Film-based delivery quality assurance for robotic radiosurgery: Commissioning and validation

Oliver Blanck*, Laura Masi, Marie Christin Damme, Guido Hildebrandt, Jürgen Dunst, Frank Andre Siebert, Daniela Poppinga, Björn Poppe

*Korrespondierende/r Autor/-in für diese Arbeit
20 Zitate (Scopus)

Abstract

Purpose: Robotic radiosurgery demands comprehensive delivery quality assurance (DQA), but guidelines for commissioning of the DQA method is missing. We investigated the stability and sensitivity of our film-based DQA method with various test scenarios and routine patient plans. We also investigated the applicability of tight distance-to-agreement (DTA) Gamma-Index criteria. Methods and material: We used radiochromic films with multichannel film dosimetry and re-calibration and our analysis was performed in four steps: 1) Film-to-plan registration, 2) Standard Gamma-Index criteria evaluation (local-pixel-dose-difference ≤2%, distance-to-agreement ≤2 mm, pass-rate ≥90%), 3) Dose distribution shift until maximum pass-rate (Maxγ) was found (shift acceptance <1 mm), and 4) Final evaluation with tight DTA criteria (≤1 mm). Test scenarios consisted of purposefully introduced phantom misalignments, dose miscalibrations, and undelivered MU. Initial method evaluation was done on 30 clinical plans. Results: Our method showed similar sensitivity compared to the standard End-2-End-Test and incorporated an estimate of global system offsets in the analysis. The simulated errors (phantom shifts, global robot misalignment, undelivered MU) were detected by our method while standard Gamma-Index criteria often did not reveal these deviations. Dose miscalibration was not detected by film alone, hence simultaneous ion-chamber measurement for film calibration is strongly recommended. 83% of the clinical patient plans were within our tight DTA tolerances. Conclusion: Our presented methods provide additional measurements and quality references for film-based DQA enabling more sensitive error detection. We provided various test scenarios for commissioning of robotic radiosurgery DQA and demonstrated the necessity to use tight DTA criteria.

OriginalspracheEnglisch
ZeitschriftPhysica Medica
Jahrgang31
Ausgabenummer5
Seiten (von - bis)476-483
Seitenumfang8
ISSN1120-1797
DOIs
PublikationsstatusVeröffentlicht - 01.07.2015

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