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Validation of a Second MU Calculation Program for Proton Treatment

a dimofte*, J Finlay, S Both, T Zhu, Univ Pennsylvania, PHILADELPHIA, PA

SU-E-T-48 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall

Purpose: The purpose of this study was to validate the monitor unit (MU) calculation procedure for using a factor-based MU calculation program (PennMU).

Methods: Double scattering beam (DS) and pencil beam scanning for single field uniform dose (SFUD) monitor units were calculated and compared to those generated by the treatment planning system using PennMU. The algorithm is based on a well-established formula for proton output calculation. All beam data are generated based on the measurement. Pristine percentage depth doses (PDD) for several ranges and off-axis ratio (OAR) at several depths of the pencil proton beam are used. The program can import DICOM RT plans from the Varian Eclipse treatment planning system (TPS).

Results: DS and SFUD plans for various clinical sites were evaluated for patients treated for prostate, pancreas, lung, esophagus, with ranges varying from 10 to 27cm and modulations varying from 5 to 15cm (WEPL). PennMU was used to calculate MU for each field and the results were compared to MU given by the TPS. For prostate cases, were the range is larger (up to 25cm), the agreement between PennMU and TPS are up to 2%. Larger errors (of up to 5%) were seen for ranges smaller than 23cm.

Conclusions: Differences in the calculated and measured values of MU are within 5% (with variations of 2% for ranges up to 23cm). This algorithm is ideally suitable for calculating patient-specific MU for double scattering and pencil-beam based treatment planning system for protons.

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