JP2010060523A - Beam position monitor and beam position measuring method of particle beam therapy device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a beam position monitor and a beam position measuring method for a particle beam therapy device capable of measuring beam position of particle beam with sufficient precision even if it is in the raster scanning method and attains miniaturization or cost reduction of the beam position monitor. <P>SOLUTION: A particle beam irradiated to a test substance 10 receives signal created in a condition where no scanning is implemented from one stopping irradiation spot to next stopping irradiation spot as a timing signal to create digital signal using collected charge acquired at a timing receiving the timing signal concerned. Thus created digital signal is used to calculate the beam position of the particle beam. The main configuration includes an I/V converter 501 creating voltage signal through I/V conversion of current output depending on collected charge, an ADC circuit 503 creating digital signal through A/D conversion of the created voltage signal, an FPGA 504 calculating the beam position using created digital signal, and a radiation dosage termination signal transmitting/receiving section 505 receiving timing signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a beam position monitor and a beam position measurement method for a particle beam, which are applied to a particle beam therapy system and measure the beam position of a particle beam.

  Conventionally, as a particle beam therapy apparatus that irradiates an affected part of a subject with a particle beam such as a heavy particle beam such as carbon or a proton beam, and kills cancer cells, the irradiation site is virtually divided into three-dimensional lattice points. A scanning irradiation method has been developed that effectively kills cancer cells while reducing exposure to normal sites by irradiating a particle beam.

  As one of the scanning irradiation methods, there is a spot scanning irradiation method. In the spot scanning irradiation method, irradiation with a particle beam is temporarily stopped at a timing at which a dose expiration signal is generated indicating that a dose irradiated to a certain irradiation point has reached a set value for the irradiation point. After that, the particles are again generated at the timing when the irradiation position setting completion signal is generated, which is supplied to the scanning electromagnet that scans the irradiation position of the particle beam to the next irradiation point and indicates that the excitation current for driving the scanning electromagnet becomes constant. Start irradiation with a line beam. By repeating this operation, irradiation of the entire affected area is performed.

  However, in the spot scanning irradiation method, even if a dose expiration signal is generated, the particle beam does not stop immediately, and the particle beam is irradiated on the subject while scanning the irradiation position from one irradiation point to the next irradiation point. The dose to be irradiated, that is, the leak dose to the normal part of the subject becomes a problem. In particular, when the dose set to irradiate each irradiation point is small, the ratio of leaked dose (leakage dose / set dose) increases. To reduce the influence of leakage dose on normal sites, it is necessary to lower the beam intensity to make the ratio of leakage dose relatively small. However, reducing the beam intensity leads to a longer treatment period and the patient. Will increase the physical burden on the body.

  In order to solve the problem of the spot scanning irradiation method, the raster scanning irradiation method is attracting attention (for example, see Non-Patent Document 1). Unlike the spot scanning irradiation method, the raster scanning irradiation method does not stop the particle beam even when the irradiation position is changed. If the irradiation point irradiated with the particle beam beam not scanned is called a stop irradiation point, in the raster scanning irradiation method, the irradiation dose for each stop irradiation point is also taken into consideration in the irradiation dose during the scanning of the particle beam. Optimization is performed. However, since the beam position of the particle beam scanned at the irradiation position is monitored by the beam position monitor, the beam position monitor is required to have high beam position measurement accuracy.

  Conventionally, as a beam position monitor used in raster scanning irradiation, an electrode portion of a collecting electrode in an ionization chamber has a strip as a number of collecting electrode elements arranged in one axial direction and not electrically connected, and is incident on each strip. There is known a beam position monitor having a signal processing circuit that collects charges as collected charges by using the ionization action by the particle beam, and calculates the beam position using the collected charges (see, for example, Patent Document 1). ).

In the conventional beam position monitor, the amount of collected charge collected by the collecting electrode is accumulated by an integrator, and the beam position is calculated using the accumulated amount of collected collected charge. Identification of the beam position is generally performed by calculating the position of the center of gravity of the particle beam by using the amount of collected charges collected at a so-called spot in the collecting electrode on which the particle beam is incident. .
JP 2001-33560 A National Institute of Radiological Sciences HIMAC Report HIMAC-124 (April 2007)

  In the raster scanning irradiation method, the particle beam is not stopped even when scanning between irradiation positions, so in the conventional beam position monitor, the charges collected while scanning the particle beam between the irradiation points are also integrated as collected charges. Is done. Therefore, there is a problem that the accuracy of beam position measurement is lowered mainly because the charges collected during the scanning of the particle beam and the charges collected at the completion of scanning are not accurately distinguished. In particular, the greater the distance from one stop irradiation point to the next stop irradiation point, the greater the degree of decrease in beam position measurement accuracy of the beam position monitor.

  Further, in the raster scanning irradiation method, the irradiation time has a large variation at each stop irradiation point, that is, a variation in the amount of electricity of the collected charges, and there can be a difference of about two digits in a normal treatment plan. In a conventional beam position monitor using an integrator, it is necessary to provide a plurality of capacitors having different capacities, and to switch the capacitors as appropriate according to the length of irradiation time, thereby ensuring beam position measurement accuracy. However, if a configuration in which a plurality of capacitors are provided is adopted, the signal processing circuit becomes complicated, and it becomes difficult to reduce the size and cost.

  The present invention has been made in view of the above problems, and is intended for a particle beam therapy system capable of accurately measuring the beam position of a particle beam even in the raster scanning method and reducing the size or cost of the beam position monitor. An object of the present invention is to provide a beam position monitor and a beam position measuring method for a particle beam.

  In order to solve the above-described problems, in the beam position monitor for the particle beam therapy system according to the present invention, a plurality of stop irradiation points set on the subject are irradiated with a particle beam, and the stop irradiation points are irradiated. When the dose reaches the set value, the collecting electrode is provided in the particle beam therapy system that scans the irradiation position of the particle beam beam to the next stop irradiation point, and is set on the trajectory of the particle beam and applied with a voltage Then, the charge generated by the ionization action at the collection electrode when the particle beam is incident on the collection electrode is collected as the collected charge, and the beam position of the particle beam scanned between the irradiation positions is collected using the collected charge. In a beam position monitor having a signal processing circuit for performing beam position calculation for specifying, the signal processing circuit performs I / V conversion on a current output generated by the ionization action in the collecting electrode, and outputs a current. An I / V converter that generates a corresponding voltage signal, a digital signal generation circuit that receives a voltage signal generated by the I / V converter and generates a digital signal related to collected charges, and the stop irradiation point A timing signal transmission / reception unit that receives a signal generated in a non-scanning state of the particle beam scanned at the next stop irradiation point as a timing signal; and the digital signal at a timing at which the timing signal transmission / reception unit receives the timing signal A beam position calculation unit that receives a digital signal related to the collected charge generated by the generation circuit and performs the beam position calculation using the received digital signal related to the collected charge.

  In the beam position measuring method of the particle beam according to the present invention, when a plurality of stop irradiation points set on the subject are irradiated with the particle beam, and the dose irradiated to the stop irradiation points reaches a set value. In addition, when the particle beam is incident on a collecting electrode which is applied to a particle beam therapy apparatus that scans the irradiation position of the particle beam beam to the next stop irradiation point and is set on the trajectory of the particle beam and applied with a voltage. A particle beam that identifies the beam position of the particle beam scanned between the irradiation positions by collecting the charge generated by the ionization action at the collecting electrode as a collected charge and performing beam position calculation using the collected charge In the beam position measuring method of the beam, the current output generated by the ionization action at the collecting electrode is I / V converted to generate a voltage signal corresponding to the current output, and the collected voltage is converted from the generated voltage signal. Set to perform the beam position calculation using the generated digital signal related to the collected charge, and generate in the non-scanning state of the particle beam scanned from the stop irradiation point to the next stop irradiation point The digital signal is generated at a timing when the timing signal is generated.

  According to the present invention, the beam position of the particle beam can be accurately measured even in the raster scanning method, and the size and cost of the beam position monitor can be reduced.

  Embodiments of a beam position monitor and a particle beam beam position measuring method for a particle beam therapy system according to the present invention will be described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a schematic view of a particle beam therapy system 1 including a beam position monitor 50 according to the first embodiment. FIG. 2 is a schematic view of the beam position monitor 50 of the first embodiment.

  The particle beam therapy system 1 equipped with the beam position monitor 50 irradiates the affected part 11 of the subject 10 with a particle beam such as proton or carbon by the raster scanning irradiation method that does not stop the particle beam even when the irradiation position is changed. To treat cancer.

  As shown in FIG. 1, the particle beam therapy apparatus 1 includes a scanning electromagnet 20, a scanning electromagnet power supply 30, a dose monitor 40, a beam position monitor 50, a ridge filter 60, a range shifter 70, and an irradiation control apparatus 80. With.

  First, the basic operation of the particle beam therapy system 1 will be described.

  In the particle beam therapy apparatus 1, the particle beam is accelerated by an accelerator (not shown), and enters the scanning electromagnet 20 as a particle beam beam having energy according to the depth of the body where the affected part 11 of the subject 10 is located. The scanning electromagnet 20 is positioned by a scanning electromagnet power supply 30, and the particle beam is irradiated at an irradiation position (X, Y) on the surface perpendicular to the particle beam axis in the subject 10, that is, according to the setting position of the scanning electromagnet 20. 1 are scanned in the X direction and the Y direction shown in FIG.

  The particle beam scanned by the scanning electromagnet 20 enters the dose monitor 40, and the irradiation dose at each of the irradiation points p1, p2, p3... Set on the affected part 11 of the subject 10 is measured. The The dose monitor 40 measures an ionization chamber that collects charges generated by the ionizing action of particle beams in the container with parallel electrodes and a secondary electron pair emitted from a secondary electron emission film disposed in the container. An SEM device or the like is used.

  The particle beam that has passed through the dose monitor 40 enters the beam position monitor 50, and the beam position monitor 50 monitors whether the beam position of the particle beam is at a predetermined position. As the beam position monitor 50, a matrix type in which the collecting electrodes are divided in a lattice shape, a multi-wire type in which the collecting electrodes are composed of a plurality of wires, a strip type in which the collecting electrodes are divided in a strip shape, or the like is used.

  A strip type beam position monitor 50 applied to the particle beam therapy system 1 is shown in FIG. As shown in FIG. 2, the beam position monitor 50 is composed of a plurality of strips 53 which are arranged in one axial direction and are not electrically connected to each other, and are set on the trajectory of the particle beam. 51. A plurality of collecting electrodes 51 are provided, and are sandwiched between high voltage electrodes each having a conductive surface while maintaining an interval of about 2 to 10 mm. When a high voltage is applied to the high-voltage electrode, an electric field is formed between the collection electrode 51 and the high-voltage electrode, and charges generated by the ionization action when the particle beam passes through the high-voltage electrode are collected. Collected by.

  The beam position monitor 50 detects a particle beam incident on a specific spot P in the sensitive region 52 of the collecting electrode 51 as a spot beam, and the particle beam scanned according to the irradiation position (X, Y) is detected. The beam position calculation is performed to monitor whether or not it is incident on the scheduled spot P. The beam position of the particle beam is obtained by converting the amount of collected charges collected by the strip 53 in the region where the spot P on which the particle beam is incident in the sensitive region 52 of the collecting electrode 51 into a digital signal, For example, the center of gravity of the particle beam is calculated by using a digital signal related to the collected charge.

  After passing through the ridge filter 60, the particle beam having passed through the beam position monitor 50 enters a range shifter 70 having an acrylic plate group composed of a plurality of acrylic plates 71 having different thicknesses, and the depth direction Z of the affected area 11 The position (see FIG. 1), that is, the irradiation position (Z) in the beam axis direction inside the affected part 11 is adjusted. The irradiation position (Z) is adjusted by adjusting the energy of the particle beam passing through the range shifter 70, that is, adjusting the range of the body by appropriately changing the combination of the acrylic plates 71 selected from the acrylic plate group. . The irradiation position (Z) is a method of adjusting the energy of the particle beam by adjusting the wavelength by electromagnetic action, in addition to using the range shifter 70 for adjusting the energy of the particle beam by passing the particle beam through the acrylic plate 71. Can also be adjusted.

  The dose peak (Bragg peak) of a single energy particle beam incident on the scanning electromagnet 20 shows a sharp shape at the affected area 11, but the energy of the particle beam is measured by the ridge filter 60 arranged on the upstream side of the range shifter 70. The distribution is expanded, and the dose peak in the affected area 11 is expanded according to the irradiation width in the particle beam axis direction.

  FIG. 3 is a flowchart showing a flow of irradiation control in the particle beam therapy system 1 of the first embodiment. The irradiation control in the particle beam therapy system 1 according to each step in this irradiation control will be described. Each step relates to a raster scanning irradiation method that does not stop the particle beam even when the irradiation position is changed.

  Step S1: As shown in FIG. 3, the affected area 11 in the subject 10 is divided into irradiation slices extending in a direction perpendicular to the particle beam axis, and one irradiation slice is selected from the divided irradiation slices. The If the deepest irradiation slice is selected, the incident energy of the particle beam and the thickness of the acrylic plate 71 of the range shifter 70 are selected according to the position of the deepest irradiation slice, and the process proceeds to step S2.

  Step S2: The number n of irradiation points and irradiation positions (Xi, Yi) [i = 1 to n] of the particle beam in the affected part 11 are set according to the shape of the affected part 11 in the deepest irradiated slice. The position of the scanning electromagnet 20 is adjusted according to the set irradiation position (Xi, Yi), and the process proceeds to Step 3.

  Step S3: The irradiation of the particle beam is started to the irradiation point at the irradiation position (Xi, Yi) set in Step S2 among the irradiation slices set in Step S1, and the process proceeds to Step S4.

  Step S4: The irradiation of the particle beam is continued until the irradiation dose to the irradiation point at the irradiation position (Xi, Yi) reaches the set dose set at the irradiation point, and the irradiation dose has reached the set dose. The process proceeds to step 5 at the timing when the dose expiration signal shown is generated. The irradiation dose at the irradiation position (Xi, Yi) on the irradiation slice is monitored by the dose monitor 40.

  Step S5: It is determined whether or not all irradiation points set in the irradiation slice have been irradiated. If it is determined that all irradiation points have been irradiated, the process proceeds to step S6. On the other hand, when the irradiation point which is not irradiated remains, it transfers to step S2. That is, the position of the scanning electromagnet 20 is changed and irradiation of the next irradiation position (Xi + 1, Yi + 1) on the same irradiation slice is started.

  Step S6: The irradiation of the particle beam is stopped, and the process proceeds to Step S7.

  Step S7: It is determined whether or not the irradiation slice for which all irradiation points have been irradiated is the final irradiation slice. If the irradiation slice is the final irradiation slice, the irradiation operation is terminated. On the other hand, if it is not the final irradiation slice, the process proceeds to step S1. That is, the next irradiation slice is selected, and the thickness of the acrylic plate 71 of the range shifter 70 is changed according to the irradiation position (Z) where the selected irradiation slice exists and the irradiation slice width. Control is repeated.

  The arrangement (irradiation pattern) of each irradiation position (X, Y) to be irradiated is described in the irradiation pattern file, and is sent to the irradiation control device 80 before the start of irradiation treatment. The irradiation pattern file includes a range shifter thickness corresponding to each irradiation position (X, Y) and an excitation current (for X direction driving and Y direction driving) for controlling the position of the scanning electromagnet 20 that determines the irradiation position (X, Y). ), Various management information such as a dose condition for generating a dose expiration signal.

  FIG. 4 is a block diagram showing a signal processing circuit 500 of the beam position monitor 50 of the first embodiment.

  As shown in FIG. 4, the signal processing circuit 500 of the beam position monitor 50 of the first embodiment includes an I / V converter 501, an amplifier 502, an ADC (A / D conversion) circuit 503, and a beam position calculation unit. As an FPGA 504 (Field Programmable Gate Array), a dose expiration signal transmission / reception unit 505, a CPU 506 as a beam position calculation control unit, an irradiation position information reception unit 507, and a storage unit 508.

  In the signal processing circuit 500, an I / V converter 501, an amplifier 502, and an ADC circuit 503 are provided for each strip 53 (see FIG. 2) constituting the collection electrode 51 of the beam position monitor 50, and each ADC circuit. 503 is connected to the FPGA 504. Further, a dose expiration signal transmitting / receiving unit 505 and a CPU 506 are connected to the FPGA 504, and an irradiation position information receiving unit 507 and a storage unit 508 are connected to the CPU 506. Hereinafter, one line composed of one strip 53 and an I / V converter 501, an amplifier 502, and an ADC circuit 503 connected to the strip 53 is referred to as a channel.

  In the signal processing circuit 500, the I / V converter 501 converts the current output indicating the amount of collected charges collected by the collecting electrode 51 of the beam position monitor 50 into a voltage signal through I / V conversion, and the amplifier 502 The I / V converted voltage signal is amplified.

  The ADC circuit 503 of the signal processing circuit 500 receives the A / D conversion start signal transmitted from the FPGA 504 of the signal processing circuit 500 and digitally converts the voltage signal amplified by the amplifier 502 in accordance with the amount of collected charge. A / D conversion into a signal to generate a digital signal related to the collected charge.

  The dose expiration signal transmission / reception unit 505 of the signal processing circuit 500 receives a dose expiration signal indicating that the dose irradiated to a certain irradiation point has reached the dose set for the irradiation point, and receives the received dose expiration signal. Is transmitted to the FPGA 504.

  The FPGA 504 of the signal processing circuit 500 outputs an A / D conversion start signal as a condition for causing each ADC circuit 503 to perform A / D conversion on the condition that the dose expiration signal transmission / reception unit 505 has received the dose expiration signal. Send. Further, a digital signal relating to the collected charge generated by each ADC circuit 503 of the signal processing circuit 500 is temporarily stored in a built-in memory (not shown), and the beam position of the particle beam is calculated using the stored digital signal. Perform beam position calculation. Note that a digital signal related to the collected charge is temporarily stored in the storage unit 508 of the signal processing circuit 500, and the FPGA 504 of the signal processing circuit 500 may perform a beam position calculation using the digital signal stored in the storage unit 508. Good.

  The irradiation position information receiving unit 507 of the signal processing circuit 500 receives irradiation position information indicating the position of the stop irradiation point to be irradiated next, immediately before the irradiation of the stop irradiation point.

  The CPU 506 of the signal processing circuit 500 transmits the irradiation position information received by the irradiation position information receiving unit 507 to the FPGA 504, and is used for the beam position calculation by the FPGA 504 and relates to the collected charges of all channels generated by the ADC circuit 503. The digital signal is transmitted to the storage unit 508.

  Regarding the configuration of the signal processing circuit 500 of the beam position monitor 50, an ADC circuit 503 is directly connected to the amplifier 502. However, a sample hold circuit is interposed between the amplifier 502 and the ADC circuit 503, and the signal is transmitted from the amplifier 502. The ADC circuit 503 may perform A / D conversion after holding the voltage signal for a certain time. By providing the sample and hold circuit, A / D conversion can be normally performed even if the input value of the voltage signal to the ADC circuit 503 changes, which is effective in improving the accuracy of beam position measurement.

  Next, the operation of the beam position monitor 50 will be described.

  Here, the background to the background art and the background to the present invention will be described before the description of the operation.

FIG. 5 is a block diagram showing a signal processing circuit 500a of a conventional beam position monitor. FIG. 6 is a timing chart relating to beam position measurement in the conventional particle beam therapy system 1.

  As shown in FIG. 5, a signal processing circuit 500a of a conventional beam position monitor (not shown) includes an I / V converter 501a, an amplifier 502a, an integrator 509a for each collection electrode channel of the beam position monitor. And an ADC circuit 503a.

  The signal processing circuit 500a of the conventional beam position monitor has three capacitors C having different capacities in order to ensure accuracy with respect to the variation in the integrated value of the collected charges based on the variation in irradiation time over two digits with respect to the irradiation position. Three capacitors C are switched and used. For this reason, it is difficult to reduce the size and cost of the beam position monitor by presenting a complicated circuit configuration.

  In addition, in the signal processing circuit 500a of the conventional beam position monitor, as shown in FIG. 6, on the condition that the dose expiration signal is generated, integration start / stop of the collected charge collected at the collection electrode of the beam position monitor is started. However, the integration process is performed continuously before and after the generation of the dose expiration signal. The charges accumulated in this way include not only the charge at the stop irradiation point of the particle beam, but also the excitation current X and the excitation current Y for driving the scanning electromagnet 20 as shown in FIG. Then, the charge during the scanning of the particle beam from the generation of the dose expiration signal to the generation of the next dose expiration signal is also included. For this reason, the accuracy of the beam position measurement is deteriorated due to the fact that the charges collected at the position in the middle of the scanning of the particle beam and the charges collected at the position where the scanning is completed are not accurately distinguished. In particular, when the distance from one stop irradiation point to the next stop irradiation point is large, the degree of decrease in the beam position measurement accuracy of the beam position monitor also increases.

  Accordingly, the beam position monitor 50 for the particle beam therapy system according to the present embodiment has been made to meet the demand for improved beam position measurement accuracy without adopting the configuration of the conventional beam position monitor and the principle of beam position measurement. . In the beam position monitor 50 for the particle beam therapy system, the beam position calculation is performed without collecting the charges as much as possible after the dose expiration signal is generated until the next dose expiration signal is generated. Not only the accuracy of position measurement is improved, but the configuration of the signal processing circuit is simplified, and the beam position monitor can be reduced in size and cost. Hereinafter, the operation of the beam position monitor for the particle beam therapy system according to the first embodiment will be described.

  FIG. 7 is a timing chart relating to beam position measurement in the particle irradiation therapy apparatus 1 of the first embodiment.

  In the particle beam therapy system 1, when the irradiation dose for the irradiation position (X, Y) of the affected part 11 reaches a set value for the irradiation position (X, Y), a dose expiration signal is generated. When the dose expiration signal is generated, the excitation current X and the excitation current Y for driving the scanning electromagnet 20 are started to be changed at the timing when the dose expiration signal is generated, as shown in FIG. (X, Y) starts to be changed. The exciting current X is used for changing the irradiation position (X) of the particle beam, and the exciting current Y is used for changing the irradiation position (Y) of the particle beam. When the excitation current X and the excitation current Y reach the set values, the excitation current X and the excitation current Y are held at constant values, and an irradiation position setting completion signal is generated.

  A dose expiration signal that is a condition for starting to change the irradiation position (X, Y) is received by the dose expiration signal transmission / reception unit 505 of the signal processing circuit 500, and the received dose expiration signal is transmitted to the FPGA 504 of the signal processing circuit 500. The

  When the FPGA 504 of the signal processing circuit 500 receives the dose expiration signal, an A / D conversion start signal is transmitted from the FPGA 504 to the ADC circuit 503 connected to each channel of the signal processing circuit 500.

  At the timing when each ADC circuit 503 receives the A / D conversion signal, the voltage signal generated by the I / V converter 501 of the signal processing circuit 500 is a digital signal corresponding to the amount of electric charge collected by each ADC circuit 503. A / D conversion is performed and a digital signal related to the collected charge is generated.

  The digital signal generated by each ADC circuit 503 is transmitted to the FPGA 504 of the signal processing circuit 500 and temporarily stored in the built-in memory of the FPGA 504. The dose expiration signal is used as a timing signal indicating that the particle beam scanned from the stop irradiation point to the next stop irradiation point is not scanned, and the collected charge generated by the A / D conversion of each ADC circuit 503 The digital signal relating to is related to the collected charge when the particle beam is not in the middle of scanning.

  On the other hand, the irradiation position information receiving unit 507 of the signal processing circuit 500 performs irradiation position information determined in the treatment plan, that is, information indicating the position of the stop irradiation point to be irradiated next among the irradiation positions where each irradiation point exists. Is read for each irradiation point immediately before the irradiation.

  The irradiation position information received by the irradiation position information receiving unit 507 is referred to by the CPU 506 of the signal processing circuit 500, and the particle beam beam scanned by the CPU 506 to the stop irradiation point to be irradiated next is incident on the collecting electrode 51. The strip 53 is discriminated from the position or the spot P located around the incident position.

  The CPU 506 limits the digital signal relating to the collected charge used for the beam position calculation by the FPGA 504 to the digital signal generated by the ADC circuit 503 connected to the discriminated strip 53. That is, in the signal processing circuit 500, the spot P where the particle beam should be incident in the sensitive region 52 of the collecting electrode 51 is expected before irradiation of the irradiation position (X, Y).

  The FPGA 504 uses a digital signal relating to the collected charge generated by the ADC circuit 503 connected to the channel around the position of the spot P where the particle beam is expected to be incident among all the strips 53 constituting the collecting electrode 51. Perform beam position calculation.

  Note that the storage unit 508 connected to the CPU 506 can store digital signals of collected charges for all channels. However, the spot P or the spot that is expected to receive a particle beam under the signal processing control by the CPU 506 is used. A digital signal generated by the ADC circuit 503 connected to a channel around P is selectively transmitted and stored. Digital signals generated by the ADC circuit 503 connected to other channels are not transmitted / stored in the storage unit 508. That is, among the digital signals related to the collected charges generated by the ADC circuit 503, the digital signals related to the collected charges used for the beam position calculation by the FPGA 504 are selectively transmitted to and stored in the storage unit 508, and the beam position calculation by the FPGA 504 is performed. Digital signals relating to collected charges that are not used in the storage are not transmitted to or stored in the storage unit 508.

  Next, the effect of the beam position monitor 50 will be described.

In the beam position monitor 50,
(1) A plurality of stop irradiation points set on the subject 10 are irradiated with a particle beam, and when the dose irradiated to the stop irradiation point reaches a set value, the irradiation position of the particle beam is When the particle beam is incident on the collection electrode 51 provided in the particle beam therapy apparatus 1 as a particle beam therapy apparatus that scans the stop irradiation point and set on the trajectory of the particle beam. In the beam position monitor 50 including the signal processing circuit 500 that collects the charge generated by the ionization action of the beam as a collected charge and performs the beam position calculation for specifying the beam position using the collected charge, the signal processing circuit 500 The I / V converter 501 generates a voltage signal corresponding to the current output by performing I / V conversion on the current output generated by the ionization action at the collecting electrode 51, and the voltage signal generated by the I / V converter 501. Receiving input and collecting charge And a timing signal for receiving a signal generated in a non-scanning state in which the particle beam scanned from the stop irradiation point to the next stop irradiation point is not scanned as a timing signal. At the timing when the transmission / reception unit and the timing signal transmission / reception unit receive the timing signal, the digital signal related to the collected charge generated by the digital signal generation circuit is received and the received digital signal related to the collected charge is used. FPGA 504 for performing the beam position calculation.

  For this reason, the collected charges collected during the scanning of the irradiation position of the particle beam from the collected charges collected by the collecting electrode 51 and used for the beam position calculation are eliminated, and a decrease in accuracy of beam position measurement can be avoided. .

  In addition, the signal processing circuit 500 of the beam position monitor 50 is configured by using a plurality of capacitors having different capacities in order to accurately measure the amount of collected charge according to the variation in the amount of collected charge based on the variation in irradiation time. There is no need to configure. Therefore, the signal processing circuit 500 and the beam position monitor 50 can be simplified and the cost can be reduced.

  That is, in the beam position monitor 50 for the particle beam therapy system, the beam position of the particle beam can be accurately measured even in the raster scanning method, and the size and cost of the beam position monitor can be reduced.

  (2) The signal processing circuit 500 is interposed between the I / V converter 501 and the digital signal generation circuit, and amplifies a voltage signal generated by the I / V converter and input to the digital signal generation circuit. An amplifier 502 is included. Therefore, even if the ionization effect in the collecting electrode 51 due to the incidence of the particle beam is weak, a digital signal related to the collected charge can be stably generated. Therefore, the beam position of the particle beam can be specified with high accuracy.

  (3) The digital signal generation circuit includes an ADC circuit 503 that performs A / D conversion on the voltage signal generated by the I / V converter 501, and generates a digital signal related to the collected charge according to the magnitude of the voltage signal. . Therefore, the beam position calculation can be executed by a computer.

  (4) The timing signal transmission / reception unit receives a dose expiration signal indicating that the dose irradiated to the stop irradiation point of the subject 10 has reached the dose set for the stop irradiation point, as the timing signal, The dose expiration signal transmission / reception unit 505 transmits the received dose expiration signal to the FPGA 504. The FPGA 504 digitally collects the collected charges with respect to the digital signal generation circuit (for example, the ADC circuit 503) at the timing of receiving the dose expiration signal. Accept the generation of the signal and receive the generated digital signal. For this reason, it is easy to avoid a decrease in measurement accuracy of the beam position due to the electric quantity of the collected charge integrated during scanning of the irradiation position of the particle beam. Therefore, the effect of (1) becomes steady.

  (5) The collection electrode 51 of the beam position monitor 50 is configured by an array of strips 53 as a plurality of independent collection electrode elements, and the I / V converter 501 of the signal processing circuit 500 is provided for each of the strips. The current output generated by the ionization action in each strip is I / V converted, and the digital signal generation circuit of the signal processing circuit 500 is provided for each I / V converter 501, and each I / V converter The signal processing circuit 500 is configured to receive the input of the voltage signal generated by the 501 and generate a digital signal related to the collected charge, and the signal processing circuit 500 is a position where the particle beam to be scanned is incident on the stop irradiation point to be irradiated next. Or the strip 53 around the incident position is discriminated, and the digital signal generated by the digital signal generation circuit provided for the discriminated strip 53 is detected with respect to the FPGA 504 of the signal processing circuit 500. A CPU 506 that permits beam position calculation using a tall signal and prohibits beam position calculation using a digital signal generated by a digital signal generation circuit provided for a strip 53 other than the identified collection electrode element.

  Therefore, it is possible to shorten the time required for each process of transmission, storage, and extraction of a digital signal used for beam position calculation with respect to the internal memory and storage unit 508 provided in the FPGA 504 of the signal processing circuit 500. Therefore, the accuracy of beam position calculation can be improved. Specifically, when the irradiation time of the irradiation point is short, the data processing failure that each process such as transmission and storage of the digital signal generated with respect to each irradiation point to the storage unit 508 or the like cannot be caught up. Is a problem. However, in the general particle beam irradiation treatment 1, among the several tens channels included in the collection electrode 51 of the beam position monitor 50, there are many channels that are effective at one time. Focusing on this point, the signal processing circuit 500 of the beam position monitor 50 discriminates the channel, that is, the strip 53 corresponding to the spot on which the particle beam is incident, and relates to the collecting electrode collected by the discriminated strip 53. Since it is transmitted and stored in the storage unit 508 of the signal processing circuit 500 only for digital signals, the problem of data processing drop can be reduced, and the accuracy of beam position calculation can be improved.

  (6) The signal processing circuit 500 includes an irradiation position information receiving unit 507 that receives irradiation position information indicating the position of the stop irradiation point to be irradiated next before irradiation of the stop irradiation point to be irradiated next. Therefore, the effect (5) can be easily realized.

  (7) The signal processing circuit 500 selectively stores the digital signal related to the collected charge used for the beam position calculation of the FPGA 504 among the digital signals related to the collected charge generated by the digital signal generation circuit, and calculates the beam position of the FPGA 504. The storage unit 508 does not store digital signals related to collected charges that are not used in the storage. Therefore, the time required for transmission / storage of the digital signal to / from the storage unit 508 can be shortened, and the effect (5) can be improved. As a method for selecting a digital signal to be stored, for example, there is a method for selecting a peripheral channel of a beam incident position obtained by beam position calculation. However, a high-speed digital signal can be selected by acquiring irradiation position information in advance. Is possible.

(Second Embodiment)
The second embodiment is an example in which other signal processing circuit elements are added to the signal processing circuit 500 of the beam position monitor 50 of the first embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted. A configuration obtained by changing or adding the configuration of the first embodiment will be described with “A” added to the end of the reference numeral.

  FIG. 8 is a block diagram showing a signal processing circuit 500A of the beam position monitor 50A of the second embodiment.

  As shown in FIG. 8, the signal processing circuit 500A of the beam position monitor 50A includes an integrator 509A as a slice irradiation dose integrator, a sample hold circuit 510A, and an ADC circuit, in addition to the signal processing circuit 500 of the first embodiment. 503A, FPGA 504A, and irradiation slice switching signal receiver 511A. A signal processing circuit corresponding to the signal processing circuit 500 of the first embodiment is referred to as a first signal line, and a signal processing circuit added to the first signal line is referred to as a second signal line.

  The second signal line of the signal processing circuit 500A is provided by branching from the output side of the amplifier 502 of the first signal line provided in each strip 53 of the collecting electrode 51 of the beam position monitor 50A. One channel is formed by the signal line. The irradiation slice switching signal receiving unit 511 is connected to the FPGA 504A of the second signal line.

  In the signal processing circuit 500A, the integrator 509A of the second signal line receives the next irradiation slice switching signal when the irradiation slice switching signal transmission / reception unit 511A receives the irradiation slice switching signal. Until then, the amount of electricity related to the collected charge collected in each strip 53 located at the spot P where the particle beam enters at the collecting electrode 51 is integrated.

  The sample and hold circuit 510A for the second signal line holds the voltage signal sent from the integrator 509A for a predetermined time. The sample hold circuit 510A is not necessarily required, but by providing the sample hold circuit 510A, an input of a voltage signal generated by the I / V converter 501 of the first signal line and input to the ADC circuit 503A of the second signal line. Even if the value changes, A / D conversion can be performed normally, which is effective in improving the accuracy of beam position measurement.

  The irradiation slice switching signal receiving unit 511A of the second signal line is a condition for starting irradiation of the irradiation slice of the subject, and switches irradiation slices when irradiation of a plurality of stop irradiation points set in the irradiation slice is completed. An irradiation slice switching signal as a condition is received.

  Next, the operation of the beam position monitor 50A will be described.

  The beam position measurement by the beam position monitor 50A is performed according to the timing shown in FIG. 7 as in the first embodiment. On the other hand, in the beam position monitor 50A, when the irradiation slice switching signal for switching the irradiation slice is generated, the generated irradiation slice switching signal is transmitted to the irradiation slice switching signal transmission / reception unit 511 in the second signal line in the signal processing circuit 500A. Is transmitted to the FPGA 504A.

  At the timing when the FPGA 504A receives the irradiation slice switching signal, the voltage signal related to the collected charge generated by the I / V converter 501 of the first signal line under the control of the FPGA 504A and integrated by the integrator 509A of the second signal line. Is cleared (discharge is turned on), and the voltage signal related to the collected charge generated by the I / V converter 501 is started to be accumulated by the integrator 509A (discharge is turned off).

  In the second signal line, the voltage signal related to the collected charge integrated by the integrator 509A is temporarily held by the sample hold circuit 510A, and then A / D converted by the ADC circuit 503A to generate a digital signal related to the collected charge. . The generated digital signal is input to the FPGA 504A of the second signal line, and the dose integration calculation applied to each irradiation slice is performed. Then, at the timing when the next irradiation slice switching signal is generated, the same dose integration calculation is performed on the next irradiation slice. Since other operations are the same as those of the first embodiment, description thereof is omitted.

  Next, the effect of the beam position monitor 50A will be described.

  In the beam position monitor 50A, in addition to the effects (1) to (7) of the first embodiment, the following effects can be obtained.

  (8) When the subject 10 is divided into a plurality of irradiation slices, the signal processing circuit 500A has a condition for starting the irradiation of the irradiation slices, and all the irradiations of the plurality of stop irradiation points set in the irradiation slices are performed. When the irradiation slice switching signal transmission / reception unit 511A receives an irradiation slice switching signal, and when the irradiation slice switching signal transmission / reception unit 511A receives the irradiation slice switching signal, the irradiation slice switching signal is received. Until the transmission / reception unit 511A receives the next irradiation slice switching signal, the transmission / reception unit 511A includes an integrator 509A that integrates irradiation doses at a plurality of stop irradiation points set in the irradiation slice.

  Therefore, the total sum of irradiation doses from the first irradiation point to the last irradiation point set in the irradiation slice by the treatment plan can be acquired. Therefore, it is possible to meet the demands of doctors and technicians who operate particle beam therapy equipment that want to check not only the irradiation position but also the irradiation dose in confirming whether irradiation is performed normally, and highly reliable particles Line therapy is realized.

  In addition, when the irradiation is temporarily stopped or the irradiation part is shifted during irradiation of one irradiation slice as in the case of respiratory synchronization irradiation (for example, see Non-Patent Document 1), the irradiation dose for one irradiation slice is integrated. At this time, for example, it is desirable to reduce the amplification factor of the amplifier 502 so that the voltage signal related to the collected charge is not input to the integrator 509A of the second signal line.

  Here, it becomes a condition for starting irradiation of the irradiation slice, and when irradiation of the stop irradiation points included in the irradiation pattern set in the irradiation slice is completed, an irradiation pattern switching signal that is a condition for switching the irradiation pattern is generated. The irradiation pattern switching signal transmission / reception unit that receives the irradiation pattern switching signal instead of the irradiation slice switching signal transmission / reception unit 511A, and when the irradiation pattern switching signal transmission / reception unit receives the irradiation pattern switching signal, You may make it provide the irradiation pattern irradiation dose integrator which integrates the irradiation dose of the stop irradiation point contained in an irradiation pattern until a part receives the next irradiation pattern switching signal. Also with this configuration, it is possible to obtain the sum of irradiation doses for the same or different irradiation patterns of the same irradiation slice, and the same effect as in (8) can be obtained.

(Third embodiment)
The third embodiment is an example in which the configuration of the signal processing circuit 500 of the beam position monitor 50 of the first embodiment is changed. In addition, the same structure as 1st Embodiment attaches | subjects the same code | symbol to a corresponding structure, abbreviate | omits description, and the structure which changed or added the structure of 1st Embodiment attaches "B" to the code | symbol end. To explain.

  FIG. 9 is a block diagram showing a signal processing circuit 500B of the beam position monitor 50B of the third embodiment.

  As shown in FIG. 9, the signal processing circuit 500B of the beam position monitor 50B is provided with a comparator circuit 512B in place of the ADC circuit 503 in the signal processing circuit 500 of the first embodiment. The comparator circuit 512B of the signal processing circuit 500B is provided for each of the I / V converters 501 provided for each strip 53 of the collecting electrode 51 of the beam position monitor 50B, and is connected to the FPGA 504 of the signal processing circuit 500B. The

  The comparator circuit 512B of the signal processing circuit 500B includes an effective digital signal indicating that the voltage corresponding to the collected charge generated by the I / V converter 501 of the signal processing circuit 500B exceeds a preset reference voltage level, and I Two determination digital signals composed of invalid digital signals indicating that the voltage signal corresponding to the collected charge generated by the / V converter 501 does not exceed the reference voltage level are generated, and the generated determination digital signal is signal-processed Transmit to the FPGA 504 of the circuit 500B. As the determination digital signal, for example, “1” is assigned to the valid digital signal and “0” is assigned to the invalid digital signal using the minimum information unit handled by the computer.

  Then, the FPGA 504 of the signal processing circuit 500B has a position where the particle beam is incident on the position of the strip provided with the comparator circuit 512 that generates the effective digital signal among the strips 53 constituting the collecting electrode 51 of the beam position monitor 50B. The beam position is calculated with the content of

  Next, the operation of the beam position monitor 50B will be described.

  The beam position measurement in the signal processing circuit 500B of the beam position monitor 50B is performed according to the timing shown in FIG. 7, as in the first embodiment. However, when the dose expiration signal is generated, a digital signal for determination is generated by the comparator circuit 512B of the signal processing circuit 500B instead of generating a digital signal related to the collected charge by the ADC circuit 503 of the first embodiment.

  The comparator circuit operation signal is transmitted from the FPGA 504 to the comparator circuit 512B at the timing when the dose expiration signal transmission / reception unit 505 of the signal processing circuit 500B receives the dose expiration signal and the dose expiration signal is transmitted to the FPGA 504 of the signal processing circuit 500B. . When the comparator circuit 512B receives the comparator circuit operation signal, a determination digital signal is transmitted from the comparator circuit 512B to the FPGA 504.

  When the FPGA 504 receives the determination digital signal from the comparator circuit 512B in the signal processing circuit 500B, the beam position calculation using the received determination digital signal is performed in the FPGA 504. That is, in the FPGA 504, it is determined that the position of the strip connected to the comparator circuit 512B that has generated the effective digital signal among the strips 53 constituting the collecting electrode 51 of the beam position monitor 50B is the spot where the particle beam is incident. . Note that the determination digital signal received by the FPGA 504 of the signal processing circuit 500B is temporarily stored in the internal memory of the FPGA 504, and the FPGA 504 performs a beam position calculation using the stored determination digital signal. Since other operations are the same as those of the first embodiment, description thereof is omitted.

  Next, the effect of the beam position monitor 50B for the particle irradiation apparatus will be described.

In the beam position monitor 50B of the third embodiment, the following effects can be obtained in addition to the effects (1), (2), (4) to (7) of the first embodiment.

  (9) The collection electrode 51 of the beam position monitor 50B is configured by an array of strips 53 as a plurality of independent collection electrode elements, and the I / V converter 501 is provided for each of the strips 53. The current output generated by the ionization action in 53 is I / V converted, and a digital signal generation circuit is provided for each I / V converter 501, and the voltage signal generated by each I / V converter 501 is A comparator that receives the input and generates two digital signals for determination: a valid digital signal indicating that the received voltage signal exceeds the reference voltage level and an invalid digital signal indicating that the voltage signal does not exceed the reference voltage level The FPGA 504 is configured to be able to input a determination digital signal generated by each comparator circuit 512B, and an effective digital signal is generated. The used beam position calculation is performed, and the beam position calculation using the invalid digital signal is not performed.

  Therefore, in the execution of the beam position calculation, signal processing is performed as compared with a case where a digital signal corresponding to the amount of electricity of collected charges generated by A / D converting the voltage signal generated by the I / V converter 501 is used. The data size (number of bits) handled by the FPGA 504 of the circuit 500B can be reduced, and the calculation time can be shortened. Therefore, the processing speed of beam position calculation can be increased.

(Fourth embodiment)
The fourth embodiment is an example in which other signal processing circuit elements are added to the signal processing circuit 500B of the beam position monitor 50B of the third embodiment. In addition, the same structure as 3rd Embodiment attaches | subjects the same code | symbol to a corresponding structure, abbreviate | omits description, The structure which changed or added the structure of 3rd Embodiment attaches "C" to the code | symbol end. To explain.

  FIG. 10 is a block diagram showing a signal processing circuit 500C of the beam position monitor 50C of the fourth embodiment.

  As shown in FIG. 10, the signal processing circuit 500C in the beam position monitor 50C includes an integrator 509C as a slice irradiation dose integrator, a sample hold circuit 510C, and an ADC circuit in addition to the signal processing circuit 500B of the third embodiment. 503C, FPGA 504C, and irradiation slice switching signal receiver 511C. Hereinafter, a signal processing circuit corresponding to the signal processing circuit 500 of the third embodiment is referred to as a first signal line, and a signal processing circuit added to the first signal line is referred to as a second signal line.

  In the signal processing circuit 500C, when the irradiation slice switching signal transmission / reception unit 511C receives the irradiation slice switching signal, the irradiation slice switching signal transmission / reception unit 511C receives the next irradiation slice switching signal. Until then, the amount of electricity related to the collected charge collected in each strip 53 located at the spot P where the particle beam enters at the collecting electrode 51 is integrated.

  The sample and hold circuit 510C for the second signal line holds the voltage signal sent from the integrator 509C for a predetermined time. Although the sample hold circuit 510C is not necessarily required, by providing the sample hold circuit 510C, an input of a voltage signal generated by the I / V converter 501 of the first signal line and input to the ADC circuit 503C of the second signal line is provided. Even if the value changes, A / D conversion can be performed normally, which is effective in improving the accuracy of beam position measurement.

  The irradiation slice switching signal receiving unit 511C of the second signal line is a condition for starting irradiation of the irradiation slice of the subject 10, and when irradiation of a plurality of stop irradiation points set in the irradiation slice is completed, the irradiation slice is selected. An irradiation slice switching signal as a switching condition is received.

  Next, the operation of the beam position monitor 50C will be described.

  The beam position measurement by the signal processing circuit 500C of the beam position monitor 50C is performed according to the timing shown in FIG. 7, as in the first embodiment. In the beam position monitor 50C, when an irradiation slice switching signal for switching irradiation slices is generated, the irradiation slice switching signal is received by the irradiation slice switching signal transmission / reception unit 511C of the second signal line and transmitted to the FPGA 504C.

  Collection that is generated by the I / V converter 501 of the first signal line and integrated by the integrator 509C of the second signal line under the control of the FPGA 504C at the timing when the FPGA 504C of the second signal line receives the irradiation slice switching signal The voltage signal related to the charge is cleared (discharge ON), and the voltage signal related to the collected charge generated by the I / V converter 501 is started to be integrated by the integrator 509C (discharge OFF).

  In the second signal line, the voltage signal related to the collected charge accumulated by the integrator 509C is temporarily held by the sample hold circuit 510C, and then A / D converted by the ADC circuit 503C to generate a digital signal related to the collected charge. . The generated digital signal is input to the FPGA 504C of the second signal line, and the dose integration calculation applied to each irradiation slice is performed. Then, at the timing when the next irradiation slice switching signal is generated, the same dose integration calculation is performed on the next irradiation slice. Since other operations are the same as those of the third embodiment, description thereof is omitted.

  Next, the effect of the beam position monitor 50C will be described.

  In the beam position monitor 50C, in addition to the effects of (1), (2), (4) to (7) of the first embodiment and (9) of the third embodiment, the following effects can be obtained. Can do.

  (10) When the subject 10 is divided into a plurality of irradiation slices, the signal processing circuit 500C becomes a condition for starting irradiation of the irradiation slices, and all of the irradiations at the plurality of stop irradiation points set in the irradiation slices are performed. When the irradiation slice switching signal transmission / reception unit 511C receives an irradiation slice switching signal, and when the irradiation slice switching signal transmission / reception unit 511C receives the irradiation slice switching signal, the irradiation slice switching signal transmission / reception is performed. Until the unit 511C receives the next irradiation slice switching signal, it has an integrator 509C for integrating the irradiation doses at a plurality of stop irradiation points set in the irradiation slice.

  Therefore, the total sum of irradiation doses from the first irradiation point to the last irradiation point set in the irradiation slice by the treatment plan can be acquired. Therefore, it is possible to meet the demands of doctors and technicians who operate particle beam therapy equipment that want to check not only the irradiation position but also the irradiation dose in confirming whether irradiation is performed normally. Particle beam therapy is realized.

  In addition, when the irradiation is temporarily stopped or the irradiation part is shifted during irradiation of one irradiation slice as in the case of respiratory synchronization irradiation (for example, see Non-Patent Document 1), the irradiation dose for one irradiation slice is integrated. At this time, for example, it is desirable to reduce the amplification factor of the amplifier 502 so that the voltage signal related to the collected charge is not input to the integrator 509C of the second signal line.

  Here, it becomes a condition for starting irradiation of the irradiation slice, and when irradiation of the stop irradiation points included in the irradiation pattern set in the irradiation slice is completed, an irradiation pattern switching signal that is a condition for switching the irradiation pattern is generated. The irradiation pattern switching signal transmission / reception unit that receives the irradiation pattern switching signal instead of the irradiation slice switching signal transmission / reception unit 511C, and when the irradiation pattern switching signal transmission / reception unit receives the irradiation pattern switching signal, You may make it provide the irradiation pattern irradiation dose integrator which integrates the irradiation dose of the stop irradiation point contained in an irradiation pattern until a part receives the next irradiation pattern switching signal. Also with this configuration, it is possible to obtain the sum of irradiation doses for the same or different irradiation patterns of the same irradiation slice, and the same effect as in (10) can be obtained.

(Fifth embodiment)
The fifth embodiment is an example in which the signal processing circuit 500 of the beam position monitor 50 of the first embodiment is changed. In addition, the same structure as 1st Embodiment attaches | subjects the same code | symbol to a corresponding structure, abbreviate | omits description, and the structure which changed or added the structure of 1st Embodiment attaches "D" to the code | symbol end. To explain.

  FIG. 11 is a block diagram showing a signal processing circuit 500D of the beam position monitor 50D of the fifth embodiment.

  As shown in FIG. 11, the signal processing circuit 500D of the beam position monitor 50D has a comparator circuit 512D. The irradiation position information receiving unit 505 included in the signal processing circuit 500 of the beam position monitor 50 of the first embodiment is not included. The comparator circuit 512D of the signal processing circuit 500D is provided for each of the amplifiers 502 connected to the output side of the I / V converter 501.

  The comparator circuit 512D includes an effective digital signal indicating that the voltage corresponding to the collected charge generated by the I / V converter 501 of the signal processing circuit 500D exceeds a reference voltage level as a preset reference value, and I / V Two determination digital signals composed of invalid digital signals indicating that the voltage signal corresponding to the collected charge generated by the V converter 501 does not exceed the reference voltage level are generated, and the generated determination digital signals are transmitted to the FPGA 504. To do. As the determination digital signal, for example, “1” is assigned to the valid digital signal and “0” is assigned to the invalid digital signal using the minimum information unit handled by the computer.

  The FPGA 504 of the signal processing circuit 500B receives the digital signal related to the collected charge, the digital signal for determination received from the comparator circuit 512D among the digital signals related to the collected charge generated by the ADC circuit 503 of the signal processing circuit 500. A beam position is calculated using the selected digital signal.

  Next, the operation of the beam position monitor 50D will be described.

  The beam position measurement by the signal processing circuit 500D of the beam position monitor 50D is performed at the timing shown in FIG. 7 as in the first embodiment.

  In the signal processing circuit 500D of the beam position monitor 50D, the voltage signal generated by the I / V converter 501 is A / D converted by the ADC circuit 503 to generate a digital signal related to the collected charge. In parallel with the generation, it is determined whether the voltage signal exceeds the reference voltage level by the comparator circuit 512D. The result of the determination is generated as a determination digital signal. The generated digital signal and determination digital signal are input to the FPGA 504 of the signal processing circuit 500D.

  The FPGA 504 selects a digital signal related to the collected charge, which is an effective digital signal from the digital signal related to the collected charge generated by the ADC circuit 503, and receives the selected digital signal. The used beam position calculation is performed. Since other operations are the same as those of the first embodiment, description thereof is omitted.

  Next, the effect of the beam position monitor 50D for the particle irradiation apparatus will be described.

  In the beam position monitor 50D, the following effects can be obtained in addition to the effects (1) to (3) and (7) of the first embodiment.

  (11) The collecting electrode 51 of the beam position monitor 50D is constituted by an array of strips 53 as a plurality of independent collecting electrode elements, and an I / V converter 501 is provided for each of the strips 53. The current output generated by the ionization action in 53 is subjected to I / V conversion, and a digital signal generation circuit (for example, ADC circuit 503) is provided for each I / V converter 501, and each I / V converter 501 is provided. The signal processing circuit 500 is provided for each of the I / V converters 501, and receives the input of the voltage signal generated by the signal generator. The signal processing circuit 500 is provided for each of the I / V converters 501, respectively. Valid digital signal indicating that the voltage signal generated by 501 and input to each digital signal generation circuit exceeds the reference voltage level, and invalid indicating that the voltage signal does not exceed the reference voltage level A comparator circuit that generates two determination digital signals of the digital signal is provided. The FPGA 504 is provided so that the determination digital signal generated by each comparator circuit 512D can be input. The comparator circuit 512D that generates the effective digital signal includes Generated by the digital signal generation circuit of the strip 53 provided with the comparator circuit 512D that performs the beam position calculation using the digital signal related to the collected charge generated by the digital signal generation circuit of the provided strip 53 and generates the invalid digital signal. The beam position calculation using the digital signal related to the collected charge is not performed.

  Therefore, it is not necessary to provide the irradiation position information receiving unit 507 as in the first embodiment, and the time required for the irradiation position information reception processing and the digital signal discrimination processing regarding the collected charge can be shortened, and the beam position calculation can be speeded up. . Further, since the irradiation position information receiving unit 507 is not necessary as in the first embodiment, the configuration of the particle beam therapy system 1 can be simplified.

  As described above, the beam position monitor for the particle beam therapy system according to the present invention has been described based on the first to fifth embodiments, but the specific configuration is not limited to these embodiments. Design changes and additions are allowed without departing from the spirit of the invention according to each claim of the claims.

  In the present embodiment, an example in which an A / D conversion start signal is transmitted to the ADC circuit of the signal processing circuit at the timing when the dose expiration signal is generated, and a voltage signal related to the collected charge is converted into a digital signal related to the collected charge is shown. It was. However, a digital signal generation start signal by the digital signal generation circuit, for example, a timing signal for generating an A / D conversion start signal by the ADC circuit is supplied to a scanning electromagnet that is driven to scan the irradiation position of the particle beam. An irradiation position setting completion signal indicating that the excitation current for driving the scanning electromagnet has become constant may be used.

  When the timing signal for generating the A / D conversion start signal is the irradiation position setting completion signal, the dose expiration signal transmission / reception unit is replaced with the irradiation position setting completion signal transmission / reception unit. That is, the timing signal transmission / reception unit of the signal processing circuit is supplied to a scanning electromagnet that is driven so as to scan the irradiation position of the particle beam, and the irradiation position indicating that the excitation current that drives the scanning electromagnet becomes constant It is configured by an irradiation position setting completion signal transmitting / receiving unit that receives a setting completion signal and transmits the received irradiation position setting completion signal to the FPGA, and the FPGA receives the irradiation position setting completion signal at the timing of receiving the irradiation position setting completion signal. Configured to receive the generated digital signal by allowing the generation of the digital signal related to the collected charge.

  Even with this configuration, the beam position of the particle beam can be accurately measured and the beam position monitor can be reduced in size and cost even in the raster scanning method.

  FIG. 12 is a timing chart relating to beam position measurement in the particle irradiation therapy apparatus when the timing signal for generating the A / D conversion start signal is used as the irradiation position setting completion signal.

  As shown in FIG. 12, the irradiation position setting completion signal is generated when the excitation current X and the excitation current Y for driving the scanning electromagnet reach the set values and become constant. The A / D conversion start signal may be generated with a certain delay time in the timing.

  When the irradiation position setting completion signal is used as the timing signal for generating the A / D conversion start signal, the A is applied to the ADC circuit more than when the dose expiration signal is used as the timing signal for generating the A / D conversion start signal. The / D conversion start signal can be input at an early timing. Therefore, the interlock operation when an abnormality occurs can be speeded up, and the safety of the particle beam therapy system can be improved.

  The irradiation position setting completion signal is generally generated by measuring the current value of the scanning magnet power supply, so it is easily affected by ripples and overshoots in the current waveform, and the generation timing of the irradiation position setting completion signal is unstable. There is a risk. Therefore, when the irradiation position setting completion signal is used as the timing signal for generating the A / D conversion start signal, it is preferable to ensure the stability of the current waveform of the scanning electromagnet power supply 30.

  Needless to say, when a comparator circuit is used instead of the ADC circuit, the irradiation position setting completion signal may be used as a timing signal for generating a comparator circuit operation signal.

  Regarding the irradiation position information receiving method by the irradiation position information receiving unit, for example, the irradiation position information set in one irradiation slice is read and stored in the storage unit of the signal processing circuit, and corresponds to each irradiation point irradiation. You may make it read the irradiation position information to perform.

  In this embodiment, the beam position calculation is performed by the FPGA of the signal processing circuit. However, the FPGA only controls the ADC circuit and extracts the digital signal generated by the ADC circuit, and performs the beam position calculation. You may make it carry out by CPU of a signal processing circuit. In this case, regarding the configuration of the signal processing circuit, an element such as a gate array that can realize a desired logic circuit by changing a wiring pattern can be used instead of the FPGA.

Schematic of the particle beam therapy system provided with the beam position monitor of the first embodiment. Schematic of the beam position monitor of the first embodiment. The flowchart which shows the flow of irradiation control in the particle beam therapy system of 1st Embodiment. The block diagram which shows the signal processing circuit of the beam position monitor of 1st Embodiment. The block diagram which shows the signal processing circuit of the conventional beam position monitor. The timing chart in connection with the beam position measurement in the conventional particle beam therapy system. The timing chart in connection with the beam position measurement in the particle irradiation therapy apparatus of 1st Embodiment. The block diagram which shows the signal processing circuit of the beam position monitor of 2nd Embodiment. The block diagram which shows the signal processing circuit of the beam position monitor of 3rd Embodiment. The block diagram which shows the signal processing circuit of the beam position monitor of 4th Embodiment. The block diagram which shows the signal processing circuit of the beam position monitor of 5th Embodiment. The timing chart in connection with the beam position measurement in the particle irradiation treatment apparatus when the timing signal for generating the A / D conversion start signal is the irradiation position setting completion signal.

Explanation of symbols

1 Particle beam therapy system (particle beam therapy system)
10 Subject
11 affected area
50, 50A, 50B, 50C, 50D Beam position monitor
51 Collection electrode
53 Collection electrode strip (collection electrode element)
501 I / V converter
503, 503A, 503C ADC circuit
504, 504A, 504C FPGA (beam position calculator)
505 Dose expiration signal transmitter / receiver
506 CPU (beam position calculation control unit)
507 Irradiation position information receiver
508 memory
509A, 509C integrator (slice irradiation dose integrator)
511 Irradiation slice switching signal transmitter / receiver
512, 512B, 512D comparator circuit

Claims (23)

A plurality of stop irradiation points set on the subject are irradiated with a particle beam, and when the dose irradiated to the stop irradiation point reaches a set value, the irradiation position of the particle beam is set to the next stop irradiation point. A collection electrode that is provided in a scanning particle beam therapy system and is set on the trajectory of the particle beam and is applied with a voltage, and a charge generated by an ionization effect at the collection electrode when the particle beam is incident on the collection electrode. In a beam position monitor including a signal processing circuit that collects collected charges and performs beam position calculation for specifying the beam positions of particle beams scanned between irradiation positions using the collected charges.
The signal processing circuit includes:
An I / V converter that generates a voltage signal corresponding to the current output by performing I / V conversion on the current output generated by the ionization effect in the collecting electrode;
A digital signal generation circuit that receives a voltage signal generated by the I / V converter and generates a digital signal related to collected charges;
A timing signal transmitting / receiving unit that receives a signal generated in a non-scanning state of the particle beam scanned from the stop irradiation point to the next stop irradiation point, as a timing signal;
At the timing when the timing signal transmission / reception unit receives the timing signal, it receives the input of the digital signal related to the collected charge generated by the digital signal generation circuit, and uses the received digital signal related to the collected charge to calculate the beam position. A beam position calculator for performing
A beam position monitor for a particle beam therapy system. The beam position monitor for the particle beam therapy system according to claim 1,
The signal processing circuit includes an amplifier that is interposed between the I / V converter and the digital signal generation circuit and amplifies a voltage signal generated by the I / V converter and input to the digital signal generation circuit. A beam position monitor for a particle beam therapy system. The beam position monitor for the particle beam therapy system according to claim 1,
The digital signal generation circuit includes an ADC circuit that performs A / D conversion on the voltage signal generated by the I / V converter and generates a digital signal related to collected charges according to the magnitude of the voltage signal. Beam position monitor for particle beam therapy equipment. The beam position monitor for the particle beam therapy system according to claim 1,
The timing signal transmission / reception unit receives a dose expiration signal indicating that the dose irradiated to the stop irradiation point of the subject has reached a set value for the stop irradiation point as the timing signal, and receives the received dose expiration signal. Consists of a dose expiration signal transmission / reception unit to be transmitted to the beam position calculation unit,
Particles characterized in that the beam position calculation unit receives the generated digital signal by allowing the digital signal generation circuit to generate a digital signal related to the collected charge at the timing of receiving the dose expiration signal. Beam position monitor for line therapy equipment. The beam position monitor for the particle beam therapy system according to claim 1,
The timing signal transmission / reception unit is supplied to a scanning electromagnet that is driven to scan the irradiation position of the particle beam, and receives an irradiation position setting completion signal indicating that the excitation current for driving the scanning electromagnet has become constant. And an irradiation position setting completion signal transmitting / receiving unit that transmits the received irradiation position setting completion signal to the beam position calculation unit,
The beam position calculation unit receives the generated digital signal by allowing the digital signal generation circuit to generate a digital signal related to the collected charge at the timing of receiving the irradiation position setting completion signal. Beam position monitor for particle beam therapy equipment. The beam position monitor for the particle beam therapy system according to claim 1,
The collecting electrode is constituted by an array of independent collecting electrode elements,
The I / V converter is provided for each of the collecting electrode elements, and converts the current output generated by the ionization action in each collecting electrode element to I / V conversion. Each of the devices is configured to receive a voltage signal generated by each I / V converter and generate a digital signal related to the collected charge,
The signal processing circuit discriminates the position where the particle beam scanned to the stop irradiation point to be irradiated next or the collecting electrode element around the incident position, and discriminates it for the beam position calculation unit. The beam position calculation using the digital signal generated by the digital signal generation circuit provided for the collection electrode element is allowed, and the digital signal generation circuit provided for the collection electrode element other than the collected collection electrode element is allowed. A beam position monitor for a particle beam therapy system, comprising: a beam position calculation control unit that prohibits beam position calculation using a generated digital signal. The beam position monitor for the particle beam therapy system according to claim 1,
The collecting electrode is constituted by an array of independent collecting electrode elements,
The I / V converter is provided for each of the collecting electrode elements, and converts the current output generated by the ionization action in each collecting electrode element to I / V conversion. Each of the devices is configured to receive a voltage signal generated by each I / V converter and generate a digital signal related to the collected charge,
The signal processing circuit includes:
An irradiation position information receiving unit that receives irradiation position information indicating the position of the stop irradiation point to be irradiated next before irradiation of the stop irradiation point to be irradiated next,
By referring to the irradiation position information received by the irradiation position information receiving unit, it is possible to determine the position where the particle beam to be scanned is incident on the stop irradiation point to be irradiated next or the collecting electrode element around the incident position. And allowing the beam position calculation unit to perform beam position calculation using a digital signal generated by a digital signal generation circuit provided for the determined collection electrode element, and collecting electrodes other than the determined collection electrode element A beam position monitor for a particle beam therapy system, comprising: a beam position calculation control unit that prohibits beam position calculation using a digital signal generated by a digital signal generation circuit provided for an element. The beam position monitor for the particle beam therapy system according to claim 1,
The collecting electrode is constituted by an array of independent collecting electrode elements,
The I / V converter is provided for each of the collecting electrode elements, and converts the current output generated by the ionization action in each collecting electrode element to I / V conversion. Each of the devices is configured to receive a voltage signal generated by each I / V converter and generate a digital signal related to the collected charge,
The signal processing circuit is provided for each of the I / V converters, and a voltage signal generated by the I / V converter and input to the digital signal generation circuit exceeds a reference voltage level. A comparator circuit that generates two determination digital signals, an effective digital signal indicating that the voltage signal does not exceed a reference voltage level,
The beam position calculation unit is provided so that a digital signal for determination generated by each comparator circuit can be input, and is generated by a digital signal generation circuit of a collecting electrode element provided with a comparator circuit that generates an effective digital signal. Performs beam position calculation using the digital signal related to the collected charge, and performs beam position calculation using the digital signal related to the collected charge generated by the digital signal generation circuit of the collection electrode element provided with the comparator circuit that generated the invalid digital signal. A beam position monitor for a particle beam therapy system, which is not performed. The beam position monitor for the particle beam therapy system according to claim 1,
The collecting electrode is constituted by an array of independent collecting electrode elements,
The I / V converter is provided for each of the collecting electrode elements, and converts the current output generated by the ionization action in each collecting electrode element to I / V conversion. An effective digital signal provided for each of the converters and receiving a voltage signal generated by each I / V converter and indicating that the received voltage signal exceeds a reference voltage level; and the voltage signal is a reference Comprising a comparator circuit that generates two determination digital signals of invalid digital signals indicating that the voltage level is not exceeded,
The beam position calculation unit is provided so that a determination digital signal generated by each comparator circuit can be input, performs beam position calculation using an effective digital signal, and does not perform beam position calculation using an invalid digital signal. A beam position monitor for a particle beam therapy system. The beam position monitor for the particle beam therapy system according to claim 1,
The signal processing circuit includes:
When the subject is divided into a plurality of irradiation slices, it becomes a condition to start irradiation of the irradiation slice, and when irradiation of a plurality of stop irradiation points set in the irradiation slice is completed, a condition for switching the irradiation slice An irradiation slice switching signal transmission / reception unit for receiving an irradiation slice switching signal,
When the irradiation slice switching signal transmission / reception unit receives an irradiation slice switching signal, irradiation of a plurality of stop irradiation points set in the irradiation slice is performed until the irradiation slice switching signal transmission / reception unit receives a next irradiation slice switching signal. A slice irradiation dose integrator for integrating the dose;
A beam position monitor for a particle beam therapy system. The beam position monitor for the particle beam therapy system according to claim 1,
The signal processing circuit includes:
When the subject is divided into a plurality of irradiation slices, it becomes a condition to start irradiation of the irradiation slice of the subject, and when irradiation of the stop irradiation points included in the irradiation pattern set in the irradiation slice is completed Is an irradiation pattern switching signal transmission / reception unit that receives an irradiation pattern switching signal that is a condition for switching the irradiation pattern;
When the irradiation pattern switching signal transmission / reception unit receives the irradiation pattern switching signal, the irradiation dose at the stop irradiation point included in the irradiation pattern is integrated until the irradiation pattern switching signal transmission / reception unit receives the next irradiation pattern switching signal. An irradiation pattern irradiation dose integrator,
A beam position monitor for a particle beam therapy system. The beam position monitor for the particle beam therapy system according to claim 1,
The signal processing circuit selectively stores a digital signal related to the collected charge used for beam position calculation of the beam position calculation unit from among the digital signals related to the collected charge generated by the digital signal generation circuit, and the beam position A beam position monitor for a particle beam therapy system, comprising a storage unit that does not store digital signals relating to collected charges that are not used for beam position calculation of a calculation unit. A plurality of stop irradiation points set on the subject are irradiated with a particle beam, and when the dose irradiated to the stop irradiation point reaches a set value, the irradiation position of the particle beam is set to the next stop irradiation point. Applied to a scanning particle beam therapy system and collects as a collected charge the charge generated by the ionization action at the collection electrode when the particle beam is incident on the collection electrode set on the trajectory of the particle beam and applied with voltage. In the beam position measuring method of the particle beam, the beam position of the particle beam scanned between the irradiation positions is specified by performing a beam position calculation using the collected charges.
The current output generated by the ionization action at the collecting electrode is I / V converted to generate a voltage signal corresponding to the current output, a digital signal related to the collected charge is generated from the generated voltage signal, and the generated digital signal related to the collected charge Set to perform the beam position calculation using
A beam of particle beam that generates the digital signal at a timing when a timing signal generated in a non-scanning state of a particle beam scanned from the stop irradiation point to the next stop irradiation point is generated Position measurement method. In the beam position measuring method of the particle beam described in claim 13,
A digital signal related to the collected charge is generated by A / D converting a voltage signal corresponding to the current output generated by performing I / V conversion on the current output generated by the ionization action at the collection electrode,
A beam position measurement method for a particle beam, wherein the beam position calculation is performed using a digital signal relating to the collected charge generated by the A / D conversion. In the beam position measuring method of the particle beam described in claim 13,
As the timing signal, a dose expiration signal indicating that the dose irradiated to the stop irradiation point of the subject has reached a set value for the stop irradiation point is used, and the digital signal is generated at the timing when the dose expiration signal is generated. A method for measuring the position of a particle beam. In the beam position measuring method of the particle beam described in claim 13,
The timing signal is supplied to a scanning electromagnet that is driven so as to scan the irradiation position of the particle beam, and an irradiation position setting completion signal that indicates that the excitation current that drives the scanning electromagnet becomes constant is used. A beam position measuring method for a particle beam, wherein the digital signal is generated at a timing when an irradiation position setting completion signal is generated. In the beam position measuring method of the particle beam described in claim 13,
The collection electrode is configured by arranging a plurality of independent collection electrode elements, and a digital signal related to the collected charge is set to be generated for each collection electrode element.
Next, the position of the incident beam beam scanned at the stop irradiation point to be irradiated or the collecting electrode element around the incident position is identified, and the beam position is determined using a digital signal related to the collected charge for the identified collecting electrode element. A beam position measurement method for a particle beam, wherein calculation is permitted and beam position calculation using a digital signal related to collected charge for a collection electrode element other than the identified collection electrode element is prohibited. In the beam position measuring method of the particle beam described in Claim 17,
Prepare in advance irradiation position information indicating the position of the stop irradiation point to be irradiated next,
It is characterized by discriminating a position where a particle beam beam scanned at a stop irradiation point to be irradiated next or a collecting electrode element around the incident position by referring to the prepared irradiation position information. Beam position measurement method for particle beam. In the beam position measuring method of the particle beam described in claim 13,
The collection electrode is configured by arranging a plurality of independent collection electrode elements, and is set to generate a digital signal related to the collection charge for each collection electrode element,
It is determined whether or not a voltage signal generated by performing I / V conversion on the current output generated by the ionizing action in each of the collecting electrode elements exceeds a reference voltage level, and the collection generated from the voltage signal exceeding the reference voltage level A beam of a particle beam that permits beam position calculation using a digital signal related to charge and prohibits beam position calculation using a digital signal related to collected charge generated from a voltage signal not exceeding a reference voltage level. Position measurement method. In the beam position measuring method of the particle beam described in claim 13,
The collection electrode is configured by arranging a plurality of independent collection electrode elements, and is set to generate a digital signal related to the collection charge for each collection electrode element,
It is determined whether or not a voltage signal generated by performing I / V conversion on the current output generated by the ionizing action in each of the collecting electrode elements exceeds a reference voltage level, and the collection generated from the voltage signal exceeding the reference voltage level The beam position calculation using the digital signal relating to the charge is allowed, the beam position calculation using the digital signal relating to the collected charge generated from the voltage signal not exceeding the reference voltage level is prohibited, and the voltage signal exceeding the reference voltage level is prohibited. The position of the collecting electrode element that is generated is a position where the particle beam is incident on the collecting electrode element, and the beam position calculation is performed to specify the beam position of the particle beam. To measure the position of a particle beam. In the beam position measuring method of the particle beam described in claim 13,
When the subject is divided into a plurality of irradiation slices, it becomes a condition for starting irradiation of the irradiation slice, and when irradiation of a plurality of stop irradiation points set in the irradiation slice is completed, a condition for switching the irradiation slice Set to generate an irradiation slice switching signal
At the timing when the irradiation slice switching signal is generated, until the next irradiation slice switching signal is generated, the irradiation doses of a plurality of stop irradiation points set in the irradiation slice are integrated. Beam position measurement method. In the beam position measuring method of the particle beam described in claim 13,
When the subject is divided into a plurality of irradiation slices, it becomes a condition to start irradiation of the irradiation slice of the subject, and when irradiation of stop irradiation points included in the irradiation pattern set in the irradiation slice is completed Is set to generate an irradiation pattern switching signal that is a condition for switching the irradiation pattern,
At the timing when the irradiation pattern switching signal is generated, until the next irradiation pattern switching signal is generated, the irradiation doses at a plurality of stop irradiation points set in the irradiation pattern are integrated. Beam position measurement method. The beam position measuring method for a particle beam according to any one of claims 17 to 20,
Particles that selectively hold a digital signal related to the collected charge used for the beam position calculation, and do not hold a digital signal related to the collected charge not used for the beam position calculation among the generated digital signals related to the collected charge. A method for measuring the beam position of a line beam.

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