(2023) McCollough | PCCT reduces calcium blooming and visual coronary stenosis estimates

Daniel Stromer

Photon-counting detector (PCD) coronary CT showed less calcium blooming than conventional energy-integrating detector (EID) CT, resulting in systematically lower visual estimates of coronary luminal stenosis.

In 25 patients scanned with both systems on the same day, median visual stenosis decreased from 31.8% to 20.6% for reader 1 and from 22.9% to 6.5% for reader 2 with PCD CT. However, quantitative stenosis measurements did not significantly differ between modalities, suggesting that reduced blooming primarily improves visual representation of the residual lumen rather than changing quantitative measurements.

The advantage was achieved using the higher spatial resolution of PCD CT together with sharper vascular kernels and 100-keV virtual monoenergetic images. Importantly, the change in appearance could affect CAD-RADS classification when patients transition from EID-CT to PCD-CT during serial coronary imaging.

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Source: McCollough CH, Rajiah P, Bois JP, et al. Comparison of Photon-counting Detector and Energy-integrating Detector CT for Visual Estimation of Coronary Percent Luminal Stenosis. Radiology. 2023;309(3). doi:10.1148/radiol.230853.

Protocol

Detail	Value
Scanner	NAEOTOM Alpha (PCD-CT); SOMATOM Force (EID-CT)
Software	NAEOTOM Alpha VA40; offline reconstruction ReconCT VA50
Scan area	Coronary CTA / heart
Scan mode	PCD: adaptive prospectively triggered sequential; EID: adaptive prospectively triggered sequential or retrospectively gated spiral depending on heart rate/indication
Acquisition window	PCD: 65%–75%; EID sequential: at least 65%–75%
Tube voltage [kV]	PCD: 120; EID: CARE kV, reference 120
Effective mAs [mAs]	n.a.
IQ level	PCD: CARE kV image quality level 32
Dose modulation	CARE kV
CTDIvol [mGy]	PCD: 7.4 ± 3.1; EID: 25.7 ± 15.0
Temporal resolution [ms]	n.a.
Rotation time [s]	0.25
Pitch	n.a.
Matrix	n.a.
Field of view [mm]	n.a.
Slice collimation [mm]	PCD: 144 × 0.4; EID: 192 × 0.6
Slice width [mm]	PCD: 0.4; EID: 0.6
Reconstruction increment [mm]	PCD: 0.2; EID: 0.3
Reconstruction kernel	PCD: Bv48 (>90 kg) or Bv56 (≤90 kg); EID: Bv40
Iterative reconstruction	PCD: QIR level 4; EID: ADMIRE level 4
Spectral reconstruction	PCD: VMI at 50 and 100 keV
Reconstruction comparison	PCD CT vs EID CT
Contrast agent	Iohexol 350 mg I/mL (Omnipaque 350)
Contrast volume	Individualized from scan time + 7-s postthreshold delay × injection rate; followed by 40 mL mixture containing 12 mL contrast + 28 mL saline, then 10 mL saline
Flow rate	<50 kg: 4 mL/s; 50–100 kg: 5 mL/s; >100 kg: 6 mL/s
Bolus triggering	150 HU in ascending aorta at 120 kV
Patient preparation	Metoprolol 5 mg; sublingual nitroglycerin 0.4 or 0.8 mg
PCD acquisition protocol	Adaptive prospectively triggered sequential, 65%–75% acquisition window
EID acquisition protocol	Sequential for HR <75 bpm; retrospectively gated spiral for HR ≥75 bpm, unstable HR, or when systolic imaging indicated