Key result
Symptomatic carotid plaques show ~23% higher 11C-PK11195 uptake on PET/CTA than asymptomatic plaques.
Why the study?
The ability to measure intraplaque inflammation in carotid atherosclerosis using 11C-PK11195 PET/CTA and its relation to symptomatic plaques was investigated.
Can 11C-PK11195 PET/CTA imaging distinguish between symptomatic and asymptomatic carotid plaques in patients with carotid stenoses?
Cross-Sectional (n=32)
Can 11C-PK11195 PET/CTA imaging distinguish between symptomatic and asymptomatic carotid plaques in patients with carotid stenoses?
Absolute Event Rate: 1.06% vs 0.86%
p-value: p=0.001
11C-PK11195 PET/CTA imaging is feasible for in vivo assessment of intraplaque inflammation and can distinguish between recently symptomatic and asymptomatic carotid plaques.
11C-PK11195 PET/CTA may identify inflamed symptomatic carotid plaques; leaves open clinical utility pending prospective validation.
AIMS: We sought to determine whether intraplaque inflammation could be measured with positron emission tomography/computed tomography angiography (PET/CTA) using (11)C-PK11195, a selective ligand of the translocator protein (18 kDa) (TSPO) which is highly expressed by activated macrophages. METHODS AND RESULTS: Patients (n = 32; mean age 70 ± 9 years) with carotid stenoses (n = 36; 9 symptomatic and 27 asymptomatic) underwent (11)C-PK11195 PET/CTA imaging. (11)C-PK11195 uptake into carotid plaques was measured using target-to-background ratios (TBR). On CTA images, plaque composition was assessed by measuring CT attenuation of the carotid plaque. Eight patients underwent carotid endarterectomy and ultrathin contiguous sections were processed for TSPO and CD68 (using immunohistochemical staining, (3)H-PK11195 autoradiography, and confocal fluorescence microscopy). Carotid plaques associated with ipsilateral symptoms (stroke or transient ischaemic attack) had higher TBR (1.06 ± 0.20 vs. 0.86 ± 0.11, P = 0.001) and lower CT attenuation [(median, inter-quartile range) 37, 24-40 vs. 71, 56-125 HU, P = 0.01] than those without. On immunohistochemistry and confocal fluorescence microscopy, CD68 and PBR co-localized with (3)H-PK11195 uptake at autoradiography. There was a significant correlation between (11)C-PK11195 TBR and autoradiographic percentage-specific binding (r = 0.77, P = 0.025). Both TBR and CT plaque attenuation had high negative predictive values (91 and 92%, respectively) for detecting symptomatic patients. However, the best positive predictive value (100%) was achieved when TBR and CT attenuation were combined. CONCLUSION: Imaging intraplaque inflammation in vivo with (11)C-PK11195 PET/CTA is feasible and can distinguish between recently symptomatic and asymptomatic plaques. Patients with a recent ischaemic event had ipsilateral plaques with lower CT attenuation and increased (11)C-PK11195 uptake.
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Gaemperli et al. (2011) conducted a cross-sectional in Carotid stenoses (n=32). Symptomatic carotid plaques vs. Asymptomatic carotid plaques was evaluated on 11C-PK11195 uptake (target-to-background ratio) (p=0.001). Symptomatic carotid plaques had higher 11C-PK11195 uptake on PET/CTA compared to asymptomatic plaques (target-to-background ratio 1.06 vs. 0.86, P=0.001).
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