Kim Do-Yeon, Park Jong-Won
Department of Information and Communication Engineering, Chungnam National University, Taejon 305-764, Republic of Korea.
Magn Reson Imaging. 2004 Apr;22(3):353-9. doi: 10.1016/j.mri.2004.01.007.
Currently, the North American symptomatic carotid endarterectomy trial, European carotid surgery trial, and common carotid method are used to measure the carotid stenosis for determining candidates for carotid endarterectomy using the projection angiography from different modalities such as digital subtraction angiography, rotational angiography, computed tomography angiography and magnetic resonance angiography. A new computerized carotid stenosis measuring system was developed using MR angiography axial image to overcome the drawbacks of conventional carotid stenosis measuring methods, to reduce the variability of inter-observer and intra-observer. The gray-level thresholding is one of the most popular and efficient methods for image segmentation. We segmented the carotid artery and lumen from three-dimensional time-of-flight MRA axial images using gray-level thresholding technique. Using the measured intima-media thickness value of common carotid artery for each case, we separated carotid artery wall from the segmented carotid artery region. After that, the regions of segmented carotid without artery wall were divided into region of blood flow and plaque. The calculation of carotid stenosis degree was performed as follows: carotid stenosis grading = (area measure of plaque/area measure of blood flow region and plaque) * 100%. No previous study has developed the carotid stenosis measuring method using MRA axial image. The new computerized stenosis measuring system has advantage over conventional caliper measuring methods; it will not only greatly increase the speed of stenosis measuring but also reduce the variability between readers. It should also reduce the variability between different institutions.
目前，北美症状性颈动脉内膜切除术试验、欧洲颈动脉手术试验和颈总动脉测量方法被用于通过数字减影血管造影、旋转血管造影、计算机断层血管造影和磁共振血管造影等不同方式的投影血管造影来测量颈动脉狭窄，以确定颈动脉内膜切除术的候选者。利用磁共振血管造影轴向图像开发了一种新的计算机化颈动脉狭窄测量系统，以克服传统颈动脉狭窄测量方法的缺点，减少观察者间和观察者内的变异性。灰度阈值法是最流行且高效的图像分割方法之一。我们使用灰度阈值技术从三维时间飞跃磁共振血管造影轴向图像中分割出颈动脉和管腔。利用每个病例颈总动脉的测量内膜中层厚度值，我们从分割出的颈动脉区域中分离出颈动脉壁。之后，将没有动脉壁的分割颈动脉区域划分为血流区域和斑块区域。颈动脉狭窄程度的计算如下：颈动脉狭窄分级 =（斑块面积测量值/血流区域和斑块面积测量值）×100%。此前尚无研究开发出利用磁共振血管造影轴向图像的颈动脉狭窄测量方法。这种新的计算机化狭窄测量系统比传统的卡尺测量方法具有优势；它不仅会大大提高狭窄测量的速度，还会降低读者之间的变异性。它也应该会降低不同机构之间的变异性。
