Nilgens H, Thelen M, Paff J, Blümler P, Blümich B
Klinik mit Poliklinik für Radiologie, Johannes-Gutenberg-Universität, Mainz, Germany.
Magn Reson Imaging. 1996;14(7-8):857-61. doi: 10.1016/s0730-725x(96)00216-0.
Stochastic NMR imaging is one of the less common NMR imaging techniques. Nevertheless, stochastic rf excitation is characterized by some remarkable features: the rf excitation power is at least two orders of magnitude lower in comparison to conventionally pulsed NMR imaging schemes. Thus, the technique is of interest for imaging of large objects. The systematic noise inherent in images obtained with random noise excitation has been eliminated by using pseudorandom noise together with Hadamard transformation for data evaluation. Data acquisition times are comparable to those of ultrafast imaging techniques. For slice selection, z magnetization is destroyed outside the slice region with specially designed low power pulses. Thus, gradient switching times are only limited by T1 and not T2*. Images are reconstructed by the backprojection algorithm. We have set up a stochastic imaging procedure on a conventional Bruker MSL 300 spectrometer, and have drawn a comparison between images obtained by the pseudorandom noise excitation and by conventional Fourier imaging.
随机核磁共振成像（Stochastic NMR imaging）是较不常见的核磁共振成像技术之一。然而，随机射频激发具有一些显著特点：与传统脉冲核磁共振成像方案相比，射频激发功率至少低两个数量级。因此，该技术对于大型物体成像具有吸引力。通过使用伪随机噪声并结合哈达玛变换（Hadamard transformation）进行数据评估，消除了随机噪声激发所获得图像中固有的系统噪声。数据采集时间与超快成像技术相当。对于切片选择，通过专门设计的低功率脉冲在切片区域外破坏z磁化。因此，梯度切换时间仅受T1限制，而非T2*。图像通过反投影算法重建。我们在传统的布鲁克MSL 300光谱仪上建立了随机成像程序，并对伪随机噪声激发和传统傅里叶成像所获得的图像进行了比较。
