Gho Sung-Min, Liu Chunlei, Li Wei, Jang Ung, Kim Eung Yeop, Hwang Dosik, Kim Dong-Hyun
Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Republic of Korea.
Magn Reson Med. 2014 Aug;72(2):337-46. doi: 10.1002/mrm.24920. Epub 2013 Sep 4.
To propose a susceptibility map-weighted imaging (SMWI) method by combining a magnitude image with a quantitative susceptibility mapping (QSM) -based weighting factor thereby providing an alternative contrast compared with magnitude image, susceptibility-weighted imaging, and QSM.
A three-dimensional multi-echo gradient echo sequence is used to obtain the data. The QSM was transformed to a susceptibility mask that varies in amplitude between zero and unity. This mask was multiplied several times with the original magnitude image to create alternative contrasts between tissues with different susceptibilities. A temporal domain denoising method to enhance the signal-to-noise ratio was further applied. Optimal reconstruction processes of the SMWI were determined from simulations.
Temporal domain denoising enhanced the signal-to-noise ratio, especially at late echoes without spatial artifacts. From phantom simulations, the optimal number of multiplication and threshold values was chosen. Reconstructed SMWI created different contrasts based on its weighting factors made from paramagnetic or diamagnetic susceptibility tissue and provided an excellent delineation of microhemorrhage without blooming artifacts typically caused by the nonlocal property of phase.
SMWI presents an alternative contrast for susceptibility-based imaging. The validity of this method was demonstrated using in vivo data. This proposed method together with denoising allows high-quality reconstruction of susceptibility-weighted image of human brain in vivo.
通过将幅度图像与基于定量磁化率成像（QSM）的加权因子相结合，提出一种磁化率图加权成像（SMWI）方法，从而提供一种与幅度图像、磁化率加权成像和QSM不同的对比度。
使用三维多回波梯度回波序列获取数据。将QSM转换为幅度在零到一之间变化的磁化率掩码。该掩码与原始幅度图像相乘多次，以在具有不同磁化率的组织之间创建不同的对比度。进一步应用时域去噪方法来提高信噪比。通过模拟确定了SMWI的最佳重建过程。
时域去噪提高了信噪比，尤其是在没有空间伪影的晚期回波中。通过体模模拟，选择了最佳的相乘次数和阈值。重建的SMWI根据由顺磁性或抗磁性磁化率组织制成的加权因子创建了不同的对比度，并提供了无微出血的清晰描绘，而无微出血通常是由相位的非局部特性引起的晕影伪影。
SMWI为基于磁化率的成像提供了一种不同的对比度。使用体内数据证明了该方法的有效性。所提出的方法与去噪一起能够在体内高质量重建人脑的磁化率加权图像。
