title: Impact of transrectal ultrasound- and computed tomography-based seed localization on postimplant dosimetry in prostate brachytherapy.
abstract: OBJECTIVE
  To study the impact of seed localization, as performed by different observers using linked (125)I seeds, on postimplant dosimetry in prostate brachytherapy and, to compare transrectal ultrasound (TRUS)-based with CT-based approach for the dosimetric outcomes.
  
  
  METHODS
  Nineteen permanent prostate implants were conducted using linked (125)I seeds. Postimplant TRUS and CT images were acquired and prostate glands were, after implantation, delineated on all images by a single oncologist, who had performed all 19 seeding procedures. Six observers independently localized the seeds on both TRUS and CT images, from which the principle dosimetric parameters V(100) (volume of prostate that received the prescribed dose), V(150) (volume of prostate that received 150% of the prescribed dose), and D(90) (minimal dose delivered to 90% of the prostate) were directly calculated for each patient. A single-factor analysis of variance was first applied to determine interobserver variability in seed localization. A nonparametric comparison of the approach using TRUS and CT was then carried out by the Wilcoxon paired-sample test.
  
  
  RESULTS
  Analysis from the analysis of variance for TRUS showed that the null hypothesis for equal means, could not be rejected for all six observers based on a significance level alpha=0.05. TRUS-based and CT-based approaches were then cross compared by the Wilcoxon paired-sample test, which suggested that the null hypothesis was insignificant for V(100) and D(90), but was significant for V(150).
  
  
  CONCLUSIONS
  Both TRUS- and CT-imaging modalities provided indistinguishable postimplant dosimetry results as far as V(100) and D(90) were concerned. There was comparable observer independence between TRUS- and CT-based seed localization for linked-seed implant procedures. With other advantages that TRUS-imaging modality had over CT in the evaluation of postimplant dosimetry, TRUS would be a preferred choice in conjunction with linked seeds for intraoperative procedures in prostate brachytherapy.
authors.affiliation: Department of Radiation Oncology, Cooper University Hospital, Camden, NJ; Department of Mechanical Engineering, Lehigh University, Bethlehem, PA.
authors.forename: Meng-Sang
authors.initials: MS
authors.lastname: Chew
authors.affiliation: Department of Radiation Oncology, Cooper University Hospital, Camden, NJ. Electronic address: Xue-jinyu@cooperhealth.edu.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Xue
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Chris
authors.initials: C
authors.lastname: Houser
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Misic
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Junsheng
authors.initials: J
authors.lastname: Cao
authors.affiliation: Department of Radiation Oncology, Frankford Hospital, Philadelphia, PA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Cornwell
authors.affiliation: Department of Urology, Frankford Hospital, Philadelphia, PA.
authors.forename: Jay
authors.initials: J
authors.lastname: Handler
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Eric
authors.initials: E
authors.lastname: Gressen
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D019160:Endosonography / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome