Buch Sagar, Cheng Yu-Chung N, Hu Jiani, Liu Saifeng, Beaver John, Rajagovindan Rajasimhan, Haacke E Mark
The MRI Institute for Biomedical Research, Waterloo, ON, Canada.
Department of Radiology, Wayne State University, Detroit, MI, USA.
NMR Biomed. 2017 Apr;30(4). doi: 10.1002/nbm.3551. Epub 2016 May 20.
Cerebral microbleeds (CMBs) are small brain hemorrhages caused by the break down or structural abnormalities of small vessels of the brain. Owing to the paramagnetic properties of blood degradation products, CMBs can be detected in vivo using susceptibility-weighted imaging (SWI). SWI can be used not only to detect iron changes and CMBs, but also to differentiate them from calcifications, both of which may be important MR-based biomarkers for neurodegenerative diseases. Moreover, SWI can be used to quantify the iron in CMBs. SWI and gradient echo (GE) imaging are the two most common methods for the detection of iron deposition and CMBs. This study provides a comprehensive analysis of the number of voxels detected in the presence of a CMB on GE magnitude, phase and SWI composite images as a function of resolution, signal-to-noise ratio (SNR), TE, field strength and susceptibility using in silico experiments. Susceptibility maps were used to quantify the bias in the effective susceptibility value and to determine the optimal TE for CMB quantification. We observed a non-linear trend with susceptibility for CMB detection from the magnitude images, but a linear trend with susceptibility for CMB detection from the phase and SWI composite images. The optimal TE values for CMB quantification were found to be 3 ms at 7 T, 7 ms at 3 T and 14 ms at 1.5 T for a CMB of one voxel in diameter with an SNR of 20: 1. The simulations of signal loss and detectability were used to generate theoretical formulae for predictions. Copyright © 2016 John Wiley & Sons, Ltd.
脑微出血（CMBs）是由脑内小血管破裂或结构异常引起的小脑出血。由于血液降解产物的顺磁性特性，可使用磁敏感加权成像（SWI）在体内检测到CMBs。SWI不仅可用于检测铁的变化和CMBs，还可将它们与钙化区分开来，这两者可能都是基于磁共振成像的神经退行性疾病重要生物标志物。此外，SWI可用于量化CMBs中的铁含量。SWI和梯度回波（GE）成像是检测铁沉积和CMBs的两种最常用方法。本研究通过计算机模拟实验，全面分析了在存在CMB的情况下，GE幅度、相位和SWI合成图像上检测到的体素数量随分辨率、信噪比（SNR）、回波时间（TE）、场强和磁敏感性的变化情况。利用磁敏感性图量化有效磁敏感性值的偏差，并确定CMB量化的最佳TE。我们观察到，从幅度图像检测CMB时，磁敏感性呈现非线性趋势，而从相位和SWI合成图像检测CMB时，磁敏感性呈现线性趋势。对于直径为一个体素、SNR为20:1的CMB，在7T时CMB量化的最佳TE值为3ms，在3T时为7ms，在1.5T时为14ms。信号损失和可检测性的模拟用于生成预测的理论公式。版权所有© 2016约翰威立父子有限公司。
