Department of Radiology, Harvard Medical School, Massachusetts General Hospital, 165 Cambridge Street, Suite 400, Boston, MA 02114.
Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218.
J Biomech Eng. 2022 Sep 1;144(9). doi: 10.1115/1.4053997.
Transluminal attenuation gradient (TAG), defined as the gradient of the contrast agent attenuation drop along the vessel, is an imaging biomarker that indicates stenosis in the coronary arteries. The transluminal attenuation flow encoding (TAFE) equation is a theoretical platform that quantifies blood flow in each coronary artery based on computed tomography angiography (CTA) imaging. This formulation couples TAG (i.e., contrast dispersion along the vessel) with fluid dynamics. However, this theoretical concept has never been validated experimentally. The aim of this proof-of-principle phantom study is to validate TAFE based on CTA imaging. Dynamic CTA images were acquired every 0.5 s. The average TAFE estimated flow rates were compared against four predefined pump values in a straight (20, 25, 30, 35, and 40 ml/min) and a tapered phantom (25, 35, 45, and 55 ml/min). Using the TAFE formulation with no correction, the flow rates were underestimated by 33% and 81% in the straight and tapered phantoms, respectively. The TAFE formulation was corrected for imaging artifacts focusing on partial volume averaging and radial variation of contrast enhancement. After corrections, the flow rates estimated in the straight and tapered phantoms had an excellent Pearson correlation of r = 0.99 and 0.87 (p < 0.001), respectively, with only a 0.6%±0.2 mL/min difference in estimation of the flow rate. In this proof-of-concept phantom study, we corrected the TAFE formulation and showed a good agreement with the actual pump values. Future clinical validations are needed for feasibility of TAFE in clinical use.
管腔衰减梯度（TAG）定义为造影剂衰减沿血管下降的梯度，是一种影像学生物标志物，可提示冠状动脉狭窄。管腔衰减流速编码（TAFE）方程是一种理论平台，可基于 CT 血管造影（CTA）成像量化每条冠状动脉的血流量。这种公式将 TAG（即，沿血管的造影剂弥散）与流体动力学相结合。然而，这一理论概念从未在实验中得到验证。本原理验证型体模研究的目的是基于 CTA 成像验证 TAFE。动态 CTA 图像以 0.5 s 的间隔获取。将平均 TAFE 估计流速与直筒（20、25、30、35 和 40 ml/min）和锥形体模（25、35、45 和 55 ml/min）中四个预设泵值进行比较。在不进行校正的情况下，使用 TAFE 公式分别低估了直筒和锥形体模中的流速 33%和 81%。针对部分容积平均和对比剂增强的径向变化等成像伪影，对 TAFE 公式进行了校正。校正后，直筒和锥形体模中的流速估计具有很好的 Pearson 相关性，r 值分别为 0.99 和 0.87（p<0.001），流速估计值仅相差 0.6%±0.2 mL/min。在本原理验证型体模研究中，我们校正了 TAFE 公式，并显示出与实际泵值具有很好的一致性。未来需要进行临床验证，以确定 TAFE 在临床应用中的可行性。
