SU-E-T-236: Monte Carlo Calculations for Radiosurgery of the Clivus
Abstract
Purpose: We sought to determine if dosimetric differences exist between Ray-Trace (RT) and Monte-Carlo (MC) calculation algorithms for radiosurgery for tumors of the clivus, given their proximity to air-tissue inhomogeneity. Methods: We retrospectively identified 10 patients with a tumor of the clivus where the target was located near an air-tissue interface. CyberKnife treatment was delivered in 1 to 5 fractions. Plans originally calculated with the RT algorithm were re-calculated with the same monitor units (MU) with the MC algorithm. Similarly, plans originally calculated with MC were recalculated with RT. MC calculations were performed using High Resolution with 2% uncertainty on the MultiPlan 4.6 planning system. If the RT plans were originally calculated using water-air density model, they were re-calculated with Body standard density model, and then compared with MC plans computed with Body standard density model. The maximum dose (Dmax) to the planning target volumes (PTV) and critical structures, minimum dose (Dmin) and coverage percentage for the PTV were calculated. Results: For 8 cases, MC PTV Dmin was a median 5% (range 0–10%) and Dmax a median 6% (range 3–9%) higher than for RT. For 2 cases, MC PTV Dmin was 6 and 2% and Dmax was 1 and 3%more »
- Authors:
-
- Stanford University Hospital, Stanford, CA (United States)
- Publication Date:
- OSTI Identifier:
- 22351143
- Resource Type:
- Journal Article
- Journal Name:
- Medical Physics
- Additional Journal Information:
- Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 60 APPLIED LIFE SCIENCES; 62 RADIOLOGY AND NUCLEAR MEDICINE; ALGORITHMS; ANIMAL TISSUES; MONTE CARLO METHOD; NEOPLASMS; RADIATION DOSES; RADIOTHERAPY; SURGERY
Citation Formats
Ho, A, Gibbs, I, Chang, S, and Soltys, S. SU-E-T-236: Monte Carlo Calculations for Radiosurgery of the Clivus. United States: N. p., 2014.
Web. doi:10.1118/1.4888567.
Ho, A, Gibbs, I, Chang, S, & Soltys, S. SU-E-T-236: Monte Carlo Calculations for Radiosurgery of the Clivus. United States. https://doi.org/10.1118/1.4888567
Ho, A, Gibbs, I, Chang, S, and Soltys, S. 2014.
"SU-E-T-236: Monte Carlo Calculations for Radiosurgery of the Clivus". United States. https://doi.org/10.1118/1.4888567.
@article{osti_22351143,
title = {SU-E-T-236: Monte Carlo Calculations for Radiosurgery of the Clivus},
author = {Ho, A and Gibbs, I and Chang, S and Soltys, S},
abstractNote = {Purpose: We sought to determine if dosimetric differences exist between Ray-Trace (RT) and Monte-Carlo (MC) calculation algorithms for radiosurgery for tumors of the clivus, given their proximity to air-tissue inhomogeneity. Methods: We retrospectively identified 10 patients with a tumor of the clivus where the target was located near an air-tissue interface. CyberKnife treatment was delivered in 1 to 5 fractions. Plans originally calculated with the RT algorithm were re-calculated with the same monitor units (MU) with the MC algorithm. Similarly, plans originally calculated with MC were recalculated with RT. MC calculations were performed using High Resolution with 2% uncertainty on the MultiPlan 4.6 planning system. If the RT plans were originally calculated using water-air density model, they were re-calculated with Body standard density model, and then compared with MC plans computed with Body standard density model. The maximum dose (Dmax) to the planning target volumes (PTV) and critical structures, minimum dose (Dmin) and coverage percentage for the PTV were calculated. Results: For 8 cases, MC PTV Dmin was a median 5% (range 0–10%) and Dmax a median 6% (range 3–9%) higher than for RT. For 2 cases, MC PTV Dmin was 6 and 2% and Dmax was 1 and 3% lower than for RT. MC PTV Dmin and Dmax maybe higher or lower than for RT even though the target coverage for MC was less than for RT (median 4%, range 0–13%) with the same MU used. The degree of differences depends on the location of the target relative to the air-tissue inhomogeneity. Examples are shown that the targets are underdosed near the air-tissue inhomogenity. Conclusion: Monte Carlo dose calculations are recommended for targets near tissue homogeneity such as the clivus. Assuming that Monte Carlo more closely approximates the true dosimetry, the use of Ray Trace could overestimate target coverage.},
doi = {10.1118/1.4888567},
url = {https://www.osti.gov/biblio/22351143},
journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 41,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 2014},
month = {Sun Jun 01 00:00:00 EDT 2014}
}