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

Eur J Nucl Med Mol Imaging. 2008 May;35(5):950-7. doi: 10.1007/s00259-007-0634-8. Epub 2008 Jan 12.


Purpose: 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.

Material and 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.

Conclusion: 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.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • False Negative Reactions
  • Female
  • Fluorodeoxyglucose F18* / pharmacokinetics
  • Humans
  • Iodine Radioisotopes*
  • Male
  • Middle Aged
  • Positron-Emission Tomography / methods*
  • Radiopharmaceuticals
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Thyroglobulin / blood*
  • Thyroid Neoplasms / blood*
  • Thyroid Neoplasms / diagnosis*
  • Tomography, X-Ray Computed / methods*


  • Iodine Radioisotopes
  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18
  • Thyroglobulin