MTA-SE "Lendület" Cardiovascular Imaging Research Group, Semmelweis University Heart and Vascular Center, Városmajor Street 68., 1122, Budapest, Hungary.
Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, 116 N Robertson Blvd, Suite 400, CA, 90048, Los Angeles, USA.
Eur Radiol. 2023 Dec;33(12):8528-8539. doi: 10.1007/s00330-023-09876-7. Epub 2023 Jul 24.
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 mm and 28.6 ± 30.1 mm, 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.
光子计数 CT（PCCT）的虚拟单能量图像（VMIs）可能会改变定量冠状动脉斑块体积。我们旨在评估斑块成分体积如何随 VMI 而变化。
使用双源 PCCT 采集冠状动脉 CT 血管造影（CTA）图像，并在 40 至 180 keV 之间以 10 keV 的增量重建 VMIs。将 120 kVp（T3D）的多色图像用作参考。在 T3D 图像上进行定量斑块分析，并将分割掩模复制到 VMI 重建中。使用固定阈值计算钙化斑块（CP；>350 亨氏单位，HU）、非钙化斑块（NCP；30 至 350 HU）和低衰减 NCP（LAP；-100 至 30 HU）体积。
我们分析了 51 名患者（67%为男性，平均年龄 65±12 岁）的 51 个斑块。随着 keV 水平的增加，平均衰减和对比噪声比（CNR）显著降低，T3D 和 70 keV 图像之间的相似值观察到（299±209 与 303±225 HU，p=0.15 用于平均 HU；15.5±3.7 与 15.8±3.5，p=0.32 用于 CNR）。T3D 和 100-180 keV 重建之间的平均 NCP 体积相当。CP 体积呈单调下降，所有 VMI 与 T3D 之间均有显著差异（p<0.05）。LAP 体积随 keV 水平增加而增加，所有 VMI 与 T3D 相比均有显著差异，除 50 keV 外（分别为 28.0±30.8mm 和 28.6±30.1mm，p=0.63）。
VMIs 之间估计的冠状动脉斑块体积存在显著差异。需要有标准化协议，以便在未来的研究中获得可比的结果，特别是对于目前使用固定 HU 阈值定义的 LAP 体积。
光子计数 CT 的不同虚拟单能量图像改变了衰减值，从而改变了相应的斑块成分体积。需要新的临床标准和协议来确定从光子计数 CT 得出斑块体积的最佳阈值。
利用光子计数 CT 的不同 VMI 能量水平分析冠状动脉斑块会导致衰减值和相应斑块成分体积发生实质性变化。
低能量图像（40-70 keV）提高了对比噪声比，但也增加了图像噪声。
需要有标准化协议，以便在未来的研究中获得可比的结果，特别是对于目前使用固定 HU 阈值定义的低衰减斑块体积。
