High Intensity Focused Ultrasound With Sonovue Microbubble Contrast Agent To Destroy Rabbit's Liver

OBJECTIVE To investigate the mechanism about ultrasound microbubble contrast-agent how to enhance the effect of high intensity focused ultrasound(HIFU) destroying the livers of rabbits, through observing the changes of biological focal field(BFF) treated by HIFU with Sono Vue^TM microbubble.METHODS Forty livers of New Zealand rabbits were ablated by HIFU for 30 seconds (P=220W, 1.6MHz). Livers were randomly divided into two groups. HIFU were performed in the manner of pointing scan in both groups. Prior to HIFU, Sono Vue^TM ultrasound microbubble contrast-agent or normal saline solution was administrated intravenously in group A and B, respectively. To measure data of hyper echoic region (includes gray scale of rising and its area), which appeared in the target volumes immediately after HIFU. Measure the length, width and thickness of actual necrotic area through dissecting liver of rabbits 20 minutes late after HIFU. And then Pathological examinations performed. All data were analyzed by SSPS for windows.RESULTS In both group, the gray scales of rising and its area were appeared in the target volumes immediately after HIFU. In group A, the gray scale of rising is 35.35±7.18, and its area is 7.70±1.72cm²; in group B, the gray scale of rising is 22.30±4.08, and its area is 2.33±0.68cm². there is significant difference between two groups (P＜0.01 ). we can find there are more necrosis in group A. With the length, width and thickness of actual nocrotic area of livers, in according to formula of area and volume( S=Ï€(X+Y)²/4, V=Ï€XYZ/6), in group A, the area and volume of actual necrosis is 8.17±1.29cm², 1.13±0.19cm³ respectively, in group B is 2.35±0.63cm², 0.21±0.06cm³ respectively. We can find more necrotic volume of target volumes in group A than in group B (P＜0.01). Energy effect factor(EEF) is nearly reduced 5.35 times. The relationship between the squares monitored by ultrasonic diagnostic unit and actual necrotic squares measured by dissection is linear relation(P＜0.01). We can predict the necrotic area according to the squares of gray scales rising (Y=3.179±0.868X). In both group, the necrosis is not reversible through examined by histopathology. The necrotic tissue is more loosen in group A, which distributing dense cavities, which structure of membrane and nucleolus is damaged. In group B, the necrosis is homogeneous coagulated necrosis.CONCLUSIONS Sono Vue^TM microbubble contrast agents can change the acoustic condition of biologic tissue, centralize local energy and enhance the effect of cavitation, improve caloric sensitivity and reduce trauma of target field, which boosts efficiency of HIFU. During the period of the treatment, B-mode diagnosis ultrasound apparatus can real-time monitor the condition of treatment, and predict actual necrotic area accurately, which ensure the validity, safety, practicability of HIFU with ultrasound microbubble contrast-agent.