Department of Biomedical Engineering, University of Strathclyde, Glasgow, UK.
Research and Development, Terumo Aortic, Glasgow, UK.
Cardiovasc Eng Technol. 2023 Oct;14(5):655-676. doi: 10.1007/s13239-023-00679-x. Epub 2023 Aug 31.
Segmentation and reconstruction of arterial blood vessels is a fundamental step in the translation of computational fluid dynamics (CFD) to the clinical practice. Four-dimensional flow magnetic resonance imaging (4D Flow-MRI) can provide detailed information of blood flow but processing this information to elucidate the underlying anatomical structures is challenging. In this study, we present a novel approach to create high-contrast anatomical images from retrospective 4D Flow-MRI data.
For healthy and clinical cases, the 3D instantaneous velocities at multiple cardiac time steps were superimposed directly onto the 4D Flow-MRI magnitude images and combined into a single composite frame. This new Composite Phase-Contrast Magnetic Resonance Angiogram (CPC-MRA) resulted in enhanced and uniform contrast within the lumen. These images were subsequently segmented and reconstructed to generate 3D arterial models for CFD. Using the time-dependent, 3D incompressible Reynolds-averaged Navier-Stokes equations, the transient aortic haemodynamics was computed within a rigid wall model of patient geometries.
Validation of these models against the gold standard CT-based approach showed no statistically significant inter-modality difference regarding vessel radius or curvature (p > 0.05), and a similar Dice Similarity Coefficient and Hausdorff Distance. CFD-derived near-wall hemodynamics indicated a significant inter-modality difference (p > 0.05), though these absolute errors were small. When compared to the in vivo data, CFD-derived velocities were qualitatively similar.
This proof-of-concept study demonstrated that functional 4D Flow-MRI information can be utilized to retrospectively generate anatomical information for CFD models in the absence of standard imaging datasets and intravenous contrast.
动脉血管的分割和重建是将计算流体动力学（CFD）转化为临床实践的基本步骤。四维血流磁共振成像（4D Flow-MRI）可以提供血流的详细信息，但处理这些信息以阐明潜在的解剖结构具有挑战性。在这项研究中，我们提出了一种从回顾性 4D Flow-MRI 数据创建高对比度解剖图像的新方法。
对于健康和临床病例，将多个心脏时步的 3D 瞬时速度直接叠加到 4D Flow-MRI 幅度图像上，并组合成单个复合帧。这种新的复合相位对比磁共振血管造影（CPC-MRA）导致管腔内的对比度增强且均匀。随后对这些图像进行分割和重建，以生成用于 CFD 的 3D 动脉模型。使用时变的、三维不可压缩雷诺平均纳维-斯托克斯方程，在患者几何形状的刚性壁模型内计算了瞬态主动脉血液动力学。
这些模型与基于 CT 的金标准方法的验证表明，关于血管半径或曲率，不存在统计学上显著的模态间差异（p>0.05），并且具有相似的 Dice 相似系数和 Hausdorff 距离。CFD 衍生的近壁血液动力学表明存在显著的模态间差异（p>0.05），尽管这些绝对误差很小。与体内数据相比，CFD 衍生的速度在定性上相似。
这项概念验证研究表明，功能 4D Flow-MRI 信息可用于在没有标准成像数据集和静脉内对比的情况下，从回顾性生成 CFD 模型的解剖信息。
