JP2018000378A - Dose calculation device, dose calculation method, and dose calculation program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate a dose with high accuracy even when an irradiation field contains a heterogeneous material.SOLUTION: An independent calculation verification device 18 includes: a specification part that specifies a homogeneous material region where a homogeneous material exists and a heterogeneous material region where a heterogeneous material exists in an irradiation field where therapeutic radiation is emitted to a patient, based on treatment planning information generated by a CT image acquired by emitting mammographic radiation to the patient and a treatment planning device 16; and a calculation part that calculates a dose when emitting the treatment radiation to the irradiation field with use of the Clarkson method, after converting the heterogeneous material region to a region equivalent to the homogeneous material region, based on the treatment planning information.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a dose calculation device, a dose calculation method, and a dose calculation program.

  Radiation therapy, in which affected areas such as cancer tumors of patients are irradiated and treated, is generally performed based on treatment plan information generated by a radiation treatment planning system (RTPS). Is.

  In this case, in order to avoid accidents due to radiation therapy such as excessive radiation, independent calculation of whether or not the MU (monitor unit) value and the absorbed dose value representing the radiation dose included in the treatment plan information are appropriate. It is important to verify the safety by using a verification device.

  For example, the Clarkson method described in Non-Patent Document 1 is known as a method for calculating the radiation dose when the radiation field has a complicated shape. In the dose calculation by the Clarkson method, the total dose is divided into two components: the dose from the primary line and the dose from the scattered radiation. Calculate the radiation dose at.

“Clarkson is not scary,” Elekta Corporation,

URL: http://www.elekta.co.jp/software/download/pdf/Clarkson4_20110815.pdf#search='%E3%82%AF%E3%83%A9%E3%83%BC%E3%82% AF% E3% 82% BD% E3% 83% B3% E6% B3% 95 '

  In dose calculation using the Clarkson method, it is normal to calculate the dose by assuming that the irradiation field is equivalent to water, which is a homogeneous material. May contain non-homogeneous substances. In such a case, there is a problem that it is difficult to calculate the dose with high accuracy by the dose calculation using the normal Clarkson method.

  The present invention has been made to solve the above problems, and a dose calculation device, a dose calculation method, and a dose calculation program capable of accurately calculating a dose even when a heterogeneous substance is contained in an irradiation field. The purpose is to provide.

  In order to achieve the above object, the dose calculation apparatus according to claim 1 is an irradiation field for irradiating the patient with therapeutic radiation based on a CT image of the patient and treatment plan information generated by the treatment planning apparatus. A homogenous substance area in which a homogeneous substance exists, a heterogeneous substance area in which a heterogeneous substance exists, a specific part for identifying the heterogeneous substance area, and the heterogeneous substance area equivalent to the homogeneous substance area based on the treatment plan information And a calculation unit for calculating a dose when the therapeutic radiation is irradiated to the irradiation field using the Clarkson method.

  In addition, as described in claim 2, the calculation unit includes a dividing unit that divides the irradiation field radially at an equal angle around a dose evaluation point, and a dividing line that divides the irradiation field includes the heterogeneous substance. A converter that converts the length of the portion that passes through the region into a length equivalent to the case where the dividing line passes through the homogeneous material region, the length of the portion that passes through the homogeneous material region of the dividing line, and the converter Based on the length of the dividing line calculated by the calculation unit, the calculation unit that calculates the length of the dividing line by adding the length of the portion that passes through the heterogeneous substance region converted by A dose calculation unit that calculates a dose when the therapeutic radiation is irradiated to the irradiation field using the Clarkson method.

  In addition, as described in claim 3, the conversion unit is based on a physical length of a part where the dividing line passes through the heterogeneous material region and an electron density of a part through the heterogeneous material region, The length of the portion passing through the heterogeneous material region may be converted to a length equivalent to the case where the dividing line passes through the homogeneous material region.

  Moreover, as described in claim 4, the calculation unit obtains a log file in which an actual measurement value obtained by actually measuring a parameter included in the treatment plan information with a radiation irradiation apparatus is recorded, and is replaced with the treatment plan information. The dose may be calculated using the log file.

  According to a fifth aspect of the present invention, there is provided a dose calculation method in which a homogeneous substance is present in an irradiation field for irradiating the patient with therapeutic radiation based on a CT image of the patient and treatment plan information generated by the treatment planning apparatus. A step of identifying a homogeneous material region and a heterogeneous material region where a heterogeneous material exists, and after converting the heterogeneous material region into an equivalent region to the homogeneous material region based on the treatment plan information And calculating a dose when the therapeutic radiation is irradiated to the irradiation field using Clarkson method.

  A dose calculation program according to a sixth aspect is a dose calculation program for causing a computer to function as each means of the dose calculation apparatus according to any one of the first to fourth aspects.

  According to the present invention, it is possible to obtain an effect that dose calculation can be performed with high accuracy even when an inhomogeneous substance is included in the irradiation field.

It is an external view of a radiotherapy irradiation system. It is a block diagram of a radiotherapy irradiation system. (A) is a plan view of the jaw 22Y, (B) is a plan view of the jaw 22X, and (C) is a plan view of the MLC 22M. It is a functional block diagram of an independent calculation verification apparatus. It is a flowchart of the dose calculation process performed with an independent calculation verification apparatus. (A) is a figure which shows an example of an irradiation field in case there is no heterogeneous substance area | region, (B), (C) is a figure which shows an example of an irradiation field in case there exists an inhomogeneous substance area | region. It is a block diagram of the radiotherapy system concerning a modification.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an external view of the radiation therapy irradiation system 10 according to the present embodiment, and FIG. 2 shows a block diagram of the radiation therapy irradiation system 10. As shown in FIGS. 1 and 2, the radiation therapy irradiation system 10 includes a CT imaging device 12, a radiation therapy irradiation device 14, a treatment planning device 16, and an independent calculation verification device 18 as a dose calculation device.

  The CT imaging apparatus 12 irradiates X-rays as imaging radiation for CT imaging while passing the affected part of the patient H lying on the bed S in the cavity 12A, thereby obtaining a CT image (computer tomographic image). Take a picture. As shown in FIG. 2, the captured CT image is output to the treatment planning device 16. For convenience of explanation, FIG. 1 shows an example in which the CT imaging device 12 is installed in the same room as the radiation therapy irradiation device 14, but the CT imaging device 12 is installed in a separate room from the radiation therapy irradiation device 14. It is common.

  The radiotherapy irradiation device 14 irradiates the patient H lying on the bed S with therapeutic radiation (for example, X-rays) R based on the treatment plan information generated by the treatment planning device 16 to treat the affected area. Specifically, the radiation therapy irradiation apparatus 14 includes a radiation source 20 that outputs radiation R irradiated to the patient H, and a collimator 22 that narrows the radiation irradiated from the radiation source 20 to an irradiation field corresponding to the affected area of the patient H. . Here, high energy radiation (for example, 1 MeV to 1000 MeV) is used as the therapeutic radiation.

  The collimator 22 includes a jaw 22Y that narrows the irradiation field of the radiation R emitted from the radiation source 20 in the Y direction, and an X direction that orthogonally intersects the Y irradiation field of the radiation R whose irradiation field is narrowed in the Y direction by the jaw 22Y. And a multi-leaf collimator (MLC) 22M that squeezes the radiation field of the radiation R whose field is narrowed down by the jaws 22Y and 22X in accordance with the shape of the affected area. In the present embodiment, the case where the jaws 22Y, the jaws 22X, and the MLC 22M are arranged in this order from the top is shown, but the arrangement order is not limited to this.

  As shown in FIG. 3A, the jaw 22Y narrows the irradiation field F in the Y direction by moving the two rectangular movable blocks 24Y1, 24Y2 in the Y direction.

  As shown in FIG. 3B, the jaw 22X narrows the irradiation field F in the X direction by moving the two rectangular movable blocks 26X1, 26X2 in the X direction.

  As shown in FIG. 3C, the MLC 22M includes a large number of movable leaves 28M that are movable in the X direction according to the shape of the affected part of the patient H.

  As shown in FIG. 1, the radiation source 20 and the collimator 22 are provided in the gantry 14A. The gantry 14A is rotatably supported by the support portion 32 via a rotation shaft 30 along the Y direction. By rotating the gantry 14A around the rotation axis 30, the irradiation angle of the radiation R irradiated to the patient H in the XZ plane can be adjusted appropriately.

  The collimator 22 is supported by the gantry 14A so as to be rotatable about an axis along the Z direction as a rotation axis. By rotating the collimator 22 around the Z axis, the irradiation field F in the XY plane of the radiation R irradiated to the patient H can be adjusted appropriately.

  The treatment planning device 16 generates shape information for specifying the shapes of the affected part (tumor part) and the normal part based on the CT image imaged by the CT imaging device 12 and also treats radiation related to radiation to be irradiated to the affected part. Generate plan information.

  The treatment plan information includes an MU (monitor unit) value representing an irradiation dose of radiation irradiated to the patient H, an absorbed dose value, a position of the MLC 22M (hereinafter referred to as an MLC position), a position of the jaw 22X (hereinafter referred to as an X-direction jaw). Position), the position of the jaw 22Y (hereinafter referred to as the Y-direction jaw position), the rotation angle of the gantry 14A (hereinafter referred to as the gantry angle), the rotation angle of the collimator 22 (hereinafter referred to as the collimator angle), the patient H Energy of radiation (hereinafter referred to as radiant energy) and the like.

  The independent calculation verification device 18 is a dose of radiation irradiated to the patient H based on the CT image photographed by the CT imaging device 12 and the shape information and treatment plan information of the affected part generated by the treatment planning device 16. Calculate Then, the calculated MU value is compared with the MU value of the treatment plan information, and the result is provided. Also, the calculated absorbed dose value at an arbitrary point is compared with the absorbed dose value of the treatment plan information, and the result is provided.

  The independent calculation verification device 18 includes a CPU, a ROM, a RAM that stores data, a nonvolatile memory such as a hard disk that stores a dose calculation program described later, and a bus that connects these.

  If the independent calculation verification device 18 is described in terms of functional blocks divided for each function realizing means determined based on hardware and software, as shown in FIG. 4, the independent calculation verification device 18 applies imaging radiation to the patient. Based on the CT image obtained by irradiation and the treatment plan information generated by the treatment planning device 16, a homogeneous material region in which a homogeneous material exists in an irradiation field for irradiating a patient with high-energy radiation for treatment, After the heterogeneous substance region is converted into a region equivalent to the homogeneous substance region based on the treatment plan information, the specifying unit 40 for identifying the heterogeneous substance region where the heterogeneous substance exists, and Clarkson method A calculation unit 42 for calculating a dose when the irradiation field is irradiated with high-energy radiation for treatment; a storage unit 44 for storing various information such as calculation results and a dose calculation program; A display unit 46 for displaying various information calculation results and the like, the.

  Next, as an operation of the present embodiment, a dose calculation process executed by the independent calculation verification device 18 will be described with reference to a flowchart shown in FIG.

  First, a CT image of the patient H is imaged by the CT imaging device 12 before the dose calculation processing is executed by the independent calculation verification device 18. The captured CT image is output to the treatment planning device 16.

  The treatment planning device 16 generates the above-described shape information and treatment plan information on the affected area based on the CT image imaged by the CT imaging device 12. In addition, various well-known techniques are employable for the production | generation of treatment plan information.

  The independent calculation verification device 18 calculates the dose of radiation applied to the affected area of the patient H based on the CT image captured by the CT imaging device 12 and the treatment plan information generated by the treatment planning device 16. This will be specifically described below.

  In this embodiment, the dose of radiation emitted to the patient H is calculated using the Clarkson method. As a method for calculating the radiation dose using the Clarkson method, for example, the method described in Patent Document 1 can be used. In dose calculation by the Clarkson method, the total dose is divided into two components, the dose from the primary line and the dose from the scattered radiation, and the scattered radiation is determined by dividing the irregular field.

  In step S100, the radiation field irradiated to the patient H is specified based on the shape information of the affected part and the treatment plan information generated by the treatment planning device 16. Since the shape of the irradiation field to be irradiated changes depending on the irradiation angle, etc., among the information included in the treatment plan information, the MLC position, the X direction jaw position, the Y direction jaw position, the gantry angle, and the collimator angle And the radiation irradiation field is specified based on the shape information of the affected area.

  In step S102, based on the CT image, a homogeneous material region in which a homogeneous material exists and a heterogeneous material region in which a heterogeneous material exists in an irradiation field that irradiates a patient with high-energy radiation for treatment. Identify. In the present embodiment, as an example, a case will be described in which the radiation field identified in step S100 is a radiation field F having a shape as shown in FIG. Note that the hatched region in FIG. 6A represents a shielding region G where radiation irradiation is shielded by the collimator 22.

  When there is no inhomogeneous material, the irradiation field F can be treated as equivalent to water, which is a homogeneous material, and all the irradiation fields F can be regarded as the homogeneous material region E0. However, actually, as shown in FIG. 6B, the irradiation field F includes a heterogeneous material region E1 where the first heterogeneous material close to air exists, or FIG. ), A heterogeneous material region E2 where a second heterogeneous material between water and air exists is included. The heterogeneous substance region E1 is a region generated by a gap between the apparatus and the breast when the affected part is a breast or the like, for example. The heterogeneous substance region E2 is a region where an organ such as a lung exists.

  When the heterogeneous material region exists, the irradiated radiation is scattered to the side (direction orthogonal to the irradiation direction of the radiation). However, in the dose calculation using the conventional Clarkson method, the irradiation field F is all water. In order to calculate the dose of radiation, side scatter of radiation is not taken into account. For this reason, an error from the actual dose increases, and the accuracy of independent calculation verification may be reduced.

  Therefore, in the present embodiment, dose calculation by the Clarkson method is performed in consideration of heterogeneous substances.

  Whether the material is homogeneous or heterogeneous can be determined based on the CT value of the CT image. The CT image represents the distribution of CT values. The CT value is expressed as a relative value with respect to water with water being “0”, and for example, air is expressed as “−1000”. Therefore, it is possible to determine which region each substance in the irradiation field F belongs to by previously determining the range of CT values represented by the first heterogeneous substance and the second heterogeneous substance.

In step S104, the dose component by the primary line is calculated based on the MU value, energy, etc. of the radiation dose in the treatment plan information. As described in Non-Patent Document 1, the dose from the primary beam is given by unscattered photons emitted from the radiation source 20 and does not depend on the size of the irradiation field. In this embodiment, as described in Non-Patent Document 1, the dose component due to the primary line is calculated as a TAR (Tissue Air Ratio) in an irradiation field of 0 × 0 cm ² .

  In step S106, a dose component due to scattered radiation is calculated based on the MU value, energy, and the like of the radiation dose in the treatment plan information in the treatment plan information. As described in Non-Patent Document 1, the dose due to the scattered radiation is given by the collimator 22, the flattening filter, or rarely photons scattered in the air, and depends on the collimator size (the size of the irradiation field). To do. Note that the dose due to scattered radiation can be further divided into two components: a scattering component generated in the gantry head of the gantry 14A and a scattering component generated in the phantom.

  In order to calculate the dose component due to the scattered radiation, for example, as shown in FIGS. 6A to 6C, the irradiation field F is radiated at an equal angle radially to a plurality of sectors FS around a predetermined dose evaluation point K. To divide. In the example of FIGS. 6A to 6C, the irradiation field F is divided into 12 at 30 degrees in a radial manner.

  Next, the length of the dividing line D when the irradiation field F is radially divided at an equal angle is calculated. At this time, the dividing line D is not simply the length from the dose evaluation point K to the peripheral edge of the irradiation field F, but the dividing line D passing through the heterogeneous material regions E1 and E2 is inhomogeneous material regions E1 and E2. Is converted into a length equivalent to that passing through the homogeneous material region E0, and the length of each dividing line D is calculated.

  Specifically, the length of each dividing line D is calculated by the following equation.

... (1)

Here, N is the number of heterogeneous material regions through which the dividing line D passes. PL _i is the physical length of the heterogeneous material region through which the dividing line D passes i-th. ED _i is an electron density corresponding to the CT value of the heterogeneous material region where the dividing line D passes through i-th. For example, table data representing the correspondence between CT values and electron density is prepared in advance, and ED _i corresponding to the CT value of the heterogeneous material region through which the dividing line D passes i-th is prepared using this table data. You can ask for.

  Here, for example, when there is a dividing line D passing through the homogeneous material region E0 and the heterogeneous material regions E1 and E2, the length RPL of the dividing line D passing through the heterogeneous material regions E1 and E2 is expressed by the following equation. .

RPL = PL ₁ × ED ₁ + PL ₂ × ED ₂ (2)

  When the length of the homogeneous material region E0 through which the dividing line D passes is LPL, the length PL of the dividing line D is calculated by the following equation.

PL = RPL + LPL (3)

  Thus, the length of the dividing line D is calculated after converting the length passing through the heterogeneous material region into a length equivalent to the length passing through the homogeneous material region. This is performed for all the dividing lines D.

  Then, as described in Non-Patent Document 1, the SAR (Scatter Air Ratio) of each sector FS is calculated. At this time, the SAR is calculated except for the shielding region G where radiation irradiation is blocked by the collimator 22.

  Next, the dose component of the scattered radiation of the irradiation field F is calculated by adding all the SARs of the sectors FS.

  In step S108, the MU value of the irradiation dose and the absorbed dose value at an arbitrary point are calculated. Specifically, first, the radiation dose Q of the irradiation field F is calculated by adding the dose component TAR of the primary ray calculated in step S102 and the dose component SAR of the scattered radiation calculated in step S104. Then, the MU value and the absorbed dose value at an arbitrary point are calculated from the irradiation dose Q by a predetermined calculation formula.

  In step S110, the difference between the MU value of the irradiation dose Q of the irradiation field F calculated in step S108 and the MU value of the irradiation dose included in the treatment plan information generated by the treatment planning device 16 is calculated.

  In step S109, the MU value of the irradiation dose included in the treatment plan information is acquired.

  In step S111, based on the MU value acquired in step S109, the absorbed dose value of the irradiation field F at an arbitrary point is calculated.

  In step S113, the difference between the absorbed dose value of the irradiation field F at the arbitrary point calculated in step S111 and the absorbed dose value included in the treatment plan information generated by the treatment planning device 16 is calculated.

  The difference calculated in step S110 and the difference calculated in step S111 are used as judgment materials when verifying whether or not the treatment plan is valid.

  As described above, in the present embodiment, when calculating the dose component due to the scattered radiation, the calculation is performed in consideration of the inhomogeneous material. Therefore, the dose component due to the scattered radiation is calculated in consideration of the lateral scattering of the radiation. . Thereby, the irradiation dose can be calculated with high accuracy, and independent calculation verification can be executed with high accuracy.

  By the way, the radiation therapy irradiation apparatus 14 includes various sensors (not shown) for detecting various parameters including the MU value of the irradiation dose, the MLC position, the X direction jaw position, the Y direction jaw position, the gantry angle, and the collimator angle. When the patient H is irradiated with radiation based on the treatment plan information, the various parameters are stored as a log file in the storage unit (not shown).

  The various parameters (expected values) in the treatment plan information may not exactly match the various parameters (actual values) in the log file, and the dose calculation using the various parameters in the log file may result in actual measurement. It may be possible to perform a reflected dose calculation.

  Therefore, for example, as shown in FIG. 7, when the independent calculation verification device 18 acquires the log file output from the radiotherapy irradiation device 14 and executes the dose calculation of FIG. 5, instead of the treatment plan information, You may make it perform dose calculation using the various parameters contained in the log file acquired from the radiotherapy irradiation apparatus 14. FIG. Thereby, dose calculation reflecting actual measurement can be performed.

  Moreover, the dose calculation program demonstrated by this embodiment is an example to the last. Therefore, it goes without saying that unnecessary steps may be deleted, new steps may be added, and the processing order may be changed within a range not departing from the spirit.

DESCRIPTION OF SYMBOLS 10 Radiotherapy irradiation system 12 CT imaging apparatus 14 Radiation therapy irradiation apparatus 14A Gantry 16 Treatment plan apparatus 18 Independent calculation verification apparatus 20 Radiation source 22 Collimator 22Y Jaw 22X Jaw 22M Multi-leaf collimator 40 Specific part 42 Calculation part 44 Storage part 46 Display part D Dividing line E0 Homogeneous material region E1, E2 Heterogeneous material region

In order to achieve the above object, the dose calculation apparatus according to claim 1 is an irradiation field for irradiating the patient with therapeutic radiation based on a CT image of the patient and treatment plan information generated by the treatment planning apparatus. A homogenous substance area in which a homogeneous substance exists, a heterogeneous substance area in which a heterogeneous substance exists, a specific part for identifying the heterogeneous substance area, and the heterogeneous substance area equivalent to the homogeneous substance area based on the treatment plan information on converted into an area, seen including a calculation unit for calculating the dose when irradiated with the therapeutic radiation in the irradiation field by using the Clarkson method, wherein the calculation unit, around a dose evaluation point Equivalent to the division part that divides the irradiation field radially at equal angles and the length of the part where the dividing line that divides the irradiation field passes through the heterogeneous material region. To convert to a long length And calculating the length of the dividing line by adding the length of the portion where the dividing line passes through the homogeneous material region and the length of the portion passing through the heterogeneous material region converted by the converting unit. And a dose calculation unit for calculating a dose when the therapeutic radiation is irradiated to the irradiation field using the Clarkson method based on the length of the dividing line calculated by the calculation unit. The conversion unit includes N as the number of the heterogeneous material regions through which the dividing line passes, PL _{i as} the physical length of the heterogeneous material region through which the dividing line passes i-th, and the heterogeneity through which the dividing line passes through i-th. The electron density corresponding to the CT value of the CT image of the material region is defined as ED _i , and the length RPL of the portion passing through the heterogeneous material region is calculated by the formula [1], whereby the dividing line is converted into the homogeneous line. Convert to the equivalent length when passing through the material region

In addition, as described in claim 2 , the calculation unit obtains a log file in which actual values obtained by actually measuring parameters included in the treatment plan information with a radiation irradiation apparatus are recorded, and instead of the treatment plan information. The dose may be calculated using the log file.

According to a third aspect of the present invention, there is provided a dose calculation method in which a homogeneous substance is present in an irradiation field that irradiates the patient with therapeutic radiation based on a CT image of the patient and treatment plan information generated by the treatment planning apparatus. A step of identifying a homogeneous material region and a heterogeneous material region where a heterogeneous material exists, and after converting the heterogeneous material region into an equivalent region to the homogeneous material region based on the treatment plan information And calculating a dose when the therapeutic radiation is irradiated to the irradiation field using Clarkson method.

Dose calculation program according to claim 4 is a computer, a dose calculation program for functioning as a respective part of the dose calculation apparatus according to claim 1 or claim 2, wherein.

Claims (6)

Based on the CT image of the patient and the treatment plan information generated by the treatment planning apparatus, the homogeneous field where the homogeneous material exists and the non-homogeneous material exist in the irradiation field where the patient is irradiated with therapeutic radiation. A specific part for identifying a homogeneous material region;
Based on the treatment plan information, after converting the inhomogeneous substance region into an equivalent region to the homogeneous substance region, the dose when the therapeutic radiation is irradiated to the irradiation field using the Clarkson method is calculated. A calculation unit to
Dose calculation device. The calculator is
A dividing unit that divides the irradiation field radially at an equal angle around a dose evaluation point;
A conversion unit that converts a length of a parting line that divides the irradiation field through the heterogeneous material region into a length equivalent to a case where the parting line passes through the homogeneous material region;
A calculating unit that calculates the length of the dividing line by adding the length of the part through which the dividing line passes through the homogeneous material region and the length of the part through the heterogeneous material region converted by the converting unit; ,
Based on the length of the dividing line calculated by the calculation unit, a dose calculation unit that calculates a dose when the therapeutic radiation is irradiated to the irradiation field using Clarkson method;
The dose calculation apparatus according to claim 1, comprising: The conversion unit has a length of a portion passing through the heterogeneous material region based on a physical length of a portion where the dividing line passes through the heterogeneous material region and an electron density of a portion passing through the heterogeneous material region. The dose calculation device according to claim 2, wherein the dividing line is converted into a length equivalent to that when the dividing line passes through the homogeneous material region. The calculation unit obtains a log file that records actual values obtained by actually measuring parameters included in the treatment plan information with a radiation irradiation apparatus, and calculates the dose using the log file instead of the treatment plan information. The dose calculation apparatus according to any one of claims 1 to 3. Based on the CT image of the patient and the treatment plan information generated by the treatment planning apparatus, the homogeneous field where the homogeneous material exists and the non-homogeneous material exist in the irradiation field where the patient is irradiated with therapeutic radiation. Identifying a homogeneous material region;
Based on the treatment plan information, after converting the inhomogeneous substance region into an equivalent region to the homogeneous substance region, the dose when the therapeutic radiation is irradiated to the irradiation field using the Clarkson method is calculated. And steps to
Dose calculation method including Computer
The dose calculation program for functioning as each means of the dose calculation apparatus of any one of Claims 1-4.