In-Vivo Detection of Strut Deformation in Partial Breast Irradiation
M Walls1*, C Ramsey1,2, I Pfeiffer2, (1) University of Tennessee, Knoxville, TN, (2) Thompson Cancer Survival Center, Knoxville, TN
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PO-GePV-T-21 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: The purpose of this study was to computationally evaluate the feasibility of using in-vivo detectors, such as plastic scintillation detectors, to perform in-vivo dosimetry inside a strut adjusted volume implant (SAVI) while a high dose rate (HDR) source was actively treating in an adjacent channel. This is particularly important for SAVI, because strut translations greater than 2-mm have been shown to significantly increase organ at risk dose.
Methods: Ten patients were randomly selected that were previously planned in Oncentra and treated with SAVI. A simulated detector was positioned lengthwise in the plane perpendicular to the central channel at the point of maximum strut diameter. The radiation dose was calculated to the simulated detector for each individual dwell position and time in the original plan. Strut splay was then simulated by adjusting the position of the reconstructed catheters. The catheter was moved in 2-mm increments and the dose to the detector position was revaluated.
Results: Strut deflection and splay was modelled for seven 6+1 applicators, two 8+1 applicators, and one 10+1applicator. For each case, the catheter reconstruction was adjusted to simulate an outward deflection of a single strut. The dose was re-calculated to the detector for all dwell positions in all struts. When the source, or the detector were located in the strut with the deflection, then the dose differed between the original and modified plans. The average dose difference for a 2-mm strut deflection was a 9% decrease in dose, while the average dose difference for a 2-mm strut deflection was a 17% decrease in dose.
Conclusion: There can be a significant change in dose due to deformation of SAVI struts. This correlates to changes in the magnitude and shape of the dose distribution that could be detected using dosimeters in adjacent struts.
Keywords
Taxonomy
TH- Brachytherapy: Development (new technology and techniques)
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