Objective:Explore the value of MRI DWI for monitoring the growth characteristics of rabbit liver VX2 tumor. Eval-uate the ADC value differences between VX2 tumors and the surrounding normal liver tissue at different periods and different b values. Methods:Twenty-five New Zealand white rabbits were enrolled. The VX2 tumors were implanted into liver after la-parotomy. Twenty-three successful modeling rabbits were randomly divided into three groups (eight in 14 d group,eight in 28 d group and seven in 42 d group). In the corresponding period,using PHILIPS 3.0T-Achieva/intera dual gradient superconducting high field strength MR scanner to do conventional and DWI scanning (b=100,400,600 and 800 s/mm2),and ADC maps were obtained. Then the ADC values of the tumors and normal liver tissue were measured for statistical analysis. Gross specimens of livers of all rabbits were sliced according to the direction of MR scanning cross sectional rightly after MR examination. Re-sults: ①All tumors showed obviously high signal intensity on DWI. On DWI maps,all tumors in the group of 14 d showed ho-mogeneously signal intensity and demonstrated well distributed texture without cystic necrosis according to pathology. However, the centra1 parts of all tumors in the group of 28 d and 42 d showed the signal intensity of cystic necrosis ,whose scopes were equal to that of specimen of gross pathology,while on T2WI only the central parts of 11 tumors showed patchy high signal in-tensity. ②The ADC values of VX2 tumors and normal liver tissues had significant difference(P<0.05) at same periods and dif-ferent b values. The ADC values of VX2 tumors had decreased with the increasing of b values ,which had significant difference (P<0.05)at same periods. The ADC values of VX2 tumors had no significant difference(P>0.05) at different periods and same b values. Conclusion:MR DWI is helpful in observing anatomy by different signal intensity,which can accurately reflect the pathological characteristics of the tumor and conduct a quantitative analysis through the ADC value ,it belongs to morphology and function imaging.%目的:探讨DWI在监测兔肝VX2瘤生长特性方面的价值;评价不同时期、不同b值条件下VX2瘤与周围正常肝组织的ADC值差异. 方法:取新西兰大白兔25只,成功建模的23只,随机分为3组,14 d组8只、28 d组8只及42 d组7只,在对应的时间内行MRI常规序列及DWI检查(b值取100、400、600、800 s/mm2),获得对应的ADC图,再分别测量肿瘤与周围正常肝组织的ADC值进行统计学分析;对全部肿瘤标本按MRI轴位扫描方向切层行大体病理检查. 结果:①DWI图像上,VX2瘤均呈明显高信号,与周围正常肝实质对比鲜明;14 d组肿瘤信号均匀,无坏死囊变,与DWI图像表现一致;28 d组与42 d组肿瘤中心可见斑片状低信号,且与大体病理所显示的坏死囊变区范围基本一致,而在常规T2WI上仅11例肿瘤中心见斑片状高信号.②同一时期不同b值条件下VX2瘤与周围正常肝组织的ADC值差异均有统计学意义(均P<0.05);同一时期,VX2瘤的ADC值随b值增大而下降(P<0.05);不同时期同一b值条件下VX2瘤的ADC值差异无统计学意义(P>0.05). 结论:DWI既能通过不同组织间的信号差异区别解剖结构、反映肿瘤的病理特征,还能通过ADC值测量对病灶进行量化分析,属于形态和功能双重成像.
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