(Open access funding provided by Semmelweis University)
(RRF-2.3.1-21-2022-00003)
(ÚNKP-22–3-II-SE)
Virtual monoenergetic images (VMIs) from photon-counting CT (PCCT) may change quantitative
coronary plaque volumes. We aimed to assess how plaque component volumes change with
respect to VMIs.Coronary CT angiography (CTA) images were acquired using a dual-source
PCCT and VMIs were reconstructed between 40 and 180 keV in 10-keV increments. Polychromatic
images at 120 kVp (T3D) were used as reference. Quantitative plaque analysis was performed
on T3D images and segmentation masks were copied to VMI reconstructions. Calcified
plaque (CP; > 350 Hounsfield units, HU), non-calcified plaque (NCP; 30 to 350 HU),
and low-attenuation NCP (LAP; - 100 to 30 HU) volumes were calculated using fixed
thresholds.We analyzed 51 plaques from 51 patients (67% male, mean age 65 ± 12 years).
Average attenuation and contrast-to-noise ratio (CNR) decreased significantly with
increasing keV levels, with similar values observed between T3D and 70 keV images
(299 ± 209 vs. 303 ± 225 HU, p = 0.15 for mean HU; 15.5 ± 3.7 vs. 15.8 ± 3.5, p =
0.32 for CNR). Mean NCP volume was comparable between T3D and 100-180-keV reconstructions.
There was a monotonic decrease in mean CP volume, with a significant difference between
all VMIs and T3D (p < 0.05). LAP volume increased with increasing keV levels and all
VMIs showed a significant difference compared to T3D, except for 50 keV (28.0 ± 30.8
mm3 and 28.6 ± 30.1 mm3, respectively, p = 0.63).Estimated coronary plaque volumes
significantly differ between VMIs. Normalization protocols are needed to have comparable
results between future studies, especially for LAP volume which is currently defined
using a fixed HU threshold.Different virtual monoenergetic images from photon-counting
CT alter attenuation values and therefore corresponding plaque component volumes.
New clinical standards and protocols are required to determine the optimal thresholds
to derive plaque volumes from photon-counting CT.• Utilizing different VMI energy
levels from photon-counting CT for the analysis of coronary artery plaques leads to
substantial changes in attenuation values and corresponding plaque component volumes.
• Low-energy images (40-70 keV) improved contrast-to-noise ratio, however also increased
image noise. • Normalization protocols are needed to have comparable results between
future studies, especially for low-attenuation plaque volume which is currently defined
using a fixed HU threshold.
