Imaging Efficiency and Contrast Enhancement in the Fast Gradient Refocusing Technique

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Abstract
The gradient recalled (refocused) echo technique produces images in very short scanning time. The signal to noise/unit time of the image is slightly better at small flip angles, provided T1 is estimated carefully. A short TR without dead space at low flip angles allows acquisition of high resolution 3D contiguous volume data within a few minutes. The gradient refocusing technique, however, can produce image artifacts due to uncompensated gradient induced phase shifts. The use of phase encoding gradient reversal removes the artifact, but also introduces signal dependence on transverse magnetization, which results in reduced tissue contrast. In this work we demonstrate that by inserting a strong gradient at the end of the pulse sequence in the slice encoding direction, tissue contrast is restored to the original Jevel with the absence of phase artifact.