Introduction 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. Purpose This study aimed at characterizing the Lynx PT system (IBA Dosimetry) and assessing its suitability for QA tests, for proton and carbon ion beams. Materials and methods 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. Results 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. Conclusion 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.
Range verification with in-beam PET techniques is a powerful tool for monitoring the correctness of dose delivery in particle therapy. Among the major limitations of in-beam PET systems are the ...limited detectors size due to the constrained space in which they can be placed to allow the irradiation, and the necessity of a high read-out modularization, due to high activity rates during the irradiation. In this work we present the data acquired at the CNAO (Centro Nazionale di Adroterapia Oncologica) treatment center in Pavia, Italy, with the new DoPET system, specifically designed to operate in in-beam conditions. The new prototype consists of two planar 15cm x 15cm LYSO-based detectors, read out by 9 PMT detector modules each. In particular, we test the capability of our system to determine particle range in various irradiation conditions. Several plastic phantoms were irradiated at the CNAO treatment centre with protons and carbon ions of various energies. The used dose in treatment plans is 2 Gy and the monitoring feedback is produced in a few minutes after the end of the treatment.
PET imaging is a non-invasive technique for particle range verification in proton therapy. It is based on measuring the beta super(+) annihilations caused by nuclear interactions of the protons in ...the patient. In this work we present measurements for proton range verification in phantoms, performed at the CNAO particle therapy treatment center in Pavia, Italy, with our 10 x 10 cm super(2) planar PET prototype DoPET. PMMA phantoms were irradiated with mono-energetic proton beams and clinical treatment plans, and PET data were acquired during and shortly after proton irradiation. We created 1-D profiles of the beta super(+) activity along the proton beam-axis, and evaluated the difference between the proximal rise and the distal fall-off position of the activity distribution. A good agreement with FLUKA Monte Carlo predictions was obtained. We also assessed the system response when the PMMA phantom contained an air cavity. The system was able to detect these cavities quickly after irradiation.
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