Effect of blood perfusion on the ablation of liver parenchyma with high-intensity focused ultrasound

Abstract

This paper discusses the effect of blood perfusion on the ablation of rat liver tissue with high-intensity focused ultrasound (HIFU). For this study a practical method has been developed, in which the liver blood flow can be reduced by ligation of the hepatic artery and portal vein. During the treatment the rat liver was mobilized out of the abdomen and the blood flow was measured using both the radioactive microsphere method and a laser Doppler blood-flow monitor. The results show that the hepatic blood flow was about 23 ml/100 g min-1 via the hepatic artery and about 227 ml/100 g min-1 via the portal vein. The total liver blood flow was reduced by 98% when both the hepatic artery and portal vein were ligated. Comparative lesions were made on the same liver lobes of rats with both normal and reduced blood flow using a focused ultrasound beam of 1.7 MHz, 67-425 W cm-2 spatially averaged focal intensity ISAL and 2-20 s exposure duration. A marked difference has been found between the lesion dimensions obtained with normal blood flow and that with reduced blood flow. For exposures at 169 W cm-2 the lesion diameter with normal blood flow was reduced by 14% for 3 s exposure duration compared to that obtained with both hepatic artery and portal vein ligated, while the reduction was more than 20% for longer durations.

Heart ablation using a planar rectangular high intensity ultrasound transducer and MRI guidance

“…For example for 6 W and 60 s duration the in vitro experiments the depth of lesion is approximately 15 mm. Using the same exposure in vivo, the depth of lesion is 12 mm which is attributed to the perfusion effect [58].…”

Utilidade do Ultrassom intracardíaco no isolamento de veias pulmonares usando cateter-balão a laser

“…We observed that complete electrical PV isolation was significantly more common when no blood flow leaks were identified between PV tissue and balloon catheter ablation, which determines the importance of catheter-balloon tissue contact also with laser energy. Good contact between the balloon and the PV orifice is necessary to obtain a circumferential lesion [14][15][16][17] . These requirements are probably related to photothermal and photomechanical interactions between laser energy on the tissue and heat transfer, which can be influenced by blood stream and tissue characteristics.…”

Extracorporeal ultrasound-guided high intensity focused ultrasound therapy: Present limitations

“…Increments were -27. 27-16.67%, 2.38-37.50% and 20.45-45.00% at 3, 6 and 12 s-insonation (106-266 W/cm 2 at 1.7 MHz), respectively (Chen et al, 1991). This technique, therefore, has a poor clinical relevancy.…”