The Use of Color Doppler to Diagnose and Grade Flow Pathology in Different Pathological Conditions

In this chapter, the reader is introduced to the Color Doppler. The normal pictures of the Color Doppler are described in the form of Schematic Diagrams. The changes that happen due to pathology are described next. The basic principle is that the Color Doppler records red color if the flow is towards the transducer. If away from the transducer, the color is blue. This is true only if the flow is streamline as in normal conditions. Turbulent flow gives usually a mosaic pattern of a greenish yellow color. Color Doppler has a Sample Volume similar to Pulse Wave Doppler and hence suffers from the disadvantage of Aliasing. That is, if the velocity of flow of blood is more than half the PRF, the normal red color is recorded as blue and vice versa. The jet of the Color Doppler gives a semi quantitative assessment of the severity of the lesion may it be stenosis or regurgitation. If the Cursor cuts across the flow of blood exactly perpendicularly, a dark image is obtained and no color is registered as in the Color Doppler recording of the Arch of Aorta.