title: Stereotactic ultrasound for target volume definition in a patient with prostate cancer and bilateral total hip replacement.
abstract: OBJECTIVE
  Target-volume definition for prostate cancer in patients with bilateral metal total hip replacements (THRs) is a challenge because of metal artifacts in the planning computed tomography (CT) scans. Magnetic resonance imaging (MRI) can be used for matching and prostate delineation; however, at a spatial and temporal distance from the planning CT, identical rectal and vesical filling is difficult to achieve. In addition, MRI may also be impaired by metal artifacts, even resulting in spatial image distortion. Here, we present a method to define prostate target volumes based on ultrasound images acquired during CT simulation and online-matched to the CT data set directly at the planning CT.
  
  
  METHODS
  A 78-year-old patient with cT2cNxM0 prostate cancer with bilateral metal THRs was referred to external beam radiation therapy. T2-weighted MRI was performed on the day of the planning CT with preparation according to a protocol for reproducible bladder and rectal filling. The planning CT was obtained with the immediate acquisition of a 3-dimensional ultrasound data set with a dedicated stereotactic ultrasound system for online intermodality image matching referenced to the isocenter by ceiling-mounted infrared cameras. MRI (offline) and ultrasound images (online) were thus both matched to the CT images for planning. Daily image guided radiation therapy (IGRT) was performed with transabdominal ultrasound and compared with cone beam CT.
  
  
  RESULTS
  Because of variations in bladder and rectal filling and metal-induced image distortion in MRI, soft-tissue-based matching of the MRI to CT was not sufficient for unequivocal prostate target definition. Ultrasound-based images could be matched, and prostate, seminal vesicles, and target volumes were reliably defined. Daily IGRT could be successfully completed with transabdominal ultrasound with good accordance between cone beam CT and ultrasound.
  
  
  CONCLUSIONS
  For prostate cancer patients with bilateral THRs causing artifacts in planning CTs, ultrasound referenced to the isocenter of the CT simulator and acquired with intermodal online coregistration directly at the planning CT is a fast and easy method to reliably delineate the prostate and target volumes and for daily IGRT.
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany. Electronic address: judit.boda-heggemann@umm.de.
authors.forename: Judit
authors.initials: J
authors.lastname: Boda-Heggemann
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Haneder
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Ehmann
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Dwi Seno Kuncoro
authors.initials: DSK
authors.lastname: Sihono
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Wertz
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Mai
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kegel
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Sigrun
authors.initials: S
authors.lastname: Heitmann
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: von Swietochowski
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D054893:Cone-Beam Computed Tomography; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D014463:Ultrasonography; D001743:Urinary Bladder