SU-E-T-297: Proton-Therapy System for Treatment of Macular Degeneration and Ocular Malignancies

Medical Physics
R L SlopsemaZ Li

Abstract

To commission a proton-therapy system for the treatment of uveal melanoma and age-related macular degeneration. Proton therapy system is the proto-type of a commercial product developed by Ion Beam Applications. Proton beam is brought into the treatment room at 105 MeV through a fixed beam line. A single-scattering system with absorber/scattering foils spreads the beam into a Gaussian profile. A library of 10 range-modulator wheels and 16 range-modulator blocks generate spread-out Bragg peaks of various range and modulation width. Source-to-axis distance of the system is 169 cm. Two orthogonal digital x-ray panels are used for alignment. EyePlan software is used both for both treatment planning and in-room alignment. Range can be varied continuously between 0.5 and 3.4 g/cm(2) . Range accuracy is measured to be better than 0.05 g/cm(2) . Modulation width can be varied in steps of =0.3 g/cm(2) with an accuracy of 0.05 g/cm(2) or 2%. Maximum aperture diameter is 2.5 cm and maximum dose rate >32 Gy/min. Strong dependence of output on range (7%/mm) and dose rate (0.2%/(Gy/min)) is found. Distal and lateral fall-off (80%-20%) are =0.23 and =0.18 g/cm(2) and do not depend much on range or depth. When reducing the aperture diameter to...Continue Reading

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