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Title: Quantification of Proton Dose Calculation Accuracy in the Lung

Abstract

Purpose: To quantify the accuracy of a clinical proton treatment planning system (TPS) as well as Monte Carlo (MC)–based dose calculation through measurements and to assess the clinical impact in a cohort of patients with tumors located in the lung. Methods and Materials: A lung phantom and ion chamber array were used to measure the dose to a plane through a tumor embedded in the lung, and to determine the distal fall-off of the proton beam. Results were compared with TPS and MC calculations. Dose distributions in 19 patients (54 fields total) were simulated using MC and compared to the TPS algorithm. Results: MC increased dose calculation accuracy in lung tissue compared with the TPS and reproduced dose measurements in the target to within ±2%. The average difference between measured and predicted dose in a plane through the center of the target was 5.6% for the TPS and 1.6% for MC. MC recalculations in patients showed a mean dose to the clinical target volume on average 3.4% lower than the TPS, exceeding 5% for small fields. For large tumors, MC also predicted consistently higher V5 and V10 to the normal lung, because of a wider lateral penumbra, which was alsomore » observed experimentally. Critical structures located distal to the target could show large deviations, although this effect was highly patient specific. Range measurements showed that MC can reduce range uncertainty by a factor of ∼2: the average (maximum) difference to the measured range was 3.9 mm (7.5 mm) for MC and 7 mm (17 mm) for the TPS in lung tissue. Conclusion: Integration of Monte Carlo dose calculation techniques into the clinic would improve treatment quality in proton therapy for lung cancer by avoiding systematic overestimation of target dose and underestimation of dose to normal lung. In addition, the ability to confidently reduce range margins would benefit all patients by potentially lowering toxicity.« less

Authors:
 [1]; ; ; ; ;  [1]
  1. Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts (United States)
Publication Date:
OSTI Identifier:
22416591
Resource Type:
Journal Article
Journal Name:
International Journal of Radiation Oncology, Biology and Physics
Additional Journal Information:
Journal Volume: 89; Journal Issue: 2; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0360-3016
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; COMPARATIVE EVALUATIONS; LUNGS; MONTE CARLO METHOD; NEOPLASMS; PATIENTS; PHANTOMS; PLANNING; PROTON BEAMS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY; TOXICITY

Citation Formats

Grassberger, Clemens, Center for Proton Radiotherapy, Paul Scherrer Institute, Villigen, Daartz, Juliane, Dowdell, Stephen, Ruggieri, Thomas, Sharp, Greg, and Paganetti, Harald. Quantification of Proton Dose Calculation Accuracy in the Lung. United States: N. p., 2014. Web. doi:10.1016/J.IJROBP.2014.02.023.
Grassberger, Clemens, Center for Proton Radiotherapy, Paul Scherrer Institute, Villigen, Daartz, Juliane, Dowdell, Stephen, Ruggieri, Thomas, Sharp, Greg, & Paganetti, Harald. Quantification of Proton Dose Calculation Accuracy in the Lung. United States. https://doi.org/10.1016/J.IJROBP.2014.02.023
Grassberger, Clemens, Center for Proton Radiotherapy, Paul Scherrer Institute, Villigen, Daartz, Juliane, Dowdell, Stephen, Ruggieri, Thomas, Sharp, Greg, and Paganetti, Harald. 2014. "Quantification of Proton Dose Calculation Accuracy in the Lung". United States. https://doi.org/10.1016/J.IJROBP.2014.02.023.
@article{osti_22416591,
title = {Quantification of Proton Dose Calculation Accuracy in the Lung},
author = {Grassberger, Clemens and Center for Proton Radiotherapy, Paul Scherrer Institute, Villigen and Daartz, Juliane and Dowdell, Stephen and Ruggieri, Thomas and Sharp, Greg and Paganetti, Harald},
abstractNote = {Purpose: To quantify the accuracy of a clinical proton treatment planning system (TPS) as well as Monte Carlo (MC)–based dose calculation through measurements and to assess the clinical impact in a cohort of patients with tumors located in the lung. Methods and Materials: A lung phantom and ion chamber array were used to measure the dose to a plane through a tumor embedded in the lung, and to determine the distal fall-off of the proton beam. Results were compared with TPS and MC calculations. Dose distributions in 19 patients (54 fields total) were simulated using MC and compared to the TPS algorithm. Results: MC increased dose calculation accuracy in lung tissue compared with the TPS and reproduced dose measurements in the target to within ±2%. The average difference between measured and predicted dose in a plane through the center of the target was 5.6% for the TPS and 1.6% for MC. MC recalculations in patients showed a mean dose to the clinical target volume on average 3.4% lower than the TPS, exceeding 5% for small fields. For large tumors, MC also predicted consistently higher V5 and V10 to the normal lung, because of a wider lateral penumbra, which was also observed experimentally. Critical structures located distal to the target could show large deviations, although this effect was highly patient specific. Range measurements showed that MC can reduce range uncertainty by a factor of ∼2: the average (maximum) difference to the measured range was 3.9 mm (7.5 mm) for MC and 7 mm (17 mm) for the TPS in lung tissue. Conclusion: Integration of Monte Carlo dose calculation techniques into the clinic would improve treatment quality in proton therapy for lung cancer by avoiding systematic overestimation of target dose and underestimation of dose to normal lung. In addition, the ability to confidently reduce range margins would benefit all patients by potentially lowering toxicity.},
doi = {10.1016/J.IJROBP.2014.02.023},
url = {https://www.osti.gov/biblio/22416591}, journal = {International Journal of Radiation Oncology, Biology and Physics},
issn = {0360-3016},
number = 2,
volume = 89,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 2014},
month = {Sun Jun 01 00:00:00 EDT 2014}
}