中文摘要：

目的探讨兔肝VX2瘤种植后MR扩散加权成像（OWI）的价值、动态特征及其病理机制。方法新西兰大白兔40只，采用开腹下块种植法行肝内VX2瘤种植，其中25只种植1个部位、15只种植2个部位。对全部种植兔于种植后第7、14、21天行DWI和第7、14天行常规MRI（T1WI、T2WI）检查，并对其中10个肿瘤标本行病理检查。结果种植后第7天DWI、T1WI、T2WI病灶发现率分别为78．7％（37／47）、10．7％（3／28）、53．6％（15／28），差异有统计学意义（χ^2=32．61，P〈0．01）；第14天分别为95．7％（45／47）、54．3％（19／35）、82．9％（29／35），差异有统计学意义（χ^2=21．50，P〈0．01）。种植后7d肿瘤生长较慢，内部尚未坏死，信号均匀；约14d后肿瘤生长开始加速，但此时内部坏死仍不明显，呈等或不均匀信号；第21天时肿瘤内部出现明显坏死，DWI上呈不均匀信号，成活肿瘤部分呈高信号，肿瘤坏死部分呈低信号，而囊变、液化部分呈高信号；从第7天至第21天。肿瘤边界逐渐由不清楚至清楚，内部信号由均匀至不均匀。敏感梯度因子（b）值为100s／，咖112时，种植后第7、14及21天，肿瘤周围表观扩散系数（ADC）值分别为（2．18±0．29）×10^-3、（1．96±0．33）×10^-3与（1．80±0．35）×10^-3mm^2／s，而肿瘤周围正常肝实质ADC值分别为（2．82±0．36）×10^-3、（2．61±0．40）×10^-3与（2．75±0．43）×10^-3mm^2／s。结论VX2瘤成活与坏死、囊变部分DWI具有典型表现，同时DWI在早期发现病变方面有重要潜在的价值。

英文摘要：

Objective To investigate the value and dynamic characteristics of diffusion-weighted imaging （DWI） in rabbit liver VX2 tumor model, with correlation of pathology. Methods Forty New Zealand rabbits were included in the study and VX2 tumor piece was implanted directly into the liver after laporotomy. Fiffteen had two intrahepatic implants while twenty-five had one implant. DWI was performed on the seventh, fourteenth and twenty-first day after implantation, while routine T1WI and T2WI sequences were done on the seventh and fourteenth day. Ten VX2 tumor samples were studied by pathology. Results The lump detection rates on the seventh day after implantation of DWI, T1WI and T2WI were 78.7% （37/47）, 10. 7% （3/28） and 53.6% （15/28） respectively with statistical significance （χ^2= 32. 61, P 〈 0. 01 ）, and those on the fourteenth day were 95.7% （45/47） ,54. 3% （19/35） and 82. 9% （29/35）respectively, also with statistical significance （χ^2 = 21.50, P 〈 0. 01 ） . The signal of most VX2 tumors on DWI was homogeneous on the seventh day after implantation duo to slow growth and no significant cellular death, On the fourteenth day VX2 tumor growth was increased, but no obvious tumor necrosis, so the signal of most VX2 tumors on DWI was either uniform or slightly inhomogeneous. On the twenty-lirst day, the signal of most VX2 tumors on DWI was inhomogeneous duo to obvious tumor necrosis. The areas of viable cells in VX2 tumors manifested as high signal on DWI, while dead or necrotic parts in VX2 tumors as low signal, however which might manifest as high signal on DWI when necrotic areas became liquefied or cystic. The tumor border on DWI changed gradually from dimness to distinct on the seventh, fourteenth and twenty-first day after implantation, and internal signal of tumor became gradually from uniform to inhomogeneous. When b value was 100 s/mm×2, ADC values in the peripheral area of tumor were （2. 18 ±0. 29） ×10^-3, （ 1.96 ± 0. 33） ×10^-3 and （ 1.80 ±0. 35） ×10^-3