Factors associated with fluorine-18-fluorodeoxyglucose uptake in benign thyroid nodules

Utility of PET/Computed Tomography in Infection and Inflammation Imaging

The role of nuclear medicine for noninvasive assessment of infection and inflammation is well established. The role of nuclear medicine is limited to initial diagnosis, recurrence, and response assessment of infections and inflammations such as tuberculosis, sarcoidosis, vasculitis, osteomyelitis, immunoglobulin G4-related diseases, and coronavirus disease 2019, as the specificity is affected by false positivity due to physiologic fluorodeoxyglucose uptake in specific organ and nonspecific uptake in postoperative cases. PET with fludeoxyglucose F 18/CT is a well-established modality for diagnosis of fever of unknown origin helping in optimized management of the patient.

Computer-Aided Diagnostic Technique in 2-Deoxy-2-[18F]fluoro-D-glucose-Positive Thyroid Nodule: Clinical Experience of 74 Non-thyroid Cancer Patients

This study verified the value of a computer-aided diagnosis (CAD) technique assisting in ultrasonography (US) diagnosis of 2-deoxy-2-[¹⁸F]fluoro-D-glucose (¹⁸FDG)-avid thyroid incidentalomas on positron emission tomography. A total of 82 ¹⁸FDG-avid thyroid incidentalomas from 74 non-thyroid cancer patients were retrospectively analyzed with respect to US and CAD parameters (anechoic area, hyper-echoic foci, hypo-echogenicity, heterogeneity, margin, taller-than-wide shape, eccentric area) and were compared with 38 other non-¹⁸FDG-avid nodules found in the same patient group. Fine-needle aspiration cytology or surgical intervention pathology was performed for diagnosis. No significant differences in nodule size or CAD parameters were found in ¹⁸FDG-avid nodules reported as benign, indeterminate or malignant. Significantly more taller-than-wide nodules were thyroid originating than metastatic (0.30 vs. 0.16, p < 0.05). Nevertheless, combined CAD and positron emission tomography/computed tomography scores and a discrimination point of 4 resulted in a sensitivity of 75% and a specificity of 80% in prediction of incidentaloma benignity.

FDG PET/CT in infection and inflammation--current and emerging clinical applications

Integrated positron emission tomography/computed tomography (PET/CT) with the glucose analogue, 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), is an evolving hybrid imaging technique in the evaluation of an important and diverse group of pathological conditions, which are characterised by infection and aseptic inflammation. With a rapidly expanding body of evidence, it is being increasingly recognised that, in addition to its established role in oncological imaging, FDG PET/CT also has clinical utility in suspected infection and inflammation. The technique can identify the source of infection or inflammation in a timely fashion ahead of morphological changes on conventional anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), map the extent and severity of disease, identify sites for tissue sampling, and assess therapy response. FDG PET/CT exhibits distinct advantages over traditional radionuclide imaging techniques in terms of shorter duration of examination, higher spatial resolution, non-invasive nature of acquisition, ability to perform quantitative analyses, and the provision of a synergistic combination of functional and anatomical imaging. With the use of illustrative clinico-radiological cases, this article discusses the current and emerging evidence for the use of FDG PET/CT in a broad spectrum of disorders, such as fever of unknown origin, sarcoidosis, large vessel vasculitis, musculoskeletal infections, joint prosthesis or implant-related complications, human immunodeficiency virus (HIV)-related infections, and miscellaneous indications, such as IgG4-related systemic disease. It will also briefly summarise the role of more novel tracers such as FDG-labelled leukocytes and gallium-68 PET tracers in this arena.

Thyroid lesions incidentally detected by (18)F-FDG PET-CT - a two centre retrospective study

Background.

Incidental ¹⁸F-FDG uptake in the thyroid on PET-CT examinations represents a diagnostic challenge. The maximal standardized uptake value (SUV_max) is one possible parameter that can help in distinguishing between benign and malignant thyroid PET lesions.

Patients and methods.

We retrospectively evaluated ¹⁸F-FDG PET-CT examinations of 5,911 patients performed at two different medical centres from 2010 to 2011. If pathologically increased activity was accidentally detected in the thyroid, the SUV_max of the thyroid lesion was calculated. Patients with incidental ¹⁸F-FDG uptake in the thyroid were instructed to visit a thyroidologist, who performed further investigation including fine needle aspiration cytology (FNAC) if needed. Lesions deemed suspicious after FNAC were referred for surgery.

Results.

Incidental ¹⁸F-FDG uptake in the thyroid was found in 3.89% — in 230 out of 5,911 patients investigated on PET-CT. Malignant thyroid lesions (represented with focal thyroid uptake) were detected in 10 of 66 patients (in 15.2%). In the first medical centre the SUV_max of 36 benign lesions was 5.6 ± 2.8 compared to 15.8 ± 9.2 of 5 malignant lesions (p < 0.001). In the second centre the SUV_max of 20 benign lesions was 3.7 ± 2.2 compared to 5.1 ± 2.3 of 5 malignant lesions (p = 0.217). All 29 further investigated diffuse thyroid lesions were benign.

Conclusions.

Incidental ¹⁸F-FDG uptake in the thyroid was found in 3.89% of patients who had a PET-CT examination. Only focal thyroid uptake represented a malignant lesion in our study — in 15.2% of all focal thyroid lesions. SUV_max should only serve as one of several parameters that alert the clinician on the possibility of thyroid malignancy.