CN104707267A - Particle ray irradiation device and particle ray treatment device - Google Patents

Abstract

An object of the present invention is to obtain a particle beam irradiation device that eliminates the influence of hysteresis of scanning electromagnets and realizes high-precision beam irradiation in raster scanning and hybrid scanning. It includes: a scanning power supply (4), the scanning power supply (4) outputs the excitation current of the scanning electromagnet (3); and an irradiation control device (5), the irradiation control device (5) controls the scanning power supply (4), and the irradiation control device (5) Including a scanning electromagnet command value learning generator (37), the scanning electromagnet command value learning generator (37) evaluates the results of the pre-scanning, and updates when the evaluation results do not meet the prescribed conditions. The command value (I _k ) of the excitation current is used to perform a pre-scan, and the command value (I _k ) of the excitation current whose evaluation result satisfies the specified conditions is output to the scanning power supply (4). The pre-scanning is based on the scanning power supply ( 4) A series of irradiation operations for the command value (I _k ) of the excitation current to be output.

Description

Particle beam irradiation device and particle beam therapy device

This application is a branch of an invention patent application titled "Particle Beam Irradiation Device and Particle Beam Therapy Device", with an international filing date of March 31, 2010, and application number 201080060087.1 (international application number is PCT/JP2010/055863). case application.

technical field

The present invention relates to a particle beam therapy device used for medical purposes or research purposes, and more particularly to a so-called raster scanning scanning type particle beam irradiation device and particle beam therapy device.

Background technique

Generally speaking, a particle beam therapy device includes: a beam generating device, which generates a charged particle beam; an accelerator, which is connected to the beam generating device, and accelerates the generated charged particle beam; a conveying system that conveys a charged particle beam that is emitted after being accelerated to an energy set in the accelerator; and a particle beam irradiating device that is provided downstream of the beam conveying system for A beam of charged particles is directed at the subject to be irradiated. Particle beam irradiation devices are roughly divided into wide-area irradiation methods and scanning irradiation methods (spot scanning, raster scanning, etc.). The shape of the irradiation field is consistent with the shape of the irradiation field, while the scanning irradiation method is to scan the thin beam beam to form the irradiation field so that it is consistent with the shape of the irradiation object.

In simple terms, spot scanning is a method of forming an irradiation field by irradiating a particle beam to form small dots like pointillism. That is, beam supply (dotting), beam stop, and movement are repeated. Spot scanning is an irradiation method with a high degree of freedom in which the irradiation dose can be changed for each spot position, and has attracted attention in recent years.

Simply put, raster scanning is a method of continuously irradiating a particle beam like a single stroke to form an irradiation field. That is, it is a method of moving the target dose at a constant speed within a certain area while continuing to irradiate the beam. Since there is no need to repeatedly supply/stop the beam, there is an advantage that the treatment time can be shortened.

A scanning method between point scanning and raster scanning has also been proposed. The beam is continuously irradiated like raster scanning, and the beam irradiation position is continuously moved between spot positions like spot scanning. The method described above has advantages of both point scanning and raster scanning. In this specification, the irradiation method between the two is called a hybrid scan.

In the wide-area irradiation method, a collimator and a borus are used to form an irradiation field that matches the shape of the affected area. The wide-area irradiation method forms an irradiation field that conforms to the shape of the affected area and prevents unnecessary irradiation to normal tissues, so it has become the most widely used and excellent irradiation method. However, it is necessary to make a mass for each patient, or to deform the collimator to match the affected part.

On the other hand, the scanning irradiation method is an irradiation method with a high degree of freedom that does not require a collimator or agglomerate. However, since these components that prevent normal tissues other than the affected area from being irradiated are not used, high beam irradiation positional accuracy exceeding that of the wide-area irradiation method is required.

Various inventions have been made for particle beam therapy devices to improve the accuracy of irradiation positions and irradiation doses. The object of Patent Document 1 is to provide a particle beam therapy apparatus capable of accurately irradiating an affected part, and discloses the following invention. In the invention of Patent Document 1, the scanning amount of the charged particle beam performed by the scanning device and the beam position of the charged particle beam detected by the beam position detector at this time are stored in the storage device, and the stored scanning amount and the beam position are used. The beam position is based on the beam position based on the treatment plan information, and the scanning amount of the scanning device is set by the control device. Since the relationship between the scanning amount obtained by actual irradiation and the beam position is stored in the storage device, accurate irradiation of the affected part can be expected.

The object of Patent Document 2 is to provide a particle therapy apparatus that ensures high safety and can irradiate charged particle beams with high precision, and discloses the following invention. The invention of Patent Document 2 provides a charged particle beam emitted from a charged particle beam generating device to a scanning electromagnet that scans an irradiation surface perpendicular to the beam advancing direction, and based on that the charged particle beam passing through the scanning electromagnet The position and dose on the irradiated surface are used to control the emission amount of the charged particle beam from the charged particle beam generating device. Specifically, among the plurality of regions formed by dividing the irradiated surface, the supply of the charged particle beam is stopped to the region where the target dose has been reached, and the charged particle beam is supplied to the other regions where the target dose has not been reached. In this way, the irradiation dose in each area is compared with the target dose, and ON/OFF (on/off) control (supply/stop) of the emission amount of the charged particle beam is performed, whereby high safety can be expected.

Patent Document 3 discloses the following invention to solve the problem that the hysteresis characteristic existing between the current and the magnetic field of the scanning electromagnet degrades the accuracy of the beam irradiation position. The invention of Patent Document 3 includes: a first computing unit that calculates the current value of the scanning electromagnet without considering the influence of hysteresis corresponding to the beam irradiation position based on the irradiation plan; and a second computing unit that calculates The second calculation unit performs correction calculation on the current value of the scanning electromagnet calculated by the first calculation unit considering the effect of hysteresis, and the irradiation control device controls the current of the scanning electromagnet based on the calculation result of the second calculation unit. In this way, by performing correction calculations in the second calculation unit to eliminate the influence of hysteresis, that is, by providing the second calculation unit with a mathematical model representing hysteresis characteristics, it is expected that the accuracy of the beam irradiation position will be improved through calculations.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2005-296162

Patent Document 2: Japanese Patent Laid-Open No. 2008-272139

Patent Document 3: Japanese Patent Laid-Open No. 2007-132902

Contents of the invention

In the invention disclosed in Patent Document 1, a conversion table is generated based on the actual data of the scanning amount of the charged particle beam and the beam position obtained by actual irradiation, and the setting of the scanning electromagnet is calculated using the conversion table. current value.

However, in reality, as shown in Patent Document 3, there is a hysteresis characteristic between the current and the magnetic field of the scanning electromagnet, and different magnetic fields are formed when the current value increases and when the current value decreases. In other words, even if the current value of the scanning electromagnet at a certain moment is known, the exact value of the magnetic field cannot be determined only by this information. Therefore, in the invention disclosed in Patent Document 1, there is a problem that the affected part cannot be accurately irradiated due to the influence of the hysteresis of the electromagnet.

In the invention disclosed in Patent Document 2, ON/OFF control (supply/stop) of the emission amount of the charged particle beam is performed so that the irradiation dose in each defined region reaches the target dose.

However, the plurality of regions formed by dividing the irradiation surface described in the invention disclosed in Patent Document 2 is a region (excitation region) in the excitation current space defined by the range of the excitation current of the corresponding scanning electromagnet, and It does not match the area (irradiated area) in the actual irradiated space. This is because if the hysteresis of the scanning electromagnet is not taken into consideration, the excitation region and the irradiation region will not correspond exactly to each other. Therefore, even in an apparatus or method intended to improve safety by managing the irradiation dose in units of excitation regions, the effect of dose management in a small region cannot be exhibited unless the influence of hysteresis of the scanning electromagnet is eliminated. That is, there is a problem that the accuracy of the beam irradiation position deteriorates due to the hysteresis of the scanning electromagnet.

In the invention disclosed in Patent Document 3, a mathematical model of hysteresis is generated inside the calculation unit, and the current value of the scanning electromagnet is corrected by calculation.

However, even if the influence of hysteresis is taken into account, there are many problems in the way of thinking like the invention of Patent Document 3. The first problem is that it is actually quite difficult to correct the hysteresis characteristic with high precision by means of calculation. For example, a curve representing hysteresis characteristics of current and magnetic field can take various forms depending on the following factors: the amplitude of the input (current); the speed at which the input (current) is changed; and the speed at which the input (current) is changed. model. Various studies have been carried out for a long time in various fields on expressing this complex hysteresis phenomenon using arithmetic methods, that is, using mathematical models, but the actual situation is still quite difficult. In addition, the second problem lies in the detection method of the beam irradiation position. In various conventional techniques, like the invention disclosed in Patent Document 3, it is intended to detect the beam irradiation position using only one or a plurality of beam position monitors. However, the beam position monitor can know the beam irradiation position only when the charged particle beam is irradiated to the beam position monitor. Therefore, there is a problem that when the beam deviates from the target and irradiates normal tissue or the like, the beam can only be stopped, and the beam irradiation position cannot be controlled to the correct irradiation position originally intended to be irradiated.

The present invention was made to solve the above problems, and an object of the present invention is to obtain a particle beam irradiation device capable of eliminating the influence of hysteresis of scanning electromagnets and realizing high-precision beam irradiation in raster scanning and hybrid scanning.

It includes: a scanning power supply, which outputs the exciting current of the scanning electromagnet; and an irradiation control device, which controls the scanning power supply. The irradiation control device includes a scanning electromagnet instruction value learning generator having a mathematical model for generating an instruction value of an exciting current, and the scanning electromagnet instruction value learning generator evaluating a result of the pre-scanning , update the mathematical model based on the evaluation result after the evaluation, and accumulate the experience of pre-scanning, and output the command value of the excitation current generated by the mathematical model based on the accumulated experience of pre-scanning to the scanning power supply, the pre-scanning is based on the output A series of irradiation operations up to the command value of the excitation current of the scanning power supply.

Since the particle beam irradiation apparatus of the present invention evaluates the result of the pre-scan, accumulates the experience of the pre-scan, and outputs the command value of the exciting current generated by the mathematical model based on the accumulated experience of the pre-scan to the scanning power supply, therefore, it can Eliminates the hysteresis effect of the scanning electromagnet, and realizes high-precision beam irradiation in raster scanning and hybrid scanning.

Description of drawings

FIG. 1 is a schematic configuration diagram of a particle beam therapy system according to Embodiment 1 of the present invention.

Fig. 2 is a configuration diagram of the irradiation control device of Fig. 1 .

Fig. 3 is a configuration diagram of another irradiation control device in Fig. 1 .

FIG. 4 is a diagram showing a plurality of regions defined in magnetic field space.

FIG. 5 is a diagram showing an example of a point table when learning irradiation.

6 is a configuration diagram of an irradiation control device in Embodiment 2 of the present invention.

7 is a configuration diagram of another irradiation control device in Embodiment 2 of the present invention.

FIG. 8 is an example of a mathematical model for generating a command current in Embodiment 3 of the present invention.

Fig. 9 is a configuration diagram of an irradiation control device in Embodiment 3 of the present invention.

reference sign

1 charged particle beam

1a Incident charged particle beam

1b emits a beam of charged particles

3 scanning electromagnet

3a X direction scanning electromagnet

3b Y direction scanning electromagnet

4 scan power

7 Beam position monitor

11 dose monitor

15 irradiated object

20 Magnetic field sensor

20a Magnetic field sensor for X direction electromagnet

20b Magnetic field sensor for Y direction electromagnet

22 Inverse mapping operator

33 Instruction Evaluator

34 Command updater

35 Scanning electromagnet instruction value series generator

35a Scan electromagnet instruction value series generator

35b Scan electromagnet instruction value series generator

37 Scanning electromagnet instruction value learning generator

37a Scanning electromagnet instruction value learning generator

37b Scanning electromagnet instruction value learning generator

37c Scanning electromagnet instruction value learning generator

37d Scanning electromagnet instruction value learning generator

37e Scanning electromagnet instruction value learning generator

38 Parameter updater

51 beam generating device

52 accelerator

53 beam delivery device

54 Particle ray irradiation device

60 NN (neural network: neural network)

Ps Determination of position coordinates

^a P _k irradiation position

P _k irradiation position

Ds Determination of dose

^a D _k Determination of dose

Di target dose

Bs Measure the magnetic field

^a B _k Measure the magnetic field

Estimated value of B _est magnetic field

Estimated value of B _k magnetic field

Dss area to measure dose

Dsc Area dose calculation

de dose error

T score table

S _i,j small area of magnetic field

I _k command current

Detailed ways

Embodiment 1

FIG. 1 is a schematic configuration diagram of a particle beam therapy system according to Embodiment 1 of the present invention. The particle beam therapy device includes: a beam generation device 51 ; an accelerator 52 ; a beam delivery device 53 ; a particle beam irradiation device 54 ; a treatment planning device 55 ; In addition, the treatment planning device 55 may not be regarded as a component part of the particle beam therapy device, and the device may be prepared independently. The beam generator 51 accelerates charged particles generated in the ion source to generate a charged particle beam. The accelerator 52 is connected with the beam generator 51 to accelerate the generated charged particle beam. The beam transport device 53 transports the charged particle beam that is accelerated to the energy set in the accelerator 52 and then emitted. The particle beam irradiation device 54 is provided downstream of the beam transport device 53 , and irradiates the irradiation target 15 with a charged particle beam.

The treatment planning device 55 formulates a plurality of treatment plans such as irradiation conditions based on the three-dimensional data of the affected part which is the irradiation target 15, and can simulate particle beam therapy. Here, the treatment plan finally selected by the doctor performing the particle beam therapy is converted into a code for driving the particle beam therapy device. The so-called codes for driving, for example, in the case of point scanning, are point coordinates X j (subscript i is layer number) for each irradiation layer (layer) Z _i (subscript i is layer number), Y _j (subscript _j is point number ), and the target dose D _j irradiated to this point. In addition, in the case of raster scanning, etc., the above code is represented by the irradiation position X _k , Y _k (the subscript k represents the serial number) of each sampling period Time series data of the irradiation trajectory of each irradiation layer (layer) _Zi , etc. Here, the target dose irradiated to the point is not the target dose required for the irradiated part because the upper layer is affected by the irradiation of the lower layer according to the Bragg peak characteristics. The data server 56 stores the treatment planning data generated for each patient by the treatment planning device 55 and codes for driving.

The particle beam irradiation device 54 includes: a beam conveying pipeline 2, which conveys the incident charged particle beam 1a incident from the beam conveying device 53; scanning electromagnets 3a, 3b, and the scanning electromagnets 3a, 3b The direction perpendicular to the incident charged particle beam 1a, that is, the X direction and the Y direction, makes the incident charged particle beam 1a scan; the magnetic field sensors 20a, 20b, the magnetic field sensors 20a, 20b detect the magnetic fields generated by the scanning electromagnets 3a, 3b; magnetic field data converter 21 ; beam position monitor 7 ; position data converter 8 ; dose monitor 11 ; dose data converter 12 ; irradiation control device 5 ; The magnetic field sensors 20a and 20b are, for example, magnetic field sensors having detection coils. In addition, as shown in FIG. 1 , the advancing direction of the incident charged particle beam 1 a is the Z direction.

The scanning electromagnet 3a is an X direction scanning electromagnet for scanning the incident charged particle beam 1a in the X direction, and the scanning electromagnet 3b is a Y direction scanning electromagnet for scanning the incident charged particle beam 1a in the Y direction. The magnetic field sensor 20a is an X-direction magnetic field sensor that detects a magnetic field in the X direction, and the magnetic field sensor 20b is a Y-direction magnetic field sensor that detects a magnetic field in the Y direction. The magnetic field data converter 21 converts the electric signal of the sensor indicating the magnetic field detected by the magnetic field sensors 20 a and 20 b into a measured magnetic field Bs of digital data. The beam position monitor 7 detects the passing position of the emitted charged particle beam 1b deflected by the scanning electromagnets 3a and 3b. The position data converter 8 calculates the irradiation position on the irradiation layer (layer) based on the electrical signal indicating the passing position detected by the beam position monitor 7, and generates digital data measurement position coordinates Ps. The dose monitor 11 detects the dose of the emitted charged particle beam 1b. The dose data converter 12 converts the electrical signal of the sensor indicating the dose detected by the dose monitor 11 into a measured dose Ds of digital data.

The irradiation control device 5 outputs command currents Ix _k , Iy _k , which are command values of exciting currents, to the scanning power supply 4 to control the irradiation position on each irradiation layer (layer) Z _i . The scanning power supply 4 outputs an excitation current actually driven to the scanning electromagnets 3 a and 3 b based on the command currents Ix _k and Iy _k output from the irradiation control device 5 .

FIG. 2 is a configuration diagram of the irradiation control device 5 . The irradiation control device 5 includes: an inverse map generator 30, an inverse map operator 22, a command value output device 25, a command evaluator 33, a command updater 34, a scanning electromagnet command value series generator 35, and a beam providing command output Device 26. The scanning electromagnet command value series generator 35 includes a command value storage device 36 . The command value output unit 25 , the command evaluator 33 , the command update unit 34 , and the scanning electromagnet command value sequence generator 35 constitute a scanning electromagnet command value learning generator 37 . The scan electromagnet command value learning generator 37 evaluates the result of the pre-scan, and if the result of the evaluation does not satisfy the prescribed condition, updates the command current I _k =(Ix _k , Iy _k ) to perform the pre-scan, and The command current I _k = (Ix _k , Iy _k ) whose evaluation result satisfies the predetermined condition is output to the scanning power supply 4, and the above-mentioned pre-scanning is based on the command current I _k = (Ix _k , Iy _k ) output by the scanning power supply 4 , a series of irradiation actions.

The operation of the irradiation control device 5 will be described. Irradiation by a particle beam therapy device is broadly divided into trial irradiation during calibration and full-scale irradiation during treatment. In general, the trial irradiation at the time of calibration is so-called irradiation for calibration, and the trial irradiation is performed only when calibration is required without a patient. The control input (current Ix) to the X-direction scanning electromagnet 3a and the control input (current Iy) to the Y-direction scanning electromagnet 3b were changed to various values to perform test irradiation, and the beam irradiation position at that time was measured. The test irradiation at the time of calibration in Embodiment 1 is performed in the same manner as in the prior art, but the charged particle beam is supplied and stopped in a point-scanning manner, and not only the measurement position coordinates Ps of the beam (xs, ys ), the magnetic field Bs (Bxs, Bys) is also measured using the magnetic field sensors 20a and 20b. The test irradiation is performed in a point-scanning manner, so that the measurement position coordinates Ps (xs, ys) of the beam can be clearly measured. At this time, the relationship formed between the measurement magnetic field Bs (Bxs, Bys) of the scanning electromagnet 3 and the measurement position coordinates Ps (xs, ys) of the beam is defined as the inverse map operator 22 generated by the inverse map generator 30. realized by the mathematical model.

Command current I _l = (Ix _l , Iy _l ) for test irradiation is prepared in advance (the subscript 1 indicates the point number of test irradiation) (step S001). The command current I _l = (Ix _l , Iy _l ) for test irradiation is prepared so that the point to be irradiated is irradiated within the assumed irradiation range of the particle beam irradiation device 54 . The command value output unit 25 outputs command current I _l =(Ix _l , Iy _l ) to the scanning power supply 4 (step S002 ). The scanning power supply 4 controls the scanning electromagnet 3 according to the command current I _l = (Ix _l , Iy _l ) (step S003 ).

The beam supply command output unit 26 is synchronized with the command value output unit 25, waits for a sufficient stabilization time in order to stabilize the magnetic fields of the scanning electromagnets 3a, 3b, and outputs a beam supply command to the beam generation device 51 indicating to generate a beam. S _start . The beam generator 51 starts to irradiate the charged particle beam. After the irradiation time T _on required for the test irradiation has elapsed, a beam stop command S _stop instructing to stop the beam is output to the beam generating device 51 , and the beam generating device 51 stops irradiating the charged particle beam.

The magnetic fields of the scanning electromagnets 3a, 3b controlled by the command current I _l = (Ix _l , Iy _l ) are measured by the magnetic field sensors 20a, 20b. The measured magnetic field B _l =(Bx _l , By _l ) measured for each test irradiation point is input to the inverse map generator 30 through the magnetic field data converter 21 .

The irradiation position coordinates P _l = (X _l , Y _l ) of the emitted charged particle beam 1 b scanned by the scanning electromagnet 3 for each point are calculated by the beam position monitor 7 . The irradiation position coordinates P _l =(X _l , Y _l ) are input to the inverse map generator 30 through the position data converter 8 .

The inverse map generator 30 stores the measured magnetic field B ₁ =(Bx _l , By _l ) and the irradiation position coordinates P _l =(X _l , Y _l ) of all points in a memory as a built-in storage device (step S004 ).

The inverse map generator 30 generates a mathematical model based on the stored measured magnetic field B _l = (Bx _l , By _l ) and the irradiation position coordinates P _l = (X _l , Y _l ), and stores the generated mathematical model in the inverse map in the arithmetic unit 22 (step S005).

As a preferred example, polynomials are used to realize the mathematical model of the inverse mapping operator 22 . The reason why the inverse mapping calculator 22 is used differently from the conventional conversion table will be described. Assuming that the specifications of the scanning electromagnet 3, the specification of the scanning power supply 4, and the specification of the irradiation beam (irradiation energy, incident beam position, etc.) are certain, if the magnetic field B (Bx, By) of the scanning electromagnet 3 is determined, Then the radiation position coordinate P(x, y) of the beam is uniquely determined, so it can be considered that the physical phenomenon related to the relationship between the magnetic field B and the radiation position coordinate P of the beam is a positive map of 2 inputs and 2 outputs.

However, during formal irradiation during treatment, it is necessary to provide the target irradiation position coordinates P _obj =(Px _obj , Py _obj ) of the beam in advance, and then control the magnetic field B(Bx, By) of the scanning electromagnet 3 so that the irradiation can be realized. The beam target irradiation position coordinates P _obj =(Px _obj , Py _obj ). That is, in _{the actual irradiation during treatment, it is necessary to calculate the estimated value B est = ( ▲} Bx ▼, ▲By▼), so as to realize the target irradiation position coordinate P _obj =(Px _obj , Py _obj ) (For the description of ▲Bx▼ and ▲By▼, please refer to formula (1) and formula (2)). Therefore, it should be noted that in actual irradiation, a mapping from the position to the reverse direction of the magnetic field is required. Therefore, in order to obtain the estimated value Best of the magnetic field B (Bx, By), the inverse mapping calculator 22 is required.

A method of realizing the mathematical model of the inverse mapping operator 22 using polynomials will be briefly described. Here, the term "polynomial" refers to a polynomial (polynomial) generally defined in mathematics, and is defined as "an expression composed only of sums and products of constants and variables", and the like. Specifically, it is, for example, an expression shown in the following mathematical expression.

[mathematical formula 1]

$\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 00</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}{\mathrm{<span\; class="notranslate">\; Px</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}{{\mathrm{<span\; class="notranslate">\; Px</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; Python</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}{\mathrm{<span\; class="notranslate">\; Px</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}{\mathrm{<span\; class="notranslate">\; Python</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 20</span>}}{{\mathrm{<span\; class="notranslate">\; Python</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

[mathematical formula 2]

$\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 00</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}{\mathrm{<span\; class="notranslate">\; Px</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}}{{\mathrm{<span\; class="notranslate">\; Px</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}{\mathrm{<span\; class="notranslate">\; Python</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 11</span>}}{\mathrm{<span\; class="notranslate">\; Px</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}{\mathrm{<span\; class="notranslate">\; Python</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 20</span>}}{{\mathrm{<span\; class="notranslate">\; Python</span>}}_{\mathrm{<span\; class="notranslate">\; obj</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, m ₀₀ , m ₀₁ , m ₀₂ , m ₁₀ , m ₁₁ , m ₂₀ , n ₀₀ , n _{01 , n 02 ,} n ₁₀ , n ₁₁ , and n ₂₀ are unknown parameter constants. In addition, Px _obj and Py _obj correspond to polynomial variables. In addition, the left side of the formula (1) (for Bx with a small ⌒ added to B, represented by ▲Bx▼) is the estimated value of Bx, and the left side of the mathematical formula (2) (for B with a small ⌒ added By, represented by ▲By▼) indicates that it is the estimated value of By. The estimated value B _est of the magnetic field B (Bx, By) is (▲Bx▼, ▲By▼).

The unknown parameter constants of the polynomials are obtained by the least square method or the like based on the measured magnetic field B _l = (Bx _l , By _l ) and the irradiation position coordinates P _l = (X _l , Y _l ) of the test irradiation.

For the estimated value B _est of the magnetic field B=(Bx, By) that realizes the target irradiation position coordinates P _obj =(Px _obj , Py _obj ), the formula (1) and the formula (2) Find out.

In the prior art, it is as follows: the calibrated control input to the scanning electromagnet 3 (command current I _l =(Ix _l , Iy _l )) and the radiation position coordinates P _l of the beam = (X _l , Y _l ) relationship is generated as a conversion table, and the conversion table is stored in advance in the scanning electromagnet command value generator 6 .

That is, the control input (command current Ix ₁ ) to the X-direction scanning electromagnet 3a and the target irradiation position P _obj of the beam are independently obtained from the x-coordinate (Px _obj ) of the target irradiation position P _obj of the beam. The control input (command current Iy ₁ ) to the Y-direction scanning electromagnet 3b is obtained from the y coordinate (Py _obj ).

However, in fact, since the control input to the X-direction scanning electromagnet 3a (command current Ix ₁ ) affects both the x-coordinate and the y-coordinate of the irradiation position P of the beam, and the control input to the Y-direction scanning electromagnet 3b The (command current Iy ₁ ) also affects both the x-coordinate and the y-coordinate of the beam irradiation position P, that is, there is an interference term. Therefore, the method using an independently obtained conversion table has poor irradiation position accuracy.

In the particle beam irradiation device 54 of Embodiment 1, when obtaining the estimated value Best of the magnetic field B=(Bx, By) that realizes the target irradiation position coordinates P _obj =(Px _obj , Py _obj ), the inverse mapping calculator 22 realizes a mathematical model in which the above-mentioned interference term is taken into account, and therefore, unlike conventional ones, the accuracy of the irradiation position of the emitted charged particle beam 1b can be improved.

Next, actual irradiation by the particle beam therapy system according to Embodiment 1 will be described. The full-scale irradiation is divided into learning irradiation in which control of beam irradiation positions and doses is optimized, and therapeutic irradiation in which a beam is irradiated to an irradiation subject 15 of a patient. Study irradiation is carried out in the following order.

For a certain irradiation subject 15, the treatment plan last selected by the doctor among the treatment plans generated by the treatment planning device 55 is converted into a code for driving the particle beam therapy device and sent to the irradiation control device 5 (step S101). Here, the learning irradiation and the treatment irradiation are assumed to be raster scanning, and the following case is explained: that is, the code used for driving is time-series data, and the time-series data is the irradiation position P _k (X _k , Y _k ) (the subscript k represents the sequence number) to represent the irradiation track of each irradiation layer (layer) _Zi (the subscript i is the layer number).

A command current I _k = (Ix _k , Iy _k ) (the subscript k is a serial number) for learning irradiation is generated by a method described later (step S102). For the learning irradiation, the pre-scan is performed according to the instruction current I _k = (Ix _k , Iy _k ) for the learning irradiation in the absence of a patient.

As a candidate for the command current I _k = (Ix _k , Iy _k ) for learning irradiation, or as an initial value for learning, any value may be used in extreme cases. Here, the value obtained by the conventional method is used as an initial value. The command current for learning irradiation is represented by ^a I _k = ( ^a Ix _k , ^a Iy _k ) (where a represents the number of times of learning, and a=0 in the case of the initial value), which clearly shows that Update command current.

In addition, the scanning electromagnet command value series generator 35 stores the command current ^a I _k =( ^a Ix _k , ^a Iy _k ) in the command value storage device 36 . For the command current ^a I _k =( ^a Ix _k , ^a Iy _k ), the subscript k represents the sequence number, which is the control input for each sampling period. In the state of no patient, a pre-scan is performed according to the command current ⁰ I _k =( ⁰ Ix _k , ⁰ Iy _k ) of the initial value (step S103 ).

In accordance with an instruction to start learning irradiation by the operator of the particle beam therapy apparatus, the actual irradiation start signal St generated by the signal generator 29 is sent to the beam supply command output unit 26 and the scanning electromagnet command value series generator 35 . The scanning electromagnet command value series generator 35 sequentially outputs the command current ⁰ I _k =( ⁰ Ix _k , ⁰ Iy _k ) learned for the 0th time according to the serial numbers in each sampling period.

The beam supply command output unit 26 receives the main irradiation start signal St, and outputs a beam supply command Sstart for generating a beam to the beam generating device 51 . The beam generator 51 starts to irradiate the charged particle beam.

The passing position of the emitted charged particle beam 1 b is detected by the beam position monitor 7 , and the measurement position coordinates P _s calculated by the position data converter 8 , that is, ^a P _k are input to the command evaluator 33 . The command evaluator 33 compares the target irradiation position, that is, the irradiation position P _k (X _k , Y _k ), with the measured position coordinates P _s , that is, ^a P _k ( ^a X _k , ^a Y _k ), and the initial value of the command current ⁰ I _k = ( ⁰ Ix _k , ⁰ Iy _k ) perform pre-scan scoring (step S104). The scoring method for the pre-scan is described below.

The signal generator 29 transmits the main irradiation end signal Se at the time when the main irradiation ends. The time when the main irradiation ends is the time when the sampling period×k (total number of sequences) elapses from the time when the main irradiation starts. The beam supply command output unit 26 receives the main irradiation end signal Se, and outputs a beam stop command S _stop to stop the beam to the beam generating device 51 . The beam generator 51 receives the beam stop command S _stop , and stops the incident charged particle beam 1 a (step S105 ).

The command updater 34 decides the partial sequence of the command current ^a I _k =( ^a Ix _k , ^a Iy _k ) learned in the a=0th time as an object of change based on the evaluation result output by the command evaluator 33 , that is, the score result. , to change the sequence (step S106). For example, slightly changing the third sequence ⁰ I ₃ =( ⁰ Ix 3 , ⁰ Iy ₃ ) of the instruction current ⁰ I _k =( ⁰ Ix _{k ,} ⁰ Iy _k ) of the a=0th learning from ⁰ Ix ₃ , becomes ⁰ Ix ₃ +ΔI.

Next, in the absence of a patient, a pre-scan is performed again using a command current whose partial sequence has been slightly changed (step S107 ). That is, as the second pre-scan, steps S103 to S105 are executed.

By slightly changing part of the sequence, the scoring result is changed from point J to point J+ΔJ. From this, it can be seen that it is only necessary to update the third pre-scan ⁰ Ix ₃ of the command current using the information of ΔJ/ΔI. Like a general learning function, if the scoring result is poor when ΔI is positive, it may be updated by setting ΔI to a negative value or the like. This can be done for all series whose scoring results are affected. With this update, the learning is counted once (a is incremented to (a+1)).

The command updater 34 generates the updated command current ^a I _k =( ^a Ix _k , ^a Iy _k ) learned for the a=1st time (step S108). Confirm that the 2nd pre-scan score is better than the previous pre-scan and continue learning. Repeated learning until the conditions set in advance (pass points, etc.) are met. Finally, the command current ^a I _k =( ^a Ix _k , ^a Iy _k ) after learning is stored in the command value storage device 36 . In addition, when the learning result is worse than the scoring result of the previous pre-scan, try to slow down the update speed (one update amount), or try to update the command current as described above.

Therapeutic irradiation is carried out in the following order. In response to a treatment irradiation start instruction from the operator of the particle beam therapy apparatus, the main irradiation start signal St is sent to the beam supply instruction output unit 26 and the scanning electromagnet instruction value series generator 35 . The scanning electromagnet command value series generator 35 sequentially outputs the command current ^a I _k =( ^a Ix _k , ^a Iy _k ) after learning according to the sequence number in each sampling period.

The beam supply command output unit 26 receives the main irradiation start signal St, and outputs a beam supply command S _start for generating a beam to the beam generator 51 . The beam generator 51 starts to irradiate the charged particle beam (step S109).

The signal generator 29 transmits the main irradiation end signal Se at the time when the main irradiation ends. The time when the main irradiation ends is the time when the sampling period×k (total number of sequences) elapses from the time when the main irradiation starts. The beam supply command output unit 26 receives the main irradiation end signal Se, and outputs a beam stop command S _stop to stop the beam to the beam generating device 51 . The beam generator 51 receives the beam stop command S _stop , and stops the incident charged particle beam 1 a (step S110 ).

Next, the scoring method of the pre-scan will be described. The most direct scoring method (No. 1 scoring method) is to compare the time series data with the actual pre-scanning illumination position ^a P _k ( ^a X _k , ^a Y _k ) of each sampling period (a is the learning times), and Considering the following evaluation function, the above-mentioned time-series data is represented by the irradiation position P _k (X _k , Y _k ) (the subscript k is the serial number) for each sampling period to represent the code for driving for raster scanning, that is, The data of the irradiation trajectory of each irradiation layer (layer) _Zi . When the value of the evaluation function reaches a predetermined value (when a predetermined condition is satisfied), learning ends.

[mathematical formula 3]

$\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Y</span>}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In addition, the scoring of the pre-scan can also be carried out by the following method (second scoring method) with emphasis on the radiation dose. For the pre-scan scoring, as shown in Figure 4, compare the target dose D _i and the measured dose D _s for each of the multiple small areas defined in the magnetic field space, and score according to the score table T shown in Figure 5 . For the evaluation of the pre-scan, for example, the scores of each of the small regions defined in the magnetic field space are added to define an evaluation function, and the evaluation is performed based on the scores of the evaluation function. A pre-scan with a higher score of the merit function is judged to be better than a pre-scan with a lower score. FIG. 4 is a diagram showing small magnetic field regions S _i,j defined by the magnetic field space (Bx,By), and FIG. 5 is a diagram showing an example of a score table T at the time of learning irradiation. In addition, the target dose D _i corresponding to the small area is calculated by the treatment planning device. The measured dose D _s is obtained based on the measurement result of the beam position monitor 7 and the time taken for the emitted charged particle beam 1b to pass through the above-mentioned small area, and the like.

In addition, in the second scoring method of the pre-scan, as shown in FIG. 3 , the signal input to the command evaluator 33 is different. Therefore, step S104 is also different. Fig. 3 is a configuration diagram of an irradiation control device using a second scoring method of pre-scanning. The target dose Di and the measured dose D _s ( ^a D _k ) are input to the command evaluator 33b of the scanning electromagnet command value learning generator 37b of the irradiation control device 5b. In step S104, the dose is detected by the dose monitor 11, and the measured dose _Ds converted by the dose data converter 12 is input to the command evaluator 33b. The command evaluator 33b compares the target dose Di with the measured dose Ds, and performs pre-scan scoring on the command current ⁰ I _k =( ⁰ Ix _k , ⁰ Iy _k ) of the initial value.

In Figure 4, (B ₀ , B ₁ ) in the left column of the table briefly indicates that the X component Bx of the magnetic field B satisfies the relationship of B ₀ ≤ Bx<B ₁ , similarly, (B _m-1 , B _m ) briefly indicates Bx The relationship of B _m-1 ≤ Bx<B _m is satisfied. (B ₀ , B ₁ ) in the upper part of the table briefly indicates that the Y component By of the magnetic field B satisfies the relationship B ₀ ≤By<B ₁ , similarly, (B _m-1 , B _m ) briefly indicates that By satisfies B _m-1 ≤ By<B _m relationship. The area S _{0, 0} is an area satisfying the relationship of B ₀ ≤ Bx<B ₁ and B ₀ ≤By<B ₁ , and the area S _{m-1, m-1} is an area satisfying B _m-1 ≤ Bx<B _m and B _m The region of the relation _-1 ≤By<B _m .

The scoring of the pre-scan is performed over the entire area of the magnetic field space corresponding to the irradiable range of the particle beam irradiation device 54 . As a result, since the target dose Di is managed for the irradiated target 15 of the patient, and the dose is managed to be zero for the portion corresponding to normal tissue of the non-irradiated target 15, the irradiated target 15 and the non-irradiated target 15 can be treated with high precision. The subject is dose-administered by the charged particle beam.

Once the magnetic field of the scanning electromagnet 3 is determined, the irradiation position of the charged particle beam is uniquely determined. In other words, there is a one-to-one relationship between the magnetic field of the scanning electromagnet 3 and the irradiation position of the charged particle beam. Therefore, the region defined by the command value current space of the prior art is not affected by the hysteresis of the scanning electromagnet. In addition, the relationship between the magnetic field measured by the magnetic field sensor 20 and the beam position measured by the beam position monitor 7 obtained by irradiating a charged particle beam at the time of calibration, and the formal During irradiation, the relationship between the magnetic field and the position of the beam is very consistent. Since the actual irradiation space can be obtained from the emission position of the charged particle beam, the passing position in the beam position monitor 7, and the positional relationship between the particle beam irradiation device 54 and the irradiation object 15, the area of the actual irradiation space is the same as that in The regions defined in the magnetic field space have a mapping relationship, and the mapping relationship basically remains unchanged during actual irradiation. Therefore, since the pre-scan scoring is performed on each of the multiple magnetic field small areas S _i,j defined in the magnetic field space, the dose of the charged particle beam is performed on each magnetic field small area of the magnetic field S _i,j Therefore, it is possible to perform dose management on the irradiated object 15 in the actual irradiated space with high precision.

The point table T at the time of learning irradiation shown in FIG. 5 is an example of a point reduction method. The dose error de is a difference obtained by subtracting the target dose Di from the area measurement dose Dss. The regional measured dose Dss is the actual irradiation dose of the small magnetic field S _{i, j} defined by the magnetic field space (Bx, By), according to the measured magnetic field Bs measured by the magnetic field sensor 20 and the measured dose Ds measured by the dose monitor 11 And generated. Δd is the magnitude of the dose error, which is set to a predetermined value within an allowable range. The absolute value of the change rate of the score when the measured dose Ds exceeds the target dose Di is larger than the absolute value of the change amount of the score when the measured dose Ds is smaller than the target dose Di. Accordingly, it is possible to promptly and accurately correct the fact that the measured dose Ds exceeds the target dose Di.

For the particle beam irradiation device 54 using the first scoring method in Embodiment 1, since the actual irradiation position is used as the evaluation function, the command current ^a I _k output to the scanning electromagnet 3 can be learned = ( ^a Ix _k , ^a Iy _k ) to get the proper result. In addition, for the particle beam irradiation device 54 using the second scoring method in Embodiment 1, the dose is measured for each small area of the magnetic field small area S _{i, j} defined by the magnetic field space (Bx, By) based on the target dose Di and the area Dss is used to score, and the evaluation function is defined according to the score, so that the instruction current ^a I _k =( ^a Ix _k , ^a Iy _k ) output to the scanning electromagnet 3 can be learned to obtain an appropriate result. Therefore, it is possible to provide a particle beam irradiation device with high precision and high safety.

For the particle beam irradiation device 54, in the first scoring method, since the actual irradiation position reflecting the influence of the hysteresis generated between the current of the scanning electromagnet 3 and the magnetic field is used as an evaluation function, the command output to the scanning electromagnet 3 is learned. Current ^a I _k = ( ^a Ix _k , ^a Iy _k ) to obtain a suitable result, thus eliminating the influence of hysteresis generated between the current and the magnetic field of the scanning electromagnet 3 . In addition, in the second scoring method, since the particle beam irradiation device 54 performs dose management of charged particle beams for each small area of magnetic field S _{i, j} defined by the magnetic field space (Bx, By), it is possible to eliminate Influence of the hysteresis generated between the current and the magnetic field of the scanning electromagnet 3. Therefore, the influence of the hysteresis of the scanning electromagnet can be eliminated, and high-precision beam irradiation can be realized.

The magnetic field sensor 20 may also be a magnetic field sensor having a Hall element. By using the Hall element, the absolute value of the magnetic field generated by the scanning electromagnet 3 can be measured without performing calculations such as integration of the voltage measured by the detection coil. Therefore, the magnetic field data converter 21 can be simplified and miniaturized.

Most preferably, the magnetic field sensor 20 has both a detection coil and a Hall element. The reason for this is that it is possible to have both advantages of the Hall element, which can measure the absolute value of the magnetic field, and the detection coil, which can measure the amount of change in the magnetic field without hysteresis.

Conventional particle beam irradiation devices only use one or more beam position monitors to detect the beam irradiation position, and use the measured position coordinates to perform feedback control of the charged particle beam. Arranging objects that block the charged particle beam, such as multiple position monitors, will cause the following problems: the beam scattering will be enlarged, and the desired beam spot diameter will not be obtained.

For the particle beam irradiation device 54 of Embodiment 1, during therapeutic irradiation, the scanning electromagnet command value series generator 35 sequentially outputs the command current a I k at the end of learning ^a I _k =( ^a Ix _k , ^a Iy _k ) to control the irradiation position and irradiation dose of the charged particle beam. Therefore, during therapeutic irradiation, the beam position monitor 7 can be moved by a moving device not shown so that the charged particle beam 1b can be emitted Beam position monitor 7 is not passed. This prevents the emitted charged particle beam 1 b from being scattered and amplified by the beam position monitor 7 . Thereby, the beam spot diameter can be reduced. Therefore, when it is better to irradiate with a small beam diameter, treatment can be performed with an appropriate spot diameter.

In addition, the command value output unit 25 can also generate the command current I _k =(Ix _k , Iy _k ) based on the estimated value B _est of the magnetic field B (Bx, By) of the scanning electromagnet 3, and execute it by using this as an initial value. pre-scan for learning.

In addition, an example in which the irradiation control device 5 has the inverse map generator 30 and the inverse map calculator 22 has been described, but even when the inverse map generator 30 and the inverse map calculator 22 are not provided, it is of course possible to eliminate The influence of the hysteresis of the scanning electromagnet realizes high-precision beam irradiation in raster scanning and hybrid scanning.

Thus, according to the particle beam irradiation device 54 of Embodiment 1, since it includes: the scanning power supply 4 that outputs the excitation current of the scanning electromagnet 3; and the irradiation control device 5 that controls the scanning power supply 4, The irradiation control device 5 includes a scanning electromagnet command value learning generator 37 that evaluates the result of the pre-scanning, and updates the value of the excitation current when the evaluation result does not satisfy a predetermined condition. Command value I _k , to perform pre-scanning, and output the command value I _k of the exciting current whose evaluation result satisfies the prescribed condition to the scanning power supply 4, the above-mentioned pre-scanning is based on the command value I _k of the exciting current output by the scanning power supply 4 Therefore, the scanning electromagnet command value learning generator 37 can learn the command value I _k of the excitation current output to the scanning power supply 4 based on the pre-scanning result to obtain an appropriate result, which can eliminate the scanning electromagnetic The hysteresis effect of iron enables high-precision beam irradiation in raster scan and hybrid scan.

According to Embodiment 1, the particle beam therapy apparatus includes: a beam generator 51 that generates a charged particle beam; an accelerator 52 that accelerates the charged particle beam generated by the beam generator 51 The beam transport device 53 transports the charged particle beam accelerated by the accelerator 52; and the particle beam irradiation device 54 uses the scanning electromagnet 3 to make the particle beam transported by the beam The charged particle beam delivered by the device 53 is scanned and irradiated to the irradiation object 15. The particle beam irradiation device 54 includes: a scanning power supply 4, which outputs the excitation current of the scanning electromagnet 3; and an irradiation control device 5, which controls the irradiation The device 5 controls the scanning power supply 4, and the irradiation control device 5 includes a scanning electromagnet command value learning generator 37. The scanning electromagnet command value learning generator 37 evaluates the results of the pre-scanning. In this case, the command value I _k of the excitation current is updated to perform a pre-scan, and the command value I _k of the excitation current whose evaluation result satisfies a predetermined condition is output to the scanning power supply 4. The above-mentioned pre-scanning is based on the output of the scanning power supply 4. A series of irradiation actions of the command value I _k of the excitation current, therefore, the scanning electromagnet command value learning generator 37 can learn the command value I _k of the excitation current output to the scanning power supply 4 based on the result of the pre-scan to obtain an appropriate As a result, the hysteresis effect of the scanning electromagnet can be eliminated, and high-precision particle irradiation can be used in raster scanning and hybrid scanning to achieve high-precision particle beam therapy.

Embodiment 2

In Embodiment 1, the charged particle beam is irradiated in the learning irradiation of the main irradiation, but it is also possible to perform learning without irradiating the charged particle beam, and optimize the command current I _k =(Ix _k , Iy _k ). Described below. In the particle beam therapy apparatus according to Embodiment 2, two types of pre-scan scoring methods (the third scoring method and the fourth scoring method) can be used as the pre-scan scoring method for learning irradiation. The third scoring method is to compare the time series data with the measured magnetic field ^a B _k ( ^a Bx _k , ^a By _k ) (a is the number of learning times) of each sampling period during the actual pre-scanning, and consider the following evaluation function, the above time The sequence data is based on the estimated value Best of the magnetic field corresponding to the irradiation position P _k (X _k , Y _k ) (the subscript k is the sequence number) of each sampling period, that _is , B _k = (Bx _k , By _k ) Data representing an irradiation trajectory for each irradiation layer (layer) Z _i , which is a code for driving the raster scan. In addition, the estimated value B _k of the magnetic field is calculated by the inverse mapping calculator 22 .

[mathematical formula 4]

$\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Bx</span>}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Bx</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; By</span>}_{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; By</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The fourth scoring method is a method of scoring based on the score table T shown in FIG. 5 . However, since the charged particle beam is not irradiated during the learning irradiation, unlike the first embodiment, the dose error de is the difference obtained by subtracting the target dose Di from the area dose calculation value Dsc. The area dose calculation value Dsc is obtained by integrating the dose according to the dwell time amount based on the measured magnetic field ^a B _k ( ^a Bx _k , ^a By _k ) measured by the magnetic field sensor 20, in the space defined by the magnetic field (Bx, By) The residence time of the charged particle beam 1b emitted in each magnetic field small area S _{i, j} defined by (Bx, By).

6 is a configuration diagram of an irradiation control device according to Embodiment 2 of the present invention, and a third scoring method is adopted as a scoring method of a pre-scan for learning irradiation. The signal input to the command evaluator 33 is different from that of the irradiation control device according to the first embodiment. The estimated value of the magnetic field B _k = (Bx _k , By _k ) and the measured magnetic field ^a B _k ( ^a Bx _k , ^a By _k ) are input to the command evaluator 33 c of the scanning electromagnet command value learning generator 37 c of the irradiation control device 5 c. . The operation of the irradiation control device 5 c according to Embodiment 2 will be described. The test irradiation at the time of calibration is the same as Step S001 to Step S005 of the first embodiment. The learning irradiation is also basically the same as step S101 to step S108 of Embodiment 1, but step S104 is different because a charged particle beam is not irradiated. Step S201 is executed instead of step S104 in Embodiment 1.

The magnetic fields generated by the scanning electromagnets 3a, 3b controlled by the command current I _k = (Ix _k , Iy _k ) are measured by the magnetic field sensors 20a, 20b. The measured magnetic field ^a B _k ( ^a Bx _k , ^a By _k ) measured by the magnetic field sensor 20 and converted by the magnetic field data converter 21 is input to the command evaluator 33c. The command evaluator 33c compares the estimated value of the magnetic field B _k = (Bx _k , By _k ) calculated for each serial number by the inverse mapping calculator 22 with the measured magnetic field ^a B _k ( ^a Bx _k , ^a By _k ) , perform pre-scan scoring on the initial command current ⁰ I _k =( ⁰ Ix _k , ⁰ Iy _k ) (step S201).

Next, the irradiation control device and operation in the case where the fourth scoring method is adopted as the scoring method of the pre-scan for learning irradiation will be described. FIG. 7 is a configuration diagram of another irradiation control device according to Embodiment 2 of the present invention, in which a fourth scoring method is adopted as a scoring method of pre-scan for learning irradiation. The signal input to the command evaluator 33 is different from that of the irradiation control device according to the first embodiment. The target dose Di and the area dose calculation value Dsc are input to the command evaluator 33d of the scan electromagnet command value learning generator 37d of the irradiation control device 5d. The operation of the irradiation control device 5d according to Embodiment 2 will be described. The test irradiation at the time of calibration is the same as Step S001 to Step S005 of the first embodiment. The learning irradiation is also basically the same as step S101 to step S108 of Embodiment 1, but step S104 is different because a charged particle beam is not irradiated. Step S202 is executed instead of step S104 in Embodiment 1.

Integrating the charged particle beam 1 controlled by the command current I _k = (Ix _k , Iy _k ) according to the amount of time it stays in each of the magnetic field small areas S _i,j , calculates the regional dose calculation value Dsc, And input it to the command evaluator 33d. The command evaluator 33d compares the target dose Di with the area dose calculation value Dsc, and performs pre-scan scoring on the command current ⁰ I _k =( ⁰ Ix _k , ⁰ Iy _k ) of the initial value (step S202).

In the particle beam irradiation apparatus 54 employing the third scoring method in Embodiment 2, since the measured magnetic field is used as the evaluation function, the command current ^a I _k to be output to the scanning electromagnet 3 can be learned without irradiating the charged particle beam = ( ^a Ix _k , ^a Iy _k ) to get the proper result. In addition, for the particle beam irradiation device 54 using the fourth scoring method according to Embodiment 2, the area dose calculation value Dsc calculated based on each small area of the magnetic field small area S _{i, j} defined by the magnetic field space (Bx, By) and the target dose Di to score, and define the evaluation function according to the score, so that even if the charged particle beam is not irradiated, the command current ^a I _k =( ^a Ix _k , ^a Iy _k ) output to the scanning electromagnet 3 can be learned to obtain appropriate result. Therefore, it is possible to provide a particle beam irradiation device with high precision and high safety.

In the third scoring method, the particle beam irradiation device 54 intends to use the measured magnetic field as an evaluation function to learn the command current ^a I _k =( ^a Ix _k , ^a Iy _k ) output to the scanning electromagnet 3 to obtain an appropriate result. , the influence of hysteresis generated between the current and the magnetic field of the scanning electromagnet 3 can be eliminated. In addition, in the fourth scoring method, since the particle beam irradiation device 54 performs dose management of charged particle beams for each small area of magnetic field S _{i, j} defined by the magnetic field space (Bx, By), it is possible to eliminate Influence of the hysteresis generated between the current and the magnetic field of the scanning electromagnet 3. Therefore, the influence of the hysteresis of the scanning electromagnet can be eliminated, and high-precision beam irradiation can be realized.

In addition, since the pre-scan for learning irradiation can be performed without irradiating a charged particle beam, useless energy consumption can be suppressed.

Embodiment 3

The so-called learning function can be interpreted as "the function of obtaining a solution close to a more ideal one for a problem". In Embodiments 1 and 2, the function of generating the command current I _k = (Ix _k , Iy _k ) was described. The above-mentioned command current I _k = (Ix _k , Iy _k ) is to achieve more ideal irradiation for the following problems: The above-mentioned problem is how to make the actual irradiation close to a treatment planning data generated by the treatment planning device 55 for each patient.

In control engineering, the so-called more advanced learning function (or more intelligent learning function) can be interpreted as "the function used to derive a more ideal solution to future unknown problems based on the accumulation of past experience". Therefore, in Embodiment 3, a particle beam irradiation apparatus and a particle beam therapy apparatus having a more advanced learning function to which the learning function described in Embodiments 1 and 2 are further applied will be described.

In Embodiment 1, pre-scan scoring is performed for learning irradiation, and the command current I _k itself is updated to a more appropriate value based on the scoring result. This method can generate an instruction current I _k for realizing more ideal irradiation for one treatment planning data, but this experience cannot be reflected in other treatment planning data.

In the third embodiment, for the learning irradiation, the scoring of the pre-scan is performed in the same manner as in the first or second embodiment. However, based on the scoring results of the pre-scan, it is not to update the command current I _k =(Ix _k , Iy _k ) itself, but to generate a mathematical model of the command current I _k =(Ix _k , Iy _k ). The parameters of the model are updated to more appropriate values. Hereinafter, the details thereof will be described.

FIG. 8 is a diagram showing an example of a mathematical model for generating the command current I _k =(Ix _k , Iy _k ) according to the third embodiment. Based on FIG. 8 , the configuration for generating command current I _k =(Ix _k , Iy _k ) will be described.

A feed-forward type NN (neural network, hereinafter referred to as "NN") 60 having a single hidden layer is an example of a mathematical model that generates the above-mentioned instruction current I _k =(Ix _k , Iy _k ). The input layer 61 is an input unit of the NN 60 , and in Embodiment 3 of the present invention, the target, that is, the irradiation position P _k (X _k , Y _k ) for each sampling period corresponds to the input layer 61 . X _k is input to the input layer 61a, and Y _k is input to the input layer 60b. The output layer 63 is an output unit of the NN 60 , and in Embodiment 3 of the present invention, the command current I _k =(Ix _k , Iy _k ) corresponds to the output layer 63 . Ix _k is output from the output layer 63a, and Iy _k is output from the output layer 63b. The hidden layer 62 is a basis function (activation function) of the NN60, and the input signals from the input layers 61a and 61b are weighted by the plurality of hidden layers 62a to 62n, and output to the output layers 63a and 63b.

In the particle beam therapy system, the scanning electromagnet 3 deflects the charged particle beam 1 to determine the irradiation position. That is, if a series of command currents I _k =(Ix _k , Iy _k ) for the scanning electromagnet 3 are determined, since the radiation position coordinates P=(X, Y) of the beam are uniquely determined, the series of command currents The physical phenomenon of I _k = (Ix _k , Iy _k ) to the radiation position coordinate P of the beam can be regarded as a dynamic two-input and two-output system with hysteresis characteristics. What is hoped to be realized by using NN60 is to realize mathematically a dual-input and double-output inverse system with exactly the dynamics of the hysteresis characteristic.

In Embodiments 1 and 2, what is updated during learning irradiation is the command current I _k =(Ix _k , Iy _k ) itself. On the other hand, in Embodiment 3, the weight of the hidden layer 62 of the NN60 is updated. FIG. 9 shows an irradiation control device 5 (5e) including a scanning electromagnet command value series generator 35b having a NN60. The irradiation control device 5e is an example in which the inverse map generator 30, the inverse map calculator 22, the command value output unit 25, and the command updater 34 are deleted from the irradiation control device 5a of Embodiment 1, and the scanning electromagnetic The iron command value learning generator 37e has a parameter updater 38, and NN60 is installed on the scanning electromagnet command value series generator 35. The irradiation control device 5e adopts the first scoring method for the scoring method of the pre-scan for learning irradiation. The parameter updater 38 updates the weight of the hidden layer 62 which is a parameter of the NN60 so that the evaluation result of the instruction evaluator 33 satisfies a predetermined condition. In the irradiation control device 5 including the scan electromagnet command value series generator 35b having the NN60, the second to fourth scoring methods can also be used for the scoring method of the pre-scan of the learning irradiation. In this case, any one of the command evaluators 33b to 33d may be used instead of the command evaluator 33a in FIG. 9 . In addition, in the case of the third scoring method, the irradiation control device 5 includes the inverse map generator 30 and the inverse map calculator 22 , and the estimated value B _k of the magnetic field may be calculated by the inverse map calculator 22 .

By employing the above configuration, in the particle beam therapy apparatus according to Embodiment 3 of the present invention, the experience of performing pre-scans for learning irradiation (learning pre-scans) on treatment plan data performed in the past is accumulated. In the case of accumulating a large amount of learning pre-scanning experience, it is not necessary to perform learning pre-scanning on new treatment plan data each time, and can obtain high-efficiency, less susceptible to the hysteresis of the scanning electromagnet, and high-precision irradiation. Particle radiation therapy device.

In addition, the learning algorithm described in Embodiments 1 to 3 is just an example, and other algorithms implemented in other technical fields such as the steepest descent method and the genetic algorithm can also be applied.

In addition, the evaluation function in the pre-scan evaluation is not limited to the functions described above, and other evaluation functions may be used. It is also possible to weight each sequence number k in the formulas (3) and (4). In addition, in the case of scoring each of a plurality of small regions defined in the magnetic field space, it may be obtained by adding weighting w _i,j to the score Sc _i,j of each small region Quantitative evaluation function. In this case, important positions and regions can be optimized with higher accuracy.

applications in industry

The particle beam irradiation device and the particle beam therapy device according to the present invention can be suitably applied to particle beam therapy devices for medical use or research.

Claims (11)

1. A particle ray irradiation device, comprising: A scanning electromagnet, which scans the beam of charged particles accelerated by the accelerator, and the scanning electromagnet has hysteresis; a scanning power supply, which outputs an excitation current for driving the scanning electromagnet; and An irradiation control device, which controls the scanning power supply, is characterized in that, The irradiation control device includes a scanning electromagnet command value learning generator, which has a mathematical model for generating the command value of the exciting current, and the scanning electromagnet command value learning generator performs pre-scanning The results of the evaluation are evaluated, the mathematical model is updated based on the evaluation results after the evaluation, and the experience of the pre-scan is accumulated, and the excitation generated by the mathematical model is based on the accumulated experience of the pre-scan A current command value is output to the scanning power supply, and the pre-scan is a series of irradiation operations based on the excitation current command value output to the scanning power supply. 2. The particle beam irradiation apparatus according to claim 1, wherein: Described scanning electromagnet instruction value learning generator comprises: generating said mathematical model of a command value of said field current; a learning function unit that evaluates the results of a series of irradiation operations based on the command value of the exciting current output to the scanning power supply, that is, a pre-scan, and updates the Mathematical models, and experience accumulating said pre-scans; and a scanning electromagnet command value series generator that outputs, to the Scan power. 3. The particle beam irradiation apparatus according to claim 1 or 2, wherein: The mathematical model generates the command value of the exciting current based on the target irradiation position coordinates on the irradiation subject irradiated by the charged particle beam. 4. The particle beam irradiation apparatus according to claim 1 or 2, wherein: The mathematical model is an inverse map in a case where a map of the command value of the excitation current having a dynamic characteristic of the hysteresis of the scanning electromagnet to the irradiation position of the charged particle beam is a forward map. 5. The particle beam irradiation apparatus according to claim 1 or 2, wherein: The mathematical model is a feed-forward neural network. 6. The particle beam irradiation apparatus according to claim 3, wherein: The mathematical model is a feed-forward neural network. 7. The particle beam irradiation apparatus according to claim 4, wherein: The mathematical model is a feed-forward neural network. 8. The particle beam irradiation apparatus according to claim 5, wherein: The feed-forward neural network has a single hidden layer. 9. The particle beam irradiation apparatus according to claim 6, wherein: The feed-forward neural network has a single hidden layer. 10. The particle beam irradiation apparatus according to claim 7, wherein: The feed-forward neural network has a single hidden layer. 11. A particle beam therapy device, characterized in that, Including: a beam generating device, the beam generating device is used to generate a charged particle beam; an accelerator, the accelerator accelerates the charged particle beam generated by the beam generating device; a beam delivery device, the beam a conveying device that conveys the charged particle beam accelerated by the accelerator; and a particle beam irradiating device that uses a scanning electromagnet to scan the charged particle beam conveyed by the beam conveying device to irradiate subject to be irradiated, The particle beam irradiation device is the particle beam irradiation device according to any one of claims 1 to 10.