title: Prostate volume and implant configuration during 48 hours of temporary prostate brachytherapy: limited effect of oedema.
abstract: BACKGROUND
  In pulsed-dose rate prostate brachytherapy the dose is delivered during 48 hours after implantation, making the treatment sensitive to oedematic effects possibly affecting dose delivery. The aim was to study changes in prostate volume during treatment by analysing catheter configurations on three subsequent scans.
  
  
  METHODS
  Prostate expansion was determined for 19 patients from the change in spatial distribution of the implanted catheters, using three CT-scans: a planning CT (CT1) and two CTs after 24 and 48 hours (CT2, CT3). An additional 4 patients only received one repeat CT (after 24 hours). The mean radial distance (MRD) of all dwell positions to the geometric centre of all dwell positions used was calculated to evaluate volume changes. From three implanted markers changes in inter-marker distances were assessed. The relative shifts of all dwell positions were determined using catheter- and marker-based registrations. Wilcoxon signed-rank tests were performed to compare the results from the different time points.
  
  
  RESULTS
  The MRDs measured on the two repeat CTs were significantly different from CT1. The mean prostate volume change derived from the difference in MRD was +4.3% (range -9.3% to +15.6%) for CT1-CT2 (p < .05) and +4.4% (range -7.5% to +16.3%) for CT1-CT3 (p < .05). These values represented a mean increase of 1.2 cm(3) in the first 24 hours and 1.5 cm(3) in the subsequent 24 hours. There was no clear sign of prostate expansion from the change in inter-marker distance (CT1-CT2: 0.2 ± 1.8 mm; CT1-CT3: 0.6 ± 2.2 mm). Catheter configuration remained stable; shifts in catheter positions were largest in the C-C direction: 0 ± 1.8 mm for CT1-CT2 and 0 ± 1.4 mm for CT2-CT3.
  
  
  CONCLUSIONS
  The volume changes derived from catheter displacements were small and therefore considered clinically insignificant. Implant configuration remains stable during 2 days of treatment, confirming the safety of this technique.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, the Netherlands. a.m.dinkla@amc.uva.nl.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Dinkla
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, the Netherlands. b.r.pieters@amc.uva.nl.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Pieters
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, the Netherlands. c.koedooder@amc.uva.nl.
authors.forename: Kees
authors.initials: K
authors.lastname: Koedooder
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, the Netherlands. n.vanwieringen@amc.uva.nl.
authors.forename: Niek
authors.initials: N
authors.lastname: van Wieringen
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, the Netherlands. r.vanderlaarse@amc.uva.nl.
authors.forename: Rob
authors.initials: R
authors.lastname: van der Laarse
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, Meibergdreef 9, 1105, AZ, Amsterdam, the Netherlands. a.bel@amc.uva.nl.
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
mesh_terms: D001918:Brachytherapy / Q000009:adverse effects* / Q000379:methods*; D002408:Catheters, Indwelling / Q000009:adverse effects; D004487:Edema / Q000209:etiology; D006801:Humans; D008297:Male; D011467:Prostate / Q000473:pathology; D011471:Prostatic Neoplasms / Q000532:radiotherapy*