Biolab, Department of Electronics and Telecommunications, Politecnico di Torino, Torino, Italy.
Ultrasonics. 2012 Sep;52(7):949-61. doi: 10.1016/j.ultras.2012.03.005. Epub 2012 Mar 21.
Accurate intima-media thickness (IMT) measurement of the carotid artery from minimal plaque ultrasound images is a relevant clinical need, since IMT increase is related to the progression of atherosclerosis. In this paper, we describe a novel dual snake-based model for the high-performance carotid IMT measurement, called Carotid Measurement Using Dual Snakes (CMUDS). Snakes (which are deformable contours) adapt to the lumen-intima (LI) and media-adventitia (MA) interfaces, thus enabling the IMT computation as distance between the LI and MA snakes. However, traditional snakes might be unable to maintain a correct distance and in some spatial location along the artery, it might even collapse between them or diverge. The technical improvement of this work is the definition of a dual snake-based constrained system, which prevents the LI and MA snakes from collapsing or bleeding, thus optimizing the IMT estimation. The CMUDS system consists of two parametric models automatically initialized using the far adventitia border which we automatically traced by using a previously developed multi-resolution approach. The dual snakes evolve simultaneously and are constrained by the distances between them, ensuring the regularization of LI/MA topology. We benchmarked our automated CMUDS with the previous conventional semi-automated snake system called Carotid Measurement Using Single Snake (CMUSS). Two independent readers manually traced the LIMA boundaries of a multi-institutional, multi-ethnic, and multi-scanner database of 665 CCA longitudinal 2D images. We evaluated our system performance by comparing it with the gold standard as traced by clinical readers. CMUDS and CMUSS correctly processed 100% of the 665 images. Comparing the performance with respect to the two readers, our automatically measured IMT was on average very close to that of the two readers (IMT measurement biases for CMUSS was equal to -0.011±0.329mm and -0.045±0.317mm, respectively, while for CMUDS, it was 0.030±0.284mm and -0.004±0.273mm, respectively). The Figure-of-Merit of the system was 98.5% and 94.4% for CMUSS, while 96.0% and 99.6% for CMUDS, respectively. Results showed that the dual-snake system CMUDS reduced the IMT measurement error accuracy (Wilcoxon, p<0.02) and the IMT error variability (Fisher, p<3×10(-2)). We propose the CMUDS technique for use in large multi-centric studies, where the need for a standard, accurate, and automated IMT measurement technique is required.
从最小斑块超声图像准确测量颈动脉内中膜厚度（IMT）是一种相关的临床需求，因为 IMT 增加与动脉粥样硬化的进展有关。在本文中，我们描述了一种用于高性能颈动脉 IMT 测量的新的双蛇模型，称为颈动脉双重蛇模型（CMUDS）。蛇（可变形轮廓）适应管腔内膜（LI）和中膜外膜（MA）界面，从而能够计算 LI 和 MA 蛇之间的 IMT。然而，传统的蛇可能无法保持正确的距离，并且在动脉的某些空间位置，它们甚至可能在它们之间坍塌或发散。这项工作的技术改进是定义一个基于双蛇的约束系统，该系统防止 LI 和 MA 蛇坍塌或渗血，从而优化 IMT 估计。CMUDS 系统由两个参数模型组成，这些模型自动使用我们使用先前开发的多分辨率方法自动跟踪的远外膜边界初始化。双蛇同时进化，并受到它们之间距离的约束，确保 LI/MA 拓扑的正则化。我们使用以前的常规半自动蛇系统（称为颈动脉单一蛇模型（CMUSS））对我们的自动 CMUDS 进行了基准测试。两位独立的读者手动追踪了一个多机构、多民族和多扫描仪的 665 个 CCA 纵向 2D 图像的 LIMA 边界。我们通过将其与临床读者追踪的金标准进行比较来评估我们系统的性能。CMUDS 和 CMUSS 正确处理了 665 个图像中的 100%。比较两个读者的性能，我们自动测量的 IMT 与两个读者非常接近（CMUSS 的 IMT 测量偏差分别等于-0.011±0.329mm 和-0.045±0.317mm，而对于 CMUDS，分别为 0.030±0.284mm 和-0.004±0.273mm）。CMUSS 的系统效能分别为 98.5%和 94.4%，而 CMUDS 的系统效能分别为 96.0%和 99.6%。结果表明，双蛇系统 CMUDS 降低了 IMT 测量误差的准确性（Wilcoxon，p<0.02）和 IMT 误差的可变性（Fisher，p<3×10(-2)）。我们提出 CMUDS 技术用于大型多中心研究，其中需要一种标准、准确和自动化的 IMT 测量技术。
