Molecular Imaging of Fibroblast Activation Protein on PET/MRI: Association With Carotid-Ulcerated Plaques and...

Increased expression of fibroblast activation protein (FAP) is associated with coronary atherosclerotic plaques. However, the association of FAP with carotid plaques remains unknown.

The objective of this was study was to assess the prevalence, distribution, and intensity of FAP uptake, and its association with carotid ulcerated plaque detected by digital subtraction angiography (DSA) and cerebrovascular risk factors.

A total of 52 atherosclerotic patients (82 plaques) with significant stenosis in the carotid artery who underwent both ⁶⁸Ga-FAPI-04 positron emission tomography/magnetic resonance imaging and DSA within 1 week were prospectively enrolled. Correlations between the fibroblast activation protein inhibitor (FAPI) uptake in carotid plaques and ulcerated plaque detected by DSA were assessed. Risk factors for ulcerative plaque were assessed by multivariate logistical regression, and the predictive value of ulcerative plaque was analyzed. Furthermore, an analysis was conducted on the association between FAPI uptake in plaques and severe stenosis, and cerebrovascular risk factors.

High focal plaque FAPI uptake was recorded in 35 of 82 plaques, of which 18 were carotid ulcerative plaques. The FAPI uptake, focal maximum standardized uptake value, and FAPI-derived target-to-background ratio (TBR) were significantly greater in ulcerated plaques than in nonulcerated plaques (all P < 0.001). In the multivariate analysis, the FAPI+ uptake (P = 0.002) and FAPI-derived TBR (P < 0.001) independently predicted ulcerated plaques. Among the cerebrovascular risk factors, the FAPI-derived TBR was significantly associated with older age and past cerebrovascular events (P < 0.001). In per patient analysis, the focal maximum standardized uptake value (P = 0.004) and FAPI-derived TBR (P = 0.001) were greater in higher-risk patients than in lower-risk patients.

⁶⁸Ga-FAPI-04 positron emission tomography/magnetic resonance imaging identifies FAPI uptake and is associated with ulcerated plaques. FAPI+ plaques are also associated with cerebrovascular risk factors.