title: Objective automated assessment of time trends in prostate edema after (125)I implantation.
abstract: OBJECTIVE
  To present an objective automated method to determine time trends in prostatic edema resulting from iodine-125 brachytherapy.
  
  
  METHODS
  We followed 20 patients, implanted with stranded seeds, with seven consecutive CT scans to establish a time trend in prostate edema. Seed positions were obtained automatically from the CT series. The change in seed positions was used as surrogate for edema. Two approaches were applied to model changes in volume. (1) A cylindrical model: seeds from the compared distribution were linked to the reference distribution of Day 28. After alignment, the compared distribution was scaled in cylindrical coordinates, leading to the changes in radial and craniocaudal directions. The volume changes were calculated using these scaling factors. (2) A spherical model: distances of seeds to the center of gravity of all seeds were used as a measure to model volume changes.
  
  
  RESULTS
  With Day 28 as reference, the observed volume changes were smaller than 18% ± 6% (1 standard deviation) for the cylindrical model and 12% ± 7% for the spherical model. One day after implantation, the implanted prostate was less than 10% larger than in the reference scan for both models. Apart from Day 0, both models showed similar volume changes.
  
  
  CONCLUSIONS
  We present an objective automated method to determine changes in the implanted prostate volume, eliminating the influence of an observer in the assessment of the prostate size. The implanted volume change was less than 18% ± 7% for the studied group of 20 patients. Edema was 9% ± 5% from 1 day after implantation onward.
authors.affiliation: Department of Medical Physics, Radiotherapeutic Institute RISO, Deventer, The Netherlands. R.Westendorp@RISOmail.nl
authors.forename: Hendrik
authors.initials: H
authors.lastname: Westendorp
authors.forename: Rob
authors.initials: R
authors.lastname: Kattevilder
authors.forename: Arie
authors.initials: A
authors.lastname: van 't Riet
authors.forename: André W
authors.initials: AW
authors.lastname: Minken
authors.forename: Tonnis T
authors.initials: TT
authors.lastname: Nuver
authors.forename: Jos J
authors.initials: JJ
authors.lastname: Immerzeel
authors.forename: Carel J
authors.initials: CJ
authors.lastname: Hoekstra
mesh_terms: D001918:Brachytherapy / Q000009:adverse effects*; D004487:Edema / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008962:Models, Theoretical; D009929:Organ Size / Q000528:radiation effects; D011469:Prostatic Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D013997:Time Factors; D014057:Tomography, X-Ray Computed
chemical_list: D007457:Iodine Radioisotopes