Surface-Guided Radiotherapy Feedback: Improvement and Change of Practices.

Purpose/Objective(s) Surface imaging systems are becoming a reference in radiotherapy treatments to improve patient setup. Thanks to an important database of patient positioning, a clinical retrospective evaluation of the system has been realized. For this evaluation, three relevant endpoints have been identified and analyzed: the time-saving setup, the accuracy setup, the number of additional X-Ray images performed to validate the patient setup. Materials/Methods Two groups of patients have been defined including all localizations except head & neck treatments. Patients have been all treated on the same Linac following the same positioning and imaging protocol. The first group, the reference one, includes 700 patients with a treatment positioning based on skin marks using lasers. The second group includes 250 patients with treatment positioning based on surface imaging system. In parallel, clinical data (BMI, age, localization etc.) and treatment data (immobilizing system, treatment technique etc.) have been extracted from the Hospital Information System (HIS) and Treatment Planning System (TPS) databases thanks to homemade program. Afterwards, statistical analyses have been carried out for both groups in order to correlate the clinical and technical data with the three defined endpoints. Results Different correlations have been pointed out. First results confirm that the surface imaging system gives relevant and better set-up information for different sub-groups (breast, skinny pelvis etc.). Nevertheless, for others sub-groups, no correlation nor improvements have been observed (pelvic high BMI etc.) in comparison to laser positioning. Conclusion Different changes in our patient positioning practices have been defined with the help of surface imaging system. For many patients, we improved our imaging workflow efficiency. For several sub-groups of patients, we still have to investigate the system and its best use.