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Investigation of the Clinical Potential of Scattering Foil Free Electron Beams


A Eldib

A Eldib1,2*, L Jin1, J Li1, C Ma1, (1) Fox Chase Cancer Center, Philadelphia, PA, (2) Department of physics, AlAzhar University, Cairo, Egypt

TU-E-108-10 Tuesday 2:00PM - 3:50PM Room: 108

Purpose:
The photon contamination is a common problem for all advanced modulated electron beam therapy techniques. The scattering foil is one of the major accelerator parts contributing to the generation of bremsstrahlung photons. This work aims to characterize the scattering foil free (SFF) beams from the Siemens Artiste accelerator and to study the feasibility of using those beams for breast cancer boost treatment utilizing our in-house Monte Carlo based treatment planning system.

Methods:
Percentage depth doses and lateral profiles were measured for all available energies with the primary scattering foil removed. All beam characteristics were compared to those of the conventional electron beams. The SFF electron beams were modeled and simulated using the Monte Carlo method. CT scans of six previously treated breast patients were used for the treatment plan generation. Electron boost plans with conventional beams and the SFF beams were generated, respectively, for all the patients.

Results:
A significant reduction of the photon component was observed with the removal of the primary scattering foil for beam energies higher than 12MeV. Slight increase in beam energy was only noticed with the 18MeV and 21MeV beams. Ion chamber measurements showed higher dose per monitor unit especially at the higher energies. Flatness was greatly affected, however the difference in flatness between conventional and SFF beams was much reduced for small cone sizes and can be clinically insignificant for breast boosts. Removal of the secondary scattering foil could further reduce photon contamination but the beam flatness was also drastically deteriorated. Results from the electron boost plans showed similar target coverage with much reduced dose to the critical structures.

Conclusion:
The SFF electron beams can deliver high-quality dose distributions as conventional electron beams for boost treatments with an added advantage of further reduced dose to the lung and heart.


Funding Support, Disclosures, and Conflict of Interest: This work has been supported by a UICC American Cancer Society Beginning Investigators Fellowship funded by the American Cancer Society

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