Measurement of ⁶⁸Ga-DOTATOC Uptake in the Thoracic Aorta and Its Correlation with Cardiovascular Risk

⁶⁸Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-d-Phe¹-Tyr³-octreotide (⁶⁸Ga-DOTATOC) is taken up by activated macrophages, which accumulate in active inflammatory lesions. The purpose of this study was to investigate the feasibility of ⁶⁸Ga-DOTATOC PET/CT for assessment of vulnerable plaque, by evaluating correlation between aortic uptake of ⁶⁸Ga-DOTATOC and cardiovascular risk factors.

Fifty patients with neuroendocrine tumors who underwent ⁶⁸Ga-DOTATOC PET/CT were retrospectively enrolled. The uptakes in the thoracic aorta were measured by two methods: multi-sample region-of-interest (ROI) method and single volume-of-interest (VOI) method. TBR_max-avg, TBR_mean-avg, TBR_max-VOI, and TBR_mean-VOI were defined by maximum and mean target-to-background ratio (TBR) from the multi-sample ROI method and the single VOI method, respectively.

Framingham risk score (FRS) exhibited significant correlations with TBR_max-avg and TBR_mean-avg, as well as TBR_max-VOI (r = 0.3389-0.4593, P < 0.05 for all). TBR_max-avg and TBR_max-VOI were significantly higher in high FRS group than in low FRS group (1.48 ± 0.21 vs. 1.70 ± 0.17, P < 0.001 for TBR_max-avg and 1.90 ± 0.33 vs. 2.25 ± 0.36, P = 0.002 for TBR_max-VOI). TBR exhibited high correlations between the two measuring methods (r = 0.9684, P < 0.001 for TBR_mean-avg and TBR_mean-VOI and r = 0.8681, P < 0.001 for TBR_max-avg and TBR_max-VOI).

⁶⁸Ga-DOTATOC uptake in the thoracic aorta exhibited a significant correlation with cardiovascular risk factors, which suggests the feasibility of ⁶⁸Ga-DOTATOC PET for vulnerable plaque imaging, with a simple measurement of the single VOI method that is comparable to the multi-sample ROI-based approach.