SU‐E‐T‐359: Patients Could (and Should) Be Treated in An Upright Position

Purpose: Treating patients in an upright (seated) position has several potential advantages including increased lung volume/reduced respiratory motion (lung patients) giving an improved lung DVH, moving other healthy tissue away from the treatment beams (e.g. breast for Hodgkins lymphoma patients), and improved comfort (HN patients with excess mucus secretion, patients with compromised lung function, etc.). We report on efforts to develop the tools/techniques to add upright treatments to the modern radiotherapy armory. Methods: The following steps have been taken towards treating patients in an upright position: (1) A novel MRI scanner that allows scans to be taken at any angle between vertical and horizontal positions was used to take volume scans and sagittal movies of 5 volunteers in vertical and supine positions. Lung volumes and motion were compared. (2) An innovative treatment chair and immobilization approach has been prototyped. The chair attaches to the treatment couch, allowing full use of the LINACs on‐board imaging and remote motion functions. (3) kV cone‐beam CT images have been acquired of upright phantoms using the Truebeam with the gantry at 0degrees and rotating the couch instead of the gantry. (4) Treatment planning studies have been completed for HN and thoracic treatments. Results: (1) Lung volume is increased by 6–53% and motion reduced by 1‐4mm, when patients are positioned in an upright position. (2) The chair has good comfort and immobilization. End‐of‐couch weight‐constraint is sufficient with the TrueBeam couch, but limits use for older couches. (3) Upright CBCTs are possible, although work is needed to improve the image quality. (4) We have quantified gantry/patient collision risks, and understand the gantry/couch angle combinations that will be used for treatment. Conclusion: Good progress has been made in developing the techniques/tools to treat patients in an upright position. Partially funded by Varian Medical Systems.