Small knowledge of medical ultrasound probe
Ultrasound refers to sound waves with a frequency higher than 20,000 Hz that cannot be heard by humans. It has the characteristics of good directionality and strong penetrating ability. The frequency of ultrasound commonly used for medical diagnosis is 1 MHz to 5 MHz. The working principle of medical ultrasound examination has a certain similarity with sonar, that is, when ultrasound is emitted into the human body, it will reflect and refract when it encounters an interface in the body, and may be absorbed and attenuated in human tissue. Because the shape and structure of various tissues in the human body are not the same, so the degree of reflection, refraction and absorption of ultrasonic waves is also different. In addition, combined with anatomical knowledge, normal and pathological changes, it is possible to diagnose whether the examined organ is normal.
Medical ultrasound imaging requires three steps: transmitting sound waves, receiving reflected sound waves, and signal processing to obtain images.
1. Transmit ultrasonic waves through piezoelectric ceramic transducers (ultrasonic probes). Different probes can emit different frequencies of sound waves. The frequency of medical ultrasonic waves is generally 2-13MHz. The higher the sound wave frequency, the weaker the diffraction and the higher the imaging resolution. However, the higher the frequency, the faster the sound wave attenuation and the smaller the penetration depth. therefore,
1) When detecting the heart, only low frequency (2-4MHz) sound waves can be used to ensure the detection depth, but the imaging effect is poor;
2) When detecting the blood vessels below the epidermis such as carotid artery and femoral artery, use high frequency (10MHz) sound waves, and the imaging is clear and better.
2. It is still the same ultrasonic probe that receives the reflected wave. The piezoelectric ceramic transducer converts the acoustic wave signal into an electrical signal, and then performs signal processing through the host for imaging.
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