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Dosimetric Comparison Between TMR Based Algorithm and Collapsed Cone Algorithm for Radiodynamic Therapy Treatment Planning Using 45MV Beams

A Eldib1, J Liu1*, J Panetta1, M Sherif2, C Ma1, (1) Fox Chase Cancer Center, Philadelphia, PA, USA (2) Kuwait Cancer Control Center, Hawally 32097, ,KW, Kuwait

Presentations

PO-GePV-T-302 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: Radio-dynamic therapy (RDT) is a novel treatment that combines high-energy photon beams and photo/radio-sensitizers to kill cancer cells. The hypothesis is that higher energy photons will produce more Cherenkov light, which will in turn activate more sensitizers in the body. Thus, 45 MV photons from a RaceTrack microtron have been investigated in this study to evaluate the dosimetry accuracy of different algorithms for patient dose calculation. Material and

Methods: The 45MV beam was modeled using Prowess (Prowess, Concord, CA) treatment planning system (TPS). The system comprises a simple TMR based algorithm and a collapsed cone dose calculation algorithm. Treatment plans for RDT patients previously treated in our department were selected including different body sites, e.g., thorax, abdomen, and pelvic lesions. The dose differences between the two algorithms were evaluated based on dose volume histograms for the planning target volume (PTV) as well as for organs at risk (OAR).

Results: TMR based algorithm could under predict the PTV dose coverage. It was shown in a thorax case that by using the same monitor units, the volume receiving the prescription dose (V6Gy) could be as low as 87% with the TMR based calculation as compared to 99% with the collapsed cone algorithm. On the other hand, V6Gy for abdominal cases was lower by less than 2%. TMR based calculations under predicted the mean dose to the normal lung tissues for the thorax cases. The collapsed cone algorithm also resulted better gamma passing rates than TMR-based dose calculation when the measured dose is analyzed against the planned dose distribution.

Conclusion: The collapsed cone algorithm is preferred for dose calculation in RDT treatment planning using high-energy photon beams.

Keywords

Treatment Planning, Dosimetry

Taxonomy

TH- External Beam- Photons: treatment planning/virtual clinical studies

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