TU‐H‐CAMPUS‐TeP1‐02: Seated Treatment: Setup Uncertainty Comparable to Supine

Abstract

Purpose:For some head and neck patients, positioning in the supine position is not well tolerated. For these patients, treatment in a seated position would be preferred. We have evaluated inter‐ and intra‐ fraction uncertainty of patient set‐up in a novel treatment chair which is compatible with modern linac designs.Methods:Five head‐and‐neck cancer patients were positioned in the chair, fitted with immobilization devices, and imaged with orthogonal X‐rays. The couch (with chair attached) was rotated to simulate delivery (without actual treatment), another set of images were acquired, providing a measure of intra‐fraction displacement. The patient then got off of and back onto the chair and the process was repeated, thus providing a measure of inter‐fraction set‐up uncertainty. Six sub‐regions in the head‐and‐neck were rigidly registered to evaluate local intra‐ and interfraction displacement. Image guidance was simulated by first registering one sub‐region; the residual displacement of other sub‐regions was then measured. Additionally, a patient questionnaire was administered to evaluate tolerance of the seated position.Results:The chair design is such that all advantages of couch motions may be utilized. Average inter‐ and intrafraction displacements of all sub‐regions in the seated position were less than 2 and 3 mm, respectively. When image guidance was simulated, interfraction displacements were reduced by an average of 4 mm, providing comparable setup to the supine position. The enrolled patients, who had no indication for a seated treatment position, reported no preference for the seated or the supine position.Conclusion:The novel chair design provides acceptable inter‐ and intra‐fraction displacement, with reproducibility similar to that observed for patients in the supine position. Such a chair will be utilized for patients who cannot tolerate the supine position and use with CBCT images for planning, in a fixed‐beam linac system, and for other treatment sites is under investigation.Funding: Varian Medical Systems