Objective:To compare the destructive characteristics of the bovine liver in vitro by double or single high intensity focused ultrasound exposure patterns.Methods:Two HIFU instruments(frequency of 1.6 MHz

acoustic power of 300 W

in situ intensity of 12 000 W/cm2)were used to ablate in vitro bovine liver ranging from 8 cm and 10 cm.In double exposure mode

two focused ultrasound transducers were fixed on the handle;the directions of focused ultrasound beams were opposite.In the single exposure mode

one focused ultrasound transducer was fixed on one handle

and a metal reflector was fixed on the other handle.The characteristics of coagulation necrosis and temperature change in treated bovine liver were observed.Results:In the double exposure mode

HIFU instrument induced complete coagulation necrosis of predetermined bovine liver targets

and the coagulation necrosis shape was similar to circular cylinder.However

under the same exposure energy and exposure time

the target area coagulation necrosis volume and the temperature were higher than those in the single side exposure mode.Conclusion:Working in double side exposure mode

HIFU can induce complete coagulation necrosis of predetermined bovine liver targets

and the effect surpasses the single side exposure mode.