GT6002 ultrasonic imaging comprehensive experimental instrument
Pulse echo type acoustic imaging experiment
I. Overview
1. The basic principle of ultrasound imaging
Ultrasonic imaging is acoustic imaging using ultrasound. It includes pulse echo acoustical imaging and transmission acoustical imaging. The former is a pulsed acoustic wave that receives its echo and obtains it. An acoustic imaging method for image of an object; the latter is an acoustic imaging method for obtaining an image of an object using transmitted acoustic waves. Currently, ultrasonic diagnostic instruments for clinical applications use pulse echo type acoustic imaging. Some imaging of transmissive acoustic imaging The method is still under study, such as some types of computed tomography by ultrasound. Currently studied with computed tomography of acoustic Velocity and computed tomography of acoustic attenuation (computed tomography of acoustic attenuation) .
The experimental instrument is a method and technology for obtaining visible images of the tissue properties and structures of an object by receiving and processing echoes carrying information on the tissue or structural properties of the object by using ultrasonic waves. Compared with other imaging technologies, the experimental instrument has its own method. The unique advantage is that other imaging can not be replaced.
2. General rules of ultrasound imaging
All pulse echo type acoustic imaging relies on echo to reflect the information of the object tissue, while the echo comes from the reflection of the tissue interface and the backscatter of the scatterer. The intensity of the echo depends on the reflection coefficient of the interface, the backscattering intensity of the particles and the attenuation of the tissue. .
The greater the difference in acoustic impedance between the tissues of the interface of the object, the stronger the echo of the reflection. The intensity of the reflection is also related to the angle of incidence of the beam. The smaller the angle of incidence, the greater the intensity of the reflection, and the beam perpendicular to the incident interface. That is, when the incident angle is zero, the reflected sound intensity is the largest, and when the incident angle is 90 degrees, the reflected sound intensity is zero.
The attenuation of the acoustic energy of the object tissue depends on the attenuation coefficient of the tissue on the sound intensity and the propagation distance of the sound beam (ie the detection depth). The attenuation characteristics of the object are mainly reflected in the echo of the rear.
Multiple reflection ultrasound encounters a strong reflection interface. After the interface, a series of evenly spaced images that are sequentially weakened are called multiple reflections. This is formed by multiple round trips between the probe and the interface.
Second, the purpose of the experiment
1. Understand the principle of pulse echo type acoustic imaging.
2. Master the use of pulse echo type acoustic imaging experiment instrument.
3. Using a pulse echo type acoustic imaging experiment instrument to perform imaging experiments on a given object.
Third, the experimental instrument
The GT6002 ultrasonic imaging comprehensive experimental instrument consists of the following components: GT6002 ultrasonic imaging integrated experimental instrument, ultrasonic transducer, circular rotating water tank, VC++ computer data processing software, data line and computer (self-provided).
1, GT6002 ultrasonic imaging comprehensive experimental instrument technical parameters and instructions for use
* The experiment instrument uses DSP processor, sampling frequency is 12.5M
* Ultrasonic sensor operating frequency: 2.5 MHz, transceiver integrated
* Distance between ultrasonic sensor and positioning/imaging object: 7 cm - 80 cm
* Positioning index Horizontal distance accuracy: ≤2.5cm; Bearing accuracy: ≤2.5o
* The instrument provides RS232 interface and is connected to the computer.
* Experimental content that can be completed: echo waveform observation; rotational scanning imaging experiment
Figure 1 GT6002 ultrasound imaging comprehensive experimental instrument
2, test stand
The experimental test stand consists of the following parts:
1) Pointer 2) Pole base 3) Angle scale 4) Ultrasonic sensor mount 5) Boom 6) Plexiglass drum 7) Pole 8) Knob 9) Rotating chassis, etc.
Specifically, as shown in Figure 2. When the test frame is installed, first unscrew the knob 8, remove the boom, and then install the ultrasonic sensor on the fixed seat and lock it; then put the boom into the bucket and re-open according to Figure 2. Screw on the knob.
3, the software interface
Figure 2 test stand
Figure 3 experimental operation interface diagram
Function key description:
Read data / save data - read and store the collected data.
Working mode - provide a total of imaging acquisition, and waveform two working methods; when imaging acquisition, you can set the rotation angle of imaging acquisition, which can be set to 1~6 °C, each time you press the imaging acquisition, the collection count will be collected. After the completion, it will automatically add 1 and press the count to reset. The acquisition count will be cleared. After the acquisition, it can be imaged according to the imaging operation. After 360°C, the imaging operation can be obtained according to the imaging operation.
Clear display - used to clear the displayed waveform or image.
Imaging operation function - image processing the collected data. When processing, you can adjust the image by increasing the threshold or decreasing the threshold and X zooming in/out, Y zooming in/out.
Signal amplification / signal reduction - zoom in and out on the display intensity of the received signal.
Serial communication - used to start and close the communication port. After startup, the serial port status displays OK!! or END, and closes to display Close!!.
Fourth, the experimental principle
The transceiver is integrated with the duplex ultrasonic transducer to complete the signal transmission and echo reception; the DSP processor is used to control the transmission and reception signals of the ultrasonic sensor and the high-speed acquisition, and the data is analyzed and processed based on the FFT transformation, and Processing data is transferred to the computer, and the computer software is used to display the measured echo waveform and generate a two-dimensional cross-sectional image of the object.
In this experiment, the basic principle of rotational imaging is used to collect the echo signals of various sections around the object to reconstruct the cross-sectional image: the specific method is to collect the echo signals of the object at regular angles and store the data; Obtain the cross-sectional imaging map. During the acquisition process, the measured imaging acquisition map can be seen. The structure of the object can be analyzed from the curve. The following figure 4 is the actual measurement map collected by two drums together:
The experimental device is mainly composed of the following parts:
1, experimental sink
The water tank is in the shape of a barrel with an inner diameter of about 480mm. It has a rotation angle indication function. The imaged object is placed in the middle of the water tank, and the ultrasonic transducer head is aimed at the object. By rotating the water tank, the surface of the object directly exposed by the ultrasonic probe is changed, and the surface structure is different. The echo signals will be different.
Fig. 4 The collected data of the two drums together
Figure 5 Transducer actual emission waveform and acceptance waveform
2. Ultrasound imaging experiment instrument
The experimental instrument is connected with the ultrasonic sensor. The ultrasonic sensor (transducer) adopts a single crystal quartz crystal structure with transceiving. The operating frequency of the transducer is about 2.5 MHz. The actual working principle of the experimental instrument is: the high speed D/ is controlled by the DSP processor. The A converter generates a frequency signal of 2.5 MHz, and the signal is amplified and processed and connected to the ultrasonic sensor as a transmitting wave; the transmitted wave will generate an echo signal after encountering different object tissues, and the echo signal is amplified and filtered by the high-speed operational amplifier. The signals received by the high-speed A/D are collected, and the FFT is used for data analysis and processing, and the data is transmitted to the computer.
3, computer analysis interface
After the collected data signal is transmitted to the computer, the computer can display the echo waveform;
Figure 6 Echo signals displayed by the computer after DSP data processing
At the same time, it can also perform point-to-point acquisition and data processing on the tissue echo signals of the whole object, and then draw the two-dimensional cross-sectional image of the object.
Fifth, the experimental content
(1) Observing the echo waveform of the imaged object
1. The transducer is mounted on the test stand and placed in the sink to adjust the transducer head to align the imaged object at the center of the sink.
2. Connect the transducer and the “sensor†socket on the front panel of the signal source, and connect the serial port on the rear panel of the instrument to the computer to turn on the power. Note: When powering on, make sure the transducer is in the water.
3. Open the computer software, use the left mouse button to click the serial communication button in the lower right corner of the display control screen, OK!! appears on the serial port status box, and then it becomes END, indicating that the serial port of the computer is open, and the data can be compared with the experiment instrument. Command communication.
4. Use the left mouse button to click the waveform button in the working mode box on the display control screen. The red waveform display is displayed below the working status, and the real-time waveform will be displayed on the screen.
5. Change the distance of the object from the ultrasonic sensor and observe the change of the echo waveform; horizontally rotate the transducer probe, change the incident angle of the transducer, and observe the echo waveform.
(II) Echo-type acoustic imaging experiment (rotary imaging)
1. The experimental steps are the same as (1) Steps 1~3 of observing the echo waveform of the imaged object.
2. Use the left mouse button to click the imaging acquisition button in the working mode box on the display control screen. The red image acquisition is displayed below the working status, and the image will be displayed on the screen.
3. First, aim the ultrasonic transducer at the center of the object, rotate the water tank to make the alignment scale 0 °C; set the rotation angle (sampling degree interval) t °C in the display control interface, press the imaging acquisition button to the object 0 °C The position is processed by imaging. If the acquisition count is not zero, you can press the count to reset.
4. Rotate the water tank every t °C and press the imaging button to perform imaging; rotate one turn in sequence to complete the 360 ​​measurement. The cross-sectional shape displayed after the measurement is the two-dimensional sectional view of the object.
5. According to the imaging treatment, the collected two-section image can be filled or smoothed.
6. After the acquisition is completed at 360 °C, press the serial port communication to stop receiving data, and store the measured data according to the stored data.
7. Read the stored data according to the read data, and adjust the imaging through the function of the imaging operation frame.
Figure 7 Glass processing diagram with handle
Figure 8 plexiglass drum imaging processing diagram
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