Using 3D printed structures to evaluate the potential causes of the color Doppler twinkling signature

The color Doppler twinkling artifact has been attributed to existing microbubbles or cavitation occurring on objects like kidney stones, some breast biopsy markers, and sandpaper. The grooves of helical constructs that twinkle may provide sufficient locations for bubble retention and/or cavitation. We developed six half-cylinders that replicate the geometry of twinkling helical constructs with a micro 3D-printing process to explore how their characteristics relate to twinkling. Four copies of each design including a control were created. The cylinders had pitch (groove-to-groove distance) of 87.5–343 μm and amplitude (groove depth) of 41.5–209 μm. The cylinders were submerged in degassed water and optically imaged before and after ultrasound to visualize bubbles on the cylinders. The cylinders remained submerged while scanning with color Doppler at frequencies from 3.1 to 6.3 MHz with a General Electric Logiq E9 scanner and 9L linear array transducer. Two designs that showed twinkling characteristics were further examined. The presence or absence of bubbles on these designs was confirmed with microscopy, and the resulting twinkling behavior was investigated. This work shows strong evidence that both existing visible bubbles and either cavitation or ultrasound wave interactions with patterned or rough surfaces are significant factors in producing the twinkling signature.