Buonocore M H, Zhu D C
Department of Radiology, University of California-Davis Medical Center, Sacramento, California, USA.
Magn Reson Med. 2001 Jan;45(1):96-108. doi: 10.1002/1522-2594(200101)45:1<96::aid-mrm1014>3.0.co;2-j.
A new image-based ghost correction technique is described for general interleaved EPI. This technique works reliably with both even- and odd-number interleaved EPI sequences. It estimates the phase distortions causing the ghosts as a general function of (x,y) even in the presence of a significant overlap of parent image and ghosts. If the phase distortion is assumed to be a function of x (frequency-encode direction) only, the new technique is similar to a recently published correction method for general interleaved EPI (Hennel. J Magn Reson 1998;134:206-213). However, that study concluded that the method for general interleaved EPI did not work. It showed that the SNRs of the edge pixels were too low to accurately estimate the phase distortion. The new technique utilizes not one, but many pixels in the image for estimating the phase distortion. The technique requires a user-defined ROI to outline the parent image and identify so-called eligible pixels for estimating the phase distortion. When all eligible pixels are used, the SNR of the phase distortion estimate is comparable to that obtained in single-shot EPI. This study provides the first examples of high-quality, image-based correction of multiple ghosts in general interleaved EPI. Magn Reson Med 45:96-108, 2001.
本文描述了一种用于一般交错回波平面成像（EPI）的基于图像的新鬼影校正技术。该技术对偶数和奇数交错EPI序列均能可靠工作。即使在父图像和鬼影有明显重叠的情况下，它也能将导致鬼影的相位失真估计为（x,y）的一般函数。如果假设相位失真仅是x（频率编码方向）的函数，那么该新技术类似于最近发表的一种用于一般交错EPI的校正方法（Hennel. J Magn Reson 1998;134:206 - 213）。然而，该研究得出结论，用于一般交错EPI的方法不起作用。它表明边缘像素的信噪比太低，无法准确估计相位失真。新技术利用图像中的多个像素而非一个像素来估计相位失真。该技术需要用户定义感兴趣区域（ROI）来勾勒父图像并识别用于估计相位失真的所谓合格像素。当使用所有合格像素时，相位失真估计的信噪比与单次激发EPI中获得的信噪比相当。本研究提供了一般交错EPI中基于图像的高质量多鬼影校正的首个实例。Magn Reson Med 45:96 - 108, 2001。
