Experimental study on positioning uncertainty of patients treated with stereotactic encephalic radiotherapy using surgical mask in Covid-19 era: analysis of dosimetric and set-up parameters

Abstract

Aim
To evaluate the positioning uncertainty in patients treated with encephalic stereotactic technique using the combination of a surgical mask with thermoplastic mask for immobilization of radiotherapy treatment.
Materials and methods
Retrospective “Matched Pair” review and evaluation of a sample of 19 patients, divided into two groups, treated between November 2018 and March 2022 with a number of active lesions less than or equal to 2 on magnetic resonance imaging (MRI): the first group includes patients treated in the pre-Covid-19 era and immobilized without a surgical mask, while the second treated in the Covid-19 era with a surgical mask.
Results
The study showed that there were no statistically significant differences between the two study groups by obtaining as positioning error in Verticality (Y-axis) values of 0.5 mm without surgical mask compared with -0.4 mm with surgical mask;
in Longitudinal (Z-axis) values of -0.3 mm compared with 0.2 mm with surgical mask and finally in Laterality (X-axis) values of -0.6 mm without surgical mask compared with 0.1 mm with surgical mask. Subsequently, dose fluence analysis also confirmed the set-up reliability datum with the online in vivo dosimetry reproducibility datum.
Discussion
The association of the surgical mask with the thermoplastic mask, which was necessary in the Covid-19 era, proved to be essential in order to ensure the quality of treatments delivered without compromising the safety of operators and patients within the Operating Unit.