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Title: SU-G-TeP1-14: SRS Dose Calculation Accuracy Comparison Between Pencil Beam and Monte Carlo Algorithms

Abstract

Purpose: Stereotactic radiosurgery (SRS) outcomes are related to the delivered dose to the target and to surrounding tissue. We have commissioned a Monte Carlo based dose calculation algorithm to recalculated the delivered dose planned using pencil beam calculation dose engine. Methods: Twenty consecutive previously treated patients have been selected for this study. All plans were generated using the iPlan treatment planning system (TPS) and calculated using the pencil beam algorithm. Each patient plan consisted of 1 to 3 targets and treated using dynamically conformal arcs or intensity modulated beams. Multi-target treatments were delivered using multiple isocenters, one for each target. These plans were recalculated for the purpose of this study using a single isocenter. The CT image sets along with the plan, doses and structures were DICOM exported to Monaco TPS and the dose was recalculated using the same voxel resolution and monitor units. Benchmark data was also generated prior to patient calculations to assess the accuracy of the two TPS against measurements using a micro ionization chamber in solid water. Results: Good agreement, within −0.4% for Monaco and +2.2% for iPlan were observed for measurements in water phantom. Doses in patient geometry revealed up to 9.6% differences for singlemore » target plans and 9.3% for multiple-target-multiple-isocenter plans. The average dose differences for multi-target-single-isocenter plans were approximately 1.4%. Similar differences were observed for the OARs and integral dose. Conclusion: Accuracy of the beam is crucial for the dose calculation especially in the case of small fields such as those used in SRS treatments. A superior dose calculation algorithm such as Monte Carlo, with properly commissioned beam models, which is unaffected by the lack of electronic equilibrium should be preferred for the calculation of small fields to improve accuracy.« less

Authors:
; ; ; ;  [1];  [2]
  1. University of Texas HSC SA, San Antonio, TX (United States)
  2. University North Carolina, Chapel Hill, NC (United States)
Publication Date:
OSTI Identifier:
22649354
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; ALGORITHMS; BEAMS; COMPUTERIZED TOMOGRAPHY; INTEGRAL DOSES; IONIZATION CHAMBERS; MONTE CARLO METHOD; PATIENTS; PLANNING

Citation Formats

Stathakis, S, Defoor, D, Saenz, D, Kirby, N, Papanikolaou, N, and Mavroidis, P. SU-G-TeP1-14: SRS Dose Calculation Accuracy Comparison Between Pencil Beam and Monte Carlo Algorithms. United States: N. p., 2016. Web. doi:10.1118/1.4957004.
Stathakis, S, Defoor, D, Saenz, D, Kirby, N, Papanikolaou, N, & Mavroidis, P. SU-G-TeP1-14: SRS Dose Calculation Accuracy Comparison Between Pencil Beam and Monte Carlo Algorithms. United States. doi:10.1118/1.4957004.
Stathakis, S, Defoor, D, Saenz, D, Kirby, N, Papanikolaou, N, and Mavroidis, P. Wed . "SU-G-TeP1-14: SRS Dose Calculation Accuracy Comparison Between Pencil Beam and Monte Carlo Algorithms". United States. doi:10.1118/1.4957004.
@article{osti_22649354,
title = {SU-G-TeP1-14: SRS Dose Calculation Accuracy Comparison Between Pencil Beam and Monte Carlo Algorithms},
author = {Stathakis, S and Defoor, D and Saenz, D and Kirby, N and Papanikolaou, N and Mavroidis, P},
abstractNote = {Purpose: Stereotactic radiosurgery (SRS) outcomes are related to the delivered dose to the target and to surrounding tissue. We have commissioned a Monte Carlo based dose calculation algorithm to recalculated the delivered dose planned using pencil beam calculation dose engine. Methods: Twenty consecutive previously treated patients have been selected for this study. All plans were generated using the iPlan treatment planning system (TPS) and calculated using the pencil beam algorithm. Each patient plan consisted of 1 to 3 targets and treated using dynamically conformal arcs or intensity modulated beams. Multi-target treatments were delivered using multiple isocenters, one for each target. These plans were recalculated for the purpose of this study using a single isocenter. The CT image sets along with the plan, doses and structures were DICOM exported to Monaco TPS and the dose was recalculated using the same voxel resolution and monitor units. Benchmark data was also generated prior to patient calculations to assess the accuracy of the two TPS against measurements using a micro ionization chamber in solid water. Results: Good agreement, within −0.4% for Monaco and +2.2% for iPlan were observed for measurements in water phantom. Doses in patient geometry revealed up to 9.6% differences for single target plans and 9.3% for multiple-target-multiple-isocenter plans. The average dose differences for multi-target-single-isocenter plans were approximately 1.4%. Similar differences were observed for the OARs and integral dose. Conclusion: Accuracy of the beam is crucial for the dose calculation especially in the case of small fields such as those used in SRS treatments. A superior dose calculation algorithm such as Monte Carlo, with properly commissioned beam models, which is unaffected by the lack of electronic equilibrium should be preferred for the calculation of small fields to improve accuracy.},
doi = {10.1118/1.4957004},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}