Discussion of mechanism behind "bamboo blind" sign observed in fatty liver parenchyma.

PURPOSE: To elucidate the mechanism behind the so-called "bamboo blind" sign frequently observed on B-mode images as multiple low-echoic lines in nonalcoholic steatohepatitis and highly fatty liver cases.

METHODS

Six types of acoustic shadowing artifacts that might be the cause of the bamboo blind sign were defined. B-mode images were acquired for 21 fatty liver cases (inc. 9 highly fatty liver cases). The cases were then pathologically diagnosed. A phantom experiment was also performed to investigate whether refraction occurs due to the gap of sound velocity between two different media.

RESULTS AND DISCUSSION: The mechanism of the bamboo blind sign corresponded well to the acoustic shadowing from small vessels in the liver. The phantom experiment validated the same phenomenon at a larger gap in sound velocity, which can be regarded as the same level as that in highly fatty liver cases.

CONCLUSION

The refraction between blood vessels and highly fatty liver parenchyma with decreased sound velocity is the dominant reason for the bamboo blind sign.