植入式微波热凝固对正常肝组织的破坏作用--影像病理观察

目的研究正常肝组织微波凝固后CT、MRI和组织病理学的动态变化及其内在联系. 材料与方法 20只兔剖腹后采用18G微波天线(芯线长1cm),40W,2min凝固左肝内侧叶.分别于术后1～2h、1、2、4、6周行CT、MRI检查,观察病理变化. 结果增强CT、MR T1WI与组织学上所测凝固范围无明显差异(P＞0.05).术后即刻CT平扫为边界欠清楚的稍低密度区,无强化;MR T1WI、T2WI中央为低信号或无信号区,外周不均匀高信号区.1周后组织学上凝固区细胞结构丧失,细胞坏死,以后纤维组织逐渐长入其间形成分隔并取代坏死组织;CT上为边界清楚的低密度区;MR T1WI病灶中央低、等信号,边缘高信号;T2WI中央高信号,边缘为不均匀高信号区,两者之间为低信号,1周以后边缘亦为低信号.1周后,凝固灶周围出现肉芽组织增生,T1WI低信号,T2WI高信号区,呈环形强化.4～6周后肉芽组织机化,强化消失. 结论增强CT、MRI能准确反映组织微波凝固范围,MRI更有助于观察凝固性坏死的动态病理变化过程.

Effect of Implantable Microwave Thermal Coagulation on the Normal Liver in Rabbits: Imaging and Pathologic Observation

Objective To investigate the dynamic pathologic changes as well as imaging changes on CT, MRI of the normal rabbit liver after microwave tissue coagulation (MTC) procedure, to study the correlation between imaging findings and pathology. Materials and Methods With a 18G microwave needle electrode, left hepatic medial lobe was thermally coagulated in 20 rabbits at laparotomy. The subsequent course time changes in tissue on CT, MRI and histopathology were observed. Results No significant difference in measured necrotic size in the liver after MTC was found between enhanced CT, T 1WI and histology (P> 0.05). Immediately after MTC, a region with indistinct margin and slightly lower attenuation than that or surrounding normal liver parenchyma emerged on CT scans and showed no enhancement. On T 1WI and T 2WI, the coagulated area showed low signal or no signal in the center, and inhomogeneous high signal in the peripheral zone. One week later, the hepatic cells in the coagulated area became necrotic and lost their structures on histological exam. Then, fibrotic tissues gradually grew into the necrotic site, formed septa and finally replaced the necrotic tissues. It displayed as a well defined low density area on CT. On MRI, it showed low or iso signal centrally and high signal peripherally on T 1WI, while high signal centrally, heterogeneous high signal peripherally with low signal between the above two areas on T 2WI. After one week, a granulation layer appeared around the coagulated area, which presented as low signal on T 1WI and high signal on T 2WI with ring shaped enhancement. Four or six week later, the granulation tissue became organized and the enhancement was no longer seen.Conclusion Enhanced CT and MRI can exactly display the microwave coagulated extent, and, especially, MRI is of great help for dynamically observing the pathological changes of the coagulated necrosis.