ESTRO 2024 - Abstract Book

S5535

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

ESTRO 2024

minimal movement, defined as <3mm for head-and-neck and brain (HN) treatments, and <5mm for non-HN treatments. These minimal movements thresholds are within institutional PTV margins for these body sites.

Results:

A total of 65 patients with evaluable data were enrolled in our study. Median age was 11 and ranged from 2 to 18 years old. Treatment was to the brain (47%), chest (13%), craniospinal axis, (9%), pelvis (8%), abdomen (6%), head and-neck (6%) or other (11%). Depending on treatment site patients were immobilized with short thermoplastic mask (49%), full thermoplastic mask (19%), chestboard (12%), vacuum bag (11%), or mattress only (11%). From the 65 patients, we acquired 302 post-treatment CBCT scans. Minimal movement was observed in 99.4% of HN treatments and 97.2% of non-HN treatments. Figure 1 shows the intrafraction movement from all study evaluations. Very few treatments had observed movement above 3 mm. The study hypothesis of >90% of evaluations having minimal movement was met. In a multivariable linear mixed effects model, age, immobilization method and boost phase of RT were significantly associated with intrafraction movement. We found that children age >11 years moved less at first evaluation, but tended to move more over time, as compared to children who were younger. With regards to immobilization, children with full thermoplastic masks tended to move less over time, as compared to children with a short thermoplastic mask. In contrast, patients immobilized with vacuum bag tended to move more as treatment course progressed, as compared to a short thermoplastic mask.

Figure 1.

Conclusion:

This study is the first known prospective trial evaluating intrafraction motion in paediatric patients receiving awake RT and the effectiveness of audiovisual distraction. We have found that children receiving RT awake with audiovisual distraction exhibit minimal intrafraction movement. The overall magnitude of this motion was small and <3mm in almost all treatments. This study validates our methods of anaesthesia avoidance using audiovisual distraction, and allow us to conclude: no, the children are not moving during awake RT!