Color Doppler ultrasound is a medical imaging technique which is used to provide visualization of the bloodflow, using color processing to add color to the image so that a doctor or care provider can clearly see what is happening inside the body. This technique requires the use of an ultrasound machine which is capable of color Doppler imaging, and can be performed in a hospital or clinic as an outpatient procedure. Having this imaging study performed is not usually painful, and the patient does not require sedatives.
Doppler ultrasound takes advantage of the Doppler effect to create a moving image of the inside of the body. In this technique, an ultrasound transducer is used to beam sound into the area of interest, and it reads the returning sound. When the sound bounces off a moving target like a blood vessel, the pitch changes as a result of the Doppler effect. The transducer can detect very subtle pitch changes and record them visually, creating an image which shows where blood is flowing, and in which direction.
Viewed in grayscale, the image can be a bit hard to read. This is where color Doppler ultrasound comes in, with the ultrasound machine assigning color values which depend on whether blood is moving towards or away from the the transducer. In addition to showing the direction of flow, the colors also vary in intensity depending on the velocity of the flow, allowing people to see how quickly the blood is moving.
One obvious application of color Doppler ultrasound is in examination of a patient with a suspected aneurysm or occlusion. The ultrasound will reveal areas where the velocity of the bloodflow is changing, acting like a red flag to point out a problem. This technique can also be used to find blood clots, which will also be clearly visible within the color display.
In examination of tumors and venous malformations, doctors can use color Doppler ultrasound to map out the blood supply and learn how far the growth has spread. This can have an impact on which treatments the doctor recommends, and how the doctor wants to approach surgery and other measures.
While color Doppler ultrasound usually involves using a transducer on the outside of the body, it can be used for transrectal and transvaginal procedures, in which the probe is inserted to get a better view. In these cases, patients may be given muscle relaxers so that the procedure will be less uncomfortable.