PET/CT imaging of unstable carotid plaque with 68Ga-labeled somatostatin receptor ligand

Wan, Ming Young Simon, Endozo, Raymond, Michopoulou, Sofia, Shortman, Robert, Rodriguez-Justo, Manuel, Menezes, Leon, Yusuf, Syed, Richards, Toby, Wild, Damian, Waser, Beatrice, Reubi, Jean Claude and Groves, Ashley (2017) PET/CT imaging of unstable carotid plaque with 68Ga-labeled somatostatin receptor ligand. Journal of Nuclear Medicine, 58 (5), 774-780. (doi:10.2967/jnumed.116.181438).

Abstract

⁶⁸Ga-labeled somatostatin receptor ligand PET imaging has recently been shown in preclinical and early human studies to have a potential role in the evaluation of vulnerable arterial plaques. We prospectively evaluated carotid plaque ⁶⁸Ga-DOTATATE uptake in patients with recent carotid events, assessed inter- and intraobserver variability of such measurements, and explored the mechanism of any plaque DOTATATE activity with immunohistochemistry in resected specimens.

Methods: twenty consecutively consenting patients with recent symptomatic carotid events (transient ischemic attack, stroke, or amaurosis fugax), due for carotid endarterectomy, were prospectively recruited. ⁶⁸Ga-DOTATATE PET/CT of the neck was performed before surgery. 68Ga-DOTATATE uptake was measured by drawing regions of interest along the carotid plaques and contralateral plaques/carotid arteries by an experienced radionuclide radiologist and radiographer. Two PET quantification methods with inter- and intraobserver variability were assessed. Resected carotid plaques were retrieved for somatostatin receptor subtype-2 (sst2) immunohistochemical staining.

Results: the median time delay between research PET and surgery was 2 d. SUVs and target-to-background ratios for the symptomatic plaques and the asymptomatic contralateral carotid arteries/plaques showed no significant difference (n = 19, P > 0.10), regardless of quantification method. The intraclass correlation coefficient was greater than 0.8 in all measures of carotid artery/plaque uptake (SUV) and greater than 0.6 in almost all measures of target-to-background ratio. None of the excised plaques was shown to contain cells (macrophages, lymphocytes, vessel-associated cells) expressing sst2 on their cell membrane.
Conclusion: ⁶⁸Ga-DOTATATE activity on PET in recently symptomatic carotid plaques is not significantly different fromcontralateral carotids/plaques. Any activity seen on PET is not shown to be from specific sst2 receptor-mediated uptake in vitro. It is therefore unlikely that sst2 PET/CT imaging will have a role in the detection and characterization of symptomatic carotid plaques.

This record has no associated files available for download.

Contributors

Download statistics