JP7327849B1 - Medical table that transmits X-rays well and reduces scattering - Google Patents

Abstract

Kind Code: A1 Conventionally, many tables of a patient or the like of a medical X-ray fluoroscope are made of carbon fiber, and do not absorb incident primary X-rays, but scatter them. X-rays scattered by the patient's body are similarly scattered by the table. This increases the radiation dose rate in spaces such as examination rooms, blurs the image quality of X-ray receivers, and exposes medical personnel and patients to radiation. A medical table supports the weight of a patient or the like, and primary X-rays pass through a net 42 of a stage 10 of a top board and reach an irradiation field without interaction. By changing the material of the surface according to the type or energy of the irradiated X-rays, the generation of scattered X-rays on the bottom plate 21 is reduced, and the top plate 11 attenuates and absorbs the scattered X-rays from human tissue. . In addition, the mesh transmission plate unit 15 on the stage 10 of the top plate, the slide table 32 and the aperture plate 62 on the stage 30 of the middle plate, and the opening/closing plate 51 on the stage 20 of the bottom plate provide the minimum necessary aperture from the position of the irradiation field and the medical purpose. Adjust to size. [Selection drawing] Fig. 13

Description

INDUSTRIAL APPLICABILITY In the medical field using X-ray (hereinafter referred to as "X-ray") fluoroscopy equipment, the present invention provides a medical device capable of making the image quality of an X-ray receiver clear and reducing the exposure dose and radiation protection load. Provide a fluoroscope table (bed).

The use of radiation in the medical field is becoming widespread, and as of 2017, the total number of radiological examination/diagnostic devices and continuous angiography devices in Japan has already exceeded 17,000.
Today, specialists (hereinafter referred to as "surgeons") in each clinical department who perform a large number of surgeries as clinical treatments use X-ray fluoroscopes. Medical practice using radiation is steadily increasing, and procedures involving exposure of patients and medical personnel are also frequently performed. In recent years, technologies such as pulse fluoroscopy and selective angiography have made further progress, but as opportunities for use increase, the exposure time from X-ray irradiation tends to become longer. resulting in increased exposure. In some cases, radiation protection measures have also fallen behind, increasing the risk of radiation injury to health care workers and patients.

For radiation protection of medical personnel and patients, Non-Patent Document 1 describes lead aprons, ceiling-mounted shields (movable ceiling-mounted screens, other suspended lead flaps, etc.), mounted shields, thyroid protectors, eye shields, etc. Radiation protective equipment has been proposed, such as protective equipment for However, these radiation protectors are intended to protect X-rays that are planarly scattered in a specific direction, that is, X-rays from an intended azimuth. X-rays from the incident X-ray source (hereinafter referred to as "primary X-rays") are scattered by the table and the patient's body tissue, and the scattered X-rays are irradiated from all directions, so that medical personnel are sufficiently exposed. cannot be protected. The exposure reduction effect of these radiation protective equipment is limited in a specific direction. In other words, these radiation protective equipment are intended to reduce the radiation exposure of medical personnel to some extent, and are not a fundamental solution to the reduction of radiation exposure due to scattered X-rays.

In general, medical X-ray fluoroscopes are often used with an X-ray tube voltage of 50 to 150 kilovolts (kV), and the corresponding X-ray energy is 50 to 150 kiloelectronvolts (KeV). is the area of At 50 KeV or higher, aluminum (Al) is not in the region where the main interaction is the photoelectric effect (hereinafter referred to as the “photoelectric region”), but in the region where the Compton scattering is the main interaction (hereinafter referred to as the “scattering region”). It is in. In other words, Al scatters X-rays without much absorption. Polymer compounds such as plastics composed of elements with an atomic number smaller than that of Al, that is, elements such as carbon (C)-hydrogen (H)-oxygen (O) are also in the scattering region and absorb most of the X-rays. do not. Therefore, when primary X-rays are irradiated and interact with these light element substances, most of them are scattered without being absorbed and become scattered X-rays. These background technologies are described in detail in Patent Document 4.

An X-ray fluoroscope has an X-ray tube installed either above or below the bed on which the patient lies (hereinafter referred to as "table"), and an X-ray receiver installed in the opposite direction receives the X-rays that have passed through the patient. . Conventionally, in order to avoid absorption of X-rays, carbon fiber reinforced plastic (hereafter referred to as "CFRP"), glass fiber reinforced plastic (hereafter referred to as "GFRP"), phenolic resin, melamine resin, etc. have been used for table materials. It's here. Al and the like have been used as metals. All conventional tables are made of a light element material that absorbs less primary X-rays. These absorb little primary X-rays, but generate scattered X-rays by scattering.

On the other hand, the primary X-rays are also scattered by the patient's human tissue, which is mainly composed of light elements such as C--H--O. It has been known. Scattered X-rays generated in the patient's body are scattered forward, sideways, and backward. In the under-tube type, in which the X-ray source is below the table, the rearwardly scattered X-rays generated by the patient's body are irradiated onto the table surface below the patient's body. In the case of the under-tube type, the number of scattered X-rays in the rear downward direction (in the direction of the floor surface) is the largest, and it is said that this number is about half of the scattered X-rays generated. The table produces rescattered scattered X-rays because the conventional table material described in the previous section scatters them further without absorbing them.

Recently, in order to reduce scattered X-rays backscattered from the patient's body in the incident direction of the primary X-rays, there is an example of laying a commercially available lead-containing (Pb) sheet or the like on the table as a shielding material. A certain amount of scattered X-rays are attenuated and absorbed by this Pb sheet. However, it is difficult to say that Pb alone has excellent ability to absorb scattered X-rays in a medium energy range of 50 KeV. Moreover, the Pb sheet is not laid near the irradiation field so as not to block the irradiation field of the primary X-ray, but is laid only on a limited part of the patient's body, so its effect is limited. In other words, it is not effective against scattered X-rays from the human body tissue or the table, which are the irradiation fields that scatter the most with the sheet. Furthermore, the blanket placed on the table cannot absorb the scattered X-rays generated on the table downward (in the direction of the floor surface). Therefore, this method is not a sufficient measure for radiation protection of medical workers.

An example of installing a partial shielding material as an accessory to the table has also been devised. The X-ray protective plate of Patent Document 1 is attached to the deck (top plate) of a table placed near a patient when performing treatment or examination under X-ray fluoroscopy, and prevents medical instruments from falling off the peripheral edge of the bottom. It is characterized in that it has a side wall portion for preventing this and an L-shaped metal fitting screwed to the outer peripheral side of the side wall portion. Although the material is not specified in Patent Document 1, it states that a heavy metal element such as metallic lead is desirable because it has a high shielding effect.
Although WO 2005/010030 is not specific about the placement site, it provides partial shielding to the patient. At least it does not participate in the transmission of primary X-rays. In addition, it is not intended to be installed near the irradiation field and to adjust the position and aperture size according to the purpose of surgery (position of the affected part) in order to minimize the irradiation field. In addition, it does not refer to the absorption of scattered X-rays or the sharpening of the image quality of the X-ray receiver.
Patent document 1 is to install a supplementary additional shield attached to the table to a limited part of the patient's body, avoiding the irradiation field like the bedsheet, and to install the overall structure of the table. Not targeted. Further, in Patent Document 1, the irradiation field, which is important for reducing scattered X-rays, is restricted to the minimum required area by the table, and the scattered X-rays generated from the patient's body are not absorbed.

The X-ray protective equipment of Patent Document 2 has an additional shielding material attached to the arm portion of the patient's body to the table. The material of the side plates, which share the shielding function, is acrylic containing heavy metals such as lead, gold, and copper.
However, since the arm portion has a small body surface area and is far from the irradiation field, it is difficult to reduce the scattered X-rays generated from the patient's body only by the arm portion. Likewise, it provides partial additional shielding to the patient and is not intended to adjust its position or aperture size near the field. At least it does not participate in the transmission of primary X-rays. Furthermore, there is no mention of sharpening the image quality of the X-ray receiver.
Japanese Patent Laid-Open No. 2002-200003 is intended to install a supplementary additional shield attached to the table for arms and the like, and does not cover the entire structure of the table. Further, as in the previous section, in Patent Document 2, the irradiation field is limited to the minimum required area by the table, and scattered X-rays generated from the patient's body are not absorbed.

On the other hand, in order to make the image quality of the X-ray receiver clear, the patient's body is irradiated with the primary X-rays from the X-ray source without being spoiled by scattering or absorption, and the scattered X-rays from the table and the patient's body are received by the X-ray receiver. It is better not to let it enter the machine. It is also important to remove the generated scattered X-rays by absorption.
At present, measures are taken to reduce the amount of incident scattered X-rays by installing a straight grid, a parallel grid, a focusing grid, a cross grid, or the like, made up of Al thin plates, etc., in front of the X-ray image receiving surface of the X-ray receiver. It is This is positioned like a front filter of an X-ray receiver.
In conventional tables, materials such as CFRP and Al are used to reduce the absorption of primary X-rays so as not to reduce the amount of transmission. I can't see the table. In addition, there is no table aimed at reducing scattered X-rays reaching the X-ray receiver from the patient's body.
Additionally, a virtual grid in the image processing software prevents image quality from being smeared by scattered x-rays from the x-ray receiver. However, this is one of image processing techniques and does not mean that scattered X-rays are reduced.
Therefore, with the conventional table, there is a limit to reducing the air dose rate due to scattered X-rays in the examination room or the like and improving the image quality of the X-ray receiver.

One of the ideas for improving the image quality of the X-ray receiver is to limit the area of the irradiation field to the minimum necessary narrow range, thereby suppressing the generation of scattered X-rays by the patient's body. Are known. The X-ray movable diaphragm of the X-ray source plays a part of this role, but since the irradiation field is adjusted at a place slightly away from the table, it is difficult to limit the area to the minimum required for medical purposes. . In addition, scattered radiation such as small-angle scattering of primary X-rays occurs between the X-ray source and the table, causing the X-ray beam to spread slightly and irradiating parts other than the irradiation field with high X-ray energy. put away. At present, there is no table that has the function of adjusting the position of the irradiation field or the size (area) of the aperture.
On the other hand, attempts to adjust the aperture size (area) of the irradiation field by table accessories are also within the scope of existing knowledge. This is an over-tube type X-ray transmission device. A two-way goniometer for tabletop X and Y axes is installed on the patient's body, and a diaphragm plate such as Pb or tungsten (W) is operated in two directions. It is what makes This irradiation field is narrowed down from a large area set at the beginning to a minimum necessary small area in the middle of the procedure.

In Patent Document 3, the idea of adjusting the size of the irradiation field in the two directions of the X-axis and the Y-axis is developed, and by rotating a size adjustment device that creates a circular shadow, the irradiation field is adjusted by a disk-shaped substance with a high attenuation coefficient. It is devised to change the area of . The material of the high attenuation coefficient shield is, for example, a lead disc, mounted in the center of the shield plate, which is a rotating disc made of graphite.
However, this is a variant of a variable diaphragm that operates in two directions, and although the size of the field can be changed, the transmitted primary X-rays are reduced by shading. In addition, although the size of the irradiation field can be changed by shading, it is impossible to adjust the position and the size of the opening according to the purpose of the operation (the position of the affected part). Therefore, the position of the irradiation field is uniform for the location of the shadow, and the range of changing the dimensions of the irradiation field is limited. Furthermore, the attenuation and absorption of scattered X-rays generated by the table and the patient's body are not considered.
Japanese Patent Application Laid-Open No. 2002-200000 describes a variable diaphragm that limits the irradiation field by shadowing of a rotating disk, and does not cover the entire structure of the table. In addition, although the area of the same irradiation field can be changed, the position of the irradiation field cannot be changed according to the purpose of surgery. Furthermore, when the area of the irradiation field is reduced, the transmitted primary X-rays are reduced. Patent document 3 does not consider transmitting primary X-rays from an X-ray source without interaction or absorbing scattered X-rays generated from a patient's body.

As mentioned above, most of the tables currently devised have table materials in the area where the primary X-rays pass through (irradiation field), and there is a notch corresponding to the area of the irradiation field. A table is missing.
Similarly, the X-ray protective plate and X-ray protective equipment are partial additional shielding bodies attached to the table, but the table itself shields the primary X-rays and their scattered rays in the irradiation field (ray attenuation, which will be described later). I can't find a table that aims to do that.
Furthermore, in the same way, a variable diaphragm with a rotating disk can be attached to the table and the area of the irradiation field can be partially adjusted within a certain range by shading. can't. There is no table that aims to provide a notch corresponding to the size of the opening in the table itself, or to adjust the position of the notch and the size of the opening during surgery.
Moreover, since the table irradiated with the primary X-rays is composed of a light element, most of the X-rays are scattered without being absorbed. I can't find the table.
In addition to shielding the above-mentioned primary X-rays and their scattered rays (same as above), the table itself aims to attenuate and absorb scattered X-rays generated from the patient's body placed on the table (linear energy absorption, which will be described later). I can't see the table.
Therefore, the necessary and sufficient position of the irradiation field and the size of the opening are adjusted, the cutout allows the primary X-rays to pass through without interaction, and the scattered X-rays generated are attenuated and absorbed while the scattered X-rays are generated as little as possible. I can't find a table that aims to do that.
Therefore, with the conventional table, it is difficult to reduce the radiation protection load on medical workers by reducing the air dose rate due to scattered X-rays in the examination room or the like.

In Patent Document 4 by the same inventor, a composite absorbing material is devised that absorbs scattered X-rays from a scatterer (a patient's body or a table) while attenuating them well. The composite absorbing material is mainly composed of a lead (Pb) low reflection attenuation layer (initial layer) and multiple absorbing layers (diffusive absorber, electron absorber). By arranging 1 to 3 pairs of diffusive absorbers and electronic absorbers so as to overlap each other without gaps, incident scattered X-rays are maximally efficiently linearly attenuated and linear energy is absorbed. X-rays are extinguished by converting their energy into kinetic energy of photoelectrons and the like. As a result, it is possible to reduce the radiation dose rate in the space such as the examination room, and to reduce the radiation exposure of patients and medical staff to the necessary and minimum level. That is, the composite absorbing material has the role of absorbing scattered X-rays from the scatterer by attenuating and absorbing the scattered X-rays from the scatterer by means of a material in which three or more layers having different roles are adhered to each other and stacked in multiple layers. Composite absorbent material is one of the primary materials that make up the structure of the present invention. Linear attenuation and linear energy absorption are described in Table 1 of the Examples below and its text description. Details of the composite absorbent material will be described in Example 5 below.

International Commission on Radiological Protection, "Radiation Protection in Fluoroscopically Guided Procedures Performed Outside Imaging Departments," ICRP Pub. 117, Translated by Japan Radioisotope Association, March 31, 2017 Hubbell,J.H. and Seltzer,S.M.,”Tables of X-Ray Mass Attenuation Coefficients and Mass Energy-Absorption Coefficients 1 keV to 20 MeV for Elements Z=1 to 92 and 48 Additional Substances of Dosimetric Interest”, NSTIR 5632, (1995) (hereinafter referred to as "NIST database")

Japanese Patent Application Laid-Open No. 2004-301563 Japanese Patent Application Laid-Open No. 2002-253547 Japanese Patent Application Laid-Open No. 2004-4049849 Japanese Patent Application No. 2022-161788 (domestic priority application, earlier application is Japanese Patent Application No. 2022-1336) JP-A-4-2876

The table of a conventional medical X-ray transmission apparatus is mainly composed of a top plate and its support base. The rays are transmitted to the X-ray receiver after interacting with the material composed of these light elements. However, the primary X-rays scattered by the table become scattered X-rays although absorption by light elements is small. Also, the patient's body on which it rests produces a considerable amount of scattered X-rays, which the conventional table does not absorb and scatters further in various directions. Therefore, the air dose rate due to scattered X-rays in the examination room or the like increases. The spatially scattered X-rays generated in this way are irradiated from all directions, blurring the image quality of the X-ray receiver and exposing the medical staff and the patient to radiation. In order to reduce the amount of scattered X-rays in space, the generation of scattered X-rays associated with the table must be reduced.

The basic role of the table of a medical X-ray fluoroscope is to support the weight of the patient's body during examination and treatment. In order to solve the above problem, the present invention devised a table that satisfies the following four additional requirements.
Requirement 1 is to transmit the primary X-rays irradiated to the irradiation field without interacting with substances as much as possible (abbreviated as "transmission of primary X-rays").
Requirement 2 is that the table itself does not generate scattered X-rays as much as possible ("Suppression of generation of scattered X-rays").
Requirement 3 is to attenuate and absorb scattered X-rays generated in the patient's body to be mounted ("attenuation and absorption of scattered X-rays").
Requirement 4 is that the irradiation field can be positioned appropriately using a simple position/dimension adjustment mechanism, and can be adjusted to the minimum aperture size (area) necessary for medical purposes ("Adjustment of irradiation field position and dimensions"). ).
Requirement 4 assumes that the dimension of the irradiation field can be changed on the table side as needed during the operation, regardless of the adjustment by the X-ray movable diaphragm of the X-ray source. It should be noted that medical staff other than the operator can also operate during the procedure.
Means for solving the problem include changing the material used for the table according to the characteristics of the X-rays applied to each site. The present invention thus relates to a table that satisfies some or all of the above four requirements in combination.

Here, an undertube type table will be explained as an example.
The structure of the table, which allows transmission of primary X-rays without interaction and attenuates and absorbs scattered X-rays, consists of three steps: a top plate, an intermediate plate, and a bottom plate. First, the structure and configuration of each stage of the table and the names of individual members will be explained. The axis line is a line passing through the centroid in the longitudinal direction of the member, and in the case of the table of the present invention, refers to a line passing through the centroid in the height direction of the lying patient.
The stage of the top plate is composed of the top plate, the absorption plate, the mesh transmission plate unit, the support rails and the reinforcement beams. The tabletop supports the weight of the patient's body on which the patient lies. There is an axially long opening in the center of the top plate, and the absorption plate and the mesh transmission plate unit are fitted on the support rails in the opening. The absorber plate is a solid diced flat plate. The mesh transmission plate unit is a hollow rectangular flat plate with a net-like central portion. The load supported by the top plate is supported by the support rails and reinforcing beams, and finally supported by the table support base.
The intermediate stage is composed of a slide table and its side rollers, a slide absorption plate, a diaphragm plate and its drive mechanism. The slide table is a flat plate elongated in the axial direction, has an opening at a part of the center of the axis, and has a slide absorption plate fixed thereon at another part. The aperture plate is a solid square-cut flat plate, and the drive mechanism such as a ball screw is mounted inside the slide table. A pair of (two) aperture plates can be slidably moved in the axial direction on the opening of the slide table to freely adjust the size of the opening. The slide table installed on the side rollers can be slid and moved in the axial direction to adjust the position of the opening. The position and size of the aperture in the axial direction of the irradiation field can be adjusted by the slide table and aperture plate. A mechanical driving mechanism may be installed for the slide table and the aperture plate.
The stage of the bottom plate is composed of a bottom plate, a low reflection/scattering opening/closing plate (hereinafter referred to as "opening/closing plate"), and its fixing/driving mechanism. The opening/closing plate is a solid square cut flat plate, and can be opened and closed by a hinge mechanism or a slide mechanism. During the operation, the opening/closing plate at the position of the radiation field is opened. In the case of the undertube type, the surface of the opening/closing plate exposed to primary X-rays and its scattered radiation is coated with low-reflection materials such as Pb, W, barium (Ba), tin (Sn), molybdenum (Mo), and niobium (Nb). Coat the element. A mechanical driving mechanism may be installed in the opening/closing plate.
In the following, measures for each requirement will be explained separately for each stage.

The best way to solve Requirement 1 (transmission of primary X-rays) is to have no objects between the X-ray source and the patient's body at the site of the exposure field. That is, it is preferable that the irradiation field portion of the table be an artificial opening (hereinafter referred to as a "notch") through which the primary X-rays pass through the free space as it is. In addition, support rails, side rollers, their driving devices, and the like are not arranged in areas that may become an irradiation field centered on the axis. These are arranged to avoid the axis line center. That is, the irradiation fields of the top plate, the intermediate plate and the bottom plate are configured to be notches through which the primary X-rays pass as they are.
As for the top plate, if the irradiation field area is small, the notch may be left as an opening, but if the area is large, leaving the notch as it is impairs the function of the top plate to support the patient's body weight. At a site that may become an irradiation field, a mesh transmission plate unit is installed by removing part or all of the absorption plate at the center of the axis line of the top plate of the table. The hollow central portion of the mesh transmission plate unit is a structure or a net (mesh) in which wire materials having high tensile strength and hardly absorbing primary X-rays are woven into a mesh. The material of the wire or mesh is relatively difficult to absorb high-energy X-rays, such as CFRP, GFRP, Al wire or Mg wire. If wire rods or netting do not provide sufficient structural strength, install a rectangular frame of the same material. Moreover, you may use the integrally molded product which integrated these. Prepare an adjuster to adjust the height with the notch. As a result, the stage of the top plate can support the weight of the patient's body placed thereon and allow most of the primary X-rays to pass therethrough.
In the intermediate stage, the aperture plate attached to the slide table is cut open so as to have a dimension in the axial direction of the irradiation field, so that the primary X-rays pass through as it is.
As for the steps of the bottom plate, the low-reflection-scattering opening/closing plate in the portion of the irradiation field is opened so that the primary X-rays pass through as they are.
Details of measures for Requirement 1 will be described in Example 1.

The measure to solve requirement 2 (suppression of scattered X-ray generation) is to use a low-reflection and low-scattering X-ray material instead of CFRP or Al-based metal for the surface layer of the table in the area to be irradiated. It is the presence of reflective elements. Since primary X-rays and their scattered rays are in a relatively high energy region, the material coated with a low-reflection element (hereinafter referred to as "low-reflection material") is made of Pb.W or Ba.Sn.Mo.Nb. A simple substance or compound of is good.
In the case of the undertube type, the low reflection/scattering opening/closing plate (opening/closing plate) of the step of the bottom plate can be opened/closed by a hinge mechanism or a slide mechanism. The material of the surface layer of the opening/closing plate at the portion irradiated with primary X-rays and its scattered rays is a low-reflection material. Better is the composite absorbent material of Example 5. This portion may be covered with a material that attenuates and absorbs scattered X-rays in addition to the outside of the switch plate.
In the case of the over-tube type, the top plate of the table is made of a low-reflection material for the surface layer of the material used for the portion to be irradiated with primary X-rays of relatively high energy. Better is the composite absorbent material of Example 5.
An object that obstructs transmission is not placed in a portion where primary X-rays in the intermediate stage may be transmitted.
Details of measures for requirement 2 will be described in a second embodiment.

Countermeasures for solving Requirement 3 (attenuation and absorption of scattered X-rays) are mainly dealt with in the stage of the top board, and secondarily in the intermediate stages. There is not much correspondence in the step of the bottom plate. The application of materials that attenuate and absorb X-rays does not apply to the irradiation field of Requirement 1.
In the stage of the top plate, the material of the surface layer of the top plate, the absorption plate, and the spacer of the mesh transmission plate unit on the patient side is a composite absorption material that well attenuates and absorbs scattered X-rays. As a workaround, low reflectance materials may be used.
In the intermediate stage, the patient-side surface of the slide absorber plate and the upper and lower planar surfaces of the aperture plate are made of a low-reflection material or a composite absorber material (hereinafter referred to as "absorber").
Details of measures for Requirement 3 will be described in Example 3.

Measures to solve Requirement 4 (position and size adjustment of the irradiation field) are mainly dealt with in the middle stage during surgery, and secondarily with the bottom plate stage. The top plate is mainly used before surgery. Although it is possible to adjust the stage of the top plate during surgery, it should not be done unless there is a strong need.
In the intermediate stage, the position and dimensions of the irradiation field are adjusted using a slide table and diaphragm plate. The approximate position of the irradiation field in the axial direction is adjusted using a slide table (abbreviated as “position adjustment of the irradiation field”). Then, the notch is adjusted by a pair of diaphragm plates to adjust the aperture size (abbreviated as “adjustment of irradiation field size”). The aperture plate can be driven by a ball screw to freely adjust the size of the aperture in the axial direction, thereby changing the size of the irradiation field in the axial direction.
In the bottom plate stage, the position of the irradiation field can be adjusted by opening and closing the low reflection/scattering opening/closing plate with a hinge mechanism or a slide mechanism. In the case of a hinge mechanism, the vertical width of the field axis can also be adjusted.
At the stage of the top plate, the adjustable width of the irradiation field in the axial direction can be set by the number of installed mesh transmission plate units at the beginning of surgery. Similarly, by selecting the width of the spacer that covers the hollow central portion of the mesh transmission plate unit, the width of the irradiation field in the direction perpendicular to the axis can be changed.
Details of measures for requirement 4 will be described in a fourth embodiment.

The descriptions of requirements 1 to 4 above are summarized below.
The medical table supports the weight of the patient, etc., ensures the transmission of primary X-rays to the irradiation field (Requirement 1), generates as little scattered radiation as possible (Requirement 2), and prevents scattered X-rays from scatterers. is attenuated and absorbed (requirement 3), and the position of the irradiation field and aperture size (area) can be adjusted (requirement 4). Even some of these requirements are effective for the invention, but it is better to satisfy all of them.
The present invention is a medical table comprising a part or all of three steps, a top plate, a middle plate and a bottom plate, the surfaces of which are made of a low-reflection material or a composite absorption material.
That is, the primary X-rays that have passed through the hollow free space (hereinafter referred to as "notch") between the bottom plate and the intermediate step pass through the mesh surface of the top plate step made of a material that hardly absorbs X-rays. Therefore, interaction with matter hardly occurs, so there is no linear attenuation due to reflection or scattering. The low-reflection material mainly reduces the generation of scattered X-rays due to primary X-rays and their scattered rays, except for the irradiation field of the steps of the bottom plate. Mainly in the steps and intermediate steps of the top plate other than the mesh portion, the composite absorbing material attenuates and absorbs the scattered X-rays from the patient's body. The position of the irradiation field is adjusted mainly in the middle and bottom plate stages, and by adjusting the minimum opening size (area) necessary for medical purposes, scattered X-rays generated near the irradiation field are reduced.
As a member of the mechanism that adjusts the position of the irradiation field and the size of the aperture, which are changed for each surgical purpose, there is a mesh transmission plate unit fitted in the top step, a hinged opening and closing plate in the bottom plate step, and an intermediate plate. The stage includes a diaphragm plate on a slide table and the like. The surface of the member is coated with a low reflection material or composite absorption material, but the entire member may be made of these materials.

The table of the present invention allows the primary X-rays to pass through the irradiation field without interacting with the substance, restricts the irradiation field to the minimum necessary aperture size (area), suppresses the generation of further scattered X-rays, and By attenuating/absorbing and reducing the scattered X-rays generated by the patient's body, the image quality of the X-ray receiver can be improved and the radiation dose rate in the space such as the examination room can be reduced. As a result, the exposure dose of medical staff and the load related to radiation protection can be reduced. Therefore, it can make a great contribution to the utilization of the technology in the industrial field.

It is an explanatory view of the structure of the steps of the top plate of the table of the present invention. FIG. 4 is an explanatory diagram of the structure of the absorbing plate on the stage of the top plate; a is an overall view, and b is a partially enlarged cross-sectional view. FIG. 4 is an explanatory diagram of the structure of the mesh transmission plate unit on the stage of the top plate; In the figure, a is a wire rod, b is a net (mesh), and c is an integrally molded product. FIG. 10 is an explanatory diagram of a method of adjusting the irradiation field dimension in the direction perpendicular to the axis line by the spacer of the mesh transmission plate unit on the stage of the top plate; In the figure, a is wide and b is narrow. FIG. 4 is an explanatory view of the tiers of the bottom plate of the table of the present invention; FIG. 4 is an explanatory diagram of the structure of the low-reflection-scattering switching plate of the step of the bottom plate; a is an overall view, b is an enlarged partial cross-sectional view (when only the outside is covered), and c is an enlarged partial cross-sectional view (when both the inner and outer surfaces are covered). It is an explanatory view of the middle stage of the table of the present invention. FIG. 4 is an explanatory diagram of the structure of a diaphragm plate in an intermediate stage; a is an overall view, and b is a partially enlarged cross-sectional view. FIG. 4 is an explanatory diagram of the structure of the slide table in the intermediate stage; FIG. 10 is an explanatory diagram of a method of adjusting the aperture size of the irradiation field by the intermediate stage slide table and diaphragm plate; FIG. 10 is an explanatory diagram of a method of adjusting the aperture size of the irradiation field by the low-reflection-scattering opening and closing plate on the stage of the bottom plate; A is a diagram for an opening angle of 90, b is for an opening angle of 60°, and c is for an opening angle of 45°. FIG. 2 is an illustration of a basic case of composite absorbent material; It is a bird's-eye view of the whole table of the present invention. a is a diagram of a top plate step, b is a diagram of an intermediate step, and c is a diagram of a bottom plate step. FIG. 10 is an explanatory diagram of the structure of the sheet transmission plate unit in the case of thin sheet sheets on the steps of the top plate; d is a belt-like film of a thin sheet, e is an elastic flat plate of a thin sheet, and f is an integrally molded product.

An embodiment of the present invention will be described based on the drawings.
The basic role of the table of a medical X-ray fluoroscope is to support the weight of the patient's body during examination and treatment. This function is mainly performed by the top plate and its supporting structure. In addition to this basic role, the above-mentioned four additional requirements are required in order to make a table that reduces the air dose rate in a clinic or the like. That is, Requirement 1 is "transmission of primary X-rays", Requirement 2 is "suppression of scattered X-rays", Requirement 3 is "attenuation and absorption of scattered X-rays", and Requirement 4 is "position and size adjustment of irradiation field". is. Here, a mode for carrying out the invention, which is a method for solving these requirements, will be described. Further, in the rest of this specification, the table will be described on the assumption that it has a three-tiered structure consisting of a top plate step, an intermediate step, and a bottom plate step.
It should be noted that the table and its components shown here are merely examples and are not intended to limit the invention.

In the remainder of the specification, the following terms will be used unless otherwise indicated.
The primary source of radiation is the X-ray tube, and this primary X-ray beam is called "primary X-rays". When the tube voltage of the X-ray tube is 100 kV, the generated primary X-rays have continuous energy and the maximum energy is approximately 100 KeV. Although it depends on the state of the X-ray generator, the average value of the energy (hereinafter referred to as "effective energy") is often about 60 to 70% of the maximum energy, so here it is assumed to be constant at 65%. Assume. In the remainder of this specification, effective energy shall be indicated unless otherwise specified.
Radiation scattered by primary X-rays hitting a patient/examinee, part of an apparatus, etc. is collectively called "scattered X-rays." On the other hand, the primary X-rays are not scattered or absorbed much, and the energy of the primary X-rays is mostly maintained and transmitted at the incident angle. ) is called a “direct ray”.
In addition, the radiography room for medical examination, the examination room, the treatment room, the X-ray examination room, etc. will be collectively referred to as the "examination room, etc.". In the rest of this specification, an undertube type X-ray fluoroscopy apparatus in which the X-ray tube is placed under the table will be described as an example, unless otherwise specified.

In the remainder of this specification, the following terms for materials are used.
A low-reflection material is a material coated with a low-reflection element such as Pb.W or Ba.Sn.Mo.Nb. A low-reflection element is an element with an atomic number of 20 or more, which is in the region (photoelectric region) where the photoelectric effect is dominant even in the energy region of 80 KeV or more, and has a linear attenuation coefficient μ of 10 (1/cm ) above. Low reflectance materials are described in more detail in Example 6.
A composite absorption material is a multi-layer structure in which the first layer of Pb serves as a low reflection attenuation layer, and the second and subsequent layers consist of 1 to 3 pairs of diffusion absorbers such as Sn and Mo and electron absorbers such as Nb and Cu. It is a material that serves as an absorption layer and attenuates and absorbs scattered X-rays inside by stacking three or more layers with different roles in close contact. The Pb of the first layer is the same as the low reflection material. At monochromatic energies such as 50 or 20 KeV, diffuse absorbers are elements with an electron absorption fraction (μ en /μ) of less than 70%. Further, the electron absorber is an element with μen/μ of 70% or more and μen of 10 (1/cm) or more.
The composite absorbent material is described in more detail in Example 5, and further details are given in co-owned US Pat.
In addition, the low reflection material and the composite absorption material are collectively referred to as "absorber". Among metal materials, high specific strength Al alloys such as Al--Mg (5000 series alloys) and Al--Mg--Si (6000 series alloys) are called Al series. High specific strength Ti alloys such as Ti-6Al-4V are called Ti series.
In addition, in the rest of this specification, unless otherwise specified, the part described as an element means a material containing that element, and unless otherwise specified, a material means a material of a single metal element.

Describe candidate materials for use in the table. Here, the elements appearing in the rest of this specification are listed, and each element used for each member is described in the examples below for the contents of each element or compound material.
First, referring to the NIST database of Non-Patent Document 2, elements that interact with primary X-rays and hardly absorb X-rays were extracted.
Table 1 shows H, C, O, Mg, Al, and Si as non-absorbing elements (light elements) and Ti, Fe, copper (Cu), Nb, Mo, Sn, The results of investigating the linear attenuation coefficients (μ) and linear energy absorption coefficients (μen) of Ba, W, and Pb are shown. In Table 1, numerical values less than 1 are indicated by indices.
In the X-ray transmission phenomenon of matter, the linear attenuation coefficient μ (1/cm) is defined by I/I ₀ =Exp (−μt). Here, I is the intensity on the exit side, _I0 is the intensity on the incident side (for example, the number of photons or dose rate), and t is the thickness of the substance. A substance with a large linear attenuation coefficient (μ) has a large attenuation, that is, a large shielding ability due to scattering, absorption, or the like. The linear energy absorption coefficient (μ en ) indicates only the amount of energy remaining after being absorbed by electrons without being re-emitted as separate photons such as bremsstrahlung X-rays, that is, only the amount of electron absorption. Table 1 shows the proportion of linear energy absorption in linear attenuation, that is, the proportion absorbed by electrons without generating another photon (characteristic X-ray, Auger electron, bremsstrahlung X-ray) due to X-ray interaction. The electron absorption ratio (μen/μ) is also added.

In Table 1, the non-absorbing elements (light elements) H, C, and O have small μ and μ en in the entire energy range of 10 to 150 KeV. At 50 KeV or more, Mg, Al, and Si are considerably small, but at less than 50 KeV, μ and μen are somewhat large, resulting in a large electron absorption ratio. On the other hand, with absorption elements (Fe, Cu, Nb, Mo, Sn, Ba, W, Pb) other than Ti, μ and μ en are considerably large at less than 80 KeV, increasing the electron absorption ratio. The absorbing elements Nb, Mo, Sn, Ba, W, and Pb have a large μ even at 80 KeV or higher, and W and Pb in particular have a large μ even at 100 KeV or higher. μen becomes a small number in an energy band slightly higher than the K absorption edge (Kab) of each element, where the electron absorption ratio (μen/μ) is also small. Ti, which is an absorbing element, has relatively small values of μ and μen above 50 KeV.

Table 1

(Solution for Requirement 1 “Transmission of primary X-rays”)
In Example 1, a specific example of a method for solving Requirement 1 (transmission of primary X-rays) is shown. For good penetration of the primary x-rays, it is best to have no objects between the x-ray source and the patient's body at the site of the exposure field.
In the stage 10 of the top plate, a hollow portion is provided at the center of the axis line of the top plate 11 in which the absorption plate 14 or the mesh transmission plate unit 15 is fitted. At a site that may become an irradiation field, a mesh transmission plate unit 15 is installed by removing part or all of the absorption plate 14 at the center of the axis line of the top plate of the table. The portion of the mesh transmission plate unit 15 is a candidate position of an irradiation field through which primary X-rays are well transmitted. Also, the support structures such as the support rails 12 and the reinforcing beams 13 located below the top plate 11 are installed so as to avoid the radiation field. FIG. 1 shows the fitting structure of the top plate 11, the absorption plate 14, the mesh transmission plate unit 15, and the top plate portion to which these are attached.
In FIG. 1, a plan view of the top plate 11 is shown on the upper side, and a vertical cross-sectional view at the centerline position of the entire table in the axial direction is shown on the arrow AA. The stage 10 of the top plate is composed of a top plate 11 , an absorption plate 14 , a mesh transmission plate unit 15 , support rails 12 and reinforcing beams 13 .
Although the position and dimensions of the irradiation field differ depending on each surgery and patient's body shape, a mesh transmission plate unit 15 is installed instead of the absorption plate 14 at the candidate position of the irradiation field required for that surgery. Since it is not easy to replace the mesh transmission plate unit 15 during surgery, the mesh transmission plate unit 15 is installed in advance at positions (candidate positions) in the irradiation field that may be used.

The construction of the stage 10 of the top plate of FIG. 1 will now be described in more detail.
The top plate 11 supports the weight of the patient's body on which the patient lies. In the plan view of the upper top plate 11, there is an opening long in the axial direction on the left side (the patient's head side) of the center of the axis line of the top plate, and the absorption plate 14 and the mesh transmission plate unit 15 are located there. It is installed by fitting it on the support rail 12 of the. Absorber plate 14 is a solid square plate. The mesh transmission plate unit 15 is a hollow rectangular flat plate with a net-like central portion. Since the support rails 12 and the reinforcing beams 13 are located on the back side of the top plate, they are indicated by dashed lines (hidden lines).
The support rail 12 can be seen on the rear side of the intermediate layer in the longitudinal section view AA. The reinforcing beams 13 positioned behind the support rails 12 are at the same height as the support rails, and are not visible in the drawing except for the dashed line (hidden line) at the left end. An intermediate step 30 is installed inside the pair (two) of support rails 12 . The support rails 12 and the right ends of the reinforcing beams 13 are lashed to the table support base 2 that supports the table 1 . A bottom plate 21 or the like is installed on the lower side between the support rail 12 and the reinforcing beam 13 from the center to the left end.

The structure and material of the absorbing plate 14 of the step 10 of the top plate will now be described. Absorber plate 14 is a solid square plate. The structure of the absorbing plate 14 is shown in FIG.
The absorbing plate 14 is inserted into a hollow portion arranged in the vicinity of the central axis in the axial direction of the top plate 11 and placed on the support rails 12 . The support rail 12 is an H-shaped or I-shaped member, and supports both the top plate 11 and the absorption plate 14 on the upper end surface. When the absorbing plate 14 under the top plate 11 is fitted, the difference in height from the surface of the top plate 11 is almost eliminated, and the top plate 11 is almost flush with the surface. The requirements of the top plate 11 and the absorbing plate 14 are to support the weight of the patient's body and to absorb scattered X-rays generated in the patient's body tissue. The feature is that the absorbing plate 14 can be replaced with the mesh transmission plate unit 15 . Therefore, the top plate 11 and the absorption plate 14 are composed of materials such as the surface layer of the Al-based base material being made of a composite absorption material. Details of the materials will be described later in Example 3 (attenuation and absorption of scattered X-rays). .

Next, the structure and material of the mesh transmission plate unit 15 of the stage 10 of the top plate will be described. The mesh transmission plate unit 15 is a hollow rectangular flat plate with a net-like central portion. FIG. 3 shows an explanatory diagram of the structure of the mesh transmission plate unit 15 in the stage 10 of the top plate. In FIG. 3, a shows a configuration in which the mesh surface is constructed with a wire rod 41, b shows a configuration in which the mesh surface is constructed from a mesh 42, and c shows a configuration in which the mesh surface is manufactured from an integrally molded product 45. As shown in FIG. A and b are structures in which wires are arranged in a grid pattern, and c is an integrally molded product.
The mesh surface of the mesh transmission plate unit 15, in the case of discrete parts, is arranged in a grid pattern by wire rods 41 or meshes 42 (hereinafter referred to as "net surface etc."), frames 43 and spacers 44. A structure 16 is constructed. Since the mesh transmission plate unit 15 also needs to have the function of supporting the load of the patient's body, the mesh surface in the center must also have a certain strength. The mesh surface and the like are made of a material such as CFRP, Al, or the like, which has high tensile strength and does not easily absorb primary X-rays. In addition, since the patient's body weight is transferred to the lower support rails 12 via the frame 43, the frame 43 must also have a certain strength. A rectangular frame 43 is installed in FIGS. 3a and 3b for the purposes of structural strength and height adjustment. The frame 43 is a plate member made of the same material as the mesh surface or the like.
On the other hand, the mesh transmission plate unit 15 may be an integrally molded product 45 . An integrally molded product 45 shown in FIG. 3c is obtained by integrally molding a mesh surface and a frame with CFRP or the like. Since this has sufficient strength as will be described later, it is not necessary to use the rectangular frame 43 . When using a commercial product such as a continuous fiber reinforcing material as the integrally molded product 45, the height may be different from the thickness of the notch that penetrates the center of the axis line of the top plate 11, so the height is adjusted. Separate parts may be required.
When adjusting the height of the mesh transmission plate unit 15, an adjuster 46 is used as a member. The adjuster 46 is made of the same material as the structure 16 in which wires are arranged in a grid pattern and the integrally molded product 45 described above. In the case of the integrally molded product 45, two adjusters 46 such as rectangular parallelepipeds are attached to a commercially available product. A structure in which wire rods are arranged in a grid pattern and an integrally molded product are stored in a notch penetrating through the central portion of the axis line of the top plate without surplus space. As a result, the integrally molded product 45 and the adjuster 46 can also support the weight of the patient's body.
When the mesh transmission plate unit 15 is fitted, the difference in height from the surface of the top plate 11 is almost eliminated, and the top plate 11 becomes almost flush with the surface, and a part of the weight of the patient's body can be supported. The rest of the patient's body weight is supported by the support rails 12 and the reinforcing beams 13 via the top plate 11 . The support rails 12 and the reinforcing beams 13 are connected to the table support base 2 which supports the entire table as shown in FIG.

FIG. 4 shows the adjustment of the irradiation field dimension in the direction perpendicular to the axis line by the spacer 44 of the mesh transmission plate unit 15 . FIG. 4 shows an example of manufacturing with an integrally molded product 45, and a is a mesh transmission plate unit for a wide case in which all the surfaces of the support rail 12 are dimensioned in the direction perpendicular to the axis of the irradiation field. Similarly, b is a narrow mesh transmission plate unit in which a part of the inter-surface dimension of the support rail 12 is covered with a spacer 44 to arbitrarily restrict the dimension in the vertical direction of the axis of the irradiation field.
The spacer 44 is made of the same material as the surface layer of the top plate 11 . If it is composite absorbent material 80, the thickness of spacer 44 is generally less than 1.5 mm.
In the above example, the absorption plate and mesh transmission plate unit of the top plate step are fitted in, but the absorption plate and mesh transmission plate unit are not inset type, but slide type that can be stored by sliding on the column guide. It doesn't matter if it is.

Materials such as the screen surface of the mesh transmission plate unit are required to be difficult to absorb primary X-rays and to have high strength. If the strength of the material of the mesh surface is as high as possible, the number of wires in the mesh can be reduced and the thickness of the mesh can be reduced to further increase the amount of primary X-rays that pass through the mesh. In addition, the finer the screen material, the clearer the image quality of the X-ray receiver. However, when the material is CFRP or the like, it is difficult to absorb the primary X-rays, so the shape of the mesh surface is not displayed on the X-ray receiver.
The material of the mesh surface of the mesh transmission plate unit of the present invention is preferably an element having small values of μ and μ en in a relatively high energy region of primary X-rays of 50 KeV or higher.
Looking at the non-absorbing elements (light elements) in Table 1 under the above concept, polymer compounds such as plastics composed of elements such as carbon (C)-hydrogen (H)-oxygen (O), Al, It can be seen that glasses and ceramics composed of metals such as Mg and elements such as Si absorb little X-rays in a relatively high energy range. Based on these results, CFRP, GFRP, Al-based materials, Mg alloys, etc. were extracted as candidate materials for the screen surface of the mesh transmission plate unit. However, Si-based ceramics (SiC, _{Si3C4 ,} etc.) were not used as candidate materials because of their low tensile elastic modulus.

Next, from the viewpoint of mechanical strength, materials such as nets were extracted. A material having as high a strength as possible is preferable for the mesh surface. Table 2 shows the results of examining the strength of the candidate materials for the screen surface of the mesh transmission plate unit extracted in the previous section.
In Table 2, the range of candidate materials for the screen surface of the mesh transmission plate unit, which is said to be difficult to absorb primary X-rays in the previous section, is carbon fiber reinforced plastic (CFRP) polyacrylonitrile (PAN) fiber and Pitch-based fiber, E glass of glass fiber reinforced plastic (GFRP), Al alloy (A5052), and Mg alloy (AZ31) were extracted, and their density (g/cm ³ ), tensile modulus (GPa), tensile strength (MPa )showed that. In CFRP and GFRP in Table 2, the range of minimum and maximum characteristic values reported in literature and the like is shown because the characteristic values generally disclosed vary widely. In addition, Ti alloy (6Al-4V), carbon steel (S45C), and stainless steel (SUS304) are added as strength comparative materials.

The tensile strength of the candidate material for the mesh surface that hardly absorbs primary X-rays shown in Table 2 is 200 MPa or more. For example, if the load is in the tensile direction, even if the body weight is 400 kilograms (Kg), a single wire rod with a diameter of φ5 mm (cross-sectional area of about 20 mm ² ) can withstand the load. A single wire having a diameter of φ2 mm (cross-sectional area of about 3.1 mm ² ) can withstand a load of 60 kg. For a diameter of φ5 mm, the required tensile strength of the candidate material is 50 MPa when the patient's body weight is 100 kg. That is, the specifications required to support a patient of standard weight (60 kg) are a wire rod with a diameter of φ2 mm when the tensile strength is 200 MPa, and a wire rod with a diameter of φ5 mm when the tensile strength is 50 MPa. However, the diameter of the wire should preferably be about φ5 mm in order to prevent it from digging into the patient's skin. In addition, in order to prevent congestion on the skin surface and the skin slipping through the mesh and partially falling and getting caught, the number of wires on the mesh surface should be large, and the mesh spacing should be at least 100 mm or less, more preferably 50 mm or less. good. In the tensile direction, even a wire rod with a diameter of φ2 mm and a tensile strength of 50 MPa can support a patient with a standard weight if there are four wire rods on the mesh surface due to the required mesh spacing. That is, assuming that the requirements for mechanical strength including bending strength are sufficiently satisfied, a plurality of wire rods having a diameter of φ2 mm or more, preferably about φ5 mm, are placed on the mesh surface at intervals of 100 mm or less, more preferably 50 mm or less. Deploy.
On the other hand, there are commercially available integrally molded products that can be used for mesh transmission plate units instead of mesh screens. The reinforcing carbon fiber mesh of Patent Document 5, which is a reinforcing material for concrete structures, and commercially available continuous fiber reinforcing materials include commercially available products having a mesh spacing of 50 mm or less. For example, Nefmac Type-C/G/H manufactured by Asahi Glass Matex Co., Ltd. and Tow Grid FTG-CR6 manufactured by Nippon Steel Chemical & Arterial Co., Ltd. are commercially available. These may be applied to the mesh surface of the mesh transmission plate unit. In addition, since these materials have considerably high self-supporting strength against a bending moment, they do not require a frame, and the cut material may be used as it is as an integrally molded product of a net (mesh) and a frame.

Table 2

Each of the support rails and reinforcing beams of the steps of the top plate is two long beams in the axial direction, and supports the load placed on the table or the like. The requirements for this material are that it is difficult to absorb primary X-rays, that it has high strength, and that it bends little when bent. From the value of μ in Table 1, the candidate materials in Table 2 (CFRP, GFRP, Mg alloy, Al alloy) hardly absorb primary X-rays. Among the metals used as comparative materials, Ti-based metals are also within a usable range.
In order to reduce the deflection due to bending, the cross section of the beam should be H-shaped, I-shaped, L-shaped, channel (co), hollow square tube (□), hollow round tube (○), which has a large cross-sectional moment of inertia. etc. is preferable. Among the above-mentioned candidate materials, commercially available shaped materials are preferable as the supporting rails and the reinforcing beams.

Structural materials of GFRP are specified in JIS K 7011, and pultruded materials are specified in JIS K 7015. Shapes such as I-type, L-type, U-type, □-type, and ◯-type are commercially available. Since it is manufactured by continuous pultrusion, it is possible to form even slightly complicated cross-sectional shapes.
In CFRP, JIS K 7097 standardizes unidirectional carbon fiber reinforced plastic strip materials that are reinforcing materials for concrete structures. However, many CFRP materials are not standardized by JIS. One of the reasons for this is that there is a high degree of freedom in the shape because there are also manufacturing processes such as impregnation. Therefore, JIS and the like prescribe various methods for testing mechanical properties. Based on this, CFRP is already used for aircraft wings and spacecraft structural members. Similar to GFRP, shapes such as U-type, □-type, and 〇-type are also available on the market.
The JIS standards for extruded profiles are Mg alloy (JIS H 4204) and Al alloy (JIS H 4100). ing. Although there is no JIS standard for Ti-based alloys, shapes such as L-type and U-type are commercially available.
Therefore, CFRP, GFRP, Mg alloys, Al-based materials, and the like are suitable as materials for the beams. For applications that require toughness, such as screws and fasteners, Ti-based materials, which are metals and have high strength, are also within the range of candidate materials because they may be able to reduce the thickness of plates.
Therefore, in the drawings of the present invention, an H-shaped material that can be machined with Al or Ti is used for the support rails, and a similar I-shaped material is used for the reinforcing beams. Although the drawings were examined for H-shaped and I-shaped materials, L-shaped and channel (co)-shaped materials may also be used.

The intermediate stage is composed of a slide table and its side rollers, an aperture plate and its drive mechanism. In the intermediate stage, there is a large hollow notch in the axial direction corresponding to the candidate position of the irradiation field in advance at the center of the axis of the slide table. The aperture plate attached to the slide table can adjust the opening angle so as to match the dimension of the irradiation field in the axial direction. By opening the opening angle of the aperture plate to the axial dimension of the irradiation field of the primary X-rays when starting the operation, the primary X-rays are transmitted as they are without interacting with each other. See the description of the third embodiment for details of the structure of the intermediate stage.

The stage of the bottom plate consists of a bottom plate, a low-reflection-scattering opening/closing plate, and its fixing/driving mechanism. The step of the bottom plate does not need strength to support any substance, and is like a cover for preventing primary X-rays outside the irradiation field and their scattered rays. At the start of work, all the low-reflection scattering opening/closing plates on the bottom plate stage are closed by the opening/closing fittings. When the surgery is started, the low-reflection scattering opening/closing plate in the portion of the irradiation field required at that time is opened by removing the fixed state of the closed state by the opening/closing metal fitting, so that the primary X-rays pass through as it is. Refer to the description of the second embodiment for details of the step structure of the bottom plate.

(Method for solving Requirement 2 “Suppression of generation of scattered X-rays”)
In Example 2, a specific example of a method for solving Requirement 2 (suppression of scattered X-ray generation) is shown. Scattered X-rays are generated in the table itself along with irradiation of primary X-rays in the bottom plate of the undertube type or the top plate of the overtube type.
As in the above-described Embodiment 1, the low-reflection scattering opening/closing plate (hereinafter referred to as the "opening/closing plate") at the portion of the irradiation field on the step of the bottom plate is opened by a hinge mechanism or a slide mechanism in order to transmit primary X-rays. . However, since the outer surface of the opening and closing plate close to the irradiation field is irradiated with relatively high-energy X-rays (hereinafter referred to as "small-angle scattered rays") scattered at small angles by the X-ray source, the X-rays are reflected and It is necessary to use a material with little scattering. Therefore, in the under-tube type, an opening and closing plate having a low-reflection material coated with a low-reflection element is installed on the surface layer. The opening/closing plate needs to have a certain strength in order to support the stress during opening/closing. For this reason, a high-strength Al-based, Ti-based, CFRP, or other plate material is used as the base material of the opening/closing plate. The bottom plate may be made of a material generally used for the table of a medical X-ray transmission apparatus, such as an Al plate or a CFRP plate.

According to Table 1, the low-reflection elements coated on the outer surface of the switching plate are extracted. In Table 1, Ti, Fe, Cu, Nb, Mo, Sn, Ba, W, and Pb are extracted as absorbing elements, and their linear attenuation coefficients (μ), linear energy absorption coefficients (μen), and electron absorption ratios (μen/μ )showed that. Elements with less scattering and more absorption in the relatively high energy region of 50 KeV or higher of the primary X-rays and their scattered rays have large linear energy absorption coefficients (μen) and electronic absorption ratios (μen/ μ) is large. Elements having a large μen and a large μen/μ at 50 KeV or more are Pb·W, followed by Ba·Sn·Mo·Nb. Therefore, the low reflection material is preferably Pb.W or Ba.Sn.Mo.Nb alone or as a compound. More preferably, as in the composite absorbing material of Example 5, the opening/closing plate in which the low reflection attenuation layer (first layer) is coated with Pb or the like should include Zr, Ni, Co, Fe, Cr, and V in the inner multilayer absorbing layer. , Ti, Mg, etc. are preferably used. This corresponds to the rigid composite absorbent material of US Pat. Further, the opening/closing plate itself may be made of a low-reflecting material such as W or a rigid composite absorbing material instead of being coated with the above-described low-reflecting material or composite absorbing material.

FIG. 5 shows an example of the step 20 of the bottom plate in the case of opening and closing the low reflection/scattering opening/closing plate (opening/closing plate) 22 by means of a hinge mechanism in an undertube type. As shown in FIG. 5, the step 20 of the bottom plate is composed of a bottom plate 21, an opening/closing plate 22, and an opening/closing metal fitting for opening/closing the same. FIG. 5 shows a vertical cross-sectional view at the axial centerline position of the entire table in the upper arrow view AA, and shows a cross-sectional view of the step 20 of the bottom plate in the lower arrow view CC.
A bottom plate 21 is mounted under the support rails 12 and the reinforcing beams 13 . Between the center of the bottom plate 21 and the end on the left side (on the patient's head side), there is an opening/closing plate 22 that can open the irradiation field position. FIG. 5 shows an example in which 8 sets of opening/closing plates are arranged in pairs (two pieces) on the left and right sides. The third and fourth pairs of opening and closing plates are open. The number of opening/closing plates may be more or less than eight sets. The opening/closing plate 22 is a solid square-cut flat plate, and in the case of a hinge mechanism, it can be opened/closed by opening/closing metal fittings attached to the lower side or the side surface of the support rail 12 . FIG. 5 shows an example in which a folding hinge 53 is used as an opening/closing fitting for opening/closing.
The step 20 of the bottom plate is like a cover for preventing the generation of scattered X-rays due to the irradiation of the primary X-rays and its scattered rays outside the irradiation field. You don't need the strength to do it. The surface of the part that is locally irradiated with primary X-rays and its scattered rays due to opening and closing operations is partially covered with a low-reflection material.

FIG. 6 shows a more detailed example of the low-reflection-scattering opening/closing plate (opening/closing plate) 22 which is of an undertube type and is opened/closed by a hinge mechanism. In FIG. 6, a is an overall view, b is an enlarged cross-sectional view of the B portion (only for the outside), and c is an enlarged cross-sectional view of the B portion (for the inside and outside).
FIG. 6a shows two low-reflection scattering switching plates 22, which are a pair of switching plates (left) 54 and switching plates (right) 55. FIG. One or more pairs are installed on the step 20 of the bottom plate of the table 1, but a large number of pairs may be installed as required. A folding hinge 53 is attached to the side surface of the support rail 12 and the bottom plate 21, and the opening/closing plate 22 opens and closes using this as a supporting point and a fulcrum. FIG. 6a shows an opening/closing example with an opening angle of 90° for full opening and full closing, but the left and right opening/closing plates can be stopped at an intermediate opening angle (for example, 45° or 30°). Since the pair of opening/closing plates 22 closed by the foldable hinges 53 have a structure in which a handle cover 56 at the tip of the plate is engaged at the center, there is no member for supporting or driving the opening/closing plates at the central portion of the axis.
Although FIG. 6a shows a structure that can be opened and closed manually, a mechanical driving mechanism such as a cam mechanism may be installed for opening and closing all or part of the low reflection scattering opening and closing plate.

6b and 6c schematically show the material configuration of the opening/closing plate 22. As shown in FIG. In the case of the low-reflection scattering opening/closing plate 22, in the case of an undertube type, the outer surface that receives irradiation of primary X-rays and its scattered radiation is covered with a low-reflection material 80. FIG. In addition, the surface of the part that is locally irradiated with primary X-rays and its scattered rays due to opening and closing is partially covered with a low-reflection material 80 . On the other hand, the inner surface of the opening/closing plate irradiated with the primary X-rays or its scattered radiation, or the inner surface irradiated with the scattered X-rays from the patient's body within the irradiation field, is coated with the composite absorbing material 70 . is good. Even better, both the inner and outer surfaces of the shutter plate are coated with a low-reflection material 80 or a composite absorbent material 70 . The opening/closing plate itself may be made of a low reflection material such as W or a rigid composite absorption material.
FIG. 6b shows a partial cross-sectional enlarged view (B section) when the composite absorbent material 70 is arranged only on the outer side. FIG. 6c shows a partial cross-sectional enlarged view (B section) in the case of arranging the composite absorbent material 70 both inside and outside.
Objects that interfere with transmission should not be placed in areas where primary X-rays may penetrate. Therefore, do not place the opening/closing plate and its supporting or driving mechanism in the irradiation field.

In the stage of the bottom plate, all the opening/closing plates are closed by the opening/closing metal fittings at the start of work. The opening and closing metal fittings are made by applying commercially available folding hinges that are often used for shelf cover plates, and can be operated manually or with weak force such as mechanical power, and the lid can be fixed and held in the closed state and the open state. Similarly, the opening/closing metal fittings may be commercially available hinge stays for shelves, folding L-shaped brackets, or flipper metal fittings for doors. When the opening/closing fitting is operated manually or with a weak force such as mechanical power, the lid is opened from the closed state. It can also be stopped in the middle from fully open to fully closed. When the operation is started, the opening/closing plate of the required irradiation field portion is opened so that the primary X-rays can be transmitted as it is.
The opening/closing plate may be provided with a driving mechanism for opening/closing. In that case, the position of the radiation field can be expanded beyond the range that can be adjusted with the intermediate layer during surgery.

Next, a method of opening and closing the opening and closing plate by means of a slide mechanism will be described. In this method, the opening/closing plate is a long plate that crosses the hollow part of the table in the direction perpendicular to the axis, and is a solid rectangular plate with one long side. The long plate is passed through the guide members of the plate support metal fittings installed on the lower side of a pair (two) of support rails, and the long plate is guided and supported by the suspension-type one-sided guide members at both ends of the plate support metal fittings. Thus, the opening/closing plate can be closed. As the guide material, a panel joint material (aluminum joiner) manufactured by extruding a commercially available Al alloy can be applied. Alternatively, a commercially available mini side roller may be split in half in the longitudinal direction and used. The opening/closing plate can be opened by pulling out the long plate from the guide member.

The concept of Requirement 2 (suppression of scattered X-ray generation) in the overtube type top plate will be explained. In the overtube type, in theory, a low-reflecting material should be placed on the top plate exposed to primary X-rays and their scattered radiation. In addition, as in Example 3, a composite absorbing material is placed in a site that is shielded by the patient's body and is not exposed and is irradiated with scattered X-rays. However, as mentioned above, it is considered better to coat the site exposed to primary X-rays and its scattered rays with a composite absorbing material rather than a low-reflection material. Therefore, when Example 3 is applied to the overtube-type top plate and the composite absorbent material is coated, there is no particular need to deal with Requirement 2.

(Solution for Requirement 3 “Attenuation and absorption of scattered X-rays”)
In Example 3, a specific example of a method for solving Requirement 3 (attenuation and absorption of scattered X-rays) is shown. Requirement 3 is primarily concerned with the steps of the top plate, and secondaryly with the steps in the middle. The step of the bottom plate is not involved.
A lot of scattered X-rays are generated from a patient's body that has been irradiated with primary X-rays. In the case of the undertube type, 40% or more of the generated scattered X-rays are scattered backwards, that is, toward the table. Since almost all conventional tables made of Al or CFRP scatter scattered X-rays without absorbing them, the air dose rate in the examination room or the like is high. Therefore, here, a method of attenuating and absorbing scattered X-rays by changing the material of the top plate of the table which is in contact with the patient's body will be explained.
A solution for the stage of the tabletop is to use a material that attenuates and absorbs the scattered X-rays well for the tabletop itself and the material of the absorbing plate near the center line in the axial direction. Materials that attenuate X-rays are generally understood to be Pb, W, Ba, etc., and these are useful in a relatively high energy region close to primary X-rays. However, the scattered X-rays from the patient's body are lower in effective energy and photon number than the primary X-rays. Pb, W, Ba, etc. are materials that well attenuate and absorb scattered X-rays in the middle and low energy regions, but the material of Example 5 having a multilayer absorption layer (pair of diffusion absorber and electron absorber) Composite absorbent materials are even more effective. However, application of materials that attenuate and absorb X-rays shall not apply to the radiation field portion of Requirement 1.

The surface of the stage 10 of the top board which receives scattered X-rays from the patient's body is composed of the top board 11, the absorption plate 14, and the mesh transmission plate unit 15 as shown in FIG. The surface layer of the top plate 11, the absorber 14 plate, and the spacer 44 of the mesh transmission plate unit uses the composite absorber material of Example 5 capable of attenuating and absorbing scattered X-rays. Although the effect of reducing scattered X-rays is reduced, the low-reflection material of Example 6 may be used as a second best measure.
Scattered X-rays generated in the patient's body are directly transmitted downward through portions of the mesh transmission plate unit other than the spacers 44, that is, meshes. If this scattered X-ray is left unattended, the air dose rate in the examination room or the like will increase, so special measures by the intermediate stage 30 are required.
Moreover, the top plate 11, the absorbing plate 14, and the spacer 44 of the mesh transmitting plate unit may be made of a low-reflection material or a composite absorbing material instead of being covered with the composite absorbing material or the like.

A schematic diagram of the intermediate stage 30 is shown in FIG. As shown in FIG. 7, the intermediate stage 30 is composed of a slide table 32, its side rollers 34, a slide absorbing plate 33, a diaphragm plate 35, and their drive mechanisms. In FIG. 7, an upper arrow view AA shows a vertical cross-sectional view at the centerline position of the entire table in the axial direction, and a lower arrow view BB shows a transverse cross-sectional view of the intermediate stage 30. As shown in FIG.

The construction of middle stage 30 of FIG. 7 will now be described in more detail.
The slide table 32 of the intermediate stage 30 is shaped like a flat plate elongated in the axial direction. The slide table 32 moves in the axial direction on roller bearings of a pair of side rollers 34 installed inside the support rail 12 . The slide absorption plate 33 is attached to a portion of the upper surface of the slide table 32 that may be irradiated with scattered X-rays, and is simply fixed and installed. The slide absorbing plate 33 is a composite absorbing material having a thickness of less than 1.5 mm, and its dimensions and area may be changed according to the purpose of surgery. In addition, it may be moved during surgery, and a suction cup or an adhesive tape is better than fixing with a screw or the like as a fixing method.
The slide table 32 is preliminarily provided with a large hollow notch extending in the axial direction at a position corresponding to the candidate position of the irradiation field. The diaphragm plate 35 is installed across the hollow notch and can be slid and moved in the axial direction by sliding on the slide table 32 . The diaphragm plate 35 that slides on the slide table 32 is a pair (two plates) of solid square-cut flat plates that can freely adjust the aperture size in the axial direction of the irradiation field. When the operation is started, the opening angle of the diaphragm plate 35 is opened to the axial dimension of the irradiation field of the primary X-rays, so that the primary X-rays are transmitted as they are without being attenuated or absorbed by interactions.

Appropriate materials for the slide table 32, the slide absorption plate 33, and the aperture plate 35, which constitute the intermediate stage, will be described. The slide table 32 is not irradiated with primary X-rays, its scattered rays, scattered X-rays, and the like. For this reason, a Ti-based material is used in addition to the conventional table material such as Al-based material and CFRP, since light weight and a certain high strength to stand on its own are required.
Since the slide absorption plate 33 and the diaphragm plate 35 are irradiated with the scattered X-rays transmitted through the mesh surface of the mesh transmission plate unit 15 of the stage 10 of the top plate, the upper surface attenuates and absorbs the scattered X-rays. It is preferable to use a composite absorbent material of Also, since the lower surface of the diaphragm plate may be irradiated with primary X-rays and its scattered rays, the lower surface is preferably made of a low-reflection material or a composite absorption material. Although the composite absorbing material described above is less effective in reducing scattered X-rays, the low-reflection material of Example 6 may be used as a second best measure.

The structure of the aperture plate 35 of the intermediate stage 30 is shown in FIG. The diaphragm plate 35 is mounted in the opening of the slide table 32 at the center of the axis line of the diaphragm plate and its driving mechanism. A pair of two ball screws 61 are installed on both sides of the opening serving as an irradiation field. One of the diaphragm plates 35 (for example, the diaphragm plate (left) 62) can be moved in the axial direction by simultaneously rotating the two ball screws 61 by the same rotation angle manually or by mechanical power. Since both ends of the lower surface of the aperture plate 35 in the vertical direction of the axis line slide on the slide table 32, they are formed as sliding surfaces with high processing accuracy. A material having good slipperiness may be attached or applied to this portion. In FIG. 8, the aperture plate 35 is a solid flat plate with a square surface. A square cut flat plate may be used. Further, an additional square-cut flat plate may be connected during surgery to form a long rectangular aperture plate (left) 62 .
A nut bracket 64 is installed under the diaphragm plate (left) 62 on the left side (on the patient's head side) to change the rotation of the ball screw into axial movement. The right diaphragm plate (right) 63 is positioned at the end of the right side of the opening of the slide table 32 (on the side of the patient's leg) before starting surgery, or at the opening of the slide table 32 in consideration of the position of the affected area. It can be positioned at any position on the part and fixed easily. A simple fixing method does not need to be easily moved, so pinning such as insertion of an embedded boss on the slide table may be used. If, as a result of adjusting the position of the diaphragm plate 35 , an opening of the slide table 32 through which the scattered X-rays pass remains, it is closed with the slide absorption plate 33 .
The two ball screws 61 are provided with a mechanical device such as an electric rotating machine such as a servomotor or a pneumatic rotating machine (actuator) 68 such as a rotary actuator that rotates the ball screws synchronously at the same speed. A drive mechanism may be installed and driven. In addition, there are cases in which one rotating machine uses a gearbox to drive two in synchronism. In that case, the position of the irradiation field can be expanded or reduced during surgery within the movable range of the diaphragm plate (left) 62 .

The structure of the slide table 32 of the intermediate stage 30 is shown in FIG. The length of the slide table 32 and its longitudinal opening can be arbitrarily set at the time of manufacture, and the length may be long or short. The length is set at the time of manufacture depending on the purpose of the device.
Under the slide table 32, side rollers 34 such as a small roller conveyor are installed with many roller bearings. The slide table 32 installed on the side rollers 34 can be freely slid and moved in the axial direction. It can be moved or withdrawn during surgery if necessary. A mechanical drive mechanism such as an electric piston, a ball screw mechanism, or a hydraulic cylinder for moving the slide table 32 may be installed. In that case, in combination with the driving mechanism of the diaphragm plate 35, it is possible to change the position of the irradiation field and the size of the opening by the machine side or by remote control during surgery.
A groove 66 for accommodating and guiding the ball screw 61 in the axial direction is provided in the vicinity of both ends in the direction perpendicular to the axis on the back side of the slide table 32 . The groove 66 may be formed by hollowing out the slide table 32 or attaching a guide cover molded from the outer end with screws. A support unit 65 serving as a bearing for supporting the ball screw 61 is installed on both end faces in the axial direction. A manual or mechanically powered drive mechanism such as actuator 68 is provided to rotate a ball screw at the right (patient's foot) end of slide table 32 .

Many types of ball screw mechanisms are already on the market, and position adjustment by remote control using a ball screw is an existing knowledge. The ball screw mechanism generally consists of a ball screw that transmits rotation to a moving body, a ball screw nut bracket on the moving side that phases the rotation with displacement in the axial direction, and a support unit on the fixed side and support side that supports the ball screw as a bearing. consists of The support unit allows mounting on a fixed surface perpendicular to the axial direction of the ball screw, and mounting of moving parts such as a table on the nut bracket. The ball screw 61 is supported by a groove 66 inside or on the side of the slide table 32, and the moving side nut bracket 64 is installed on the lower bottom portion of the diaphragm plate 35 on the left side (the patient's head side). The support units 65 are installed at both ends of the slide table 32, with the fixed side on the left side (patient's head side) and the support side on the right side (patient's leg side).

An example of a combination of ball screw mechanism products manufactured by MISUMI is BSS1510-500 for the ball screw, NFB1510S-20 for the moving side ball screw nut bracket, BSW12 for the fixed side support unit, and BUN12 for the support side support unit. . These products are only examples, and other members and other companies' products can be constructed with similar functions. In addition, an example of using mechanical power to rotate two ball screws to operate a lift in the vertical direction is an example of utilization of a transport conveyor in MISUMI's inCAD Library. 244 (two ball screws simultaneously driven). This utilizes a gearbox to synchronously branch and transmit the rotation of mechanical power from one motor or the like to two ball screws to move the lifter up and down. Mechanical power such as motors may be two units that rotate synchronously.

(Solution for Requirement 4 “Radiation field position and dimension adjustment”)
Example 4 shows a specific example of a method for solving Requirement 4 (position and size adjustment of irradiation field). Here, a table of an undertube type X-ray transmission apparatus is shown as an example.
If the required minimum area of the irradiation field is set, the output of the X-ray source of the medical X-ray transmission device can be reduced, and the scattered radiation can be reduced by reducing the output. That is, it is possible to obviously reduce the air dose rate in the examination room, etc., improve the image quality of the X-ray receiver, and reduce the radiation exposure of the patient and the medical staff. In particular, if the output of the X-ray source can be made less than 88 KeV, the effect is great.
The area of the irradiation field can be adjusted to a rough dimensional width by the X-ray movable diaphragm of the X-ray source, but here, the position and dimensions of the irradiation field, that is, the area, are adjusted by a device attached to the table other than the X-ray movable diaphragm. will be explained.
During surgery, the position and size of the irradiation field are adjusted mainly in the middle step, and secondarily in the bottom plate step. Including the settings for starting the surgery, the functions of all stages including the stages of the tabletop are used.
Here, operations for adjusting the position and size of the irradiation field, that is, (1) setting the size of the irradiation field when starting surgery and (2) adjusting the size of the irradiation field during surgery, are described in Example 1. A general description will be given including the above-mentioned contents in 1 to 3.

First, (1) the setting of the position and size of the irradiation field when starting surgery will be described.
Although the stage 10 of the top plate is used at the beginning of the surgery, the width of the irradiation field in the axial direction can be adjusted according to the number of mesh transmission plate units 15 installed, that is, the aperture plate 35 and the opening/closing plate 22 can be selected during surgery. You can set the maximum axial width of the possible irradiation field. By selecting the spacer 44 of the mesh transmission plate unit 15 with an appropriate width from among various types, it is possible to set the aperture dimension in the direction perpendicular to the axis of the irradiation field. These countermeasures for the stage 10 of the top board are made in the initial stage, and in principle, they are not adjusted during the operation unless there is a strong need.
In the intermediate stage 30, the axial position of the slide table 32 is moved and adjusted according to the position of the affected area, and the ball screw 61 adjusts the axial opening size of the diaphragm plate 35, thereby achieving the purpose of the operation. It is possible to set the primary X-ray irradiation field at a necessary and sufficient position and area for .
In the stage 20 of the bottom plate, the opening/closing plate 22 of the portion of the irradiation field necessary for the purpose of the operation is opened by a hinge mechanism or a sliding function to set the position of the necessary and sufficient primary X-ray irradiation field. be able to. The vertical width of the field axis can also be adjusted with the hinge mechanism.

Next, (2) the adjustment of the size of the radiation field during surgery, which is performed as necessary, will be described.
The adjustment at the table position consists of changing the size of the irradiation field by the slide table 32 and the aperture plate 35 at the intermediate stage 30 described in Requirement 2 (“adjustment of the irradiation field”), and changing the size of the table 1 described in Requirement 1. It is necessary to change the position of the notch through which the primary X-ray is transmitted by the open/close plate 22 on the step 20 of the bottom plate (the same “transmission surface adjustment”). These are dealt with by the function of the table 1 having a three-stage structure having a function of adjusting the positions of various materials.
For the stage 10 of the top plate, the number of mesh transmission plate units 15 to be installed and the width of the spacers are selected at the beginning of the surgery as described in the previous section, and are not positively changed during the surgery.

Adjusting the size of the field during surgery in the middle stage will now be described.
In the intermediate stage 30 , the irradiation field is adjusted by adjusting the rough position in the axial direction with a slide table 32 and adjusting the detailed aperture size in the axial direction with a pair of aperture plates 35 attached to the slide table 32 . The slide table 32 slides in the axial direction to change the dimension of the irradiation field in the axial direction. The diaphragm plate 35 is driven by a ball screw 61 to freely adjust the opening dimension of the two diaphragm plates in the axial direction.
The slide table 32 and diaphragm plate 35 can be slid and adjusted even during surgery. Also, these slides can be manually operated, but there are cases where the mechanical driving mechanism described in the third embodiment is installed. In this case, the position of the irradiation field can be changed by remote control during surgery, and the size of the aperture in the axial direction can be enlarged or reduced. FIG. 10 shows an explanatory view of the position and size adjustment of the irradiation field by the slide table 32 and diaphragm plate 35 of the intermediate stage 30. As shown in FIG.
FIG. 10 shows an example in which an irradiation field is set near the patient's heart. The width of the irradiation field in the axial direction is set by the opening/closing plate 22 and the aperture plate 35, and primary X-rays and their scattered rays are not irradiated to the patient's body other than the width. Scattered X-rays from the patient's body are mainly attenuated and absorbed by the top plate 11 and the absorption plate 14 . Scattered X-rays in portions of the mesh transmission plate unit 15 other than the irradiation field are attenuated and absorbed by the diaphragm plate 35 located below and the slide absorption plate 33 on the slide table. The slide absorption plate 33 is a thin plate simply stuck on the slide table 32, and the position can be changed according to the irradiation position of the scattered X-ray, the length in the axial direction can be lengthened, and the area can be increased. can be done.
In FIG. 10, four mesh transmission plate units 15 are installed in place of the absorption plate 14 before surgery. As a result, the entire range of the patient's upper body can be changed and set as an irradiation field by manipulation during surgery while maintaining the radiation exposure of the patient and the medical staff in a reduced state. In FIG. 10, up to eight mesh transmission plate units 15 can be installed. In FIG. 10, the mesh transmission plate unit 15 is shown to be composed of eight pieces for the sake of explanation, but the number of these units may be larger. The greater the number of installed mesh transmission plate units 15, the wider the maximum width of the irradiation field that can be selected during surgery. However, from the viewpoint of reducing the air dose rate in the examination room or the like as much as possible, the smaller the number of mesh transmission plate units installed before surgery, the better.

Next, the adjustment of the size of the radiation field during surgery on the stage of the bottom plate will be described.
In the stage 20 of the bottom plate, the position of the irradiation field is adjusted by opening and closing the low reflection/scattering opening/closing plate (opening/closing plate) 22 with a hinge mechanism or a slide mechanism to change the notch through which primary X-rays pass. In the case of a hinge mechanism, the aperture size in the direction perpendicular to the axis of the irradiation field can also be adjusted. In FIG. 10, eight pairs of opening/closing plates 22 are shown for the sake of explanation, but the number may be larger. FIG. 11 is an explanatory view of the position and size adjustment of the irradiation field by the opening/closing plate 22 using the hinge mechanism of the step 20 of the bottom plate. FIG. 11 shows the position of arrows DD in FIG. Fig. 11a is a diagram for an open angle of 90° (fully open), b is for an open angle of 60° (2/3 open), and c is for an open angle of 45° (1/2 open).
In FIG. 11, the magnitude of the aperture width in the vertical direction of the axis of the resulting irradiation field is: a (fully open) at an opening angle of 90°> b (2/3 open) at 60°> c (1/2) at 45° open). Although these three opening angles are shown in FIG. 11 for explanation, more opening angles may be set. In FIG. 11, the aperture dimension in the direction perpendicular to the axis of the maximum irradiation field is the opening angle a of 90°. You can't get big. Although it is not expected that there will be many surgeries in which the patient's entire chest and abdominal circumferences are viewed through, if necessary, the opening angle of the opening/closing plate 22 can be set to 90°, and the slide table 32 can be pulled out to maximize the vertical direction of the axis. The width of the irradiation field can be obtained.
The opening and closing plates 22 can be opened and closed manually, but there are cases where a mechanism for driving several or all pairs of opening and closing plates by mechanical power such as a cam mechanism is installed. In this case, the opening/closing plate 22 can be opened/closed and the angle of opening can be changed by remote control during surgery, the position of the irradiation field can be changed, and the size of the opening in the vertical direction of the axis can be enlarged or reduced.

(Composite absorbent material of Patent Document 4)
Patent Document 4 by the same inventor devises a composite absorbing material that absorbs scattered X-rays while attenuating them well. The composite absorbing material is placed on the surface irradiated with scattered X-rays from the patient's body, and attenuates the incident scattered X-rays as efficiently as possible, absorbs the linear energy, and rescatters the scattered X-rays. The purpose is to reduce X-rays are annihilated by converting their energy into kinetic energy such as photoelectrons due to attenuation and absorption by the composite absorbing material. The composite absorbing material is mainly composed of a low reflection attenuation layer (initial layer) such as lead (Pb) or the like and multilayer absorbing layers (one to three pairs of a diffusion absorber and an electron absorber). That is, the composite absorbing material attenuates and absorbs scattered X-rays from a scatterer such as a human body tissue or a table by means of a material in which three or more layers having different roles are adhered and stacked in multiple layers.

The principle of composite absorbent material will be explained. Incident X-rays that are mainly targeted by composite absorbing materials are not primary X-rays but scattered X-rays that have been scattered one or more times by a substance. Energies are targeted below 88 KeV.
When X-rays interact with matter in the photoelectric region, most of the incident X-rays are absorbed in linear energy due to the photoelectric effect. When the energy of incident X-rays exceeds the absorption edge, photoelectrons, characteristic X-rays and Auger electrons are emitted due to the photoelectric effect. Further, bremsstrahlung X-rays are generated by bremsstrahlung radiation of these electrons. In a slightly higher energy region near the absorption edge, a singular absorption occurs, in which the photoelectric absorption is remarkable.
Pb in the first low-reflection-attenuation layer attenuates most of incident X-rays well and absorbs linear energy well. The K-edge of Pb is 88 KeV and the L-edge is about 13-16 KeV. That is, even in the case of a medical X-ray apparatus, characteristic X-rays (L-X-rays) of about 10.5 to 14.8 KeV are emitted from the surface of Pb due to the L absorption edge.
In the energy region between the K and L absorption edges of Pb (17 to 87 KeV), singular absorption occurs in elements with an atomic number of 37 or more and less than 81, and K Photoelectric absorption is significant between the absorption edges.
The multi-layer absorption layer utilizes specific absorption and aims to efficiently extinguish X-rays with a pair of a diffusion absorber and an electron absorber. Elements with an electron absorption fraction of less than 70% at certain monochromatic energies in this energy range (eg 60/50/40/30/20 KeV) are extracted as diffuse absorbers. See Table 1 for the linear attenuation coefficient μ, the linear energy absorption coefficient μen, and the electron absorption ratio (μen/μ) for monochromatic energy.
Diffusion absorbers undergo significant linear attenuation due to singular absorption at the K absorption edge, and also significantly absorb linear energy. line) is also re-emitted. That is, absorption plus re-emission of secondary X-rays in many directions diffusely pushes back photons that have been attenuated in the surrounding layers (i.e., they move more zig-zags over longer distances in a thin layer of material). ) also has a role.
The electron absorber is an element with an atomic number of 11 or more and 82 or less that absorbs secondary X-rays, etc., and absorbs X-rays well with a specific energy extracted from the diffusion absorber, that is, the electron absorption rate is 70. % or more, it is an element that absorbs electrons well.
That is, by coexisting a diffusion absorber and an electron absorber as a pair, X-rays are diffused and pushed back in a thin material layer, and electrons are absorbed while the X-rays travel back and forth many times.
In the multi-layer absorption layer, one to three pairs of diffusive absorbers and electron absorbers are superimposed without gaps, so that X-rays are efficiently extinguished while passing through the thin multi-layered material many times. , into kinetic energy such as photoelectrons.

Materials used for the composite absorbent material will be described.
The low reflection attenuation layer (first layer) is set to 0.1 to 0.3 mm of Pb.
A pair of multilayer absorption layers is a pair of a diffusion absorber and an electron absorber by looking at the value of the linear energy absorption coefficient μen and the electron absorption ratio (μen/μ) at an arbitrary monochromatic energy set other than the K absorption edge. Set the element (material) that becomes
When the monochromatic energy for setting the diffusion absorber is 50 KeV, the single element or compound of the element or the compound that has the electron absorption ratio μen/μ at 50 KeV in Table 1 of less than 70% and is used as the diffusion absorber is Sn or Ba. The single element or the compound of the element serving as the electron absorber which is equal to or greater than 70% is Fe, Cu, Nb or Mo. W or Pb can be placed in the electron absorber, and if there are some placed in adjacent layers, these placed in other roles can also serve and be integrated.
When the monochromatic energy for setting the diffusion absorber is 30 KeV, the single element or compound of the element or the compound that serves as the diffusion absorber with the electron absorption ratio μen/μ at 30 KeV in Table 1 below 70% is Nb, Mo or Sn. The single element or compound of the element serving as the electron absorber which is equal to or greater than 70% is Ti, Fe or Cu. Ba, W, or Pb can be placed in the electron absorber, and if there are some placed in adjacent layers, these placed in other roles can also be integrated.

Next, the operation of setting the combination of the diffusion absorber and the electron absorber for the entire multilayer absorption layer (method of designing the multilayer absorption layer) will be described. The electron absorption region is an X-ray energy region in which the electron absorption ratio (μen/μ) of each element is 70% or more. Separately, the photon emission region is a region where this is less than 70%. These are set for monochromatic X-ray energies shown in the NIST database in Table 1.
Pb, which scatters less in this energy region, is used for the first layer that receives scattered X-rays of less than 88 KeV from a scatterer (body tissue, table, filtering filter, etc.).
For example, 40 to 60 KeV (median value: 50 KeV) is intentionally targeted for the first diffusion absorber in the second layer, and an element such as Sn, which is in the photon emission region, is used in this region.
For the electron absorber of the third layer as opposed to the second layer, an element such as Mo or Nb, which is in the electron absorption region in the region of 50 KeV, is used. Although the thickness increases, Cu or Fe may be used.
For example, for the second diffusion absorber in the fourth layer, 20 to 40 KeV (median value: 30 KeV) is intentionally aimed, and an element such as Nb or Mo, which is separately in the photon emission region, is used in this region.
For the electron absorber of the fifth layer as opposed to the fourth layer, an element such as Cu or Fe, which is in the electron absorption region in the region of 30 KeV, is used. Al, Si, and Ti may be used depending on the conditions. Since the K-absorption edge of Ti is 4.96 KeV, the K-absorption edge of the elements forming the diffused absorber of the multilayer absorption layer is inevitably 5 KeV or more.
With the above configuration, scattered X-rays of less than 88 KeV can be annihilated and converted into kinetic energy of electrons.

Composite absorbent material is one of the primary materials that make up the structure of the present invention. By using composite absorbent materials, the radiation dose rate in spaces such as examination rooms can be reduced. As a result, the image quality of the X-ray receiver can be made clear, and the radiation exposure of patients, etc. and medical personnel can be properly minimized. The configuration of the base case of the composite absorbent material is illustrated in FIG.
FIG. 12 shows a Pb low reflection attenuation layer (first layer) 3081 and a multilayer absorption layer 3081 when the outermost layer of the multilayer absorption layer 90 is made of Al, Si, Mg, or the like, which has a low fluorescence yield and low energy of the generated characteristic X-rays. A base case configuration consisting of only layers 90 (1-3 pairs) is shown. FIG. 12a. is an explanatory diagram of the configuration; b. is a composite absorber material 71 in which the multilayer absorber layer 90 consists of two pairs of diffusion absorbers 91 and electron absorbers 92, forming a total of five layers; c. is a composite absorbing material 72 in which the multi-layer absorbing layer 90 consists of three pairs of diffusion absorbers 91 and electron absorbers 92, making up a total of seven layers; d. shows a composite absorbing material 73 in which the multilayer absorbing layer 90 consists of a diffusion absorber 91 and an electron absorber 92 paired to form a total of three layers.
Examples of material combinations here are Pb--Sn--Nb--Cu--Al for a total of 5 layers, Pb--Ba--Sn--Nb--Cu--Fe--Al for a total of 7 layers, and a total of 3 layers. In some cases, it is Pb--Nb--Si. Fe and Cu, which are combinations of elements with similar properties, may be combined to form a total of 6 layers of Pb--Ba--Sn--Nb--Cu--Al in the case of a total of 7 layers.
The low reflection material of Example 6 may be used as a second best measure, although the effect of reducing scattered X-rays is reduced at the site where the composite absorption material is used.

(low reflection material)
The low-reflection material is placed on the surface irradiated with the primary X-rays and its scattered rays for the purpose of reducing the generation of scattered X-rays due to reflection and scattering.
A low-reflection material is a material coated with a low-reflection element such as Pb.W or Ba.Sn.Mo.Nb. A low-reflection element is an element with an atomic number of 20 or more, which is in a region (photoelectric region) in which the photoelectric effect is dominant even in an energy region of 80 KeV or more, and has μ of 10 (1/cm) or more at a monochromatic energy of 80 KeV. is an element. More preferably, it is an element with μen of 10 (1/cm) or more at 80 KeV.
Here, μ is a linear attenuation coefficient, μen is a linear energy absorption coefficient, and μen/μ is an electron absorption ratio. .

A material used for the low-reflection material will be described.
The primary X-ray energy of medical X-ray fluoroscopy equipment is in the range of 50 to 150 KeV. Elements in the photoelectric range are used in the primary X-ray energy range in order to avoid reflection due to Compton scattering in low-reflection materials. There is a need to. According to the description of Patent Document 4, elements with an atomic number of 20 or more are in the photoelectric region even in the region of 80 KeV or more.
On the other hand, according to Table 1, for absorbing elements (Fe, Cu, Nb, Mo, Sn, Ba, W, Pb) other than Ti, both μ and μ en are considerably large at less than 80 KeV. However, when Fe and Cu reach 80 KeV, μ and μ en become 10 (1/cm) or less.
Absorbing elements Nb, Mo, Sn, Ba, W, and Pb have a large μ even at 80 KeV or more, and W and Pb in particular have a large μ of 10 (1/cm) or more even at 100 KeV or more. Furthermore, W and Pb have a large μen of 10 (1/cm) or more even at 100 KeV. μ en of Nb, Mo, Sn, and Ba is 10 (1/cm) or more at 60 KeV, but becomes 10 (1/cm) or less at 80 KeV.
A large linear attenuation coefficient μ means high linear attenuation capability (that is, shielding capability). A large linear energy absorption coefficient means high linear energy absorption capacity (that is, electron absorption capacity), and the interaction with X-rays results in less reflection and scattering and greater absorption.
Therefore, preferable low-reflection elements are W and Pb, and elements that are slightly inferior in low-reflectivity at 80 KeV but can be expected to have a certain effect are Ba.Sn.Mo.Nb.

The composite absorbing material has a low reflection attenuation layer as the first layer, and mainly uses Pb. Besides Pb, Bi, U and Th have been proposed. That is, the Pb of the first layer is the same as that proposed as the low reflection material. The composite absorbing material is composed of a multi-layer absorbing layer (one to three pairs of diffusion absorber and electron absorber) in addition to the low reflection attenuation layer. That is, the composite absorbing material can attenuate and absorb scattered X-rays generated when the first layer of Pb is attenuated by the multi-layered absorption layer. Therefore, it is better to use the composite absorbing material of Example 5 instead of coating the surface using the low-reflection material.

In Example 7, the bird's-eye view shown in FIG. 13 will be described.
The bird's-eye view of FIG. 13 shows the structure divided into three stages of a top plate, an intermediate plate, and a bottom plate. However, the support rails 12 and the reinforcing beams 13 are shown together with the table support base 2 on the bottom plate step 20 instead of on the top plate step 10 for the sake of clarity.
The steps of the top plate are composed of the top plate 11 , the absorption plate 14 , the mesh transmission plate unit 15 , the support rails 12 and the reinforcing beams 13 . The top plate 11 supports the weight of the patient's body on which the patient lies. The top plate 11 has an axially long opening at the center of its axis, and the absorbing plate 14 is installed by being fitted onto the support rails there. The absorption plate 14 at a position that may become an irradiation field is removed, and a mesh transmission plate unit 15 is installed. The mesh surface of the mesh transmission plate unit 15 is made of a material such as CFPR, Al, etc., which has a high strength and hardly absorbs X-rays. In the case of the undertube type, the upper surfaces of the top plate 11 and the absorbent plate 14 are covered with a composite absorbent material. By covering the edge of the mesh transmission plate unit 15 in the direction perpendicular to the axis with a spacer 44, the aperture size of the irradiation field in the direction perpendicular to the axis can be adjusted. (a) shows the mesh transmission plate unit 15 with a wide width, and (b) shows the mesh transmission plate unit 15 with a narrow width. The load supported by the top plate 11 is supported by the support rails 12 and the reinforcing beams 13, and finally supported by the table support base 2. - 特許庁
The intermediate stage 30 is composed of a slide table 32 and its side rollers 34, a slide absorption plate 33, a diaphragm plate 35 and their drive mechanism. The slide table 32 is a flat plate elongated in the axial direction, has an opening at a part of the center of the axis, and a slide absorbing plate 33 is easily fixed on the other part. A driving mechanism such as a ball screw 61 for the aperture plate 35 is mounted inside the slide table 32 . A pair of (two) diaphragm plates 35 can be slid over the opening of the slide table 32 to freely adjust the size of the opening in the axial direction. The slide table 32 installed on the side rollers 34 can be slid and moved in the axial direction to freely adjust the position of the opening. The position and size of the opening in the axial direction of the irradiation field can be adjusted by the slide table 32 and the aperture plate 35 . The slide table 33 and diaphragm plate 35 may be provided with a mechanical driving mechanism. In the case of the undertube type, the upper side of the diaphragm plate 35 is covered with a composite absorbent material 70 and the lower side with a low reflection material 80 . The slide absorbing plate 33 is simply installed locally except for the opening of the slide table 22 and covered with the composite absorbing material 70 on the upper side.
The step 20 of the bottom plate is composed of a bottom plate 21, a low reflection scattering opening/closing plate (opening/closing plate) 22, and its fixing/driving mechanism. The opening/closing plate 22 can be opened/closed by controlling the opening angle with a hinge mechanism or the like. During surgery, the opening/closing plate 22 at the position of the irradiation field is opened. In the case of the undertube type, the opening/closing plate 22 is coated with a low-reflection material on the outside and a composite absorbing material 70 on the inside. The opening/closing plate 22 may be provided with a mechanical driving mechanism.

A solution to requirement 1 (transmission of primary X-rays) was shown in Example 1, but Example 2 shows a modified example that is another specific example. The wires and nets installed in the mesh transmission plate unit 15 of the stage 10 of the top plate described in Example 1 allow primary X-rays to pass through well. The image of the X-ray receiver may have a faint white shadow like graph paper. Therefore, here , a strip-shaped film or flat plate material (hereinafter referred to as " A case where a thin sheet") is used in the sheet transmission plate unit 60 will be described.

For example, in a non-apertured table made of CFRP with a thickness of t = 5 cm and a table with an aperture for a transmission plate unit of assumed width 10 cm x length 10 cm, a monochromatic primary X-ray transmittance of 60 KeV uniform over the entire width is compare. Assuming that the transmittance I ₀ of the table in the open state is 1000, from Table 1, μ of carbon (C) is 0.18 (1/cm), so the relational expression I/I ₀ =Exp(−μt) In the case of a non-opened table, the transmission amount I is about 400, and the transmission ratio I/ _I0 is 40%. Here, since one wire mesh with a diameter of 5 mm is required at an interval of 10 cm, it is approximate that two wires are used vertically and horizontally, but the equivalent average thickness is 0.25 mm. 996, and the transmittance I/ _I0 is 99.6%. Further, in the case of the sheet transmission plate unit 60 using a thin plate sheet with a thickness of 0.5 mm on one side, the transmittance I is about 991, and the transmittance I/ _I0 is 99.1%. As described above, in this trial calculation example, the transmittance of the wire rod, the mesh, and the thin plate sheet is at least twice as high as that of the non-opened table, which is almost equal to that of the open table. However, the transmittance of the thin sheet is about 0.5% lower than that of the wire or mesh. However, the thin sheet has the advantage that the image of the X-ray receiver does not contain any thin white shadows such as that of grid paper due to wires or nets.

FIG. 5 shows an explanatory diagram of the structure of a sheet transmission plate unit 60 using a thin plate sheet (a belt-shaped film and a plate or an integrally molded product). FIG. 5 is an explanatory diagram of the structure of the transmission plate unit in the case of the thin plate sheet on the stage of the top plate. In FIG. 5, d shows the case of a belt-shaped film 49 of thin sheet, e shows the case of a thin sheet (elastic flat plate) 50, and f shows the case of an integrally molded product.

In the case of the thin sheet of Example 8 , as in the case of the wire or mesh of Example 1, the primary X-rays that pass through can be further increased by reducing the thickness. Therefore, the first method for reducing the thickness of the portion of the thin sheet placed in the irradiation field is to increase the strength of the material of the thin sheet itself as much as possible. Here, the necessary thickness is estimated from the result of the tensile strength calculated from the vertical cross-sectional area (thickness×width of the short side) of the thin plate sheet. If the width of the short side is as short as 10 cm and the thickness of the thin sheet is 0.1 mm, the longitudinal cross-sectional area of the smaller side is 0.1 cm ² . CFRP or GFRP with a longitudinal cross-sectional area of 0.1 cm ² has a tensile strength of about 200 to 4,000 kg from the range of tensile strength in Table 2. That is, even when the patient's body weight is 100 kg, the mechanical strength requirement is fully satisfied. Even if the candidate material has a tensile strength of 100 MPa (1,019 kg/cm ² ), the actual thin sheet also has a long side width that results in a larger longitudinal cross-sectional area. In addition, it is difficult to imagine that a patient lying on a table puts his or her entire weight on an area of 10 cm width. In addition, in the case of thin sheets, it is not necessary to consider biting into the patient's skin. Furthermore, since the thin sheet is much thinner than the patient's body and table, it absorbs and scatters less primary X-rays. In addition, wire rods or nets and thin sheets may coexist and both may be used. However, if an extremely thin film cannot be obtained, the amount of transmission of primary X-rays will be reduced by that amount, and the image quality of the X-ray receiver will be deteriorated. As for the thickness of the thin plate sheet, the thinner the better, as long as there is no problem in terms of strength. In general, the thickness of the patient's body is about 150 to 300 mm depending on the part, whereas the thickness of the table is about 50 mm. In order to improve the image quality of the X-ray receiver, it is desirable that the thickness of the thin sheet be less than one-fifth the thickness of the table, and better less than one-tenth the thickness of the table. To ensure that the thickness is less than 1/10 of the thickness of the table, the thickness of the thin sheet must be less than 0.5 mm.

Especially in the case of CFRP and GFRP, the tensile strength is extremely high in one direction in which carbon fibers and glass fibers are installed during manufacturing. In addition, by devising a weaving method in which flat plates of CFRP or GFRP having a narrow width are crossed, the tensile strength in two directions can be made extremely high. However, since the self-supporting strength based on the bending strength is not high, the thin CFRP or GFRP becomes a loose and elastic flat plate unless a separate support material is provided. This tendency is the same for metal Al and Mg thin film materials.
A second method for reducing the thickness of the portion of the thin sheet placed in the irradiation field is to use the high tensile strength of the thin sheet as effectively as possible by devising the structure for placing the thin sheet. In other words, this utilizes the fact that the surface supporting the weight of the patient's body on the table does not have to be a rigid body, and may be elastically recessed along the patient's body. .
However, the force supported by the dented thin plate sheet must be supported by another strength member and transmitted to the support rails 12 of the table. This strength member should be a rectangular, hollow structure located outside the field. In Example 2, this rectangular hollow structure devised a frame 43 . The frame 43 has a shape obtained by combining rectangular materials with a thickness slightly smaller than that of the table into a square, and has high strength as a beam. The material of the frame 43 is mostly CFRP or GFRP moldings, and Al-based or Mg-based metal pillars and molds may be used. If the frame 43 is installed in a position sufficiently removed from the irradiation field, the material of the frame 43 may be other metals such as Ti-based metals. On the other hand, the thin sheet has extremely high tensile strength, but the band-shaped film 49 and the elastic flat plate 50 are considered to be wobbly without being self-supporting.
As described above, the weight of the patient's body to be placed on top is supported by the tensile strength of the thin sheet itself, and the reaction force is supported by the strength of the frame 43, thereby further reducing the thickness of the thin sheet at the site placed in the irradiation field. can.

CFRP molding methods include autoclave molding, resin transfer molding (RTM) molding, hot press molding, sheet molding compound (SMC), sheet winding molding, pultrusion molding, and injection molding. There is In autoclave molding, hot press molding, SMC, and sheet winding molding, a sheet-like intermediate material called a prepreg is produced by impregnating carbon fibers with a resin in advance. The shape and dimensions of the product obtained by the molding method differ, and the performance of the obtained product greatly varies depending on the molding method. It is necessary to select the optimum molding method according to the required characteristics of the product, such as the type of resin, intermediate materials, shape, cost, quantity, and quality.
The thin sheet (belt-shaped film) 49 described below is often manufactured by a sheet winding molding method or the like, and the thickness expected for this product is 0.1 mm or less. The thin sheet (elastic flat plate) 50 is often manufactured by a hot press molding method, SMC, or the like, and the expected thickness of this product is 0.5 mm or less. An integrally molded product of CFRP is often manufactured by the RTM molding method or the like, and the thickness of the thin plate sheet portion is 0.5 mm or less like the strip film 49 . The filament winding molding method is a method of molding CFRP wires. Carbon fiber yarns with a diameter of 5 micrometers (μm) made by baking acrylic fibers under special conditions of about 1000°C are bundled together and mixed with resin. Manufactured by baking the layers. A carbon fiber tow is an untwisted bundle of fibers in which fine filaments (single yarns) with a diameter of 5 to 15 μm are aggregated. It is often used as an intermediate product and processed into various forms. In general, a thin bundle of 1,000 to 30,000 filaments (about 0.1 to 3 mm in diameter) is called small tow, and a thick bundle of 48,000 filaments or more (about 4.8 mm or more in diameter) is called large tow. An example of CFRP wire products is carbon fiber tow (long fiber) manufactured by Mitsubishi Chemical Corporation. The model number of the wire with a diameter of about 5 mm is TRW40-50L, and its tensile strength is 4,120 MPa.

FIG. 5d shows a case in which the thin plate sheet (strip film) 49 constitutes the sheet transmission plate unit 60 and the like. It is a structure placed on the support rail 12 as a strip. d-1 of FIG. 5 is a partial explanatory view. That is, the strip film 49 is an endless tape such as CFRP, GFRP, etc. By adjusting the circumferential length of the tape in advance, the strip film 49 is tightly fitted into the rectangular hollow frame 43 without any extra space. As a result, when the weight of the patient's body is applied, a tensile force is applied in the circumferential direction, and although the belt-shaped film 49 is slightly dented and deformed, it supports the weight of the patient's body with its tensile strength, and is further formed into a rectangular shape. A hollow frame 43 supports the . If the belt-like film 49 whose length is precisely adjusted can be prepared, it is inexpensive and easy to handle. The frame 43 incorporating the strip film 49 is placed on the adjuster 46 and adjusted so that it is at the same height as the table surface.

FIG. 5e shows a case where a thin plate sheet (elastic flat plate) 50 constitutes a sheet transmission plate unit 60 and the like. is a structure fixed to the frame 43 of the . FIG. 5 e-1 is a partial explanatory view. The elastic flat plate 50 should have a thickness of 0.5 mm or less in order to transmit primary X-rays better than a normal table. The flat elastic flat plate 50 of 0.5 mm or less has high tensile strength but does not have self-supporting strength and is wobbly, so it is fixed to the frame 43 which is a strength member. The length of the short side (or the long side) of the elastic flat plate 50 is made longer, and the ends thereof are wrapped around a bar 57 and fixed with a pin 58 or the like. As a result, the elastic flat plate 50 is slightly dented and deformed, but with its tensile strength it supports the weight of the patient's body placed thereon, and the rectangular hollow frame 43 supports it. The frame 43 to which the planar elastic flat plate 50 is fixed is placed on the adjuster 46 and adjusted so as to be flush with the table surface.

FIG. 5f shows a case where the sheet transmission plate unit 60 and the like are configured by the integrally molded product 45, and shows the case where the elastic flat plate 50 of the thin sheet is integrally molded with the adjuster 46. FIG. Molded products such as CFRP and GFRP are generally manufactured by the RTM molding method or the like. That is, after arranging carbon fibers or glass fibers in a mold, a thermoplastic resin or the like is injected and solidified. The frame 43 described above is also often manufactured in this process. In this manufacturing process, if the height information required for the adjuster 46 is known, prepare a mold corresponding to the shape of the elastic flat plate, frame, and adjuster shown in FIG. 5e. , the integrally molded product 45 can be manufactured. Since the integrally molded product 45 does not require assembly, it has the advantage of saving labor at the site.

Candidate products on the market corresponding to CFRP thin sheet (belt-shaped film) 49 were investigated. An example is a carbon fiber sheet manufactured by Mitsubishi Plastics, Inc., the product name of which is registered as a trademark. The original purpose of this carbon fiber sheet is to repair and reinforce concrete structures that are used by bonding, and it is used as a sheet-like repair/reinforcement material in which high-strength, high-modulus carbon fibers are aligned in one direction. It has a specific gravity one-fifth that of iron, ten times more tensile strength than steel, and three times more elasticity than steel. Durability is said to be excellent in chemical resistance without deterioration in strength due to ultraviolet rays.
There are also cross-type products in which high-strength carbon fibers are aligned in two directions, and for example, the thickness of type 20 (MRK-2D2-20) is as thin as about 0.06 mm. Its tensile strength is 2900 N/mm ² (=2900 MPa), and its tensile modulus is 230 KN/mm ² . That is, the thin thickness and high strength of this product are sufficient for forming the sheet transmission plate unit 60 and the like with the strip film 49 of the thin sheet. However, since the product is supplied in the form of a roll, bonding with an adhesive or the like is required to form an endless strip. The standard amount of adhesive resin such as epoxy resin used for impregnation is 0.6 kg/m ² .

Candidate products on the market corresponding to CFRP thin sheet (elastic flat plate) 50 were investigated. Some CFRP thin sheet products do not strictly indicate the manufacturing method and tensile strength. This is because values such as tensile strength vary greatly depending on the molding method, type of resin to be impregnated, intermediate material, curing conditions and weaving method.
A first example is a carbon plate (3K, plain weave) manufactured by NEWS COMPANY. The material composition of this product is about 60% carbon fiber, about 40% epoxy resin, and has a specific gravity of 1.52 kg/cm ³ . The shape of the product is commercially available with an effective size of 49 cm wide by 49 cm long and a thickness of 0.2 to 5 mm. This product is molded by a hot press molding method after lamination of prepregs. The lamination method is to laminate several layers by plain weave. However, there is no description of tensile strength. Even in this case, the lowest numerical value in Table 2 is expected to be satisfactory, but if the tensile strength is 200 MPa, it is possible to support the weight of a patient's body of 100 kg or more even with a thickness of 0.5 mm. .
A second example is a thermoplastic resin laminate TPCL manufactured by Teijin. The material composition of this product is that the fiber is carbon fiber and the matrix is PEEK resin. The specific gravity is 1.30 to 1.76 kg/cm ³ depending on the ratio of the two. The shape of the product is, for example, 80 cm wide×120 cm long and 0.31 mm thick. This product is press-molded by pressing it against a die within a few minutes after heating. Since the typical tensile strength is 60,000 MPa, it is possible to support the patient's body weight of 100 kg or more even with a thickness of 0.31 mm.

1. table (bed)
2. table support 3. 4. patient body; Notch 5 . Irradiation field6. width of the irradiation field;7. 8. Maximum width for which the irradiation field can be selected during surgery. Primary X-rays from an X-ray source9. Scattered X-rays from patient body10. 20. Top plate step. Bottom plate steps 30 . intermediate stage 11 . top plate 12 . support rails 13 . reinforcement beams 14 . absorber plate 15 . mesh transmission plate unit 16 . A structure 21 in which wires are arranged in a grid pattern. bottom plate 22 . Low-reflection scattering switching plate (switching plate)
23. base material 24 . Base material (Al system)
25. Base material (Ti-based)
31. middle 32 . slide table 33 . Slide absorbing plate 34 . side rollers 35 . Aperture plate 41 . wire 42 . net (mesh)
43. frame 44 . spacer 45 . integrally molded product 46. Adjuster 47 . Wide 48. Narrow 49. Thin sheet (strip film)
50. Thin sheet (elastic flat plate)
51. Open/close plate (closed)
52. Open/close plate (open)
53. folding hinge 54 . Open/close plate (left)
55. Open/close plate (right)
56. handle cover 57 . bar 58. pin 60 . sheet transmission plate unit 61 . ball screw 62 . Aperture plate (left)
63. Aperture plate (right)
64. nut blanket 65 . support unit 66 . groove 67 . Lower plate 68 . actuator 70 . Composite absorbent material 71.2 pairs for a total of 5 layers composite absorbent material 72.3 pairs for a total of 7 layers composite absorbent material 73.1 pair for a total of 3 layers composite absorbent material 80. low reflection material 81 . Low reflection attenuation layer (first layer)
90. multilayer absorbent layer 91 . diffusion absorber 92 . electron absorber

Claims (41)

On a table on which a patient's body is placed in a medical X-ray transmission device,
At the site of the irradiation field where the primary X-rays are irradiated,
A net composed of a single element or a compound of an element with an atomic number of 14 or less is placed on the top plate of the top plate, and X-rays are transmitted through the net, thereby suppressing the absorption and scattering of X-rays by the top plate. A table characterized by A table on which a patient's body is placed for an undertube type X-ray transmission apparatus for medical use, wherein a bottom plate step and/or an intermediate step is provided below the top plate step,
At the site of the irradiation field where the primary X-rays are irradiated,
In the bottom plate and/or in the middle step, notches are provided to allow the hollow free space to pass through,
A table characterized by suppressing the absorption and scattering of X-rays by the table by passing through a net composed of a single element or a compound of an element having an atomic number of 14 or less on the top plate of the stage of the top plate. In the table of claim 2,
A slide table with a hollow through surface is installed on the intermediate stage, which is a rectangular parallelepiped plate that is long in the axial direction,
A plurality of open/close plates, which are solid cut flat plates, are installed in the axial direction on the steps of the bottom plate,
one or more of the opening/closing plates are opened in the vertical direction of the axis;
moving the hollow penetrating surface of the slide table above the opening position of the opening /closing plate,
By aligning the cutouts of the open / close plate and the hollow penetrating surface of the slide table,
A table characterized by the ability to adjust the irradiation field to the position required for medical purposes even during surgery In the table of claim 3,
Among the many opening and closing plates provided on the bottom plate stage, the opening and closing plates in the irradiation field are opened so that the primary X-rays can pass through as they are.
In the intermediate stage , the diaphragm plate is installed across the hollow notch of the slide table, and the opening size in the axial direction of the irradiation field can be freely adjusted,
reducing the generation of scattered X-rays due to primary X-rays and their scattered radiation,
In the intermediate stage, the irradiation field is narrowed down to the minimum required aperture size,
By attenuating and absorbing the scattered X-rays generated by the patient's body on the top plate, the image quality of the X-ray receiver becomes clear and the radiation dose rate in the space such as the examination room is reduced. a table with The net of the table described in claim 1,
A wire composed of a single element or a compound of an element having an atomic number of 14 or less that hardly absorbs X-rays is arranged crosswise or knitted by knitting or the like,
A table characterized by being a structure in which wires are arranged in a grid pattern at intervals of 10 cm or less
The net of the table described in claim 2 ,
A wire composed of a single element or a compound of an element having an atomic number of 14 or less that hardly absorbs X-rays is arranged crosswise or knitted by knitting or the like,
A table characterized by being a structure in which wires are arranged in a grid pattern at intervals of 10 cm or less
The wire constituting the net of the table according to claim 5 is
composed of an element or compound of an element with an atomic number of 14 or less that hardly absorbs X-rays,
A table having a diameter of 2 millimeters or more and a tensile strength of 50 megapascals or more
The wire constituting the net of the table according to claim 6 is
A table comprising a single element or compound of an element having an atomic number of 14 or less that hardly absorbs X-rays, having a diameter of 2 millimeters or more, and having a tensile strength of 50 megapascals or more.
In the net of the table according to claim 1, the net of the table is a structure in which wires are arranged in a grid pattern, and the structure is a combination of a wire or net and a rectangular plate-like frame that supports the weight of the patient's body. A table characterized by being a hollow cut plate-shaped structure or a molded product that integrates these In the net of the table according to claim 2, the net of the table is a structure in which wire rods are arranged in a grid pattern, and the structure is a combination of a wire rod or a net and a rectangular plate-like frame that supports the weight of the patient's body. A table characterized by being a hollow cut plate-shaped structure or a molded product that integrates these The structure in which the wires of the table according to claim 9 or 10 are arranged in a lattice,
It can be stored without surplus space in the through cutout in the center of the axis line of the top plate in the irradiation field,
By having a member that adjusts the height to be flush with the notch,
A table characterized by being a mesh permeable plate unit in which the mesh surface of the steps of the top plate can be freely fitted and removed. Part or all of the mesh transmission plate unit of the table according to claim 11 ,
Prepare an absorption plate, which is a solid cut flat plate having the same external dimensions and shape as the mesh transmission plate unit,
By replacing it with the mesh transmission plate unit and installing it,
A table characterized by being able to set and adjust the axial opening dimension of the irradiation field to the maximum width required for medical purposes.
The mesh transmission plate unit of the table according to claim 11 ,
Both ends in the vertical direction of the axis of the surface of one mesh transmission plate unit on the upper surface of the top plate are covered inward by two solid cut plate spacers from both end faces,
By changing the dimension of the width in the direction perpendicular to the axis of the mesh surface exposed without being covered with the spacer,
A table characterized by being able to adjust the width in the direction perpendicular to the axis of the irradiation field to the width required for medical purposes.
In the opening and closing plate of the table according to claim 3 or 4,
A step of the bottom plate is provided at the bottom of the step of the top plate,
arranging one or more opening and closing plates that open and close with a hinge mechanism or slide mechanism on the stage of the bottom plate,
By opening one or more opening/closing plates and allowing primary X-rays to enter,
A table characterized by the ability to change the position of the irradiation field required for medical purposes In the top plate of the table according to claim 1, claim 2, claim 3 or claim 4 ,
Surface materials exposed to X-rays outside the field are:
By changing the surface material according to the type or energy of the irradiated X-rays,
A table characterized by reducing the generation of scattered X-rays from the table In the top plate of the table according to claim 15 ,
A low-reflection material is placed on the material of the downward surface irradiated with primary X-rays and its scattered radiation,
and/or, a table characterized in that a composite absorbing material is placed on the material of the surface facing upwards onto which scattered X-rays from the patient's body are irradiated. The material constituting the absorbing plate of the table according to claim 12 is
A composite absorbing material is disposed on the surface material of the upper surface irradiated with scattered X-rays from the patient's body ,
and/or, a table characterized in that a low-reflection material is placed on the surface material of the lower surface irradiated with primary X-rays and its scattered rays.
The material constituting the spacer of the table according to claim 13 is
A composite absorbing material is disposed on the surface material of the upper surface irradiated with scattered X-rays from the patient's body,
and/or, a table characterized in that a low-reflection material is placed on the surface material of the lower surface irradiated with primary X-rays and its scattered rays.
In the opening/closing plate and/or the diaphragm plate of the table according to claim 4 ,
A low-reflection material is placed on the material of the downward surface irradiated with primary X-rays and its scattered radiation,
and/or, a table characterized in that a composite absorbing material is placed on the material of the surface facing upwards onto which scattered X-rays from the patient's body are irradiated. In the top plate of the table according to claim 16 ,
A table characterized by placing a composite absorbing material at a site shielded by the patient's body and not exposed to primary X-rays but irradiated with scattered X-rays. In the slide table of the table according to claim 3 or claim 4 ,
Disposing a pair of diaphragm plates, which are solid cut flat plates, on the hollow through surface of the slide table,
By axially moving one or both of the diaphragm plates,
A table characterized by the ability to adjust the aperture size of the irradiation field in the axial direction required for medical purposes even during surgery In the opening and closing plate installed at the bottom of the table according to claim 3 ,
The opening and closing plates are a pair of two solid square-cut flat plates,
By opening at an arbitrary opening angle in the direction perpendicular to the axis with a hinge mechanism,
A table characterized by being able to adjust the aperture size of the irradiation field in the vertical direction and the axis line required for medical purposes even during surgery. In the table according to claim 4,
On the surface of the slide table in the intermediate stage on which scattered X-rays are incident ,
By providing a slide absorbing plate on which a composite absorbing material is arranged ,
A table characterized by reducing scattered X-rays generated in parts other than the irradiation field The material for the net of the table according to claim 9 or 10 is
A table characterized in that it is carbon fiber reinforced plastic, glass fiber reinforced plastic, metallic aluminum or metallic magnesium The material for the structure in which the wires of the net of the table according to claim 11 are arranged in a lattice ,
A table characterized in that it is carbon fiber reinforced plastic, glass fiber reinforced plastic, metallic aluminum or metallic magnesium The material of the upper surface of the table irradiated with scattered X-rays according to claim 3 or claim 4 is
A table characterized by using a low-reflection material The material of the lower surface of the table according to claim 3 or 4, which is irradiated with primary X-rays,
Table characterized by composite absorbent material The material constituting the top plate of the table according to claim 16 is
The low-reflectance material is placed on the surface irradiated with primary X-rays from the X-ray source or its scattered rays, and is composed of an element or compound with an atomic number of 20 or more, and has a linear attenuation coefficient of 10 (1 / cm) or more,
The composite absorption material is placed on the surface irradiated with scattered X-rays from the patient's body on which it is placed, and the first layer is a low reflection attenuation layer, and the second and subsequent layers are a multi-layer absorption consisting of a pair of a diffusion absorber and an electron absorber. A table characterized by being a material in which three or more layers are adhered to each other and stacked in multiple layers.
The material constituting the absorbing plate of the table according to claim 17 is
The low-reflection material is placed on the surface irradiated with primary X-rays from the X-ray source or its scattered rays and is composed of an element or compound of an element having an atomic number of 20 or more, and has a linear attenuation coefficient of 10 (1 / cm) or more,
The composite absorption material is placed on the surface irradiated with scattered X-rays from the patient's body on which it is placed, and the first layer is a low reflection attenuation layer, and the second and subsequent layers are a multi-layer absorption consisting of a pair of a diffusion absorber and an electron absorber. A table characterized by being a material in which three or more layers are adhered to each other and stacked in multiple layers.
The material constituting the spacer of the table according to claim 18 is
The low-reflection material is placed on the surface irradiated with primary X-rays from the X-ray source or its scattered rays and is composed of an element or compound of an element having an atomic number of 20 or more, and has a linear attenuation coefficient of 10 (1 / cm) or more,
The composite absorption material is placed on the surface irradiated with scattered X-rays from the patient's body on which it is placed, and the first layer is a low reflection attenuation layer, and the second and subsequent layers are a multi-layer absorption consisting of a pair of a diffusion absorber and an electron absorber. A table characterized by being a material in which three or more layers are adhered to each other and stacked in multiple layers.
The material constituting the opening and closing plate and/or the diaphragm plate of the table according to claim 19 is
The low-reflection material is placed on the surface irradiated with primary X-rays from the X-ray source or its scattered rays and is composed of an element or compound of an element having an atomic number of 20 or more, and has a linear attenuation coefficient of 10 (1 / cm) or more,
The composite absorption material is placed on the surface irradiated with scattered X-rays from the patient's body on which it is placed, and the first layer is a low reflection attenuation layer, and the second and subsequent layers are a multi-layer absorption consisting of a pair of a diffusion absorber and an electron absorber. A table characterized by being a material in which three or more layers are adhered to each other and stacked in multiple layers.
The composite absorbent material of the table top according to claim 20 ,
The material of the surface irradiated with scattered X-rays from the patient's body on which it is placed is
By arranging a composite absorption material in which three or more layers of multilayer absorption layers, the first layer being a low reflection attenuation layer and the second layer or less consisting of a pair of a diffusion absorber and an electron absorber, are stacked in multiple layers in close contact,
A table characterized by reducing rescattering of X-rays by attenuating and absorbing scattered X-rays.
The composite absorbent material of the slide absorbent plate of the table according to claim 23 ,
The material of the surface irradiated with scattered X-rays from the patient's body on which it is placed is
By arranging a composite absorption material in which three or more layers of multilayer absorption layers, the first layer being a low reflection attenuation layer and the second layer or less consisting of a pair of a diffusion absorber and an electron absorber, are stacked in multiple layers in close contact,
A table characterized by reducing rescattering of X-rays by attenuating and absorbing scattered X-rays.
On a table on which a patient's body is placed in a medical X-ray transmission device,
At the site of the irradiation field where the primary X-rays are irradiated,
A thin sheet composed of a single element or a compound of an element with an atomic number of 14 or less is placed on the stage of the top plate, and X-rays are transmitted through the thin plate sheet, thereby suppressing the absorption and scattering of X-rays by the top plate. a table characterized by On the table on which the patient's body is placed in a medical undertube type X-ray transmission device,
Provide a bottom plate and/or an intermediate step at the bottom of the step of the top plate,
At the site of the field where the primary X-rays are irradiated, the X-rays
In the bottom plate and/or in the middle step, notches are provided to allow the hollow free space to pass through,
At the stage of the top plate, a thin sheet composed of an element or compound of an element with an atomic number of 14 or less is transmitted.
A table characterized by suppressing absorption and scattering of X-rays by the table The thin sheet of the table according to claim 34 or 35 ,
A table characterized in that the member installed in the irradiation field is a strip-shaped film or a flat board
The thin sheet of the table according to claim 34 or 35 ,
The weight of the patient's body placed on top is supported by the tensile strength of the thin sheet itself, and the reaction force is supported by a rectangular hollow strength member separately prepared. A table characterized by being able to be made smaller
The thin plate sheet of the table according to claim 34 or 35 ,
A table characterized by using a material with a thickness of 0.5 mm or less and a tensile strength of 100 MPa or more
The thin sheet of the table according to claim 34 or 35 ,
A table characterized in that the material is carbon fiber reinforced plastic or glass fiber reinforced plastic The structure for arranging the thin sheet of the table according to claim 34 or 35 ,
A table characterized by being a hollow cut plate-shaped structure combining rectangular plate-shaped frames that support the weight of the patient's body, or a molded product that integrates these. The structure for arranging the thin plate sheet of the table according to claim 40 ,
It can be stored without surplus space in the through cutout in the center of the axis line of the top plate in the irradiation field,
By having a member that adjusts the height to be flush with the notch,
A table characterized by being a sheet transparent plate unit in which the thin plate sheet surface of the stage of the top plate can be freely fitted and removed.