The color flash artifact is a commonly encountered artifact on color Doppler ultrasound, representing spurious flow signal arising due to tissue/transducer motion.
Physics
The flash artifact is caused by movement of reflective tissues (e.g. due to respiration), or the transducer, which generates a Doppler shift, and thus a color signal 1. Modern US devices utilize various noise/motion suppression techniques to minimize this artifact, nevertheless it remains omnipresent especially in anechoic structures where the motion discriminator algorithm cannot suppress it as easily 2.
Practical points
- A high color gain makes this ubiquitous artifact more prominent 1. In such cases even slight transducer movements can induce inhomogeneous color noise filling the entire color box. Reducing the gain can alleviate this to some extent, but may also remove the actual flow signal especially from slow flow blood vessels.
- In many cases the flash artifact can easily be reduced simply by slower fanning with the transducer during duplex color Doppler imaging. The flash artifact can make color Doppler interrogation of structures influenced heavily by respiratory/cardiac movements difficult, if not impossible. This is a commonly encountered problem e.g. in the evaluation of the left lobe of the liver.
- It is also good to bear in mind that anechoic structures (e.g. gallbladder, simple cysts) are more prone to produce flash artifacts than more echogenic tissues 1. This is caused by the color write priority, as in the absence of significant B-mode signal the spurious color signal caused by the artifact is erroneously displayed 2. In those rare cases where this poses a diagnostic difficulty, the color write priority setting of the scanner can be adjusted to reduce the artifact.