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Beam Characteristics of a Directional X-Ray Source for Intraoperative Radiotherapy

M Kim*, W Harris, D Bollinger, S Anamalayil, N Taunk, B Teo, University of Pennsylvania, Philadelphia, PA


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Physical characteristics were investigated for a novel intraoperative radiotherapy (IORT) device with a directional x-ray source that operates between 50 kVp and 100 kVp. Directional capability was introduced to enable more conformal dose for treatment of irregularly shaped cavities and facilitate dose sculpting for normal tissue sparing.
Methods/Materials: Each of the 6 directional sectors of the IORT system has 3 target locations that can be turned on independently to create a 3D dose distribution. Gafchromic film measurements were made in water and in solid phantoms to characterize dose uniformity and the direction dependent depth-dose distributions. Film was placed at the tip of the electron gun, perpendicular to the beam direction as well as parallel to the electron gun to obtain the 3D depth dose characteristics of the beam. Dose profiles were taken along the transverse and longitudinal plane, and along a 45-degree angle in the forward direction of the beam.
Results: The dose profiles and depth dose curves taken shows that the system is capable of delivering directional radiation therapy by choosing one or more of the 18 target positions available for dose sculpting. The dose sculpting capability is an advantage of the system to deliver conformal dose to irregularly shaped targets. The dose uniformity for different sectors had a slight dependence on the local magnetic field. This effect is larger for the low energy and at the inner target location. In-plane homogeneity between sectors was found to be heavily dependent on the source tuning and target position.
Conclusion: Beam characteristics were generated for a novel IORT device. The device design allows for levels of dose shaping previously unachievable with IORT.

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TH- External Beam- Photons: intraoperative

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