Final answer:
A high-contrast ultrasound image indicates a narrow dynamic range, meaning less variation between the brightest and darkest areas of the image and stronger reflections where there's a significant change in density.
Step-by-step explanation:
If an ultrasound image displays high contrast, it generally means that there is a greater difference between the brightest and the darkest parts of the image, implying stronger reflections at interfaces where there are significant changes in density. These strong reflections correlate with a narrow dynamic range, which indicates there are fewer gradations between the extremes of dark and light in the ultrasound image. In contrast, a wide dynamic range would show many shades of gray, representing more subtle differences in density and a gradation of echo intensities.
For example, a 3D ultrasound image of a fetus will show areas of high contrast where tissues of differing densities meet, resulting in fewer shades of gray and a narrower dynamic range. Conversely, if there are more gradual changes in density, the sound is less strongly reflected and the image will have a wide dynamic range with more shades of gray, giving a more detailed picture of the internal structures.