Acute Injury Effect Of High Intensity Non-focused Ultrasound Irradiation To Porcine Liver

It has been a long history since ultrasound had been used therapeutically, which even earlier than the emergence of ultrasound imaging technology. Some ultrasonic therapeutic methods have become routine treatments, while high intensity focused ultrasound for treatment of liver malignant tumor in animal models and human studies have shown bright prospects. However, ultrasound therapeutic equipments actually used clinically have been confined in a relatively few types of equipment. Many newly developed ultrasound therapeutic equipments meet neither the clinical requirements of the effectiveness and safety, nor the needs of clinical practice. This situation is not only because of the complexity of the mechanism of ultrasound, but also because of the lack of interdisciplinary collaboration on the issue. There are also some common problems in research methods of ultrasonic biological effects. Entrusted by Shanghai Shiqiang Medical Equipment Co. Ltd, we initiate a research of application and development on SJ-1 ultrasonic generator developed newly in the field of hepatobiliary surgery. By integrated research of the physical parameters, acoustic field distribution and biological effects, we hope that the comprehension on liver acute damage caused by high-energy ultrasound exposure could been deepen, the performance of related equipment could been improved, the ultrasonic treatment research could been promoted through the morphological and molecular pathological observation of transition zone.Objective:.(1). To measure the acoustic field parameters of SJ-1 ultrasonic generator distributed in a certain space, to comprehend its attenuation model of the acoustic field.(2). To study the porcine liver acute damages caused by high-energy non-focused ultrasound exposure in vivo, to investigate the mechanism and meaning of pathological changes in transition zone.(3). To study the effects of liver blood occlusion and sulphur hexafluoride microbubbles on ultrasonic ablation, to investigate the way to acquire more big ablated focus without improving the output power or extend the duration of exposure, to observe the effects of sulphur hexafluoride microbubbles on the changes of injuries of transition zone.Methods: (1). The acoustic field distribution of SJ-1 ultrasonic generator transducer is to be measured point by point used piezoelectric hydrophone 8101 in an anechoic tank mechanically, when a standard sound source is used as a control.(2). The maximum depth of ablated lesions is to be measured by macroscopic and IOUS examination respectively in different irradiation models while the means of ultrasonic transducer contact directly with porcine liver in vivo is employed. Meanwhile, Pathological changes in transition zone and ablated lesions are observed by the optical microscope and the TEM. The apoptosis, proliferation and the expression of HSP70 and its mRNA of cells in the transition zone are detected.(3). Porcine livers are irradiated in vivo by high-energy ultrasound on three different conditions, which are: normal liver blood perfusion, liver blood occlusion with or without sulphur hexafluoride microbubbles. The maximum depth of ablated lesions is to be measured by macroscopic examination. Pathological changes in transition zone and ablated lesions are observed by the optical microscope and the TEM. The apoptosis, proliferation, the expression of HSP70 and its mRNA, and the expression of VEGF and CD34 of cells in the transition zone are detected.Results:(1). The acoustic field of SJ-1 ultrasonic generator transducer is spread divergently with continued wave and non-focused distribution. The actual sound axis coincides mainly with the geometric center axis of the transducer. The sound pressure distribution is in the shape of axisymmetric in general used the geometric center axis of the transducer as center line. The acoustic field of transducer head changed linearly with increase of the output power in high sensitivity and accuracy.(2). The maximum depth of ablated lesions in positive correlation with the output power of generator, also in positive correlation with the duration of irradiation in a certain range. Similar changes happened in transition zone and ablated lesions are observed by the optical microscope and the TEM in each groups, while no apparent correlation had been confirmed with the output power of generator and the duration of irradiation. The apoptosis index and PCNA positive index in transition zone in positive correlation with the output power of generator while little correlation with the duration of irradiation. The enhanced expression of HSP70 and its mRNA was distributed in transition zone unevenly when relatively higher expression was observed around vascellum. The level of expression of HSP70 and its mRNA was in positive correlation with the output power of generator while little correlation with the duration of irradiation.(3). The maximum depth of ablated lesions could be deepened after the irradiation of high-energy ultrasound with liver blood occlusion while AI, PI and the level of expression of HSP70 in transition zone was also increased. The maximum depth of ablated lesions could be deepened after the irradiation of high-energy ultrasound with liver blood occlusion combined with sulphur hexafluoride microbubbles, while severer injury in hepatocytes and vascular endothelial cells also had been observed and AI, PI and the level of expression of HSP70 and its mRNA in transition zone were also increased. Sulphur hexafluoride microbubbles could enter into the cytoplasm of hepatocytes during the irradiation. The level of the expression of VEGF and the numbers of MVD in transition zone could be increased by ultrasonic irradiation or liver blood occlusion, but they could be decreased by liver blood occlusion combined with sulphur hexafluoride microbubbles after ultrasonic irradiation.Conclusions:(1). The characteristic of the distribution of SJ-1 ultrasonic generator fit the use of liver injury effects of ultrasonic irradiation subsequently. The measurement system used in the experiment could meet the needs of detection of acoustic field of transducer in general.(2). Heat coagulative necrosis of porcine liver tissue in vivo could be made with high-energy non-focused ultrasound irradiation on the proper model. IOUS is a simple and accurate method to measure the volume of the ablated lesions. Apoptosis and proliferation have been enhanced at same time in transition zone which is an apparent characteristic of activities of tissue and cells in transition zone in acute stage. HSP70 may play an important role in the recovery and survival of the damaged tissue and cells in transition zone.(3). Both the blood perfusion and the vascellum could impact the ultrasonic energy absorbed by tissue. Sulphur hexafluoride microbubbles could not only enhance the ultrasonic ablation, but also impact on the changes in transition zone. Sulphur hexafluoride microbubbles may destroy the vascular endothelial cell and interrupt the progress of angiogenesis.