IUniversity of Cologne, Faculty of Medicine and University Hospital Cologne, Institute for Diagnostic and Interventional Radiology, Cologne, Germany; Department of Radiology, Case Western Reserve University, Cleveland, OH, USA; Department of Radiology, University Hospitals Medical Center, Cleveland, OH, USA.
Department of Radiology, Case Western Reserve University, Cleveland, OH, USA; Department of Radiology, University Hospitals Medical Center, Cleveland, OH, USA.
Eur J Radiol. 2019 Aug;117:49-55. doi: 10.1016/j.ejrad.2019.05.019. Epub 2019 May 29.
This study aimed to identify the energy level of virtual monoenergetic images (VMI) that closest represents conventional images (CI) in order to demonstrate that these images provide improved image quality in terms of noise and Signal-to-noise ratio (SD/SNR) while attenuation values (HU) remain unaltered as compared to CI.
60 and 30 patients with contrast-enhanced (CE) and non-enhanced (NCE) spectral detector CT (SDCT) of the abdomen were included in this retrospective, IRB-approved study. CI and VMI of 66-74 keV as well as quantitative iodine maps were reconstructed (Q-IodMap). Two regions of interest were placed in each: pulmonary trunk, abdominal aorta, portal vein, liver, pancreas, renal cortex left/right, psoas muscle, (filled) bladder and subcutaneous fat. For each reconstruction, HU and SD were averaged. ΔHU and SNR (SNR = HU/SD) were calculated. Q-IodMap were considered as confounder for ΔHU. In addition, two radiologists compared VMI of 72 keV and CI in a forced-choice approach regarding image quality.
In NCE studies, no significant differences for any region was found. In CE studies, VMI images showed lowest ΔHU (HU CI/VMI: 104 ± 18/103 ± 17, p ≥ 0.05). Iodine containing voxels as indicated by Q-IodMap resulted in an over- and underestimation of attenuation in lower and higher VMI energies, respectively. Image noise was lower in VMI images (e.g. muscle: CI/ VMI: 15.3 ± 3.3/12.3 ± 2.9 HU, p ≤ 0.05). Hence, SNR was significantly higher in VMI compared to CI (e.g. liver 3.8 ± 0.6 vs 3.0 ± 0.8, p ≤ 0.05). In visual analysis, VMI were preferred over CI at all times.
VMI show improved SD/SNR characteristics while the attenuation remains unaltered as compared to CI.
本研究旨在确定与常规图像（CI）最接近的虚拟单能量图像（VMI）的能量水平，以证明这些图像在噪声和信噪比（SD/SNR）方面提供了更好的图像质量，同时衰减值（HU）与 CI 相比保持不变。
本回顾性、IRB 批准的研究纳入了 60 名和 30 名接受腹部对比增强（CE）和非增强（NCE）光谱探测器 CT（SDCT）的患者。重建了 66-74keV 的 CI 和 VMI 以及定量碘图（Q-IodMap）。在每个图像上放置了两个感兴趣区域：肺动脉干、腹主动脉、门静脉、肝脏、胰腺、左/右肾皮质、腰大肌、（充盈）膀胱和皮下脂肪。对于每种重建，计算了 HU 和 SD 的平均值。计算了 ΔHU 和 SNR（SNR=HU/SD）。Q-IodMap 被认为是 ΔHU 的混杂因素。此外，两名放射科医生以强制选择的方式比较了 72keV 的 VMI 和 CI 的图像质量。
在 NCE 研究中，任何区域均未发现显著差异。在 CE 研究中，VMI 图像显示出最低的 ΔHU（HU CI/VMI：104±18/103±17，p≥0.05）。Q-IodMap 所示的含碘体素导致较低和较高 VMI 能量的衰减分别高估和低估。VMI 图像的图像噪声较低（例如肌肉：CI/VMI：15.3±3.3/12.3±2.9 HU，p≤0.05）。因此，与 CI 相比，VMI 的 SNR 显著更高（例如肝脏 3.8±0.6 与 3.0±0.8，p≤0.05）。在视觉分析中，VMI 始终优于 CI。
与 CI 相比，VMI 显示出改善的 SD/SNR 特性，同时衰减保持不变。
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