Multiparametric Cardiac 18F-FDG PET: Pilot Comparison of FDG Delivery Rate with 82Rb Myocardial Blood Flow

TL;DR

This study investigates the use of 18F-FDG PET imaging to measure myocardial blood flow, comparing it with the standard 82Rb PET method, and finds promising correlations after glucose normalization, indicating potential for combined metabolic and perfusion imaging.

Contribution

The paper demonstrates that dynamic 18F-FDG PET, with kinetic modeling and glucose normalization, can reliably estimate myocardial blood flow, offering an alternative to traditional perfusion tracers.

Findings

Moderate correlation (r=0.79) between FDG K1 and Rb MBF before normalization.

Improved correlation (r>0.9) after blood glucose normalization.

FDG extraction fraction similar to Rb-chloride in myocardium.

Abstract

Myocardial blood flow (MBF) and flow reserve are usually quantified in the clinic with positron emission tomography (PET) using a perfusion-specific radiotracer (e.g. 82Rbchloride). However, the clinical accessibility of existing perfusion tracers remains limited. Meanwhile, 18F-fluorodeoxyglucose (FDG) is a commonly used radiotracer for PET metabolic imaging without similar limitations. In this paper, we explore the potential of 18F-FDG for myocardial perfusion imaging by comparing the myocardial FDG delivery rate K1 with MBF as determined by dynamic 82Rb PET in fourteen human subjects with heart disease. Two sets of FDG K1 were derived from one-hour dynamic FDG scans. One was the original FDG K1 estimates and the other was the corresponding K1 values that were linearly normalized for blood glucose levels. A generalized Renkin-Crone model was used to fit FDG K1 with Rb MBF, which then allowed for a nonlinear extraction fraction correction for converting FDG K1 to MBF. The linear correlation between FDG-derived MBF and Rb MBF was moderate (r=0.79) before the glucose normalization and became much improved (r>0.9) after glucose normalization. The extraction fraction of FDG was also similar to that of Rb-chloride in the myocardium. The results from this pilot study suggest that dynamic cardiac FDG-PET with tracer kinetic modeling has the potential to provide MBF in addition to its conventional use for metabolic imaging.