Role of somatostatin receptor and FDG imaging in capturing plaque inflammation: a PET/CT analysis, corroborated by clinical data

Ziel/Aim:

Evidence indicates that atherosclerosis-related vascular inflammation can be measured with ¹⁸F-FDG-PET. However, background uptake, patients' comorbidities, and concomitant treatments may hamper signal semi-quantification. Up-regulation of somatostatin receptor subtype-2 occurs on activated macrophages and it has been suggested that somatostatin-receptor PET imaging may also capture vascular inflammation. This study aimed to compare the vascular distribution and biological determinants of plaque inflammation, as assessed by both ⁶⁸Ga-DOTATOC and ¹⁸F-FDG-PET.

Methodik/Methods:

27 patients (12 males, mean age 69.4 ± 8, range 56 – 87) underwent an ¹⁸F-FDG and a 68 Ga-DOTATOC-PET within a four-week period for clinical reasons. Cardiovascular-risk was stratified using a simplified version of the Framingham model. VOIs were drawn on the entire aorta in both the ¹⁸F-FDG and the 68-Ga DOTATOC PET/CT. In these VOIs, SUV_mean and SUV_max were normalized to blood activity to obtain the aortic target-to-background ratio (TBR_mean and TBRmax). Differences in mean values and linear regression analysis were tested for these values and cardiovascular risk factors.

Ergebnisse/Results:

Aortic TBRmax was significantly higher on ⁶⁸Ga-DOTATOC than on ¹⁸F-FDG-PET images (5.7 ± 2.2 Vs. 2 ± 1.2, p < 0.01) while no differences were highlighted for TBR_mean. Cardiovascular risk score correlated with both TBR_mean (R = 0.82 and 0.81 for ¹⁸F-FDG-PET and for ⁶⁸Ga-DOTATOC, respectively, p < 0.001). Finally, only TBRmax of ⁶⁸Ga-DOTATOC (and not of ¹⁸F-FDG) was higher in diabetics (n = 12) with respect to the remaining patients (6 ± 0.8 Vs. 4.9 ± 0.6, p < 0.05).

Schlussfolgerungen/Conclusions:

Correlations of both tracers uptake upon ongoing biological determinants of vascular inflammation confirm that PET might provide a window on plaque pathophysiology. In this framework, ⁶⁸Ga-DOTATOC vascular signal demonstrated to better capture the presence of arterial hot spots and was able to better highlight plaque inflammation in diabetic patients.