FujiFilm VisualSonics Vevo MD User Manual page 261

Persistence applies a pixel averaging algorithm to the most recently acquired frames
to produce a more uniform view of the faster moving tissue in the image data.
Persistence reduces distracting artifacts such as shimmering.
Tap the Persistence button and use the Up and Down buttons to cycle through the
available options: Off, Low, Med, High, and Max.
Note: Options available vary depending on the transducer type.
Controls in Color Doppler Mode 261