Type A Ultrasonic Diagnostic Apparatus
Type A ultrasonic diagnostic apparatus is the abbreviation for amplitude modulated mode. Type A display is the earliest and most basic way of applying ultrasound technology to medical diagnosis. It is mainly suitable for checking simple anatomical structures such as liver, gallbladder, spleen, eyes and brain, measuring line degree and obtaining the size and shape of echo amplitude, and obtaining tissue characteristic information by analyzing the distribution of echo amplitude.
Application scope in clinical diagnosis:
The A-type ultrasonic diagnostic apparatus can be used in many departments, and the most representative application is the measurement of the position of the brain midline. Generally, the midline position of the normal human brain passes through the geometric center of the skull, and the maximum deviation is ≤0.3cm. If the deviation of the midline of the brain is more than 0.3cm when measured with a double-track A-type diagnostic instrument, a space-occupying lesion should be considered. This method is painless and highly accurate. Outlook
The A-type diagnostic instrument is the earliest ultrasound equipment used in clinical practice. Due to the emergence of the B-type diagnostic instrument, the A-type diagnostic instrument has been on the verge of being eliminated, and is currently only used in brain midline measurement and ophthalmology. However, the A-type diagnostic instrument has high accuracy and specificity in the identification and determination of tissues (or tissue characterization) and biometrics. At present, only a few foreign manufacturers are producing standardized A-type diagnostic instruments.
B-type ultrasonic diagnostic apparatus
Fundamental:
Type B (brightnessmodulationmode) ultrasound is a brightness modulation type. Its principle is the same as that of type A. The differences are: ①Change the amplitude modulation display to the brightness modulation display, which sends the amplified echo pulse electrical signal to the display The cathode (or on the control grid) changes the brightness of the display with the size of the signal; ②The doctor diagnoses the disease based on the human body information obtained from the sound image, rather than the human body information reflected by the wave pattern like A-mode ultrasound.
The general B-ultrasound working process is: when the probe gets the excitation pulse, it emits ultrasound, (at the same time, the probe is controlled by the focus delay circuit to realize the acoustic focusing of the sound wave.) Then after a period of delay, the probe receives the echo signal reflected back. The received echo signal is processed by beamforming. Then the digital scan converter (DSC) circuit performs digital conversion to form a digital signal, and further image processing under the control of the CPU, and then synthesizes the video signal with the chart forming circuit and the measurement circuit and sends it to the display to form the familiar B-mode image. Also called two-dimensional black and white ultrasound image.
