Elliott M A, Insko E K, Greenman R L, Leigh J S
Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6100, USA.
J Magn Reson. 1998 Feb;130(2):300-4. doi: 10.1006/jmre.1997.1319.
The high frequency k-space data in magnetic resonance imaging is often poorly reproduced due to the finite dynamic range of an analog-to-digital converter. The magnitude of this digitization error can equal and even exceed the magnitude of the thermal noise. Under such conditions, attempts to increase image signal-to-noise ratio via signal averaging meet with diminishing success. Because the relative size of the digitization error increases at higher spatial frequencies, a reduction in image resolution is incurred as well. By adjusting the level of the analog signal sampled by the analog-to-digital converter during the course of an imaging experiment, the magnitude of the digitization artifact can be greatly reduced. The results of simulations and imaging experiments are presented which demonstrate that this strategy improves both the signal-to-noise ratio and resolution of magnetic resonance images.
由于模数转换器有限的动态范围，磁共振成像中的高频k空间数据常常难以得到良好的再现。这种数字化误差的幅度可能等于甚至超过热噪声的幅度。在这种情况下，试图通过信号平均来提高图像信噪比的做法成效越来越小。由于数字化误差的相对大小在较高空间频率下会增加，图像分辨率也会降低。通过在成像实验过程中调整模数转换器采样的模拟信号电平，可以大大降低数字化伪影的幅度。文中给出了模拟和成像实验的结果，这些结果表明该策略提高了磁共振图像的信噪比和分辨率。
