肝癌模型的23↑Na—MRI和1↑H扩散加权成像研究

Monitoring intrahepatic hepatocellular carcinoma growth by 23↑Na-MRI and 1↑H-diffusion weighted imaging

目的探讨应用无创23↑Na—MRI和1↑H-MRI监测大鼠原位肝癌的生长和结构与代谢转化过程的可行性。方法大鼠肝脏种植N1S1细胞制备原位肝癌，应用动物专用MR机对肝脏在建模后7、14、21、28d分别成像，DWI测量ADC值，单量子（SQ）23↑Na和三量子滤波（TQF）23↑Na—MRI分别测量组织Na^＋总含量和细胞内Na^＋含量，并与组织病理对照。采用方差分析比较肝脏、肿瘤、肿瘤／肝脏的ADC值、SQ和TQF↑23Na信号强度组间差异，并进一步采用SNK法进行组内两两比较。结果大鼠肝癌平均倍增时问为3．9d。肿瘤生长的4个星期中，和周围肝组织的ADC比值保持为1．4～1．5；肝癌的SQ和TQF23↑Na信号强度在生长过程中都升高，而周围肝组织基本不变，4个时间点（N1S1细胞种植7d、14d、21d和28d）肝癌与周围肝组织SQ、TQF的信号强度比值分别为1．05±0．20、1．41±0．32、1．50±0．45、1．62±0．50（F=2．97，P〈0．05）；1．32±0．11、1．54±0．18、2．38±0．22、2．39±0．16（F=11．18，P〈0．01）。病理示肿瘤活细胞区相对细胞外间隙（ECS）为（9．7±1．8）％，肿瘤内炎症／坏死细胞区ECS为（12．7±1．7）％，较正常肝脏ECS（5．2±0．4）％增加（t值分别为5．55、11．36，P〈0．05），单位面积内肿瘤存活细胞区和炎症／坏死细胞数较周围正常肝组织细胞数增多（t值分别为14．9、26．51，P〈0．05），细胞／核比值从正常的4．0±0．3降低至肿瘤细胞的1．6±0．1（t=20．08，P〈0．05），反映出细胞内外间隙不同权重的复杂变化。结论水ADC和SQ23↑Na—MRI反映ECS和组织总Na^＋的改变从而反映肿瘤组织的改变，TQF23↑Na-MRI反映细胞内Na^＋的变化从而反映肝癌细胞生理和代谢的转化。在肝癌生长中组织总Na^＋和细胞内Na^＋都增高。

Objective To monitor the structural and metabolic transformation of growing intrahepatic hepatocellular carcinoma （HCC） by non-invasive 23Na-MRI and 1↑H-DWI. Methods Each animal was examined weekly for 4 weeks after injection of 1 × 10^6 N1S1 cells into the left liver lobe. MR images were acquired with a Varian MR system. The effects of untreated growth on water apparent diffusion coefficient （ADC）, total tissue Na ^＋ and intracellular Na^＋ were monitored in rat HCCs using 1↑H-DWI, single-quantum （ SQ ） 23↑Na and triple-quantum-filtered （ TQF ） 23↑ Na-MRI. Histological analysis of HCC tissues was performed. Relative extracellular space （ECS）, cell numbers, and the cell to nucleus area ratio were calculated. Statistical analysis of the data was performed by ANOVA and post-hoe multiple comparison. Results The doubling time of the tumor growth was 3.9 days. During the four weeks in tumor growing, the ratio of water ADC to nearby liver was always 1.4 to 1.5. The HCC growth was associated with an increase in both total tissue and intracellular 23 Na signal intensity, and the changes in Nai^＋ were more profound than in Na1^＋. The ratio of the tumor SQ, TQF 23↑Na signal intensity to the nearby liver at four time points（7,14, 21 and 28 d） was 1.05 ±0.20,1.41 ±0. 32,1.50 ±0.45,1.62 ±0. 50（ F =2. 97 ,P 〈0. 05） ;1.32 ±0. 11, 1.54 ± 0. 18,2. 38 ± 0. 22,2. 39±0. 16 （ F = 11.18, P 〈 0. 01 ）, respectively. Statistical analysis of the histological slices showed that the mean of relative ECS in healthy liver was significantly lower compared to both ECS spaces in HCC viable ceils and inflammation/necrosis areas. The number of viable and inflamed/ necrotic cells was statistically higher compared to nearby liver tissue. However, the increase in ＂cellularity＂ was caused mostly by shrinkage of cellular cytoplasm when the ratio of cell to nucleus areas decreased from 4.0±0.3 （ normal liver） to 1.6±0.1 （viable HCC cells） （t=20.08,P〈0.05）.Conclusions Thewater ADC and SQ↑23 Na-MRI reflect ECS, total tissue Na^＋ changes and thus reflect mostly the compartmental alterations in tumor tissue, while TQF 23↑Na-MRI reflects the intracellular Na^＋ and thus physiological, metabolic transformation in HCC cells.