Geis J R, Hendrick R E, Lee S, Davis K A, Thickman D
Department of Radiology, University of Colorado Health Sciences Center, Denver 80262.
Radiology. 1989 Mar;170(3 Pt 1):863-8. doi: 10.1148/radiology.170.3.2916044.
To study the effect of hydrogen spin density (N[H]) on magnetic resonance (MR) image contrast in white matter disease of the brain, T1, T2, and N[H] values were determined for normal white matter and idiopathic white matter lesions (IWMLs) in 21 patients by using multiple spin-echo (SE) sequences. T1 values of IWMLs were significantly greater than those of normal white matter in all patients studied, and T2 values of IWMLs were significantly greater in 20 of 21 patients. N[H] values of IWMLs were greater in 20 of 21 patients, with statistically significant differences from those of normal white matter in 17 of those 20 patients. Averaged over all 21 patients studied, N[H] values of IWMLs were 20% higher than N[H] values of normal white matter. The effect of unequal N[H] values on contrast between IWMLs and normal tissues is to reduce contrast on short SE sequences with a short repetition time (TR) and a short echo time (TE), while enhancing contrast between IWMLs and normal tissues on long TR/TE SE sequences. Elevated N[H] values in IWMLs have a minimal effect on contrast in conventional inversion-recovery (IR) sequences but substantially enhance contrast between IWMLs and normal brain tissues in short inversion time IR sequences.
为研究氢自旋密度（N[H]）对脑白质疾病磁共振（MR）图像对比度的影响，采用多自旋回波（SE）序列测定了21例患者正常白质和特发性白质病变（IWMLs）的T1、T2及N[H]值。在所有研究患者中，IWMLs的T1值均显著高于正常白质，21例患者中有20例IWMLs的T2值显著更高。21例患者中有20例IWMLs的N[H]值更高，其中20例患者中有17例与正常白质的N[H]值存在统计学显著差异。在所有21例研究患者中进行平均，IWMLs的N[H]值比正常白质的N[H]值高20%。N[H]值不相等对IWMLs与正常组织之间对比度的影响是，在短重复时间（TR）和短回波时间（TE）的短SE序列上降低对比度，而在长TR/TE SE序列上增强IWMLs与正常组织之间的对比度。IWMLs中升高的N[H]值对传统反转恢复（IR）序列的对比度影响最小，但在短反转时间IR序列中显著增强了IWMLs与正常脑组织之间的对比度。
