Selection of the optimum b factor for diffusion-weighted magnetic resonance imaging assessment of ischemic stroke
Selection of the optimum b factor for diffusion-weighted magnetic resonance imaging assessment of ischemic stroke
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DOI：
10.1002/mrm.20059
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发表时间：
2004-05-01
影响因子：
3.3
通讯作者：
Monahan, WG
中科院分区：
文献类型：
--
作者：
Kingsley, PB;Monahan, WG
本研究的目的是确定弥散敏感性因子B，当通过弥散加权MRI评价缺血性卒中时，该因子可优化弥散加权信号强度和表观弥散系数（ADCNR）的对比噪声比（CNR）。计算人脑典型ADC值的相对对比度、噪声水平、CNR和ADCNR，正常组织中成人为780 mum（2）/s，新生儿为1200 mum（2）/s，急性和亚急性卒中低20-40%，慢性卒中高50%。最佳B因子在很大程度上取决于ADC、TE是固定的还是随B因子变化、测量的是CNR还是ADCNR以及各向异性。成人急性和慢性脑卒中的最佳B因子为1000 s/mm（2），亚急性脑卒中为1200 s/mm（2）。新生儿的最佳值比成人低约200 s/mm（2）。在B因子的至少2倍范围内（最佳B因子的68-136%），CNR和ADCNR在最佳值的10%范围内。如果在所有情况下都使用单个B系数，则建议扩散B系数为1000 s/mm（2）。(C)2004 Wiley-Liss，Inc.
The purpose of this study was to determine the diffusion sensitivity factor b that optimizes the contrast-to-noise ratio (CNR) for both diffusion-weighted signal intensity and the apparent diffusion coefficient (ADCNR) when evaluating ischemic stroke by diffusion-weighted MRI. The relative contrast, noise levels, CNR, and ADCNR were calculated for typical ADC values in human brain, 780 mum(2)/s in adults and 1200 mum(2)/s in neonates in normal tissue, 20-40% less in acute and subacute stroke, and 50% more in chronic stroke. The optimum b factor depends strongly on the ADC, whether TE is fixed or varies with the b factor, whether CNR or ADCNR is measured, and anisotropy. The optimum b factor in adults is 1000 s/mm(2) in acute and chronic stroke, and 1200 s/mm(2) in subacute stroke. The optimum values are about 200 s/mm(2) lower in neonates than in adults. The CNR and ADCNR are within 10% of the optimum over at least a 2-fold range of b factors, from 68-136% of the optimum b factor. If a single b factor is to be used for all situations, a diffusion b factor of 1000 s/mm(2) is recommended. (C) 2004 Wiley-Liss, Inc.