PMID- 31998821 OWN - NLM STAT- PubMed-not-MEDLINE LR - 20220412 IS - 2331-5180 (Electronic) IS - 2331-5180 (Linking) VI - 6 IP - 2 DP - 2019 Fall TI - Characterization of a MLIC Detector for QA in Scanned Proton and Carbon Ion Beams. PG - 50-59 LID - 10.14338/IJPT-19-00064.1 [doi] AB - PURPOSE: Beam energy validation is a fundamental aspect of the routine quality assurance (QA) protocol of a particle therapy facility. A multilayer ionization chamber (MLIC) detector provides the optimal tradeoff between achieving accuracy in particle range determination and saving operational time in measurements and analysis procedures. We propose the characterization of a commercial MLIC as a suitable QA tool for a clinical environment with proton and carbon-ion scanning beams. MATERIALS AND METHODS: Commercial MLIC Giraffe (IBA Dosimetry, Schwarzenbruck, Germany) was primarily evaluated in terms of short-term and long-term stability, linearity with dose, and dose-rate independence. Accuracy was tested by analyzing range of integrated depth-dose curves for a set of representative energies against reference acquisitions in water for proton and carbon ion beams; in addition, 2 modulated proton spread-out Bragg peaks were also measured. Possible methods to increase the native spatial resolution of the detector were also investigated. RESULTS: Measurements showed a high repeatability: mean relative standard deviation was within 0.5% for all channels and both particle types. The long-term stability of the gain calibration showed discrepancies less than 1% at different times. The detector response was linear with dose (R (2) > 0.99) and independent on the dose rate. Measurements of integrated depth-dose curve ranges revealed a mean deviation from reference measurements in water of 0.1 +/- 0.3 mm for protons with a maximum difference of 0.4 mm and 0.2 +/- 0.6 mm with maximum difference of 0.85 mm for carbon ion beams. For the 2 modulated proton spread-out Bragg peaks, measured differences in distal dose falloff were