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US5084675A Method for improving the signal-to-noise ratio in a nuclear magnetic resonance tomography apparatus 失效
改进核磁共振成像装置中信号噪声比的方法

Method for improving the signal-to-noise ratio in a nuclear magnetic
resonance tomography apparatus
摘要:
In the echo planar imaging (EPI) method of operating a nuclear magnetic resonance (magnetic resonance imaging) tomography apparatus, the necessary, rapid switching of gradients having a high amplitude usually cannot be achieved with square-wave gradients, and therefore a read-out gradient having a sinusoidal shape is generally used. Given a chronologically equidistant sampling of the nuclear magnetic resonance signal in the time domain, however, a sampling in the k-space with different rates is present. The bandwidth of the signal is proportional to the sampling rate in the k-space. In the method disclosed herein, bandwidth of a bandpass filter or a low-pass filter in the signal processing circuit for the nuclear magnetic resonance signal is adapted to the time dependent bandwith of the nuclear magnetic resonance signal, i.e., to the sampling rate in the k-space. The bandwidth is increased with increasing sampling rate. The signal-to-noise ratio is noticeably improved.
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