TSPO PET Imaging: From Microglial Activation to Peripheral Sterile Inflammatory Diseases?

Table 4

Applications	Population/animal models	Radioligand	Main findings	Ref.
Vasculitis
Clinical	(i) 15 patients with large vessel vasculitis (5 TA, 4 GCA, & 6 SLE); (ii) 1 GCA patient followed-up after 20-week course of oral CS	^11C-PK11195	(i) 3/5 patients whose tracer binding was found at the level of the aorta; maximal tracer uptake coincided with minimal calcification; Tracer TBR was significantly higher in symptomatic, compared to asymptomatic patients; (ii) Tracer uptake was markedly reduced in the wall of the aortic arch after CS treatment; The reduction in radioligand binding was paralleled by a distinct improvement in symptoms and a decrease in his serum inflammatory markers	Pugliese et al. (2010) [36]
Clinical	7 patients (3 symptomatic & 4 asymptomatic) with large vessel vasculitis	^11C-PK11195	was significantly greater in symptomatic than in asymptomatic patients	Lamare et al. (2010) [110]
Atherosclerosis
Preclinical	Constrictive cuff was placed on the right carotid artery of 6 mice	^18F-FEDAA1106	Significantly increased tracer binding in the right carotid artery compared to left (unmanipulated) carotid artery; TAC exhibited a significantly greater increase in binding at the downstream region when compared to the cuffed or upstream regions at 60 minutes after injection	Cuhlmann et al. (2014) [120]
Preclinical	10 atherosclerotic mice (LDLR^−/− ApoB^100/100) versus 9 healthy mice	^18F-FEMPA	There was visually detectable tracer uptake that colocalized with the aortic arch, but not significantly different between the animal groups; Radioligand SUV was significantly higher in atherosclerotic aortas in muted mice than in healthy control mice	Hellberg et al. (2017) [121]
Clinical	32 patients with carotid stenosis (9 symptomatic & 27 asymptomatic)	^11C-PK11195	Tracer SUV and TBR were higher in carotid plaques of symptomatic than asymptomatic patients; No significant correlation between radioligand TBR and plaque calcification; ROC analysis of tracer TBR to identity patients with CVE showed sensitivity of 78%, specificity of 74%, NPV of 91%, and PPV of 50%	Gaemperli et al. (2012) [122]

CS, corticosteroids; CVE, cerebrovascular events; GCA, giant cell arteritis; HC, healthy control; NPV, negative predictive value; PPV, positive predictive value; ROC, receiver operating characteristic; SLE, systemic lupus erythematosus; SUV, standardized uptake value; TA, Takayasu’s arteritis; TAC, time-activity curves; TBR, target-to-background ratio; , total volume of distribution.