CN101690671A - Dynamic demodulation device of Doppler ultrasonic imaging system - Google Patents
Dynamic demodulation device of Doppler ultrasonic imaging system Download PDFInfo
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- CN101690671A CN101690671A CN200910190768A CN200910190768A CN101690671A CN 101690671 A CN101690671 A CN 101690671A CN 200910190768 A CN200910190768 A CN 200910190768A CN 200910190768 A CN200910190768 A CN 200910190768A CN 101690671 A CN101690671 A CN 101690671A
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Abstract
The invention discloses a dynamic demodulation device of a Doppler ultrasonic imaging system, which comprises a digital beam forming module and an orthogonal demodulation module which are connected. The dynamic demodulation device also comprises a dynamic frequency orthogonal signal generation module, wherein the dynamic frequency orthogonal signal generation module is connected with the orthogonal demodulation module, and is used for generating a cosine local oscillatory signal and a sine local oscillatory signal of which frequencies are changed with a beam propagation time and transmitting the signals to the orthogonal demodulation module. The dynamic demodulation device of the Doppler ultrasonic imaging system in the invention can compensate the attenuation of ultrasonic echo signals in human tissue so as to reduce errors of Doppler frequency shift signals.
Description
Technical field
The present invention relates to the supersonic imaging apparatus technical field, be specifically related to dynamic demodulation device of Doppler ultrasonic imaging system.
Background technology
In Doppler ultrasonic image-forming system, reflection and decay can take place in the communication process of these ultrasonic pulses in human body in a series of supersonic coherent train of pulse of probe emission.The ultrasonic echo of probe recipient soma and blood flow emission simultaneously amplifies after changing the signal of telecommunication into, carries out AD conversion and digital beam then and synthesizes (beamforming).Signal one tunnel after wave beam is synthetic is used for doing the B mode imaging, generates two-dimentional tissue image; Doppler's relevant treatment is carried out on another road, generates blood-stream image.And the data of generation blood flow imaging at first will be carried out quadrature demodulation and be handled.
As shown in Figure 1, with wave beam the echo-signal after synthetic with two orthogonal local oscillation signal (cos (ω
0T) and sin (ω
0T)) multiply each other after, obtain I and Q two-way restituted signal.The purpose of demodulation is to extract from echo-signal that people's in-vivo tissue or blood flow move and the doppler shifted signal that produces; And the purpose of using quadrature demodulation is that the differentiation Doppler signal is positive frequency deviation or negative sense frequency displacement.
In Doppler ultrasonic image-forming system, the frequencies omega that the frequency of the employed orthogonal local oscillation signal of demodulation is common and ultrasound emission encourages
0Identical.But because tissue is relevant with supersonic frequency in fact to the decay of ultrasonic signal, the variation relation of the attenuation quotient same frequency in the tissue can be described with power function, can be reduced to α on the engineering
DB=0.7dB/[MHzcm].So work as with ω
0When in human body, propagating, because there is bigger attenuation quotient in radio-frequency head branch than low frequency part, so its mid frequency can change for the impulsing string of mid frequency.Be that the degree of depth is dark more, mid frequency is low more.In the B mode imaging, the variation that the echo-signal after can synthesizing wave beam usually uses the technology of dynamic filter to come compensating frequency.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of dynamic demodulation device of Doppler ultrasonic imaging system, overcome prior art and when quadrature demodulation, can't compensate the decay of ultrasound echo signal in tissue, thereby cause the excessive defective of doppler shifted signal error.
The present invention solves the problems of the technologies described above the technical scheme that is adopted to be:
A kind of dynamic demodulation device of Doppler ultrasonic imaging system, comprise digital beam synthesis module and quadrature demodulation module, described digital beam synthesis module links to each other with described quadrature demodulation module, also comprise dynamic frequency orthogonal signalling generation module, described dynamic frequency orthogonal signalling generation module links to each other with described quadrature demodulation module, and described dynamic frequency orthogonal signalling generation module is used for cosine local oscillation signal and the sinusoidal local oscillation signal that generated frequency changes with the beam propagation time and sends to described quadrature demodulation module.
Described dynamic demodulation device of Doppler ultrasonic imaging system, the frequency f c with beam propagation time t variation of wherein said cosine local oscillation signal and sinusoidal local oscillation signal
(t)Calculate according to following formula:
fc
(t)＝f
0-2*(α
dB/8.6886)*(c
0*t)*(B/2.36)
2，
Wherein: f
0Be the mid frequency that Doppler ultrasonic image-forming system transmits,
α
dB＝0.7dB/[MHz·cm]，
c
0＝1540m/s，
B is the bandwidth that Doppler ultrasonic image-forming system transmits.
Described dynamic demodulation device of Doppler ultrasonic imaging system, wherein also comprise gain control digit time TGC module, described digital beam synthesis module links to each other with described gain control digit time TGC module, and described gain control digit time TGC module links to each other with described quadrature demodulation module.
Described dynamic demodulation device of Doppler ultrasonic imaging system, wherein said dynamic frequency orthogonal signalling generation module comprises dynamic frequency maker and digital frequency synthesizer, described dynamic frequency maker links to each other with described digital frequency synthesizer, described dynamic frequency maker is used to generate the frequency that changes with the beam propagation time, and described digital frequency synthesizer is used to generate corresponding cosine local oscillation signal and the corresponding sinusoidal local oscillation signal that changes with described frequency and beam propagation time.
Described dynamic demodulation device of Doppler ultrasonic imaging system, wherein said dynamic frequency maker is made as field programmable gate array FPGA.
Described dynamic demodulation device of Doppler ultrasonic imaging system wherein calculates corresponding described frequency according to Doppler ultrasonic image-forming system and be stored in the described dynamic frequency maker pulse-recurrence time.
Described dynamic demodulation device of Doppler ultrasonic imaging system, wherein said digital frequency synthesizer is made as field programmable gate array FPGA.
Described dynamic demodulation device of Doppler ultrasonic imaging system wherein is provided with look-up table in described digital frequency synthesizer, according to the described frequency and the phase value in the different moment, search the cosine value and the sine value of described phase value correspondence from described look-up table.
Beneficial effect of the present invention: dynamic demodulation device of Doppler ultrasonic imaging system of the present invention can compensate the decay of ultrasound echo signal in tissue, thereby reduce the error of doppler shifted signal.
Description of drawings
The present invention includes following accompanying drawing:
Fig. 1 is a prior art Doppler ultrasonic image-forming system sketch map;
Fig. 2 is a dynamic demodulation device of Doppler ultrasonic imaging system sketch map of the present invention;
Fig. 3 is two of dynamic demodulation device of Doppler ultrasonic imaging system sketch map of the present invention;
Fig. 4 is a dynamic frequency orthogonal signalling generation module sketch map of the present invention.
The specific embodiment
With embodiment the present invention is described in further detail with reference to the accompanying drawings below:
The present invention is based on following principle: when under linearity condition, spectrum envelope is the ultrasound wave of Gaussian function when propagating in human body, and its mid frequency can be described by following formula with the relation of propagation distance:
Fc=f
0-2 α z σ
2Formula 1
Wherein fc represents the mid frequency of ultrasound echo signal, and unit is MHz; f
0Be the mid frequency of transmit burst, unit is MHz; α is the attenuation quotient of ultrasound wave at human body, and unit is Neper/ (cm*MHz), and wherein Neper is the napier of unit of the sound intensity; Z represents the distance of beam propagation, and unit is cm; σ
2It is the variance of transmit burst frequency spectrum.
The frequency spectrum variance is σ
21/2 amplitude bandwidth of train of pulse frequency spectrum can provide by following formula:
B=2.36* σ formula 2
Consider again to work as ultrasound wave with speed c
0When=1540m/s propagated in human body, the pass of its time and propagation distance was:
T=z/c
0Formula 3
And be the attenuation quotient α and the α of unit with Neper/ (cm*MHz)
DBConversion:
α=α
DB/ 8.6886 formulas 4
Composite type 1-4 is when mid frequency is f
0And bandwidth is the ultrasonic pulse string of B when propagating in human body, and the mid frequency fc pass in time that can draw under the different depth is:
Fc
(t)=f
0-2* (α
DB/ 8.6886) * (c
0* * (B/2.36) t)
2Formula 5
According to formula 5, and ω
(t)=2 π fc
(t), realize quadrature demodulation module as shown in Figure 2.Different with scheme shown in Figure 1 is the time dependent local oscillation signal of frequency of utilization (cos (ω
(t)T) and sin (ω
(t)T)) local oscillation signal (cos (ω of replacement fixed frequency
0T) and sin (ω
0T)) come the demodulation ultrasound echo signal.The quadrature demodulation module is made of two multipliers, and echo-signal is multiplied each other with two local oscillation signals respectively, obtains I and Q two paths of signals, can judge the direction of blood flow by the phase relation between I and the Q.If the output phase of the output phase hysteresis Q passage of the demodulation of I passage illustrates that then this doppler shifted signal is positive frequency deviation signal (a blood flow direction flow direction probe); If the output phase of the leading Q passage of the output phase of the demodulation of I passage illustrates that then this doppler shifted signal is reverse frequency shift signal (blood flow direction is away from probe).And, increased dynamic frequency orthogonal signalling generation module among Fig. 2 in order to produce dynamic local oscillation signal.Its effect is the time (promptly at different depth locations) of propagating in human body according to ultrasound wave, and the orthogonal signalling that produce different frequency are used for demodulation.
Specific embodiment:
As shown in Figure 2, the digital beam composite part is addition after different time-delay of the echo-signal process after a plurality of (for example 32) receive path AD is changed and the weighting, forms a wave beam, thereby improves the signal to noise ratio of system.Numeral TGC its essence is a multiplier, thus the echo letter with wave beam after synthetic with tissue under the different multiplication compensation different depths to the decay of ultrasonic signal.Usually these coefficients preset, and select different coefficients according to the degree of depth of echo, and the degree of depth is dark more, and coefficient value is big more, thereby can compensate the exponential damping of echo amplitude.The effect of low pass filter be filtering multiply each other gained with the frequency signal, and remaining difference frequency signal promptly is required doppler shifted signal.
As shown in Figure 4, the core of dynamic demodulation is to produce dynamic local oscillation signal (cos (ω
(t)T) and sin (ω
(t)T)), dynamic frequency orthogonal signalling generation module can be realized by field programmable gate array FPGA.It is divided into dynamic frequency maker and digital frequency synthesizer two parts.
According to formula 5, f
0For the mid frequency of impulsing string, as 3.5MHz; B is the frequency spectrum 1/2 amplitude bandwidth of impulsing string, and the pulse number of this parameter and transmit burst has relation.If obviously the bandwidth of many its frequency spectrums so of pulse number is also narrow, the skew of frequency also can be also little when propagating in tissue; But how pulse number can cause the reductions of resolution, and can increase the increase to the radiating energy of human body, may have the problem of secure context.So should compromising, pulse number considers to get the acceptable value of everyway.α
DB=0.7dB/[MHzcm] and c
0=1540m/s.
Because the parameter in the formula 5 is the running parameter except hyperacoustic propagation time, all the other parameters are all definite when ultrasonic emitting, and should reduce the operation of multiplication and division during programmable gate array FPGA realizes at the scene as far as possible, so the dynamic frequency maker at the scene among the programmable gate array FPGA an available dynamic ram realize.Be 260us the pulse-recurrence time of supposing ultrasonic system, 260us can be divided into 128 sections, and every so approximately 2us (260us/128) is for a local frequency.The local frequency of each time period correspondence can be precomputed so and, and to have the degree of depth of field programmable gate array FPGA be in 128 the dynamic ram.When handling in real time, in the time that human body is propagated, from dynamic ram, find out corresponding local frequency and get final product according to ultrasound echo signal.
The generation of orthogonal local oscillation signal is to use the method for Direct Digital synthetic (DDS, Direct DigitalSynthesizer) to realize.One sine and cosine look-up table is arranged in the dynamic frequency maker, frequency according to the generation of dynamic frequency maker, and different constantly phase values, from look-up table, finding out the cosine value and the sine value of this phase place correspondence, the orthogonal local oscillation signal that generates different frequency is used for demodulation.
What use in this example is the implementation method of field programmable gate array FPGA, can realize the present invention on the different components such as MCU at DSP in addition certainly.In addition, as shown in Figure 3, when not needing amplitude to ultrasonic echo to compensate, can remove gain control digit time TGC (Time Gain Control) module, directly the echo-signal after synthetic is carried out dynamic demodulation with wave beam.
Those skilled in the art do not break away from essence of the present invention and spirit, can there be the various deformation scheme to realize the present invention, the above only is the preferable feasible embodiment of the present invention, be not so limit to interest field of the present invention, the equivalent structure that all utilizations description of the present invention and accompanying drawing content are done changes, and all is contained within the interest field of the present invention.
Claims (8)
1. dynamic demodulation device of Doppler ultrasonic imaging system, comprise digital beam synthesis module and quadrature demodulation module, described digital beam synthesis module links to each other with described quadrature demodulation module, it is characterized in that: also comprise dynamic frequency orthogonal signalling generation module, described dynamic frequency orthogonal signalling generation module links to each other with described quadrature demodulation module, and described dynamic frequency orthogonal signalling generation module is used for cosine local oscillation signal and the sinusoidal local oscillation signal that generated frequency changes with the beam propagation time and sends to described quadrature demodulation module.
2. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 1 is characterized in that: the frequency f c with beam propagation time t variation of described cosine local oscillation signal and sinusoidal local oscillation signal
(t)Calculate according to following formula:
fc
(t)＝f
0-2*(α
dB/8.6886)*(c
0*t)*(B/2.36)
2，
Wherein: f
0Be the mid frequency that Doppler ultrasonic image-forming system transmits,
α
dB＝0.7dB/[MHz·cm]，
c
0＝1540m/s，
B is the bandwidth that Doppler ultrasonic image-forming system transmits.
3. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 2, it is characterized in that: also comprise gain control digit time TGC module, described digital beam synthesis module links to each other with described gain control digit time TGC module, and described gain control digit time TGC module links to each other with described quadrature demodulation module.
4. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 3, it is characterized in that: described dynamic frequency orthogonal signalling generation module comprises dynamic frequency maker and digital frequency synthesizer, described dynamic frequency maker links to each other with described digital frequency synthesizer, described dynamic frequency maker is used to generate the frequency that changes with the beam propagation time, and described digital frequency synthesizer is used to generate corresponding cosine local oscillation signal and the corresponding sinusoidal local oscillation signal that changes with described frequency and beam propagation time.
5. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 4 is characterized in that: described dynamic frequency maker is made as field programmable gate array FPGA.
6. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 5 is characterized in that: calculate corresponding described frequency pulse-recurrence time and be stored in the described dynamic frequency maker according to Doppler ultrasonic image-forming system.
7. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 6 is characterized in that: described digital frequency synthesizer is made as field programmable gate array FPGA.
8. dynamic demodulation device of Doppler ultrasonic imaging system according to claim 7, it is characterized in that: in described digital frequency synthesizer, look-up table is set, according to the described frequency and the phase value in the different moment, from described look-up table, search the cosine value and the sine value of described phase value correspondence.
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|---|---|---|---|
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103512960A (en) * | 2013-09-27 | 2014-01-15 | 中国科学院声学研究所 | Ultrasound array imaging method |
| CN104665876A (en) * | 2015-02-10 | 2015-06-03 | 深圳大学 | TCD (Trans-cranial Doppler) blood flow detection method |
| CN105939674A (en) * | 2014-12-22 | 2016-09-14 | 奥林巴斯株式会社 | Diagnostic ultrasound apparatus, diagnostic ultrasound apparatus operation method, and diagnostic ultrasound apparatus operation program |
| CN108042155A (en) * | 2017-12-20 | 2018-05-18 | 飞依诺科技(苏州)有限公司 | Ultrasound echo signal automatic time frequency demodulation method and processing system |
| CN110090043A (en) * | 2018-01-30 | 2019-08-06 | 深圳市理邦精密仪器股份有限公司 | Fetal rhythm data capture method, device and the Medical Devices of ultrasonic Doppler |
-
2009
- 2009-09-29 CN CN200910190768A patent/CN101690671A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103512960A (en) * | 2013-09-27 | 2014-01-15 | 中国科学院声学研究所 | Ultrasound array imaging method |
| CN103512960B (en) * | 2013-09-27 | 2016-01-06 | 中国科学院声学研究所 | A kind of supersonic array formation method |
| CN105939674A (en) * | 2014-12-22 | 2016-09-14 | 奥林巴斯株式会社 | Diagnostic ultrasound apparatus, diagnostic ultrasound apparatus operation method, and diagnostic ultrasound apparatus operation program |
| CN105939674B (en) * | 2014-12-22 | 2019-09-24 | 奥林巴斯株式会社 | The working method of diagnostic ultrasound equipment and diagnostic ultrasound equipment |
| CN104665876A (en) * | 2015-02-10 | 2015-06-03 | 深圳大学 | TCD (Trans-cranial Doppler) blood flow detection method |
| CN108042155A (en) * | 2017-12-20 | 2018-05-18 | 飞依诺科技(苏州)有限公司 | Ultrasound echo signal automatic time frequency demodulation method and processing system |
| CN110090043A (en) * | 2018-01-30 | 2019-08-06 | 深圳市理邦精密仪器股份有限公司 | Fetal rhythm data capture method, device and the Medical Devices of ultrasonic Doppler |
| CN110090043B (en) * | 2018-01-30 | 2022-03-25 | 深圳市理邦精密仪器股份有限公司 | Ultrasonic Doppler fetal heart data acquisition method and device and medical equipment |
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Open date: 20100407 |