Comparison Of Repositioning Accuracy And Comfort Survey In 2 Head Supports Used Inside The Same Available Immobilization Systems For Treatment Of Head And Neck Target

To compare setup reproducibility, comfort level and hardness reported by the patients between two head supports used in the same immobilization system. Additionally, the relationship between setup accuracy and patient comfort survey was also examined. Between March 2011 and February 2012, totally 35 patients undergoing head-and-neck RT were enrolled and all studied patients received the same immobilization device (standard thermoplastic head-and-shoulder mask, Type S mask) twice, and two different head supports were used. For each studied patient, both TIMO support and Silverman support were used to compare setup reproducibility by several types of measurement. All patients underwent simulation CT scans. A series of on-board images (OBIs) were taken at the start, during, and by the end of the RT course. The OBI images were subsequently co-registered and repositioning accuracy was examined by recording displacement including three axes at the isocenter and orthogonal planes. Furthermore, the patients’ reported comfort level and hardness between the two head supports were analyzed. Finally, we attempted to explore the association between repositioning accuracy and the patients’ subjective perception regarding comfort level and hardness. Totally, 351 OBI data sets were studied. Although absolute difference was very small between the two head supports regarding three displacement errors, spine curve, and mandible angle, Silverman support was associated with more limited repositioning displacement in AP and ML directions (paired t-test, p = 0.011, 0.004, respectively). As RT course proceeded, a trend was noted toward a greater variation in both spinal curve and mandible angle, suggesting reproducibility should be noticed as RT dose accumulates. In comfort survey, perception of hardness was positively correlated with comfort level in both head supports with weak but significant significance (Spearman's correlation coefficient = 0.387, p < 0.001). Moreover, although there was no any correlation between hardness of head supports and repositioning accuracy, comfort level was positively correlated with repositioning displacement in rotation (Pearson's correlation coefficient = 0.213, p < 0.001) in Silverman head support only. The current study has demonstrated that the available immobilization system equipped with either TIMO head support or Silverman head support provides satisfactory and nearly equivalent repositioning-related outcomes. In the future, we might consider leaving the choice between the two different head supports to the individual patient according to subjective perception of comfort level.