The twinkle artifact (also sometimes referred to as the color comet tail artifact) is a color doppler phenomenon that appears as a rapidly changing mixture of color around a stationary object- often times around ureteral stones.
A couple of theories have suggested that the “twinkle” occurs either because of a strongly reflective medium with a rough surface (Rahmouni et al.) or because of a narrow band of intrinsic sonographic machine noise generated by slight random time fluctuations in the path lengths of transmitted and reflected acoustic waves (Kamaya et al.) Ahmad et al. took a look at this sign and determined that the color Doppler twinkling sign can aid the gray scale ultrasound detection of a urinary calculus, especially if the stone is undistinguishable from the surrounding structures or lacks a posterior acoustic shadow. (doi:10.1016/j.ejrnm.2014.01.013)