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摘要
Purpose: The aim of this study was to propose a channel combination method for vertical bar B-1(+)vertical bar mapping methods using phase difference to reconstruct vertical bar B-1(+)vertical bar map. @@@ Theory and methods: Phase-based vertical bar B-1(+)vertical bar mapping methods commonly consider the phase difference of two scans to measure vertical bar B-1(+)vertical bar. Multiple receiver coils acquire a number of images and the phase difference at each channel is theoretically the same in the absence of noise. Affected by noise, phase difference is approximately governed by Gaussian distribution. Considering data from all channels as samples, estimation can be achieved by maximum likelihood method. With this method, all phase differences at each channel are combined into one. In this study, the proposed method is applied with Bloch-Siegert shift vertical bar B-1(+)vertical bar mapping method. Simulations are performed to illustrate the phase difference distribution and demonstrate the feasibility and facility of the proposed method. Phantom and vivo experiments are carried out at 1.5 T scanner equipped with 8-channel receiver coil. In all experiments, the proposed method is compared with weighted averaging (WA) method. @@@ Results: Simulations revealed appropriateness of approximating the distribution of phase difference to Gaussian distribution. Compared with WA method, the proposed method reduces errors of vertical bar B-1(+)vertical bar calculation. Phantom and vivo experiments provide further validation. @@@ Conclusion: Considering phase noise distribution, the proposed method achieves channel combination by finding the estimation from data acquired by multiple receivers coil. The proposed method reduces vertical bar B-1(+)vertical bar reconstruction errors caused by noise.
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单位1; 南方医科大学
