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Ultrasound equipment need to understand what parameters
Currently ultrasound equipment brands, how to choose to own a machine favored in price, performance, usage , etc., as relevant now elaborate on the parameters of ultrasound equipment purchases :

A clinical application scope and focus : ultrasound applied to the abdomen, heart , superficial organs, peripheral vascular , endovascular , and intraoperative angiography . Currently there are systemic classification machine, obstetrics and gynecology with abdominal machines, used machines superficial vascular organ , heart machine , to seek the brand and model as needed. If GE VIVID series specializes in cardiac ; Madison abdominal machine for the strength of obstetrics and gynecology , cardiac function is weak .
Japanese brand machines in terms of image quality plus the abdomen , but because of its technical weaknesses, less ideal model of cardiac imaging .

2 Probe : Convex array types , linear array , phased array , cavity volume , intracardiac catheter probe, transesophageal probe.
The availability of broadband multi-frequency variable frequency technology, whether harmonic imaging features are supported .

3 -dimensional gray-scale imaging system
1 ) digital beam forming technology
2 ) transmit / receive channel number
3 ) receives the ultrasonic signal dynamic range
4 ) Scan line density
5 ) probing depth
6 ) frame rate
7 ) whether to support the organization and contrast harmonic imaging
8 ) composite imaging technology
9 ) tissue Doppler
10 ) and a variety of coded excitation pulse control imaging technology
11 ) Grayscale flow imaging technology
12 ) linear array probe trapezoid imaging technology
13 ) widefield imaging technology

4 spectral Doppler imaging system
1 ) Doppler type : PW, CW, HPRF etc.
2 ) Display
3 ) Movie playback time
4 ) Measurement speed: Max / Min

5 color flow imaging system
1 ) flow imaging mode
2 ) color flow display: speed chart , the energy map, speed energy diagrams
3 ) color display angle
4 ) color display frame rate

6 three-dimensional imaging
1 ) -dimensional real-time 4D imaging technology
2 ) three-dimensional imaging : tissue , blood vessels, surface

7 . Organization optimization and processing technology
1 ) pixel optimization, speckle noise removal techniques
2 ) adaptive scan control technology
3 ) display optimization technology to automatically organize

8 . Measurement and analysis functions
1 ) general measurement function
2 ) Doppler flow measurement and analysis
3 ) Measurement and analysis of cardiac function

9 digital data and image storage / management / transmission system
1 ) File information management system: report file storage, image storage format selection , storage media : HD, FD, MOD, CD, DVD.
2 ) Digital Communication System : Video printer interface ; external monitor machine interfaces ; Recorder Interface ; DIMCOM3.0 interfaces ; USB interface.

The main performance parameters of the ultrasonic diagnostic apparatus

( A ) blind

Blind spot is the most recent target depth echo B- device can recognize. It will help the small blind checked out close to the surface of the lesion , the performance depends on the characteristics of the amplifier and variable aperture technology offerings can . Further reducing the amplitude of the pulse launched into the amplifier and the amplifier time constant adjustment will affect the size of the blind .
However, plus a water balloon transducer test, the blind meaningless .

(B ) probing depth

         B- device normally displayed in the image , the maximum allowable sensitivity and brightness conditions , the observed maximum depth is called the target echo detection depth . The higher the value , the more checks in vivo wider .
Factors that affect the performance of the following reasons :
1 .
The sensitivity of the transducer
Transducers for transmitting and receiving ultrasonic waves in the process to achieve the electric and acoustic → → acoustic -electric conversion efficiency. The higher the sensitivity , the greater the depth of investigation .
Sensitivity depends on the match situation and the electromechanical properties of the wafer acoustic transducers , electrical matching layers.
2 transmit power
Improved transducer radiated sound power can be increased probing depth . However, to be increased to improve the acoustic power emitted voltage circuit.
This is not only difficult to machine design and acoustic power must be limited to within safe dose threshold , the technical indicators it safe dose intensity threshold used to indicate that the sound intensity should not exceed 10mW/cm2.
3 receiver amplifier gain
Improve the receiving amplifier gain can be increased probing depth .
However, the amplifier gain increases , the amplified echo signal is weak , but also noise signal amplification system , which make it useful in the noise signal , the gain should be moderate.
4 Operating Frequency
Sound attenuation coefficient and frequency vivo tissue into a linear relationship . The lower the frequency, the longer the wavelength , the smaller the attenuation of the amplitude , the greater the depth of the probe , but the resolution deteriorates . In contrast , the higher the frequency , the smaller the probing depth , but the resolution changed for the better . In order to improve the performance of the machine , in general, dynamic frequency scanning and dynamic tracking filter technology that enables high resolution and depth of investigation to combine applications.
Nevertheless, in order to meet clinical needs , the need to design the transducer is still different frequencies in different parts of the organism to diagnose .

( C) the axial resolution ( vertical resolution )

        Refers to the minimum distance along the beam axis direction , the B- picture display can distinguish two echoes goals. The smaller the value , the sharper the bedding sonographic longitudinal interface. For continuous wave, the theoretical attainable resolution equal to half a wavelength. Thus , the higher the frequency , the better the resolution . Since the biological tissue is not identical to the target interface , so the actual value of the theoretical resolution can not be achieved , but the equivalent value of 2 to 3 wavelengths . Effective pulse ultrasonic pulse echo system , the axial resolution ultrasound pulses (duration ) related. The narrower the pulse , the better the axial resolution , in order to improve this characteristic, the transducer is currently widely used in multilayer optimum impedance matching technology while improving the characteristics , in order to ensure a steep leading edge , each of the receiving amplifier
manufacturers have adopted the best dynamic tracking filter .

(D ) the lateral resolution (horizontal resolution )

        Means for scanning the ultrasound beam in a plane perpendicular to the direction of the beam axis can be distinguished on the minimum distance between the target echo . The smaller the value , the sharper the transverse sonogram bedding interface .
The factors include :
1 .
Beam width
The narrower the beam , the better the lateral resolution . The beam width and diameter of the wafer and working frequency. However, the size of the transducer can not do much , the frequency can not be infinitely high .
Therefore, the designer taking lens, a variable aperture techniques in the design and application of a dynamic focus segmented continuous dynamic focus , thereby improving lateral resolution .
2 system dynamic range
Directional sound field generated by the transducer , the sound pressure ( or intensity ) is not evenly distributed.
Such a general rule, the gain with the lifting beam width is widened and narrowed accordingly , and the transverse dimension of the target echo pan elongated and shortened accordingly .
3 medium display brightness and attenuation coefficient
Display brightness and medium attenuation coefficient will affect the lateral resolution, so when measuring the lateral resolution , gain and brightness sure to equipment transferred to the best condition .

(E ) shows the geometric position error

        Refers to the actual target size and accuracy of the distance measurement and display of the B- device .
In practice the main longitudinal measurement
Geometry showing error and horizontal geometry showing error . The technical parameters for measuring in vivo tumor size is very influential , related to the diagnosis and treatment of consistency.
Factors affecting the accuracy of the speed of sound settings and scan uniformity of law in the form of the relevant sector of the image, it worse than the accuracy of the linear array scanning plane geometry .

( Six ) beam slice thickness

        Refers to linear , convex array and phased array thickness in the direction perpendicular to the scanning plane transducer . The thinner the slices , the picture becomes clear, on the contrary would lead to image compression , resulting in artifacts. Slice thickness and the natural frequency depends on the size of the minor axis direction of the wafer .
Solution: usually focused acoustic lens in front of the installation and the use of chip technology in the whole of focus .

( Seven ) contrast resolution

        Refers to the smallest difference can be detected in the image of the echo amplitude. Better contrast resolution , the stronger the layering of the image, the more rich details , the picture becomes soft and delicate .
This factor causes , depending on the bandwidth of the acoustic signals and display gray-scale circuit.

( Eight ) working frequency, bandwidth , repetition rate

1 .
Operating Frequency
Operating frequency is the frequency of the ultrasonic probe launch , both with the natural frequency of the probe crystal , but also with other parameters related to the transmitter oscillator circuit .
2 .
In the pulse-echo system is emitted ultrasonic pulse , which is only a short burst duration. According to the spectrum analysis, a pulse contains many harmonics, i.e., a frequency band having a width ; contains many harmonics of the broadband is called the bandwidth ; maximum energy concentrated near the center frequency. Also can be inferred : When the pulse frequency is 1.MHz , the duration of its burst only 1μs ( microseconds ) ; while the actual pulse B -type ultrasonic diagnostic apparatus ( work ) frequency is greater than 1.MHz , the duration is less than 1μs ( microseconds ) .
3 .
Repetition frequency
Diagnostic ultrasound is emitted ultrasonic pulse signal ; transmitting at a predetermined time interval to repeat the same pulse signal , the repetition period of this time interval is called the T, the number of pulses per second is called a repetition frequency occurs F, known as pulse duration of the pulse
width W.
Repetition frequency is smaller, deeper probing depth ultrasound .
Transmitting ultrasonic pulse bandwidth ( band ) is wider, the higher the longitudinal resolution .

(Ix ) transmit power

        Improved transducer radiated sound power can be increased probing depth . However, to be increased to improve the acoustic power emitted voltage circuit. This not only brings difficulties to machine design and sound power must be restricted within the safe design and use of a threshold dose , especially for fetuses and children to reduce and prevent the use of ultrasound for inspection of rabbits , you must use a low -power ultrasonic diagnosis when necessary
Miriam ; ultrasonic transmitter power technical indicators used to represent sound intensity , sound intensity ultrasound diagnostic apparatus shall not be greater than 10mW/cm2.
        The ultrasonic diagnostic apparatus transmit power , and the electromechanical conversion factor of the probe wafer , a transmitting circuit and the transmitting capacity of the storage capacitor of the pulse repetition frequency is proportional and inversely proportional to the chip area of ​​the probe .

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