Lee H K, Nalcioglu O, Buxton R B
Department of Radiological Sciences, University of California, Irvine 92717.
Magn Reson Med. 1991 Sep;21(1):21-9. doi: 10.1002/mrm.1910210105.
One of the difficulties encountered in 19F NMR imaging of fluorinated blood substitutes is that these compounds often exhibit complex multipeak spectra. These peaks result in chemical-shift artifacts along the readout direction and blurred images. In addition, each peak excites a different slice (mis-selection) when a slice selection gradient is applied during the selective rf pulse. A simultaneous multislice imaging method has been developed to solve the inherent problem of mis-selection. The essence of this method is to use the two strongest peaks of the spectrum to excite controlled different multiple slices simultaneously, with or without a slice gap. The images corresponding to the two spectral lines are then separated from in- and out-of-phase images (Dixon method). This method corrects the problem of mis-selection and either improves the SNR or increases the number of slices over spectrally selective methods which image only one peak.
在氟化血液替代品的19F核磁共振成像中遇到的困难之一是,这些化合物常常呈现出复杂的多峰光谱。这些峰会在读出方向上导致化学位移伪影和图像模糊。此外,当在选择性射频脉冲期间施加切片选择梯度时,每个峰会激发不同的切片(误选)。已经开发出一种同时多层成像方法来解决固有的误选问题。该方法的本质是利用光谱中两个最强的峰同时激发可控的不同多个切片,有或没有切片间隙。然后,将与两条光谱线对应的图像从同相和反相图像中分离出来(狄克逊法)。该方法纠正了误选问题,并且相比于仅对一个峰进行成像的光谱选择性方法,要么提高了信噪比,要么增加了切片数量。