Abstract 150: Arterial Calcification and Neural Metabolic Activity: Assessing Neurovascular Status Through FDG and NaF PET/CT Imaging
Authors: Subtirelu Robert C. , Teichner Eric M. , Su Yvonne , Werner Thomas , Høilund‐Carlsen Poul Flemming , Revheim Mona‐Elisabeth , Alavi Abass 
Published: March 2024

Introduction
Atherosclerosis, the occlusion of arteries due to the accumulation of fatty substances, cholesterol, calcium, and fibrin in the arterial walls, can result in reduced blood flow and a subsequent decrease in oxygen delivery to the organs supplied by the affected artery, including the brain. Positron emission tomography‐computed tomography (PET‐CT) utilizing 18F‐fluorodeoxyglucose (FDG) and 18F‐Sodium Fluoride (NaF) have demonstrated efficacy in the assessment of cerebral glucose metabolism and atherosclerotic calcification, respectively. However, the reported literature has not clearly correlated arterial disease throughout the body with cerebral hypometabolism. Utilizing a novel integration of FDG and NaF PET/CT imaging, our study explores the link between cardiovascular risk factors and regional cerebral metabolism.

Methods
We compared 79 healthy controls (mean age 44.5 ± 13.8 years, 53.2% males) and 40 individuals (mean age 55.9 ± 11.9 years, 50% males) at increased risk for cardiovascular disease (CVD) as assessed by the systematic coronary risk evaluation (SCORE) tool. All subjects underwent whole‐body FDG‐PET/CT imaging. [18F]fluoride PET/CT imaging was performed using hybrid PET/CT scanners with image correction and reconstruction processes following standard protocols. The quantitative regional analysis of PET images was performed using MIMneuro version 7.1.5 (MIM Software, Inc., Cleveland, Ohio). 70 whole brain structures were analyzed in each subject. MIMneuro provided region‐based analysis, with z‐scores generated by comparing the patient to the selected age‐matched set of normal controls. Using OsiriX MD software, [18F]fluoride PET/CT scans were analyzed with regions of interest (ROIs) manually drawn to assess carotid calcification and standardized uptake value mean (SUVmean), along with ROI volume values. Correlations between the degree of molecular calcification and cerebral FDG uptake in patients with cardiovascular risk factors were evaluated using Pearson’s R, with the significance threshold set at P < 0.05.

Results
Unhealthy patients demonstrated significant negative correlations between increased calcification in the carotid arteries, as assessed by NaF‐PET, and metabolic activity in the anterior cingulate (r = ‐0.42, p = 0.008) and cingulate regions (r = ‐0.34, p = 0.036). Conversely, healthy patients exhibited significant positive correlations in the pons (r = 0.25, p = 0.042) and pontine tegmentum (r = 0.34, p = 0.005), suggestive of a compensatory mechanism to maintain autonomic and motor functions.

Conclusion
The present study provides insight regarding the interplay between arterial calcification and neural metabolic activity, particularly as it pertains to regions supplied by the anterior cerebral artery. Our investigation suggests that calcification in the carotid arteries, which give rise to the ACA, has a deleterious impact on the function of the cingulate gyrus. Additionally, the observed positive correlation in the pons and pontine tegmentum in healthy individuals raises intriguing questions regarding potential compensatory mechanisms that may help maintain autonomic and motor functions despite vascular impediments. Understanding the temporal progression of vascular calcification allows for the optimization of surgical strategy and timing, potentially reducing stroke risk and improving patient outcomes. These findings underscore the necessity of persistent surveillance and targeted management strategies concerning carotid calcification.