磁共振监测脑脊液源性转移的形成及其表现基础

MRI monitoring of cerebral spinal fluid metastasis in rabbit model

目的建立脑脊液源性转移的动物模型，分析成瘤率及其MR／表现与病理基础，探讨MRI在肿瘤生物学形成中的监测价值。方法实验组24只新西兰大白兔经枕骨大孔蛛网膜下腔注射VX2肿瘤细胞（1×10^6个细胞/m1）的混悬液；对照组6只，抽取0．5ml生理盐水经枕骨大孔注入蛛网膜下腔，接种动物不同时间行MRI检查，T1WI，T2WI，FLAIR和注射Gd．DTPA造影剂后T1WI，FLAIR及DCE—MR／扫描。MR／扫描后立即获取标本观察形态学特点，镜下分析肿瘤生长特性。结果MRI平扫：①实验组：2只在延髓，1只在颈胸交界处脊髓实质内发现结节状异常信号灶（阳性率12．5％），T1WI呈低信号，T2WI呈等低信号。6只（25％）FLAIR序列见脑脊膜及结节灶呈略高信号。②对照组6只MRI均呈阴性表现。MR／增强表现：①实验组：T1WI增强扫描15／24只（62．5％）实验兔发现脑脊膜和（或）蛛网膜下腔呈线样不规则增厚或结节状强化，其中3只延脑和脊髓内病灶增强明显。FLAIR增强发现16／24只（66．67％）实验兔呈阳性征象。DCE—MR／扫描发现18／24只（75％）实验兔呈阳性征象。②对照组：5／6只实验兔MR／均呈阴性表现。大体标本证实20／24只转移的脑脊膜增厚，局部结节。镜下22／24只脑脊膜见多量肿瘤细胞沿软脑膜及蛛网膜浸润，部分肿瘤侵入脑及脊髓内。对照组未见明显异常改变。X2检验统计学结果：脑脊液源性转移的成瘤率91．67％。MR／平扫与增强后T1WI比较两者间差异有统计学意义（P〈0．01）。FLAIR增强和FLAIR平扫差异有统计学意义（P〈0．01）。T1WI，FLAIR增强阳性率与病理比较差异有统计学意义（P〈0．05）。DCE．MR／阳性率与病理结果差异有统计学意义（P〉0．05）。结论经枕骨大孔接种VX2瘤细胞成瘤率91．67％。MR／监测脑脊液转移瘤具有较高的敏感性并且可观察肿瘤的生长情况，DEC—MR／是检出脑脊膜转移的最佳序列。MR／检查的阳性率与病理结果仍存在差距，我们认为提高设备的分辨率，探讨最佳检查序列对脑脊液转移瘤的检出仍是至关重要的因素。

Objective To establish a rabbit model of cerebral spinal flow metastasis, to analyze the growth rate of tumor, and to investigate the value of MRI in monitoring the biology of tumor compared with pathology. Methods Twenty-four New Zealand white rabbits were inoculated with suspension of VX2 tumor cells in the subarachnoid space via the foramen magnum （experimental group ）, and 6 rabbits were inoculated with normal saline （control group）. MRI examination, including non-enhanced T1 WI, T2 WI, and FLAIR sequences and then T1WI, FLAIR after dynamic contrast enhanced with Gd-DTPA were done 7 - 22 days after inoculation with a 3-day interval. The rabbits were killed after the last MRI scan with their spinal cords, spinal meninges, and tumor taken out to undergo microscopy. Resnits （ 1 ） MRI plain scan showed that in the experimental group 2 nodi in the medulla and 1 nodus in the cervical spinal cord were found with low signal on T1WI and high signal on T2 WI; and FLAIR imaging showed local lesions with medial signal in 6 rabbits （25%）. And no abnormal signs were seen in the control group. （2） MRI enhancement showed that in the experimental group the images of 15 rabbit models were enhanced markedly with irregular thickening of meninges or nodules at the subarachnoid space on T1WI, positive signs were confirmed on FLAIR sequence in 16 of the 24 rabbits, and positive signs were noted on DCE-MRI scanning in 18 of the 24 rabbits （75%）. In the control group 5 of the 6 rabbits were negative in images. Microscopy showed thickened of meninges and spinal meninges in 20 of the 24 rabbits of the experimental group and spinal cord metastasis in 22 rabbits. No pathological changes were seen in the control group. Statistics showed a CSF metastasis rate of 91.67%. There were significant difference between the plain scan and T1WI with enhancement （ P 〈 0. 01 ） and between FLAIR scan and FLAIR enhancement scans. There was a significant difference between T1 WI and FLAIR enhancement and pathological findings （ P 〈 0. 05 ）. There was no significant difference between DCE-MRI method and pathological results （P 〉 0. 05 ）. Conclusion Gd-DTPA enhanced MRI scan sequences has a high sensitivity and specificity and can be used in monitoring the growth of CSF metastasis. There is a disparity between the MRI signs and pathological findings. It is a key that to improve the spatial resolution of machine and to investigate the best method for detecting early metastasis.