Contrast-enhanced ultrasonographic imaging diagnosis on assessment of vascularity in liver metastatic lesions.

AIM: To investigate the vasculature of rabbit liver metastatic lesions by color Doppler imaging and power Doppler imaging (PDI) techniques. METHODS: Eight New Zealand rabbits with implanted VX2 liver tumors were used. All ultrasound examinations were performed with a HP 5500 color Doppler ultrasound scanner. Before and after the injection of contrast agent, the changes of gray scale and the periphery and intralesional blood flow of the liver metastatic lesion were carefully observed by B mode ultrasound, color Doppler flow imaging (CDFI) and PDI. RESULTS: Twelve lesions were found in the eight rabbits with implanted VX2 liver tumors, whose diameter ranged from 1.6 to 4.8 cm. Echoes of these lesions were not characterized and has lack of specificity. After the injection of contrast agent, the numbers of dot or strip-like flow messages increased both at the periphery and inside of these lesions under the mode of CDFI and PDI, and were more pronounced under PDI. Morphology of intralesional vessels extended, even branched and some signals were clearly found encircling the lesion. And some vessels were found penetrating into the center of the lesion. CONCLUSION: PDI after injection of self-made echo contrast agent can show a pronounced sensitivity than that of B mode ultrasound and CDFI in diagnosis of vascularity of a metastatic lesion.

Assessment of hepatic VX2 tumors of rabbits with second harmonic imaging under high and low acoustic pressures.

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. Hepatic VX2 tumors were imaged with B mode Ultrasonography (US), and second harmonic imaging (SHI) under high mechanic index (1.6) and low mechanic 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 then the venous channel was cleaned with sterilized saline. All the images were recorded by magnetic optics (MO), and they were analyzed further by at least two independent experienced sonographers. RESULTS: Totally 6 hypoechoic and 3 hyperechoic lesions were found in the six carrier rabbits with a mean size about 2.1+/-0.4 under 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 B mode US and SHI under high 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.

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.