磁共振射频系统简介

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                    <section><section powered-by="gulangu"><section><p><img src="image/20201019/ba8293b7f09aa5e0c529073c44c5f52d_1.gif" /></p></section></section><section powered-by="gulangu"><section><section><p>磁共振的线圈构成</p></section><p><img src="image/20201019/f401e9a8d2efd661ef9036c35323b1dd_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/dee5b9b46be1002eaa1ebc28e6fe21f5_3.jpg" /></p></section></section><section powered-by="gulangu"><section><section><p>射频系统的作用</p></section><p><img src="image/20201019/f401e9a8d2efd661ef9036c35323b1dd_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 射频系统的作用是发射射频脉冲，使磁化的质子吸收能量产生共振，并接收质子在驰豫过程中释放的能量而产生MR信号，其频率在拉莫频率附近，包括射频线圈和射频放大器。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 用于发射射频建立射频磁场的射频线圈叫发射线圈，用于检测MR信号的射频线圈叫接收线圈。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;RF能够发挥作用必须满足两个基本条件，一是RF频率与拉莫进洞频率一致，二是RF线圈产生的B<span>1</span>要与主磁场产生产生的B<span>0</span>相垂直。</p></section></section></section><section powered-by="gulangu"><section><section><p>射频系统的工作原理</p></section><p><img src="image/20201019/f401e9a8d2efd661ef9036c35323b1dd_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;被磁化M<span>0</span>的大小远远小于系统主磁场的强度，为了准确测量，需要利用共振频率的射频施加在M<span>0</span>上，使之转到与主磁场垂直方向的平面上，再进行测量。</p></section></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/55db0d866c8f01c520a00aaaf2b989b7_6.jpg" /></p></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 只要M<span>0</span>的Z方向被翻转到XY平面内，并切割感应线圈，就会产生可被测到的电信号。M<span>0</span>越大，收到的电信号就会越强。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;在磁共振成像中，共振频率的射频脉冲的施加是翻转M<span>0</span>切割感应线圈的前提和必要条件，因此，在磁共振成像系统中，就是通过施加射频来实现对M<span>0</span>的测量的。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 无论哪种成像系列，射频线圈都是最先被启动工作的设备之一，这是产生可以被测量的M<span>0</span>的基础。</p></section></section></section><section powered-by="gulangu"><section><p><img src="image/20201019/ba1fe356068596ef940d48119a402a3f_7.jpg" /></p></section></section><section powered-by="gulangu"><section><section><p>射频系统的信噪比</p></section><p><img src="image/20201019/f401e9a8d2efd661ef9036c35323b1dd_2.png" /></p> <section></section></section></section><section powered-by="gulangu"><section><section><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 射频线圈的敏感容积越小，则信噪比越高；线圈与人体检查部位的距离越近，则信号越强，信噪比越高。</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 这两者直接决定着图像的质量，所以需要根据人体各个部位的不同形状、大小，制成不同尺寸和类型的线圈，以取得最佳图像质量。</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/b03564b81c141fca89785628ed079e58_9.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>