Discovery of Two Types of Twinkling Can Explain Contradictory Observations among Twinkling Artifact Investigators in Ultrasound Imaging

Twinkling Artifact is a valuable tool in detecting dense objects such as kidney stones, calculi etc., especially when there is no acoustic shadowing and presence of hyperechogenic tissues obstructs visualization. This phenomenon is not completely understood. Different scientific groups have contradictory findings concerning its properties: some of them observed a decrease in Twinkling intensity at elevated pulse repetition frequencies (PRF), while others found Twinkling to be independent from PRF, etc. In this paper we hypothesize that this kind of contradictions can be partially resolved on an assumption that there are two types of Twinkling. The 1st type presumably is produced by random-phased reflections from microcavitation and can be registered even at PRF high enough to suppress blood flow. The 2nd is originated from elastic vibrations as the object under investigation swings like a pendulum in the field of ultrasound. These vibrations can be associated with an external source such as a muscles contraction, etc. or the acoustic radiation force from signals emitted by the transducer. The 2nd type of Twinkling disappears at high PRF and can be regularly observed in silicone and polyurethane phantoms where the occurrence of cavitation microbubbles is highly unlikely. Key Words: Ultrasound Imaging, Twinkling Artifact, Stone Detection, Doppler Effect, Color Frame Mapping, Acoustic Radiation Force, Elastic Vibration, Ultrasound Phantom, Cavitation, Microbubbles.