基于双掩模和3D区域迭代矢量选择的双回波Dixon水脂分离方法

Dual-echo Dixon method for water and fat separation based on double masks and regional iterative phasor extraction

目的:提出一种基于双掩模和3D区域迭代矢量选择(DM-3DRIPE)的水脂分离方法,使其在包含低信噪比(SNR)区域和强不均匀磁场情况下更可靠.方法:两点水脂分离的关键在于确定正确的场矢量.低SNR体素场矢量受噪声影响较大,为了降低噪声的影响,通过双掩模方法进行图像质量控制,先计算高质量体素点场矢量,然后再用于辅助计算低质量体素点场矢量.为了降低主磁场不均匀的影响,联合区域迭代矢量选择(RIPE)方法和三维信息辅助确定场矢量.结果:仿真实验结果表明,即使低SNR区域(rSN=0.8)或场不均匀性是常规场图的4倍,水图和脂肪图依然能够成功分离.413层人体图像实验结果显示,与传统的RIPE方法相比,DM-3DRIPE方法可将错误率从28.33%降到0.73%.结论:在低SNR区域和强不均匀主磁场存在时,DM-3DRIPE方法鲁棒性更高.

Objective:To develop a double masks and 3D regional iterative phasor extraction(DM-3DRIPE)method for robust water-fat separation in the presence of low signal-to-noise ratio(SNR)region and strong inhomogeneous field map.Methods:Determination of field phasor was the key of two-point water-fat separation.The field phasor of low SNR was affected by noise easily.To minimize the effect of noise,double masks were proposed to control the quality of image.Field phasor of high quality was firstly determined,and then was assisted to calculate field phasor of low quality.To reduce the effect of inhomogeneous field map,3D information was combined with regional iterative phasor extraction(RIPE)to reliably calculate phasor.Results:Results of simulation data showed water and fat maps were successfully achieved in the image containing low SNR region(r SN=0.8)and 4 times inhomogeneous field map than usual.Compared with traditional RIPE method,the DM-3DRIPE method decreased the error ratio from 28.33%to 0.73%for 413 in vivo images.Conclusion:The DM-3DRIPE method was shown more robust when applied to low SNR regionand strong inhomogeneous field map.