SU-E-T-18: Output Dependence on Dose Rate for Uniform Scanning Proton Beams

Medical Physics
E Ramirez, Y Zheng

Abstract

Accurate determination of proton output is critical to ensure accurate proton dose delivery. It was found that the proton output factor was decreased when the dose rate was low. The purpose of the study is to investigate the dose rate effects on proton dose output factors. We systematically measured output (nC/MU) of the proton beam as a function of dose rate for various beam conditions. We first measured dose rate effects for proton beams of three range and modulation combinations: range 16 cm and modulation 10 cm, range 5 cm and modulation 3 cm, and range 30 and modulation 15 cm. We then investigated the dose rate effects for two scanning field sizes, the standard 18×18 cm̂2 and the largest available 25×25 cm̂2. The output factor varied with dose rate, increasing more than 6% when the dose rate increased from 0.1 Gy /minutes to about 2.5 Gy/minute. The output variation on dose rate seems to depend on only the dose rate itself. The effect of proton energy and scanning field size on the dose rate dependence was minimal. The proton dose output factor depends on the dose rate at our facility, and can be large (>5%). This dependence needs to be taken account in output modeling for more accurate proton dose delivery.

Related Concepts

Related Feeds

Buruli Ulcer

Buruli ulcer is a progressive disease of subcutaneous tissues caused by mycobacterium ulcerans. Here is the latest research.

Related Papers

Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics
Kyoko AbeMakoto Sakama
International Journal of Radiation Oncology, Biology, Physics
S M WaldowP E Wallner
© 2022 Meta ULC. All rights reserved