18F-FDG PET/CT for the quantification of inflammation in large carotid artery plaques

Figure 1. 18F-FDG PET/CT of stenotic plaque in the right internal carotid artery. From left to right: CT angiography, co-registered PET/CT, and 18F-FDG PET. The white box shows the plaque extension craniocaudally with lumen contrast-filling defect and vessel wall thickening on CT angiography (left image)

Figure 2. 18F-FDG uptake quantification was based on the SUVmax of all the plaque-containing axial PET slices (A): Max SUVmax = the single highest SUVmax (B), mean SUVmax = the mean of all plaque SUVmax (C), MDS3 = the mean SUVmax of the three contiguous slices centered on the slice with the highest SUVmax (D), MDS5 = the mean SUVmax of the five contiguous slices centered on the slice with the highest SUVmax (E), and mean SUVmax4 = the mean SUVmax of the four slices with highest SUVmax within the plaque(F) (based on a figure by Tawakol et al 32)

Figure 3. The histological quantification of inflammation was performed on H&E stained samples. The ocular micrometer was used to measure the total plaque area and area occupied by inflammatory cells in all the fields of view from all sections. The amount of inflammation per plaque was defined as the sum of all areas with inflammatory cells divided by the total area of all sections. A: ×200 magnification with inflammatory areas (marked by blue lines) containing mainly lymphocytes (i) and lipid macrophages (ii). B: ×400 magnification of areas with lipid macrophages

Figure 4. Plaque extension (gray bars) and max SUVmax location (black dots) per patient along the x-axis. The y-axis shows the distance in millimeter from the bifurcation (0) cranially in the internal carotid artery and caudally in the common carotid artery

Figure 5. Uncorrected 18F-FDG uptake values for individual patients sorted according to increasing mean SUVmax. Each color represents separate quantification methods. The black dots are the background values (mean SUVmean)

Figure 6. Uncorrected and background-corrected (TBR and cSUV) max and mean SUVmax per patient sorted according to increasing mean SUVmax

Figure 7. Scatter plots with correlation lines of total area with inflammatory cells versus uncorrected (A, B) and background-corrected (TBR: C, D and cSUV: E, F) max and mean SUVmax

Figure 8. Deviation from the mean SUVmax for different quantification methods for individual patients. The black bar represents the mean values