Quality assurance of a system for improved target localization and patient set-up that combines real-time infrared tracking and stereoscopic X-ray imaging

• Published in: Radiotherapy and oncology Vol. 67; no. 1; pp. 129 - 141
• Main Authors: Verellen, Dirk, Soete, Guy, Linthout, Nadine, Van Acker, Swana, De Roover, Patsy, Vinh-Hung, Vincent, Van de Steene, Jan, Storme, Guy
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01-04-2003
• Subjects: Algorithms; Automated patient positioning; Computer Graphics; Humans; Infrared markers; Intra-fractional correction of three-dimensional set-up errors; Phantoms, Imaging; Quality Assurance, Health Care; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Conformal - instrumentation; Radiotherapy, Conformal - standards; Stereoscopic X-ray imaging; Automated patient positioning; Intra-fractional correction of three-dimensional set-up errors; Infrared markers; Stereoscopic X-ray imaging
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/S0167-8140(02)00385-7

Background and purpose: The aim of this study is to investigate the positional accuracy of a prototype X-ray imaging tool in combination with a real-time infrared tracking device allowing automated patient set-up in three dimensions.
Material and methods: A prototype X-ray imaging tool has been integrated with a commercially released real-time infrared tracking device. The system, consisting of two X-ray tubes mounted to the ceiling and a centrally located amorphous silicon detector has been developed for automated patient positioning from outside the treatment room prior to treatment. Two major functions are supported: (a) automated fusion of the actual treatment images with digitally reconstructed radiographs (DRRs) representing the desired position; (b) matching of implanted radio opaque markers. Measurements of known translational (up to 30.0
mm) and rotational (up to 4.0°) set-up errors in three dimensions as well as hidden target tests have been performed on anthropomorphic phantoms.
Results: The system's accuracy can be represented with the mean three-dimensional displacement vector, which yielded 0.6
mm (with an overall SD of 0.9
mm) for the fusion of DRRs and X-ray images. Average deviations between known translational errors and calculations varied from −0.3 to 0.6
mm with a standard deviation in the range of 0.6–1.2
mm. The marker matching algorithm yielded a three-dimensional uncertainty of 0.3
mm (overall SD: 0.4
mm), with averages ranging from 0.0 to 0.3
mm and a standard deviation in the range between 0.3 and 0.4
mm.
Conclusions: The stereoscopic X-ray imaging device integrated with the real-time infrared tracking device represents a positioning tool allowing for the geometrical accuracy that is required for conformal radiation therapy of abdominal and pelvic lesions, within an acceptable time-frame.