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Purpose or Objective Intracranial stereotactic radiosurgery (SRS) requires high precision for setup and during treatment. On Brainlab Novalis system, noninvasive repositioning with dedicated proprietary thermoplastic mask is as accurate as with the invasive ring. Macromedics developed a new full head mask dedicated to SRS, fully compatible with the Brainlab couch and localization system, named the Double Shell Positioning System (DSPS) with documented submillimetric and subdegree intrafraction accuracy. The aim is to prospectively compare both fixation systems in a randomized trial for setup and intrafraction accuracy, as well as patient reported comfort. Material and Methods Study was approved by the Ethics Committee of CHU‐UCLNamur. All patients approved written informed consent. Sixty patients with various pathologies (metastases, vestibular schwannoma, meningioma or pituitary adenoma) had to be recruited. Randomization between Brainlab and DSPS masks was stratified according to disease and fractionation (one vs multiple fractions). For each treatment session, initial setup accuracy was measured and corrected with Brainlab exactrac system and 6 degrees of freedom (6DoF) values (tx, ty, tz, rx, ry, rz) were recorded in mm or degree and resultant vectors for translations were calculated. The same was made at the end of the session (intrafraction movement). Patient reported comfort with a Visual Analog Scale (VAS) at the end of confection time and for treatment (for fractionated treatments average value of all scores was considered). VAS went from 0 (most uncomfortable) to 10 (very comfortable). Comparisons for accuracy and comfort were made with mixed model linear regression (R 3.0.1, package nlme). Regarding accuracy, the variable was the mean movement (resultant vector) for each patient. Results We report the results for 58 patients, two patients are not treated yet. Among the 28 patients of the DSPS group, seven received a fractionated treatment (either 3 or 28 fractions). In the Brainlab group, it was the case for six of the 30 patients. Setup accuracy and intrafraction motion are recorded in Table 1. Initial setup accuracy was significantly better with the DSPS mask (P < 0.01), particularly in the y direction (longitudinal) and around the x rotation (head tilt) where it showed less variability. There was no significant difference for intrafraction motion (P = 0.88), both masks showing submillimiter and subdegree accuracy on average. During confection, both masks were rated as comfortable (average VAS scores 8.7 and 8.4 for DSPS and Brainlab, P = 0.53). For treatment, DSPS was scored as more comfortable than Brainlab (average VAS scores 7.2 and 6.0, P = 0.04). Conclusion We could demonstrate that DSPS and Brainlab dedicated masks are both viable alternatives to invasive head frame for SRS, showing submillimeter and subdegree intrafraction motion. Initial setup accuracy was significantly better with DSPS, maybe due to the higher comfort reported by the patients. (Table Presented).
Meunier, C., Pauvert, M., Wergifosse, V., Delree, M., Wanet, M., Bihin, B., & Daisne, J. F. (2017). OC-0077: Comparison of setup accuracy, intrafractionmovement and comfort for two stereotactic masks. Radiotherapy and Oncology, 123, S40. https://doi.org/10.1016/s0167-8140(17)30521-2