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Poster — Thurs Eve‐39: Full 3D dose calculation for total body irradiation: A comparison study between treatment planning systems in homogeneous and heterogeneous conditions
Author(s) -
Lavallée MC,
Gingras L,
Aubin S,
Côté C,
Larochelle M,
Chrétien M,
Beaulieu L
Publication year - 2008
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 - 10.1118/1.2965958
Subject(s) - homogeneous , nuclear medicine , radiation treatment planning , total body irradiation , medicine , radiation therapy , physics , surgery , chemotherapy , cyclophosphamide , thermodynamics
Purpose: To perform full 3D heterogeneous dose calculations for total body irradiation (TBI) cases and compare different treatment planning softwares (TPS). Method: A retrospective study was performed on 7 patients. Dose distributions obtained with Pinnacle 3 v.7.9u (Philips Medical Systems) were compared with the ones calculated using our actual TBI planning system Theraplan Plus (TPP) by MDS Nordion/Nucletron . Two different Pinnacle 3 models were studied: standard beam commissioning ( std_Pinnacle 3 ) and TBI commissioning ( TBI_Pinnacle 3 ). For the later case, commissioning was adapted for the special TBI conditions (extended SSD of 190cm, large field, acrylic beam spoiler, and out of field dose (OFD)). Results: Significant differences are found between the TPP , std_Pinnacle 3 and TBI_Pinnacle 3 dose distributions. For the relative mid‐line doses, differences up to 12% were observed. Systematic overestimations of 5% were found in patients extremities between TPP and TBI_Pinnacle 3 . Average dose underestimation of 3% was observed between std_Pinnacle 3 and TBI_Pinnacle 3 . Differences in patient extremities are attributed to the OFD contribution which is not correctly computed in TPP and std_Pinnacle 3 . Dose comparison outside the patient's mid‐line showed greater differences (up to 20%) between models. Accurate 3D heterogeneous dose calculations with TBI_Pinnacle 3 model show major differences (homogeneous versus heterogeneous) in high and low density regions. Dose overestimation of 5% was observed in bony regions and dose underestimation of 5% to 10% was observed in lung regions. Conclusion: Those results are of major interest since they show a strong dependence of the dose calculation outcome on both TPS and commissioning used, potentially leading to significant dose misevaluation.

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