Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
Department of Radiology and Biomedical Imaging, Yale Medical School, New Haven, Connecticut, USA.
Magn Reson Med. 2017 Nov;78(5):1862-1869. doi: 10.1002/mrm.26569. Epub 2016 Dec 8.
The conventional two-point (2pt) Dixon technique explicitly estimates B0 map by performing phase unwrapping. When signal loss, phase singularity, artifacts, or spatially isolated regions corrupt the measured phase images, this unwrapping-based technique will face difficulty. This work aims to improve the reliability of B0 mapping by performing unwrapping error correction.
To detect the unwrapping-caused phase errors, we determined a magnitude-based fat/water mask and used it as reference to identify pixels being mismatched by the phase-based mask, which was derived from the B0-corrected phase term of the Hermitian product between echoes. Then, we corrected the afore-determined phase error on a region-by-region basis. We tested the developed method with nine patients' data, and the results were compared with a well-established region-growing technique.
By adding the step to correct unwrapping-caused error, we improved the robustness of B0 mapping, resulting in better fat-water separation when compared with the conventional 2pt and the phasor-based region-growing techniques.
We showed the feasibility of B0 mapping with bipolar 2pt human cardiac data. The software is freely available to the scientific community. Magn Reson Med 78:1862-1869, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
传统的两点（2pt） Dixon 技术通过执行相位解缠来明确估计 B0 图。当信号丢失、相位奇点、伪影或空间孤立区域损坏测量的相位图像时，这种基于解缠的技术将面临困难。本研究旨在通过执行解缠误差校正来提高 B0 映射的可靠性。
为了检测解缠引起的相位误差，我们确定了基于幅度的脂肪/水掩模，并将其用作参考，以识别相位掩模不匹配的像素，该相位掩模是由回波的厄米特乘积的 B0 校正相位项得出的。然后，我们在逐区域的基础上校正预先确定的相位误差。我们使用九名患者的数据测试了所开发的方法，并将结果与成熟的基于区域生长的技术进行了比较。
通过添加校正解缠引起的误差的步骤，我们提高了 B0 映射的稳健性，与传统的 2pt 和基于向位的区域生长技术相比，实现了更好的脂肪/水分离。
我们展示了使用双极 2pt 人体心脏数据进行 B0 映射的可行性。该软件可供科学界免费使用。磁共振医学杂志 78:1862-1869,2017。©2016 国际磁共振学会。
