Ramadan U A, Markkola A T, Halavaara J, Tanttu J, Häkkinen A M, Aronen H J
Department of Radiology, Helsinki University Central Hospital, University of Helsinki, Finland.
Magn Reson Imaging. 1998 Dec;16(10):1191-9. doi: 10.1016/s0730-725x(98)00146-5.
The aim of the present investigation was to determine spin lock (SL) relaxation parameters for the normal brain tissues and thus, to provide basis for optimizing the imaging contrast at 0.1 T. 68 healthy volunteers were included. On-resonance spin lock relaxation time (T1rho) and off-resonance spin lock relaxation parameters (T1rho(off), Me/Mo), MT parameters (T1sat, Ms/Mo), and T1, T2 were determined for the cortical gray matter, and for the frontal and parietal white matters. The T1rho for the frontal and parietal white matters ranged from 110 to 133 ms and from 122 to 155 ms with locking field strengths from 50 microT to 250 microT, respectively. Accordingly, the values for the gray matter ranged from 127 to 155 ms. With a locking field strength of 50 microT, T1rho(off) for the frontal and parietal white matters were from 114 to 217 ms and from 126 to 219 ms, and for the gray matter from 136 to 267 ms with the angle between the effective magnetic field (B(eff)) and the z-axis (theta) ranging from 60 degrees to 15 degrees, respectively. The T1rho of the white and gray matters increased significantly with increasing locking field amplitude (p < 0.001). The T1rho(off) decreased significantly with increasing theta (p < 0.001). T1rho and T1rho(off) with theta > or = 30 degrees were statistically significantly shorter in the frontal than in the parietal white matters (p < 0.05). The duration, amplitude and theta of the locking pulse provide additional parameters to optimize contrast in brain SL imaging.
本研究的目的是确定正常脑组织的自旋锁定（SL）弛豫参数，从而为优化0.1 T场强下的成像对比度提供依据。研究纳入了68名健康志愿者。分别测定了皮质灰质、额叶白质和顶叶白质的共振自旋锁定弛豫时间（T1rho）、非共振自旋锁定弛豫参数（T1rho(off)、Me/Mo）、MT参数（T1sat、Ms/Mo）以及T1、T2。额叶白质和顶叶白质的T1rho分别在锁定场强为50 μT至250 μT时，范围为110至133 ms和122至155 ms。相应地，灰质的T1rho值范围为127至155 ms。在锁定场强为50 μT时，额叶白质和顶叶白质的T1rho(off)分别在有效磁场（B(eff)）与z轴夹角（θ）为60°至15°时，范围为114至217 ms和126至219 ms，灰质的T1rho(off)范围为136至267 ms。白质和灰质的T1rho随锁定场强幅值增加而显著增加（p < 0.001）。T1rho(off)随θ增加而显著降低（p < 0.001）。当θ≥30°时，额叶白质的T1rho和T1rho(off)在统计学上显著短于顶叶白质（p < 0.05）。锁定脉冲的持续时间、幅值和θ为优化脑SL成像对比度提供了额外参数。
