title: Scintigraphic detection of 125I seeds after permanent brachytherapy for prostate cancer.
abstract: The purpose of this investigation was to monitor the localization and migration of 125I seeds after permanent brachytherapy for prostate cancer using a new scintigraphic technique that may overcome the drawbacks of conventional x-ray methods.
  
  
  METHODS
  125I seeds emit gamma-rays with an average energy peak of 28 keV. We used a gamma-camera equipped with low-energy high-resolution collimators that were tuned to an energy level of 35 keV with a 70% window width. Sixteen patients with prostate cancer were examined after 125I seed insertion. The number of seeds remaining in the prostate was confirmed using pelvic CT for postoperative dose planning; however, seeds that had migrated outside the prostate could not be detected. Furthermore, the migrated seeds were not completely traceable using chest or abdominal radiography. Thus, we adopted a scintigraphic technique to perform this task. The evaluation of radiography and scintigraphy findings was masked, and the rates of migrated seed detection were statistically examined using the McNemar test. To localize the migrated seeds, we fused the scintigraphic images of the migrated seeds and the patients' contours.
  
  
  RESULTS
  Scintigraphy was successfully used to detect 20 migrated seeds of a total of 1,182 implanted seeds, whereas radiography was successfully used to detect 7. The sensitivity of the scintigraphy results was 20 of 20 (100%), whereas that of the radiography results was 7 of 20 (35%). Seed migration was detected in 11 of 16 patients (69%) using scintigraphy, whereas seed migration was detected in only 4 patients (25%) using radiography; this difference was statistically significant (P = 0.016).
  
  
  CONCLUSIONS
  Scintigraphy is more effective for detecting seed migration and monitoring the localization of 125I seeds than radiography. The precise anatomic location of migrated seeds can be pinpointed using fusion images. Scintigraphy may become a standard procedure for monitoring seed migration during 125I brachytherapy in patients with prostate cancer.
authors.affiliation: Division of Nuclear Medicine, International Medical Center of Japan, Tokyo, Japan.
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Kono
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kubota
authors.forename: Takuya
authors.initials: T
authors.lastname: Mitsumoto
authors.forename: Akitomo
authors.initials: A
authors.lastname: Tanaka
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ishibashi
authors.forename: Kazumi
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kimiteru
authors.initials: K
authors.lastname: Ito
authors.forename: Jun
authors.initials: J
authors.lastname: Itami
authors.forename: Mikio
authors.initials: M
authors.lastname: Kanemura
authors.forename: Shigeru
authors.initials: S
authors.lastname: Minowada
mesh_terms: D000368:Aged; D001918:Brachytherapy; D006801:Humans; D007457:Iodine Radioisotopes / Q000032:analysis / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D007457:Iodine Radioisotopes