Calculation of Dose Distribution for SBRT Patient Using Geant4 Simulation Code

Jeongku Kang; Jeongok Lee; Dong Joon Lee

doi:10.14316/pmp.2015.26.1.36

Journal List > Prog Med Phys > v.26(1) > 1098497

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Kang, Lee, and Lee: Calculation of Dose Distribution for SBRT Patient Using Geant4 Simulation Code

Original Article

Progress in Medical Physics 2015;26(1):36-41.

Published online: 20 March 2015

DOI: https://doi.org/10.14316/pmp.2015.26.1.36

Calculation of Dose Distribution for SBRT Patient Using Geant4 Simulation Code

Jeongku Kang^∗, Jeongok Lee^†, Dong Joon Lee^‡

^∗Department of Radiation Oncology, Presbyterian Medical Center, Jeonju, Korea

^†Department of Radiology, Wonkwang Health Science University, Iksan, Korea

^‡Department of Neurosurgery, Ilsan Paik Hospital, School of Medicine, Inje University, Goyang, Korea

Correspondence: Dong Joon Lee(djlee@paik.ac.kr) Tel:82-31-910-7730, Fax:82-31-915-0885

Received 25 February 2015 Revised 5 March 2015 Accepted 8 March 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Monte Carlo based dose calculation program for stereotactic body radiotherapy was developed in this study. The Geant4 toolkit widely used in the radiotherapy was used for this study. The photon energy spectrum of the medical linac studied in the previous research was applied for the patient dose calculations. The geometry of the radiation fields defined by multi-leaf collimators were taken into account in the PrimaryGeneratorAction class of the Geant4 code. The total of 8 fields were demonstrated in the patient dose calculations, where rotation matrix as a function of gantry angle was used for the determination of the source positions. The DicomHandler class converted the binary file format of the DICOM data containing the matrix number, pixel size, endian type, HU number, bit size, padding value and high bits order to the ASCII file format. The patient phantom was constructed using the converted ASCII file. The EGSnrc code was used to compare the calculation efficiency of the material data.

Keywords: Monte Carlo, dicom, SBRT, Geant4

References

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Fig. 1.

The isodose distributions for the center slice of the CT data. (a) dose distributions from iPLan, (b) dose distributions in this study.

Fig. 2.

Dose distributions of the lateral slices, (a) dose distributions from iPLan, (b) dose distributions in this study.

Table 1.

Compositions by fractional weight of the materials used in the BEAMnrc default method and their mass densit ranges.

#	Material	ρ (gcm⁻³) range	Fraction by weight
#	Material	ρ (gcm⁻³) range	H	C	N	O	Na	Mg	P	S	Cl	Ar	K	Ca	Zn
0	Air	0.044			75.5	23.2						1.3
1	Lung	0.302	10.3	10.5	3.1	74.9	0.2		0.2	0.3	0.3		0.2
2	Soft	1.101	10.1	11.1	2.6	76.2
3	Bone	2.088	4.72	14.43	4.2	44.61		0.22	10.5	0.32				20.99	0.01

Table 2.

The treatment planning parameters for a patient in the iPlan system.

Object name	Object type	Dose/fraction	No. of fraction	Total dose	Normalization mode
Tumor L4	PTV	10.0 Gy	4	80.0%=40.00 Gy	93.5% covers 99.5% of
					target volume

Table 3.

The field parameters for a SBRT patient.

Name	Depth equiv. (mm)	Abs. dose (Gy)	Rel. dose (%)	MU
IMRT Beam1	46.9	7.18	14.4	4,288.0
IMRT Beam2	119.8	5.07	10.1	4,076.0
IMRT Beam3	63.0	8.26	16.5	3,776.0
IMRT Beam4	52.4	8.16	16.3	3,848.0
IMRT Beam5	85.7	7.63	15.3	3,524.0
IMRT Beam6	111.2	5.88	11.8	3,620.0
IMRT Beam7	48.7	3.94	7.9	3,736.0
IMRT Beam8	77.4	6.74	13.5	3,992.0

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