[18F] FDG uptake: pay attention to candies

Area of Science:

• Nuclear Medicine
• Oncology
• Radiochemistry

Background:

• [18F]Fluorodeoxyglucose ([18F]FDG) is a radiotracer used in Positron Emission Tomography (PET) imaging, mimicking glucose metabolism.
• Optimal [18F]FDG PET/CT imaging necessitates a fasting state (≥6 hours) to minimize physiological uptake variations and ensure accurate assessment of pathological processes.
• Contradictory findings exist regarding the impact of glucose levels on [18F]FDG uptake in lymphomatous tissues, prompting further investigation.

Purpose of the Study:

• To investigate the critical role of a euglycemic state and adequate fasting prior to [18F]FDG administration in lymphoma patients.
• To evaluate the impact of fasting on the diagnostic accuracy of [18F]FDG PET/CT in lymphoma staging and chemotherapy response assessment.
• To highlight potential pitfalls in interpreting [18F]FDG PET/CT scans due to non-compliance with fasting protocols.

Main Methods:

• Retrospective analysis of two lymphoma cases undergoing [18F]FDG PET/CT for chemotherapy response evaluation.
• Initial [18F]FDG PET/CT scans were performed without strict adherence to fasting guidelines, followed by repeat scans after ensuring a minimum six-hour fasting period.
• Comparison of imaging findings, focusing on [18F]FDG uptake patterns in neoplastic lesions and muscles before and after fasting.

Main Results:

• Initial [18F]FDG PET/CT scans in both cases were negative for neoplastic lesions but demonstrated increased, diffuse muscle uptake, potentially mimicking pathological findings.
• Subsequent [18F]FDG PET/CT scans, performed after a confirmed fasting period of at least six hours, revealed characteristic pathological uptake in lymphomatous lesions.
• The findings underscore that muscle uptake can obscure or be misinterpreted in the context of inadequate fasting, impacting diagnostic accuracy.

Conclusions:

• A fasting period of at least six hours is essential before [18F]FDG administration for accurate [18F]FDG PET/CT imaging in lymphoma.
• Maintaining a euglycemic state is critical for reliable assessment of tumor glucose metabolism and chemotherapy response in lymphoma.
• Clinicians must emphasize and verify fasting compliance to avoid misinterpretation of [18F]FDG PET/CT scans and ensure optimal patient management.