title: Three-dimensional transrectal ultrasound guided high-dose-rate prostate brachytherapy: A comparison of needle segmentation accuracy with two-dimensional image guidance.
abstract: OBJECTIVE
  Conventional transrectal ultrasound guided high-dose-rate prostate brachytherapy (HDR-BT) uses an axially acquired image set for organ segmentation and 2D sagittal images for needle segmentation. Sagittally reconstructed 3D (SR3D) transrectal ultrasound enables both organ and needle segmentation and has the potential to reduce organ-needle alignment uncertainty. This study compares the accuracy of needle tip localization between the conventional 2D sagittally assisted axially reconstructed (SAAR) and SR3D approaches.
  
  
  METHODS
  Twelve patients underwent SAAR-guided HDR-BT, during which SR3D images were acquired for subsequent segmentation and analysis. A total of 183 needles were investigated. Needle end-length measurements were taken, providing a gold standard for insertion depths. Dosimetric impact of insertion depth errors (IDEs) on clinical treatment plans was assessed.
  
  
  RESULTS
  SR3D guidance provided statistically significantly smaller IDEs than SAAR guidance with a mean ± SD of -0.6 ± 3.2 mm and 2.8 ± 3.2 mm, respectively (p < 0.001). Shadow artifacts were found to obstruct the view of some needle tips in SR3D images either partially (12%) or fully (10%); however, SR3D IDEs had a statistically significantly smaller impact on prostate V100% than SAAR IDEs with mean ± SD decreases of -1.2 ± 1.3% and -6.5 ± 6.7%, respectively (p < 0.05).
  
  
  CONCLUSIONS
  SR3D-guided HDR-BT eliminates a source of systematic uncertainty from the SAAR-guided approach, providing decreased IDEs for most needles, leading to a significant decrease in dosimetric uncertainty. Although imaging artifacts can limit the accuracy of tip localization in a subset of needles, we identified a method to mitigate these artifacts for clinical implementation.
authors.affiliation: Medical Biophysics, The University of Western Ontario, London, ON, Canada; Robarts Imaging Research Laboratories, London, ON, Canada. Electronic address: whrinivi@uwo.ca.
authors.forename: William Thomas
authors.initials: WT
authors.lastname: Hrinivich
authors.affiliation: Medical Biophysics, The University of Western Ontario, London, ON, Canada; Oncology, University of Western Ontario, London, ON, Canada; London Regional Cancer Program, London, ON, Canada.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Hoover
authors.affiliation: Medical Biophysics, The University of Western Ontario, London, ON, Canada; Oncology, University of Western Ontario, London, ON, Canada; London Regional Cancer Program, London, ON, Canada.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Surry
authors.affiliation: Robarts Imaging Research Laboratories, London, ON, Canada.
authors.forename: Chandima
authors.initials: C
authors.lastname: Edirisinghe
authors.affiliation: Robarts Imaging Research Laboratories, London, ON, Canada.
authors.forename: Jacques
authors.initials: J
authors.lastname: Montreuil
authors.affiliation: Oncology, University of Western Ontario, London, ON, Canada; London Regional Cancer Program, London, ON, Canada.
authors.forename: David
authors.initials: D
authors.lastname: D'Souza
authors.affiliation: Medical Biophysics, The University of Western Ontario, London, ON, Canada; Robarts Imaging Research Laboratories, London, ON, Canada; Oncology, University of Western Ontario, London, ON, Canada; Physics and Astronomy, University of Western Ontario, London, ON, Canada.
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenster
authors.affiliation: Medical Biophysics, The University of Western Ontario, London, ON, Canada; Oncology, University of Western Ontario, London, ON, Canada; London Regional Cancer Program, London, ON, Canada; Physics and Astronomy, University of Western Ontario, London, ON, Canada.
authors.forename: Eugene
authors.initials: E
authors.lastname: Wong
mesh_terms: D016477:Artifacts; D001918:Brachytherapy / Q000379:methods*; D019160:Endosonography; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D009339:Needles; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D018084:Ultrasonography, Interventional / Q000379:methods; D035501:Uncertainty
keywords: 3D ultrasound; High-dose-rate brachytherapy; Prostate cancer; Transrectal ultrasound