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目的观察大鼠脑C6胶质瘤模型的MR扩散加权成像(DWI)表现,并与肿瘤细胞密度等病理学变化进行对照,分析胶质瘤DWI表现的病理学基础。方法肿瘤细胞接种后12～18d分别对16只肿瘤生长良好的大鼠C6胶质瘤模型进行MR增强及DWI检查,观察胶质瘤MR增强及DWI表现,并与病理学改变进行对照分析。结果7例肿瘤灶增强MRI呈环行强化,表观扩散系数(ADC)图均显示肿瘤中心区域信号明显升高,肿瘤中心与周围区域ADC值分别为[(106.5±11.9)×10-5]、[(78.2±9.2)×10-5]mm2/s,两者之间差异有统计学意义(t=8.26,P<0.01);病理学显示该7只肿瘤灶内部明显坏死,细胞密度明显下降,肿瘤中心及周围区域细胞密度分别为(13±8)%、(40±5)%,两者间差异有统计学意义(t=6.55,P<0.01)。另外9只MR增强扫描肿瘤强化均匀,但其中6只ADC图信号不均匀,中心区及周围区ADC值分别为[(94.1±12.6)×10-5]、[(75.8±11.4)×10-5]mm2/s,两者之间差异有统计学意义(t=5.38,P<0.05)。镜下观察肿瘤中心区域细胞密度下降,肿瘤中心区域及周围区域肿瘤细胞密度分别为(29±4)%、(41±8)%,两者之间差异有统计学意义(t=3.92,P<0.05)。3只ADC图显示信号均匀的肿瘤灶中,其中心区及周围区ADC值分别为[(86.7±9.0)×10-5]、[(84.2±7.6)×10-5]mm2/s,两者之间差异无统计学意义(t=3.41,P>0.05)。镜下肿瘤中心及周围细胞密度分别为(38±7)%、(40±5)%,两者间差异无统计学意义(t=1.92,P>0.05)。结论DWI及ADC的信号差异可以反映胶质瘤内部细胞密度的差异,区别肿瘤内部坏死后的细胞稀疏区和肿瘤增殖旺盛的细胞密集区,为从微观角度观察胶质瘤的结构变化提供了基础。
Objective To observe the expression of MR diffusion-weighted imaging (DWI) in rat brain C6 glioma model and to compare with the pathological changes such as tumor cell density to analyze the pathological basis of glioma DWI. Methods Twenty-six tumor-bearing rat C6 glioma models were evaluated by MR and DWI at 12-18 days after inoculation of tumor cells. MR imaging and DWI were performed to evaluate gliomas. The pathological changes were compared with those of the controls. Results The enhancement of MRI in 7 cases showed ring enhancement. The apparent diffusion coefficient (ADC) showed that the signal in the center of the tumor was significantly increased. The ADC values were (106.5 ± 11.9) × 10-5, (78.2 ± 9.2) × 10-5] mm2 / s, the difference between the two groups was statistically significant (t = 8.26, P <0.01) .Pathological examination revealed that the seven tumor cells were significantly necrotic and the cell density was significantly decreased (13 ± 8)% and (40 ± 5)% respectively in the tumor center and the surrounding area. The difference between the two groups was statistically significant (t = 6.55, P <0.01). The other nine MR enhancement scan tumors were homogenized, but the signal of 6 ADCs was inhomogeneous. The ADC values in central area and surrounding area were (94.1 ± 12.6) × 10-5, (75.8 ± 11.4) × 10- 5] mm2 / s, the difference between the two was statistically significant (t = 5.38, P <0.05). Microscopically, the density of tumor cells in the center of the tumor decreased. The tumor cell density in the tumor center and surrounding area were (29 ± 4)% and (41 ± 8)%, respectively. The difference was statistically significant (t = 3.92, P <0.05). The ADC values of the three ADCs showed that the average ADC values were (86.7 ± 9.0) × 10-5 and [(84.2 ± 7.6) × 10-5] mm2 / s in the central and peripheral regions respectively There was no significant difference between the two groups (t = 3.41, P> 0.05). The tumor density in the center of the tumor and its surrounding cells were (38 ± 7)% and (40 ± 5)% respectively. There was no significant difference between the two groups (t = 1.92, P> 0.05). Conclusion The difference of signal intensity between DWI and ADC can reflect the difference of cell density in gliomas. Differentiating the cell sparsity after tumor necrosis and cell proliferation area with strong tumor proliferation provides the basis for observing the structure change of glioma from the microscopic point of view .