ESTRO 2024 - Abstract Book

S5605

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

positioning based on an open mask system. Evaluation of the primary endpoint (patient comfort) has been previously reported. Here we report on the secondary endpoints of mask stability and positioning accuracy.

Material/Methods:

In this single-centre prospective randomized self-controlled trial, patients were treated sequentially with two immobilization masks and identical treatment plans, each used for 50% of the prescribed treatment. The order in which the masks were used was decided using crossover randomization. Intra-fraction analysis of the uncertainties associated with mask stability were assessed by daily pre-treatment kV imaging and once-weekly post-treatment kV imaging for both mask types. A Surface Guided Radiation Therapy (SGRT) system was used in combination with the open-face masks to report intra-fraction motion and aid patient positioning. Real-time deltas reported by the SGRT system were recorded after patient pre-positioning and again after kV imaging and the application of correctional shifts (Figure 1).

Results:

A total 30 patients with primary or secondary brain tumors were registered to the trial, with 29 completing treatment to a median radiation dose 54Gy, range 30-60Gy.

Pre-positioning accuracy with the closed mask using lasers for set-up was superior for pitch, roll and rotation (Figure 2). Longitudinal positioning was also superior with the closed masks. Lateral and vertical positioning using SGRT was