Halbach R E, Battocletti J H, Salles-Cunha S X, Sances A
Med Phys. 1981 Jul-Aug;8(4):444-51. doi: 10.1118/1.594988.
Two types of crossed-coil nuclear magnetic resonance (NMR) blood flowmeter detectors have been developed for the noninvasive measurement of blood flow. The first is a cylindrical coil configuration suitable for limb blood measurement. A cylindrical flowmeter (12.5 cm internal diam) operating at a nuclear resonance frequency of 3.2 MHz has been applied to measurement of flow in the forearm. The second type is the flat crossed-coil detector, which retains many of the operational advantages of the cylindrical detector, but is suitable for blood flow measurement of almost any surface of the body. Three flat crossed-coil detectors are described, operating at NMR frequencies of 9, 21.4, and 75 MHz. Two types of intermediate frequency signal processors have been used in the NMR receivers, a simple diode type, and a synchronous detector. The synchronous detector is preferred for its ease of operation and superior stability. Modular detection systems containing transmitter, receiver, post-detector signal conditioning, and power supply have been designed for all of the flat crossed-coil detectors. A self-contained synchronous detector module is included in the 21.4 and 75 MHz systems.
已开发出两种交叉线圈式核磁共振（NMR）血流计探测器，用于无创测量血流。第一种是适用于肢体血流测量的圆柱形线圈配置。一种内径为12.5厘米、以3.2兆赫核磁共振频率运行的圆柱形血流计已应用于前臂血流测量。第二种是扁平交叉线圈探测器，它保留了圆柱形探测器的许多操作优点，但适用于身体几乎任何表面的血流测量。描述了三种扁平交叉线圈探测器，分别以9兆赫、21.4兆赫和75兆赫的核磁共振频率运行。NMR接收器中使用了两种类型的中频信号处理器，一种是简单的二极管类型，另一种是同步检波器。同步检波器因其操作简便和稳定性优越而更受青睐。已为所有扁平交叉线圈探测器设计了包含发射器、接收器、检波器后信号调理和电源的模块化检测系统。21.4兆赫和75兆赫系统中包含一个独立的同步检波器模块。
