Parametric Imaging of Biologic Activity of Atherosclerosis Using Dynamic Whole-Body Positron Emission Tomography

Abstract

BackgroundFor molecular imaging of atherosclerotic vessel wall activity, tracer kinetic analysis may yield improved contrast versus blood, more robust quantitative parameters, and more reliable characterization of systems biology. ObjectivesThe authors introduce a novel dynamic whole-body positron emission tomography (PET) protocol that is enabled by rapid continuous camera table motion, followed by reconstruction of parametric data sets using voxel-based Patlak graphical analysis. MethodsTwenty-five subjects were prospectively enrolled and underwent dynamic PET up to 90 minutes after injection of 2-[18F]fluoro-2-deoxy-D-glucose (FDG). Two sets of images were generated: 1) the established standard of static standardized uptake value (SUV) images; and 2) parametric images of the metabolic rate of FDG (MRFDG) using the Patlak plot–derived influx rate. Arterial wall signal was measured and compared using the volume-of-interest technique, and its association with hematopoietic and lymphoid organ signal and atherosclerotic risk factors was explored. ResultsParametric MRFDG images provided excellent arterial wall visualization, with elimination of blood-pool activity, and enhanced focus detectability and reader confidence. Target-to-background ratio (TBR) from MRFDG images was significantly higher compared with SUV images (2.6 ± 0.8 vs 1.4 ± 0.2; P < 0.0001), confirming improved arterial wall contrast. On MRFDG images, arterial wall signal showed improved correlation with hematopoietic and lymphoid organ activity (spleen P = 0.0009; lymph nodes P = 0.0055; and bone marrow P = 0.0202) and increased with the number of atherosclerotic risk factors (r = 0.49; P = 0.0138), where signal from SUV images (SUVmaxP = 0.9754; TBRmaxP = 0.8760) did not. ConclusionsAbsolute quantification of MRFDG is feasible for arterial wall using dynamic whole-body PET imaging. Parametric images provide superior arterial wall contrast, and they might be better suited to explore the relationship between arterial wall activity, systemic organ networks, and cardiovascular risk. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of arterial wall disease.