HIFU Hemostasis of Liver Injuries Enhanced by Ultrasound Contrast Agents

Our objective was to investigate whether High‐Intensity Focused Ultrasound (HIFU) hemostasis can be achieved faster in the presence of ultrasound contrast agents (UCA). Incisions (3 cm long and 0.5 cm deep) were made in surgically exposed rabbit liver. Optison at a concentration of 0.18 ml/kg was injected into the mesenteric vein, immediately before the incision was made. The HIFU applicator (frequency of 5.5 MHz, and intensity of 3,700 W/cm²) was scanned manually over the incision (at an approximate rate of 1 mm/s) until hemostasis was achieved. The times to complete hemostasis were measured and normalized with the initial blood loss. The hemostasis times were 59±23 s in the presence of Optison and 70±23 s without Optison. The presence of Optison produced a 37% reduction in the normalized hemostasis times (p<0.05). Optison also provided faster (by 34%) formation of the coagulum seal over the lesion. Gross observations showed that the lesion size did not change due to the presence of Optison. Histological analysis showed that lesions consisted of an area of coagulation necrosis in vicinity of the incision, occasionally surrounded by a congestion zone filled with blood. Our results suggest the potential utility of microbubble contrast agents for increasing efficiency of HIFU hemostasis of internal organ injuries.