JP2005195643A - Radiographic image photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable radiographic image photographing device made thin and light in weight while satisfying a withstand load specification. <P>SOLUTION: The radiographic image photographing device is an electronic cassette 10 constituted of a radiation detecting panel 16 for detecting radiation transmitted through a subject, a base 15 for mounting and supporting the panel 16, and a housing 11 in which these are included. A plurality of supporting members 14 supporting the base 15 are arranged on the lower surface 15b side of the base 15 opposed to the upper surface 15a on which the panel 16 is mounted between the lower housing 11a and the base 15, and the base 15 is constituted so that a gap H<SB>a</SB>between the lower surface 15b of the base 15 and an electronic part 18a arranged in the lower housing 11a satisfies a relation δ<SB>a</SB><H<SB>a</SB>when it is assumed that the deflection of the base 15 in the withstand load specification of the radiographic image photographing device is δ<SB>a</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiographic imaging apparatus made of a lightweight and thin electronic cassette, for example.

  2. Description of the Related Art Conventionally, a device for obtaining a radiographic image of an object by irradiating the object with radiation and detecting the intensity distribution of the radiation transmitted through the object has been widely used in industrial nondestructive inspection and medical diagnosis. It's being used. As a general method for such photographing, a film / screen method for radiation is known.

  This is a method of photographing a combination of a photosensitive film and a phosphor sensitive to radiation. A sheet of rare earth phosphor that emits light when irradiated with radiation is adhered to both sides of the photosensitive film. The radiation that has passed through the subject is converted into visible light by a phosphor, captured by the photosensitive film, and then visualized by developing the latent image formed on the photosensitive film by chemical processing. be able to.

  On the other hand, with recent advances in digital technology, there is a need for a method of obtaining a high-quality radiographic image by converting a radiographic image into an electrical signal, performing image processing on the electrical signal, and displaying it on a CRT or the like as a visible image. It is coming. As a method for converting such a radiation image into an electrical signal, for example, as disclosed in Patent Documents 1 and 2, a radiation transmission image is temporarily stored as a latent image in a phosphor, and then a laser beam or the like is used. A radiation image recording / reproducing system that photoelectrically reads out a latent image and outputs it as a visible image by irradiating with excitation light has been proposed.

  With the progress of semiconductor process technology, an apparatus for taking a radiographic image using a semiconductor sensor has been developed. These systems have a very wide dynamic range compared to conventional radiographic systems using photosensitive films, and have the practical advantage of being able to obtain radiographic images that are not affected by fluctuations in radiation exposure. Have. At the same time, unlike the conventional photosensitive film system, there is an advantage that chemical processing is unnecessary and an output image can be obtained immediately.

JP-A-55-12429 JP-A-56-11395

  Conventionally, in this type of radiographic imaging apparatus, rigidity is generally more important than the weight of the apparatus itself and the dimensions in the thickness direction. However, in recent years, a portable imaging device, a so-called electronic cassette, has been required in order to enable imaging of a wide range of parts more quickly.

  For an operator such as a radiologist, it is desirable that the electronic cassette be lighter in consideration of the operability of the work of placing and transporting the electronic cassette at a predetermined position. Also, when inserting an electronic cassette between the subject lying on the bed and the bed, if the size in the thickness direction is large, the subject will be painful, so that it should be as thin as possible. It is rare.

  However, when it is light and thin, there is a problem that the mechanical strength is insufficient. Moreover, in the Example described in Patent Document 3, the mechanical structure related to the strength resistance when the subject is placed on the electronic cassette is not clearly described. Actually, it cannot be put into practical use unless the mechanical strength is improved in order to protect the semiconductor sensor, and simply strengthening is contrary to the purpose of reducing the weight and thickness.

Japanese Patent No. 38227

  An object of the present invention is to provide a radiographic imaging apparatus that solves the above-described problems, reduces the thickness and weight of the imaging unit itself, and improves operability and portability during installation.

In order to achieve the above object, a radiographic image capturing apparatus according to the present invention transmits a radiation emitted from a radiation generating unit to a subject, and the radiation image capturing device that detects a radiation distribution transmitted through the subject transmits the subject. A radiation detection panel having a detection surface on which a photoelectric conversion element for detecting radiation is arranged, a plate-like base for supporting the detection panel, an electric board placed behind the base, and a housing containing them A plurality of support members that are joined to the housing on the second surface side opposite to the first surface on which the detection panel is mounted, clearance H _a between the mounting component and the base of the second surface on the body, when the deflection of the base in the load-bearing specifications and δ _a, δ _a <satisfying the relationship H _a It is characterized by.

  According to the radiographic imaging device of the present invention, the amount of bending when a static load is applied to the base supporting the radiation detection panel is made smaller than the gap between the mounted component of the electric circuit and the inner wall of the housing. By designing, the reliability of the device can be ensured even when the casing is thin and light.

  In addition, the physical burden on the operator and the subject is reduced, the operability of the operator is improved, and the subject's discomfort can be suppressed.

  Furthermore, it is possible to perform imaging of a wide range of parts more quickly and at the same time, it is possible to construct an inexpensive system in which one imaging apparatus can be installed on a plurality of imaging platforms.

  The present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a conceptual diagram of a general system using such a radiographic image capturing apparatus. The radiographic image capturing apparatus 1 includes a radiation detecting means 2. A radiation generating device 3 is provided above the radiographic image capturing device 1, and the subject S is irradiated with radiation from the radiation generating device 3, and the radiation transmitted through the subject S is arranged in a two-dimensional lattice. Detection is performed by radiation detection means 2 comprising a conversion element. The image signal detected by the radiation detection means 2 is subjected to digital image processing in the image processing means 4, and a radiation image of the subject S is displayed on the monitor 5.

  2 is a side sectional view of the electronic cassette 10 as the radiographic image capturing apparatus 1 according to the first embodiment, FIG. 3 is a bottom view with a part cut away, and the upper portion of the lower housing 11a is X-ray transparent. Are sealed by an upper casing 11b made of CFRP having excellent strength, and screw mounting holes 12 are provided at several locations on the bottom surface of the lower casing 11a. A screw 13 is inserted into the screw mounting hole 12 and a support member 14 is fixed in a columnar shape. On the support member 14, a lightweight and high-strength aluminum alloy or magnesium is used to protect it from vibration or impact during transportation. A base 15 made of a structure having high rigidity such as an alloy is provided, and an upper surface 15a of the base 15 is a flat surface. The panel 16 is fixed.

  The radiation image detection panel 16 includes a phosphor 16a that converts the radiation irradiated from the radiation generator 3 into visible light, a photoelectric conversion element 16b that is arranged in a grid pattern that converts the visible light into an electric signal, and a substrate 16c. It is made up. As the substrate 16c, a glass substrate is often used because it does not have a chemical action with a semiconductor element, withstands the temperature of the semiconductor formation process, and requires dimensional stability. On such a glass substrate 16c, a photoelectric conversion element 16b formed in a two-dimensional array by a semiconductor process and a phosphor 16a obtained by applying a phosphor of a metal compound to a resin plate are stacked.

  On the lower surface 15b side of the base 15, there is a circuit board 18 on which an electronic component 18a for processing photoelectrically converted electrical signals, controlling signal readout from the radiation detection panel 16, and transferring image data is mounted. Is disposed on the lower housing 11a. The photoelectric conversion element 16 b is connected to the circuit board 18 via a plurality of flexible circuit boards 17 that pass through the side of the base 15.

  In addition, a buffer material 19 is disposed between the upper housing 11 b and the radiation detection panel 16.

  The upper housing 11b is required to have as high a radiation transmittance as possible while ensuring a high S / N without reducing the X-ray dose to be detected. However, on the other hand, since the radiation detection panel 16 is mainly composed of a glass plate, a structure for supporting it in strength is necessary, and a casing 11 for sealing is provided so as not to cause image quality deterioration due to external light. In addition, when the subject S gets on the upper housing 11b, a sufficient load resistance specification for protecting the radiation detection panel 16 is required.

  Therefore, it is required to improve rigidity by increasing the thickness of the casing 11 itself or to secure a distance between the radiation detection panel 16 and the upper casing 11b. Considering these conditions, in order to support the load only by the upper casing 11b and prevent the radiation detection panel 16 from being stressed, there is a problem that the transmittance is reduced and the outer shape of the electronic cassette 10 is increased. Therefore, it is difficult to realize, and a load-bearing support structure that can endure even when a load is applied to the radiation detection panel 16 itself is required.

  Therefore, the above-described cushioning material 19 is interposed between the upper housing 11b and the radiation detection panel 16, and the cushioning material 19 is locally applied to the radiation detection panel 16 even if the upper housing 11b is bent under a load. It suppresses the generation of natural stress and plays the role of dispersing stress.

  The upper surface 15a on which the radiation detection panel 16 is mounted is a flat surface so that the base 15 does not bear a load only by the radiation detection panel 16. The base 15 is designed so that the bending stress applied to the radiation detection panel 16 is within an allowable range even when a load is applied from above. That is, as shown in FIG. 3, a plurality of support members 14 are two-dimensionally arranged on the base 15 in a lattice shape, which contributes to supporting a load from above.

  As described above, the electronic cassette 10 is as light as possible so that it can be easily handled by the operator, and has a thickness that does not cause pain when inserted between the lying subject and the bed. It is necessary. It is the thickness t of the base 15 and the height H of the support member 14 that greatly affects the thickness of the electronic cassette 10. Further, the strength is designed by the thickness t of the base 15 and the distance L between the support members 14 so that the bending stress applied to the radiation detection panel 16 is within an allowable range even when a load is applied from above, and the weight is reduced. ing.

On the other hand, the height H of the support member 14 is determined by the height H _p including the electronic component 18 a of the circuit board 18 disposed below the base 15 and the gap H _a between the electronic component 18 a and the base 15. Is done. In this case, load is applied from above the flexing base 15, the gap H _a gradually narrowed. In a standard specification, the base 15 is intensity designed not eliminated the gap H _a, even when took stronger load, before reaching the deflection radiation detection panel 16 is damaged, the electronic component 18a clearance H _a to receive the load contact is ensured.

Since the radiation detection panel 16 is expensive and the circuit board 18 is replaceable, it is important to prevent the radiation detection panel 16 from being damaged. The entire electronic cassette 10 is secured by ensuring _a minimum gap Ha. It is possible to reduce the thickness. Incidentally, to be placed the circuit board 18 to the lower surface 15b side of the base 15, the gap H _a is equal to the height H of the base 15 and the lower housing 11a.

In other words, when the bending of the base 15 in the load-bearing specification is δ _a and the breaking deflection of the glass substrate 16 c is δ _g , the base is set so as to satisfy the relationship of δ _a <H _a <δ _g. A thickness t [mm] of 15 and an interval L [mm] between the support members 14 are determined.

Calculation of the deflection of a flat plate subjected to a vertical load is as follows. The basic equation of deflection δ due to elastic bending of a flat plate is as follows, where p (x, y) is a load distribution function, ν is a Poisson's ratio, and E is a longitudinal elastic modulus [kgf / mm ² ]. It becomes.
^{∂ 4 · δ / ∂x 4 +} 2∂ 4 δ / (∂x 2 · ∂y 2) + ∂ 4 · δ / ∂y 4
= P (x, y) / D (1)
D = E · t ³ / {12 (1-ν ² )} (2)

The bending δ _a of the base 15 assumes that the base 15 is a uniform plate and assumes that the subject S having a weight P [kgf] is placed in the center between the supports, and the base 15 has a longitudinal elastic modulus E. When the material is adopted, the deflection δ _a [mm] is obtained by the following equation (3).
δ _a = (A · P / E) (L ² / t ³ ) (3)

  A is the maximum deflection coefficient (no unit), and varies depending on the shape supporting the base 15, the constraint condition of the base 15, the load position, and the like. In the present embodiment, the area to which the load is applied is assumed to have a size corresponding to a ridge and is 40 [mm] in diameter, so A = 0.46.

  The deflection coefficient A slightly changes depending on the range of the load area. Assuming a diameter of 20 to 80 mm, the deflection coefficient A may be estimated around ± 20%. Therefore, A is set in the range of 0.37 to 0.55.

When lightweight and high specific strength magnesium is used as the material of the base 15, the longitudinal elastic modulus E is about 4600 [kgf / mm ² ]. Here, if C _L that defines the relationship of load displacement is determined as a specification condition and an allowable deflection δ _L is set, Equation (4) for selecting the thickness t and the support interval L of the base 15 is obtained.
C _L = δ _L / P ≧ δ _a / P = (A / E) (L ² / t ³ ) (4)

The weight P of the object S is set to 100 [kgf], when the condition a relationship load displacement to 1 the allowable deflection δ _L [mm], C _L is 0.01, and the (3), (4) (5) is obtained. What is necessary is just to select the thickness t and the support space | interval L of the base 15 in the area | region of the upper side of the graph shown by FIG. 4 so that this Formula (5) may be satisfied. In FIG. 4, A is 0.46, but 0.37 has a wider design solution range. As a result, the strength margin decreases, so the optimal solution is in a trade-off relationship with weight reduction.
100 ≧ L ² / t ³ (5)

In this case, even when the weight P is 200 [kgf], when the deflection δ is 2 [mm] or less and the thickness t of the base 15 is set to about 3 mm, in the region where the support interval L is 50 [mm] or less. The base 15 does not contact the electronic component 18a. Therefore, it is set the gap H _a to the extent [2 mm], in weight P = 100 deflected state with [kgf] is applied for the standard specification, which can ensure the gap H _a, the normal shooting Is possible.

Furthermore, even if the flexure takes abnormal load [delta] _a is 2 [mm], since it is possible to suppress deflection by the electronic component 18a, it is possible to prevent the breakage of the radiation detection panel 16 itself.

  Further, in order to reduce the weight, it is necessary to reduce the mass of the base 15 as much as possible. Generally, the weight that can be carried by the operator is about 5 [kg], and the base 15 needs to be configured with at least 2 [kg]. In the case of the radiation detection panel 16 having a half-cut size (430 [mm] × 353 [mm]), the base 15 needs to have a flat area of at least 440 [mm] × 363 [mm]. Then, the thickness t satisfying 2 [kg] or less is 7 [mm].

  On the other hand, if the support interval L of the support member 14 is reduced, the thickness t of the base 15 can be reduced and the weight can be reduced. However, the interval at which the circuit board 18 is disposed is reduced. Although it is possible to provide a through hole in the circuit board 18 and allow the support member 14 to pass therethrough, there are disadvantages in cost and circuit pattern design. Therefore, it is necessary to limit the number of support members 14 and to optimally design the thickness t satisfying a weight of 2 [kg] or less within a range of 7 [mm] or less.

  The following Table 1 shows the relationship between the spacing L of the support members 14 when the support members 14 are two-dimensionally arranged in a lattice shape and the number N of inner arrangements excluding the outermost arrangement of the support members 14. . Assuming that 30 is the limit of the number of support members 14 that can be configured, it is considered appropriate to set the distance L to 70 [mm] or more.

Table 1
L [mm] 40 50 60 70 80 90 100 110 120 150 200 300 400
N [pieces] 99 56 42 30 20 16 12 12 9 4 2 1 0

  Therefore, it is desirable to select the number of the support members 14 in a region satisfying t ≦ 7 and L ≧ 70 mm.

In this embodiment, a magnesium alloy is used for the base 15, but in the case of an aluminum alloy, the longitudinal elastic modulus E is about 7300 [kgf / mm ² ], which is 1.6 times larger. The left side is 160, and the same configuration can be achieved by satisfying the thickness of 4.6 [mm] or less as the specific gravity increases.

  FIG. 5 is a side sectional view of the electronic cassette 10 according to the second embodiment. In addition, the same code | symbol is attached | subjected to the member same as Example 1. FIG.

  According to the equation (5), the distance L between the support members 14 and the thickness t of the base 15 influence the deflection by a power, and there are significant restrictions on changing each independently. Rather, there is a possibility of further weight reduction by changing the material or shape that determines the deflection coefficient A.

  As described above, when an aluminum alloy is used as the material, strength can be obtained. However, since the specific gravity is 1.5 times, it cannot be easily reduced in weight. Therefore, as shown in FIG. 5, it is possible to reduce the weight by adopting a material having a gap instead of a homogeneous material as the base 21, and changing the filling rate.

In this case, considering that the strength is lower than that of the homogeneous plate material, the specification of the load displacement when the apparent thickness t _b is assumed to be a homogeneous plate material having a filling rate of 100% is (4) it is desirable to satisfy set from the equation: C _L to be 1 / M (M = 1 or more) to (6). If this formula (6) is arranged, formula (7) is obtained. Note that M is an index representing a decrease in strength of a sample that is not homogeneous.

For example, in consideration of a decrease in strength when a gap is provided in the base 21 of FIG. 5, the deflection per unit load when setting it as a homogeneous material with a filling rate of 100% is set to 1 / M. Employing the condition for obtaining the formula (5) and taking the case of M = 2 as an example, the formula (8) is obtained. However, the deflection coefficient A = 0.46.
C _L / M ≧ δ _a / P = (A / E) (L ² / t _b ³ ) (6)
_{(1 / M) (δ L} E / A · P) ≧ L 2 / t b 3 ··· (7)
50 ≧ L ² / t _b ³ (8)

  FIG. 6 shows a region based on the equation (8). In addition, the dotted line has shown the case of the homogeneous board | plate material shown in FIG. 4 for the comparison.

Then, while maintaining the apparent thickness t _b , weight reduction is promoted by reducing the filling rate, and if the design allows the bending δ _b to be equal to or less than M times the bending δ _a in this case. , Equivalent or higher rigidity can be obtained.

  If formula (4) is also arranged, it can be expressed together as a case where the filling rate is 100% with M = 1 in formula (7).

Even when a material having an evenly distributed foam structure is used, it is desirable that the surface be a homogeneous plate material in order to avoid stress concentration. Accordingly, homogeneous plate 21a on the front and back surfaces of the Example 2, the base 21, 21b are fixed so as to cover a gap 21c is an intermediate layer, overall reduces the filling rate with respect to the plate thickness t _b in It becomes the composition.

  FIG. 7 is a side sectional view of the electronic cassette 10 according to the third embodiment, and a bottom view in which a part of FIG. 8 is cut away. In addition, the same code | symbol is attached | subjected to the member same as Example 1. FIG.

A plurality of recesses 31c having openings are formed on the lower surface side of the base 31, and a flat plate 31d is fixed so as to cover these recesses 31c. Clearance H _a in this case is a gap between the electronic component 18a of the lower surface 31b and the circuit board 18 of the plate 31d.

  As shown in FIG. 8, the concave portion 31c is arranged in a shape in which X-shaped ribs are provided for each predetermined section partitioned by a one-dot chain line. A support member 14 is attached. The flat plate 31 d is fixed by fastening with the support member 14 and bonding to the base 31.

  By attaching such a flat plate 31d as a reinforcing material as a part of the base 31, the base 31 acts so as to suppress elongation generated by bending, so that load resistance can be improved. Further, as the material of the flat plate 31d, a lightweight material having a high elastic coefficient is effective, and fiber reinforced plastic, fiber reinforced metal, aluminum alloy, or the like is suitable.

  Thus, by forming the thick portion constituting the base 31 on the upper surface 31a side on which the radiation detection panel 16 is mounted, it is difficult to cause deformation even with respect to a local load. It can have the effect as a shielding material.

  Further, since the flat plate 31d is attached to the surface facing the upper surface 31a, not only adhesion but also fastening with screws can be used together, which is more effective in terms of reinforcement. Further, since the opening of the base 31 is a simple recess 31c in the plate thickness direction, it can be easily and inexpensively manufactured by an existing manufacturing method such as die casting.

Similarly to Example 1, even when the magnesium alloy is selected from the regions satisfying t _b ≦ 7 and L ≧ 70 mm, the region shown in FIG. 6 exists and can be reduced in weight. The combination of square and slanted ribs at the four corners of the support point as shown in FIG. 8 achieves a weight reduction of about 40% compared to δ _b / δ ≦ 2 and a filling rate of 100%. it can.

It is a conceptual diagram of a general system. FIG. 3 is a cross-sectional view seen from the side of Example 1. It is the bottom view which notched a part. 6 is a graph showing the relationship between the thickness of the base and the spacing between support members in Example 1. FIG. It is sectional drawing seen from the side of Example 2. FIG. It is a graph showing the relationship between the thickness of the base of Example 2, and a support member space | interval. FIG. 6 is a cross-sectional view as viewed from the side of Example 3. It is the bottom view which notched a part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiographic imaging apparatus 2 Radiation detection means 3 Radiation generation apparatus 4 Image processing means 5 Monitor 10 Electronic cassette 11a Lower housing 11b Upper housing 13 Screw 14 Support member 15, 21, 31 Base 16 Radiation detection panel 17 Flexible circuit board 18 Circuit board 18a Electronic component 19 Buffer material 21a, 21b Plate material 31c Recessed portion 31d Flat plate

Claims (9)

A radiation detection panel having a detection surface on which a photoelectric conversion element for detecting radiation transmitted through a subject is disposed in a radiographic imaging apparatus that irradiates a subject with radiation emitted from radiation generation means and detects a radiation distribution transmitted through the subject; And an imaging unit comprising a plate-like base for supporting the detection panel, an electric board disposed behind the base, and a housing containing them, and the base mounts the detection panel. A plurality of support members to be joined to the housing on the second surface side opposite to the first surface, and a gap H between the mounting component on the housing and the second surface of the base _a is, load deflection said base with heavy specification when the [delta] _a, [delta] _a <radiographic imaging apparatus that satisfies the relationship of H _a. When the radiation detection panel has a the base of the deflection [delta] _g at the time of breaking, the gap H _a is claimed in claim 1, characterized by satisfying the relation δ _a <H _a <δ _g Radiographic imaging device. When the support member is made of a material having a longitudinal elastic modulus E and a filling factor of 100%, the deflection of the base is δ, the deflection when the filling factor is 100% or less is δ _b , and the allowable deflection at the load P is When δ _L and the maximum deflection coefficient are A, the interval L between the support members and the apparent plate thickness t _b of the support members satisfy the following expression with respect to one or more coefficient M that represents a decrease in strength. The radiographic image capturing apparatus according to claim 1, wherein:
L ² / t _b ³ ≦ (1 / M) (δ _L · E) / (A · P) (A = 0.37)
δ / δ _b ≦ M   4. The radiographic imaging apparatus according to claim 3, wherein when the base is made of a magnesium alloy, the distance L satisfies L ≧ 70 mm and the basic thickness t of the plate satisfies t ≦ 7 mm.   4. The radiographic imaging apparatus according to claim 3, wherein when the base is made of an aluminum alloy, the distance L satisfies L ≧ 70 mm and the basic plate thickness t of the plate satisfies t ≦ 4.6 mm.   The radiographic imaging apparatus according to claim 1, wherein the base is made of a material having a foam structure.   The radiation according to any one of claims 1 to 3, wherein the base includes a plurality of recesses having openings on the second surface side, and the recesses are covered with a flat plate. Image shooting device.   The radiographic imaging apparatus according to claim 7, wherein the flat plate is made of fiber reinforced plastic, fiber reinforced metal, or aluminum alloy.   The radiographic imaging apparatus according to claim 1, wherein the imaging unit is a portable electronic cassette.

Images