From the Department of Radiology, Mayo Clinic, Rochester, MN.
J Comput Assist Tomogr. 2023;47(4):569-575. doi: 10.1097/RCT.0000000000001450. Epub 2023 Feb 10.
This study aimed to determine the optimal photon energy for virtual monoenergetic images (VMI) in computed tomography angiography (CTA) using photon-counting-detector (PCD) CT.
Under institutional review board approval, 10 patients (abdominal, n = 4; lower extremity, n = 3; head and neck, n = 3) were scanned on an investigational PCD-CT (Count Plus, Siemens Healthcare) at 120 or 140 kV. All images were iteratively reconstructed with Bv48 kernel and 2-mm slice thickness. Axial and coronal VMI maximum-intensity projections were created in the range 40 to 65 keV (5-keV steps). Contrast-to-noise ratio (CNR) was calculated for major arteries in each VMI series. Two radiologists blindly ranked each VMI series for overall image quality and visualization of small vessels and pathology. The median and SD of scores for each photon energy were calculated. In addition, readers identified any VMIs that distinguished itself from others in terms of vessel/pathology visualization or artifacts.
Mean iodine CNR was highest in 40-keV VMIs for all evaluated arteries. Across readers, the 50-keV VMI had the highest combined score (2.00 ± 1.11). Among different body parts, the 45-keV VMI was ranked highest for the head-and-neck (1.75 ± 0.68) and lower extremity (2.00 ± 1.41) CTA. Meanwhile, 50- and 55-keV VMIs were ranked highest for abdominal (2.50 ± 1.35 and 2.50 ± 1.56) CTA. The 40-keV VMI received the highest score for iodine visualization in vessels, and the 65-keV VMI for reduced metal/calcium-blooming artifacts.
Quantitatively, VMIs at 40 keV had the highest CNR in major arterial vasculature using PCD-CTA. Based on radiologists' preference, the 45- and 50-keV VMIs were optimal for small body parts (eg, head and neck and lower extremity) and large body parts (eg, abdomen), respectively.
本研究旨在使用基于光子计数探测器（PCD）的 CT 确定 CT 血管造影（CTA）中虚拟单能量图像（VMI）的最佳光子能量。
在机构审查委员会批准下，10 名患者（腹部，n=4；下肢，n=3；头颈部，n=3）在一台研究用 PCD-CT（Count Plus，西门子医疗）上以 120 或 140kV 进行扫描。所有图像均使用 Bv48 核和 2mm 层厚进行迭代重建。在 40 至 65keV（5keV 步长）范围内创建轴向和冠状 VMI 最大强度投影。在每个 VMI 系列中计算主要动脉的对比噪声比（CNR）。两位放射科医生对每个 VMI 系列的整体图像质量和小血管及病变的可视化进行盲法排名。计算每个光子能量的中位数和标准差。此外，读者还确定了在血管/病变可视化或伪影方面有别于其他 VMI 的任何 VMI。
对于所有评估的动脉，40keV VMI 的碘 CNR 平均值最高。在两位读者中，50keV VMI 的总分最高（2.00±1.11）。在不同的身体部位中，45keV VMI 对头颈部（1.75±0.68）和下肢（2.00±1.41）CTA 的评分最高。同时，50keV 和 55keV VMI 对头腹部（2.50±1.35 和 2.50±1.56）CTA 的评分最高。40keV VMI 对血管内碘的可视化评分最高，65keV VMI 对金属/钙 blooming 伪影的减少评分最高。
定量分析显示，在使用 PCD-CTA 时，40keV VMI 对主要动脉血管的 CNR 最高。根据放射科医生的偏好，45keV 和 50keV VMI 分别是小部位（如头颈部和下肢）和大部位（如腹部）的最佳选择。
