Verification of air-kerma strength of 125I seed for permanent prostate implants in Japan.
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.
Sumida
Iori
I
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
Koizumi
Masahiko
M
Takahashi
Yutaka
Y
Ogata
Toshiyuki
T
Akino
Yuichi
Y
Isohashi
Fumiaki
F
Konishi
Koji
K
Yoshioka
Yasuo
Y
Inoue
Takehiro
T
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
D007457:Iodine Radioisotopes