小型猪早期肝泡状球蚴病模型能谱CT初步研究

Spectral CT imaging characteristics of early-stage hepatic alveolar echinococcosis in minipig models

目的分析小型猪早期肝泡状棘球蚴病（hepatic alveolar echinococcosis，HAE）模型的能谱CT影像表现，并确定最佳单能图像。方法贵州小型猪9头，行肝脏穿刺接种泡球蚴头节混悬液，接种25周经超声检查确认泡状棘球蚴接种成功的小型猪行64排能谱CT平扫和动脉期、门脉期、静脉期三期增强扫描，记录病灶大小、形态和内部结构。图像分析以5key为间距，选取40-140keV的21个单能图像，以肝实质为背景，测量三期HAE病灶图像的信噪比（signal tonoiseratio，SNR）、对比噪声比（contrast to noise ratio，CNR）和噪声，并绘制图像噪声、SNR和CNR散点图，确定三期HAE最佳单能量图像。在碘基图像上测量三期正常肝实质、HAE病灶及病灶边缘区域碘值并进行比较。检查结束后处死小型猪，对肝脏病变区域行组织病理学检查。结果小型猪早期HAE模型成功建模4头，均为单发病灶；CT平扫表现为类圆形囊性病灶，囊壁呈环形钙化，囊内呈水样密度，2个病灶囊内可见颗粒样钙化，病灶直径7．15-33．25mm；增强后病灶无明显强化，病灶边缘区呈低强化；三期散点图显示在70keV水平上早期HAE病灶的SNR和CNR均较高，噪声较低；病灶边缘区和正常肝实质在动脉期[（0.479±0．235）、（1．139±0．859）g／L]、门脉期[（4．804±0．895）、（17．464±1．078）g／L]和静脉期[（6．763±0．619）、（22．113±1．054）g／L]的碘值比较差异均有统计学意义（P〈0．01）；HAE病灶在三期扫描间的碘值比较差异无统计学意义（P〉0.05）；组织病理学检查可见单个或多个囊泡样红染结构，病灶边缘区纤维组织增生，同时可见微血管及多种炎细胞浸润。结论早期小型猪HAE病灶在能谱CT图像上有一定特征性表现，70keY图像是肝动脉期、门脉期及静脉期观察小型猪早期HAE病灶的最佳单能图像。

Objective To analyze the spectral CT imaging characteristics of early-stage hepatic alveolar echinococcosis （HAE） in minipig models, and to determine the optimal monochromatic image. Methods Nine Guizhou minipigs were inoculated Echinococcus protoscolex suspension by liver puncture. The successfully vaccinated AE minipigs, which were confirmed by ultrasonography 25 weeks after vaccination, underwent 64-slice spectral CT and enhancement scanning at arterial phase, portal venous phase and venous phase to record the size, shape and internal structure of the lesions. The signal to noise ratio （SNR）, contrast to noise ratio （CNR） and noise at three phases of HAE were detected among 21 monochromatic energy images from 40 to 140 keV at an interval of 5 keY, to draw the scatter diagrams of SNR, CNR and noise, and to choose the optimal energy image. The iodine values of the normal liver tissue, HAE lesion and marginal zone of HAE lesion were determined in iodine image and compared. These 9 minipigs were sacrificed after radiologic examination and the lesions in liver received histopathologic examination. Results Four minipigs were successfully established HAE models with single lesion in all. CT showed oval cystic lesions, annular calcification on the cyst wall, and watery density in cyst. The scattered calcification was found in the cyst in two lesions, with the average diameter of 19.12 ram. No obvious enhancement occurred after contrast enhancement, and low enhancement was found at the marginal zone of HAE lesions. Three-phase scatter diagrams showed that SNR and CNR were higher and the noise was lower in the 70 keV level in the early-stage HAE lesion. There were significant differences in the iodine values at marginal zone of HAE lesion and normal liver tissue among the arterial phase （（0. 479 ± 0. 235）, （1. 139 ±0. 859） g/L）, portal venous phase （（4. 804±0. 895）, （17. 464±1. 078） g/L） and venous phase （（6. 763±0. 619）, （22. 113±1. 054）g/L） （P〈0.01）, and there were no significant differences in the iodine values of HAE lesions among three phases （P〉0.05）. The histopathological examination showed single or multiple vesicle like structures, a large number of fibrous tissue hyperplasia and visible capillaries and a variety of inflammatory cell infiltration in the edge tissue of the lesions. Conclusion The early-stage HAE in minipig has certain features on spectral CT. The image in the 70 keV level is the best monochromatic image for observing the early-stage HAE at hepatic arterial phase, portal venous phase and venous phase.