Program Information
A New Concept for Generating a Flat Dose Distribution Without a Flattening Filter
T Tsubouchi*, M Yagi , I SUMIDA , K OGAWA , Osaka University Graduate School of Medicine, Suita, Osaka
Presentations
MO-F-FS1-1 (Monday, July 31, 2017) 4:30 PM - 6:00 PM Room: Four Seasons 1
Purpose: To generate a flat dose distribution with flattening-filter-free mode of linac used in radiotherapy, we developed a new concept in which the way of collision of electrons on a target for X-ray generation was changed. The aim of this study is to validate the new concept by Monte Carlo simulations based on experimental data.
Methods: A L-band electron linac was operated to measure physical characteristics of electrons (energy spectra and spatial distribution) used for the simulations. The linac was also used to generate X-ray by colliding electrons to a tungsten target with the thickness of 4 mm. The target was set perpendicular (1st-position) and at an angle of 80 degree (2nd-position) to the electron beam direction. EBT3 film was used for a spatial dose distribution measurement of both electron and X-ray. The measured X-ray distribution was compared with the simulated one to validate the simulation based on experimental data. After the validation of the simulations, the dose distributions in a virtual water were calculated.
Results: The peak energy of electrons was 14.2 MeV and the full widths at half maximum (FWHM) of electron spatial distribution were 14.1 and 6.2 mm in the lateral- and vertical-direction, respectively. The measured X-rays had the FWHMs of 14.4 and 8.7 mm for 1st-position and 14.3 and 8.7 mm for 2nd-position in the lateral- and vertical-direction, respectively, which were in good agreement with the simulated ones. The results for simulating dose in the water showed that the new concept provided flat dose distributions without a flattening filter.
Conclusion: Our study showed the feasibility of the new concept by demonstrating the simulation based on the experimental data. X-ray generated with this new concept would be low-scatters, high dose rate in addition to a flat dose distribution, and these dosimetric characteristics would offer more efficient treatment.
Funding Support, Disclosures, and Conflict of Interest: There is no Conflict of Interest This work was supported by JSPS KAKENHI Grant Number JP15J06453.
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