正常犬肝脏射频消融后CT、正电子发射计算机体层成像-CT与病理表现的比较

Findings of radiofrequency ablation in normal dog liver： comparative study of CT, positron emission tomography-CT and histopathology

目的比较正常犬肝脏射频消融（RFA）后不同时期的病理、CT及PET-CT表现，为肝脏肿瘤RFA后随访方案的制定提供指导及参考依据。方法成年健康杂种犬15只，随机数字表法分为5组（RFA后即刻组、1周组、2周组、4周组和8周组），每组3只。对每只犬肝脏行2次RFA治疗，消融后的实验犬于所在组对应的时间点行CT和PET-CT检查，完成检查后，静脉注射氯化钾溶液牺牲后，腹部切口取肝脏标本行病理检查。以消融灶周围环形反应带与正常肝实质强化／摄取率（rp/p）变化对图像进行评估，并将影像表现与病理改变进行对比分析。结果RFA术后即刻组，病理检查显示，消融灶中央凝固坏死，周围肝窦扩张充血；增强CT消融灶周围出现明显的环形强化带；PET-CT表现为低代谢消融灶被等代谢肝组织环绕。1～4周组，病理检查显示，消融灶坏死程度逐渐加重，周围肝组织表现为炎症细胞浸润、肉芽组织形成并逐渐成熟；CT动脉期和PET—CT消融灶周围均呈环形强化和高代谢，尤以1～2周组明显。8周组，病理检查显示，消融灶周围纤维组织增生明显；PET-CT显示上述强化和高代谢征象消失。增强CT动态变化曲线为术后即刻组明显强化（rp/p=1．34±0．21），1周组达峰值（rp/p=1．39±0．20），之后逐渐回落；PET—CT代谢变化为单峰曲线，1周组为代谢峰值（rp/p=1．19±0．09），即刻组及8周组分别趋于等代谢。结论CT和PET—CT均可较准确的反映肝脏RFA后的病理改变。为规避RFA术后炎症反应对评价肿瘤残余的干扰，影像检查应在术后即刻和8周后进行。术后即刻PET-CT扫描可能优于CT，1周后两者的诊断效能可能相似。

Objective To evaluate dynamic CT and PET-CT features of normal dog liver after radiofrequency ablation（RFA） correlated with the time-related histopathological changes. Methods Fifteen hybrid adult dogs in good health condition were evenly divided into 5 groups （the immediate, 1 st, 2 nd, 4 th and 8 th week group） according to random digits table methods. Twice RFA was performed for each dog liver. The dogs after RFA underwent CT and PET-CT scanning respectively at the time point defined for each group. All dogs were executed through intravenous injection of klorvess liquid after scanning. Liver samples were histologically examined. All images were assessed to determine the ratios （rp/p ） which referred to the comparison of rimlike enhancement or tracer uptake in the periphery of the necrosis to that in normal liver parenchyma. Those imaging results were compared and correlated with histopathological findings. Results For the immediate group after RFA procedure, central ablation lesions appeared coagulation necrosis and surrounding sinusoids engorged with blood. On the images of enhanced CT, marked rimlike enhancement was noticed in peripheral ablation lesions. While PET-CT showed decreased 18F-FDG uptake surrounded by homogeneous tracer distribution. For the 1 sr--4 th week group, central necrosis was gradually getting more severe. Infiltration of the inflammatory cells, granulation tissue formation and fibrous tissue restoration were noticed in peripheral ablation lesions. Rimlike enhancement and increased glucose metabolism appeared surrounding the lesions on CT and PET-CT, especially in the 1st to 2nd week groups. For the 8 th week group after RFA, the enhancement or hypermetabolism metioned above disappeared when perilesional tissue regeneration became more obvious. From the dynamic curve of changes on enhanced CT, marked enhancement occurred in the immediate group after ablation （ rp/p = 1.34 ± 0. 21 ）, reached its peak at the Ist week group （ rp/p = 1.39 ± 0. 20 ）, and then declined gradually. The metabolic changes on PET-CT showed a typical single peak curve, with the peak at the 1st week group （rp/p = 1.19 ±0. 09） and similar even metabolism at the immediate and 8 th week group. Conclusions Both CT and PET-CT imaging can well correlate with the histopathological changes after RFA in the normal liver. To avoid the interference of inflammatory reaction when differentiating normal liver tissue from residual tumor, it is better to take radiology examination immediately and 8 weeks after RFA. PET-CT probably has advantages over CT immediately after RAF. After 1 week, PET-CT and CT may have similar diagnostic efficacy.