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SU‐GG‐T‐545: Dosimetric Verification of RapidArc Treatment Delivery Using the Delta4 Phantom
Author(s) -
Korreman S,
Medin J,
Wiberg I,
Bocanek J,
Archambault Y,
Cozzi 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 - 10.1118/1.2962294
Subject(s) - imaging phantom , nuclear medicine , reproducibility , dosimetry , medicine , image guided radiation therapy , mathematics , medical imaging , radiology , statistics
Purpose: Recently, Varian Medical Systems have introduced a new treatment technique, in which dose is delivered over one gantry rotation with variable MLC positions, dose rate and gantry speed, RapidArc. A preclinical RapidArc installation was carried out on a Varian Clinac at our institution. We report dosimetric verification of reproducibility and consistency of RapidArc delivery using the Delta4 phantom (Scandidos, SE). Method and materials: 9 treatment plans generated in the Eclipse preclinical version of the RapidArc optimizer (H&N, prostate and lung) were delivered using a Clinac equipped with RadidArc delivery capability. The delivered dose was measured using the Scandidos Delta4 phantom. The measured dose distributions were compared with doses calculated in Eclipse. All plans were delivered three times consecutively, and the first run was used as reference for constancy checks. The temporal resolution of the delivery was analysed by investigating the arc segments between control points separately (177 control points per rotation). Gamma analysis (3%/3mmDTA) was used to quantify correspondence between dose distributions. Results: Overall, good agreement was observed between measured and calculated doses, generally with gamma values <1 in >95% of measured points. Comparison of the accumulated doses for two consecutive runs of a plan showed gamma values <1 in all measured points. The segment‐by‐segment analysis showed discrepancies between two consecutive runs, with >90% gamma values <1 in around 50–60% of the segments (gamma dose criterium 3%; <1–2 mGy for single segments). Segments with large dose deviations were typically counter‐balanced by following segments with large deviations of the opposite sign. The segment discrepancies cancelled out in the accumulated dose. Conclusion: The delivery of RapidArc beam delivery corresponded well with calculated dose distributions for different cases. The delivery was reproducible, and was carried out with high stability of the accelerator performance. Research sponsored by Varian Medical Systems, Inc.