JP5800588B2 - Radiation irradiation equipment - Google Patents

Description

  The present invention relates to a radiation irradiation apparatus, and in particular, a sample of a blood product or the like in a radiation irradiation apparatus that irradiates radiation containing X-rays or γ rays to a blood bag (hereinafter referred to as a blood product) enclosing blood for blood transfusion. The present invention relates to a technique for correcting a radiation dose by thickness.

It is known that blood for transfusion in a blood bag has a side effect called GVHD (Graph Versus Host Dissease). In order to prevent this, it is necessary to irradiate the blood product with a treatment to inactivate lymphocytes in the blood product. The radiation used for the inactivation treatment includes γ rays and X rays using the radioisotope ¹³⁷ Cs (cesium).

  As a radiation irradiation apparatus for inactivation treatment, for example, a two-way irradiation apparatus disclosed in Patent Document 1 is known. The two-way irradiation device is an X-ray tube device (referred to as the first X-ray tube device), and the cathode and anode of the second X-ray tube device face the first X-ray tube device and are installed in the protection room. A sample dish (hereinafter referred to as a tray) is disposed between the first and second X-ray tube apparatuses. A dosimeter probe for monitoring the irradiation dose is arranged in the vicinity of the tray. By simultaneously irradiating X-rays from the upper and lower surfaces of the sample with the two X-ray tube apparatuses, it is not necessary to turn the tray over, and a larger dose and uniform irradiation can be performed than in the conventional apparatus. The irradiation dose is monitored by a dosimeter probe, and when the specified dose is reached, the irradiation is automatically stopped.

Japanese Utility Model Publication No. 7-43679

  In the two-way irradiation device, the dose rate detected by the dosimeter probe (in order to ensure that a blood product placed within the X-ray irradiation range is always irradiated with a dose of X-rays exceeding a predetermined value) X-ray irradiation dose per unit time) is adjusted by the exposure length of the probe. As an adjustment procedure, first place a simulated blood product filled with water in a blood bag or a phantom equivalent to a blood product within the tray storage range (within the X-ray irradiation range), and use the dosimeter probe to store the tray. The dose distribution is obtained by measuring the X-ray dose at each location within the range. The minimum dose rate within the tray storage range is specified from the dose distribution. Place the dosimeter probe used for dose distribution measurement at a predetermined position (monitor position) near the tray so that the dose rate detected by the dosimeter probe at this position is less than the minimum dose rate within the tray storage range. In addition, the length of exposure of the dosimeter probe from the X-ray shield is adjusted.

  The dosimeter probe has a rod shape, and is supported by a support portion of a cylindrical X-ray shield (metal). The dosimeter probe and the support are fixed by a set screw. The incident amount of the X-ray dose to the dosimeter probe is determined by the length of exposure of the dosimeter probe from the support part. If the dosimeter probe is exposed for a long time, the monitor dose rate increases, and conversely, the monitor dose rate decreases.

  That is, since the exposure length is adjusted so that the dose rate detected by the dosimeter probe at the monitor position is lower than the dose rate in the tray storage range, the dose measured at the monitor position is within the X-ray irradiation range. Lower than any part of the throat. For this reason, when the measurement result at the monitor position reaches the prescribed dose, the radiation product is stopped, so that the blood product placed in the X-ray irradiation range is always irradiated with more than the prescribed amount of X-rays. .

  The X-ray dose radiated from the X-ray tube device is gradually attenuated as the surface of the anode target becomes rough due to the collision of thermoelectrons, and the minimum value of the dose rate within the tray storage range also changes. For this reason, it is necessary to periodically adjust the exposure length of the dosimeter probe.

  The procedure for adjusting the exposure length of the dosimeter probe will be described in detail. First, remove the protective cover of about 15 kg, remove the dosimeter probe from the monitor position, place it at a predetermined location within the tray storage range, attach the protective cover, and measure the dose rate. This operation is repeated to measure the dose distribution within the tray storage range. Remove the protective cover again and insert the dosimeter probe into the support at the monitor position and fix it with a push screw. Put on the protective cover again and irradiate with X-rays. Read the monitor dose rate at this time, and if the monitor dose rate value is larger than the minimum dose rate obtained by the dose distribution measurement, remove the protective cover again and loosen the push screw holding the dosimeter probe. Pull the radiation detection part of the dosimeter probe into the support part by hand. Then, the dosimeter probe's set screw is tightened again. After that, a protective cover is attached, X-rays are irradiated, and it is confirmed whether or not the same value as the minimum dose rate is obtained.

  As described above, in the conventional two-way irradiation apparatus, the position adjustment of the dosimeter probe is performed manually, and the adjustment of the exposure length depends on the amount of the target. Many times, it took time to make accurate adjustments. It is necessary to repeat the work of removing and attaching the heavy protective cover, and the burden on the operator who performs the adjustment is great. In addition, if the push screw is loosened after adjustment and the dosimeter probe is misaligned, there is a risk of mis-irradiation such as insufficient irradiation dose or over-irradiation. It was.

  The objective of this invention is providing the radiation irradiation apparatus which can perform the position adjustment of a dosimeter probe accurately and in a short time.

  In order to achieve the above object, according to the present invention, the following radiation irradiation apparatus is provided. That is, a radiation irradiating unit for irradiating the irradiated object, a mounting unit for mounting the irradiated object in the radiation irradiation region of the radiation irradiating unit, a dosimeter probe arranged at a predetermined position near the radiation irradiation region, A radiation irradiation apparatus having a control unit for stopping radiation irradiation of the radiation irradiation unit according to a dose detected by the dosimeter probe, wherein the dosimeter probe is supported by a dosimeter probe support mechanism, A radiation shield that covers a portion of the dosimeter probe, and an adjustment mechanism that adjusts the length of exposure of the dosimeter probe from the radiation shield by moving the radiation shield relative to the dosimeter probe; Is provided.

  For example, the adjustment mechanism includes a feed screw and a mechanism that moves the radiation shield in the longitudinal direction of the dosimeter probe according to the rotation amount of the feed screw.

  The radiation protective cover that covers the outside of the space where the radiation irradiation unit and the dosimeter probe are arranged is provided with an opening for operating the adjustment mechanism, and a removable protective cover is attached to the opening. preferable.

  At least one of the opening of the radiation protective cover and the removable protective cover may be configured to include a detection unit that detects that the removable protective cover is attached to the opening.

  When the detection unit does not detect that a removable protective cover is attached, the control unit can be configured not to irradiate the radiation irradiation unit. The control unit can also display an error display on the display unit when a removable protective cover is not attached.

  As described above, according to the present invention, the position adjustment of the dosimeter probe can be accurately performed in a short time. In addition, it is possible to prevent erroneous irradiation due to the position shift after adjusting the monitor dose rate, and to reduce the burden on the operator.

1 is a block diagram illustrating a configuration of a radiation irradiation apparatus (bidirectional irradiation apparatus) 100 according to an embodiment. It is a top view of the probe support mechanism 70 of the apparatus of FIG. FIG. 3 is a view as seen from an arrow A of the probe support mechanism of FIG. 2. FIG. 3 is an enlarged view of FIG. 2. It is a B arrow view of FIG. It is a top view which shows the mechanism 70a which supports the dosimeter probe 7a of the probe support mechanism 70 of FIG. It is a D arrow line view of FIG. It is a top view of the probe support mechanism 70 of the state which removed the protective cover 31 for small windows of the radiation irradiation apparatus of embodiment. It is F arrow line view of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the overall configuration of the radiation irradiation apparatus of the present embodiment. Here, a two-way irradiation apparatus that irradiates an object to be irradiated with X-rays from two directions as shown in FIG. 1 will be described as an example. The two-way irradiation apparatus 100 includes a tray holding unit 10, X-ray tube devices 2 and 3 that are vertically opposed to each other with the tray holding unit 10 interposed therebetween, and a dosimeter probe 7 a that is arranged in the vicinity of the tray holding unit 10. The probe support mechanism 70 and the X-ray shield 1a covering the space in which these are arranged are provided. The tray holding unit 10 is equipped with a tray 13 that accommodates an irradiation object 13a such as a blood product. The tray holding unit 10 has a structure that can be pulled out to a position 10a outside the shield 1a in order to carry out the tray 13 to the outside.

  The two-way irradiation apparatus 100 further includes a high voltage generation unit 4 that supplies power to the X-ray tube apparatuses 2 and 3, a cooling device 5 for cooling the X-ray tube apparatuses 2 and 3, a dosimeter 7, a touch panel, and the like. An operation panel 8, a control device 6 and a barcode reader 14 are provided.

  Two types or three or more types of trays 13 for preparing a thick blood product and a tray for storing a thin blood product are prepared. Each tray 13 is provided with a barcode, and when read by the barcode reader 14, barcode information is sent to the control device 6 to recognize the thickness of the tray.

  An X-ray filter 11 is disposed between the upper X-ray tube device 2 and the tray 13, and an X-ray filter 12 is disposed between the lower X-ray tube device 3 and the tray 13. X-ray filters 11 and 12 having a predetermined X-ray transmittance are used. A space between the X-ray filter 11 and the X-ray filter 12 is referred to as an X-ray irradiation chamber 1b.

  A high voltage is independently applied to the upper X-ray tube device 2 by the high voltage generator 4a of the high voltage generation unit 4, and a high voltage is independently applied to the lower X-ray tube device 3 by the high voltage generator 4b. The As a result, the X-ray beam bundles 2 a and 3 a are respectively emitted from the upper X-ray tube device 2 and the lower X-ray tube device 3, and are irradiated to the irradiated object in the tray 13.

  The cooling device 5 cools the anode by supplying cooling oil to the X-ray tube devices 2 and 3. A circulating cooling device (or water supply) 9 is connected to the cooling device 5, and the cooling oil warmed by the X-ray tube devices 2 and 3 is cooled by the cooling water.

  The dosimeter 7 measures the X-ray dose incident on the dosimeter probe 7a. The probe support mechanism 70 that supports the dosimeter probe 7 a is provided with a correction filter 25 for correcting the X-ray absorption amount according to the thickness of the tray 13. The configuration of the probe support mechanism 70 will be described in detail later.

  The operation panel (touch panel) 8 is used to set the X-ray irradiation conditions such as the dose of the upper X-ray tube apparatus 2 and the lower X-ray tube apparatus 3 irradiated to the tray 13 and the thickness of the tray, message display, and registration of various data. This is done by an operator's operation. The shield 1a shields X-rays from leaking out from the irradiation chamber 1b.

  In this way, by irradiating the X-ray beam bundles 2a and 3a simultaneously from the upper surface and the lower surface of the irradiated object 13a by the two X-ray tube devices 2 and 3, there is no need to turn the tray 13 over, and a large dose And uniform X-ray irradiation can be performed. The irradiation dose is monitored by the dosimeter probe 7a, and when the dose of the dosimeter 7 reaches the set value, the control device 6 stops the radiation irradiation.

  In the two-way irradiation apparatus, the exposure length of the dosimeter probe is ensured to ensure that the irradiated object 13a placed in the X-ray irradiation range 50 is always irradiated with X-rays at a dose rate equal to or higher than a predetermined value. It is adjusting. As an adjustment procedure, a phantom is placed in the X-ray irradiation range 50, and the dose distribution is obtained by measuring the X-ray dose at each location in the tray storage range using the dosimeter probe 7a. From the dose distribution, the minimum value of the dose rate within the tray storage range 50 is specified. The dosimeter probe 7a used for the dose distribution measurement is attached to the probe support mechanism 70 so that the dose rate detected by the dosimeter probe at this position is not more than the minimum dose rate in the tray storage range. Adjusts the length exposed from the X-ray shield.

  Hereinafter, the probe support mechanism 70 will be described with reference to FIGS. 2 is a top view of the probe support mechanism 70 shown by cutting out the shield 1a, FIG. 3 is a view taken in the direction of arrow A in FIG. 2 (a part of the shield 1a is cut away), and FIG. 4 is an enlarged view (front view) of FIG.

  As shown in FIGS. 2 to 5, the shield 1 a is provided with a box-shaped cover 30 that covers the outside of the region where the dosimeter probe 7 a of the irradiation chamber 1 b is disposed. The cover 30 is formed of an X-ray shield similar to the shield 1a.

  An opening for inserting the probe support mechanism 70 is formed in the shield 1 a inside the cover 30. A plate-like base 60 is fixed to the outside of the opening by a fixing tool 60a. The probe support mechanism 70 is fixed to the plate-like base 60, and is inserted from the opening of the shield 1a to the irradiation chamber 1b side.

The probe support mechanism 70 includes a mechanism 70 a that supports the dosimeter probe 7 a and a mechanism 70 b that supports the correction filter 25. The correction filter 25 attenuates the X-ray dose corresponding to the X-ray absorption amount due to the thickness of the irradiated object 13a so that the X-ray dose detected by the dosimeter probe 7a becomes the X-ray dose at the center of the thickness of the irradiated object 13a. This is a filter 25 for correcting to The value of the dose rate irradiated to the central portion of the irradiated object 13a varies depending on the thickness of the irradiated object (blood product) 13a, and the thick blood product has a larger amount of X-ray absorption than the thin blood product. The central dose rate value is smaller for hot blood products than for thin blood products. It is well known that this X-ray absorption is expressed by the following equation.
I / I ₀ = exp (−μt)
(Where I: dose after transmission, I ₀ : dose before transmission, μ: absorption coefficient, t: thickness of object)
In order to correct this difference in absorption, in the two-way irradiation apparatus, a correction filter 25 corresponding to the X-ray absorption amount is put on the dosimeter probe 7a as necessary to correct the state close to the center of the irradiated object 13a. Monitor X-ray dose.

  The mechanism 70b that supports the correction filter 25 is a mechanism that slides the correction filter 25 in the direction of the arrow 71 by the driving force of the motor 21 in FIG. Thereby, the state where the correction filter 25 covers the dosimeter probe 7a and the state where it does not cover are selectively switched. Since the structure of the mechanism 70b is widely known, detailed description thereof is omitted. The operation of the motor 21 is controlled by the control device 6. Specifically, when the thickness of the irradiation object 13a set by the operator on the operation panel 8 is a thickness that requires the correction filter 25, the control device 6 puts the correction filter 25 on the dosimeter probe 7a. If the correction filter 25 is not necessary, the motor 21 is driven so that the filter 25 is slid in the retracting direction.

  In order to explain the mechanism 70a for supporting the dosimeter probe 7a, FIG. 6 shows an enlarged view of the configuration in which the support mechanism 70b of the correction filter 25 is removed from the probe support mechanism 70 of FIG. FIG. 7 shows a view taken in the direction of arrow D in FIG. As shown in FIGS. 6 and 7, the mechanism 70 a that supports the dosimeter probe 7 a includes a fixing bracket 43, a support base 44, a shield 41, a roller 42, a guide 40, a transmission bracket 45, a feed screw 46, and a fixing screw 47. It is configured with.

  The dosimeter probe 7a is fixed to the fixing metal 43 by being inserted into the fixing metal 43 and tightened with a fixing screw 43a. The support base 44 is parallel to the dosimeter probe 7 a in the longitudinal direction, has a flat upper surface, and one end is fixed to the base 60. The fixing metal 43 is fixed to the side surface of the support base 44 by a connecting metal 48.

  The guide 40 is a bar disposed in parallel with the dosimeter probe 7 a to guide the shield 41 linearly, and one end is fixed to the base 60. The shield 41 is made of a material that shields X-rays, and is provided with two parallel through holes. The tip of the dosimeter probe 7a is inserted into one of the through holes, and the guide 40 is inserted into the other. A roller 42 is attached to the side surface of the shield 41, and the roller 42 is mounted on the upper surface of the support base 44. Thus, the shield 41 is supported by the guide 40 and the support base 44 and is movable in the longitudinal direction of the dosimeter probe 7a by the roller 42.

  The upper end of the transmission fitting 45 is connected to the lower surface of the shield 41 by a screw 45a. A feed screw 46 is inserted into the end face on the base side of the transmission fitting 45. Further, the tip of the fixing screw 47 is abutted against the end face on the base side of the transmission fitting 45. A nut 47 a for locking the fixing screw 47 is disposed at a portion where the fixing screw 47 contacts the base 60.

  Next, the movement of each part will be described. When the operator loosens the lock nut 47a of the fixing screw 47 to release the lock and rotates the feed screw 46 clockwise, the transmission fitting 45 starts moving in the direction approaching the base 60 and is connected to the shield. 41 is also guided by the guide 40 and moves in a direction approaching the base 60 direction. Thereby, the length by which the radiation detection part 7b at the tip of the dosimeter probe 7a is exposed from the shield 41 is increased, and the monitored dose rate can be increased.

  On the other hand, when the feed screw 46 is rotated counterclockwise, the transmission fitting 45 and the shield 41 move away from the base 60, and the shield 41 covers the radiation detector 7b. The dose rate monitored by 7b can be reduced. If the screw pitch of the feed screw 46 is made fine, the shield 41 can be adjusted more finely.

  Further, since the position of the dosimeter probe 7a is fixed to the base 60 via the probe fixing bracket 43, the coupling bracket 48, and the support base 44, the operator rotates the feed screw 46 to adjust the monitor dose rate. There is no concern that the dosimeter probe 7a will be displaced even if the measurement is performed.

  As described above, in the present embodiment, the operator performs the operation of rotating the feed screw 46 so that the length at which the radiation detector 7b at the tip of the dosimeter probe 7a is exposed from the shield 41 is continuously fine. Can be adjusted. This eliminates the need for the operator to adjust the position of the dosimeter probe by adjusting the position of the dosimeter probe by trial and error as in the prior art, and the monitor dose rate of the dosimeter probe can be adjusted with high accuracy.

  Moreover, in this embodiment, the monitor dose rate of the dosimeter probe 7a can be adjusted without removing the entire heavy protective cover 30 which is generally about 15 kg. This will be described below.

  A feed screw 46 for adjusting the exposed length of the dosimeter probe 7 a is disposed outside the base 60. In this embodiment, as shown in FIGS. 2 to 5, a small window (opening) 30 a is provided in a region facing the feed screw 46 and the fixing screw 47 of the protective cover 30, and the small window protective cover 31 is screwed. 31a is detachably attached. The small window protective cover 31 is made of a material that shields the same X-rays as the protective cover 30.

  Therefore, when adjusting the monitor dose rate of the dosimeter probe 7a, the small window 30a is opened by removing the small window protective cover 31 as shown in FIGS. 8 and 9, and the operator passes through the small window 30a. , Feed screw 46, fixing screw 47 and nut 47a can be accessed. In this embodiment, it is not necessary to remove the heavy protective cover 30 of about 15 kg, and the feed screw 46 and the lock nut 47 can be accessed by removing the small cover protective cover 30 of about 2 kg. Can be reduced. 8 and 9, reference numeral 7c denotes a cable for connecting the dosimeter probe 7a and the dosimeter 7.

  Further, when measuring the dose distribution in the X-ray irradiation range 50, it is necessary to remove the dosimeter probe 7a from the support mechanism 70a. However, in this embodiment, the dosimeter probe 7a is removed by removing the connecting bracket 48 from the fixing bracket 43. The entire fixture 43 can be removed and drawn into the irradiation chamber 1b to measure the dose distribution. That is, the dose distribution measurement can be performed by removing the dosimeter probe 7a together with the fixing bracket 43 without removing the entire protective cover 30. When taking out the dosimeter probe 7a outside the irradiation chamber 1b for calibration of the dosimeter, etc., loosen the fixing screw 43a and remove the fixing bracket from the dosimeter probe 7a, and then remove the dose from the small window 30a. Only the total probe 7a can be taken out. That is, the dosimeter probe 7a can be attached and detached from the small window 30a without removing the entire protective cover 30. In the conventional apparatus, in the case of dose distribution measurement and dosimeter configuration, etc., it was necessary to remove the entire protective cover, and then loosen the thumbscrew in the irradiation chamber and pull out the dosimeter probe. Since it is not necessary to remove the entire cover 30, the operator's work is reduced.

  Furthermore, in the present embodiment, the detection switch 33 is provided on the base 60 so that the X-ray leakage due to the forgotten attachment of the small window protective cover 31 does not occur, and the detection switch 33 is pushed inside the small window protective cover 31. The protruding cam 34 is added. As a result, it is possible to electrically detect that the detection switch 33 is pushed by the cam 34 of the small window protective cover 31 as shown in FIG. 4, and it is possible to detect forgetting to attach the small window protective cover 31. When the detection switch 33 is not pushed by the cam 34, the control device 6 is configured so that X-ray irradiation cannot be started. In addition, the control device 6 notifies the operator by displaying an error display indicating that the small window protective cover 31 is forgotten to be attached on the display unit of the operation panel 8.

  As described above, in the present invention, by providing a monitor dose rate adjustment mechanism, the adjustment time can be shortened, and it is possible to prevent erroneous irradiation due to a positional deviation of the dosimeter probe. In addition, adjustment is possible without removing a heavy protective cover, reducing the burden on the operator and adjusting the monitor dose rate.

  In the present embodiment, an apparatus that irradiates X-rays as radiation has been described. However, the present invention can also be applied to other radiation irradiation apparatuses such as γ-rays.

1: protective box, 1a: shield, 1b: irradiation chamber, 2: upper X-ray tube device, 2a: upper X-ray tube device, 3: lower X-ray tube device, 3a: lower X-ray tube device, 4: high voltage generation Unit, 4a: High voltage generator, 4b: High voltage generator, 5: Cooling device, 6: Controller, 7: Dosimeter, 7a: Dosimeter probe, 7b: Radiation detector, 7c: Dosimeter probe cable, 8: Operation panel (touch panel), 9: Circulating cooling device or tap water, 10: Tray holding unit, 10a: Tray holding unit unloading position, 11: X-ray filter, 12: X-ray filter, 13: Tray with barcode 13a: irradiated object, 14: bar code reader, 21: filter drive motor, 25: correction filter, 30: protective cover, 31: protective cover for small window, 33: detection switch forgotten to attach protective cover for small window 34: cam, 40: guide, 41: shield, 42: roller, 43: probe fixing bracket, 44: support base, 45: transmission bracket, 46: feed screw, 47: fixing screw, 47a: fixing nut, 48: 50: X-ray irradiation range corresponding to the tray storage range, 60: base, 70: probe support mechanism, 70a: dosimeter probe support mechanism, 70b: correction filter support mechanism, 100: X-ray irradiation device (2 Directional irradiation device)

Claims (7)

A radiation irradiating unit for irradiating the irradiated object, a mounting unit for mounting the irradiated object in a radiation irradiation region of the radiation irradiating unit, and a dosimeter probe disposed at a predetermined position near the radiation irradiation region; A control unit for stopping radiation irradiation of the radiation irradiation unit by a dose detected by the dosimeter probe, a space shield covering a space in which the mounting unit is disposed, and an outside of an opening provided in the space shield has a fixed base and a dosimeter probe supporting mechanism for supporting the dosimeter probe inside the space of the space shield to,
The dosimeter probe support mechanism includes a support base fixed to the base and supporting the dosimeter probe, a radiation shield covering a part of the dosimeter probe, and a transmission fitting connected to the radiation shield. A feed screw inserted into the base and a fixing screw releasably secured to the base;
The feed screw has a tip inserted into the transmission fitting, feeds the transmission fitting away from the base according to the rotation direction thereof, and retracts the radiation shield in the direction of approaching the base. Move it in the longitudinal direction of the meter probe,
The fixing screw has a distal end abutted against an end portion of the transmission fitting .   The radiation irradiation apparatus according to claim 1,
  The dosimeter probe support mechanism further includes a rod-shaped guide having one end fixed to the base,
  The radiation irradiation apparatus, wherein the guide is arranged in parallel with the dosimeter probe and is inserted into a through hole provided in the radiation shield to guide the movement of the transmission fitting.   The radiation irradiation apparatus according to claim 1, wherein a lock nut for releasing the fixation with respect to the base is disposed outside the base in the fixing screw. The radiation irradiation apparatus according to claim 1, further comprising a radiation protection cover that covers an outside of a space in which the radiation irradiation unit and the dosimeter probe are arranged,
The radiation protective cover is provided with an opening for operating the adjusting mechanism, and a removable protective cover is attached to the opening. 5. The radiation irradiation apparatus according to claim 4 , wherein at least one of the opening of the radiation protective cover and the removable protective cover detects that the removable protective cover is attached to the opening. A radiation irradiation apparatus comprising a detection unit. 6. The radiation irradiation apparatus according to claim 5 , wherein when the detection unit does not detect that the removable protective cover is attached, the control unit does not cause the radiation irradiation unit to emit radiation. Radiation irradiation device characterized. The radiation irradiation apparatus according to claim 6 , wherein the control unit displays an error display on a display unit when the removable protective cover is not attached.

Images