Ultra-high-resolution (UHR) coronary CTA with photon-counting CT was feasible in patients with a high coronary calcium burden, providing improved visualization of calcified plaques and adjacent coronary lumen compared with conventional 0.6 mm reconstructions.
Reconstruction kernel selection proved critical. Moderate sharp kernels (particularly Bv64) achieved the best balance between blooming reduction, vessel sharpness, and image noise, while very sharp kernels increased noise without further improving blooming.
The study established an optimized UHR coronary PCCT protocol (0.2 mm slices, Bv64 kernel, 200 mm FOV, 512×512 matrix), laying the technical foundation for later clinical UHR coronary PCCT studies.
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Figure 5. Axial images from ultra-high-resolution CCTA (slice thickness, 0.2 mm) with PCD-CT of the left main and the proximal left anterior descending artery. Although borders of calcified plaques have a blurry appearance on reconstructions with low kernel strengths, reconstructions with moderate kernel strengths (eg, Bv64) enable an excellent delineation of calcified plaques and adjacent vessel lumen before increased image noise on reconstructions with high kernel strengths (eg, Bv89) hampers vessel lumen visualization.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Software | syngo CT VA50 |
Scan area | Coronary CTA |
Scan mode | Retrospective ECG-gated dual-source spiral UHR mode |
Acquisition mode | Quantum HD |
Scan direction | Helical |
Tube voltage [kV] | 120 |
Effective mAs [mAs] | IQ level 64 (automatic tube current modulation) |
IQ level | 64 |
Dose modulation | Automatic tube current modulation |
CTDIvol [mGy] | 38.2 ± 11.1 |
DLP [mGy·cm] | n.a. |
Temporal resolution [ms] | 66 |
Rotation time [s] | 0.25 |
Pitch | 0.19–0.32 (heart rate dependent) |
Matrix | 512 × 512 or 1024 × 1024 |
Field of view [mm] | 200 × 200 (Bv40–72), 150 × 150 (Bv89) |
Slice collimation [mm] | 120 × 0.2 |
Slice width [mm] | 0.2 (reference reconstruction additionally 0.6 mm) |
Reconstruction increment [mm] | 0.2 (0.3 mm for reference reconstruction) |
Reconstruction kernel | Bv40, Bv44, Bv56, Bv60, Bv64, Bv72, Bv80, Bv89 |
Iterative reconstruction | QIR level 4 |
Reconstruction comparison | Eight UHR vascular kernels (0.2 mm) versus reference Bv40 at 0.6 mm |
ECG gating | Retrospective |
ECG pulsing | Fixed 30–80% R-R interval |
Contrast agent | Ultravist 370 (iopromide 370 mg iodine/mL) |
Contrast volume | 50–80 mL (body weight dependent) |
Flow rate | 3.3–4.4 mL/s |
Saline chaser | 20 mL |
Bolus triggering | 140 HU in ascending aorta at 90 kV |
Patient preparation | Sublingual nitroglycerin (2.5 mg isosorbide dinitrate); no beta-blockers |
Phase selection | Least-motion cardiac phase reconstructed individually |
Key Results
Parameter | Main finding |
|---|
Feasibility | UHR coronary PCCT successful in all 20 patients |
Median calcium score | 479 |
Best reconstruction kernel | Bv64 |
Lowest blooming | Bv72 (39.7%) |
Highest vessel sharpness | Bv89 (2383 ΔHU/mm) |
Best plaque/lumen delineation | Bv64–Bv72 |
Reference reconstruction | Bv40, 0.6 mm showed highest SNR/CNR but greatest blooming |
Recommended protocol | Bv64, 0.2 mm slices, 200 mm FOV, 512×512 matrix |
Source: Mergen V, Sartoretti TB, Baer-Beck M, Schmidt B, Petersilka M, Wildberger JE, Euler A, Eberhard M, Alkadhi H. Ultra-High-Resolution Coronary CT Angiography With Photon-Counting Detector CT: Feasibility and Image Characterization. Investigative Radiology. 2022;57(12):780-788. doi:10.1097/RLI.0000000000000897.
