Page 61 - ARNM-3-2

Advances in Radiotherapy
& Nuclear Medicine 18 F-FDG uptake and hypercholesterolemia

ASCVD begins with histologic changes within the aorta and iliac arteries (as assessed by CT imaging) and
arterial wall, driven by inflammation and other factors. inflammatory activities (quantified by 18F-FDG uptake
Consequently, the permeability of endothelial cells layer using a standard compartmental modeling approach)
increases, resulting in lipid accumulation and infiltration in hypercholesterolemic patients. This aim extends to
of inflammatory cells within the arterial wall, leading to examining the relationship between calcium burden,
the formation of atherosclerotic plaque. 7 cholesterol burden, and inflammatory response – as
These lesions are progressive and may advance to cause defined by the metabolic rate of glucose (MRGlu) – and
a significant limitation or obstruction of blood flow, in whether the calcium burden in hypercholesterolemic
addition to artery-to-artery thromboembolism. ASCVD patients differs from that in individuals with normal lipid
8
presents in varying degrees of complexity, ranging from levels or stable angina (SA), based on MRGlu values.
stable to acute clinical events, and about 50% of ASCVD 2. Materials and methods
9
patients who die suddenly have no prior warning signs. 3
Eighteen participants scheduled for 18 F-FDG CT/
Several known factors contribute to atherosclerosis
and its downstream sequelae leading to acute clinical PET examination were prospectively enrolled in this
study. The inclusion criteria comprised individuals with
events. Among these, hypercholesterolemia is a key hypercholesterolemia, SA, and healthy controls who
factor. Hypercholesterolemia has been found to induce consented to participate. Classification was based on
10
atherosclerosis in both human and experimental animals clinical examination, including the absence of clinical
through several atherogenic processes, 10,11 and is considered
a major cause of the initiation and progression of ASCVD, signs and symptoms, and normal blood pressure, glucose,
increasing the risk of ASCVD up to five-fold. 12 and lipid profile.
Common risk stratification models for ASCVD Exclusion criteria included oncology patients and
25
in patients with hypercholesterolemia include glucose levels >7 mmol/L. Measurements of glucose,
the cholesterol-year score, the Spanish Familial total cholesterol (TC), high-density lipoprotein cholesterol
13
Hypercholesterolemia Cohort Study, and the French (HDL-C), low-density lipoprotein cholesterol (LDL-C),
14
Familial Hypercholesterolemia Registry. However, triglyceride (TG), and C-reactive protein (CRP) were
15
these models lack consideration of calcium burden in obtained from all participants after overnight fasting.
hypercholesterolemic patients. Atherosclerosis imaging Low-dose unenhanced CT images were acquired
techniques allow for a more accurate analysis of the immediately before the PET acquisition using a PET/CT
pathological processes and plaque characteristics, which scanner (Philips Medical Systems, Netherlands) and were
may refine ASCVD risk assessment. used for attenuation and scatter correction, anatomic
Computed tomography (CT) is a very frequently localization, and calcium burden. Dynamic PET images
used imaging modality to assess calcium burden in were acquired over 30 min immediately following a bolus
18
ASCVD. Although the role of calcium burden is debated intravenous injection of F-FDG radiopharmaceutical
16
– considered a marker of vulnerable plaque in some agent (Sherbrooke Molecular Imaging Center [CIMS],
studies, 17,18 while others associate plaque calcification with CIUSSS de l’Estrie - Centre Hospitalier Universitaire
plaque stability and an inverse relationship with ASCVD de Sherbrooke, Canada). PET and CT images were
risk 19,20 – it remains an important parameter. reconstructed using a Philips Gemini TF 16 PET/CT
scanner (Philips Medical Systems, Netherlands), equipped
18
18 F-Fluorodeoxyglucose ( F-FDG) positron emission with time-of-flight capability. The injected activity of F-
18
tomography/CT (PET/CT) has proven to be a powerful FDG ranged from 220 to 350 MBq, normalized to the
molecular imaging modality for analyzing inflammatory participant’s weight. PET data were reconstructed using
activity in atherosclerotic plaques, providing accurate the iterative 3D row action maximum likelihood algorithm
information on vascular metabolic activity. 16,18,21,22 into 26 frames (12 × 2 min, 8 frames × 4 min, and 6
The extent and density of aortic calcification have frames × 24 min). CT and PET voxel dimensions were 1
3
3
been shown to correlate with increased atherosclerotic × 1 × 4 mm and 4 × 4 × 4 mm , respectively.
inflammatory activity, as measured by F-FDG uptake. 22,23 Regions of interest (ROIs) for arteries were segmented
18
In addition, calcium burden on CT and F-FDG uptake semi-automatically from CT images using an edge-based
18
on PET have been correlated in the abdominal aorta and active contour model to delineate the optimal object
iliac arteries. 16,24 boundary. Each ROI was validated using the colocalized
26
Thus, the aim of this study is to explore the association ROI on the corresponding PET slice – identified using
between calcium burden in the arterial walls of the Digital Imaging and Communications in Medicine header
Volume 3 Issue 2 (2025) 53 doi: 10.36922/arnm.8540