A Doppler ultrasound is a noninvasive diagnostic that uses circulating red blood cells to reflect high-frequency sound waves (ultrasound) to assess the blood flow via your blood arteries. Normal ultrasounds employ sound waves to create images, but they are unable to depict blood flow.

By monitoring the rate of change in pitch, a Doppler ultrasound may calculate how quickly blood flows (frequency). A sonographer with training in ultrasound imaging applies pressure to your skin with a tiny, hand-held instrument (transducer) roughly the size of a bar of soap across the area of your body being scanned, moving from one place to another as required.

As an alternative to more invasive treatments like angiography, which involves injecting dye into the blood arteries to make them visible on X-ray images, this test may be performed.