title: A motion-compensated image filter for low-dose fluoroscopy in a real-time tumor-tracking radiotherapy system.
abstract: In the real-time tumor-tracking radiotherapy system, a surrogate fiducial marker inserted in or near the tumor is detected by fluoroscopy to realize respiratory-gated radiotherapy. The imaging dose caused by fluoroscopy should be minimized. In this work, an image processing technique is proposed for tracing a moving marker in low-dose imaging. The proposed tracking technique is a combination of a motion-compensated recursive filter and template pattern matching. The proposed image filter can reduce motion artifacts resulting from the recursive process based on the determination of the region of interest for the next frame according to the current marker position in the fluoroscopic images. The effectiveness of the proposed technique and the expected clinical benefit were examined by phantom experimental studies with actual tumor trajectories generated from clinical patient data. It was demonstrated that the marker motion could be traced in low-dose imaging by applying the proposed algorithm with acceptable registration error and high pattern recognition score in all trajectories, although some trajectories were not able to be tracked with the conventional spatial filters or without image filters. The positional accuracy is expected to be kept within ±2 mm. The total computation time required to determine the marker position is a few milliseconds. The proposed image processing technique is applicable for imaging dose reduction.
authors.affiliation: Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Miyamoto
authors.affiliation: Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan masayori@med.hokudai.ac.jp.
authors.forename: Masayori
authors.initials: M
authors.lastname: Ishikawa
authors.affiliation: Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Sutherland
authors.affiliation: Department of Medical Physics, Hokkaido University Hospital, North-14 West-5, Kita-ku, Sapporo 060-8648, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Suzuki
authors.affiliation: Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Taeko
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Department of Medical Physics, Hokkaido University Hospital, North-14 West-5, Kita-ku, Sapporo 060-8648, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Toramatsu
authors.affiliation: Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Seishin
authors.initials: S
authors.lastname: Takao
authors.affiliation: Department of Medical Physics, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nihongi
authors.affiliation: Department of Radiology, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Division of Quantum Science and Engineering, Graduate School of Engineering, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Kikuo
authors.initials: K
authors.lastname: Umegaki
authors.affiliation: Department of Radiology, Graduate School of Medicine, Hokkaido University, North-15 West-7, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
mesh_terms: D016477:Artifacts; D003199:Computer Systems; D057918:Fiducial Markers; D005471:Fluoroscopy / Q000295:instrumentation / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods; D009038:Motion; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000295:instrumentation / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: image processing; imaging dose; motion compensation; real-time tracking; respiratory motion; respiratory-gated radiotherapy