SU‐FF‐T‐391: Simplified Monte Carlo Simulation for Absolute Dose Distribution of IMRT

C. Lee, M. Lin, T. Chao, C. Tung

Research output: Contribution to journalArticle

Abstract

Purpose: A simple method was proposed to incorporate heterogeneous fluence distribution due to time‐dependent leaf motion of IMRT delivery into Monte Carlo based static dose calculation to predict the dose distribution inside a patient and the transmission dose distribution at the EPID. Method and Materials: Weighting factors stored in an efficiency map was incorporated into an open photon field of the Monte Carlo simulation (BEAMnrc, 2005) to mimic the heterogeneous fluence distribution of an IMRT field. The efficiency map was obtained by dividing the measured in‐air IMRT absolute dose distribution to that of the same open field using an aS500 EPID (Varian, Palo Alto, CA) which was carefully calibrated for absolute dose measurement. The EPID was setup at 140 cm SDD and 3.84 mm polystyrene phantom was used for the 6 MV photon beam to ensure full electronic buildup. Absolute dose calibration of Monte Carlo simulation was performed under a standard setup where absolute dose at a reference point was verified by ion chamber measurement. Transmission dose comparison at the EPID for two dynamic wedge fields and two IMRT fields as well as absolute dose distributions at the midplane (SAD=100cm) of a 24.8 cm polystyrene phantom among film dosimetry, EPID measurement and Monte Carlo simulation will be presented. Results: Max discrepancy of 3.3% was observed along the central axis for F1 IMRT field. In addition, penumbra along the field edge of the Monte Carlo simulation appeared to be 1–3 mm wider than EPID and film dosimetry. Conclusion: A simplified method to incoporate heterogeneous fluence distribution of IMRT fields into static Monte Carlo simulation for absolute dose verification was proven feasible. The system can also serve as an independent absolute dose check system to commercial TPS calculation.

Original languageEnglish (US)
Pages (from-to)2135-2136
Number of pages2
JournalMedical Physics
Volume33
Issue number6
DOIs
StatePublished - Jan 1 2006

Fingerprint

Film Dosimetry
Polystyrenes
Photons
Calibration
Ions

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

SU‐FF‐T‐391 : Simplified Monte Carlo Simulation for Absolute Dose Distribution of IMRT. / Lee, C.; Lin, M.; Chao, T.; Tung, C.

In: Medical Physics, Vol. 33, No. 6, 01.01.2006, p. 2135-2136.

Research output: Contribution to journalArticle

@article{4d89d05992694f1594a3e7e076baace9,
title = "SU‐FF‐T‐391: Simplified Monte Carlo Simulation for Absolute Dose Distribution of IMRT",
abstract = "Purpose: A simple method was proposed to incorporate heterogeneous fluence distribution due to time‐dependent leaf motion of IMRT delivery into Monte Carlo based static dose calculation to predict the dose distribution inside a patient and the transmission dose distribution at the EPID. Method and Materials: Weighting factors stored in an efficiency map was incorporated into an open photon field of the Monte Carlo simulation (BEAMnrc, 2005) to mimic the heterogeneous fluence distribution of an IMRT field. The efficiency map was obtained by dividing the measured in‐air IMRT absolute dose distribution to that of the same open field using an aS500 EPID (Varian, Palo Alto, CA) which was carefully calibrated for absolute dose measurement. The EPID was setup at 140 cm SDD and 3.84 mm polystyrene phantom was used for the 6 MV photon beam to ensure full electronic buildup. Absolute dose calibration of Monte Carlo simulation was performed under a standard setup where absolute dose at a reference point was verified by ion chamber measurement. Transmission dose comparison at the EPID for two dynamic wedge fields and two IMRT fields as well as absolute dose distributions at the midplane (SAD=100cm) of a 24.8 cm polystyrene phantom among film dosimetry, EPID measurement and Monte Carlo simulation will be presented. Results: Max discrepancy of 3.3{\%} was observed along the central axis for F1 IMRT field. In addition, penumbra along the field edge of the Monte Carlo simulation appeared to be 1–3 mm wider than EPID and film dosimetry. Conclusion: A simplified method to incoporate heterogeneous fluence distribution of IMRT fields into static Monte Carlo simulation for absolute dose verification was proven feasible. The system can also serve as an independent absolute dose check system to commercial TPS calculation.",
author = "C. Lee and M. Lin and T. Chao and C. Tung",
year = "2006",
month = "1",
day = "1",
doi = "10.1118/1.2241309",
language = "English (US)",
volume = "33",
pages = "2135--2136",
journal = "Medical Physics",
issn = "0094-2405",
publisher = "AAPM - American Association of Physicists in Medicine",
number = "6",

}

TY - JOUR

T1 - SU‐FF‐T‐391

T2 - Simplified Monte Carlo Simulation for Absolute Dose Distribution of IMRT

AU - Lee, C.

AU - Lin, M.

AU - Chao, T.

AU - Tung, C.

PY - 2006/1/1

Y1 - 2006/1/1

N2 - Purpose: A simple method was proposed to incorporate heterogeneous fluence distribution due to time‐dependent leaf motion of IMRT delivery into Monte Carlo based static dose calculation to predict the dose distribution inside a patient and the transmission dose distribution at the EPID. Method and Materials: Weighting factors stored in an efficiency map was incorporated into an open photon field of the Monte Carlo simulation (BEAMnrc, 2005) to mimic the heterogeneous fluence distribution of an IMRT field. The efficiency map was obtained by dividing the measured in‐air IMRT absolute dose distribution to that of the same open field using an aS500 EPID (Varian, Palo Alto, CA) which was carefully calibrated for absolute dose measurement. The EPID was setup at 140 cm SDD and 3.84 mm polystyrene phantom was used for the 6 MV photon beam to ensure full electronic buildup. Absolute dose calibration of Monte Carlo simulation was performed under a standard setup where absolute dose at a reference point was verified by ion chamber measurement. Transmission dose comparison at the EPID for two dynamic wedge fields and two IMRT fields as well as absolute dose distributions at the midplane (SAD=100cm) of a 24.8 cm polystyrene phantom among film dosimetry, EPID measurement and Monte Carlo simulation will be presented. Results: Max discrepancy of 3.3% was observed along the central axis for F1 IMRT field. In addition, penumbra along the field edge of the Monte Carlo simulation appeared to be 1–3 mm wider than EPID and film dosimetry. Conclusion: A simplified method to incoporate heterogeneous fluence distribution of IMRT fields into static Monte Carlo simulation for absolute dose verification was proven feasible. The system can also serve as an independent absolute dose check system to commercial TPS calculation.

AB - Purpose: A simple method was proposed to incorporate heterogeneous fluence distribution due to time‐dependent leaf motion of IMRT delivery into Monte Carlo based static dose calculation to predict the dose distribution inside a patient and the transmission dose distribution at the EPID. Method and Materials: Weighting factors stored in an efficiency map was incorporated into an open photon field of the Monte Carlo simulation (BEAMnrc, 2005) to mimic the heterogeneous fluence distribution of an IMRT field. The efficiency map was obtained by dividing the measured in‐air IMRT absolute dose distribution to that of the same open field using an aS500 EPID (Varian, Palo Alto, CA) which was carefully calibrated for absolute dose measurement. The EPID was setup at 140 cm SDD and 3.84 mm polystyrene phantom was used for the 6 MV photon beam to ensure full electronic buildup. Absolute dose calibration of Monte Carlo simulation was performed under a standard setup where absolute dose at a reference point was verified by ion chamber measurement. Transmission dose comparison at the EPID for two dynamic wedge fields and two IMRT fields as well as absolute dose distributions at the midplane (SAD=100cm) of a 24.8 cm polystyrene phantom among film dosimetry, EPID measurement and Monte Carlo simulation will be presented. Results: Max discrepancy of 3.3% was observed along the central axis for F1 IMRT field. In addition, penumbra along the field edge of the Monte Carlo simulation appeared to be 1–3 mm wider than EPID and film dosimetry. Conclusion: A simplified method to incoporate heterogeneous fluence distribution of IMRT fields into static Monte Carlo simulation for absolute dose verification was proven feasible. The system can also serve as an independent absolute dose check system to commercial TPS calculation.

UR - http://www.scopus.com/inward/record.url?scp=85024801958&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85024801958&partnerID=8YFLogxK

U2 - 10.1118/1.2241309

DO - 10.1118/1.2241309

M3 - Article

AN - SCOPUS:85024801958

VL - 33

SP - 2135

EP - 2136

JO - Medical Physics

JF - Medical Physics

SN - 0094-2405

IS - 6

ER -