Analysis of the aortic wall motion by SPAMM tagging method.

为了分析胸主动脉壁的血流动力学负荷，我们采用磁共振SPAMM标记法评价局部主动脉壁运动。我们研究了4名健康志愿者、7名真主动脉弓动脉瘤患者和10名降主动脉夹层患者。纵向参数用弯曲指数（lambda）表示，弯曲指数是用准矢状标记的切片计算的。圆形参数用扭曲指数（epsilon）表示，该指数是通过标记主动脉截面切片计算得到的。在4名主动脉正常的志愿者中，近端降主动脉弯曲指数最大，而降主动脉膈水平弯曲指数最小。高扭曲指数，在正常志愿者中发现：(1)前壁，(2)小弯曲壁。(3)横膈膜前壁水平，可能提示主动脉壁的高血流动力学负荷。有趣的是，那些高度扭曲的部位很好地证实了真正动脉瘤患者的破裂部位。主动脉瘤边缘的畸变指数与动脉瘤边缘的角度密切相关。动脉瘤边缘角度大，扭曲指数高，表明动脉瘤扩张或破裂的风险高。主动脉夹层假腔管壁畸变指数不高于真腔管壁畸变指数，但血栓形成假腔管壁畸变指数明显小于真腔管壁畸变指数。因此，扭曲指数可能预示主动脉夹层的预后。分析主动脉壁的血流动力学负荷是有用的。该方法可以分析运动，有助于了解主动脉壁的血流动力学负荷和主动脉瘤的特征。

To analyze hemodynamic load to the aortic wall of thoracic aorta, we evaluate local aortic wall motion by the SPAMM tagging method using magnetic resonance. We studied four healthy volunteers, seven patients with true aortic arch aneurysm, and ten patients with descending aortic dissection. The longitudinal parameters were expressed by the bending index(lambda), which was calculated using slices tagged parasagittally. Circular parameters were expressed by the distortion index(epsilon), which was calculated using tagged slices of aortic cross-section. In four volunteers with normal aorta, the bending index was greatest at the proximal descending aorta, and was smallest at the diaphragmatic level of the descending aorta. High distortion index, found in normal volunteers on (1)the anterior wall, (2)wall of lesser curvature. and (3)anterior wall of diaphragmatic level, may suggest high hemodynamic loads on the aortic wall. Interestingly, those high distortion sites confirm well to ruptured sites of patients with true aneurysm. Distortion index at the border of aortic aneurysm was well related to the angle of the aneurysmal border. Aneurysm with a high angle at its border had a high distortion index, which would indicate high risks of expansion or rupture of the aneutysm. Distortion index at the wall of pseudo-lumen of aortic dissection was not higher than that of the wall at the true lumen, but the distortion index at thrombosed wall of the pseudo-lumen was significantly smaller. Therefore, the distortion index may indicate the prognosis of aortic dissection. It is useful to analyze hemodynamic load to the aortic wall. This method can analyze the motion, and it is useful for understanding hemodynamic loading to the aortic wall and for characterization of the aortic aneurysm.