Figure 3a. Color Doppler US images of ice ball show twinkling artifact (arrows), which is a US artifact that occurs at highly reflective objects. Twinkling artifact appears as rapidly alternating red and blue color Doppler signal, which gives the appearance of movement, at surface of ice ball. No definite vascular flow was identified anterior to ice ball with color Doppler imaging. Amount of signal varies from (a) small or (b) moderate to (c) large.