JPWO2017141301A1 - Particle beam therapy apparatus and method for determining the number of scans of particle beam therapy apparatus - Google Patents

Abstract

In the particle beam therapy system, the number of scans is easily determined in a short time without the need for complicated measurement or the like to determine the number of scans. The irradiation control unit (80) includes an interlock circuit (14a) that imposes an interlock value on the beam intensity. The irradiation control calculation unit (70) derives the dose from the dose, the measurement result of dose calibration, and the number of irradiation spots. The predetermined number of scans is determined based on the total spot count value and the interlock value of the predetermined dose, and the predetermined spot measured by the dose monitor (42) by the beam intensity assigned the interlock value to the irradiation control unit (80). Scan with the count value and irradiate with the determined number of scans.

Description

  The present invention relates to a particle beam therapy apparatus that irradiates a particle beam to treat cancer and a method of determining the number of scans of the particle beam therapy apparatus.

  Conventionally, in a particle beam therapy system, a method for determining the number of scans of uniform scanning with broad irradiation includes a method of setting a predetermined value or optimizing according to irradiation conditions. For example, in Patent Document 1, when 5 GyE is irradiated to the entire irradiation region, all irradiation spots are irradiated with one gate by the particle beam by the first acceleration, and a dose of 3 GyE is given to the irradiation target. It is disclosed to irradiate all irradiation spots again with a particle beam generated by acceleration of 2 to give a dose of 2 GyE to an irradiation target.

JP 2014-28310 A (paragraph 0031, FIG. 1)

  In general, the method of optimizing according to irradiation conditions increases the number of scans, and the greater the number of scans, the more flat the irradiation field. However, in order to optimize the number of scans, it is calculated as the maximum number of times that the spot dose becomes equal to or greater than the minimum dose, but it is necessary to determine from the beam intensity, the movement time between the spots, etc. There was a problem.

  The present invention has been made to solve the above-described problems, and does not require complicated calculations, measurements, or the like to determine the number of scans, and easily determines the number of scans in a short time. An object of the present invention is to provide a particle beam therapy system and a method for determining the number of scans of the particle beam therapy system.

  The particle beam therapy system according to the present invention scans a particle beam with a scanning deflection magnet, measures a dose with a dose monitor, and irradiates the particle beam with an irradiation nozzle that imposes an interlock value on the beam intensity. An irradiation control unit that scans and controls the scanning deflection electromagnet, a treatment planning unit that sets a dose and the number of irradiation spots, the dose, an actually measured dose value, and a count value measured by the dose monitor The number of scans is determined on the basis of the measurement result of the dose calibration that is the ratio of the above, and the total spot count value of the predetermined dose derived from the number of irradiation spots and the interlock value, and the interlock control unit determines the interlock value. Scanning with a predetermined spot count value measured by the dose monitor according to the imposed beam intensity, and irradiating the determined number of scanning times. It is characterized in that a radiation control calculation unit.

  In addition, the method of determining the number of scans of the particle beam therapy system according to the present invention includes a dose calibration, a measurement result of dose calibration that is a ratio of an actually measured dose value and a count value measured by a dose monitor, and a predetermined number derived from the number of irradiation spots. The number of scans is determined based on the total spot count value and the interlock value of the doses.

  According to this invention, by determining the number of scans based on the interlock value, the number of scans can be easily determined in a short time by irradiating with the number of times determined by the beam intensity controlled by the interlock value. Can be irradiated.

It is a block diagram which shows schematic structure of the particle beam therapy apparatus in Embodiment 1 of this invention. It is a bird's-eye view which shows schematic structure of the whole particle beam therapy apparatus in Embodiment 1 of this invention. It is a figure explaining operation | movement of the particle beam therapy apparatus in Embodiment 1 of this invention. It is a flowchart figure at the time of particle beam irradiation of the particle beam therapy apparatus in Embodiment 1 of this invention. It is a figure explaining operation | movement of the particle beam therapy apparatus in Embodiment 2 of this invention. It is a flowchart figure at the time of particle beam irradiation of the particle beam therapy apparatus in Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram of the main configuration of the particle beam therapy system according to Embodiment 1 of the present invention, and FIG. 2 is a bird's-eye view of the schematic configuration of the entire particle beam therapy system. As shown in FIGS. 1 and 2, the particle beam therapy system according to Embodiment 1 includes a particle beam generator 10, a particle beam transport unit 20, two particle beam irradiation units 30A and 30B, and the like. Although FIG. 2 shows a system that typically includes two particle beam irradiation units, there may be more particle beam irradiation units or one particle beam irradiation unit. In FIG. 1, only one particle beam irradiation unit is provided as the particle beam irradiation unit 30 for simplicity. For operational reasons such as radiation safety management, the particle beam generator 10 and the particle beam irradiation units 30A and 30B are installed in a shielded room. The particle beam transport unit 20 connects the particle beam generator 10 and the particle beam irradiation units 30A and 30B. The particle beam transport unit 20 includes particle beam transport paths 21 and 22 that transport the particle beam generated by the particle beam generation unit 10 to the particle beam irradiation units 30A and 30B, respectively. The particle beam transport unit 20 includes a deflecting electromagnet 50 for changing the direction of the particle beam, and is configured so that the particle beam passes through the vacuum duct. The particle beam irradiation units 30A and 30B are configured to irradiate the target site of the patient with the particle beam PB. Hereinafter, the particle beam irradiation units 30A and 30B will be described as the particle beam irradiation unit 30.

  The particle beam generator 10 includes an injector 11 and an accelerator 12. The injector 11 generates and accelerates particles having a large mass such as a proton beam or a carbon beam. The accelerator 12 accelerates the particles accelerated at the first stage by the injector 11 and emits the particle beam PB. The accelerator 12 is controlled by a signal from the accelerator controller 13 provided in the irradiation controller 80. The accelerator controller 13 supplies an energy control signal to the accelerator 12, sets acceleration energy, sets energy of the particle beam PB emitted from the accelerator 12, and controls time and intensity for emitting the particle beam PB. To do.

  The particle beam irradiation unit 30 constitutes a treatment room. The particle beam irradiation unit 30 includes an irradiation nozzle 40, a treatment table 32, and the like. The treatment table 32 is used to hold the patient in a supine or sitting position. The irradiation nozzle 40 irradiates the particle beam PB transported to the particle beam irradiation unit 30 toward the irradiation target of the patient on the treatment table 32.

  In FIG. 1, the specific structure of the irradiation nozzle 40 of the particle beam irradiation part 30 in Embodiment 1 is shown. The irradiation nozzle 40 shown in FIG. 1 scans the particle beam PB in the horizontal direction, that is, the scanning deflection electromagnets 41a and 41b (41a and 41b) that scan the X and Y planes orthogonal to the particle beam PB irradiation direction. (This may also be referred to as a deflection electromagnet 41.), a scanning deflection electromagnet drive power supply 45 for driving the scanning deflection electromagnet 41, a dose monitor 42 for monitoring the irradiation dose of the particle beam PB, and an energy width of the particle beam PB. It has a ridge filter 43 which is an energy width expanding device.

  The scanning deflection electromagnet drive power supply 45 is controlled by a signal from the beam scanning controller 16 provided in the irradiation controller 80, and sets the excitation current of the scanning deflection electromagnet 41. The scanning uses a method of scanning the beam irradiation by a method of repeatedly moving and stopping the beam while continuing the irradiation. During irradiation, the dose monitor 42 measures the irradiated dose, and the count value of the measured dose is sent to the irradiation dose controller 14. The irradiation dose controller 14 is provided with an interlock circuit 14a, and the beam intensity is determined in advance by the irradiation dose controller 14 while the particle beam PB moves at a predetermined scanning speed in the spot interval per spot. When the value is exceeded, the beam is cut off, and irradiation is performed with a constant beam intensity at a spot interval per spot.

  The ridge filter 43 reduces the energy of the particle beam passing therethrough. However, since the thickness of the particle beam passing through the ridge filter 43 varies depending on the location, the particle beam after passing as a whole is the particle before passing through. The energy width is wider than the energy width of the line. Therefore, when the particle beam after passing through the ridge filter 43 is irradiated into the body, for example, the position of the Bragg peak BP, that is, the range of the particle beam is expanded.

  In the treatment planning unit 60, data of administration dose for which the irradiation dose distribution for each patient is determined is stored. The irradiation control calculation unit 70 determines the number of scans and the irradiation dose of each irradiation spot based on the administration dose data and the dose calibration measurement result, and outputs the data to the irradiation dose controller 14 of the irradiation control unit 80. To do. Further, the irradiation control calculation unit 70 also determines the energy and spot size of the particle beam that the accelerator 12 should emit and outputs the data to the accelerator controller 13.

  FIG. 3 shows an image diagram of the irradiation area when the irradiation target is actually irradiated with the particle beam. In the first irradiation, as shown in FIG. 3A, each circle indicates each irradiation spot, and scanning is performed in the direction of arrow A from the start spot 101 to the end spot 103 (1st Scan). Further, as shown in FIG. 3B, the second irradiation returns to the direction opposite to the scanning direction of the first irradiation, and scans from the start spot 201 to the end spot 203 in the direction of arrow B (2nd). Scan). Similarly, scanning is repeated N times as many times as necessary (Nth Scan, N is an integer) to complete all irradiation.

  Next, the operation of the particle beam therapy system and the method for determining the number of scans according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the particle beam therapy system according to the method for determining the number of scans in the first embodiment. First, in the treatment planning unit 60, dose data for which the irradiation dose distribution for each patient is determined is set (step S401).

Subsequently, dose calibration is measured using a water phantom based on the set dose data (step S402). Here, the total count value of the dose is derived from the measurement result of the dose calibration which is the ratio of the measured dose value in the water phantom and the dose count value in the corresponding dose monitor 42 by Equation (1).
(Equation 1)
Total dose value [TOC · Scan] = dose dose [Gy] ÷ calibration measurement result [Gy / (TOC · Scan)] (1)
Note that TOC (Total Count) means total spot dose integration.

And the total spot count value of the dose of each irradiation spot is derived | led-out by Formula (2). Note that the number of irradiation spots is set by the treatment planning unit 60.
(Equation 2)
Dose total spot count value [SPC · Scan] = Dose total count value × normal spot weight (2)
Here, the normal spot means not an edge spot, and the normal spot weight means the ratio of the count value of one spot to the total count value of doses.

Therefore, the above equation (2) can be rewritten as the equation (3) from the equation (1).
(Equation 3)
Total spot count value of dose [SPC · Scan] = (dose [Gy] ÷ calibration measurement result [Gy / (TOC · Scan)]) × normal spot weight (3)

Next, using the total spot count value of the obtained dose as the total spot count value of N irradiations at each irradiation spot, the number of scans is determined by the irradiation control calculation unit 70 (step S403). The number of scans N is determined by equation (4). The value of the number of scans N is rounded down to the first decimal place on the safe side.
(Equation 4)
Number of scans N [Scan] = total spot count value [SPC · Scan] ÷ allowed minimum spot count value of one spot [SPC] (4)

In the first embodiment, a method of scanning the beam irradiation by repeating the movement and stop of the beam while continuing the irradiation is used, and the allowable minimum spot count value per spot is expressed as shown in Expression (5). Is done.
(Equation 5)
Permissible minimum spot count value (SPC) of one spot = maximum count rate of dose monitor [MHz] × 10 ⁶ × ((spot interval [mm] ÷ maximum scanning speed [mm / msec]) × 10 ⁻³ + (static) Time “μsec” + position monitor delay speed [μsec]) × 10 ⁻⁶ ) (5)
Here, the settling time is the time until the vibration generated when the spot moves and switches to the next spot is settled. The vibration is caused by the coils used for the scanning deflection electromagnets 41a and 41b. Further, the position monitor delay speed is the time until the beam is accumulated because the beam irradiation position cannot be calculated unless a certain amount of beam is accumulated in the position monitor in order to calculate the irradiation position of the beam by a position monitor (not shown). Therefore, the settling time and the position monitor delay time are times necessary for the beam scanning position control.

Therefore, the above equation (4) can be rewritten as the equation (6) from the equation (5).
(Equation 6)
Number of scans N [Scan] = total spot count value [SPC · Scan] ÷ (maximum count rate of dose monitor [MHz] × 10 ⁶ × ((spot interval [mm] ÷ maximum scanning speed [mm / msec]) × 10 ⁻³ + (time required for beam scanning position control [μsec] × 10 ⁻⁶ ))) (6)

Furthermore, in Embodiment 1, since the maximum count rate of the dose monitor 42 is an interlock value, Expression (6) can be rewritten as Expression (7).
(Equation 7)
Number of scans N [Scan] = total spot count value [SPC · Scan] ÷ (interlock value [MHz] × 10 ⁶ × ((spot interval [mm] ÷ maximum scanning speed [mm / msec]) × 10 ⁻³ + (Time required for controlling the scanning position of the beam [μsec] × 10 ⁻⁶ ))) (7)

  Subsequently, the irradiation control calculation unit 70 calculates a spot count value that is evenly distributed per scan from the obtained number of scans N and the total spot count value, and obtains it by the beam intensity to which the interlock value is imposed. The particle beam PB is irradiated with the obtained spot count value (step S404). In the first irradiation, the beam is repeatedly moved and stopped while continuing the irradiation from the start spot 101 to the end spot 103 (see FIG. 3). Note that the spot count value is rounded off to the first decimal place on the safe side so as not to be interlocked.

  The scanning is repeated N times as many times as necessary (step S405). For example, in the first spot 102, the second spot 202 at the same position is irradiated with the same spot count, and this scanning is repeated to form the Nth spot N02. By irradiating, one spot is irradiated with the total spot count, and all irradiation is completed.

  As described above, the interlock circuit 14a is provided, and the number of scans is determined based on the interlock value of the beam intensity, so that complicated calculation and measurement are not required to determine the number of scans. The number of scans can be determined by time, and appropriate irradiation can be performed.

  As described above, in the particle beam therapy system according to Embodiment 1 of the present invention, the irradiation control unit 80 includes the interlock circuit 14a that imposes an interlock value on the beam intensity. The number of scans is determined based on the dose calibration measurement result, which is the ratio of the actually measured dose value and the count value measured by the dose monitor 42, and the total spot count value and interlock value of a predetermined dose derived from the number of irradiation spots. In order to determine the number of scans, the irradiation controller 80 scans with the predetermined spot count value measured by the dose monitor 42 with the beam intensity controlled by the interlock value and irradiates the determined number of scans. The number of scans can be easily determined in a short time without the need for complicated calculations and measurements, and appropriate irradiation can be performed.

Embodiment 2. FIG.
In the first embodiment, the case of irradiating the particle beam PB with the spot count value in which the total spot count value is equally distributed by the number of irradiations N is shown, but in the second embodiment, the case of adjusting the spot count value is shown.

  FIG. 5 is a diagram showing an irradiation pattern of the particle beam therapy system according to the first and second embodiments of the present invention. 5A shows the irradiation pattern of the first embodiment, and FIG. 5B shows the irradiation pattern of the second embodiment. As shown in FIG. 5A, in the first embodiment, for example, the planned dose per spot, that is, the total spot count value is 1502 [SPC · Scan], and the number of scans is 3 by the irradiation control calculation unit 70. When the number of times is determined, the spot count value of each scan in which the total spot count value 1502 [SPC · Scan] is evenly distributed with the number of scans of 3 is rounded down to the first decimal place as the safe side and becomes 500 [SPC]. As a result, the total dose per spot is 1500 [SPC · Scan], which deviates from the ideal value.

  In the second embodiment, as shown in FIG. 5B, the total spot count value, that is, the total dose per spot is the same as the planned dose per spot in the final (third) scan. As described above, adjustment is performed by the irradiation control calculation unit 70. That is, the irradiation control calculation unit 70 causes the irradiation control unit 80 to irradiate with 500 [SPC], which is a spot count value that is uniformly distributed in the first and second scans, and totals in the last (third) scan. It adjusts so that it may irradiate with 502 [SPC] so that it may become the spot count value 1502 [SPC * Scan], and it makes the irradiation control part 80 irradiate. About another structure, it is the same as that of the particle beam therapy apparatus of Embodiment 1, The description is abbreviate | omitted.

  Next, the operation of the particle beam therapy system and the method for determining the number of scans according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 6 is a flowchart showing the operation of the particle beam therapy system according to the method of determining the number of scans in the second embodiment. Steps 601 to 604 are the same as steps 401 to 404 in the first embodiment, and a description thereof will be omitted.

  The scanning is repeated N-1 times as many times as necessary (step S605). For example, in the first spot 102, the same spot count is irradiated to the second spot 202 at the same position, and this scanning is repeated for the (N-1) th time. The same spot count is irradiated up to spot (N-1) 02.

In the final scan (Nth scan), the irradiation control calculation unit 70 adjusts the spot count value of the final round (Nth) obtained by Equation (6), and the irradiation control unit 80 sets the interlock value. The particle beam PB is irradiated with the given constant beam intensity (step S606).
(Equation 6)
Last spot count value [SPC] = total spot count value [SPC · Scan] − (N−1) spot count value up to the first time [SPC] × (N−1) (6)

  In this way, by adjusting the spot count value in the final scan, the particle beam PB is irradiated with a constant beam intensity, so that the number of scans can be easily determined in a short time. Accuracy can be improved.

  In the second embodiment, the spot count value is adjusted in the final scan, but the present invention is not limited to this. The same effect can be obtained by adjusting the spot count value regardless of whether it is the first scan or the middle scan. Further, there may be a plurality of times for adjustment.

  As described above, in the particle beam therapy system according to Embodiment 2 of the present invention, the irradiation control calculation unit 70 adjusts the spot count value for any one of the scanning times to obtain the total spot count value. Since irradiation is performed, not only can the number of scans be determined in a short time, but also the accuracy of dose irradiation can be improved.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  14a interlock circuit, 40 irradiation nozzle, 41, 41a, 41b scanning deflection magnet, 42 dose monitor, 60 treatment planning unit, 70 irradiation control calculation unit, 80 irradiation control unit, PB particle beam.

Claims (6)

An irradiation nozzle that scans a particle beam with a scanning deflection magnet, measures a dose with a dose monitor, and irradiates the particle beam;
An irradiation control unit that has an interlock circuit that imposes an interlock value on the beam intensity, and that controls the scanning deflection electromagnet;
A treatment planning unit for setting a dose and the number of irradiation spots;
Measurement result of dose calibration, which is a ratio of the measured dose value and the count value measured by the dose monitor, and the total spot count value of the predetermined dose derived from the number of irradiation spots and the interlock value The number of scans is determined based on the irradiation, and scanning is performed with a predetermined spot count value measured by the dose monitor based on the beam intensity on which the interlock value is imposed on the irradiation controller, and the determined number of scans is irradiated. A particle beam therapy system comprising: a control calculation unit. 2. The particle beam therapy system according to claim 1, wherein the total spot count value of the dose is represented by the following formula (A).
The total spot count value of the dose = (the administration dose ÷ the measurement result of the dose calibration) × (the ratio of the count value of one spot to the total count value of the dose) (A) The particle beam therapy apparatus according to claim 1, wherein the number of scans is represented by the following formula (B).
Number of scans = total spot count value / (interlock value × ((spot interval / maximum scanning speed) + (time required for beam scanning position control))) (B)   4. The spot count value is a value obtained by dividing the total spot count value of the dose by the number of scans and rounding down the first decimal place. 5. Particle beam therapy equipment.   The spot count value is a value obtained by dividing the total spot count value of the dose by the number of scans, rounded down to the first decimal place, and adjusts the spot count value at any one of the scan times 4. The particle beam therapy system according to claim 1, wherein the total spot count value is irradiated for all scanning times. 5.   Dosage dose, measurement result of dose calibration, which is the ratio of the dose value measured based on the administration dose and the count value measured by the dose monitor, and the total spot count value and interlock value of a predetermined dose derived from the number of irradiation spots A method for determining the number of scans of a particle beam therapy system, wherein the number of scans is determined based on the method.

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