AIM:To investigate the possible clinical application value ofsecond harmonic imaging under low acoustic pressure.METHODS:Six New Zealand rabbits,averaging 2.7±0.4kg,were selected and operated upon to construct hepaticVX2 tumor carrier model.Hepatic VX2 tumors were imagedwith B mode UItrasonography (US),and second harmonicimaging (SHI) under high mechanic index (1.6) and lowmechanic index (0.1).Echo agent was intravenously injectedthrough ear vein at a dose of 0.01 mL/kg under B mode USand high MI SHI,and 0.05 mL/kg under low MI SHI,andthen the venous channel was cleaned with sterilized saline.All the images were recorded by magnetic optics (MO),andthey were analyzed further by at least two independentexperienced sonographers.RESULTS:Totally 6 hypoechoic and 3 hyperechoic lesionswere found in the six carrier rabbits with a mean size about2.1±0.4 under B mode ultrasound,they were oval or roundin shape with a clear outline or a hypoechoic halo at themargin of the lesions.Contrast agent could not change theechogenicity of the lesions under B mode US and SHI underhigh acoustic pressure.However,it could greatly increasethe real time visualization sensitivity of the lesions with SHIunder low acoustic pressure.CONCLUSION: Our results suggest that contrast enhanced SHI with low MI and a bubble non-destructive method would be much more helpful than conventional SHI in our future clinical applications. AIM: To investigate the possible clinical application value of second harmonic imaging under low acoustic pressure. METHODS: Six New Zealand rabbits, averaging 2.7 ± 0.4 kg, were selected and operated upon to construct hepatic VX2 tumor carrier model. Hepatoma VX2 tumors were imaged with B mode UItrasonography (US), and second harmonicimaging (SHI) under high mechanic index (1.6) and lowmechanic index (0.1). Echo agent was intravenously injected through ear vein at a dose of 0.01 mL / kg under B mode US and high MI SHI, and 0.05 mL / kg under low MI SHI, and at the venous channel was cleaned with sterilized saline. All the images were recorded by magnetic optics (MO), and the were were further analyzed at least two independentexperienced sonographers .RESULTS: Totally 6 hypoechoic and 3 hyperechoic lesionswere found in the six carrier rabbits with a mean size of about 2.1 ± 0.4 under B mode ultrasound, they were oval or roundin shape with a clear outline or a hypoechoic halo at the margin of the lesions. Contrast agent could not change theechogenicity of the lesions under B mode US and SHI underhigh acoustic pressure. However, it could greatly increase the real time visualization sensitivity of the lesions with SHI under low acoustic pressure. CONCLUSION: Our results suggest that contrast enhanced SHI with low MI and a bubble non-destructive method would be much more helpful than conventional SHI in our future clinical applications.