title: Quality assurance and commissioning of an infrared marker-based patient positioning system for frameless extracranial stereotactic radiotherapy.
abstract: Rapid advancements in imaging technology have led to remarkable improvements in identification and localization of tumors, ushering the era of high-precision techniques in contemporary radiotherapy practice. However, uncertainties in patient set-up and organ motion during a course of fractionated radiotherapy can compromise precision of radiation therapy. Excellent accuracy has been achieved with invasive and non-invasive fixation systems for stereotactic radiotherapy. This report describes the commissioning procedure and Quality Assurance studies done to evaluate the accuracy of isocenter localization by an infrared marker-based positioning system (ExacTrac). The ExacTrac has two infrared cameras that emit and detect infrared rays from reflective markers and construct three-dimensional coordinates of each marker. It detects the difference of the actual isocenter position from the planned isocenter coordinates in three translational (lateral, longitudinal, vertical, or x,y,z axes) and three rotational axes (six degree of freedom). This study performed on a flat and static phantom shows excellent accuracy achieved by the ExacTrac system. The positioning accuracy of ExacTrac (± 1 mm translational displacement and ± 1° rotational errors) can be a valuable tool in implementing frameless extracranial stereotactic radiotherapy. Nevertheless, it needs to be further evaluated on patients with inherent motion and greater positional uncertainty before being adopted in clinical practice.
authors.affiliation: Department of Radiation Oncology, Advanced Centre for Treatment Research & Education in Cancer (ACTREC), Tata Memorial Centre, Kharghar, Navi Mumbai, India; ; Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
authors.forename: Tejpal
authors.initials: T
authors.lastname: Gupta
authors.forename: Reena
authors.initials: R
authors.lastname: Phurailatpam
authors.forename: Mishra
authors.initials: M
authors.lastname: Ajay
authors.forename: Pai
authors.initials: P
authors.lastname: Rajeshri
authors.forename: Mohindra
authors.initials: M
authors.lastname: Pranshu
authors.forename: Chopra
authors.initials: C
authors.lastname: Supriya
keywords: extracranial; infrared marker; patient positioning system; quality assurance; stereotactic radiotherapy