Standard PCCT virtual noncontrast (VNC) calcium scoring performs well for larger and denser plaques but can miss subtle disease. Large/medium and high/medium-density plaques showed strong agreement with true noncontrast (TNC) scoring (r > 0.9; ICC ≥ 0.90), whereas low-density plaques showed poor agreement and small plaques were not detectable with standard VNC reconstruction.
A dedicated “safety-net” reconstruction combining thinner 1.0-mm slices, a sharper Qr44 kernel, low monoenergetic energy and lower calcium thresholds markedly improved subtle-plaque detection. The best clinical setting was 55 keV, QIR 2, and a 110-HU threshold.
In 63 participants, standard VNC missed 56 plaques visible on TNC; the optimal safety-net reconstruction recovered 50/56 (89%). The approach may therefore be particularly valuable when standard VNC yields a calcium score of zero, potentially preventing false-negative risk classification while supporting elimination of a separate TNC scan.
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Figure 7: Example axial CT reconstructions of in vivo coronary artery calcium scoring (CACS) without and with calcium scoring overlay, comparing CACSTNC (left column: 70 keV, quantum iterative reconstruction [QIR] off) and CACSVNC (middle column: 55 keV, QIR 1, as previously recommended) (9) at standard CACS settings with CACSVNC at the proposed safety net reconstruction (right column: 55 keV, QIR 2). The upper row (participant 1) shows CT scans in a 90-year-old male, the middle row (participant 2) in a 62-year-old male, and the lower row (participant 3) in a 59-year-old female. The safety net reconstruction allowed improved detection of small and/or low-density in vivo plaques (arrowheads) that initially were detected in reference TNC scans but not in standard VNC reconstructions. LAD = left anterior descending artery, RCA = right coronary artery, TNC = true noncontrast, VNC = virtual noncontrast.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha, VA40 |
Scan area | Coronary arteries / cardiac CT |
Scan mode | QuantumPlus |
Tube voltage [kV] | 120 |
Rotation time [s] | 0.25 |
Detector slice collimation | 144 × 0.4 mm |
ECG gating | ECG-triggered |
Reference TNC reconstruction | 70 keV, QIR off |
Standard TNC slice thickness / increment [mm] | 3.0 / 1.5 |
Standard TNC kernel | Qr36 |
VNC reconstruction energies | 55–80 keV in 5-keV increments |
VNC iterative reconstruction | QIR 1–4 |
Standard VNC slice thickness | 3.0 mm |
Standard VNC kernel | Qr36 |
Safety-net slice thickness / increment [mm] | 1.0 / 1.0 |
Safety-net kernel | Qr44 |
Preferred safety-net reconstruction | 55 keV, QIR 2 |
Preferred calcium threshold | 110 HU |
Contrast agent | Iopromide 350 mg I/mL |
Contrast protocol | 50 mL contrast → 20 mL 50% contrast/saline → 25 mL saline |
Bolus triggering | Descending aorta, 150 HU |
Trigger delay | 8 s |
Patient preparation | 0.4 mg sublingual nitroglycerin; 5 mg oral metoprolol if HR >70 bpm |
Key Results
Parameter | Main finding |
|---|
Clinical cohort | 63 participants; mean age 57.8 ± 15.5 years |
Large/medium or denser plaques | VNC vs TNC: r > 0.9; ICC ≥ 0.90 |
Low-density plaques, standard VNC | Poor agreement: r = 0.5–0.6; ICC = 0.20–0.48 |
Small plaques, standard VNC | Not detectable |
Best safety-net reconstruction | 55 keV, QIR 2, Qr44, 1.0 mm, 110 HU |
Clinical plaque recovery | 50/56 (89%) previously missed plaques detected |
Source:
Fink N, Emrich T, Schoepf UJ, Zsarnoczay E, O’Doherty J, Halfmann MC, Griffith JP III, et al. Improved Detection of Small and Low-Density Plaques in Virtual Noncontrast Imaging–based Calcium Scoring at Photon-Counting Detector CT. Radiology: Cardiothoracic Imaging. 2024;6(4). doi:10.1148/ryct.230328.
