ESTRO 2021 Abstract Book

S1656

ESTRO 2021

Comfort was scored by the volunteers/patients with numbers from 1 (no comfort) to 5 (very comfortable).

Results

Reproducibility The blue knee cushion scored best in the patients while for the volunteers the immobilization mask was best. Given the unavailability of the immobilization masks in clinical routine, this has not (yet) been tested in patients. The reproducibility of the blue knee cushion and the vacuum mattress is comparable but not optimal in both groups. Time registration Both patient and volunteer positioning (T1) were fastest using the blue knee cushion. It took on average twice as long to get the patients off the treatment table compared to the volunteers when using the vacuum mattress. This is probably due to the age difference. When we include the scores of the red knee cushion, it has the best scores at any time. Comfort The vacuum mattress was experienced the least comfortable for both groups. The volunteers reported pain in the shoulders using all devices, including the immobilization mask where the arms are placed high on the chest instead of above the head. Conclusion We have found that the immobilization mask has advantages in reproducibility and comfort. We think to extend the use of this device even further to all treatments where the use of a frog-leg position is recommended. Surface guided radiotherapy (SGRT) has promise of potential improving patient’s positioning and dose delivery accuracy. The current study aimed to compare the patient positioning reproducibility for SGRT and the standard laser-based approach. Materials and Methods 28 breast and pelvic cancer patients were enrolled in the study. 13 patients were treated with standard laser-based positioning RT (LBPRT) using thermoplastic masks for breast cancer and skin markers for pelvic cancer RT. 15 patients received SGRT, thermoplastic masks or skin markers were not used. Positioning accuracy was quantified with cone-beam CT (CBCT) for SGRT and LBPRT patients in general cohort and the groups regarding the region of irradiation. 147 CBCTs were performed, 5 mm isocenter displacement was considered to be acceptable. Mann-Whitney test was conducted on comparisons (p < 0.05). Results All CBCTs showed minor deviation from the reference point (table 1). Statistical analysis revealed no significant differences between SGRT and LBPRT for this parameter (р> 0,05). Table 1. – Median of reference position deviation for compered techniques PO-1944 experience of SGRT implementation D. Mychko 1 , E. Zvereva 1 , S. Siamkousky 1 1 Minsk City Clinical Oncologic Dispensary, Radiotherapy Department, Minsk, Belarus Purpose or Objective