title: Prostate CT segmentation method based on nonrigid registration in ultrasound-guided CT-based HDR prostate brachytherapy.
abstract: OBJECTIVE
  The technological advances in real-time ultrasound image guidance for high-dose-rate (HDR) prostate brachytherapy have placed this treatment modality at the forefront of innovation in cancer radiotherapy. Prostate HDR treatment often involves placing the HDR catheters (needles) into the prostate gland under the transrectal ultrasound (TRUS) guidance, then generating a radiation treatment plan based on CT prostate images, and subsequently delivering high dose of radiation through these catheters. The main challenge for this HDR procedure is to accurately segment the prostate volume in the CT images for the radiation treatment planning. In this study, the authors propose a novel approach that integrates the prostate volume from 3D TRUS images into the treatment planning CT images to provide an accurate prostate delineation for prostate HDR treatment.
  
  
  METHODS
  The authors' approach requires acquisition of 3D TRUS prostate images in the operating room right after the HDR catheters are inserted, which takes 1-3 min. These TRUS images are used to create prostate contours. The HDR catheters are reconstructed from the intraoperative TRUS and postoperative CT images, and subsequently used as landmarks for the TRUS-CT image fusion. After TRUS-CT fusion, the TRUS-based prostate volume is deformed to the CT images for treatment planning. This method was first validated with a prostate-phantom study. In addition, a pilot study of ten patients undergoing HDR prostate brachytherapy was conducted to test its clinical feasibility. The accuracy of their approach was assessed through the locations of three implanted fiducial (gold) markers, as well as T2-weighted MR prostate images of patients.
  
  
  RESULTS
  For the phantom study, the target registration error (TRE) of gold-markers was 0.41 ± 0.11 mm. For the ten patients, the TRE of gold markers was 1.18 ± 0.26 mm; the prostate volume difference between the authors' approach and the MRI-based volume was 7.28% ± 0.86%, and the prostate volume Dice overlap coefficient was 91.89% ± 1.19%.
  
  
  CONCLUSIONS
  The authors have developed a novel approach to improve prostate contour utilizing intraoperative TRUS-based prostate volume in the CT-based prostate HDR treatment planning, demonstrated its clinical feasibility, and validated its accuracy with MRIs. The proposed segmentation method would improve prostate delineations, enable accurate dose planning and treatment delivery, and potentially enhance the treatment outcome of prostate HDR brachytherapy.
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: Peter
authors.initials: P
authors.lastname: Rossi
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: Tomi
authors.initials: T
authors.lastname: Ogunleye
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: David M
authors.initials: DM
authors.lastname: Marcus
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: Ashesh B
authors.initials: AB
authors.lastname: Jani
authors.affiliation: Department of Radiology and Imaging Sciences, Emory University, Atlanta, Georgia 30322.
authors.forename: Hui
authors.initials: H
authors.lastname: Mao
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Curran
authors.affiliation: Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322.
authors.forename: Tian
authors.initials: T
authors.lastname: Liu
mesh_terms: D001918:Brachytherapy; D057785:Catheters; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007432:Intraoperative Period; D008297:Male; D015588:Observer Variation; D009929:Organ Size; D019047:Phantoms, Imaging; D011467:Prostate / Q000000981:diagnostic imaging* / Q000473:pathology / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography