Basic Principles
The Doppler Effect
The Doppler effect was first introduced by Austrian physicist Christian Johann Doppler in 1842. It describes the phenomenon in which the frequency of a light wave increases or decreases when there is relative motion between a light source and a receiver. The difference between the received frequency and the transmitted frequency caused by this relative motion is called the Doppler shift or Doppler effect.
Sound waves are also characterized by the Doppler effect, and Doppler ultrasound is best suited for the detection of moving fluids, so Doppler ultrasound is particularly important for the detection of blood flow in the heart and large vessels.
Basic modalities of Doppler echocardiography
1 Pulsed Doppler (PW)
2 Continuous Doppler (CW)
3 Color Doppler flow imaging (CDFI) (1) A-type ultrasound diagnostic instrument
A-type ultrasound is a kind of amplitude modulation type, which is the most popular and the most basic type of domestic ultrasound diagnostic instrument in the early period, and has been basically eliminated now. It has been basically eliminated.
(B) M-type ultrasound diagnostic instrument
M-type ultrasound is the use of glow modulation, to reflect the brightness of the echo strength, M-type display of the body's various layers of tissue for the body surface (probe) of the distance over time, is to reflect the spatial structure of a one-dimensional, M-type ultrasound is more often used to detect the heart, it is often referred to as the M-type echocardiogram, is now generally used as a two-dimensional color Doppler echocardiography instrument. A display mode is set on the instrument.
(C) B-type ultrasound diagnostic instrument
B-type display is the use of A-type and M-type display technology developed, it will be A-type amplitude modulation display to the brightness modulation display, brightness varies with the size of the echo signal, reflecting the human body tissues of the two-dimensional cross-section tomographic images.
The real-time section image displayed by type B is realistic, intuitive and easy to grasp. It is only 20 years of history, but the development is very rapid, the instrument is constantly updated, in recent years every year there are improvements in the new B type instrument, B type instrument has become the most basic and important equipment for ultrasound diagnosis. Currently more commonly used B-type ultrasound imaging modalities: scanning mode: linear (straight line) scanning, fan-shaped scanning, trapezoidal scanning, arc scanning, radial scanning, circumferential scanning, composite scanning; scanning drive mode: manual scanning, mechanical scanning, electronic scanning, composite scanning.
(D) D-type ultrasound diagnostic instrument
Ultrasonic Doppler diagnostic instrument referred to as the D-type ultrasound diagnostic instrument, this type of instrument is the use of the principle of the Doppler effect on the movement of the organs and blood flow detection. It is essential in the diagnosis of cardiovascular diseases. At present, ultrasound instruments used for cardiovascular diagnosis are equipped with Doppler, which is divided into pulsed Doppler and continuous Doppler. In recent years, many new topics are inseparable from the Doppler principle, such as peripheral blood vessels, blood vessels of internal organs and neoplastic tumors, etc., so now ultrasound is basically equipped with Doppler display mode.
(E) color Doppler blood flow imaging device
Color Doppler blood flow imaging is referred to as color ultrasound, including two-dimensional imaging and color imaging two parts. High-quality color display requires satisfactory black-and-white structural images and clear color flow images. On the basis of displaying two-dimensional section, turn on the switch of "color blood flow imaging", the signal of color blood flow will be automatically superimposed on the black and white two-dimensional structural display, and the speed display, variance display or power display can be selected according to the needs. At present, there are many types and models of color ultrasound on the international market, and the development of the grade is changing day by day, with more high information, high resolution, high automation, wide range, simple and practical characteristics.