KR101297263B1 - Simulation apparatus for radiation dose of charged particle, irradiation apparatus for charged particle ray, simulation apparatus for radiation dose of charged particle, and irradiation method for charged particle ray - Google Patents

Abstract

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a charged particle dose simulation apparatus and a method for simulating charged particle dose, which can reduce the burden of arithmetic processing while calculating the dose distribution of charged particle beams while suppressing a decrease in precision.
[Resolution] The input unit 31 that receives the input of the simulation data including the material information of the object X and the irradiation information of the quantum line B, and the simulation data and dose distribution kernel received from the input unit 31. On the basis of the above, the calculation unit 33 includes a calculation unit 33 that calculates a dose distribution of the quantum line B in the irradiated object X, and the calculation unit 33 is a surface map from the quantum line B that is assumed to have reached the body surface. In addition, the surface map is subdivided to subdivide the quantum line B into a plurality of beamlets Ba, and the target object X based on the simulation data and the plurality of beamlets Ba received from the input unit 31. The simulation apparatus 3 which calculates dose distribution of the quantum wire B in ().

Description

Charged particle dose simulation apparatus, charged particle beam irradiation apparatus, simulation method of charged particle dose and charged particle beam irradiation method {Simulation apparatus for radiation dose of charged particle, irradiation apparatus for charged particle ray, simulation apparatus for radiation dose of charged particle, and irradiation method for charged particle ray}

The present invention relates to a charged particle dose simulation apparatus for simulating the dose distribution of charged particle beams in an irradiated body when irradiated with charged particle beams such as quantum wires. It relates to a full particle beam irradiation apparatus, a simulation method of charged particle dose, and a charged particle beam irradiation method.

BACKGROUND OF THE INVENTION A quantum ray therapy apparatus for treating a tumor by irradiating charged particle beams such as quantum rays is known. In the treatment of such tumors, it is necessary to formulate an irradiation plan such as absolute dose, dose distribution, irradiation position, or the like according to the shape and position of the tumor, and to irradiate the charged particle beam with high accuracy according to this irradiation plan. When formulating an investigation plan, a dose distribution is calculated in advance by inputting the irradiation conditions of the quantum wires into a simulation device mounted on a quantum wire treatment device or the like, and whether or not the quantum wires are correctly irradiated to the tumor based on the dose distribution. The simulation is performed. As a method of calculating a dose distribution, the method called Monte Carlo Simulation and Pencil Beam Algorithm (PBA), for example is known (refer nonpatent literature 1-4).

Harald Paganetti, Hongyu Jiang, Katia Parodi, Roelf Slopsema and Martijn Engelsman, IOP Publishing, Physics in Medicine and Biology, 53 (2008) 4825-4853. Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, MA 02114, USA, IOP Publishing, Physics in Medicine and Biology, 54 (2009) 4399-4421. Nobuyuki Kanematsu, Masataka Komori, Shunsuke Yonai 1 and Azusa Ishizaki, IOP Publishing, Physics in Medicine and Biology, 54 (2009) 2015-2027. Linda Hongyz, Michael Goiteiny, Marta Bucciolinix, Robert Comiskeyy, Bernard Gottschalkk, Skip Rosenthaly, Chris Seragoy and Marcia Urie, Phys. Med. Biol. 41 (1996) 1305-1330.

However, in Monte Carlo Simulation described above, the dose distribution is calculated by statistical processing, but the accuracy is high. However, the burden of computational processing is large, requiring a period of several days. On the other hand, in PBA, compared with Monte Carlo Simulation, the precision tends to be lowered, and there is a problem that it is difficult to secure desired precision.

SUMMARY OF THE INVENTION The present invention aims to solve the above problems, and it is possible to reduce the burden of computational processing while suppressing the decrease in precision, thereby enabling the early calculation of the dose distribution of charged particle beams and charged particle beams. An object of the present invention is to provide an irradiation apparatus, a simulation method of charged particle dose, and a charged particle beam irradiation method.

The present invention assumes the time when the charged particle beam is irradiated to the irradiated object, assumes that the charged particle beam is an imaginary shape having an auger spread, and calculates the spread of the charged particle beam in the irradiated object. An apparatus for simulating a dose distribution of charged particle beams in an irradiated object using a dose distribution kernel to input an input for receiving input of simulation data including material information of the irradiated object and irradiation information of charged particle beams. Means and calculating means for calculating a dose distribution of charged particle beams in the object under investigation based on the simulation data and the dose distribution kernel received from the input means, wherein the calculating means includes a predetermined range in the middle of the traveling direction of the charged particle beams. A plurality of virtual shapes having an auger spread are divided into subdivided charged particle beams and the subdivided positions as starting points. In addition, the dose distribution of the charged particle beam in the irradiated object is calculated based on the simulation data received from the input means and the plurality of virtual shapes of the charged particle beam.

When the irradiated body is composed of only a certain substance, relatively high precision can be expected even in the conventional PBA. However, since the actual irradiated object is composed of various materials intricately intertwined, in the conventional PBA, the dose distribution of the charged particle beam is precisely corrected. It is difficult to calculate. However, according to the present invention, since the virtual shape of the awl shape assumed as the charged particle beam is appropriately subdivided and assumed to be a plurality of virtual shapes, the dose distribution of the charged particle beam is calculated while each of the divided virtual shapes corresponds to a complicated convoluted configuration. This makes it possible to improve the accuracy of dose distribution. In addition, in the present invention, the dose distribution of charged particle beams is obtained after assuming that the charged particle beams are assumed to be a virtual shape of awl shape, thereby reducing the burden of calculation processing compared to Monte Carlo Simulation which derives a dose distribution by statistical calculation processing. You can. As a result, it is possible to calculate the dose distribution at an early stage while reducing the burden on the arithmetic processing while suppressing the decrease in precision.

In addition, the position which subdivides a charged particle beam is suitable as long as it is a position just before a charged particle beam enters an irradiated object. Since the charged particle beam can be subdivided into a plurality of virtual shapes corresponding to the internal structure immediately before entering the inside of the irradiated object, it is easy to further improve the precision in calculating the dose distribution of the charged particle beam.

It is also preferable to further include an output means for notifying the dose distribution calculated by the calculation means. By informing the output means of text information, image information, audio information, etc., which the operator can see and hear, the operator can easily grasp the dose distribution of the charged particle dose as the simulation result.

In addition, the output means is suitable if the dose distribution is made into an iso dose line or an iso dose plane. It is possible to easily grasp the magnitude of the dose by notifying the dose of the dose or the dose of the dose.

Moreover, the charged particle beam irradiation apparatus which concerns on this invention was equipped with the said simulation apparatus, It is characterized by the above-mentioned. According to the present invention, the charged particle beam can be irradiated on the basis of the dose distribution of the charged particle beam earlier calculated by the simulation apparatus.

In addition, the present invention assumes a time when the charged particle beam is irradiated to the irradiated object, assumes that the charged particle beam is a virtual shape having an auger spread, and derives the spread of the charged particle beam in the irradiated object. A method of simulating a dose distribution of charged particle beams in a subject using a dose distribution kernel, comprising: a subject information acquiring step of acquiring material information of a subject; a survey information setting step of determining irradiation information of a charged particle beam; Based on the irradiation information determined in the irradiation information setting step and the dose distribution kernel, the charged particle beams spread to a predetermined range in the middle of the charged particle beam's traveling direction are subdivided, and the segmented position is used as a starting point and has an awl-shaped spread. A plurality of virtual types of material information and charged particle beams acquired in the subject information acquisition step are assumed while a plurality of virtual shapes are assumed. And a simulation step of calculating a dose distribution of charged particle beams in the irradiated object based on the phase. According to the present invention, it is possible to calculate the dose distribution of the charged particle beam early, while reducing the burden of computational processing while suppressing the decrease in precision.

The charged particle beam irradiation method according to the present invention is characterized in that the charged particle beam is irradiated on the basis of the dose distribution of the charged particle beam calculated by the simulation method. According to the present invention, the charged particle beam can be irradiated on the basis of the dose distribution of the charged particle beam calculated earlier by the simulation method.

According to the present invention, it is possible to calculate the dose distribution at an early stage while reducing the burden of the calculation processing while suppressing the decrease in precision.

1 is an explanatory diagram of a quantum line treatment apparatus equipped with a simulation apparatus according to an embodiment of the present invention.
2 is an explanatory diagram showing the effect of quantum line treatment by a graph.
3 is an explanatory diagram schematically illustrating a dose distribution calculation algorithm.
4 is an explanatory diagram schematically illustrating the concept of the DMS-PBA method.
Fig. 5 is an explanatory diagram for the subdivision of beamlets in the DMS-PBA method.
FIG. 6: shows the difference with the conventional PBA method about DMS-PBA method typically, (a) is explanatory drawing which shows a PBA typically, (b) is explanatory which shows a DMS-PBA typically It is also.
Fig. 7 is a diagram showing the difference between the dose distributions of the DMS-PBA method and the conventional PBA method, where (a) is a diagram showing the difference between the two points at an equal dose line, and (b) is a depth. It is a graph which shows the dose distribution of both at 0 mm, and (c) is a graph which shows the dose distribution at 115 mm in depth.
Fig. 8 is a diagram showing a dose distribution using a clinical image (sagittal plane), and (a) shows an image of a dose distribution obtained by the PBA method by isometry. (B) is an example of the image which shows the dose distribution calculated | required by the DMS-PBA method by carrying out isometric dose linearization.
FIG. 9 is a diagram showing a dose distribution using a clinical image (axial plane), in which (a) is an example of an image showing a dose distribution obtained by the PBA method by isometry. (b) is an example of the image which shows the dose distribution calculated | required by the DMS-PBA method by carrying out isometric dose linearization.
10 is a flowchart showing a schematic procedure of quantum line treatment.
11 is a flowchart showing the operation procedure of the dose distribution simulation.
12 is a graph showing simulation results of Experimental Example 1. FIG.
13 is a graph showing the simulation results of Experimental Example 2. FIG.
14 is a graph showing the simulation results of Experimental Example 3. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described, referring drawings.

When treating a tumor (cancer lesion) by irradiating a quantum ray (charged particle beam), an investigation plan such as absolute dose, dose distribution, irradiation position, etc. is devised according to the shape and position of the tumor. Therefore, the quantum line is irradiated. As shown in FIG. 1, the quantum ray treatment apparatus (charged particle beam irradiation apparatus) 1 is a simulation apparatus (charged particle dose simulation apparatus) 3 for generating an irradiation plan, and the creation of a patient or the like in accordance with the simulation result. The irradiation apparatus 5 which irradiates the quantum wire B to the dead body X is provided.

The irradiation apparatus 5 includes an irradiation unit 51 for irradiating the quantum wire B toward the irradiated object X, a collimator 52 for adjusting the irradiation range of the quantum wire B, and a quantum wire in accordance with the shape of the cancer lesion. A bolus 53 or the like for adjusting the reach of (B) is provided. The material of the bolus 53 is polyethylene etc. The actual irradiation by the irradiation apparatus 5 is performed based on the input operation of the irradiation apparatus 5 by an operator.

However, as shown in Fig. 2, in the case of photon rays, the damage to the cells is greatest (the greatest therapeutic effect) immediately after entering the patient's skin (body surface Xa) (before reaching the cancer lesion). ) The peak is reached, and gradually decreases. On the other hand, in the case of heavy charged particles such as quantum lines, a maximum portion called Bragg Peak appears at a predetermined depth. Therefore, by appropriately adjusting the shape of the bolus 53 through which the quantum wire B passes, and adjusting the depth at which the Bragg Peak appears, the damage to the normal tissue is suppressed and the tumor tissue (cancer lesion) is adjusted. We can increase damage to.

The simulation apparatus 3 (refer FIG. 1) is equipped with the central processing unit, and the central processing unit has CPU, RAM, ROM, etc. as a hardware structure, and is an input part (input means) 31 and a calculation part (as a functional structure). Computing means) 33, and an output unit (output means) 35.

The input unit 31 is an operation device such as a touch panel, a keyboard or a mouse, and receives input of data based on the operator's operation. In addition, the input unit 31 receives image data including a cancer lesion photographed by a therapeutic CT (Computed Tomography), data relating to an irradiation area, and irradiation parameter data, for example. The irradiation parameter data is, for example, data such as the irradiation direction and the angle of the patient bed. In this embodiment, the image data (therapeutic CT image data) acquired by the therapeutic CT correspond to the substance information of the irradiated object X, and the data and irradiation parameter data regarding an irradiation area correspond to the irradiation information of a charged particle beam. do. Hereinafter, these are collectively called simulation data.

The calculation unit 33 assumes a time when the quantum wire B is irradiated onto the irradiated object X, and assumes that the quantum wire B is an imaginary shape having an awl shape (pencil beam shape), It has a function of simulating the dose distribution of the quantum line B in the inside of the object X using a dose distribution kernel which derives the spread of the quantum line B in the inside of the object X. Here, the conventional method for calculating the dose distribution was, for example, the Pencil-beam method (PBA method), but in the present embodiment, the Delta-function Multi Segmented PBA method (DMS-PBA method) further evolved the PBA method. Dose distribution calculation is performed. Hereinafter, after briefly explaining the PBA method, the DMS-PBA method will be described in detail.

The PBA method is a method of performing calculation using a dose distribution kernel in which quantum wires B are assumed to have a pencil beam shape and considering spreading due to coulomb scattering of quantum wires B in a material. . Specifically, as shown in FIG. 3, a quantum line is taken into consideration in consideration of the spread of a beam obtained by real measurement of a dose distribution in a deep portion from an irradiation point and obtained by a predetermined calculation (approximation by Gaussian). The dose distribution at a predetermined point in the advancing direction of (B) is derived. For example, to obtain a spread of the point Z ₁ as σ ₁ spread by the Gaussian approximation, is obtained from the expansion of the point Z ₂ σ ₂ as the spreading by the Gaussian approximation.

Although the conventional PBA method is advantageous in that the dose distribution of the quantum wire B can be derived in a calculation time of about several minutes, a heterogeneous substance within the irradiation range (for example, bone of a patient) It is also assumed that the accuracy of calculation decreases depending on the presence or absence of, and there is room for improvement.

The DMS-PBA method is a technique that can improve the accuracy while taking advantage of the reduction in calculation time, which is an advantage of the PBA method. There are at least two characteristic matters of the DMS-PBA method, and the first is scattering from the bolus 53 by Surface Map analysis on the body surface Xa of the subject (patient, etc.) X. Is a dose distribution calculation taking into account the second, and a second is a high-resolution dose distribution calculation by the beamlets Ba which are fired with the body surface Xa as a starting point.

These features of the DMS-PBA method will be conceptually described with reference to FIGS. 4 and 5. FIG. 4 is an explanatory diagram schematically illustrating the concept of the DMS-PBA method, and FIG. 5 is an explanatory diagram for beam segmentation in the DMS-PBA method. As shown in FIG. 4, the quantum line (beam) B input to the bolus 53 or the like proceeds while spreading by lateral multicoulomb scattering and reaches the body surface Xa. Here, the lateral emission of the beam B to the body surface Xa is calculated. This calculation is the same as that of the conventional PBA.

Next, a Surface Map on the body surface Xa is created. The surface map is a mapping of the number of beams B different in intensity (heavy), residual ratio, and residual ratio of the summed beam B in each calculation grid on the body surface Xa. For example, assuming that the bolus 53 is a block body having a cross-sectional L-shape, the residual ratio at the body surface Xa of the beam B passing through the thick portion is the beam B passing through the thin portion. It becomes small compared with the residual ratio in body surface Xa. Moreover, in the area | region where the beam B which passed the thick part and the beam B which passed the thin part overlaps on the body surface Xa, dose (intensity) becomes large compared with the area | region which does not overlap. Taking these factors into consideration, a Surface Map on the body surface Xa is created. The above is the dose distribution calculation which considered the scattering from the bolus 53 by the surface map analysis in the body surface Xa of the to-be-exposed object X, and is a 1st characteristic of the DMS-PBA method. However, the residual ratio is a distance corresponding to the kinetic energy of the quantum wire.

Next, a plurality of quantum lines (hereinafter, referred to as "beamlets") that are virtually irradiated by subdividing the surface map and subdividing each element (hereinafter referred to as "voxel") as a starting point ( Calculate the initial condition of Ba). For example, the dose of the beamlet Ba is obtained by segmenting the dose distribution in which the incidence into the body surface Xa is assumed in the delta function shape (see Fig. 5 (a)). In addition, the size of the beamlet Ba in the voxel is assumed to be extremely small.

Next, the dose distribution calculation by the beamlet Ba irradiated into the body from the body surface Xa is performed. The dose distribution calculation by the beamlet Ba will be conceptually explained with reference to FIG. Fig. 5A shows the lateral profile of the dose on the body surface Xa. As shown in Fig. 5A, the dose of the beamlet Ba is obtained by segmentation of the above-described dose distribution. Assuming that the beamlet (segment) Ba is irradiated into the body, each segment spreads as it progresses deeply (see FIG. 5 (b)). The dose distribution at any depth in the body is derived by the superposition of the segments (see FIG. 5 (c)). Fig. 5C shows the lateral profile of the dose in the body.

By integrating all the beamlets Ba, it is possible to calculate the dose distribution in the body. The above is the high resolution dose distribution calculation by the beamlet Ba projected from the body surface Xa as a starting point, and is a second feature of the DMS-PBA method. However, the specific calculation of the beam size by the DMS-PBA method is based on the following equation (1).

σ _init : initial beam size

σ _dms : Beam size by DMS-PBA

d: depth relative to body surface

t: bolus thickness

g: air-gap from bolus to body surface

σ _θ : scattering angle by bolus

σ _pt : scattered light in the subject (patient body)

Next, the difference between the PBA method and the DMS-PBA method will be described with reference to FIGS. 6 and 7. 6 (a) is an explanatory diagram schematically showing PBA, and (b) is an explanatory diagram schematically showing DMS-PBA. As shown in FIG. 6, in the PBA method, the beam B which reached | attained the body surface Xa becomes an initial condition of the beam B irradiated into a body as it is. That is, in the PBA method, the beam B, which has passed through the bolus 53 and reached the body surface Xa as the beam sizes σ ₁ , σ ₂ , and residual proportional R ₁ , R ₂ , is kept in the body under the same conditions. It is assumed to be investigated. On the other hand, in the DMS-PBA method, the beam B inputted to the body surface Xa as the beam sizes σ ₁ , σ ₂ , and residual proportional R ₁ , R ₂ is subdivided on the body surface Xa, whereby the beam size It is assumed that (σ ₀ ) is subdivided into a plurality of beamlets Ba which are extremely small compared with σ ₁ and σ ₂ , and each beamlet Ba is irradiated into the body.

FIG. 7 illustrates a case where a beam B is irradiated with respect to a model of an object X to which a bone equivalent is placed in a water equivalent, and the dose distribution is determined by the DMS-PBA method and the PBA method. The calculated result is shown, (a) is a figure which shows the upper point of both, isoline dosed, (b) is a lateral profile of both in depth 0mm, (c) is Both lateral profiles at depth of 115 mm.

As shown in Fig. 7B, when the depth d is "0mm", that is, the size of the beam B and the dose on the body surface Xa are the same. On the other hand, as shown in FIG.7 (c), when the depth d is "115 mm", the big difference arises between the dose distribution calculated | required by the PBA method, and the dose distribution calculated | required by the DMS-PBA method. This difference is due to the fact that the dose distribution is calculated without considering the existence of bone equivalents in the PBA method, whereas the dose distribution is calculated in consideration of the presence of bone equivalents in the DMS-PBA method.

The output unit 35 is an output device such as a monitor or a speaker. The output unit 35 outputs (notifies) the simulation result in the operation unit as an image that can be viewed by an operator or the like, or outputs it as sound data (notification). That is, the output unit 35 receives the dose distribution data based on the calculation result in the DMS-PBA method from the calculation unit 33, and based on the received dose distribution data, for example, the isometry line ( A dose distribution image, which has been formed into a line or isometric surface, is synthesized, and image data (image information) generated by an operator or the like is viewed and displayed (notified).

Here, the image data displayed from the output unit 35 will be described in detail with reference to FIGS. 8 and 9. 8 and 9 show an example of an image in which the dose distribution is equal dose-linearized, and the output unit 35 displays an image as shown in FIG. 8 (b) or 9 (b), for example. 8 (a) and 9 (a) are images showing dose distributions derived by the PBA method, and FIGS. 8 (b) and 9 (b) are doses derived by the DMS-PBA method. It is an image showing a distribution.

When the dose distribution image (Fig. 8 (a)) in the PBA method and the dose distribution image (Fig. 8 (b)) in the DMS-PBA method are compared, the dose distribution image in the DMS-PBA method is determined by the PBA method. Compared to the dose distribution image, each isometry line is intricately entangled, and it can be estimated that the dose distribution is calculated with high accuracy in response to the heterogeneous substance. Similarly, as shown in Fig. 9, the dose distribution image (Fig. 9 (b)) in the DMS-PBA method is more complicated than the dose distribution image (Fig. 9 (a)) in the PBA method. It is intricately shaped, and it can be inferred that the dose distribution is calculated accurately with respect to the heterogeneous substance.

Next, an outline of the actual quantum ray treatment method will be described, and a dose distribution simulation method and a quantum ray irradiation method (charged particle beam irradiation method) performed therein will be described with reference to FIGS. 10 and 11. FIG. 10 is a flowchart showing the outline procedure of quantum line treatment, and FIG. 11 is a flowchart showing the operation procedure of dose distribution simulation.

As shown in FIG. 10, the diagnosis is first performed by an operator such as a doctor (step S1), and then the image of the cancer lesion is acquired by the treatment CT after that (step S2). Next, determination of the irradiation area (step S3) and determination of the irradiation parameter (step S4) are performed. The process of acquiring the therapeutic CT image of step S2 corresponds to the subject (X) information acquisition process of acquiring the substance information of the subject X, and the determination of the irradiation area of the steps S3 and S4 and the irradiation parameter. The step in which the determination is made corresponds to the irradiation information setting step of determining the irradiation information of the charged particle beam.

Next, in the simulation apparatus 3, the process regarding dose distribution simulation is performed (step S5), and the dose distribution image as a simulation result is displayed (notified) from the output part 35. Next, as shown in FIG. Step S5 corresponds to a simulation process.

The operator confirms the dose distribution image displayed on the output unit 35. For example, the operator determines whether the Bragg peak of the quantum line B has reached the target area (cancer lesion) correctly and has not reached the target area outside (the simulation result). . Here, if an operator determines that the Bragg peak of the quantum wire B does not reach | attach a cancer lesion correctly, it returns to step S4. The operator repeatedly executes the determination of the irradiation parameters (step S4) and the dose distribution simulation (step S5) until the Bragg peak of the quantum line B reaches the cancer lesion accurately, and accurately reaches the cancer lesion. In the case of determination, the irradiation apparatus 5 is operated to perform irradiation of actual quantum lines (step S7). Step S7 is corresponded to the quantum wire irradiation method (charged particle beam irradiation method) which irradiates a quantum wire (B).

Next, the dose distribution simulation performed in the simulation apparatus 3 is demonstrated. This dose distribution simulation assumes when the quantum wire B is irradiated onto the irradiated object X, and assumes that the quantum wire B is an imaginary shape having a beam pencil shape (auger shape). As a method for simulating the dose distribution of the quantum line B in the object X using a dose distribution kernel that derives the spread of the quantum line B in the object X, the above-described PBA method It is implemented by the more advanced DMS-PBA method.

The simulation apparatus 3 performs a process concerning dose distribution simulation by receiving simulation data. The input unit 31 of the simulation apparatus 3 accepts input of simulation data including therapeutic CT image data, irradiation area data, and irradiation parameter data (step S11).

When the simulation data is received by the input unit 31, the calculation unit 33 assumes when the quantum line B is irradiated to the object X, and irradiates area data, irradiation parameter data (material information) and dose distribution. Based on the kernel, it is assumed that the quantum wire B is a beam (virtual shape) having a beam pencil shape (auger shape) spreading, and it is assumed that such a beam is fired (step S12).

Next, the calculating part 33 calculates the lateral emittance of the beam to body surface Xa using the dose distribution kernel which derives the spread of the beam in the to-be-exposed object X. FIG. In addition, the calculation unit 33 creates a Surface Map on the body surface Xa on the assumption that the beam that has spread to a predetermined range in the middle (body surface) of the beam traveling direction has reached the body surface Xa ( Step S13).

Next, in order to subdivide the beam on the body surface Xa, the calculation unit 33 subdivides the Surface Map on the body surface Xa and assumes a plurality of voxels (step S14). Further, the calculation unit 33 assumes a plurality of beamlets (virtual shapes) having a pencil beam shape (auger shape) with a plurality of voxels as starting points, and assumes that the subdivided beamlets have been fired (step). S15). The calculating unit 33 also calculates a dose distribution of the quantum lines B in the object X based on the treatment CT image data and the plurality of beamlets (step S16). This completes the dose distribution simulation.

Next, effects of the simulation apparatus 3 and the dose distribution simulation method according to the present embodiment will be described.

For example, when the subject X is made of only a certain substance, relatively high precision can be expected even in the conventional PBA method. However, since the actual object X, such as a patient, is composed of various materials intricately intertwined, it is difficult to accurately calculate the dose distribution of quantum wires (charged particle beams) in the conventional PBA method. However, according to the simulation apparatus 3 and the dose distribution simulation method which concern on this embodiment, the virtual shape of the pencil beam shape (awl shape) assumed as the quantum wire B is appropriately subdivided into a plurality of beamlets (virtual shapes). Since it is assumed, it is possible to calculate the dose distribution of the quantum line B while corresponding each of the finely divided beamlets to a complicated configuration, which is effective for improving the accuracy of the dose distribution.

In addition, in the simulation apparatus 3 and the dose distribution simulation method which concern on this embodiment, after assuming that the quantum wire (charged particle beam) B is an imaginary shape of a pencil beam shape (awl shape), Since the dose distribution is obtained, the burden of computation processing can be reduced compared to Monte Carlo Simulation, which derives the dose distribution by statistical computation. As a result, it is possible to calculate the dose distribution at an early stage while reducing the burden on the arithmetic processing while suppressing the decrease in precision.

In addition, in this embodiment, since the position which subdivides the quantum wire B is the position (body surface Xa) just before the quantum wire B enters the to-be-exposed object X, the to-be-exposed object X Since the quantum line B can be subdivided into a plurality of beamlets (virtual shapes) corresponding to the internal structure immediately before entering the inside of the structure, high precision in calculating the dose distribution of the quantum line B can be expected. .

In addition, in this embodiment, the output part 35 which informs the dose distribution computed by the calculating part 33 is provided, and the character information, image information, audio information, etc. which an operator can see and hear from the output part 35 are shown. You can inform. Therefore, the operator can easily grasp the dose distribution of the quantum line B as a simulation result.

Moreover, since the output part 35 informs an operator by outputting the image which dose-diffracted or iso dose-diffused the dose distribution, an operator can easily grasp the magnitude of a dose.

Next, the experimental result for demonstrating the superiority of this embodiment is demonstrated with reference to FIG. 12, FIG. 13, and FIG. 12, 13, and 14 show verification results using experimental geometry, and each figure (a) is a diagram schematically showing a moving direction of a quantum line B with respect to a phantom which is an object model. Each figure (b) is a graph which shows the dose distribution profile of the deep part direction of the to-be-exposed object X, and each figure (c) is a graph which shows the lateral dose distribution profile in a predetermined depth.

In Experimental Example 1, Experimental Example 2, and Experimental Example 3, polystyrene made by reproducing the boundary between the bolus 61 having a cross-sectional L-shape, air, and soft tissue seen in the sinus cavity. And a phantom 62, a 2D dosimeter (2D-ARRAY) 63 disposed below the phantom 62, and a patient bed 64 for quantum line treatment supporting the phantom 62 and 2D-ARRAY. The verification experiment is performed using an experiment apparatus (see FIGS. 12A, 13A, and 14A). In each of Experimental Examples 1, 2, and 3, a dose distribution profile was derived using the PBA method and the DMS-PBA method, assuming that the beam B passed through the phantom 62.

As shown in Fig. 12 (b), Fig. 13 (b), and Fig. 14 (b), in the simulation results (deep dose distribution profiles) of Experimental Example 1, Experimental Example 2, and Experimental Example 3, the dose at the Bragg peak The dose derived by the DMS-PBA method is smaller than the dose derived by the PBA method. 12 (c) shows the lateral dose distribution profile at the Bragg peak depth (depth d is 123 mm) of Experimental Example 1, and measured by 2D-ARRAY 63 of the experimental apparatus (Measured). ), Hot spots are observed. 13 (c) shows the lateral dose distribution profile at the Bragg peak depth (depth d is 142 mm) in Experimental Example 2, and a cold spot is observed in the measured value (Measured). 14 (c) shows the lateral dose distribution profile at the Bragg peak depth (depth d is 162 mm) in Experimental Example 3, and hot spots are observed in the measured value (Measured). Hot spots are high dose spots and cold spots are low dose spots.

Next, the content guessed from the verification result of Experimental Example 1, Experimental Example 2, and Experimental Example 3 is demonstrated.

(1) In each of Experimental Examples 1, 2 and 3, the appearance of hot spots or cold spots at the depth of Bragg peak can be considered to be due to the effect of the detour effect of both.

(2) In the PBA method, the maximum precision of about 12% was observed in the hot spot or cold spot of each Bragg peak. This is considered to be due to the spread of the pencil beam shape considering only the side spread along the central axis.

(3) The DMS-PBA method can consider the influence of heterogeneous substances in the body by the segmentation of the beam B on the body surface. As a result, the lateral dose distribution profile is about a few mm. Considering the geometric positional shift of (62), it was confirmed that the coincidence was 3%.

In addition, the following verification results can be obtained from the results shown in Table 1.

IF: Irradiation Field (irradiation field area (mm ² ))

Volume: Total Litter calculated by the beam

Time: Time taken to calculate (sec)

(1) The larger the irradiation field area is, the longer the calculation time (the time for calculation processing) of the PBA method and the DMS-PBA method is.

(2) In the PBA method and the DMS-PBA method, as the ratio of the total volume calculated by the beam becomes smaller, the ratio to the calculation time also becomes smaller.

(3) In the case where the irradiation field area was 100 x 100 mm ² , the calculation time of the DMS-PBA method was shorter than that of the PBA method.

From the above verification results, in comparison with the PBA method currently implemented in the clinic, the DMS-PBA method calculates the dose distribution in the heterogeneous region in the phantom 62 at the same calculation time (simulation result). It was confirmed that the precision of) was excellent.

In addition, although the initial verification using the phantom, it was confirmed that the DMS-PBA method can be useful in clinical use.

As mentioned above, although this invention demonstrated the simulation apparatus and dose distribution simulation method which concern on embodiment, this invention is not limited only to the said embodiment. For example, the aspect known from the output unit 35 is not limited to predetermined image data, and may be audio data or the like. In addition, the simulation apparatus is not limited to being provided in the quantum line treatment apparatus, and may be provided separately from the quantum line treatment apparatus.

3 ... Simulation apparatus, 31... Input unit (input means), 33. Computing unit (computing means), 35. Output section (output means), B... Quantum wire, beam (charged particle beam), X... Subject.

Claims (7)

Assuming that the charged particle beam is irradiated to the irradiated object, assuming that the charged particle beam is a virtual shape having an auger spread, the dose distribution kernel for deriving the spread of the charged particle beam in the irradiated object In the charged particle dose simulation apparatus for simulating the dose distribution of the charged particle beam in the irradiated object using
Input means for receiving input of simulation data including material information of the irradiated object and irradiation information of the charged particle beam;
Calculation means for calculating a dose distribution of charged particle beams in the object under investigation based on the simulation data and the dose distribution kernel received from the input means;
And,
The calculating means assumes a plurality of virtual shapes having a plurality of charged particle beams spreading to a predetermined range in the middle of the traveling direction of the charged particle beams, and having auger spreads as a starting point. And calculating a dose distribution of the charged particle beam in the irradiated object based on the plurality of virtual shapes of the simulated data and the charged particle beam received by the input means.
Charged particle dose simulation apparatus, characterized in that. The method according to claim 1,
The position where the charged particle beam is subdivided is a position immediately before the charged particle beam enters the irradiated object.
Charged particle dose simulation apparatus, characterized in that. The method according to claim 1,
Further comprising output means for informing the dose distribution calculated by the computing means
Charged particle dose simulation apparatus, characterized in that. The method according to claim 3,
The output means informs the dose distribution by iso dose lines or iso dose planes.
Charged particle dose simulation apparatus, characterized in that. The charged particle beam irradiation apparatus provided with the said charged particle dose simulation apparatus in any one of Claims 1-4. Assuming that the charged particle beam is irradiated to the irradiated object, assuming that the charged particle beam is a virtual shape having an auger spread, the dose distribution kernel for deriving the spread of the charged particle beam in the irradiated object In the simulation method of the charged particle dose to simulate the dose distribution of the charged particle beam in the irradiated object,
A subject information acquisition step of acquiring substance information of the subject;
An irradiation information setting step of determining irradiation information of the charged particle beams;
On the basis of the irradiation information determined in the irradiation information setting step and the dose distribution kernel, a plurality of the charged particle beams spread to a predetermined range in the middle of the traveling direction of the charged particle beams are subdivided, and the divided positions are used as starting points. Assuming a plurality of virtual shapes having an awl-shaped spread, the dose distribution of charged particle beams in the object under investigation based on the plurality of virtual shapes of the material information and the charged particle beams acquired in the object information acquisition step Simulation process
Simulation method of charged particle dose, characterized in that it comprises a. The charged particle beam irradiation method, wherein the charged particle beam is irradiated based on the dose distribution of the charged particle beam calculated by the simulation method of charged particle dose according to claim 6.

Images