ESTRO 2024 - Abstract Book

S5623

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

ESTRO 2024

The aim of this pilot study was to determine if the translational and rotational accuracy during treatment set up was comparable between five-, and four-point immobilisation for thoracic patients. Secondly, whether there was an improvement in patient experience using the less restrictive four-point shell.

Material/Methods:

16 consecutive radically planned thoracic patients (55Gy/20#) were randomised between five-point, and four-point immobilisation. Department protocol is to image daily and treatment was delivered as standard. After treatment was complete all CBCT images were retrospectively reviewed independently by two IGRT specialist RTTs on XVI (Elekta, Stockholm, Sweden) to establish an isocentric match using an automated rigid registration algorithm. Setup errors was recorded firstly as translational deviations of the isocenter along three axes, namely left–right (LR), superior–inferior (SI), and anterior–posterior (AP), and secondly as rotational deviations along three axes, namely pitch, yaw and roll. For each patient, the systematic error in each direction was calculated as the mean of all setup errors recorded during the fractionated radiotherapy course, while the random error in each direction was the standard deviation (SD) of the patient setup errors. The populations' mean of setup errors was the average of all patients' means in each direction.