JP2010057656A - Radiation quality, calculation method, and calculation program of biological effectiveness of heavy particle beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calculation method calculating biological effectiveness of heavy particle beam when irradiating the heavy particle beam in a short period of time without depending on the type and energy of the particles. <P>SOLUTION: A first Monte Carlo code taking no account of secondary electron and account of only an energy imparted along a course, a second Monte Carlo code taking account of an energy which the secondary electron 7 generated along the course applies to a medium, and a data conversion code for converting particle data of the first Monte Carlo code into particle data of the second Monte Carlo code, are installed into a computer, a heavy particle beam and physical property data of a target and an object are input therein, a transport of the heavy particle beam from colliding on the target and being dispersed till entering a code changeover position is calculated by the first Monte Carlo code, the particle data of the first Monte Carlo code are converted into the particle data of the second Monte Carlo code at the code changeover position, and the transport from the code changeover position into the object is calculated by the second Monte Carlo code. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a calculation method and calculation program for the quality and biological effects of a heavy particle beam.

  For example, Patent Documents 1 to 3 disclose a dose calculation method for calculating a dose distribution in an object irradiated with radiation by a radiation irradiation apparatus by computer simulation. A technique related to the present invention is disclosed in Non-Patent Document 1.

JP 2000-507848, "Calculation of radiation therapy dose using whole particle Monte Carlo transport" JP 2002-336365 A, “Dose Simulation Calculation Method” JP 2004-41292 A, “Dose Calculation Method”

Y. Kase, et. al, “Microscopic Measurements and Estimates of Human Cell Survival for Heavy-Ion Beams”, RADIATION RESEARCH 166, 629-638 (2006)

When evaluating the interaction between a heavy particle beam (for example, C, Ne, Si, Ar ions) and the human body, the quality of the particle beam (such as the application of linear energy or linear energy) and the effect of the particle beam on the human body (Biological effect) needs to be evaluated in detail.
That is, in heavy ion radiotherapy, in addition to physical dose, biological dose considering radiation quality is the evaluation standard for administration dose. Heavy particle beams cause nuclear fragmentation in the material and break up into smaller particles, and the beam is a mixture of various particles with different energization and scattering characteristics. Therefore, a method that does not depend on the type or energy of particles is desirable as a method for evaluating the quality of radiation.
However, in Patent Literatures 1 to 3, for example, dose distributions of electromagnetic radiation and fine particle radiation for a target such as a tumor are calculated, but evaluation of radiation quality and biological effect has not been made.

  The present invention has been developed to solve the above-described conventional problems. That is, an object of the present invention is to provide a particle beam having a quality (radiation intensity) and a particle beam when a target is irradiated with a heavy particle beam (for example, C, Ne, Si, Ar ions). Provides a method and program for calculating the quality and biological effects of heavy particle beams that can be used to evaluate the effects (biological effects) on the particle in detail and reduce the calculation time without depending on the type or energy of the particles. There is to do.

According to the present invention, when the particle beam passes through the medium, the first Monte Carlo code for performing the transport calculation by the Monte Carlo method without considering the secondary electrons and considering only the energy application along the path is made to the computer. When,
A second Monte Carlo code that performs transport calculation by the Monte Carlo method in consideration of energy application along the path and energy given to the medium by secondary electrons generated along the path;
A data conversion code for converting the first Monte Carlo code particle data into the second Monte Carlo code particle data; and
Input the heavy ion beam, target and object position and physical property data and the code switching position near the upstream side of the object to the computer,
The first Monte Carlo code performs a transport calculation until the heavy particle beam collides with the target, is dispersed, and enters the code switching position by a computer,
Converting the first Monte Carlo code particle data into the second Monte Carlo code particle data at the code switching position;
Transport calculation within the object from the code switching position is performed with the second Monte Carlo code,
There is provided a method for calculating the quality of a heavy particle beam and the biological effect, wherein the absorbed dose and biological effect of the heavy particle beam received by the object are output.

Further, according to the present invention, when the particle beam passes through the medium, the first Monte Carlo code that performs the transport calculation by the Monte Carlo method without considering the secondary electrons and considering only the energy application along the path,
A second Monte Carlo code that performs transport calculation by the Monte Carlo method in consideration of energy application along the path and energy given to the medium by secondary electrons generated along the path;
A data conversion code for converting the first Monte Carlo code particle data into the second Monte Carlo code particle data;
Let the computer input the heavy ion beam, target and object position and physical property data and the code switching position near the upstream side of the object to the computer,
The first Monte Carlo code performs a transport calculation until the heavy particle beam collides with the target, is dispersed and enters the code switching position,
Converting the particle data of the first Monte Carlo code to the particle data of the second Monte Carlo code at the code switching position;
Causing the second Monte Carlo code to execute the transport calculation within the object from the code switching position;
There is provided a program for calculating the quality and biological effect of a heavy particle beam, which outputs the linear energy received by the object, the absorbed dose of the heavy particle beam, and the biological effect.

  Conventionally, in calculating dose and radiation quality, a simple calculation method using analytical formulas or a general-purpose Monte Carlo code is used.

However, when evaluating the interaction between the particle beam and the human body, it is necessary to evaluate the biological effects due to the radiation quality in addition to the physical dose. A simple calculation method is not provided with a method that fully considers the effect of radiation quality.
On the other hand, there are a number of computer programs (Monte Carlo codes) that perform transport calculations using the Monte Carlo method. However, each Monte Carlo code has its pros and cons, and there is a problem in that the calculation accuracy decreases or the calculation time is slow under certain conditions. there were.

In the calculation method and calculation program of the present invention, a first Monte Carlo code that does not consider secondary electrons and a second Monte Carlo code that considers secondary electrons are used, and particle beam data is transferred between the two Monte Carlo codes. Two Monte Carlo codes are used for one calculation target system using an interface (data conversion code).
That is, each Monte Carlo code performs calculations in an area where the calculation accuracy or calculation speed is excellent, so that dose and radiation quality can be evaluated with high accuracy in a relatively short calculation time. As a result, detailed evaluation of the effects (biological dose) of particle beams on the human body became possible.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

FIG. 1 is a diagram showing dose distributions of various types of radiation in a living body. In this figure, the horizontal axis is the depth (cm) from the body surface, and the vertical axis is the relative dose.
As shown in this figure, in an uncharged particle having no electric charge such as a photon beam or a neutron beam, the number of particles attenuates exponentially with the depth in the body. On the other hand, when high-energy charged particles are irradiated into the body, they proceed while gradually losing energy due to Coulomb scattering, and suddenly lose energy near the range. For this reason, the deep dose distribution has a portion giving a high dose called a Bragg peak near the range. By matching this part with the position of the tumor, the dose can be concentrated on the tumor.
Carbon, neon, silicon, argon and the like are known as high energy charged particles.

FIG. 2 is a survival rate curve of cells irradiated with X-rays and heavy particle beams. In this figure, the horizontal axis represents the absorbed dose (Gy), and the vertical axis represents the cell viability S.
As shown in this figure, when the cell survival rate S is the same (e.g. 0.1), the absorbed dose D of heavy particle beam than absorbed dose D ₀ of the X-ray becomes a small value. In other words, when the cells are killed by irradiating the tumor with X-rays and heavy particle beams, the heavy cell beams can achieve the same cell survival rate S at a lower dose than the X-rays.

In this figure, the relationship between the absorbed dose D (Gy) of the heavy particle beam and the cell viability S (−) can be expressed by equation (1). Here, α and β are parameters for each cell and radiation quality.
S = exp (−α · D−β · D ² ) (1)

Further, the ratio D ₀ / D between the absorbed dose D _{0 of} X-rays and the absorbed dose D of heavy particle beams that achieves the same cell viability S (for example, 0.1) is defined as a biological effect (Relativistic Biological Effect: RBE). To do. Therefore, the biological effect (RBE) is generally a positive number greater than one.

FIG. 3 is a diagram showing a physical dose and a biological dose of a heavy particle beam in a living body. In this figure, the horizontal axis represents the depth (cm) from the body surface, and the vertical axis represents the relative dose (%).
In this figure, the physical dose corresponds to the absorbed dose of the heavy particle beam in FIG. 1, but in radiotherapy, it is necessary to evaluate the treatment dose with the biological dose taking into account the biological effect (RBE) described above. There is.

In the present invention, the quality of particle beam means the intensity of radiation, and is expressed by linear energy transfer (LET). The line energy y (LET) represents the amount of energy locally absorbed by charged particles per unit length.
In contrast, the average energy that a charged particle loses when passing through a unit length is called “stopping power”. The linear energy (LET) when charged particles pass through living tissue or gas is almost equal to the stopping power.
Further, it is known that the parameter α in the equation (1) can be given as a function of the line energy y.
This relational expression is α = f (y) (2).

When the high energy charged particles are different, for example, even when carbon, neon, silicon, argon, etc. are mixed, the same biological effect (RBE) can be obtained if the above-described linear energy y (LET) is the same. it can.
That is, the parameter β in the formula (1) is a constant value if the cells and the radiation quality are the same. Therefore, when a certain linear energy y (LET) is obtained by analysis or experiment, α is obtained from the equation (2), and the heavy particle beam for the same cell viability S (for example, 0.1) is obtained from the equation (1). The absorbed dose D is determined.
Furthermore, since the absorbed dose D ₀ of X-rays is known, a biological effect (RBE) can be obtained as D ₀ / D.

FIG. 4 is a schematic diagram of a system to be analyzed by the present invention. This analysis target assumes a particle beam cancer treatment apparatus. In the figure, high-energy charged particles 1 (for example, ¹² C) are incident from the left side, collide with the target 2 and are dispersed, and the dispersed particles 3 are at the right end. A linear energy y is given to an object (not shown) located at.
In this example, the incident direction of the charged particles 1 is the z axis, and one direction perpendicular to the z axis (for example, the horizontal direction) is the x axis. It is assumed that the origins of the x-axis and the z-axis are on the incident surface of the target 2, the charged particle 1 enters from z = −125 cm, and the object (for example, a living body) is at a position of z = 200 cm.
The target 2 is, for example, an aluminum flat plate or water.

In an actual particle beam cancer treatment apparatus, a dipole magnet, a flattening filter, a collimator, a bolus, and the like that control the incident direction of the charged particles 1 are provided, but these are omitted in this example. In addition, even when there are these, it can apply similarly.
Further, the present invention is not limited to the system described above, and can be similarly applied to any other system.

In order to obtain the linear energy y at the position of z = 200 cm in the analysis target of FIG. 4, the present invention performs a transport calculation by the Monte Carlo method. The transport calculation by the Monte Carlo method statistically processes the behavior of secondary electrons that are generated secondarily while calculating what kind of physical phenomenon the charged particle 1 colliding with the target 2 will proceed while causing it. The line energy y given to the object is directly calculated.
Hereinafter, the charged particles 1 and the dispersed particles 3 are collectively referred to as a particle beam 4.

FIG. 5 is a schematic diagram showing an example of a calculation model to which the Monte Carlo method is applied.
As shown in FIG. 5A, when the particle beam 4 passes through the medium 5, energy application 6 is given to the medium 5 along the path (black circle). In FIG. 5B, a large number of secondary electrons 7 (δ line) are generated along the path, and energy 8 is similarly given to the medium 5 (white circles). The range affected by the secondary electron beam 7 is, for example, 1 mm or less from the orbit of the particle beam 4 in the case of a carbon beam having an energy of 290 MeV / n.

  Many computer programs (referred to as Monte Carlo codes) that perform transport calculations by the Monte Carlo method are known. Among them, the Monte Carlo code known by the name of PHITS (hereinafter simply referred to as “PHITS code” or “Code 1”) is: As shown in FIG. 5A, when the particle beam 4 passes through the medium 5, the secondary electrons are not considered but only the energy application 6 along the path is taken into consideration. Further, a Monte Carlo code known by the name of GEANT4 (hereinafter simply referred to as “GEANT4 code” or “code 2”) has a secondary electron beam 7 (δ line) in the medium 5 as shown in FIG. The energy 8 to be given is also taken into consideration.

The characteristics of each calculation code are as follows.
PHITS code (1) The calculation speed is high because the δ ray transport calculation is not performed.
(2) The calculation accuracy of energy application decreases in a region where the calculation accuracy in a minute region is smaller than the region affected by the δ line. This is because the calculation of transport of δ rays is not performed, and the influence of δ rays imparting energy outside the region is also calculated as energy provision within the region.
(3) The calculation accuracy is high in the transport calculation that does not consider energy application or in the calculation of energy application in a relatively large area because the calculation process is simple.

GEANT4 code (1) The calculation speed is slow.
(2) The calculation accuracy does not decrease even in a small area.
(3) Since many calculation processes and models are included, the calculation accuracy is slightly inferior. This is because the evaluation of energy lost by particles is relatively easy and experimental verification is possible, but the energy of the generated δ rays is difficult to verify, and errors in the calculation model may accumulate.

  FIG. 6 is a flowchart showing a method for calculating the quality and biological effect of a heavy particle beam according to the present invention. As shown in this figure, the method of the present invention comprises steps S1 to S9.

  In step S1, the heavy particle beam (heavy particle beam 4), the position and physical property data of the target and the object, and the code switching position near the upstream side of the object are input to the computer. The data of the heavy particle beam includes coordinates, energy [Mev / n], velocity vector, and particle type in accordance with data used in the first Monte Carlo code (PHITS code in this example).

Next, along the path of the heavy particle beam 4, the coordinate z is changed with a constant displacement Δz (step S2), and the transport calculation is performed with the first Monte Carlo code (PHITS code in this example) (step S3). Steps S2 and S3 are repeated until the coordinate z reaches the code switching position z1 (step S4).
Here, the “code switching position z1” is set at a position where the heavy particle beam 4 collides with the target, is dispersed and enters the object (for example, the surface of the body), or in the vicinity of the upstream side. Good.

  When the coordinate z reaches the code switching position z1, the heavy particle beam data at that time is converted into particle data of a second Monte Carlo code (GEANT4 code in this example) (step S5). The particle data of the second Monte Carlo code includes coordinates, momentum [MeV / c], particle type, and mass [Mev].

In the PHITS code, the energy of particles is given by the kinetic energy (E _k ) and the velocity vector (u, v, w), whereas in the GEANT4 code, the energy is input by the momentum vector (p _x , p _y , p _z ). To do. For this reason, the conversion is performed using Equation (3) in Equation 1. Here, Mc ² is mass energy.

The particle type is identified by an integer according to a specific rule in both the PHITS code and the GEANT4 code.
For example, in the case of an atomic nucleus, it is expressed as Z × 10 ⁶ + A in the PHITS code, and 10 ⁹ + Z × 10 ⁴ + A × 10 in the GEANT4 code. Here, A is the mass number and Z is the atomic number.
For example, if it is ¹² C, it will be 6000012 for the PHITS code and 10000060120 for the GEANT4 code.
Further, in the PHITS code, the atomic number Z and the mass number A are read from this notation, but in the GEANT4 code, it is necessary to input the mass M in units of [MeV]. For this reason, conversion is performed by the following equation (4).
M = 931.494 · A [MeV] (4)

  Next, along the path of the heavy particle beam, the coordinate z is changed with a constant displacement Δz (step S6), and the transport calculation is performed with the second Monte Carlo code (GEANT4 code in this example) (step S7). Steps S6 and S7 are repeated until the coordinate z reaches the analysis target position z2 (step S8).

Next, in step S9, the linear energy y received by the object at the analysis target position z2 is calculated, and the absorbed dose D of the heavy particle beam with respect to the predetermined cell survival rate S is calculated therefrom. Further, the predetermined absorbed dose of X-rays A biological effect (RBE) is obtained from D ₀ to D ₀ / D.

FIG. 7 is a diagram showing a first embodiment of the present invention. In this figure, (A) shows the line energy y at the analysis target position, and (B) shows the biological effect RBE at the analysis target position. In this embodiment, in the analysis target of FIG. 4, the position of Z = 190 cm is the code switching position, and the position of z = 200 cm is the analysis target position.
In each figure, the horizontal axis is the x-coordinate of the position to be analyzed, the thin line A in the figure is the analysis result using only the PHITS code, the black circle C (● mark) in the figure is the analysis result according to the present invention, and the black angle D in the figure (■ mark) is an actual measurement value measured with a tissue equivalent proportional counter (lossy counter).

The tissue equivalent proportional counter (Rossi counter) is a counter tube in which a tissue equivalent gas (diameter: 12.7 mm, pressure: 4.40 kPa) having a tissue equivalent length of 1 μm is enclosed, and is μm based on a biological effect evaluation method (Microdosimetry). Energy application measurement is performed in a region having a size of about the same size as the cell nucleus.
That is, based on the assumption that the quality of radiation depends on the variation in energy application in a minute region, in the present invention, the tissue equivalent gas is gas pressure so that the human body equivalent thickness is 1 μm in a spherical counter having a diameter of 12.7 mm. Was adjusted and sealed to simulate the application of energy in a minute region. The evaluation object was the side scattering characteristic of a ¹² C pencil beam. The beam was incident on an Al or water target, the physical dose due to scattering and nuclear fragmentation, and the spatial distribution of the radiation quality were evaluated by Monte Carlo calculation, and the accuracy was verified by comparison with experimental values. The Monte Carlo code used PHITS and GEANT4, each incorporating routines for quality assessment.

From FIG. 7, it can be seen that the analysis result A using only the PHITS code overestimates the linear energy by about 50% and overestimates the biological effect by about 20% compared to the actual measurement value D.
On the other hand, in the analysis result C according to the present invention, the relative error of the line energy is about 20% and the relative error of the biological effect is about 4% as compared with the actual measurement value D. You can see that they match.

FIG. 8 is a diagram showing a second embodiment of the present invention. In this figure, (A) shows the linear energy at the position to be analyzed, and (B) shows the calculation time. In this embodiment, in the analysis target of FIG. 4, the position of Z = 190 cm is the code switching position, and the position of z = 200 cm is the analysis target position.
In FIG. 8A, the horizontal axis is the x coordinate of the position to be analyzed, the inverted triangle A (▼) in the figure is the analysis result using only the PHITS code (code 1), and the diamond B (♦) is the GEANT4 code ( The analysis results based only on code 2), the black circle C (● mark) is the analysis result according to the present invention, and the black angle D (■ mark) is an actual measurement value measured with a tissue equivalent proportional counter (lossy counter).

From this figure, it can be seen that the analysis result C according to the present invention and the analysis result B using only the GEANT4 code (code 2) are in good agreement with the actual measurement value D.
Further, as can be seen from the table of FIG. 8B, the analysis time of the present invention is the analysis time of only the PHITS code (code 1) compared to the analysis time of only the GEANT4 code (code 2) (52 hours). It can be seen that the analysis time is greatly shortened because it is only 14 hours close to.

As described above, for the purpose of application to heavy particle beam cancer treatment, in the present invention, a calculation method and a calculation program for heavy particle beam quality and biological effects using the Monte Carlo code (PHITS and GEANT4) are devised. did. Also, according to the present invention, as a result of comparing the analysis and the experiment with respect to the side scatter distribution of the ¹² C beam, the biological effect was matched within a relative error of about 4%.

The calculation program of the present invention is a computer program for executing the above-described calculation method using a computer.
The calculation program of the present invention includes the first Monte Carlo code, the second Monte Carlo code, and the data conversion code described above.
In addition, this calculation program causes the computer to input the heavy ion beam, the position and physical property data of the target and the object, and the code switching position in the vicinity of the upstream side of the object,
The first Monte Carlo code performs a transport calculation until the heavy particle beam collides with the target, is dispersed and enters the code switching position,
Converting the particle data of the first Monte Carlo code to the particle data of the second Monte Carlo code at the code switching position;
Causing the second Monte Carlo code to execute the transport calculation within the object from the code switching position;
The linear energy received by the object, the absorbed dose of heavy particle beams, and biological effects are output.

As described above, in the calculation method and calculation program of the present invention, the first Monte Carlo code that does not consider secondary electrons and the second Monte Carlo code that considers secondary electrons are used, and the particle beam data between the two Monte Carlo codes is used. Two Monte Carlo codes were used for one calculation target system using an interface (data conversion code) for transferring data.
As a result, the dose and radiation quality can be evaluated with high accuracy in a relatively short calculation time.

Only the PHITS code resulted in overestimation of radiation quality and biological effects as described above. One possible cause is that the PHITS code does not consider the track structure.
FIG. 9 is a ¹² C linear energy probability density distribution diagram. In this figure, A is a PHITS code, C is the present invention, and D is an actual measurement value. From this figure, it is thought that the detector is actually very small and there are many δ lines that jump out of this region, but as a result of omitting this, PHITS code A counts a large number of events indicating high energy application. .
Thus, in the present invention, only the detector portion is recalculated using the GEANT4 code having a track structure calculation model. As a result, as described above, a quality distribution that almost reproduces the experimental results was obtained.

FIG. 10 is a schematic diagram of a particle beam cancer treatment apparatus. In this figure, 1 is an incident particle or charged particle, 2 is a scatterer or target, 9 is a dipole magnet, 10 is a collimator, 11 is a multi-leaf collimator, 12 is a range shifter, 13 is a water phantom, and 14 is a counter. .
The incident particle 1 is a dipole magnet 9 and a scatterer 2 (such as lead) that spatially expands the beam in accordance with the size of the tumor affected area, and further the beam expanded by the collimators 10 and 11 becomes a tumor shape. The beam is focused on.

In addition, a ridge filter that modulates energy is also used, but is omitted in this example.
In recent irradiation methods, there is a method of scanning a beam two-dimensionally with only a dipole magnet without using a scatterer or a collimator. In this case, particles of various energies are implanted without changing the thickness of the range shifter without using a ridge filter.

FIG. 11 is a diagram showing a third embodiment of the present invention. In this example, experimental values were compared with calculated values for the apparatus shown in FIG.
In FIG. 11, the horizontal axis is the water equivalent thickness of the range shifter, the vertical axis is the average value of the line energy, and the rhombus A (♦ mark) in the figure is the result of analysis using only the PHITS code (code 1), the black circle C (● The black square D (■) is an actual measurement value measured with a tissue equivalent proportional counter (lossy counter).
Normally, the counter is moved in water to obtain the distribution in the depth direction. In this case, this was simulated by changing the thickness of the range shifter.

From this figure, calculation A (♦ mark) using only PHITS overestimates the line quality especially in the shallow part. In this region, since the kinetic energy of secondary electrons that generate a large amount of particle beam kinetic energy is also high, it is conceivable that the proportion of secondary electrons that impart energy outside the counter is large.
On the other hand, in the vicinity of the peak, the difference between the PHITS calculation A (♦ mark) and the experimental value D (■ mark) is small. This is because the kinetic energy of the particle beam is small here and the kinetic energy of the generated secondary electrons is low, so the percentage of the electrons that stop in the counter is high, and the difference from the case where the secondary electrons are not taken into consideration. It is thought to be smaller.
This interpretation confirms that secondary electrons have an effect on the quality of radiation.

  In addition, this invention is not limited to embodiment mentioned above, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

It is a figure which shows dose distribution in the living body of various radiation. It is a survival rate curve of the cell irradiated with the X-ray and the heavy particle beam. It is a figure which shows the physical dose and biological dose in the living body of a heavy particle beam. 1 is a schematic diagram of a system to be analyzed by the present invention. It is a schematic diagram which shows the example of the calculation model to which a Monte Carlo method is applied. It is a flowchart which shows the calculation method of the quality and biological effect of a heavy particle beam by this invention. It is a figure which shows 1st Example of this invention. It is a figure which shows 2nd Example of this invention. ^{It is a 12} C linear energy probability density distribution map. It is the schematic of a particle beam cancer treatment apparatus. It is a figure which shows 3rd Example of this invention.

Explanation of symbols

1 charged particle (heavy particle beam, incident particle),
2 targets (scatterers),
3 dispersed particles, 4 particle beams,
5 medium, 6 energy given along the path,
7 secondary electron beam (δ line), 8 energy given by secondary electron,
9 dipole magnet, 10 collimator,
11 Multi-leaf collometer, 12 Range shifter,
13 water phantom, 14 counter

Claims (2)

A first Monte Carlo code that performs a transport calculation by a Monte Carlo method in consideration of only energy application along the path without considering secondary electrons when the particle beam passes through the medium;
A second Monte Carlo code that performs transport calculation by the Monte Carlo method in consideration of energy application along the path and energy given to the medium by secondary electrons generated along the path;
A data conversion code for converting the first Monte Carlo code particle data into the second Monte Carlo code particle data; and
Input the heavy ion beam, target and object position and physical property data and the code switching position near the upstream side of the object to the computer,
The first Monte Carlo code performs a transport calculation until the heavy particle beam collides with the target, is dispersed, and enters the code switching position by a computer,
Converting the first Monte Carlo code particle data into the second Monte Carlo code particle data at the code switching position;
Transport calculation within the object from the code switching position is performed with the second Monte Carlo code,
A method for calculating the radiation quality and biological effect of a heavy particle beam, wherein the absorbed dose and biological effect of the heavy particle beam received by the object are output. When the particle beam passes through the medium, a first Monte Carlo code for performing transport calculation by the Monte Carlo method without considering secondary electrons and considering only energy application along the path;
A second Monte Carlo code that performs transport calculation by the Monte Carlo method in consideration of energy application along the path and energy given to the medium by secondary electrons generated along the path;
A data conversion code for converting the first Monte Carlo code particle data into the second Monte Carlo code particle data;
Let the computer input the heavy ion beam, target and object position and physical property data and the code switching position near the upstream side of the object to the computer,
The first Monte Carlo code performs a transport calculation until the heavy particle beam collides with the target, is dispersed and enters the code switching position,
Converting the particle data of the first Monte Carlo code to the particle data of the second Monte Carlo code at the code switching position;
Causing the second Monte Carlo code to execute the transport calculation within the object from the code switching position;
A program for calculating the radiation quality and biological effect of a heavy particle beam, characterized by outputting the linear energy received by the object, the absorbed dose of the heavy particle beam, and the biological effect.

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