EFFECT OF BLOOD PERFUSION ON THE ABLATION OF LIVER PARENCHYMA WITH HIGH-INTENSITY FOCUSED ULTRASOUND

This paper discusses the effect of blood perfusion on the ablation of rat liver tissue with high-intensity focused ultrasound (HIFU). For th is study a practical method has been developed, in which the liver blo od flow can be reduced by ligation of the hepatic artery and portal ve in. During the treatment the rat liver was mobilized out of the abdome n and the blood flow was measured using both the radioactive microsphe re method and a laser Doppler blood-flow monitor. The results show tha t the hepatic blood flow was about 23 ml/100 g min-1 via the hepatic a rtery and about 227 ml/100 g min-1 via the portal vein. The total live r blood flow was reduced by 98% when both the hepatic artery and porta l vein were ligated. Comparative lesions were made on the same liver l obes of rats with both normal and reduced blood flow using a focused u ltrasound beam of 1.7 MHz, 67-425 W cm-2 spatially averaged focal inte nsity I(SAL) and 2-20 s exposure duration. A marked difference has bee n found between the lesion dimensions obtained with normal blood flow and that with reduced blood flow. For exposures at 169 W cm-2 the lesi on diameter with normal blood flow was reduced by 14% for 3 s exposure duration compared to that obtained with both hepatic artery and porta l vein ligated, while the reduction was more than 20% for longer durat ions.