Journal of Ultrasound in Medicine, Vol 9, Issue 5 255-260, Copyright © 1990 by American Institute of Ultrasound in Medicine
Color Doppler artifact in anechoic regions
D. G. Mitchell, P. Burns and L. Needleman
Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107.
For color Doppler imaging, several types of signal processing are employed
in order to produce acceptable images of blood flow in blood vessels while
suppressing color in moving solid tissue. The processing can produce an
artifact in which color may arise from noise or from tissue motion and fill
anechoic regions preferentially. This artifact may complicate the
differentiation of areas with blood flow from anechoic regions without
flow. By using four different color Doppler ultrasound units to image a
tissue-equivalent phantom containing anechoic cylinders, artifactual color
resulted when gain was raised sufficiently. This color was concentrated in
anechoic regions of a gray-scale image that did not contain flow. In two
instruments, this artifact was only observed when the transducer was
vibrated, simulating tissue motion. In these instruments, the
identification of low-frequency, high-amplitude Doppler signals is used to
locate moving solid tissue and so suppress color in these regions. In the
other two instruments, the presence of echoes within the image suppressed
the assignment of color. With both types of processing, color may appear
artifactually in echo-free regions without flow, such as fluid collections.
Presence or absence of flow should be confirmed by Doppler spectral
analysis. An understanding of the origin and appearance of artifactual
color can prevent its occurrence from detracting from the usefulness of
color Doppler imaging.
