title: Effect of a urinary catheter on seed position and rectal and bladder doses in CT-based post-implant dosimetry for prostate cancer brachytherapy.
abstract: OBJECTIVE
  To assess the variability in rectal and bladder dosimetric parameters determined according to post-implant computed tomography (CT) images in patients with or without a urethral catheter.
  
  
  METHODS
  Patients with prostate cancer who were scheduled to undergo CT after brachytherapy between October 2012 and January 2014 were included. We obtained CT series with and without a urinary catheter in each patient. We compared the rectal and bladder doses in 18 patients on each CT series.
  
  
  RESULTS
  The shifts in the seed positions between with and without a catheter in place were 1.3 ± 0.3 mm (mean ± standard deviation). The radiation doses to the rectum, as determined on the CT series, with a urethral catheter were higher than those on CT without a catheter (p < 0.001). Radiation doses to the bladder with a catheter were significantly lower than those without a catheter (p = 0.027).
  
  
  CONCLUSIONS
  Post-implant dosimetry (PID) with no catheter showed significantly lower rectal doses and higher bladder doses than those of PID with a catheter. We recommend the PID procedure for CT images in patients without a catheter. Use of CT with a catheter is limited to identifying urethral position.
authors.affiliation: Department of Radiation Oncology.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kunogi
authors.affiliation: Department of Radiation Oncology.
authors.forename: Nanae
authors.initials: N
authors.lastname: Yamaguchi
authors.affiliation: Department of Urology, Juntendo University, Hongo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Wakumoto
authors.affiliation: Department of Radiation Oncology.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sasai
keywords: CT-based; brachytherapy; prostate cancer; rectal dose; urinary catheter