This proof-of-concept study is described as the first clinical PCCT study to characterize high-risk human carotid plaque features in living patients, using histology from subsequent carotid endarterectomy as the reference. The cohort comprised 10 symptomatic patients.
Spectral PCCT could differentiate multiple plaque components. Calcification was distinguishable from all other features across 40–190 keV, while intraplaque haemorrhage (IPH) was also distinguishable from the other tissue classes except thrombus. Thrombus was distinguishable from other features (except IPH) over 40–166 keV.
The key clinical implication is that PCCT may move carotid CTA beyond assessment of stenosis and calcification toward non-invasive characterization of rupture-prone plaque components, particularly IPH and thrombus, potentially improving cardiovascular risk stratification.
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Figure 1. Comparison of attenuation of distinct atherosclerotic plaque features scanned by PCCT in living patients and corresponding microscopic images after carotid endarterectomy. High-resolution PCCT angiography demonstrates carotid stenosis, with matched ROIs on 70-keV PCCT images and histology. Spectral HU measurements from 40–190 keV characterize calcium, IPH, thrombus, lipid core, fibrosis, and necrosis and demonstrate feature-specific spectral behavior.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Scan area | Carotid arteries |
Reference standard | Histology after carotid endarterectomy |
Timing | PCCT mean 1.7 ± 1.6 days before surgery |
Acquisition mode | Quantum Plus Single-source |
Tube voltage [kVp] | 120 |
Image quality level | 150 |
Exposure control | CARE Dose4D |
Collimation | 120 × 0.2 mm |
Rotation time | 0.5 s |
Pitch | 0.85 |
Contrast reconstruction | Qr40 and Bv64, QIR 4 |
Non-contrast reconstruction | Qr40 and Br84, QIR 3 |
Slice thickness | 0.4 mm |
Increment | 0.2 mm |
Spectral analysis | 40–190 keV in 1-keV increments |
Representative VMI | 70 keV |
Contrast | Omnipaque, 350 mg I/mL |
Plaque characterization
Feature | Histological reference / n | PCCT finding |
|---|
Calcification | von Kossa / 340 | Distinguished from all other features across 40–190 keV |
IPH | Glycophorin A / 106 | Distinguished from all features except thrombus |
Thrombus | Glycophorin A / 43 | Distinguished from other features except IPH at 40–166 keV |
Lipid core | oxLDL / 107 | Differentiated from fibrosis across all energies |
Fibrosis | Russell-Movat / 470 | Differentiated from lipid core throughout spectral range and necrosis at lower energies |
Necrosis | Histological tissue/cell absence / 62 | Spectral differentiation more limited |
The study used 1,128 manually matched histology-PCCT ROIs, with alignment validated by an experienced imaging cardiologist; blinded inter-observer assessment showed 82% overall agreement.
Key takeaway
PCCT provided in-vivo spectral tissue characterization of carotid plaques, including detection of intraplaque haemorrhage and thrombus, rather than merely quantifying stenosis or calcium. However, this remains an early proof-of-concept: only 10 patients were included, all were of the same sex and ethnicity, and there was no direct accuracy comparison with conventional CT or MRI.
Source: Shami A, Sun J, Celander M, et al. Clinical photon-counting computed tomography in living patients detects intra-plaque haemorrhage and thrombus in carotid plaques. European Heart Journal. 2025;46(46):5045–5048. Published August 29, 2025. doi:10.1093/eurheartj/ehaf707.
