Morris P G, McIntyre D J, Rourke D E, Ngo J T
Department of Biochemistry, University of Cambridge, UK.
NMR Biomed. 1989 Dec;2(5-6):257-66. doi: 10.1002/nbm.1940020514.
The need for NMR selective pulses in magnetic resonance imaging and spectroscopy is reviewed. The shortcomings of the current generation of pulses are discussed and the need for new categories of pulse identified. Strategies for selective pulse design are outlined and two numerical optimization methods, simulated annealing and SPINCALC (a method recently introduced by us: J. T. Ngo and P. G. Morris, Magn. Reson. Med. 5, 217 (1987], are discussed in detail. Their use is illustrated and compared for the design of pi/2 phase-compensated pulses. Both methods require substantial amounts of CPU time, with simulated annealing the more demanding. Unconstrained, simulated annealing also tends to produce pulses with discontinuous waveforms. A crude two-dimensional pulse derived from a low flip angle approximation is illustrated.
回顾了磁共振成像和光谱学中对核磁共振选择性脉冲的需求。讨论了当前一代脉冲的缺点，并确定了对新型脉冲的需求。概述了选择性脉冲设计的策略，并详细讨论了两种数值优化方法，即模拟退火和SPINCALC（我们最近引入的一种方法：J.T. Ngo和P.G. Morris，Magn. Reson. Med. 5, 217 (1987]）。举例说明了它们在π/2相位补偿脉冲设计中的应用并进行了比较。这两种方法都需要大量的CPU时间，模拟退火的要求更高。无约束的模拟退火还倾向于产生具有不连续波形的脉冲。展示了一个由低翻转角近似推导而来的粗略二维脉冲。
