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SU‐E‐T‐736: Dosimetric Evaluation with Heterogeneity in Eclipse Treatment Planning Dose Calculation Algorithms
Author(s) -
Rana S,
Cheng C,
Hibbitts K,
Ahmad S
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3612698
Subject(s) - imaging phantom , radiation treatment planning , nuclear medicine , materials science , beam (structure) , dosimetry , eclipse , algorithm , computer science , physics , optics , medicine , radiation therapy , radiology , astronomy
Purpose: Dose calculation accuracy utilizing anisotropic analytical algorithm (AAA) and pencil beam convolution (PBC) with multiple inhomogeneous phantoms was evaluated with measurements. Methods: A five layer virtual phantom was created in the Eclipse planning system. Each 5 cm layer was assigned in terms of water, air, water, bone, and water materials. Plans with a 6MV beam in different field sizes were calculated in AAA_8615 (with heterogeneity correction) and PBC_8615 (with and without heterogeneity correction). Combinations of solid water, PVC, and Styrofoam were then manufactured to acquire doses with parallel plate chamber and EDR2 films. Next, a seven field IMRT plan in PBC without heterogeneity was created within a Rando phantom. A cylindrical target volume was defined and 95% target was covered by prescription doses. Plans were then regenerated by recalculating this optimized base plan with keeping identical beam parameters but switching algorithms. The base plan was delivered to the phantom with TLDs and films. Measurements were compared with all calculations at same locations. Results: AAA shows a better dose prediction in all materials from measurements (Fig. 1–Fig.4). Discrepancies in air and bone regions due to lacks of lateral scatters and beam hardening were observed. In IMRT, both PBC with heterogeneity and AAA mean calculated target doses were <1% compared to TLD measurements; and PBC without heterogeneity values were lower by 11%. AAA produced better matches in profiles (Fig.5) as well. Conclusions: The findings suggest that AAA is more appropriate in dose predictions especially when lung and bone are involved.