title: Prostate swelling and shift during high intensity focused ultrasound: implication for targeted focal therapy.
abstract: OBJECTIVE
  We quantified prostate swelling and the intraprostatic point shift during high intensity focused ultrasound using real-time ultrasound.
  
  
  METHODS
  The institutional review board approved this retrospective study. Whole gland high intensity focused ultrasound was done in 44 patients with clinically localized prostate cancer. Three high intensity focused ultrasound sessions were required to cover the entire prostate, including the anterior zone (session 1), middle zone (session 2) and posterior zone (session 3). Computer assisted 3-dimensional reconstructions based on 3 mm step-section images of intraoperative transrectal ultrasound were compared before and after each session.
  
  
  RESULTS
  Most prostate swelling and intraprostatic point shifts occurred during session 1. The median percent volume increase was 18% for the transition zone, 9% for the peripheral zone and 13% for the entire prostate. The volume percent increase in the transition zone (p <0.001), peripheral zone (p = 0.001) and entire prostate (p = 0.001) statistically depended on the volume of each area measured preoperatively. The median 3-dimensional intraprostatic shift was 3.7 mm (range 0.9 to 13) in the transition zone and 5.5 mm (range 0.2 to 14) in the peripheral zone. A significant negative linear correlation was found between the preoperative presumed circle area ratio, and the percent increase in prostate volume (p = 0.001) and shift (p = 0.01) during high intensity focused ultrasound.
  
  
  CONCLUSIONS
  We quantified significant prostate swelling and shift during high intensity focused ultrasound. Smaller prostates and a smaller preoperative presumed circle area ratio were associated with greater prostate swelling and intraprostatic shifts. Real-time intraoperative adjustment of the treatment plan impacts the achievement of precise targeting during high intensity focused ultrasound, especially in prostates with a smaller volume and/or a smaller preoperative presumed circle area ratio.
authors.affiliation: University of Southern California Institute of Urology, Hillard and Roclyn Herzog Center for Prostate Cancer Focal Therapy, Keck School of Medicine, University of Southern California, Los Angeles, California; Department of Urology, Tokai University Hachioji Hospital, Hachioji, Japan.
authors.forename: Sunao
authors.initials: S
authors.lastname: Shoji
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Uchida
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nakamoto
authors.forename: Hakushi
authors.initials: H
authors.lastname: Kim
authors.forename: Andre Luis
authors.initials: AL
authors.lastname: de Castro Abreu
authors.forename: Scott
authors.initials: S
authors.lastname: Leslie
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Sato
authors.forename: Inderbir S
authors.initials: IS
authors.lastname: Gill
authors.forename: Osamu
authors.initials: O
authors.lastname: Ukimura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004487:Edema / Q000150:complications*; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D011469:Prostatic Diseases / Q000150:complications*; D011471:Prostatic Neoplasms / Q000150:complications* / Q000473:pathology / Q000601:surgery*; D012189:Retrospective Studies; D016896:Treatment Outcome; D036761:Ultrasound, High-Intensity Focused, Transrectal
keywords: 3-dimensional; 3D; HIFU; PCAR; PZ; TRUS; TZ; edema; high intensity focused ultrasound; high-intensity focused; high-intensity focused ultrasound ablation; peripheral zone; preoperative presumed circle area ratio; prostate; prostatic neoplasms; transition zone; transrectal; transrectal ultrasound; ultrasound