Fever of Unknown Origin: The Roles of FDG PET or PET/CT

Drinking Large Volume of Hot Water May Cause Increased 18 F-FDG Uptake in Esophagus

ABSTRACT

We present 2 cases of diffuse FDG accumulation in the esophagus due to drinking hot water before an 18 F-FDG PET/CT scan. Drinking large volume of hot water immediately before the FDG PET/CT study may lead to challenges in the interpretation of the hypermetabolic esophagus.

Quantifying the contribution of 18F-FDG PET to the diagnostic assessment of pediatric patients with fever of unknown origin: a systematic review and meta-analysis

BACKGROUND

The value of ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) in the diagnostic assessment of pediatric fever of unknown origin is not known, and evidence from adults is not applicable.

OBJECTIVE

To quantify the contribution of ¹⁸F-FDG PET to pediatric fever of unknown origin, considering its diagnostic limitations.

MATERIALS AND METHODS

We searched PubMed, EMBASE and Cochrane Central Register of Controlled Trials up to Feb. 18, 2021. We included studies on patients with pediatric fever of unknown origin presenting sufficient data to calculate the likelihood of achieving definite diagnosis (based on pathology or clinical follow-up) between those with abnormal PET findings versus those with normal PET findings. We assessed the risk of bias using a modified Newcastle-Ottawa quality assessment scale and quantified the value of PET by pooling the likelihood of achieving definite diagnosis using a random-effects model.

RESULTS

We included 6 studies and found that pediatric patients with abnormal PET findings were about 17 times more likely to achieve definite diagnoses than those with normal PET findings (odds ratio [OR]: 16.75, 95% confidence interval [CI] 8.0-35, P < 0.00001). Sensitivity analyses using a fixed-effect model (OR 16.91, 95% CI 8.1-35, P < 0.0001) or removing one study at a time (OR 12-20, 95% CI lower bound 3.8-8.6, 95% CI upper bound 33-45, P < 0.0001) did not significantly alter the results. Sample size (interaction P = 0.75), imaging modality (interaction P = 0.29), length of follow-up (interaction P = 0.37), fever of unknown origin subclasses (interaction P = 0.89) and geographical areas (interaction P = 0.74) of studies showed no statistically significant influence on the results.

CONCLUSION

¹⁸F-FDG PET is a promising approach in the diagnostic work-up of pediatric fever of unknown origin. Further studies are warranted to support routine use in clinical care.

Focal FDG Uptake in the Cerebral Parenchyma Beneath the Subdural Hematoma

ABSTRACT

Changes in cerebral glucose metabolism after subdural hematoma have been rarely reported. We present a case with acute subdural hematoma detected unexpectedly on FDG PET/CT. Focal intense FDG uptake in the cerebral parenchyma beneath the subdural hematoma was seen on PET. The density of the cerebral parenchyma was normal on CT. The patient received conservative management. He recovered without any complication. This case indicates that familiarity with the changes in cerebral glucose metabolism on PET after subdural hematoma may be helpful for optimal patient care.

PET/Computed Tomography in the Evaluation of Fever of Unknown Origin and Infectious/Inflammatory Disease in Pediatric Patients

Fever in children is common. If it persists and its cause cannot be identified in a reasonable time, along with laboratory and conventional imaging investigations, it is defined as fever of unknown origin (FUO). 18F-fluorodeoxyglucose (FDG) PET/computed tomography (CT) is well established in the evaluation of malignancy, which is a possible cause of FUO. FDG often locates inflammatory and infectious lesions considered nonspecific or false-positive for oncology; however, these findings are beneficial in FUO evaluation because infectious and inflammatory diseases are important FUO causes. FDG-PET/CT is being increasingly used for investigation of FUO as well as infectious/inflammatory disease.

Preparation and Logistic Considerations in Performing PET and PET/Computed Tomography in Pediatric Patients

It is good for the nuclear medicine technologist to be aware of the normal variants and the appearance of a good-quality scan. The primary responsibility as a nuclear medicine technologist is to provide an optimal quality scan that maximizes the reading physician's ability to correctly interpret while using current radiation safety practices as the best possible experience is created for patients and families. Combining the radiation safety aspects (nuclear) with how care is provided (medicine) and the use of the most recent equipment (technology) is what defines a nuclear medicine technologist.

Is There Any Potential of FDG PET/CT in Monitoring Disease Activity in Familial Hemophagocytic Lymphohistiocytosis?

FDG PET/CT was performed in a 30-year-old woman to detect the source of fever of unknown origin. The images showed widespread abnormal activity, consistent with lymphoma. However, lymph node biopsy revealed only inflammation, and a diagnosis of familial hemophagocytic lymphohistiocytosis was eventually made after familial hemophagocytic lymphohistiocytosis-specific gene was detected. After proper therapy, a follow-up FDG PET/CT examination 2 months later showed resolution of most of the previously seen lesions.