Multiple Imaging Study Of The Hepatic Alveolar Echinococcosis In Rat

Objective:Successfully prepared the animal model of secondary hepatic alveolar echinococcosis (HAE) in rats, then all the rats were screened by ultrasonographuy (US) in early stage. The characteristic features of HAE in rats were summarized in order to accumulate the imaging data for early HAE. The dynamic progresses of HAE in rats were detected by Contrast-enhanced Ultrasound (CEUS) and MRI diffusion-weighted imaging (DWI). All imaging data compared with pathological examination, studied the relationship between the imaging features with pathological features, and explored the regular imaging pattern in different stage of HAE with multi-model imaging techniques, ana confirmed the value of multi-model imaging techniques in monitoring the evolution in HAE. Methods: We utilized the secondary hepatic alveolar echinococcosis animal models in this study. After9weeks, the surviving157rats were screened by US. The size, shape, border, internal echogenicity and blood flow of all lesions were recorded, and all imaging data were saved in the ultrasound workstation. Ten rats were selected randomly from different groups and accepted CEUS, MR-T1WI, T2WI and DWI imaging exam after9weeks,28weeks and50weeks. All procedures were manipulated in accordance with standard procedures, and detailed records were saved. The rats were sacrificed after the exam, then the specimens were stained with HE, Masson staining. Results:139rats were detected HAE lesions in liver by US from157rats. US had high pecificity (83.33%) and sensitivity (93.52%) in screening the early HAE model.142early lesions according to different sonographic features were divided into type1hyper-echoic spot, type2granular hyper-echoic spots, type3single hyper-echoic lesion and type4mixed pattern. Type1, type2and type3showed hyperechoic in US and no vesicle-like structure were detected. The average diameter of lesions in type1, type2and type3were less than type4. Early lesions presented needle-like or multiple cyst-like white structures in liver, the fluid in the vesicles were different depending on the size of lesions. The common features of these lesions in pathology were cyst structure surrounded by the characteristic periparastic granulomatous and fibrous tissues, which were shown blue in the Masson stain. Additionally, proliferation of small blood vessels, epithelioid cells, macrophages, fibroblasts and lymphocytes were shown in HE staining. The enhancement of the lesions observed can generally be divided into two different models in early HAE. Lesions of a size smaller than3mm and of type2exhibited ring enhancement during the arterial phase and no enhancement during portal venous phase. Type3as well as type4showed ring and central septa enhancement during the arterial and portal-venous phases. The lesions in advanced stage showed the ring enhancement in arterial phase and stronger enhancement in portal venous phas, no enhancement in internal lesions. The ratio of the width of enhancement with the diameter of the lesions decreased gradually in the evolution o the different stage. Early HAE lesions presented low signal on T1-weighted imaging, high signal on T2-weighted images, and high signal on DWI imaging with lower signal halo, similar to the "month halo " surrounding the lesions. On advanced stage, uniformity of low signal on T1-weighted images lesions, high signal mixed with low signal on T2-weighted images, and high signal on DWI images with the low signal halo surrounding the lesions. ADC value decreased gradually during the evolution of the lesions. Conclusion:US is very useful for screening the early HAE in rats due to its high sensitivity and high specifity. The typical ultrasonographical features of early HAE presented as hyper-echoic lesions in liver, only a little lesions presented as mixed type. The enhanced belt surrounding the lesions on CEUS was testified in pathology riched in micro blood vessels, which was the basis of the enhancement of CEUS. In early stage, the blood supply of HAE lesions mainly were hepatic artery, and portal veins taken part in the supply in advanced stage. DWI imaging can clearly show the internal structures and transition zone surrounding the lesions, which presented as the lower signal. The ADC values were lower than the internal lesions, which decreased gradually with the evolution of the HAE lesions. Thus, CEUS can show the dynamic evolution of peripheral blood vessels surrounding HAE lesions, and DWI can display the dynamic evolution of fiborisis surrounding the HAE lesions. A combination can reflect the dynamic changes of both vascularization and fiborisis in HAE lesions.