Dopplers

Vascular Doppler ultrasounds and fetal Doppler ultrasounds are important medical devices that help diagnosis important health conditions.

Vascular Doppler ultrasound is a noninvasive diagnostic test used to determine the amount of blood flow moving through blood vessels by aiming high-frequency sound waves (ultrasound) at red blood cells. Fetal Doppler measures the heart rate and produces a sound, image or both.

Regular ultrasound uses sound waves to produce images of body structures that is picked up by the transducer/probe and a computer uses those sound waves to make an image such as that which is performed on babies in the uterus, for viewing the inside of a gallbladder, detecting kidney stones, or pericardial effusions. It can even be used to evaluate joints in conditions such as rheumatoid arthritis. Regular ultrasound can also have Doppler ability. Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions.

The term Doppler came from an Austrian physicist named Christian Doppler who discovered the Doppler Shift Principal in 1842. Sound waves from a moving object (the heart valves) can expand or be come compressed which changes the frequency. An example of sound waves changing pitch is witnessed when a train whistle passes. As the train is approaching someone, the pitch is higher and then becomes lower as the train goes away from the person.

The Doppler principle governs weather forecasting, radar, modern navigation, the motion of stars, and is thought to be part of the 'Big Bang' theory.

• A Doppler ultrasound can diagnose many conditions such as:
• Deep vein thrombosis
• Poorly functioning valves in your leg veins known as venous insufficiency due to the buildup of blood in the extremities
• Heart valve defects and congenital heart disease
• Arterial occlusion
• Peripheral artery disease
• Aneurysms
• Artery stenosis such as the carotid arteries

A Vascular Doppler ultrasound estimates the speed of blood flow by measuring the rate of change in its frequency. During a Doppler ultrasound, a sonographer applies a transducer to your skin over the area of interest. It is often the first test performed before more invasive ones. Dopplers may be inconclusive and may require angiography to gain definitive x-ray pictures of a vessel. If there is an area of suspicion that needs to be monitored after angiography, then Vascular Doppler is a useful tool to follow regression.

Types of Doppler Ultrasonography

Doppler ultrasound: Doppler ultrasound depends on the Doppler effect, which is a change in the frequency of a wave as a result of the motion of the red blood cells.

There are several kinds of Doppler ultrasound:

Vascular Dopplers (Hand-Held)

Hand-held versions have large, bright, back lit display of the pulse rate. The display also indicates battery, volume, and signal strength status. The powerful digital processor eliminates background noise and amplifies a strong clear signal. Auto-correlation calculates a fast, accurate pulse rate

• Color Vascular Doppler – is color coded (red or blue) information that estimates the average velocity of flow within a vessel depending on the direction of blood flow indicating flow to or from the ultrasound transducer.
• Pulsed Vascular Doppler –measures the amplitude of a signal displayed as a graph of the full range of velocities a specific point in time usually in shades of gray.
• Power Vascular Doppler -- depicts the power or amplitude of the sound signals rather than the frequency shift, but does not show speed or direction.

Fetal Dopplers measures the fetal heart rate and produces a sound, image or both on a handheld device with a probe that can be moved over the maternal abdomen. Fetal probes are different than vascular probes.