ABSTRACT
OBJECTIVES: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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. CLINICAL RELEVANCE STATEMENT: 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. KEY POINTS: ⢠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.
Subject(s)
Plaque, Atherosclerotic , Radiography, Dual-Energy Scanned Projection , Humans , Male , Middle Aged , Aged , Female , Signal-To-Noise Ratio , Tomography, X-Ray Computed/methods , Computed Tomography Angiography/methods , Coronary Angiography/methods , Plaque, Atherosclerotic/diagnostic imaging , Retrospective Studies , Radiography, Dual-Energy Scanned Projection/methodsABSTRACT
BACKGROUND: Coronary CT angiography (CCTA) pericoronary adipose tissue (PCAT) markers are promising indicators of inflammation. OBJECTIVE: To determine the effect of patient and imaging parameters on the associations between non-calcified plaque (NCP) and PCAT attenuation and gradient. METHODS: This was a single-center, retrospective analysis of consecutive patients with stable chest pain who underwent CCTA and had zero calcium scores. CCTA images were evaluated for the presence of NCP, obstructive stenosis, segment stenosis and involvement score (SSS, SIS), and high-risk plaque (HRP). PCAT markers were assessed using semi-automated software. Uni- and multivariable regression models correcting for patient and imaging characteristics between plaque and PCAT markers were evaluated. RESULTS: Overall, 1652 patients had zero calcium score (mean age: 51 years â± â11 [SD], 871 women); PCAT attenuation values ranged between -123 HU and -51 HU, and 649 patients had plaque. In univariable analysis, the presence of NCP, SSS, SIS, and HRP were associated with PCAT attenuation (2, 1, 1, 6 HU; respectively; p â< â.001 all); while obstructive stenosis was not (1 HU, p â= â.58). In multivariable analysis, none of the plaque markers were associated with PCAT attenuation (0 HU p â= â.93, 0 HU p â= â.39, 1 HU p â= â.18, 2 HU p â= â.10, 1 HU p â= â.71, respectively), while patient and imaging characteristics showed significant associations, such as: male sex (1 HU, p â= â.003), heart rate [1/min] (-0.2 HU, p â< â.001), 120 âkVp (8 HU, p â< â.001) and pixel spacing [mm3] (32 HU, p â< â.001). Similar results were observed for PCAT gradient. CONCLUSION: PCAT markers were significantly associated with NCP, however the associations did not persist following correction for patient and imaging characteristics.
