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SU‐E‐T‐405: Evaluation of IMRT QA Using 3DVH, a 3D Patient Dose and Verification Analysis Software
Author(s) -
Jarry G,
Martin D,
Lemire M,
Ayles M,
Pater P
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 - 10.1118/1.3612359
Subject(s) - nuclear medicine , computer science , medicine
Purpose: 3DVH (Sun Nuclear Corporation) is a software that uses individual field QA data to obtain a three‐dimensional dose distribution in the patient. The purpose of this poster is to evaluate 3DVH as an IMRT QA tool; mainly to present our validation results, the TPS model improvements they lead to and preliminary passing rate results on IMRT plans analysed using 3DVH. Methods: The validation was performed using simulated Mapcheck (Sun Nuclear Corporation) QA results obtained from the TPS. The accuracy of 3DVH in calculating errors was verified by introducing errors in the plans and comparing these plans with the dose 3DVH predicted. IMRT plans were verified using the 3DVH software and the results were analysed by looking at DVH values. The 3DVH results were compared to Mapcheck QA results. Results: The validation shows that 3DVH can predict errors within 3%, with discrepancies tending to increase as the induced errors become greater. The retrospective analysis of IMRT plans resulted in a TPS model modification as it brought to light the occasional under dosing of the PTVs. The rounded leaf tip model was modified to decrease the field size for fields defined by the MLC only. This change to the model was validated using picket fence measurements. The IMRT plans were recalculated using the new model; as a result, the 3DVH passing rate for a 3%/3mm gamma between the expected dose and the 3DVH dose increased from 93% to 98% on average. Further analysis of IMRT plans has shown that 3DVH is more sensitive to dose discrepancies than individual field QA. Conclusions: 3DVH is a useful tool for IMRT QA which supplements the planar dose information collected using 2D arrays or film. The analysis of IMRT plans has shown that 3DVH can detect dose differences that are not detected by individual field analysis alone.