Vascularity of hepatic VX2 tumors of rabbits: assessment with conventional power Doppler US and contrast enhanced harmonic power Doppler US.

Aim: To investigate the characteristics of the vascularity of hepatic metastasis.

Methods: Six New Zealand rabbits, weighing averagely 2.7+/-0.4 kg, were selected and operated to establish hepatic VX2 tumor carrier model. Hepatic VX2 tumors were then imaged with conventional B mode US, second harmonic imaging (SHI), color Doppler flow imaging (CDFI), power Doppler imaging (PDI) and harmonic PDI by a transducer S8 connected to HP-5 500 ultrasound system. A kind of self made echo contrast agent was intravenously injected at a dose of 0.01 mL/kg through ear vein, and then the venous passage was cleaned with sterilized saline.

Results: Totally, 6 hypoechoic lesions and 3 hyperechoic lesions were found in the six carrier rabbits with a mean size about 2.1+/-0.4 cm under conventional B mode ultrasound, they were oval or round in shape with a clear outline or a hypoechoic halo at the margin of the lesions. Contrast agent could not change the echogenicity of the lesions under conventional B mode and SHI, however, it could greatly increase the flow sensitivity of the lesions under PDI and harmonic PDI. Nutrient artery of these metastatic lesions might also be well depicted under contrast enhanced PDI and harmonic PDI.

Conclusion: Our result suggested that contrast enhanced PDI, especially harmonic PDI, was a promised method in the detection of vascularity of hepatic tumor nodules.