SU-E-T-547: Modeling Biological Response to Proton Irradiation and Evaluating Its Potential Clinical Consequences

Journal Article · Mon Jun 15 04:00:00 EDT 2015 · Medical Physics

DOI:https://doi.org/10.1118/1.4924909· OSTI ID:22496263

Taleei, R; Peeler, C; Guan, F; Patel, D; Titt, U; Mirkovic, D; Grosshans, D; Mohan, R ^[1]

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1. Departments of Radiation Physics and Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, TX (United States)

Purpose: In addition to physical uncertainties, proton therapy may also be associated with biologic uncertainties. Currently a generic RBE value of 1.1 is used for treatment planning. In this work the effects of variable RBE, in comparison to a fixed RBE, were evaluated by calculating the effective dose for proton treatments. Methods: The repair misrepair fixation (RMF) model was used to calculate variable proton RBEs. The RBE weighted spread-out Bragg peak (SOBP) dose in water phantom was calculated using Monte Carlo simulation and compared to 1.1 weighted SOBP dose. A head and neck proton treatment was used to evaluate the potential effects, by comparing the head and neck treatment plan computed with a commercial treatment planning system that incorporates fixed RBE of 1.1 and a Monte Carlo treatment planning system that incorporates variable RBE. Results: RBE calculations along the depth of SOBP showed that the RBE at the entrance is approximately 1 and reaches 1.1 near the center of the SOBP. However, in distal regions the RBE rises to higher values (up to 3.5 depending on the cell type). Comparison of commercial treatment plans using a fixed RBE of 1.1 and Monte Carlo using variable RBE showed noticeable differences in the effective dose distributions. Conclusion: The comparison of the treatment planning with fixed and variable RBE shows that using commercial treatment planning systems that incorporate fixed RBE (1.1) could Result in overestimation of the effective dose to part of head and neck target volumes, while underestimating the effective dose to the normal tissue beyond the tumor. The accurate variable RBE as a function of proton beam energy in patient should be incorporated in treatment planning to improve the accuracy of effective dose calculation.

• OSTI ID: 22496263
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 6 Vol. 42; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BRAGG CURVE
COMPUTERIZED SIMULATION
DOSE-RESPONSE RELATIONSHIPS
HEAD
IRRADIATION
MONTE CARLO METHOD
NECK
NEOPLASMS
PROTON BEAMS
RADIATION DOSE DISTRIBUTIONS
RADIOTHERAPY
RBE
THERAPEUTIC USES