A-mode ultrasonography

A-type ultrasound is a type of classification in ultrasound examination. Type A ultrasound diagnosis is ultrasonic oscillometric diagnosis, that is, amplitude modulation type ultrasound. It uses the reflection characteristics of ultrasound to obtain relevant information in human tissues to diagnose diseases. This method is commonly used in clinical practice to measure the distance of the tissue interface, the diameter of the organ, and to detect the size and extent of the liver, gallbladder, spleen, kidney, uterus and other organs, and also for the exploration of ophthalmology and craniocerebral diseases. At present, many diagnostic items for type A ultrasound have gradually been replaced by type B ultrasound. However, it is useful for the detection of the midline of the brain, the measurement of the axial axis, the diagnosis of serous effusion, the diagnosis of hepatic abscess, and the location of puncture drainage. Because of its simplicity and low cost, it still has practical value that cannot be ignored. Basic Information Specialist classification: growth and development check classification: ultrasound Applicable gender: whether men and women apply fasting: not fasting Tips: When checking, you need to actively cooperate with the doctor's work. Normal value The state of the tissue is judged based on the height, the number, and the shape of the echo amplitude. There is no specific standard, and the diagnosis should be based on the location of the specific examination and the experience of the doctor. Clinical significance Abnormal results of heart disease, liver ascites, gallstones, kidney stones, serous effusion and other diseases. People who need to be examined have people with the above diseases. Precautions Taboo before the examination: poor rest, improper diet, excessive fatigue. Requirements for inspection: Actively cooperate with the doctor's work. Inspection process The patient takes the supine position, and the doctor scans with an ultrasonic probe to obtain scan data and images for analysis and diagnosis. 1. The working principle of type A ultrasound system. The A-type one-way ultrasonic diagnostic apparatus is composed of a main control circuit, a transmitting circuit, a high frequency signal amplifier, a compensation circuit, a detector, a video signal amplifier, a time base circuit, an oscilloscope, and a transducer. The main control circuit generates a sync pulse signal of the trigger reflection circuit and the time base scan circuit. Increasing the repetition frequency of the sync signal increases the brightness of the screen, but the repetition frequency is too high and the depth of detection is limited. At present, most of the repetition frequencies of 400 to 1000 Hz are used, and the lowest is 50 Hz. When the transmitting circuit is triggered by the synchronizing signal, a high-frequency electric oscillation with a duration of 1.5 to 5 μs is generated. The amplitude and duration of the output pulse can be adjusted by a potentiometer connected in parallel at the output. The receiving circuit includes three parts: a high frequency amplifier, a detector and a video amplifier, and some instruments are added to the compensation circuit. In the receiving circuit, there are gain and suppression two adjustment knobs. The gain knob is used to adjust the amplification factor of the output. The suppression knob is used to adjust the threshold level to remove unwanted wavelets below the threshold without affecting the signal above the threshold. The echo signal is finally amplified by the video amplifier to a sufficient amplitude and sent to the Y-axis deflector of the oscilloscope to produce a Y-direction offset. The magnitude of the offset is roughly proportional to the signal size. The time base circuit generates a sawtooth wave voltage that is amplified to a sufficient amplitude by the subsequent stage and sent to the X-axis deflection plate of the oscilloscope tube to generate a scan line. The repetition frequency of the sawtooth wave is determined by the master control circuit. Generally in the range of 400 to 1000 Hz. The speed of the sawtooth voltage change (ramp speed) is related to the depth of detection. The slower the change, the deeper the maximum depth of detection. The depth adjustment or ratio adjustment of the instrument is to adjust the slope of the sawtooth voltage. 2. Characteristics and limits of type A ultrasound. Ultrasound diagnosis of type A (amplitude modulation mode) is ultrasonic oscillometric diagnosis, that is, amplitude modulation type ultrasound. It uses the reflection characteristics of ultrasound to obtain relevant information in human tissues to diagnose diseases. When the ultrasonic beam propagates in the human tissue to encounter two layers of adjacent media interfaces with different acoustic impedances, a reflected echo is generated at the interface, and each time an interface is encountered, an echo is generated, which echoes on the oscilloscope screen. The form shows that the higher the acoustic impedance difference of the medium on both sides of the interface, the higher the amplitude of the echo; on the contrary, the smaller the acoustic impedance difference of the medium on both sides of the interface, the lower the amplitude of the echo. If the ultrasonic wave propagates in a uniform medium without an interface, that is, when the acoustic impedance difference is zero, an echo-free flat section is present. The state of the tissue is judged based on the height, the number, and the shape of the echo amplitude. Not suitable for the crowd Generally no taboos. Adverse reactions and risks Generally not.

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