磁共振“自旋回波SE”简介

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                    <section><section powered-by="gulangu"><section><p><img src="image/20201019/cb5c859e4c702a480eea95f58a8b3a86_1.gif" /></p></section></section><section powered-by="gulangu"><section><section> <p><img src="image/20201019/0fb2fbafc7b3437de4dbf634df8944b0_2.png" /></p> <section><p>自旋回波SE的特点</p></section> </section> <p><img src="image/20201019/a69b059efa95a58f20b5a8ec2edf4a78_3.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;磁共振成像序列设计是磁共振成像系统硬件组件的工作时间表。序列设计就如同是钢琴的琴谱，按照琴谱设定的时间顺序来按动不同音调的琴键，就会得到不同曲调的音乐。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span>按照MRI硬件工作顺序和方式的特点，我们将序列设计分为许多种类，比如，按照信号采集中MRI信号回波形成的机制将序列分为自旋回波、快速自旋回波、梯度回波GRE、平面回波成像等。</span></p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span>自旋回波系列是MR成像的经典序列，其他序列的结构和特点均需要与SE序列进行比较。因此，有必要重点介绍SE序列。</span></p><p><span>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;自旋回波是射频脉冲与静磁场中核磁矩体系相互作用的结果。两个具有适当宽度的射频脉冲以一定的间隔相继作用在静磁场中的核磁矩体系上，经过一段时间在接收系统中会出现一个感应信号，信号与第二脉冲的间隔恰好等于脉冲之间的间隔，就像脉冲信号的回波一样，故称为“自旋回波”。</span></p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;SE序列的特点就是在90°脉冲激发后，利用180°复相脉冲，以剔除主磁场不均匀造成的横向磁化矢量衰减。</p></section></section></section><section powered-by="gulangu"><section><section> <p><img src="image/20201019/0fb2fbafc7b3437de4dbf634df8944b0_2.png" /></p> <section><p>自由进动信号FID</p></section> </section> <p><img src="image/20201019/a69b059efa95a58f20b5a8ec2edf4a78_3.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 由于宏观磁向量M持续绕B进动，故其顶端的轨迹在弛豫时表现为螺旋形。其横向分量Mxy将在平面xOy以螺旋线形式回到原点。其轨迹图、信号图、横向矢量衰减图如下。</p></section></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/e9781ac88bb50f19cf10610d928de344_6.jpg" /></p></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/ba297d34ceafe568308602bda4d1cc9f_7.jpg" /></p></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/7f8447458ae938476c93fd93c56ac5bf_8.jpg" /></p></section></section><section powered-by="gulangu"><section><section> <p><img src="image/20201019/0fb2fbafc7b3437de4dbf634df8944b0_2.png" /></p> <section><p>自旋回波系列结构</p></section> </section> <p><img src="image/20201019/a69b059efa95a58f20b5a8ec2edf4a78_3.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/4bdeff35ed951b6ce491a8e4c4b747a0_11.jpg" /></p></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/c64ca240b75ae4037fb48f8bcb36a68f_12.jpg" /></p></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/fce24350d20daba3bd3d4113287e0ada_13.jpg" /></p></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/f96b06e206229bcac39567765c1965ef_14.jpg" /></p></section></section><section powered-by="gulangu"><section><section><p><br  /></p></section></section></section><section powered-by="gulangu"><section><section> <section powered-by="gulangu"><section><section><p>欢</p></section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>迎</p></section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>关</p></section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>注</p></section></section></section> </section></section></section><section powered-by="gulangu"><section><section><p><br  /></p></section></section></section><section powered-by="gulangu"><section><section> <section powered-by="gulangu"><section><p><img src="image/20201019/3f40be0ec26fa5ac748f71d3b12018fd_15.jpg" /></p></section></section> </section><section> <section powered-by="gulangu"><section><section> </section></section></section> </section><section> <section powered-by="gulangu"><section><section><p>关注我们</p><p>一起涨姿势！</p></section></section></section> </section></section></section></section>