title: Combined metabolic and morphologic imaging in thyroid carcinoma patients with elevated serum thyroglobulin and negative cervical ultrasonography: role of 124I-PET/CT and FDG-PET.
abstract: OBJECTIVE
  This study sought to compare iodine-124 positron emission tomography/computed tomography (124I-PET/CT) and 2-[18F]fluoro-2-deoxy-D: -glucose- (FDG-) PET in the detection of recurrent differentiated thyroid carcinoma (DTC) lesions in patients with increasing serum thyroglobulin (Tg), Tg-antibodies, or both, but without pathological cervical ultrasonography. We assessed the lesion detection accuracy of 124I-PET alone, CT alone, (124)I-PET/CT, FDG-PET, and all these modalities combined.
  
  
  METHODS
  The study included 21 patients (9 follicular, 12 papillary DTC) who had been rendered disease-free by thyroidectomy and radioiodine treatment (RIT) and followed up for 21-275 months after the last RIT. In all patients, FDG-PET was performed first. Within 1 week, 124I-PET/CT was performed 24 h after oral administration of 43 +/- 11 MBq 124I. Imaging results were correlated with further clinical follow-up with (n = 12) or without (n = 9) post-study histology as the reference standard.
  
  
  RESULTS
  The sensitivities for DTC lesion detection were: 124I-PET, 49%; CT, 67%; 124I-PET/CT, 80%; FDG-PET, 70%; and all modalities combined, 91%. For local recurrences (distant metastases), the sensitivities were: 124I-PET, 60% (45%); CT, 20% (84%); and FDG-PET, 65% (71%). One-third of lesions demonstrated pathological tracer uptake with both 124I- and FDG-PET, while two-thirds were positive with only one of these modalities.
  
  
  CONCLUSIONS
  Used together, 124I-PET and CT allow localization of foci of highly specific 124I uptake as well as non-iodine-avid lesions. The combination of 124I-PET/CT and FDG-PET improves restaging in recurrent DTC by enabling detection on whole-body scans of local recurrence or metastases that are often not found if only one of the methods or other imaging modalities are applied.
authors.affiliation: Department of Nuclear Medicine, University of Duisburg/Essen, Hufelandstrasse 55, 45122 Essen, Germany. lutz.freudenberg@uni-essen.de
authors.forename: L S
authors.initials: LS
authors.lastname: Freudenberg
authors.forename: G
authors.initials: G
authors.lastname: Antoch
authors.forename: A
authors.initials: A
authors.lastname: Frilling
authors.forename: W
authors.initials: W
authors.lastname: Jentzen
authors.forename: S J
authors.initials: SJ
authors.lastname: Rosenbaum
authors.forename: H
authors.initials: H
authors.lastname: Kühl
authors.forename: A
authors.initials: A
authors.lastname: Bockisch
authors.forename: R
authors.initials: R
authors.lastname: Görges
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005188:False Negative Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood* / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013954:Thyroglobulin