| 摘要: |
| 【摘要】目的 由动态3D血管建模法分析4D相位对比MRI（PC-MRI）所测血流参数，判定正常主动脉及Stanford B型胸主动脉夹层患者血流动力学特征。方法 在带有时间分辨率的3D PC-MRI所获数据中，获取动态 3D 血管模型。定位任意一层血管参考截面作为参考相像，通过在与参考像的同一截面进行提取变形轮廓信息，在同一位点判定不同时相的靶血管脉动性，并应用时间描点法获取脉动性数据。应用该后处理方法，分析比较采用4D PC-MRI获取的19名健康成年志愿者及8例Stanford B型主动夹层患者在血流动力学信息上的差异。全部数据采用中位数（M）及四分位间距（QIR）表示，样本均值比较采用Mann-Whitney U 检验。结果 健康人的主动脉内流型绝大部分为层流，仅见极少量螺旋流，绝无涡流出现，主动脉全长范围内壁面切应力变化小而且均匀。Stanford B型主动脉夹层的 4D PC-MRI 所显示假腔内血栓，均能得到解剖形态学验证。假腔内逆向血流出现频率高，且峰值流速到达时间提前，对应真腔内正向血流比率高，无峰值流速提前到达表现。真假腔射血量比较：真腔（M=54.3 ml；IQR= 43.2～64.8)较假腔（M=31.6 ml；IQR=19.8～47.6)高（P＜0.01）；（2）真腔内的血流方向以前向为主（M=91.4%；IQR=90.0%～94.2%)，假腔内逆向血流所占比例高（M=40.3%，IQR=23.2%～53.3%；P＜0.01）；（3）假腔内的平均流速 （M =7.1 cm/s；IQR=4.9～9.8 cm/s) 低于真腔（M =18.0 cm/s,IQR=13.9～20.6 cm/s；P＜0.01）；（4）假腔内的峰值流速于R波后166.0 ms （IQR=132.8～210.0）到达，显著早于真腔215.0 ms（IQR=196.3～249.0 ms；P＜0.01）。螺旋流在假腔内出现几率高，尤其是假腔入口处（8/10），其中螺旋流仅出现在假腔内的比率为6/8；螺旋流通常出现在收缩早期，R波后的 158 ms （IQR=145～249 ms)，持续306 ms （IQR=217～537 ms)，最大的旋转角度 820°/搏。结论 血管动态3D模型能够高效分析 4D PC-MRI，并且提供定量的血流参数信息，血流方向、流速峰值到达时间及螺旋流的出现或改变可能参与主动脉夹层假腔的发生和发展，4D Flow MRI 技术可能为 Stanford B 型主动脉夹层治疗方案选择提供定量参考信息。 |
| 关键词: 动脉瘤，夹层 模型，心血管 磁共振成像 |
| DOI：10.3724/SP.J.1008.2014.00651 |
| 投稿时间：2013-06-12修订日期：2013-08-04 |
| 基金项目:海口市重点科技计划项目（2012-072）. |
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| Analysis of 4 dimensional phase contrast MRI by moving 3 dimensional model method in patients with Stanford B type aortic dissection |
| 郭子义,Chen Jing |
| () |
| Abstract: |
| Objectives The aim of this study was to visualize and quantify the flow characteristics in both healthy and patients with Stanford B type aortic dissection. All deriving blood flow parameters from four-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) were post-processed by moving three dimensional 3D model methods. Methods Moving 3D model of a blood vessel were captured from 4D PC-MRI. Determining a reference vascular cross-sectional plane and capturing the displacement contours information at the same plane were all used to determine the plurality of target vascular cross-sectional planes at multiple times. The plurality parameters of target vascular cross-sectional planes were determined by temporal tracking. The differences of flow characteristics both healthy (n=19) and patients (n=8) with Stanford B type aortic dissection were analyzed by 4D PC-MRI. Variables are expressed as median and inter quartile range (IQR). Sample means were compared using Mann-Whitney U test. A value of P≤0.05 was considered significant for all statistical tests. Results All 4D PC-MRI data were effectively post-processed by the moving 3D model methods. Qualitative blood flow visualization in the aorta of healthy volunteers showed laminar, without turbulences or vortex formation. In the ascending aorta there was a slight helical flow pattern, while there were little changes of wall shear stress in the entire thoracic aorta. Aortic remodeling and false lumen thrombosis of type Stanford B thoracic aortic dissection were determined by 4D PC-MRI and confirmed by T1 3D MRI anatomy scan. Blood flow in the false lumen was multidirectional and complex, with a high proportion of reverse flow, against the predominant aortic flow direction or true lumen. The peak velocity of blood flow in false lumen typically arrived earlier, while not in normal condition. Helical flow was seen mainly near the entry tear of false lumen with higher possibility. The stroke volume was greater in the true (54.3 ml，IQR 43.2—64.8 ml) compared with the false lumen (31.6 ml，IQR 19.8—47.6 ml，Mann-Whitney P＜0.01). The majority of the flow in the true lumen was forward flow (91.4%，IQR 90.0%—94.2%), whereas the false lumen had a high proportion of backward flow (40.3%，IQR 23.2%—53.3%). Expansion rates were measured at the proximal and distal sites. The average velocity of blood flow in the false lumen (7.1 cm/s， IQR 4.9—9.8 cm/s) was less than the true lumen (18.0 cm/s，IQR 13.9—20.6 cm/s， Mann-Whitney P＜0.01). (4) Maximum velocity occurred earlier in the cardiac cycle (false lumen, 166.0 ms （IQR 132.8—210.0） vs true lumen, 215.0 ms （IQR 196.3—249.0 ms，Mann-Whitney P＜0.01). Helical flow was only seen in the false lumen and occurred in 8 of 10 patients,only seen in false lumen 6 of 8 patients. Helical flow typically developed in early-systole, at 158 ms (IQR 145—249 ms) after the R-wave, and lasted for 310 ms (IQR 217—537 ms). The maximum amount of rotation seen was 820° per cardiac cycle. Conclusion Moving 3D model methods were suited to visualize and quantify the flow characteristics and flow parameters from 4D PC-MRI. The changes of flow orientation, time to peak velocity, and helical flow are able to quantify the appearance and development of thoracic aortic dissection. |
| Key words: Aneurysm,dissecting Models,cardiovascular Magnetic resonance imaging |
