title: Deflection Analysis of Different Needle Designs for Prostate Biopsy and Focal Therapy.
abstract: The biopsy needles currently used were designed for a transrectal biopsy and are known to experience significant deflection from the point of entry into the gland to the needle tip.
  
  
  
  Five designs were selected for testing: 18-gauge Bard, 15-gauge lancet tip needle with 12° vet-point cannula, and trocar tip needle with 12°, 15°, and 20° vet-point cannulas. The 15-gauge needle was designed to take a variable specimen sample between 20 and 60 mm, whereas the Bard needle specimen bed was fixed at 20 mm. The needles were bench tested on a spring-loaded platform and fired into gelatin matrix with modulus of elasticity similar to human prostate.
  
  
  
  The Bard device with lancet tip needle deflected an average of 0.9 mm (range 0.3-1.3 mm) and 1.9° (range 0.6°-2.8°). Increasing needle diameter from 18-gauge Bard to 15-gauge variable with the same lancet tip needle design resulted in an average deflection across the 3 test lengths of 0.9 mm (range 0-2.0 mm) and 0.9° (range 0°-2.0°) with no significant difference. On the contrary, the use of the 3-point trocar tip needles with 12°, 15°, and 20° vet-point cannulas demonstrated significant reduction in the extent of deflection in both millimeters and degrees. There was no deflection at the 2- and 4-cm shots for both spring loads and preloads for the 3 vet tip angles tested. At 6 cm, the 20° vet tip performed the best.
  
  
  
  We proposed a mechanism that provides more accurate prostate sampling by combining a 3-point trocar tip on the needle with a 20° vet tip on the cutting cannula. Using the phantom, mimicking prostate gland tissue density, no deflection was revealed between 20- and 60-mm biopsy lengths, which should permit a straight sample in the majority of prostate glands and improve cancer localization for focal therapy planning.
authors.affiliation: 1 Department of Urology and Radiation Oncology, The Icahn School of Medicine at Mount Sinai, Mount Sinai, NY, USA.
authors.forename: Nelson N
authors.initials: NN
authors.lastname: Stone
authors.affiliation: 2 Department of Urology, Bladder Health and Reconstructive Institute, Memorial Hospital Miramar, Miramar, FL, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Mouraviev
authors.affiliation: 3 Vention Medical, Boulder, CO, USA.
authors.forename: David
authors.initials: D
authors.lastname: Schechter
authors.affiliation: 3 Vention Medical, Boulder, CO, USA.
authors.forename: Josh
authors.initials: J
authors.lastname: Goetz
authors.affiliation: 4 Department of Pathology, University of Colorado Anschutz Medical Campus in Aurora, Aurora, CO, USA.
authors.forename: M Scott
authors.initials: MS
authors.lastname: Lucia
authors.affiliation: 5 Department of Urology, University of Colorado Anschutz Medical Campus in Aurora, Aurora, CO, USA.
authors.forename: E Erin
authors.initials: EE
authors.lastname: Smith
authors.affiliation: 5 Department of Urology, University of Colorado Anschutz Medical Campus in Aurora, Aurora, CO, USA.
authors.forename: E David
authors.initials: ED
authors.lastname: Crawford
mesh_terms: D001707:Biopsy, Needle / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D061705:Image-Guided Biopsy; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000628:therapy
keywords: deflection of biopsy needles; prostate cancer; transperineal template-mapping biopsy; transrectal ultrasound; trocar tip needle