title: Radioiodine therapy of benign thyroid disorders: what are the effective thyroidal half-life and uptake of 131I?
abstract: OBJECTIVE
  The use of radioiodine therapy is common in the treatment of benign thyroid disease. Council directive Euratom 97/43 requires that for all medical exposure of individuals for radiotherapeutic purposes exposures of target volumes should be individually planned. There are several strategies to accomplish this aim for radioiodine therapy including individual radioiodine uptake measurement and using either individual or mean effective radioiodine uptake and half-life. Although it is always simple to use standard activities, the effective thyroidal half-life and thyroidal uptake of I needs to be estimated individually to achieve optimal dosimetric results. We analyzed the radioiodine half-life and uptake in a large number of patients for use in a semi-individual calculation.
  
  
  METHODS
  Patients presenting consecutively between 1 January 2006 and 31 December 2007 were included in the study. Inclusion criteria were the control of hyperthyroidism and withdrawal of antithyroid drugs 2 days before preliminary radioiodine testing and therapy. Patients were treated for Graves' disease (n=363), nontoxic goitre (n=50), toxic goitre (n=639), or toxic uninodular adenoma (n=365). The effective half-life and uptake of I were estimated by uptake measurements after 24 h and 5 days during the preliminary radioiodine test, and serial measurements over 5 days during therapy.
  
  
  RESULTS
  The mean effective half-life of I measured during radioiodine therapy was 5.4 days in Graves' disease, 6.4 days in nontoxic goitre, 6.6 days in toxic goitre, and 5.7 days in toxic uninodular adenoma. The mean maximal uptake of I measured during radioiodine therapy was 64% in Graves' disease, 42% in nontoxic goitre, 38% in toxic goitre, and 31% in toxic uninodular adenoma.
  
  
  CONCLUSIONS
  These actual values analyzed here might be used for a semi-individual calculation of therapeutic activity when an individual approach is not possible.
authors.affiliation: Department of Nuclear Medicine, University of Cologne, Cologne D-50924, Germany. carsten.kobe@uk-koeln.de
authors.forename: Carsten
authors.initials: C
authors.lastname: Kobe
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eschner
authors.forename: Markus
authors.initials: M
authors.lastname: Wild
authors.forename: Ilka
authors.initials: I
authors.lastname: Rahlff
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Sudbrock
authors.forename: Matthias
authors.initials: M
authors.lastname: Schmidt
authors.forename: Markus
authors.initials: M
authors.lastname: Dietlein
authors.forename: Harald
authors.initials: H
authors.lastname: Schicha
mesh_terms: D000236:Adenoma / Q000532:radiotherapy; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006042:Goiter / Q000532:radiotherapy; D006111:Graves Disease / Q000532:radiotherapy; D006207:Half-Life; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D011878:Radiotherapy / Q000379:methods*; D013959:Thyroid Diseases / Q000532:radiotherapy*; D013964:Thyroid Neoplasms / Q000532:radiotherapy; D013997:Time Factors
chemical_list: D007457:Iodine Radioisotopes