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SU‐E‐T‐453: Feasibility of IMRT System Evaluations Using Pre‐Made IMRT Leaf Patterns
Author(s) -
Gordon J,
Young S,
Dukes B,
Hamilton R
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 - 10.1118/1.3612407
Subject(s) - imaging phantom , radiation treatment planning , dosimetry , ionization chamber , superposition principle , pencil (optics) , confidence interval , nuclear medicine , beam (structure) , optics , materials science , computer science , mathematics , physics , radiation therapy , statistics , medicine , ion , radiology , mathematical analysis , quantum mechanics , ionization
Purpose: To assess the feasibility of utilizing pre‐made IMRT leaf patterns in IMRT system evaluation. Methods and Materials: A TG1 19 evaluation set consisting of five IMRT test cases were optimized using a pencil‐beam algorithm and delivered on a 30 cm × 30 cm × 15 cm solid water phantom. Per‐field measurements were collected using a diode array, and composite measurements were collected using film and ion chamber. Measurements were compared to calculation to determine confidence limit values per TG1 19 methodology. The phantom image set, associated contours, and leaf patterns were then transferred to a separate treatment planning system utilizing different treatment planning software previously commissioned for the same LINAC. Dose calculations utilizing a convolution‐superposition algorithm were performed on this planning system utilizing the pre‐made IMRT leaf patterns and image set. These calculations were compared to previously collected measurements, and TG1 19 confidence limits were determined. Results: The TG1 19 evaluation utilizing the pencil‐beam treatment planning system resulted in confidence limits of 1.55%, 8.06%, and 3.13% for diode array, film, and ion chamber comparisons, respectively. The TG1 19 evaluation utilizing the same leaf patterns within the convolution‐superposition treatment planning system resulted in confidence limits of 10.5%, 14.9%, and 5.46% for diode array, film, and ion chamber comparisons, respectively. The TG1 19 confidence limit values for the two planning systems differed by 8.95%, 6.84%, and 2.33%.Conclusion: This study has demonstrated the feasibility in utilizing pre‐made leaf patterns to evaluate the dose model for an IMRT system. In this case, the pencil‐beam TPS calculations were closer to measured values, as quantified by the TG119 assessment.