Evaluation of mechanical and geometric accuracy of two different image guidance systems in radiotherapy

Abstract Aim To assess the mechanical and the geometric accuracy of two different clinically used image guidance systems in radiotherapy for a period of 6 months. Background With the image guidance procedures being routine in the clinical radiotherapy department, the quality assurance tests for these systems become essential. The mechanical and geometric accuracy of these systems are crucial since it directly affects patient treatment set-up and delivery. Materials and methods We have assessed the mechanical and the geometric accuracy of two different image guidance systems (MV and kV based), being used clinically for a period of 6 months. The quality assurance tests such as imager positioning/repositioning, imaging and treatment beam isocentre coincidence, imager mechanical alignment, image scaling, geometric accuracy of cone beam computed tomography system, automatic image registration and offset calculation accuracy were assessed in this period. Results It was found that both systems were mechanically and geometrically accurate within ±2 mm in this period. Conclusion The quality assurance tests for MV based image guidance system were simple compared to kV based systems. We recommend performing periodic quality assurance tests to verify the integrity of both image guidance systems.