Measurement-based Monte Carlo dose calculation system for IMRT pretreatment and on-line transit dose verifications

Mu Han Lin, Tsi Chian Chao, Chung Chi Lee, Chuan Jong Tung, Chie Yi Yeh, Ji Hong Hong

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The aim of this study was to develop a dose simulation system based on portal dosimetry measurements and the BEAM Monte Carlo code for intensity-modulated (IM) radiotherapy dose verification. This measurement-based Monte Carlo (MBMC) system can perform, within one systematic calculation, both pretreatment and on-line transit dose verifications. BEAMnrc and DOSXYZnrc 2006 were used to simulate radiation transport from the treatment head, through the patient, to the plane of the aS500 electronic portal imaging device (EPID). In order to represent the nonuniform fluence distribution of an IM field within the MBMC simulation, an EPID-measured efficiency map was used to redistribute particle weightings of the simulated phase space distribution of an open field at a plane above a patient/phantom. This efficiency map was obtained by dividing the measured energy fluence distribution of an IM field to that of an open field at the EPID plane. The simulated dose distribution at the midplane of a homogeneous polystyrene phantom was compared to the corresponding distribution obtained from the Eclipse treatment planning system (TPS) for pretreatment verification. It also generated a simulated transit dose distribution to serve as the on-line verification reference for comparison to that measured by the EPID. Two head-and-neck (NPC1 and NPC2) and one prostate cancer fields were tested in this study. To validate the accuracy of the MBMC system, film dosimetry was performed and served as the dosimetry reference. Excellent agreement between the film dosimetry and the MBMC simulation was obtained for pretreatment verification. For all three cases tested, gamma evaluation with 3%/3 mm criteria showed a high pass percentage (<99.7%) within the area in which the dose was greater than 30% of the maximum dose. In contrast to the TPS, the MBMC system was able to preserve multileaf collimator delivery effects such as the tongue-and-groove effect and interleaf leakage. In the NPC1 field, the TPS showed 16.5% overdose due to the tongue-and-groove effect and 14.6% overdose due to improper leaf stepping. Similarly, in the NPC2 field, the TPS showed 14.1% overdose due to the tongue-and-groove effect and 8.9% overdose due to improper leaf stepping. In the prostate cancer field, the TPS showed 6.8% overdose due to improper leaf stepping. No tongue-and-groove effect was observed for this field. For transit dose verification, agreements among the EPID measurement, the film dosimetry, and the MBMC system were also excellent with a minimum gamma pass percentage of 99.6%.

Original languageEnglish (US)
Pages (from-to)1167-1175
Number of pages9
JournalMedical Physics
Volume36
Issue number4
DOIs
StatePublished - Jan 1 2009

Fingerprint

Film Dosimetry
Tongue
Equipment and Supplies
Prostatic Neoplasms
Head
Therapeutics
Intensity-Modulated Radiotherapy
Polystyrenes
Neck
Radiation

Keywords

  • electronic portal imaging
  • IMRT dose verification
  • Measurement-based simulation
  • Monte Carlo
  • transit dosimetry

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

Measurement-based Monte Carlo dose calculation system for IMRT pretreatment and on-line transit dose verifications. / Lin, Mu Han; Chao, Tsi Chian; Lee, Chung Chi; Tung, Chuan Jong; Yeh, Chie Yi; Hong, Ji Hong.

In: Medical Physics, Vol. 36, No. 4, 01.01.2009, p. 1167-1175.

Research output: Contribution to journalArticle

Lin, Mu Han ; Chao, Tsi Chian ; Lee, Chung Chi ; Tung, Chuan Jong ; Yeh, Chie Yi ; Hong, Ji Hong. / Measurement-based Monte Carlo dose calculation system for IMRT pretreatment and on-line transit dose verifications. In: Medical Physics. 2009 ; Vol. 36, No. 4. pp. 1167-1175.
@article{7c1d9b8355ce4fe78c1fa359cb8ae9ce,
title = "Measurement-based Monte Carlo dose calculation system for IMRT pretreatment and on-line transit dose verifications",
abstract = "The aim of this study was to develop a dose simulation system based on portal dosimetry measurements and the BEAM Monte Carlo code for intensity-modulated (IM) radiotherapy dose verification. This measurement-based Monte Carlo (MBMC) system can perform, within one systematic calculation, both pretreatment and on-line transit dose verifications. BEAMnrc and DOSXYZnrc 2006 were used to simulate radiation transport from the treatment head, through the patient, to the plane of the aS500 electronic portal imaging device (EPID). In order to represent the nonuniform fluence distribution of an IM field within the MBMC simulation, an EPID-measured efficiency map was used to redistribute particle weightings of the simulated phase space distribution of an open field at a plane above a patient/phantom. This efficiency map was obtained by dividing the measured energy fluence distribution of an IM field to that of an open field at the EPID plane. The simulated dose distribution at the midplane of a homogeneous polystyrene phantom was compared to the corresponding distribution obtained from the Eclipse treatment planning system (TPS) for pretreatment verification. It also generated a simulated transit dose distribution to serve as the on-line verification reference for comparison to that measured by the EPID. Two head-and-neck (NPC1 and NPC2) and one prostate cancer fields were tested in this study. To validate the accuracy of the MBMC system, film dosimetry was performed and served as the dosimetry reference. Excellent agreement between the film dosimetry and the MBMC simulation was obtained for pretreatment verification. For all three cases tested, gamma evaluation with 3{\%}/3 mm criteria showed a high pass percentage (<99.7{\%}) within the area in which the dose was greater than 30{\%} of the maximum dose. In contrast to the TPS, the MBMC system was able to preserve multileaf collimator delivery effects such as the tongue-and-groove effect and interleaf leakage. In the NPC1 field, the TPS showed 16.5{\%} overdose due to the tongue-and-groove effect and 14.6{\%} overdose due to improper leaf stepping. Similarly, in the NPC2 field, the TPS showed 14.1{\%} overdose due to the tongue-and-groove effect and 8.9{\%} overdose due to improper leaf stepping. In the prostate cancer field, the TPS showed 6.8{\%} overdose due to improper leaf stepping. No tongue-and-groove effect was observed for this field. For transit dose verification, agreements among the EPID measurement, the film dosimetry, and the MBMC system were also excellent with a minimum gamma pass percentage of 99.6{\%}.",
keywords = "electronic portal imaging, IMRT dose verification, Measurement-based simulation, Monte Carlo, transit dosimetry",
author = "Lin, {Mu Han} and Chao, {Tsi Chian} and Lee, {Chung Chi} and Tung, {Chuan Jong} and Yeh, {Chie Yi} and Hong, {Ji Hong}",
year = "2009",
month = "1",
day = "1",
doi = "10.1118/1.3089790",
language = "English (US)",
volume = "36",
pages = "1167--1175",
journal = "Medical Physics",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "4",

}

TY - JOUR

T1 - Measurement-based Monte Carlo dose calculation system for IMRT pretreatment and on-line transit dose verifications

AU - Lin, Mu Han

AU - Chao, Tsi Chian

AU - Lee, Chung Chi

AU - Tung, Chuan Jong

AU - Yeh, Chie Yi

AU - Hong, Ji Hong

PY - 2009/1/1

Y1 - 2009/1/1

N2 - The aim of this study was to develop a dose simulation system based on portal dosimetry measurements and the BEAM Monte Carlo code for intensity-modulated (IM) radiotherapy dose verification. This measurement-based Monte Carlo (MBMC) system can perform, within one systematic calculation, both pretreatment and on-line transit dose verifications. BEAMnrc and DOSXYZnrc 2006 were used to simulate radiation transport from the treatment head, through the patient, to the plane of the aS500 electronic portal imaging device (EPID). In order to represent the nonuniform fluence distribution of an IM field within the MBMC simulation, an EPID-measured efficiency map was used to redistribute particle weightings of the simulated phase space distribution of an open field at a plane above a patient/phantom. This efficiency map was obtained by dividing the measured energy fluence distribution of an IM field to that of an open field at the EPID plane. The simulated dose distribution at the midplane of a homogeneous polystyrene phantom was compared to the corresponding distribution obtained from the Eclipse treatment planning system (TPS) for pretreatment verification. It also generated a simulated transit dose distribution to serve as the on-line verification reference for comparison to that measured by the EPID. Two head-and-neck (NPC1 and NPC2) and one prostate cancer fields were tested in this study. To validate the accuracy of the MBMC system, film dosimetry was performed and served as the dosimetry reference. Excellent agreement between the film dosimetry and the MBMC simulation was obtained for pretreatment verification. For all three cases tested, gamma evaluation with 3%/3 mm criteria showed a high pass percentage (<99.7%) within the area in which the dose was greater than 30% of the maximum dose. In contrast to the TPS, the MBMC system was able to preserve multileaf collimator delivery effects such as the tongue-and-groove effect and interleaf leakage. In the NPC1 field, the TPS showed 16.5% overdose due to the tongue-and-groove effect and 14.6% overdose due to improper leaf stepping. Similarly, in the NPC2 field, the TPS showed 14.1% overdose due to the tongue-and-groove effect and 8.9% overdose due to improper leaf stepping. In the prostate cancer field, the TPS showed 6.8% overdose due to improper leaf stepping. No tongue-and-groove effect was observed for this field. For transit dose verification, agreements among the EPID measurement, the film dosimetry, and the MBMC system were also excellent with a minimum gamma pass percentage of 99.6%.

AB - The aim of this study was to develop a dose simulation system based on portal dosimetry measurements and the BEAM Monte Carlo code for intensity-modulated (IM) radiotherapy dose verification. This measurement-based Monte Carlo (MBMC) system can perform, within one systematic calculation, both pretreatment and on-line transit dose verifications. BEAMnrc and DOSXYZnrc 2006 were used to simulate radiation transport from the treatment head, through the patient, to the plane of the aS500 electronic portal imaging device (EPID). In order to represent the nonuniform fluence distribution of an IM field within the MBMC simulation, an EPID-measured efficiency map was used to redistribute particle weightings of the simulated phase space distribution of an open field at a plane above a patient/phantom. This efficiency map was obtained by dividing the measured energy fluence distribution of an IM field to that of an open field at the EPID plane. The simulated dose distribution at the midplane of a homogeneous polystyrene phantom was compared to the corresponding distribution obtained from the Eclipse treatment planning system (TPS) for pretreatment verification. It also generated a simulated transit dose distribution to serve as the on-line verification reference for comparison to that measured by the EPID. Two head-and-neck (NPC1 and NPC2) and one prostate cancer fields were tested in this study. To validate the accuracy of the MBMC system, film dosimetry was performed and served as the dosimetry reference. Excellent agreement between the film dosimetry and the MBMC simulation was obtained for pretreatment verification. For all three cases tested, gamma evaluation with 3%/3 mm criteria showed a high pass percentage (<99.7%) within the area in which the dose was greater than 30% of the maximum dose. In contrast to the TPS, the MBMC system was able to preserve multileaf collimator delivery effects such as the tongue-and-groove effect and interleaf leakage. In the NPC1 field, the TPS showed 16.5% overdose due to the tongue-and-groove effect and 14.6% overdose due to improper leaf stepping. Similarly, in the NPC2 field, the TPS showed 14.1% overdose due to the tongue-and-groove effect and 8.9% overdose due to improper leaf stepping. In the prostate cancer field, the TPS showed 6.8% overdose due to improper leaf stepping. No tongue-and-groove effect was observed for this field. For transit dose verification, agreements among the EPID measurement, the film dosimetry, and the MBMC system were also excellent with a minimum gamma pass percentage of 99.6%.

KW - electronic portal imaging

KW - IMRT dose verification

KW - Measurement-based simulation

KW - Monte Carlo

KW - transit dosimetry

UR - http://www.scopus.com/inward/record.url?scp=63849293621&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=63849293621&partnerID=8YFLogxK

U2 - 10.1118/1.3089790

DO - 10.1118/1.3089790

M3 - Article

C2 - 19472622

AN - SCOPUS:63849293621

VL - 36

SP - 1167

EP - 1175

JO - Medical Physics

JF - Medical Physics

SN - 0094-2405

IS - 4

ER -