Reproducibility of patient setup in the seated treatment position: A novel treatment chair design

Abstract

Radiotherapy in a seated position may be indicated for patients who are unable to lie on the treatment couch for the duration of treatment, in scenarios where a seated treatment position provides superior anatomical positioning and dose distributions, or for a low‐cost system designed using a fixed treatment beam and rotating seated patient. In this study, we report a novel treatment chair that was constructed to allow for three‐dimensional imaging and treatment delivery while ensuring robust immobilization, providing reproducibility equivalent to that in the traditional supine position. Five patients undergoing radiation treatment for head‐and‐neck cancers were enrolled and were setup in the chair, with immobilization devices created, and then imaged with orthogonal X‐rays in a scenario that mimicked radiation treatments (without treatment delivery). Six subregions of the acquired images were rigidly registered to evaluate intra‐ and interfraction displacement and chair construction. Displacements under conditions of simulated image guidance were acquired by first registering one subregion; the residual displacement of other subregions was then measured. Additionally, we administered a patient questionnaire to gain patient feedback and assess comparison to the supine position. Average inter‐ and intrafraction displacements of all subregions in the seated position were less than 2 and 3 mm, respectively. When image guidance was simulated, L‐R and A‐P interfraction displacements were reduced by an average of 1 mm, providing setup of comparable quality to supine setups. The enrolled patients, who had no indication for a seated treatment position, reported no preference in the seated or the supine position. The novel chair design provides acceptable inter‐ and intrafraction displacement, with reproducibility equivalent to that reported for patients in the supine position. Patient feedback will be incorporated in the refinement of the chair, facilitating treatment of head‐and‐neck cancer in patients who are unable to lie for the duration of treatment or for use in an economical fixed‐beam setup.

A CBCT study of the gravity-induced movement in rotating rabbits

“…While prototype small animal irradiators envisaged fixed sources and rotation stages rotate about a vertical axis, which negates the impact of gravity induced motion (Matinfar et al 2009), the commercial units have horizontal subject stages and rotating x-ray gantries (PXi Precision X 2015, Xstrahl Medical 2015). Vertical CT (Shah et al 2009) and seated fixed-beam treatments (Pankuch 2015, McCarroll et al 2017 are under development. Many cancer patients would be unable to maintain an immobilised upright or seated stance such as this over the course of radiotherapy treatment, or it may be undesirable as it limits the available beam entry paths to treatment areas.…”

Anatomical changes in the male pelvis between the supine and upright positions—A feasibility study for prostate treatments in the upright position

“…9,10 Several recent papers address the benefits and possible advantages of upright treatments and the rationale to re-consider treating patients in the upright orientation again. 1,2,[11][12][13] Treating abdominal and pelvic organs in the upright position requires that the imaging be done in the same orientation since the impact of the gravitational changes on the organs will displace and change the shape of organs such as the bladder, liver, spleen, pancreas, the large and small bowel. [14][15][16][17] A search of the published literature revealed a lack of data regarding organ changes between supine and upright positions in the male pelvis.…”

Upright patient positioning for gantry-free breast radiotherapy: feasibility tests using a robotic chair and specialised bras

“…Small-scale published studies suggest that upright radiotherapy may increase comfort for subsets of patients. In the context of head and neck radiotherapy, a sample of 5 patients reported slightly increased comfort for their back and arms, positioned upright relative to supine ( 14 ). Further research into upright positioning for a cohort of 16 patients who received conventional, supine radiotherapy to the pelvis, reports an average patient comfort score of 4.1 out of a maximum of 5 (range 3:5) for upright positioning, compared to 3.9 (range 2:5) for supine positioning ( 15 ).…”