F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and Tc-99m pertechnate scan findings of a patient with unilateral subacute thyroiditis

Diagnostic Value of 2-[18F]FDG PET/CT in a Patient with Atypical Subacute Thyroiditis: A Case Report

Simple Summary

Positron emission tomography/computed tomography (PET/CT) imaging with 2-deoxy-2-[¹⁸F]fluoro-d-glucose (2-[¹⁸F]FDG) could be a useful diagnostic tool to detect foci of infection or inflammation in patients with fever of unknown origin (FUO) or with inflammation of unknown origin (IUO). We report a case of a patient originally presenting with a clinical history of FUO and later with persistent high-sensitivity C-reactive protein (hsCRP) levels, even after antibiotic therapy. The patient underwent 2-[¹⁸F]FDG PET/CT to investigate and to localize a possible focus of infection or inflammation. Since only 2-[¹⁸F]FDG hotspots were detected in both thyroid lobes, specific thyroid diagnostic examinations were performed. Subacute thyroiditis (SAT) was then diagnosed, and other possible causes of FUO or IUO were excluded. We found it interesting to present this case to illustrate the potential diagnostic value of 2-[¹⁸F]FDG PET/CT imaging in patients with atypical SAT presenting only with FUO.

Abstract

Background: Positron emission tomography/computed tomography (PET/CT) imaging with 2-deoxy-2-[¹⁸F]fluoro-d-glucose (2-[¹⁸F]FDG) is a sensitive diagnostic imaging modality in oncology and could be a useful diagnostic tool in patients with fever of unknown origin (FUO) or with inflammation of unknown origin (IUO). Case presentation: We report a case of a patient originally presenting with a clinical history of FUO and later with persistent high-sensitivity C-reactive protein (hsCRP) levels, even after antibiotic therapy. The patient underwent 2-[¹⁸F]FDG PET/CT to investigate and to localize a possible focus of infection or inflammation. 2-[¹⁸F]FDG hotspots were detected in both thyroid lobes. Thyroid diagnostic examinations and follow up were performed. Subacute thyroiditis (SAT) was then diagnosed by thyroid examinations, and other possible causes of FUO or IUO were not found. Conclusion: This case illustrates the potential diagnostic value of 2-[¹⁸F]FDG PET/CT in patients with atypical SAT, who originally present with only a clinical history of FUO.

The Role of 18F-FDG PET/CT in the Management of the Autoimmune Thyroid Diseases

Objective: It is a well-known fact that positron emission tomography (PET) is an effective tool in the assessment of thyroid focal lesions, however only few studies so far have investigated its role in monitoring of autoimmune thyroid diseases (AITDs). The aim of this study is to assess if PET scan may be useful for the assessment of the thyroid gland in patients with an AITD-Hashimoto's thyroiditis. Methods: We evaluated twenty subjects with diagnosed Hashimoto's thyroiditis (proven by presence of elevated thyroid antibodies level and by thyroid imaging). The maximum standardized uptake value (SUV-max) of the thyroid parenchyma was measured using ¹⁸F-FDG-PET/CT. Control group consisted of patients who have been in carcinoma remission for other reasons than thyroid cancer and who had been investigated by PET scan to exclude carcinoma recurrence. All control group subjects had their thyroid glands intact, none of them had a medical history of thyroid disease including thyroid nodules. AITDs had been excluded in all control group subjects. STATISTICA 13.1 software was used for statistical analysis. Results: Results: The SUV-max was significantly higher in patients with an AITD than in healthy subjects (median SUV-max 3.94 vs. 1.95; p = 0.005). Conclusions: ¹⁸F-FDG-PET/CT scan may differentiate normal thyroid parenchyma from the diffused inflammatory changes of the thyroid gland in patients with AITDs. However, the researchers must be continued.

18F-FDG PET/CT imaging of atypical subacute thyroiditis in thyrotoxicosis: A case report

BACKGROUND

In addition to its established role in oncologic imaging, F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) is useful for the assessment of inflammatory activity. However, subacute thyroiditis (SAT) in thyrotoxicosis is rarely detected during these scans.

CASE

A 66-year-old man with SAT in thyrotoxicosis demonstrated symptoms of transient fatigue, headache, and fever, without typical neck pain. Using F-FDG PET/CT, we found increased F-FDG uptake in the thyroid gland, predominantly in the right side due to SAT. We also observed a coexisting decrease in F-FDG uptake in the liver and increased F-FDG uptake in skeletal muscle due to thyrotoxicosis.

CONCLUSION

Using F-FDG PET/CT, the combined observations of increased F-FDG uptake in the thyroid and skeletal muscle, and decreased F-FDG uptake in the liver, even when the typical symptom of neck pain is subtle or absent, may be helpful for the differential diagnosis of SAT in thyrotoxicosis.

The use of (18)F-FDG-PET/CT for diagnosis and treatment monitoring of inflammatory and infectious diseases

FDG-PET, combined with CT, is nowadays getting more and more relevant for the diagnosis of several infectious and inflammatory diseases and particularly for therapy monitoring. Thus, this paper gives special attention to the role of FDG-PET/CT in the diagnosis and therapy monitoring of infectious and inflammatory diseases. Enough evidence in the literature already exists about the usefulness of FDG-PET/CT in the diagnosis, management, and followup of patients with sarcoidosis, spondylodiscitis, and vasculitis. For other diseases, such as inflammatory bowel diseases, rheumatoid arthritis, autoimmune pancreatitis, and fungal infections, hard evidence is lacking, but studies also point out that FDG-PET/CT could be useful. It is of invaluable importance to have large prospective multicenter studies in this field to provide clear answers, not only for the status of nuclear medicine in general but also to reduce high costs of treatment.

Subacute thyroiditis presenting as a focal lesion on [18F] fluorodeoxyglucose whole-body positron-emission tomography/CT

A 52-year-old man presented with subacute thyroiditis and showed an intensely hypermetabolic thyroid lesion on (18)F-FDG PET/CT. The patient also had coexisting chronic lymphocytic thyroiditis. The lesion of subacute thyroiditis revealed an SUV(max) of 9.1 g/mL and was ill-defined, heterogeneous, markedly hypoechoic, and hypovascular on US. Biopsy demonstrated histologic findings of subacute thyroiditis, which should be included in the differential diagnosis of an intensely hypermetabolic thyroid lesion on (18)F-FDG PET/CT.