When to image carotid plaque inflammation with FDG PET/CT

Area of Science:

• Cardiovascular Imaging
• Nuclear Medicine
• Atherosclerosis Research

Background:

• Quantifying 18-fluorodeoxyglucose (FDG) uptake in carotid atherosclerotic plaques using positron emission tomography (PET) is challenging due to spatial resolution and blood activity.
• Late PET acquisition protocols improve plaque-to-blood contrast but are inconvenient for prospective studies.
• Retrospective studies often rely on early acquisition data, necessitating evaluation of quantification method changes.

Purpose of the Study:

• To assess the impact of early versus late PET scan timing on FDG uptake quantification in carotid artery plaques.
• To compare the consistency of SUVmax and Target-to-Background Ratio (TBR) methods across different acquisition times.

Main Methods:

• Compared FDG uptake at 1 and 3 hours post-injection in 19 carotid artery plaques.
• Evaluated plaque maximum standardized uptake value (SUVmax) and target-to-background ratio (TBR) using venous blood-pool activity.
• Assessed consistency and changes in quantification metrics between early and late scans.

Main Results:

• High consistency was observed for SUVmax between 1 and 3-hour scans (r²=0.86).
• The TBR method showed poor consistency between time points (r²=0.34).
• Absolute SUVmax values varied, while TBR generally increased as blood pool activity decreased.

Conclusions:

• Carotid plaque inflammation can be identified 1 hour after FDG injection.
• SUVmax is a reliable method for quantifying plaque FDG uptake at an early time point.
• Early PET acquisition using SUVmax offers a practical approach for assessing carotid plaque inflammation.