Stevenson V L, Parker G J, Barker G J, Birnie K, Tofts P S, Miller D H, Thompson A J
NMR Research Unit, Institute of Neurology, Queen Square, WC1N 3BG, London, UK.
J Neurol Sci. 2000 Sep 15;178(2):81-7. doi: 10.1016/s0022-510x(00)00339-7.
To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain.
The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions.
Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times.
Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times.
Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection.
研究全脑正常表现白质（NAWM）和多发性硬化（MS）病灶的T1和T2弛豫时间变化。
与传统或快速自旋回波（FSE）序列相比，磁共振成像（MRI）序列快速液体衰减反转恢复（FLAIR）已显示出总体上病灶检出率增加，但后颅窝和脊髓的病灶较少。其原因尚不清楚，但可能是由于NAWM和MS病灶内T1和T2弛豫时间的变化。
10例患者和10名对照者接受了脑部MRI检查，包括FSE、快速FLAIR序列以及T1和T2弛豫时间测量。
在分析的151个病灶中（幕下22个，幕上129个），快速FLAIR序列漏诊了8个病灶。正常对照者幕下区域的T1和T2弛豫时间比幕上区域长。患者NAWM的弛豫时间在两个区域均比对照值延长。两个区域的病灶弛豫时间均长于对照白质或患者NAWM，但幕下差异不明显。快速FLAIR序列上不可见的8个后颅窝病灶的特征是T1和T2弛豫时间短，T1和T2均与患者NAWM重叠，T2弛豫时间与对照值重叠。
病灶和NAWM的弛豫时间特征在全脑各不相同。幕下病灶的T1和T2弛豫时间比幕上病灶更接近局部NAWM的弛豫时间，导致后颅窝病灶与背景NAWM之间的对比度降低。因此，一些病灶的特征与NAWM重叠，导致清晰度降低。利用这些信息，有可能优化快速FLAIR序列以改善后颅窝病灶的检出。
