Hittmair K, Kramer J, Rand T, Bernert G, Wimberger D
MR Institute, University of Vienna, Austria.
Neuroradiology. 1996 May;38(4):360-6. doi: 10.1007/BF00596589.
Our purpose was to establish parameters for normal infratentorial brain maturation at 0.5 and 1.5 T and to evaluate the field strength criteria for the assessment of infratentorial brain maturation with MRI. We examined 27 children with normal psychomotor development (3 days to 24 months) with a 1.5 T system and 22 (4 days to 29 months) with a 0.5 T system; standard T2-weighted spin-echo sequences (TR/TE 2500/90 ms at 1.5 T and TR/TE 2200/90 ms at 0.5 T) were obtained. The signal intensity of infratentorial anatomical structures compared to their surroundings was classified as high, isointense or low by three neuroradiologists. For anatomical structures with age-related contrast changes, the time of these changes was determined statistically for the 0.5 T and 1.5 T system independently. The delineation of the structures without age-related contrast changes at the two field strengths was compared using a chi 2 test. Age-related contrast changed were found in the same anatomical structures ("marker sites") at 0.5 and 1.5 T. Generally, these changes were apparent in larger structures (pons, middle cerebellar peduncles, medulla, cerebellar folia, red nuclei, cerebral peduncles), with only slight field-strength-dependent differences in the time of the contrast changes. Contrast changes from high to isointense signal were observed slightly earlier at 0.5 T and changes from isointense to low signal slightly later at 0.5 T. The delineation of the smaller anatomical structures was significantly better at 1.5 T but these structures did not show age-related contrast changes. The differences in the assessment of infratentorial brain maturation between 0.5 and 1.5 T can be attributed to a lower signal-to-noise ratio at lower magnetic field strengths. These differences do not complicate temporal classification of the stage of infratentorial brain maturation using the same "marker sites" and the same temporal criteria at 0.5 or 1.5 T. However, higher field strengths are preferable for the assessment of smaller structures with physiological signal differences; this may imply better detection of small lesions at higher field strengths.
我们的目的是确定0.5T和1.5T场强下幕下脑正常成熟的参数，并评估MRI评估幕下脑成熟的场强标准。我们使用1.5T系统检查了27名精神运动发育正常的儿童（3天至24个月），使用0.5T系统检查了22名（4天至29个月）；获得了标准的T2加权自旋回波序列（1.5T时TR/TE为2500/90ms，0.5T时TR/TE为2200/90ms）。三位神经放射科医生将幕下解剖结构与其周围组织相比的信号强度分为高、等或低。对于具有与年龄相关的对比度变化的解剖结构，分别对0.5T和1.5T系统统计确定这些变化的时间。使用卡方检验比较了两种场强下无年龄相关对比度变化的结构的轮廓。在0.5T和1.5T时，在相同的解剖结构（“标记部位”）中发现了与年龄相关的对比度变化。一般来说，这些变化在较大的结构（脑桥、小脑中脚、延髓、小脑小叶、红核、大脑脚）中较为明显，对比度变化的时间仅存在轻微的场强依赖性差异。在0.5T时，从高信号到等信号的对比度变化观察得稍早，而从等信号到低信号的变化在0.5T时稍晚。在1.5T时，较小解剖结构的轮廓明显更好，但这些结构没有显示出与年龄相关的对比度变化。0.5T和1.5T之间幕下脑成熟评估的差异可归因于较低磁场强度下较低的信噪比。这些差异并不影响在0.5T或1.5T时使用相同的“标记部位”和相同的时间标准对幕下脑成熟阶段进行时间分类。然而，对于评估具有生理信号差异的较小结构，较高的场强更可取；这可能意味着在较高场强下能更好地检测小病变。
