JP4584012B2 - Human transport vehicle - Google Patents

Description

  The present invention relates to a human body transportation vehicle, and more particularly to a mobile vehicle for safely moving a patient who has injected a radiation source between a PET apparatus loaded vehicle and a medical facility. In this specification, PET refers to positron emission tomography.

  Conventionally, in order to increase the operating rate of expensive medical diagnostic equipment such as MRI (magnetic resonance diagnostic) equipment, such equipment can be mounted on a trailer equipped with an examination room so that it can be visited in various places (mobileization). (Patent Document 1).

However, since MRI only provides knowledge of the shape of an organ, in recent years, PET examinations that contribute to early detection of cancer and the like by providing physiological function information such as local blood flow in the body and glucose consumption are attracting attention. In addition, since this inspection apparatus is also quite expensive, it is desired to make it mobile. Here, the principle of the PET examination will be briefly explained. A radiopharmaceutical such as F ¹⁸ -FDG (fluorodeoxyglucose) is injected into the body of the examinee, and the positron emitted from the medicine is annihilated with other electrons. Then, the annihilation photons (γ rays) are emitted. Since cancer cells consume 3 to 8 times as much glucose as normal cells, FDG is collected and appears in the PET image. In this method, there is a possibility that other examinees and medical workers may be exposed to radiation by gamma rays emitted from the patient's body, and in order to avoid this, it is a chair for the waiting room of the medical facility, The thing which provided the radiation shielding board in the side surface is proposed (patent document 2).
JP 2001-095780 A JP 2004-361288 A

    In Japan, there are strict regulations on the handling of radioactive substances, so if you are going to visit a hospital with a vehicle equipped with a PET device, you will be injected around the medical facility after injecting the radiopharmaceutical to the patient in the radiation control area of the medical facility. Although it is necessary to transfer the examinee to the parked vehicle equipped with the PET apparatus, a means for reliably blocking radiation emission from the body of the examinee during the transfer is necessary. For this purpose, for example, it is conceivable that the chair with the radiation shielding function of Patent Document 2 is a movable wheelchair and that the front surface of the chair is also covered with a radiation shielding plate. However, since metal with high specific gravity such as lead or iron is used as the radiation shielding material, the weight of the radiation shielding wheelchair becomes extremely large and difficult to move when attempting to completely block radiation. is there.

    Therefore, an object of the present invention is to provide a human transport vehicle that can be easily operated and moved while effectively preventing exposure of a caregiver or a passerby during the transfer of a medical examinee.

The first means is a transport vehicle for transporting the examinee P injecting a nuclear medical radiation source into the body,
The carriage 2 that囲成radiation shielding wall 24 around while have a pedestal 12 is provided,
A handle for operation by a caregiver N, which is spaced from the radiation shielding wall 24 at the rear of the operation arm 42 protruding from the rear side of the carriage at least to the rear of the carriage, and is shorter than the projection length of the operation arm. Part 46 is attached.

  “Nuclear medicine” includes the above-described PET examination, but the human body transportation vehicle of the present invention may also be used for SPECT (Single Photon Emission Tomography).

  “Car” is a structure in which a radiation shielding wall is erected from the periphery of a base frame (or substrate) provided with a plurality of wheels, and an appropriate location (for example, a side wall) of the radiation shielding wall is formed on a boarding / alighting door. be able to. In addition, it is desirable to provide a self-propelled drive unit in the cart. This drive unit can be formed by an electric motor, for example.

    It is desirable that the “pedestal” is formed in a chair shape to be described later by standing from a part (for example, the rear part) of the basic frame. However, since the examinee who is a sick person moves while lying down, the pedestal can be a bed type that is elongated in one direction (preferably in the front-rear direction). In this case, the base frame may be formed vertically corresponding to the pedestal and surrounded by a radiation shielding wall, and the entire carriage may be configured as a stretcher with a shielding wall.

    The “radiation shielding wall” stands preferably vertically from the periphery of the carriage so as to cover the entire circumference of the carriage. The height of the radiation shielding wall is set so that the radiation emitted from the body of the examinee is not directly exposed to the attendant who operates the handle portions before and after the carriage. The radiation shielding wall is preferably made of an opaque material having sufficient radiation shielding ability such as lead or iron.

    In addition to the function of the operation unit that the attendant guides the traveling direction of the transport vehicle, the “handle portion” is directly attached to the radiation shielding wall when the attendant or the like changes the direction of the human transport vehicle. It is to avoid touching. Since the transfer vehicle of the present invention is bulky and it is difficult to confirm the safety in front of the transfer vehicle from the rear of the transfer vehicle, it is desirable to provide a handle portion on both the front and rear sides of the transfer vehicle so that the attendant is accompanied by each. . When the pedestal is installed on the rear side of the carriage, the front handle portion is preferably near the front wall portion of the radiation shielding wall, and the rear handle portion is preferably located away from the rear wall portion of the radiation shielding wall. It can be installed equidistant from the pedestal. The front handle is between the front of the pair of left and right operation arms protruding forward from the front of the carriage, and the rear handle is the rear of the pair of left and right operation arms protruding rearward from the rear of the carriage. It is preferable to form it in the shape of a horizontal bar-like handrail erected between them, but instead, for example, it is formed at the front end of each front operation arm and the rear end of each rear operation arm. You can also.

    The second means includes the first means, and passes through the front or rear corresponding wall portions 24f, 24b of the radiation shielding wall 24 from the part of the body of the examinee who is placed on the pedestal 12 to the front or rear. The thicknesses of the corresponding wall portions 24f and 24b are determined according to the distance from a part of the body to the handle portions 46 and 48 so that the dose of radiation reaching the handle portions 46 and 48 becomes a prescribed amount or less.

    That is, in this means, the thickness of the front, rear and left and right side walls of this radiation shielding wall is constant for the amount of exposure of the attendees such as attendants, passersby, and facility personnel as described later. It is determined to be as follows. Specifically, in the case of a radiation shielding wall made of lead, the thickness of the rear wall portion is 5-8 mm forward when the distance from the examinee's body to the front and rear handle portions is about 1 m. The wall thickness should be about 5mm. In addition, when the distance between the passerby passing by the human body moving vehicle and the examinee is about 550 mm, it should be about 3 mm.

    In other words, the handle portion of the present invention becomes a warning sign indicating that there is a possibility of being exposed to radiation exceeding the reference value when the attendant approaches a place closer to the radiation shielding wall than the handle portion for a certain time. .

    In this means, the horizontal distance from the position of the pedestal (more specifically, part of the body of the patient sitting on the pedestal) to the handle is set as large as possible within the range that can be moved in the hospital corridor and elevator. The thickness of the corresponding wall portion of the radiation shielding wall may be determined so that the radiation exposure dose of the attendant at the handle portion does not reach the specified value according to the distance. The horizontal distance from the pedestal (or part of the body of the examinee sitting on the pedestal) to the handle is preferably about 1 m, and if this length is from the front handle to the rear handle Since it is about 2 m, the thickness of the radiation shielding wall can be suppressed to a reasonable range while enabling mounting on an elevator or the like and turning at the corner of the hallway. However, this horizontal distance can be changed as appropriate according to the size of the passage of a hospital or the like.

    The radiation exposure dose may be defined by a radiation dose per unit time, but may be defined by an integrated dose within a transfer time from a radiation management area such as a hospital to a vehicle equipped with a PET apparatus. This point will be further described later in the fourth means.

In addition, since F ¹⁸ FDG injected into the body of the examinee circulates in the body together with blood, the part of the examinee's body that is the starting point of the horizontal distance to the handle portion is the torso, more specifically the internal body. It is desirable to use the heart of the patient who collects the most blood. However, it is not necessarily limited to the torso or heart. For example, in the above-described stretcher type bed, it is possible to take the horizontal distance from the body part (head to foot) closest to the front and rear handle parts. .

The third means includes the second means, and the radiation shielding wall 24 is box-shaped, and is approached to the lower side of the rear wall portion 24b of the radiation shielding wall 24 so that the examinee P A chair-shaped pedestal 12 that can be seated is provided.

  In this means, the pedestal is made into a chair shape to make the trolley compact, and the distance from each part of the examinee's body seated on the chair to the handle part compared to the stretcher type trolley described above Is made small so that the calculation error of the radiation exposure dose based on a part of the body (for example, the trunk) becomes small.

  The chair-shaped base can be provided continuously with the rear wall portion of the radiation shielding wall, and the rear wall portion can be used as a backrest.

  The fourth means includes the third means, and uses the body part as the torso of the examinee P, and determines the dose of radiation reaching the front or rear handle parts 46, 48 from the torso, As an integrated dose that the attendant N can be exposed to at the positions of the front and rear handle portions 46 and 48 during the transfer time, the thicknesses of the front and rear corresponding wall portions 24f and 24b of the radiation shielding wall 24 are determined from this integrated dose. Further, the dose that can be exposed through the side wall portion 24s of the radiation shielding wall 24 by an encounter person who approaches the carriage 2 within an encounter time set shorter than the transfer time is less than a prescribed amount. The thickness of the side wall portion 24s is determined.

  In this measure, in front of the radiation shielding wall, the cumulative dose that can be exposed to the caretaker within the transport time by the transport vehicle and the encounter time when the encounter is close to the transport vehicle is below the reference value. Or it is comprised so that the thickness of a back corresponding | compatible wall part and a left-right side wall part may be defined. Here, the transfer time is assumed to be the transfer time from a radiation control area such as a hospital to a vehicle equipped with a PET device, and the encounter time is a corridor through which a human transport vehicle passes for those concerned in the facility. Time to be present in other places such as in a car or elevator for other work, time when a human transport vehicle is stored in a lift on a PET device-equipped vehicle, and time for other patients to rub against the transport vehicle Assumed. Of course, since these transfer times and encounter times are different in each case, in an actual calculation, the exposure dose may be calculated by setting standard transfer times and encounter times. This transfer time is set longer than at least the encounter time. More specifically, the transfer time is, for example, about 5 to 10 minutes, more preferably about 20 minutes, and the encounter time is, for example, about 30 seconds to 1 minute, more preferably about 2 minutes. Further, the prescribed amount of radiation allowed can be set to 4 μsV (sievert), for example.

  The fifth means includes any one of the first means to the fourth means, and further, auxiliary shielding that is inclined upward and inward at least at the upper end of the front wall or the rear wall of the radiation shielding wall 24 A plate 26 is attached.

  The “auxiliary shielding plate” is for preventing the attendant and the like from being exposed to radiation emitted upward from the body of the examinee. Of course, it is desirable to block the upper surface opening of the radiation shielding wall with a shielding plate such as a lead plate from the viewpoint of preventing radiation leakage, but in this case, the weight of the entire transport vehicle becomes excessively large and difficult to handle. Therefore, shielding is effectively performed with a small amount of shielding material by projecting the auxiliary shielding plate obliquely upward and inward from the upper end of the vertical radiation shielding wall.

  The auxiliary shielding plate may be attached to the upper end of the front or rear wall portion of the radiation shielding wall, and is preferably attached to the upper ends of the left and right side wall portions of the radiation shielding wall. The length of the auxiliary shielding plate is preferably about 100 mm, but may be about 50 mm. The projection angle of the auxiliary shielding plate from the upper end of the radiation shielding wall is preferably about 30 degrees with respect to the vertical direction.

  Further, the auxiliary shielding plate 26 may be a curved plate portion that curves inward and protrudes so as not to scatter the radiation emitted from below, so that the radiation emitted from the body of the examinee is auxiliary shielded. The inner surface of the plate 26 can be configured to reflect one or more times and return downward. The auxiliary shielding plate may be formed in an arc shape when viewed from the longitudinal direction (left and right directions in the front and rear auxiliary shielding plates), and may be formed in an arc shape (particularly, a quarter arc shape) with the inner surface of the tip portion being horizontal. desirable.

The invention according to the first means has the following effects.
○ Because the handle portions 46 and 48 are provided at the front and rear of the carriage 2 apart from the radiation shielding wall 24, the attendant P guiding the human transport vehicle in a hospital corridor or the like approaches carelessly or the radiation shielding wall You can prevent inadvertent touching.
○ Since the periphery of the pedestal for the patient is surrounded by a radiation shielding wall, the privacy of the patient and other patients who pass through the hospital is also protected.

  According to the invention relating to the second means, the thickness of the front and rear wall portions of the radiation shielding wall is set so that the amount of exposure at the positions of the handle portions 46, 48 is less than the prescribed amount. It is possible to prevent the attendant who operates this human transport vehicle from being exposed to radiation exceeding the prescribed amount, and to reduce the weight of the human transport vehicle while ensuring safety to the surroundings. .

  According to the invention relating to the third means, since the pedestal 12 is made into a chair shape, the entire trolley is compactly formed, and the variation in the distance from each part of the body of the examinee P sitting on the chair to the handle part is reduced. The amount of radiation exposure due to radiation can be predicted more accurately.

According to the invention relating to the fourth means, the following effects can be obtained.
○ Designed so that the radiation emitted from the torso of the examinee P is less than the prescribed amount, the radiation dose close to the dose actually exposed from the examinee P can be obtained accurately and easily.
○ The front and rear wall portions 24f and 24b of the radiation shielding wall 24 are based on the accumulated radiation dose within the transfer time of the caregiver N, and the left and right side wall portions 24s are based on the accumulated radiation dose within the encounter time of the passerby. Since it was determined based on the above, it is possible to ensure the necessary thickness for each part of the radiation shielding wall without waste.

  According to the fifth aspect of the invention, since the auxiliary shielding plate 26 inclined upward and inward from the upper end of the radiation shielding wall 24 is attached, radiation can be shielded more effectively with a small amount of radiation shielding material.

  1 to 5 show a human transport vehicle 1 according to an embodiment of the present invention.

  This human body transfer vehicle includes a carriage 2, a radiation shielding enclosure 22, and operation members 40F and 40B.

  The carriage 2 has front wheels 6 and rear wheels 8 attached to the front and rear of a rectangular base frame 4 as viewed from above, and a drive unit 10 for driving rear wheels is mounted on the rear part of the base frame 4. A chair-shaped pedestal 12 is attached to the rear side of the base frame 4 so as to cover the upper part of the base frame 4. Further, a stepping substrate 14 is stretched on the upper surface of the front portion of the base frame 4. Further, in the illustrated example, a pair of left and right front projecting plates 16 and 16 are projected from the front portion of the base frame, and one rear projecting plate 18 is projected from the rear portion of the base frame, so that the back surface of each front projecting plate is provided. A caster, which is the front wheel 6, is attached to the rear projecting plate 18, and a pair of left and right drive wheels are supported as the rear wheel 8 so that the left and right parts of the rear projecting plate 18 can be provided.

  As shown in FIG. 3, the enclosure 22 is configured to cover the entire periphery except for the upper side and the lower side of the examinee P seated on the pedestal 12 by the radiation shielding wall 24 and the auxiliary shielding plate 26. This enclosure is made of lead. The radiation shielding wall 24 is formed in a square cylinder shape that stands vertically from the upper surface of the base frame 4, and the rear wall portion 24 b of the radiation shielding wall is used as a backrest of the examinee P so as to be used as a backrest. It is formed continuously at the rear end. Further, an auxiliary shielding plate 26 is attached to the upper end portion of the radiation shielding wall 24. The auxiliary shielding plate 26 includes front and rear auxiliary shielding plates 26f and 26b protruding from the upper ends of the front and rear wall portions 24f and 24b of the radiation shielding wall in the front and rear direction, and left and right side wall portions of the radiation shielding wall. The side auxiliary shielding plates 26s and 26s that protrude from the upper ends of 24s and 24s inward in the left-right direction are formed so as not to cause a gap at each corner. A part of the side of the enclosure 22 is formed as a door 30 that can be opened and closed with respect to the other parts of the enclosure around the hinge 28. Reference numeral 32 denotes a handle attached to the door 30. Further, the auxiliary shielding plate 26 can be projected at an angle of about 30 to 60 degrees with respect to the vertical upper side.

  The thicknesses of the front and rear wall portions 24f and 24b of the radiation shielding wall 24 and the front auxiliary shielding plate 26 depend on the positions of the front and rear handle portions 48 and 46, and the side wall portion 24s of the radiation shielding wall. The thickness is determined so that the accumulated radiation dose during the transfer time or passage time does not reach the specified value depending on the distance from the passerby. A specific method of obtaining the thickness will be described in the examples.

  The operation members 40F and 40B are detachably attached to the front and rear sides of the carriage 2, respectively. As shown in FIG. 1, the rear operation member 40B has inverted L-shaped operation arms 42 and 42 that are erected from both the left and right upper surfaces of the rear projecting plate 24 and then bent rearward. A horizontal bar-like handle portion 46 is formed between the rear end portions of the pair of left and right operation arms. Similarly, the front operation portion 40F has inverted L-shaped operation arms 44, 44 that stand up from the front projecting plates 16, 16 and then bend forward, and the front ends of the pair of left and right operation arms. A horizontal bar-shaped handle portion 46 is formed between the portions. Both the handle portions 46 and 48 may be set to a height at which the human body transportation vehicle can be easily operated, for example, the height of the waist of the attendant N. The operation arms 42 and 44 are preferably formed so as to be detachable from the carriage 2. It should be noted that an operation button (not shown) for operating the above-described drive unit is preferably attached to an appropriate position of the operation arms 42 and 44 or the handle portions 46 and 48. Unlike the illustrated example, the front and rear operation members 40F and 40B may be formed symmetrically in the front-rear direction (that is, the distance from the radiation shielding wall to the handle portion is substantially the same). Can be used both before and after the carriage.

In the above configuration, when performing a PET diagnosis, first, a radiopharmaceutical is injected into the examinee P in the radiation control area 62 in the hospital 60 as shown in FIG. 5, and the human body placed in this radiation management area after the required time has elapsed. The examinee P is boarded in the transfer vehicle 1. This human transport vehicle 1 goes out of the entrance through the corridor 64 under the guidance of the attendant N who attends the front and rear. Then, it is only necessary to bring the examinee P together with the human transport vehicle 1 into the PET diagnostic device-equipped vehicle 66 parked at the entrance using a lift 68 or the like. In these processes, the person N is most likely to be exposed to the radiation released from the body of the examinee P. The thickness of the front and rear wall portions of the radiation shielding wall is determined in consideration of the transfer time. As a result, radiation exceeding the specified amount will not be exposed unless it is unnecessarily close to the human transporter side of the handle portion for a long time. In addition, a passerby encountered in the hallway, and sick B ₁ pass each other, for example, accepted even for facility personnel B ₂ to carry out other business, the side wall portion of the radiation shielding wall taking into account the passage time and the distance Since the thickness of the material is determined, unexpected exposure can be prevented.

  6 and 7 show modifications of the auxiliary shielding plate 26 according to the present invention. Each auxiliary shielding plate is curved inwardly of the human body transportation vehicle 1 as shown in FIG. It is provided so that the radiation emitted from the body is reflected once or a plurality of times, returns to the radiation shielding wall 24, and does not escape to the outside.

When the auxiliary shielding plate is an inclined flat plate as in the embodiment of FIGS. 1 to 5, the radiation from the examinee's body is reflected obliquely upward and forward by the rear auxiliary shielding plate as described in the examples below. There is a possibility of hitting the head of a caregiver. Therefore, in the present embodiment, as shown in the figure, the auxiliary shielding plate is an arc plate with at least the inner surface of the distal end portion being horizontal. With this shape, the tip e of the auxiliary shielding plate is received from the examinee as shown in FIG. _{2 The} radiation hitting the inner surface of the portion closer to the lower part is further lowered, and the radiation hitting the inner surface of the auxiliary shielding plate closer to the proximal end e ₁ is further reflected from the inner surface of the portion closer to the distal end e ₂ and then reflected downward. Since the reflected light is not easily leaked to the outside because it is returned to the inside, it is possible to effectively prevent the radiation of radiation from the rear auxiliary shielding plate 26b at a shallow elevation angle, which is particularly easy to directly irradiate the head of the front attendant. it can.

Particularly preferred is a quadrant that is perpendicular to the inner surface near the base end e ₁ and horizontal at the inner surface near e ₂ , as shown in FIG. 7, and in this way, as long as the incident angle θ at the base end e ₁ is not less than 45 degrees, the auxiliary The radiation incident on the inner surface of the shielding plate 26 near the base end from the lower inner side is re-reflected at the front end portion as shown in the figure and travels downward, so that scattering to the outside can be prevented more reliably.

  In this means, it is particularly important that the rear auxiliary shielding plate 26b is a curved plate, but the other front auxiliary shielding plates 26b and side auxiliary shielding plates 26s are preferably configured similarly.

  In the above configuration, the thickness of the radiation shielding wall 24 is determined in consideration of the relationship with the dimensions of each part of the human transport vehicle. First, it is desirable that the dimensions of the carriage 2 and the radiation shielding wall 24 be made as compact as possible within a range in which the examinee P having a normal physique does not feel pressure. For this purpose, for example, the width of the carriage 2 and the radiation shielding wall 24 is about 700 mm and the width of the carriage 2 and the radiation shielding wall 24 is about 1000 mm. Next, the front and rear handle portions 48 and 46 are preferably separated by about 1000 mm from the rear and front surfaces of the upper half of the trunk of the examinee P sitting on the pedestal. Then, even if the thickness of the chest of the examinee P is 300 mm, the distance from the front end to the rear end of the human body transportation vehicle is about 2300 mm, which is a size that can be safely passed through a hospital corridor or the like.

Thus, from the distances L _{1 and} L ₂ (≈1000 mm) between the attendant N who operates the front and rear handle parts 48 and 46 and both sides of the torso of the examinee P, the exposure dose of the attendant N is kept below a certain level. Thus, the thicknesses of the front and rear wall portions 24f and 24b of the radiation shielding wall 24 are determined experimentally. Further, the distance that passerby closest to the side surface of the body transport vehicle of the present application assumes about 300 mm, the left and right sidewall portions of the radiation shield wall from a distance L ₃ between the barrel portion left and right side surfaces of the examinee P and the passers 24s The thickness of is experimentally determined. Assuming that the left and right width of the body of the examinee P is about 400 mm, the distance L ₃ is about 550 mm. The height of the pedestal is set so that the heart of the examinee P is almost the same height as the front and rear handle portions 48 and 46, and the height is 1000 mm from the floor surface.
(1) Experiment contents In order to examine the radiation shielding wall thickness and radiation shielding ability of the human body transportation vehicle described in the above embodiment, subjects A, B, C, and D were changed in thickness d of each part of the radiation shielding wall. The human body transportation vehicle was mounted, and the radiation dose was measured over time at the front measurement point f, the rear measurement point b, the side measurement point s, and the diagonally front upper measurement points u and u ′. Here, as shown in FIG. 3, the rear measurement point b is an installation location of the rear handle 46 and is located at an intermediate position in the lateral width direction of the carriage (position overlapping the heart H of the examinee P as shown in FIG. 2). The measurement point f is an installation location of the front handle portion 48 and is installed at an intermediate position in the left-right width direction of the carriage. In addition, when installing a radiation measuring instrument in these positions, the operation arm and the support | pillar should just be removed beforehand. As shown in FIG. 2, the side measurement point s is set at a position approximately the same as the heart H of the examinee P, taking a distance L ₃ (= 550 mm) from the left and right side surfaces of the examinee P. Further, the diagonally upper front measurement points u and u ′ are near an imaginary line L extending from the heart H of the examinee P along the upper end of the front wall portion 24f of the radiation shielding wall as seen from the side s as shown in FIG. Between the front wall portion 24f and the front side attendant N, as shown in FIG. Each subject was administered a radiopharmaceutical F ¹⁸ -FDG with a dose of 10 mCi (370 MBq), and the cumulative radiation dose was measured every 5 minutes from the time of administration.
(2) Experimental results Table 1 below shows the accumulated radiation dose measurement values A _f , B _f , C _f , and D _f for each subject A, B, C, and D at the front measurement point f. Subject A is a cart with the radiation shielding wall removed, subject C is a cart with a thickness of the front wall portion of the radiation shielding wall of 3 mm, and subjects B and D have a thickness of the front wall portion of the radiation shielding wall. Each boarded a 5-mm bogie. The measured value is an average value of the measured values of the subject B and the subject D. FIG. 8 is a graph in which the measured value of the integrated radiation dose in each time zone is plotted on the vertical axis and the time is plotted on the horizontal axis, and these measured values are graphed for each thickness of each shielding wall. The broken line in the figure is a linear approximation line described later for the accumulated dose for each shielding thickness.

The following Table 2 shows the accumulated radiation dose measured values B _b , C _b , D _b for each subject B, C, D at the rear measurement point b. Subject B boarded a cart with a thickness of the rear wall portion 24b of the radiation shielding wall of 10 mm, and subject C and subject D boarded a cart with a thickness of the front wall portion of the radiation shielding wall of 8 mm. The measurement value is an average value of the measurement values of the subject C and the subject D. FIG. 9 is a graph in which the measured value of the integrated radiation dose in each time zone is plotted on the vertical axis and the time is plotted on the horizontal axis, and these measured values are graphed for each thickness of each shielding wall. The broken line in the figure is a linear approximation line to be described later for the accumulated dose for each shielding thickness.

The following Table 3 shows the accumulated radiation dose measurement values B _u , B _u ′, C _u , C _u ′, D _u , D _u ′ for each subject B, C, D at the diagonally upper front measurement point u, _u ′. Is shown. In the measurement at the measurement point u, the subject B is a cart with a front auxiliary shield plate thickness of 5 mm, and the subject C and the subject D are a cart with a front auxiliary shield plate thickness of 8 mm. In the measurement at the measurement point u ′, the subject B, the subject C, and the subject D are mounted on a carriage that is not provided with a front auxiliary shielding plate. The measured value is an average value of the measured values at the same shielding thickness. Further, FIG. 10 is a graph in which the measured value of the integrated radiation dose in each time zone is plotted on the vertical axis and the time is plotted on the horizontal axis, and the measured values are graphed for each shielding wall thickness. The broken line in the figure is a linear approximation line to be described later for the accumulated dose for each shielding thickness.

Table 4 below shows the accumulated radiation dose measurement values B _s , C _s , and D _s for each subject B, C, and D at the side measurement point s. Test subject B boarded a cart with a thickness of the front wall portion 24f of the radiation shielding wall of 5 mm, and subject C and test subject D boarded a cart with a thickness of the front wall portion of the radiation shield wall of 8 mm. The measurement value is an average value of the measurement values of the subject C and the subject D. Further, FIG. 11 is a graph in which the measured values of the integrated radiation dose in each time zone are plotted on the vertical axis and the time is plotted on the horizontal axis, and the measured values are graphed for each thickness of each shielding wall. The broken line in the figure is a linear approximation line to be described later for the accumulated dose for each shielding thickness.

(3) Analysis of the experimental results First, in order to determine the thickness of the front and rear parts of the enclosure 22 from the exposure dose of the attendant accompanying the front and rear of the human transport vehicle, at each of the measurement points at the front, rear, and diagonally upper front Consider radiation dose.

When the measured values obtained for each shielding thickness d (= 0 mm, 3 mm, 5 mm) shown in FIG. 8 at the front measurement point f are linearly approximated, y ₀ = −0.0159t + 3.2682, y ₃ = The following equation is obtained: −0.01t + 1.9, y ₅ = −0.0101t + 1.3826. However, y ₀ , y ₃ , and y ₅ are integrated doses (μsV) at d = 0 mm, 3 mm, and 5 mm, respectively, and t is time (minutes).

Next, predicted values y ₄ and y ₆ of radiation dose at d = 4 mm and d = 6 mm are calculated from these measured values. Therefore, considering the radiation dose function Y = f (t, d) with respect to the thickness d for each elapsed time, Y (t, d) = md + b. Here, both the slope m and the constant b are variables that depend on the elapsed time t. When the slope m is obtained between y ₃ and y ₅ , m = (y ₅ −y ₃ ) / 2, and when t = 5 (minutes), m = (1.332−1.850) /2=−0.259 (ΜsV / mm). The constant is b = Y−md, and when t = 5 minutes, b = y ₃ −m × 3 = 1.850 − (− 0.259) × 3 = 2.627 (μsV). As a result, Y (t, d) = Y (5, d) = − 0.259 × d + 2.627 is obtained. Substituting d = 4 and d = 6 into this, Y (t, d) = Y (5,4) = 1.593 (μsV) and Y (t, d) = Y (5,6) = 1.703 (μsV) Get. When the same operation is performed for t = 10, 15,... 60, the expected value shown in FIG.

When the measured values obtained for each shielding thickness d (= 8 mm, 10 mm) shown in FIG. 9 at the rear measurement point are linearly approximated, y ₈ = −0.003 t + 0.5258, y ₁₀ = −0.001 t + 0 as shown by the broken line. .3318 is obtained. However, y ₈ and y ₁₀ are integrated doses (μsV) at d = 8 mm and 10 mm, respectively, and t is time (minutes).

Then calculate the expected value _{y 3, y 4, y 5} , y 6, y 7 radiation dose at d = 3 to 7 mm from these measurements. The expected value shown in FIG. 13 is obtained by the same procedure as described for the front measurement point.

When linearly approximating the measured values obtained for each shielding thickness d (= 0 mm, 5 mm, 8 mm) shown in FIG. 10 at the diagonally upper measurement points u, u ′, y ₀ = −0.005 t + 1, The following equations are obtained: y ₅ = −0.0045t + 0.7894, y ₈ = −0.0032t + 0.6545. However, y ₀ , y ₅ , and y ₈ are integrated doses (μsV) at d = 0 mm, 5 mm, and 8 mm, respectively, and t is time (minutes).

Then calculate the expected value y _3, y ₄ radiation dose at d = 3 mm, 4 mm from these measurements. The expected value shown in FIG. 14 is obtained by the same procedure as described for the front measurement point.

  40 minutes after injecting the radiopharmaceutical, the resting period is 40 minutes, and after the resting period, the transportation by the human body transportation vehicle is started. As this transportation takes 20 minutes, the horizontal distance from the examinee to the caregiver is 1000 mm. Table 5 below shows the cumulative radiation dose for the attendant for 20 minutes at each of the front, rear, and diagonally upper measurement points. When the allowable exposure amount to the human body is 4 μsV, the minimum shielding thickness d in which the integrated dose in each direction is less than the allowable amount can be set to the thickness of the wall portion in the direction of the radiation shielding wall.

    Regarding the front measurement point f, the accumulated dose at the shielding thickness of 4 mm is 4.455 μSv, and the accumulated dose at the shielding thickness of 5 mm is 3.409 μSv. Therefore, the thickness of the front wall portion 24 f may be 5 mm. The accumulated dose at 5 mm is a value actually measured, and this value is considered to be highly reliable.

  For the rear measurement point b, the accumulated dose at a shielding thickness of 4 mm is 3.361 μSv, and the accumulated dose at a shielding thickness of 3 mm is 3.707 μSv. Will meet. However, the cumulative dose at the shielding thickness d = 3 to 7 mm is a value estimated from the measured values at the shielding thickness d = 8 mm and 10 mm, and the estimation error is considered to increase as the distance from d = 8 mm increases. And, taking into account that the required wall thickness is determined as d = 5mm from the measurement of the front measurement point where the distance from the examinee's body is the same, the thickness of the rear wall portion 24b should also be about 5mm. Is desirable. In addition, it is easier to balance the human transport vehicle if the thicknesses of the front and rear wall portions are the same. On the other hand, 8 mm can be considered as a suitable wall thickness as the required thickness of the rear wall portion supported by the actually measured values.

  Regarding the diagonally upper measurement point u, the accumulated dose at a shielding thickness of 4 mm is 3.130 μSv, and the accumulated dose at a shielding thickness of 3 mm is 3.292 μSv. Therefore, the shielding standard of 3 mm satisfies the safety standard. These accumulated doses are estimated values based on the measured values at the shielding thickness d = 0 mm, 5 mm, and 8 mm, and the gradient m of the radiation dose Y between the shielding thickness d = 5 to 8 mm is −0.044. On the other hand, since m between d = 0 to 5 mm is −0.042 and there is no significant difference, it can be seen that even the estimated value is quite reliable. Therefore, the thickness of the front auxiliary shielding plate may be 3 mm.

    Next, the thickness of the side wall portion 24s of the radiation shielding wall is determined from the exposure dose of the person who encounters and is exposed to the human body transportation vehicle. These encounters can be divided into two groups. One is a passerby who passes in the immediate vicinity of a human transport vehicle for a relatively short time, and the other is a person related to the facility except for a radiation worker and is relatively far from the human transport vehicle. May be repeatedly exposed. Assuming the passing position of a passerby from the human body transportation vehicle, the present applicant performed radiation dose measurement at the side measurement point f described above.

When the measured values obtained for each shielding thickness d (= 5 mm, 8 mm) shown in FIG. 11 at this side measurement point f are linearly approximated, y ₅ = −0.0145t + 2.2455, y ₈ = The expression -0.005t + 1.0864 is obtained. However, y ₅ and y ₈ are integrated doses (μsV) at d = 5 mm and 8 mm, respectively, and t is time (minutes). Next, predicted values y ₃ , y ₄ , y ₆ , and y ₇ of radiation dose at d = 3 mm, 4 mm, 6 mm, and 7 mm are calculated from these measured values. The expected value shown in FIG. 15 is obtained by the same procedure as described in the front measurement point. The side measurement point is a point at a distance of 550 mm from the body of the examinee P, and assumes the position of a passerby who passes the human body transportation vehicle.

Furthermore, the exposure dose of the facility equipment person far away from the passerby is calculated. The distance from the side wall portion of the radiation shielding wall to the passerby is I, the distance from the side wall portion to the facility personnel is L, and the radiation measurement amount at the side measurement point at each shielding thickness is (I / L ) Multiply ² as a coefficient to calculate the radiation dose for the personnel involved in the facility. When the above coefficient is applied to the radiation measurement amount with I = 395 mm and L = 450 mm, FIG. 16 is obtained.

    Assuming that the passer-by encounter time is 30 seconds and the facility-related person's encounter time is 2 minutes, the radiation dose during the encounter time between the passer-by and the facility-related person is calculated from the above-mentioned FIG. 15 and FIG. become that way. From this table, when the shielding thickness is selected so as to satisfy the safety standard (4 μSv), it is understood that a thickness of about 3 mm is sufficient.

1 is a side view of a human body transport vehicle according to a first embodiment of the present invention. It is a left-right direction longitudinal cross-sectional view of the human body transportation vehicle of FIG. It is a longitudinal cross-sectional view of the human body transportation vehicle of FIG. It is a cross-sectional view of the human body transportation vehicle of FIG. It is explanatory drawing of the usage example of the human body transport vehicle of FIG. It is a longitudinal cross-sectional view which shows the principal part modification of the human body transport vehicle of FIG. It is an enlarged view of the principal part of FIG. It is a figure showing the measurement dose in the front measurement point f of the radiation which leaks from the human body transportation vehicle of FIG. It is a figure showing the measurement dose in the back measurement point b of the radiation which leaks from the human body transportation vehicle of FIG. It is a figure showing the measurement dose in the diagonally front upper measurement point u and u 'of the radiation which leaks from the human body transportation vehicle of FIG. It is a figure showing the measurement dose in the side measurement point s of the radiation which leaks from the human body transportation vehicle of FIG. It is a graph showing the time-dependent change of the radiation dose in the front measurement point corresponding to each shielding thickness based on the measurement result of FIG. FIG. 10 is a graph showing a change with time in radiation dose at a rear measurement point corresponding to each shielding thickness based on the measurement result of FIG. 9. FIG. 11 is a graph showing a change in radiation dose with time at a diagonally upper front measurement point corresponding to each shielding thickness based on the measurement result of FIG. FIG. 12 is a graph showing changes in radiation dose with time at side measurement points corresponding to respective shielding thicknesses based on the measurement results of FIG. 12 is a graph showing a change with time of a radiation dose (calculated value) farther than a side measurement point corresponding to each shielding thickness based on the measurement result of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Human body transfer vehicle 2 ... Carriage 4 ... Base frame 6 ... Front wheel 8 ... Rear wheel
10 ... Drive unit 12 ... Base 14 ... Substrate 16 ... Front projecting plate 18 ... Back projecting plate
22 ... enclosure 24 ... radiation shielding wall 24f ... front wall part 24b ... rear wall part
24s ... side wall part 26 ... auxiliary shielding plate 26f ... front side auxiliary shielding plate
26b ... Back side auxiliary shielding plate 26s ... Side auxiliary shielding plate 28 ... Hinge 30 ... Door 32 ... Handle
40F, 40B ... Operation member 42, 44 ... Operation arm 46, 48 ... Handle
48 ... Front handle
60 ... Hospital 62 ... Radiation control area 64 ... Corridor 66 ... PET equipped car 68 ... Lift f ... Front measurement point s ... Side measurement point b ... Rear measurement point u, u '... Diagonal upper front measurement point P ... Patient N ... Intermediary B ₁ ... Passer-by B ₂ ... Facility personnel

Claims (5)

A transport vehicle for transporting a patient ( P ) who has injected a nuclear medical radiation source into the body,
It provided the dolly (2) that囲成radiation shielding wall (24) around while have a base (12),
A caregiver (N) having a width at the back of the operation arm (42) protruding from the rear side of the dolly at least to the rear of the dolly at a distance from the radiation shielding wall (24) and shorter than the protruding length of the operation arm. A human body transporting vehicle equipped with a handle portion (46) for operating . In addition, a handle (48) is provided on the front side of the carriage (2) to be operated by the attendant (N) away from the radiation shielding wall (24) .
The front or rear handle portion ( 46, 46 b ) passes through the front or rear corresponding wall portion ( 24 f, 24 b ) of the radiation shielding wall ( 24 ) from a part of the body of the examinee ( P ) placed on the pedestal ( 12 ) . the dose of radiation reaching the 48) that defines the thickness of the corresponding wall portions in accordance with the distance from the part of the body to be equal to or less than a specified amount until the handle portion (46,48) (24f, 24b) The human body transportation vehicle according to claim 1, wherein As a box-shaped of the radiation shielding wall (24), the rear wall portion (24b) is brought closer to the lower side examinees in the second half portion of the carriage (2) (P capable seated chair form of the radiation shield wall (24) characterized in that a pedestal (12), according to claim 2 human transport carriage according. Using the body part as the torso of the examinee ( P ) , the caregiver ( N ) uses this body transport vehicle to determine the radiation dose reaching the front or rear handle ( 46,48 ) from this torso. As the cumulative dose that can be exposed at the position of the front or rear handle ( 46,48 ) during the transfer time of this, the thickness of the front or rear corresponding wall portion ( 24f, 24b ) of the radiation shielding wall ( 24 ) is calculated from this cumulative dose. encountered who approached beside the truck (2) can be exposed to radiation it through sidewall portions (24s) of the radiation shielding wall (24) in the set, further set the encounter time shorter than the transport time of 4. The human transport vehicle according to claim 3, wherein the thickness of the side wall portion ( 24s ) is determined so that the dose is below a prescribed amount. The auxiliary shielding plate ( 26 ) inclined upward and inward is attached to at least an upper end portion of the front wall or the rear wall of the radiation shielding wall ( 24 ). The human body transport vehicle described in Crab.

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