Doppler Effect in Medical Imaging Technology

 

The application of the Doppler effect has a great role in medicine, and is also the focus of medical imaging majors in the medical profession.

 

Doppler ultrasound is a medical ultrasound examination that uses the Doppler effect to generate motion imaging of tissue and body fluids (usually blood) and their relative velocity to the probe. By calculating the frequency shift of a particular sample volume, such as flow in an artery or blood flow on a heart valve, its speed and direction can be determined and displayed. Color Doppler or color Doppler flow is displayed by the color scale. 

 

Color Doppler images typically incorporate grayscale (B-mode) images to display two-sided ultrasound images, allowing simultaneous visualization of the anatomy of the area. This is particularly useful in cardiovascular studies (ultrasonography of the vascular system and heart) and is indispensable in many areas, such as determining the hepatic vascular reversal blood flow in portal hypertension.

 

 

Operating

 

Doppler information is displayed using a spectral Doppler pattern, or Doppler information is displayed using color Doppler (directional Doppler) or power Doppler (non-directional Doppler). This Doppler shift falls within the audible range and is typically heard using stereo speakers: this produces a very unique synthetic pulsation sound.

 

All modern ultrasound scanners use pulse Doppler to measure speed. Pulse wave machines emit and receive a series of pulses. The frequency shift of each pulse is ignored, but the frequency shift is obtained using the relative phase change of the pulse (since the frequency is the rate of change of the phase). 

 

The main advantage of pulse-wave Doppler (= PW Doppler) in continuous wave (= CW Doppler) is that distance information is obtained (the time between the transmitted pulse and the received pulse can be converted into the distance from which the speed of sound is known) and gain Fix the application. The disadvantage of pulsed Doppler is that the measurement results may appear aliased. The terms Doppler ultrasound and Doppler ultrasound have been accepted for pulsed and continuous Doppler systems, although the mechanisms for measuring velocity differ.

 

It should be noted that there is no standard for color Doppler display. Some laboratories display arteries as red and veins as blue. As medical illustrators often show, some blood vessels may have some blood vessels flowing to the sensor and some blood vessels may flow out of the sensor. This causes the vascular part to be a vein and partly an illogical appearance of the artery. Other laboratories use red to indicate the flow to the transducer and leave the blue color out of the transducer. 

 

There are also some other labs that prefer to display ultrasonic Doppler color maps that are more in line with previously published physics: the red shift represents the longer echo (scattering) of the blood away from the transducer; and the blue color represents the flow from the flow The blood of the reflector reflects the short wave of the echo. Due to this confusion and lack of standards in various laboratories, ultrasound physicians must understand the basic acoustic physics of color Doppler and the physiology of normal and abnormal blood flow in humans.