title: Comparing pre-therapeutic124I and131I uptake tests with intra-therapeutic131I uptake in benign thyroid disorders.
abstract: OBJECTIVE
  124I-PET/CT can be used for pre-therapeutic assessment of radioactive iodine uptake in benign thyroid disorders, however systematic comparisons with intra-therapeutic uptake are still lacking for these disorders. The goals of this study were to compare124I RAIU and conventional131I RAIU tests with each other; to compare both tests with intra-therapeutic uptake (reference); and to verify the time course of radioactive iodine uptake at three time points (30, 102, and 336 h [14 days] post administration; p.a.).
  
  
  METHODS
  Thirteen patients with benign thyroid diseases underwent131I RAIU test and124I RAIU test one after another before the intra-therapeutic131I uptake (reference) was measured via short-range and long-range measurements. After correction for decay, relative uptake differences were calculated and subjected to the Bland-Altman method for the evaluation of levels of agreement.
  
  
  RESULTS
  Radioactive iodine uptake tests with124I-PET/CT and131I probe did not show systematic deviations at any time point. Likewise, at 30 and 102 h p.a. there was no systematic discrepancy between pre-therapeutic and intra-therapeutic uptake levels. At 14 days p.a., however, both pre-therapeutic tests tended to overestimate the uptake compared to reference. Findings showed, for the first time with124I, that radioiodine therapy has some early radiobiological effects possibly limiting the accuracy of pre-therapeutic dosimetry.
  
  
  CONCLUSIONS
  124I RAIU tests represent a feasible alternative to standard131I RAIU tests. The additional benefits of124I-PET/CT (e.g., functional topography, inclusion of retrosternal areas, possibility to enable fusion imaging) may thus increase the scope of this technology in benign thyroid disorders.
authors.affiliation: Clinic of Nuclear Medicine, Jena University Hospital, Jena, Germany.
authors.forename: Falk
authors.initials: F
authors.lastname: Gühne
authors.affiliation: Clinic of Nuclear Medicine, Jena University Hospital, Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kühnel
authors.affiliation: Clinic of Nuclear Medicine, Jena University Hospital, Jena, Germany. martin.freesmeyer@med.uni-jena.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Freesmeyer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography; D013959:Thyroid Diseases / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D016896:Treatment Outcome
chemical_list: D007457:Iodine Radioisotopes
keywords: 124Iodine; Benign thyroid disorders; PET/CT; RAIU; Uptake