ESTRO 2024 - Abstract Book

S4905

Physics - Quality assurance and auditing

ESTRO 2024

In spite of the use of detailed RTQA guidelines, 25% of initial SBRT treatment plan submissions within the HALT study required correction owing to outlining errors. After corrections, centres showed good compliance, with a sharp decrease in the number of further treatment modifications needed. Particular care must be taken when delineating structures close to the PTV, as these errors may have greater dosimetric consequences, with the potential of increased toxicity or inappropriate compromise of PTV coverage. The QA program was effective in highlighting potential variations from protocol. Prospective case reviews should be maintained for future studies in the SBRT setting.

Keywords: individual case reviews, SBRT, RTQA, compliance

2521

Digital Poster

Commissioning and Validation of AlignRT InBore™ system on the Ethos™ Linear accelerator

Ananda Ramchandra Jadhav, Prasad Raj Dandekar, Ajinkya Gupte, Sachin Rasal, Omkar Awate, Manish Bhosale, Mayank Dhoundiyal

Sir H N Reliance Foundation Hospital and Research Centre, Radiation Oncology, Mumbai, India

Purpose/Objective:

To document the commissioning process and evaluate the performance of AlignRT InBore™, Surface Guided Radiation Therapy (SGRT) platform designed specifically for ring gantry linear accelerator, on Ethos™. This system integrates ceiling mounted cameras for patient positioning and bore-mounted cameras for intra-fraction tracking. The current study also evaluates the accuracy of SGRT system for patient positioning and dosimetric impact of SGRT system on adaptive radiotherapy patients for pelvic malignancies.

Material/Methods:

Stability, accuracy, and overall performance of AlignRT InBore™ and the SGRT Ceiling Cameras were assessed in accordance with VisionRT's standard installation guidelines. Commissioning involved Thermal Stability Test, Relative Shift Accuracy Test in vertical, longitudinal, and lateral directions, Delta Stability and Pod Occlusion Test, ambient lighting assessment during patient alignment and treatment. Calibration, system setup, validation analysis, real-time delta performance of the Ceiling Camera and InBore Ring Camera, as well as their co-calibration, were performed, as per pre-specified requirements by VisionRT. The MV iso center Cube Phantom, Daily Calibration Plate, Mannequin, and Leg Phantom were used for these evaluations. Image quality was assessed using the MV iso-center Cube Phantom and Catphan R 504 Phantom, as per MV imaging and CBCT protocols.

Daily adapted plans of ten patients who underwent adaptive radiotherapy on Ethos were analysed on Eclipse TPS for dosimetric impact. These patients were set up and monitored during treatment with SGRT system. Patient-specific