Diagnostic ultrasound ( PDFDrive )

26 PART I Physics
A
B
FIG. 1.38 Color Flow and Power Doppler. (A) Color low Doppler imaging uses a color map to display information based on the detection
of frequency shifts from moving targets. Noise in this form of display appears across the entire frequency spectrum and limits sensitivity.
(B) Power Doppler uses a color map to show the distribution of the power or amplitude of the Doppler signal. Flow direction and velocity information
are not provided, but noise is reduced, allowing higher gain settings and improved sensitivity for low detection.
A
B
FIG. 1.39 Frequency and Power Mode Color Mapping. (A) Conventional color Doppler uses the color map to show differences in low
direction and Doppler frequency shift. Because noise appears over the entire frequency spectrum, gain levels are limited to those that do not
introduce excessive noise. (B) Power Doppler color map, in contrast, indicates the amplitude of the Doppler signal. Because most noise is of low
amplitude, it is possible to map this to colors near the background. This permits the use of high gain settings that offer signiicant improvements
over conventional color Doppler in low detection.