External dose rates in radioiodine treatment of benign goitre: Estimation versus direct measurement

Objective. According to European recommendations, the external dose rate (ED) in radioiodine-treated goitre patients can be determined by estimating from calculation of the residual activity (RA) in the patient based on radioiodine uptake measurements or by measuring ED directly. In the European gui...

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Bibliographic Details
Published in:Scandinavian journal of clinical and laboratory investigation 2006, Vol.66 (6), p.509-516
Main Authors: Jørgensen, H. B., Høilund-Carlsen, P. F., Nielsen, V. E.
Format: Article
Language:English
Subjects:
Administration, Oral
Adult
Aged
Aged, 80 and over
Biometry
Dose-response relationship
Female
Goiter - metabolism
Goiter - radiotherapy
goitre
Humans
iodine isotopes
Iodine Radioisotopes - administration & dosage
Iodine Radioisotopes - pharmacokinetics
Iodine Radioisotopes - therapeutic use
Male
Middle Aged
radiation
radiometry radiotherapy
Radiotherapy Dosage
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Summary:Objective. According to European recommendations, the external dose rate (ED) in radioiodine-treated goitre patients can be determined by estimating from calculation of the residual activity (RA) in the patient based on radioiodine uptake measurements or by measuring ED directly. In the European guidelines, "Radiation Protection 97", it is assumed that an RA of 600 MBq 131I causes an ED of 30 Sv h at a distance of 1 m. This implies a slope of 0.05 µSv h MBq for the ratio ED RA relationship, but, theoretically, this ratio is higher, at 0.07, a difference that is due to measurement in air versus in a scattering medium. We sought to investigate what the true ratio might be. Material and methods. Sixty-six patients scheduled for radioiodine treatment of benign goitre (mean size 102 mL, range 20-440), who received 131I orally (mean 984 MBq, range 173-3700) were examined. After 24 h and 96 h iodine uptake percentage we examined 7269 patients scheduled for radioiodine treatment of benign goitre (mean size 1042 mL, range 20-440) who received 131I orally (mean 101,100 MBq, range 180-3700). After 24 h and 96 h, the iodine uptake was determined, RA calculated and ED measured using a hand-held dosimeter. Results. At 24 and 96 h, we observed a slope ratio of 0.103 µSv h MBq (95 % CI: 0.09564-0.111) and 0.101 µSv h MBq (95 % CI: 0.0915-0.11107), respectively, for the ED RA relationship. None of the confidence intervals included the value 0.05 µSv h MBq, reflecting that the observed slopes differed significantly from the expected slope (p
ISSN:0036-5513
1502-7686
DOI:10.1080/00365510600844663