title: Verification of air-kerma strength of 125I seed for permanent prostate implants in Japan.
abstract: BACKGROUND
  To assure the physical quality of brachytherapy, we investigated the difference between measured and manufacturer's stated source strengths in a single model SourceTech Medical (STM)1251 (125)I seed.
  
  
  METHODS
  A well-type ionization chamber with a single-seed holder was used to measure the source strength of 2412 (125)I seeds before implant in 34 patients. The air-kerma strength was 0.450 U for all cases. The mean source strength for each patient was measured and compared with the manufacturer's stated value. The deviation from the measured value was compared with the tolerance range of the American Association of Physicists in Medicine (AAPM) TG-56 report's recommendation.
  
  
  RESULTS
  The measured source strength was higher than the manufacturer's stated value, with a median difference of 1% (range, 2% to 5%). Sixteen of the total of 2412 seeds (0.7%) were more than 5% different from the manufacturer's stated value. The median SD from the mean value was 2.2% (range, 1.1% to 2.5%) for all patients.
  
  
  CONCLUSIONS
  This is the first report of a single-seed assay performed for the model STM1251 (125)I seed. In this study the manufacturer's stated strength agreed well with the measured value. Nevertheless, the advisability of performing a single-seed assay at every institution should be considered, by referring to the appropriate regulations; for example, those used in the United States.
authors.affiliation: Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan. sumida@radonc.med.osaka-u.ac.jp
authors.forename: Iori
authors.initials: I
authors.lastname: Sumida
authors.forename: Masahiko
authors.initials: M
authors.lastname: Koizumi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ogata
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Akino
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Isohashi
authors.forename: Koji
authors.initials: K
authors.lastname: Konishi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshioka
authors.forename: Takehiro
authors.initials: T
authors.lastname: Inoue
mesh_terms: D001918:Brachytherapy; D004307:Dose-Response Relationship, Radiation; D004867:Equipment Design; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry*; D007564:Japan; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D019736:Prostheses and Implants; D011879:Radiotherapy Dosage
chemical_list: D007457:Iodine Radioisotopes