Blood dosimetry from a single measurement of the whole body radioiodine retention in patients with differentiated thyroid carcinoma.
A simple method is presented to estimate the radiation-absorbed dose to the blood after radioiodine administration from a single external measurement of the whole-body retention in patients suffering from differentiated thyroid cancer. The blood dose is calculated applying the formalism of the Medical International Radiation Dose Committee under the assumptions that whole-body activity decays exponentially and that 14% of the whole-body residence time can be attributed to the blood. Accuracy and applicability of the method were tested based on data from 29 assessments, 18 pre-therapeutic tracer studies, and 11 ablation therapies, with whole-body and blood-retention measurements over at least 4 days. The mean of the absolute deviations between estimates and actual blood doses was found to be 14%, if external whole-body counting was performed on day 1 or 2 after radioiodine administration. This simple formalism is: 1) applicable to pre-therapeutic dosimetry for remnant ablation or treatment of metastases in a blood dose-based treatment concept and 2) applicable to blood-dose estimates after radioiodine therapy to determine radiation exposure. When combined with a measurement of the whole body retention 1 or 2 days after radioiodine administration this single time-point method closely approximates the classic, yet much more labor intensive multi-day dosimetry that measures both blood and whole-body activities.
Hänscheid
Heribert
H
Department of Nuclear Medicine, University of Würzburg, Würzburg, Germany. haenscheid@nuklearmedizin.uni-wuerzburg.de
Lassmann
Michael
M
Luster
Markus
M
Kloos
Richard T
RT
Reiners
Christoph
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012062:Relative Biological Effectiveness; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D014018:Tissue Distribution; D014915:Whole-Body Counting; D055815:Young Adult
D007457:Iodine Radioisotopes