A comparison between four immobilization systems for pelvic radiation therapy using CBCT and paired kilovoltage portals based image-guided radiotherapy.

Introduction: We commonly use 6- and 4-clamped thermoplastic molds (TMs) for rigid immobilization during pelvic radiotherapy (RT), sometimes a vacuum cushion (VC) is also used as leg support with TM. Our objective was to report the setup margins (SMs) associated with the different systems, to analyze whether any of these systems is superior, and to analyze whether any of them showed better reproducibility in any particular direction.

Materials And Methods: Retrospective analysis was done by dividing the patients into four groups: 6-clamp with VC (6CVC), 6-clamp without VC (6CNC), 4-clamp with VC (4CVC), and 4-clamp without VC (4CNC).