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，我们利用磁共振的Spamm标记法评估了局部的主动脉壁运动。我们研究了4名健康志愿者、7名真主动脉瘤患者和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(Lambda)是用沿矢状面标记的切片计算的。圆形参数用扭曲指数(Epsilon)表示，该指数是用标记的主动脉横断面切片计算的。在4名主动脉正常的志愿者中，降主动脉近端的弯曲指数最大，降主动脉横隔部的弯曲指数最小。正常志愿者的变形指数较高：(1)前壁，(2)小曲度壁。(3)隔水平前壁可能提示主动脉壁血流动力学负荷较高。有趣的是，这些高扭曲部位很好地证实了真性动脉瘤患者的破裂部位。主动脉瘤边缘变形指数与动脉瘤边缘夹角呈正相关。边缘呈高角度的动脉瘤变形指数高，提示动脉瘤扩张或破裂的风险较高。主动脉夹层假腔管壁的变形指数不高于真腔管壁的变形指数，而血栓形成的假腔管壁的变形指数明显小于真管腔的变形指数。因此，变形指数可作为判断主动脉夹层预后的指标。这对分析主动脉壁的血流动力学负荷是有用的。这种方法可以分析运动，这对了解主动脉壁的血流动力学负荷和主动脉瘤的特征是有用的。

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.