Elasticity-based determination of isovolumetric phases in the human heart.
Elasticity-based determination of isovolumetric phases in the human heart.
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DOI：
10.1186/1532-429x-12-60
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发表时间：
2010-10-27
期刊：
影响因子：
--
通讯作者：
Sack I
中科院分区：
文献类型：
--
作者：
Elgeti T;Beling M;Hamm B;Braun J;Sack I
通过磁共振弹性成像（MRE）直接确定等容量心脏时间间隔，利用复杂信号的幅度来推导形态学信息，结合复杂信号的相位来进行张力松弛测量。35名健康志愿者和11名松弛异常患者接受了约25赫兹振动的经胸波刺激。采用k-空间分割、ecg门控梯度回忆的稳态回波序列和500 hz双极运动编码梯度，以小于5.2 ms的帧率获得一系列360度的心脏短轴视图复杂图像。用幅值图像测量左心室的横截面积，用相位图像分析外诱发波的幅值。在所有受试者中，确定了幅度下降和心室收缩开始之间的延迟时间，并将其分配给等容张力时间。相反，波幅增加与心室扩张之间的延迟被用来测量等容弹性松弛的时间。收缩期波幅减小，舒张期波幅增大。波幅的变化发生在形态变化之前。健康志愿者等体积弹性松弛时间为75±31 ms，明显短于等体积张力松弛时间136±36 ms （P < 0.01）。松弛异常（轻度舒张功能不全，n = 11）患者等容弹性松弛时间明显延长，为133±57 ms (P < 0.01)，而等容张力松弛时间在健康对照组范围内（161±45 ms, P = 0.053）。复杂的MRE信号传递了心脏形态和弹性的互补信息，可以结合起来直接测量人体心脏的等容张力和弹性松弛。
To directly determine isovolumetric cardiac time intervals by magnetic resonance elastography (MRE) using the magnitude of the complex signal for deducing morphological information combined with the phase of the complex signal for tension-relaxation measurements. Thirty-five healthy volunteers and 11 patients with relaxation abnormalities were subjected to transthoracic wave stimulation using vibrations of approximately 25 Hz. A k-space-segmented, ECG-gated gradient-recalled echo steady-state sequence with a 500-Hz bipolar motion-encoding gradient was used for acquiring a series of 360 complex images of a short-axis view of the heart at a frame rate of less than 5.2 ms. Magnitude images were employed for measuring the cross-sectional area of the left ventricle, while phase images were used for analyzing the amplitudes of the externally induced waves. The delay between the decrease in amplitude and onset of ventricular contraction was determined in all subjects and assigned to the time of isovolumetric tension. Conversely, the delay between the increase in wave amplitude and ventricular dilatation was used for measuring the time of isovolumetric elasticity relaxation. Wave amplitudes decreased during systole and increased during diastole. The variation in wave amplitude occurred ahead of morphological changes. In healthy volunteers the time of isovolumetric elasticity relaxation was 75 ± 31 ms, which is significantly shorter than the time of isovolumetric tension of 136 ± 36 ms (P < 0.01). In patients with relaxation abnormalities (mild diastolic dysfunction, n = 11) isovolumetric elasticity relaxation was significantly prolonged, with 133 ± 57 ms (P < 0.01), whereas isovolumetric tension time was in the range of healthy controls (161 ± 45 ms; P = 0.053). The complex MRE signal conveys complementary information on cardiac morphology and elasticity, which can be combined for directly measuring isovolumetric tension and elasticity relaxation in the human heart.