Dosimetric characterization of a commercial 2-D scintillation detector for quality assurance tests in scanned proton and carbon ion beams.

Pencil beam scanning technique used at CNAO requires beam characteristics to be carefully and periodically checked to guarantee patient safety. Radiochromic films are used within daily QA checks. This study aimed at characterizing the Lynx PT system (IBA Dosimetry) and assessing its suitability for QA tests, for proton and carbon ion beams. The Lynx PT is a 2D high-resolution dosimetry system consisting of a scintillating screen coupled with a CCD camera, in a compact light-tight box. A dedicated software is used for image acquisition, raw data correction and fast data analysis. Lynx was characterized in terms of short-term stability, image geometrical distortion, uniformity, signal proportionality, response dependence on IRIS and on particle intensity, particle energy and type. Irradiations were performed at the Centro Nazionale di Adroterapia Oncologica (CNAO) for both protons and carbon ions. Measurements with Lynx were compared to those made with EBT3 reference films. The detector response dependence on radiation LET was also investigated. Lynx basic characterization results have shown a proportional behavior with delivered number of particles. Strong dependence of the acquired signal on beam energy and particle type was found. No significant differences in the investigated beam parameters measured with Lynx and EBT3 film were observed. The detector also showed good performances in term of image uniformity and geometrical distortion. The Lynx PT system appears as a promising tool for measurements for both single pencil beam and scanned beam, enabling fast QA and beam optics optimization checks. [ABSTRACT FROM AUTHOR]