Efficacy and clinical use of novel high-resolution EPID-based 2D and 3D automated patient-specific quality assurance for SRS and SBRT patients

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Stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments should be delivered with caution because any delivery error can have a severe radiobiological impact on the patient due to the high dose per fraction used in such modalities. Therefore, a very high accuracy including a quality assurance program accompanying the entire treatment process is required. This study assessed the efficacy and clinical use of novel high-resolution 2-dimensional and 3-dimensional electronic portal imaging devices, an automated patient-specific quality assurance (PSQA) for SRS and SBRT patients. The dosimetric performance of these devices was evaluated by comparison with other detectors. Deliberate errors (errors of multi leave collimators (MLCs), gantry and collimator angle, and monitor unit (MU) changes) were introduced to assess the sensitivity of the devices. Twenty volumetric modulated arc therapy (VMAT) plans from various tumour sites, constrained to field sizes below 7.7 cm × 7.7 cm, were analyzed. Point dose measurements showed mean dose differences of 0.1% ± 1.5% for ionization chambers and 0.94% ± 1.8% for EPID compared to treatment planning system (TPS) calculations. With 2%/2 mm, average Gamma Passing Rates (GPRs) were 98.6% (film), 99.0% (SRS MapCHECK®), 98.7% (PDIP), 99.5% (PerFRACTION™,2D), 99.8% (PerFRACTION™,3D), and 93.2% for ArcCHECK®. At stringent 2%/1 mm criteria, high-resolution systems maintained > 94% pass rates while ArcCHECK® dropped to 73.5%. EPID showed comparable GPRs to films and SRS MapCHECK®. EPID detected most errors except small MLC shifts and gantry angle errors. It is concluded that EPID dosimetry can perform SRS and SBRT PSQA without additional devices. Thus, it offers a cost-effective, high-resolution alternative comparable to dedicated devices, enhancing clinical efficiency, without compromising accuracy.

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