Considerations for Upright Particle Therapy Patient Positioning and Associated Image Guidance

Abstract

Particle therapy is a rapidly growing field in cancer therapy. Worldwide, over 100 centers are in operation, and more are currently in construction phase. The interest in particle therapy is founded in the superior target dose conformity and healthy tissue sparing achievable through the particles’ inverse depth dose profile. This physical advantage is, however, opposed by increased complexity and cost of particle therapy facilities. Particle therapy, especially with heavier ions, requires large and costly equipment to accelerate the particles to the desired treatment energy and steer the beam to the patient. A significant portion of the cost for a treatment facility is attributed to the gantry, used to enable different beam angles around the patient for optimal healthy tissue sparing. Instead of a gantry, a rotating chair positioning system paired with a fixed horizontal beam line presents a suitable cost-efficient alternative. Chair systems have been used already at the advent of particle therapy, but were soon dismissed due to increased setup uncertainty associated with the upright position stemming from the lack of dedicated image guidance systems. Recently, treatment chairs gained renewed interest due to the improvement in beam delivery, commercial availability of vertical patient CT imaging and improved image guidance systems to mitigate the problem of anatomical motion in seated treatments. In this review, economical and clinical reasons for an upright patient positioning system are discussed. Existing designs targeted for particle therapy are reviewed, and conclusions are drawn on the design and construction of chair systems and associated image guidance. Finally, the different aspects from literature are channeled into recommendations for potential upright treatment layouts, both for retrofitting and new facilities.

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

“…Two recent papers from Sulman et al 1 . and Volz et al 2 . provide summaries of the initial uses of upright treatments in the early days of radiation therapy.…”

“…provide summaries of the initial uses of upright treatments in the early days of radiation therapy. When CT scanners were introduced to the market circa 1975, external beam radiation therapy moved to a model of treating patients in a supine posture to match the position in which the CT images were acquired 1,2 . Several attempts were made in the 80′s to develop upright CT scanners to scan patients in either a standing position for treatments using the Fermilab fixed horizontal neutron beam 3,4 or in the seated position for particle therapy at the Lawrence Berkeley Laboratory (LBL), 5,6 the Harvard Cyclotron Laboratory (HCL) 7 and the HIMAC facility in Japan 8 .…”

“…Nevertheless, the seated position is still used regularly for intracranial treatments at many particle therapy facilities 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 1,2,11–13 . 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 14–17 .…”

“…Treating patients in the upright position using external beam radiation therapy has a long history. Two recent papers from Sulman et al 1 and Volz et al 2 provide summaries of the initial uses of upright treatments in the early days of radiation therapy. When CT scanners were introduced to the market circa 1975, external beam radiation therapy moved to a model of treating patients in a supine posture to match the position in which the CT images were acquired.…”

“…When CT scanners were introduced to the market circa 1975, external beam radiation therapy moved to a model of treating patients in a supine posture to match the position in which the CT images were acquired. 1,2 Several attempts were made in the 80′s to develop upright CT scanners to scan patients in either a standing position for treatments using the Fermilab fixed horizontal neutron beam 3,4 or in the seated position for particle therapy at the Lawrence Berkeley Laboratory (LBL), 5,6 the Harvard Cyclotron Laboratory (HCL) 7 and the HIMAC facility in Japan. 8 One major problem with the earlier systems was that the scan times were very long, mainly due to the infancy of the CT and computer technologies and the fact that continuous helical scanning was not yet available.…”