title: Geometric evaluation of systematic transrectal ultrasound guided prostate biopsy.
abstract: OBJECTIVE
  Transrectal ultrasound guided prostate biopsy results rely on physician ability to target the gland according to the biopsy schema. However, to our knowledge it is unknown how accurately the freehand, transrectal ultrasound guided biopsy cores are placed in the prostate and how the geometric distribution of biopsy cores may affect the prostate cancer detection rate.
  
  
  METHODS
  To determine the geometric distribution of cores, we developed a biopsy simulation system with pelvic mock-ups and an optical tracking system. Mock-ups were biopsied in a freehand manner by 5 urologists and by our transrectal ultrasound robot, which can support and move the transrectal ultrasound probe. We compared 1) targeting errors, 2) the accuracy and precision of repeat biopsies, and 3) the estimated significant prostate cancer (0.5 cm(3) or greater) detection rate using a probability based model.
  
  
  RESULTS
  Urologists biopsied cores in clustered patterns and under sampled a significant portion of the prostate. The robot closely followed the predefined biopsy schema. The mean targeting error of the urologists and the robot was 9.0 and 1.0 mm, respectively. Robotic assistance significantly decreased repeat biopsy errors with improved accuracy and precision. The mean significant prostate cancer detection rate of the urologists and the robot was 36% and 43%, respectively (p <0.0001).
  
  
  CONCLUSIONS
  Systematic biopsy with freehand transrectal ultrasound guidance does not closely follow the sextant schema and may result in suboptimal sampling and cancer detection. Repeat freehand biopsy of the same target is challenging. Robotic assistance with optimized biopsy schemas can potentially improve targeting, precision and accuracy. A clinical trial is needed to confirm the additional benefits of robotic assistance.
authors.affiliation: James Buchanan Brady Urological Institute, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287-2101, USA. mhan1@jhmi.edu
authors.forename: Misop
authors.initials: M
authors.lastname: Han
authors.forename: Doyoung
authors.initials: D
authors.lastname: Chang
authors.forename: Chunwoo
authors.initials: C
authors.lastname: Kim
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Lee
authors.forename: Yihe
authors.initials: Y
authors.lastname: Zuo
authors.forename: Hyung-Joo
authors.initials: HJ
authors.lastname: Kim
authors.forename: Doru
authors.initials: D
authors.lastname: Petrisor
authors.forename: Bruce
authors.initials: B
authors.lastname: Trock
authors.forename: Alan W
authors.initials: AW
authors.lastname: Partin
authors.forename: Ronald
authors.initials: R
authors.lastname: Rodriguez
authors.forename: H Ballentine
authors.initials: HB
authors.lastname: Carter
authors.forename: Mohamad
authors.initials: M
authors.lastname: Allaf
authors.forename: Jongwon
authors.initials: J
authors.lastname: Kim
authors.forename: Dan
authors.initials: D
authors.lastname: Stoianovici
mesh_terms: D062005:Biopsy, Large-Core Needle / Q000295:instrumentation* / Q000379:methods; D003198:Computer Simulation; D019160:Endosonography / Q000379:methods; D006801:Humans; D061705:Image-Guided Biopsy / Q000379:methods; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging* / Q000473:pathology*; D015203:Reproducibility of Results; D012371:Robotics; D012680:Sensitivity and Specificity; D036761:Ultrasound, High-Intensity Focused, Transrectal / Q000379:methods*