Program Information
APBI Brachytherapy Treatment Planning: The Impact of Heterogeneous Dose Calculations
S Loupot*, T Han , M Salehpour , K Gifford , M.D. Anderson Cancer Center, Houston, TX
Presentations
SU-F-19A-1 Sunday 4:00PM - 6:00PM Room: 19APurpose:To quantify the difference in dose to PTV_EVAL and OARs (skin and rib) as calculated by (TG43) and heterogeneous calculations (CCC).
Methods: 25 patient plans (5 Contura and 20 SAVI) were selected for analysis. Clinical dose distributions were computed with a commercially available treatment planning algorithm (TG43-D_(w,w)) and then re-computed with a pre-clinical collapsed cone convolution algorithm (CCC-D_(m,m)). PTV_EVAL coverage (V90%, V95%), and rib and skin maximum dose were compared via percent difference. Differences in dose to normal tissue (V150cc, V200cc of PTV_EVAL) were also compared. Changes in coverage and maximum dose to organs at risk are reported in percent change, (100*(TG43 – CCC) / TG43)), and changes in maximum dose to normal tissue are absolute change in cc (TG43 – CCC).
Results: Mean differences in V90, V95, V150, and V200 for the SAVI cases were -0.2%, -0.4%, -0.03cc, and -0.14cc, respectively, with maximum differences of -0.78%, -1.7%, 1.28cc, and 1.01cc, respectively. Mean differences in the 0.1cc dose to the rib and skin were -1.4% and -0.22%, respectively, with maximum differences of -4.5% and 16%, respectively.
Mean differences in V90, V95, V150, and V200 for the Contura cases were -1.2%, -2.1%, -1.8cc, and -0.59cc, respectively, with maximum differences of -2.0%, -3.16%, -2.9cc, and -0.76cc, respectively. Mean differences in the 0.1cc dose to the rib and skin were -2.6% and -3.9%, respectively, with maximum differences of -3.2% and -5.7%, respectively.
Conclusion: The effects of translating clinical knowledge based on D_(w,w) to plans reported in D_(m,m) are minimal (2% or less) on average, but vary based on the type and placement of the device, source, and heterogeneity information.
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