正常成人外侧膝状体MR显示序列的初步研究

Identify normal anatomy of lateral geniculate nucleus with MRI:a preliminary study

目的探讨正常成人外侧膝状体(LGN)的MR检查序列及最大高径及体积的正常参考范围,为正常视通路纤维束追踪及视通路相关病变的临床诊断、治疗及研究奠定基础。方法对10名成年健康志愿者进行横断位T2液体衰减反转恢复序列(T2-FLAIR)、T1加权-反转恢复自旋回波序列(T1W-IRTSE)、双回波自旋序列[包括质子密度加权成像(PDW)及T2自旋回波序列(T2TSE)]扫描及冠状位双回波自旋序列扫描。以双侧LGN信噪比(SNR)及LGN与周围感兴趣组织(包括视放射、内囊后肢及脑脊液)的对比噪声比(CNR)作为量化指标,对上述不同序列显示的LGN影像质量进行比较,并通过后处理软件测量LGN的最大高径和体积。结果 LGN显示情况评估:PDW序列能够清晰显示LGN表现为高于周围脑白质束的一楔形或三角形高信号区域,而其他3个序列对LGN结构显示不佳,且PDW序列同其他序列对LGN的显示评分差异有统计学意义(F=165.883,P<0.001)。LGN定量评估:PDW序列同其他3个序列间LGN的SNR和CNR具有差异性,且各序列间比较差异均具有统计学意义(P<0.05)。PDW序列上,LGN的SNR最高(93.02±12.20),LGN与内囊后肢、视放射的CNR也最高(分别为8.32±4.32、6.91±3.25)。LGN高径及体积测量:右侧LGN平均最大高径、体积分别为(4.51±0.29)mm、(95.62±3.41)mm3,左侧为(4.48±0.32)mm、(97.47±2.70)mm3,两侧差异均无统计学意义(t=-0.116,P=0.910;t=1.386,P=0.199)。结论①PDW序列能够清晰显示LGN的解剖结构并能够较准确地测量其最大高径及体积。②PDW序列可作为视通路纤维束追踪、视通路相关病变分析及视功能研究的较为理想的解剖定位序列。

Objective To explore the normal morphology of the normal lateral geniculate nucleus （LGN） with different MRI sequences. To establish an anatomical reference for the fiber tracking, clinical diagnosis or research of optic pathway lesion of visual system. Methods There were ten healthy volunteers enrolled and each underwent axial T 2 -FLAIR and T 1 W-IR TSE, and axial and coronal PDW and T 2 TSE. The signal-to-noise ratio （SNR） of LGN and contrast-to-noise ratio （CNR） of LGN to the surrounding tissue [optic radiation, posterior limb of the internal capsule （PLIC） and cerebrospinal fluid] were calculated. Image quality evaluation of the LGN on different sequences was made. The maximum height and the volume of bilateral LGN were measured. Results On PDW images, the LGN could be clearly shown in all cases. It often manifested as a small wedge-shaped or triangular area of high signal intensity relative to the surrounding white matter tracts. However, it was difficult to identify the LGN on other four sequences due to lower CNR between the LGN and the adjacent white matter tracts. The scores of LGN on PDW statistically differed with other three sequences （F=165.883,P＆lt;0.001）; SNR （93.02±12.20）, CNR to the PLIC （8.32±4.32） and CNR to the optic radiation （6.91±3.25） on PDW turbo spin-echo images were significantly higher than those on all other images （P＆lt;0.05）. The mean heights and volumes of the normal adults were （4.51±0.29） mm and （95.62±3.41） mm 3 of the right LGN, respectively; （4.48 ±0.32） mm and （97.47±2.70） mm 3 of the left LGN respectively. There were no significant differences between right and left sides （t=-0.116, P=0.910; t=1.386, P=0.199）. Conclusions （1）The PDW sequence can identify the anatomy of LGN clearly and can be used to measure the maximum height and the volume. （2）The PDW sequence can provide ideal anatomical reference for the studies of visual function, optic pathway lesions, and the fiber tracking of visual pathways.