A single‐scan T mapping method based on two gradient‐echo images with compensation for macroscopic field inhomogeneity |
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Authors: | Yuguang Meng Hao Lei |
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Institution: | 1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China;2. Graduate School, Chinese Academy of Sciences, Beijing 100049, China |
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Abstract: | T ‐weighted imaging (T WI) and quantitative T mapping with conventional gradient‐echo acquisition are often hindered by severe signal loss induced by macroscopic field inhomogeneity. Various z‐shimming approaches have been developed for T WI/T mapping in which the effects of macroscopic field inhomogeneity are suppressed while the sensitivity of T ‐related signal intensity to alterations in the microscopic susceptibility is maintained. However, this is often done at the cost of significantly increased imaging time. In this work, a fast T mapping method with compensation for macroscopic field inhomogeneity was developed. A proton density‐weighted image and a composite T ‐weighted image, both of which were essentially free from macroscopic field inhomogeneity‐induced signal loss, were used for the T calculation. The composite T ‐weighted image was reconstructed from a number of gradient‐echo images acquired with successively incremented z‐shimming compensation. Because acquisition of the two images and z‐shimming compensation were realized in a single scan, the total acquisition time for obtaining a T map with the proposed method is the same as the time taken for a conventional multiecho gradient‐echo imaging sequence without compensation. The performance and efficiency of the proposed method were demonstrated and evaluated at 4.7 T. Magn Reson Med 60:1388–1395, 2008. © 2008 Wiley‐Liss, Inc. |
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Keywords: | magnetic resonance imaging gradient echo susceptibility artifact T temporal resolution |
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