The picture signal post-processing approach and the device of supersonic colour blood flow imaging
Technical field
The present invention relates to ultrasonic imaging technique, relate in particular to the signal processing in the medical ultrasound imaging, particularly relate to the method and the device of the picture signal post processing of color flow angiography.
Background technology
Imaging of Type B black and white and color flow angiography are two broad aspect of modern medicine ultra sonic imaging.In ultra sonic imaging, speckle noise appears because tissue not only can cause in the ultrasonic B black white image the interference capability of ultrasonic reflections, equally also can in color blood-stream image, cause speckle noise, " black hole " appears in the color blood-stream image thereby make.In addition, because the intravital blood flow of people, tissue, blood vessel wall etc. are not complete immobilized reflector, ultrasonic front-end circuit components and parts are easy to form false " isolated point " coloured image with the indefinite front passage amplitude phase error that causes of working time length on coloured image simultaneously.For " black hole " of reducing coloured image reaches " isolated point " phenomenon, related post processing of image technology is an important step that influences picture quality in ultrasonic color blood flow imaging.Described in addition color blood-stream image post processing comprises the mixing post processing at least, is exactly with color blood-stream image, comprises velocity image, energy diagram picture and variance image, is embedded in the corresponding black white image according to certain rule.Its specific implementation because different color ultrasound front ends is different with the color flow angiography performance of processors, makes that threshold value and the principle combinations difference in the thresholding rule is bigger when mixing post processing.Up to the present, difficulty has a mixing post-processing technology generally acknowledged, system and method.
Below in conjunction with prior art and theory the existing post processing of image technology that is applied to ultra sonic imaging is done an explanation.Fig. 2 is color flow angiography background technology figure.The ultrasound wave that ultrasonic probe array 1 is launched enters human body, through the reflection of tissue and blood flow, is received by same linear transducer array 1.The signal that linear transducer array 1 receives is divided into two-way successively after amplifying circuit 3, A/D change-over circuit 4 and wave beam synthesis circuit 5, the one tunnel delivers to black-and-white signal processing module 61, forms the two-dimentional black and white tissue image signal corresponding to human tissue structure; Color blood-stream image processing module 62 is delivered on another road, forms the color blood-stream image signal of two dimension.Usually color blood-stream image processing module 62 adopts auto-correlation processor, can select to export three kinds of blood-stream image signals, i.e. either one or several in velocity image signal, energy diagram image signal and the variance image signal.Blood-stream image signal of being exported and above-mentioned black and white tissue image signal all are sent to threshold judgement module 63 and finish threshold judgement, are determined the image model sign of each scanning element point.This image model sign mixes post-processing module 64 with above-mentioned black and white tissue image signal and blood-stream image signal process, and blood-stream image is embedded in the black and white tissue image according to certain rule.This mixing post-processing module 64 is handled the picture signal that obtains through colorful digital scan converter 7, arrives display 8 at last and shows.In this process, from the strict sense, post processing of image comprises the processing of two aspects: the one, and the single channel signal of each image channel is handled before mixing, with the certain methods filtering wave point of making an uproar, with raising picture quality; The 2nd, the black and white tissue image signal data of colorful blood velocity image signal data, energy image signal data or the variance image signal data of auto-correlation processor output and 61 outputs of black-and-white signal processing module, according to certain method, be the thresholding rule, mix.Signal all can reduce the existence of " black hole " or " isolated point " pixel through described post processing of image.
About the thresholding rule, a basic rule is arranged.To being sent to four kinds of picture signals of mixing post processing thresholding is set respectively, certain pixel on the image then, threshold judgement is: (1) black and white tissue image data exceed the tissue pixels that is judged to of black and white tissue image thresholding; What (2) the velocity image data exceeded speed threshold is judged to the blood flow pixel; What (3) the energy view data exceeded energy threshold is judged to the blood flow pixel; (4) the variance image data exceed the tissue pixels that is judged to of variance thresholding.In actual engineering, because the ultrasonic performance of front end difference of different manufacturers, different machines, 4 kinds of thresholdings need experience setting and reasonable combination to finish the mixing post processing.
It is as follows that list of references has been enumerated relevant certain methods:
Document 1 has been summarized the common certain methods of mixing post processing of color flow angiography;
Document 2 is introduced people such as Torp.H and was utilized the space average method to handle the color blood-stream image data in 1996, to improve color image quality.In fact the space average method is equivalent to color image data is carried out a two-dimentional low pass smothing filtering, and this method is the method for the frequent removal high-frequency noise that uses in the Flame Image Process, makes in this way, can obtain the coloured image of colored gray scale smooth variation;
Document 3 is introduced Forestieri SF and is utilized median filter method in the Flame Image Process to handle energy view data in the color blood-stream image.Median filter method is the same with aforementioned space average method, also is the low pass filter of filter away high frequency noise commonly used in the Flame Image Process.
Document 4 and 5 has been introduced the people such as Michael of GE company by the colored statistics of histogram of color image data and the method for two-dimensional search, eliminates " black hole " and " isolated point " color image data in the color blood-stream image.As the threshold value of criterion, and two-dimensional search was a kind of processing method for the artificial raising coloured image ornamental of eliminating " isolated point " coloured image and " black hole " based on statistical decision purely when colored statistics of histogram was mainly used to color image data and black and white tissue image data mixing are set.
Above-mentioned several method all has certain effect to " black hole " and " isolated point " color image data of eliminating in the color blood-stream image, but also has limitation separately.The space two-dimensional averaging method is the two-dimensional filtering that color image data is carried out, and amount of calculation is bigger; Median filter method is only effective to the color power angio picture, to colored velocity image or variance image, on the picture point that blood flow rate changes, can go wrong.And the statistics with histogram of GE need be added up the color image data of a lot of frames, cause taking big memory element, and last threshold value can postpone to some extent; The two-dimensional search processing method will consume the very long processing time equally in addition.
Summary of the invention
The technical problem to be solved in the present invention is to avoid above-mentioned the deficiencies in the prior art part and the post processing of image method and the device that propose a kind of supersonic colour blood flow imaging, can be effective in multiple color blood-stream image simultaneously, handle simply, be convenient to again realize reducing " black hole " and " isolated point " phenomenon to improve image quality.
The present invention solve the technical problem the picture signal post-processing approach that adopts, and comprises step
A. will be divided into two-way from the beam signal of wave beam synthesis circuit, it is handled the back once black-and-white signal and produces the black and white tissue image signal, another is output color blood-stream image signal after colorful blood is handled, and comprises velocity image signal, energy diagram image signal and variance image signal;
C. each described color blood-stream image signal is divided into two-way again, and one the tunnel through threshold judgement generation image model sign; The rear end directly or by filter is sent in another road, delivers to the mixing post-processing module with described image model sign and described black and white tissue image signal and goes to do to mix imaging processing;
Especially, also comprise step
B. after colorful blood is handled, also to export one tunnel black and white tissue image signal from the beam signal of wave beam synthesis circuit and be used for threshold judgement.
Compared with prior art, because when ultrasonic front end works in the colorful blood pattern, what launch is narrow band signal, and what launch when working in the black white image pattern is broadband signal, so though the tissue image resolution of colorful blood module output signal correspondence is not as the tissue image of black and white processing module output signal correspondence, but for every scanning line, its image envelope is more level and smooth, simultaneously much smaller to the probability that the emission of signal forms interference by same range unit inner tissue echo, so as the reference thresholding, more can eliminate " black hole " and " isolated point " phenomenon in the coloured image with the tissue image signal thresholding for referencial use of black-and-white signal processing module output than tradition with it.
In the technique scheme, each single channel picture signal, comprise colorful blood velocity image signal, energy diagram image signal, variance image signal and be sent to the black and white tissue image signal of threshold judgement module, be decomposed into the local two-dimentional smothing filtering that one dimension is handled on the both direction through following step earlier, carry out threshold judgement again or mix post processing:
1. the vertical pixel on the smooth signal corresponding image m bar scanning line, promptly the data of the arbitrary pixel except that the border are the meansigma methods of the original scan-data of itself and front and back plurality of adjacent points on this scanning line, and store;
2. the pixel on the horizontal m bar scanning line of smooth signal corresponding image except that the border, promptly the data of arbitrary pixel are the meansigma methods of vertical smoothed data of respective point on its adjacent some scanning lines with front and back on this scanning line, and store.
To having the blood flow rate image of direction, the two-dimentional The disposal of gentle filter in described part is only got the peripheral point consistent with processing pixel sign symbol and is made average computation together.
Compare with other filtering modes, it is simple that the present invention program has processing, is applicable to multiple color blood-stream image simultaneously, and calculating and memory data output require little advantage.
The present invention solve the technical problem the image after processing device that adopts, and comprises ultrasonic probe 1, radiating circuit 2, receives amplifying circuit 3, and emission or reception ultrasonic scanning signal are used; Described reception amplifying circuit 3 is connected successively with A/D change-over circuit 4, wave beam synthesis circuit 5, and black-and-white signal processing module 61 and colorful blood processing module 62 are connected in parallel in after the wave beam synthesis circuit 5; Described colorful blood processing module 62 comprises that two groups of orthogonal demodulation circuits 621, low-pass filter circuit 622, wall filtering circuit 623 connect respectively successively, the parallel again input auto-correlation processor 624 of resulting two groups of signals, thus produce color Doppler flow signals; The color Doppler flow signals of described output is divided two-way, and one is sent to threshold judgement module 63, and another is sent to and mixes post-processing module 64 and the signal of aforementioned black-and-white signal processing module 61 outputs and the signal mixing post processing of threshold judgement module 63 outputs; Described result is delivered to display 8 through colorful digital scan converter 7, it is characterized in that, described colorful blood processing module 62 also comprises asks mould module 625, and this is asked mould module 625 to utilize the envelope of I after the quadrature demodulation, Q two paths of signals to produce one tunnel black and white tissue image signal and is sent to described threshold judgement module 63.Can use DSP to realize above-mentioned post-processing approach and circuit, only need a resource seldom just can realize the present invention, and when obtaining fine treatment effect, less cost.
Description of drawings
Fig. 1 is a color flow angiography post-processing approach flow process principle schematic of the present invention.
Fig. 2 is a prior art color flow angiography method flow diagram.
Fig. 3 is the generating principle sketch map of colorful blood treatment channel tissue image.
Fig. 4 is the ultrasonic color flow view data.
Fig. 5 is that smoothing processing obtains Cm, the raw image data point that the n dot image data need use.
The specific embodiment
Below, the most preferred embodiment shown in 1 is set forth the inventive method in conjunction with the accompanying drawings.
Colorful blood processing module 62 as Fig. 1 has not only been exported the color blood-stream image signal, and velocity image signal, energy diagram image signal or variance image signal have also been exported one tunnel black and white tissue image signal.The color blood-stream image signal that this road black and white tissue image signal passes through after local two-dimentional smoothed filter circuit 65 processing and above-mentioned colorful blood processing module 62 is exported is finished threshold judgement together; The output result of this judgement determines the image model sign of each pixel of every scanning line; The black and white tissue image signal of each road color blood-stream image signal of colorful blood processing module 62 outputs and 61 outputs of black-and-white signal processing module, respectively through behind the two-dimentional smothing filtering in single pass part separately with above-mentioned image model sign, enter the mixing post processing.
In above-mentioned processing, because when Ultrasound Instrument works in colorful blood pattern (to call the C pattern in the following text), also work in imaging of tissue pattern (to call the B pattern in the following text), emphasize resolution B pattern front end emission be broadband signal, C pattern with respect to the emission narrow band signal, in an imaging of tissue resolution elements, the B mode echoes causes " black hole " in the tissue image than the easier formation interference of C mode echoes.Simultaneously the C mode echoes is because lower radial resolving power makes that the tissue image envelope that is formed by the C pattern is smoother, and wherein " black hole " than the tissue image of B pattern still less.When the thresholding rule treatments, can reduce simultaneously " isolated point " coloured image quantity.
The tissue image signal of C mode treatment passage forms as shown in Figure 3.The output of wave beam synthesis circuit 5 enters colorful blood processing module 62, i.e. C mode treatment passage in the time period that the emission of C pattern receives.This signal forms I, the Q two paths of signals of 90 ° of phase phase difference earlier through the orthogonal demodulation circuit 621 in the colorful blood processing module 62.Described I, Q two paths of signals pass through the low-pass filter circuit 622 in the module 62 respectively, extract envelope separately; The two-way envelope enters detection and the parameter estimation that wall filtering circuit 623 and auto-correlation processor 624 carry out colorful blood on the one hand, form the output of color blood-stream image signal, enter as shown in phantom in FIG. on the other hand and ask mould module 625, form the black and white tissue image signal of C treatment channel.
The described mould module of asking can adopt following algorithm:
Wherein A is a black and white tissue image signal pixel data; Or adopt another algorithm:
Wherein K is a gain factor, determines that by experiment 1n represents natural logrithm;
Also can adopt such algorithm:
Wherein K is a gain factor, determines that by experiment 1g represents denary logarithm.
The two-dimentional smoothed filter circuit 65 in above-mentioned part can carry out respectively each channel signal as shown in Figure 1, also can only be applied to certain single channel signal, be velocity image signal, energy diagram image signal, variance image signal or black and white tissue image signal, all can effectively reduce noise jamming, more help image quality improvement.
The local two-dimentional The disposal of gentle filter of carrying out in single channel can be decomposed it in the following manner and is the level and smooth step of one dimension on the both direction, can not only reduce the quantity of " isolated point " pixel in the coloured image to a certain extent, have more and handle simple advantage, be applicable to multiple color blood-stream image simultaneously:
1. with n point diagram picture point on vertical 3 the smooth signal correspondence image m bar scanning lines of following calculating, use the original scan-data of itself and adjacent two point diagram picture points, and average result is stored;
Cm,n=(Cm,n-1+Cm,n+Cm,n+1)*0.33334
2. with n point diagram picture point on horizontal 3 the smooth signal correspondence image m bar scanning lines of following calculating, use vertical smoothed data of respective point on itself and adjacent two scanning lines, and average result is stored;
Cm,n=(Cm-1,n+Cm,n+Cm+1,n)*0.33334
Cm wherein, n range unit of the m bar scanning line of n data representing image, as shown in Figure 4.Image pixel vertical and horizontal when realizing level and smooth measure initial, just begin to realize smoothing processing when having only the image slices vegetarian refreshments to have 3 pixels at least.And initial some base lines in border when realizing level and smooth measure or column data will be capped or lose as known technology and do not addressed.Alleged 3 can be adopted 4 points according to need smoothly only as demonstration in the above-mentioned decomposition computation, 5 points, or k point is level and smooth, and the corresponding multiplier factor 0.33334 that changes is one of k part.
To having the blood flow rate picture signal of direction, the two-dimentional The disposal of gentle filter in described part need be finished according to the direction of speed.Because the positive and negative of data is the direction of response speed, make average computation so can only get the peripheral point consistent with described pixel sign symbol.
The two-dimentional smooth filtering method in above-mentioned part is applied in the thresholding rule, can also calculate in conjunction with mixing post processing, adopt to simplify.Post processing with colorful blood energy image imaging is an example below, sets forth this processing; Same alleged 3 are not smoothly limited to and actually can only make smoothing processing with three point data.
Figure 4 shows that the colorful blood energy image signal data of auto-correlation processor output, Cm, n represent the pixel of n range unit of m bar scanning line.Suppose to obtain handling this point data of back colorful blood energy diagram picture, earlier as shown in Figure 5, the resolution of colorful blood energy diagram picture (the calling the C image in the following text) data of the black and white tissue image (calling B ' image in the following text) of the black and white tissue image (calling the B image in the following text) of colorful blood treatment channel signal correspondence, black-and-white signal treatment channel signal correspondence and auto-correlation processor output signal correspondence is adjusted into consistent, carries out post processing of image more according to the following steps based on the two-dimentional smothing filtering in part:
1. the pixel on the vertically level and smooth B image m bar scanning line, promptly the data of the arbitrary pixel except that the border are the meansigma methods of the original scan-data of itself and front and back plurality of adjacent points on this scanning line, and store;
2. the pixel on the laterally level and smooth m bar scanning line of B image except that the border, promptly the data of arbitrary pixel are the meansigma methods of vertical smoothed data of respective point on its adjacent some scanning lines with front and back on this scanning line, and store;
3. as 1. the pixel on the vertically level and smooth C image m bar scanning line of method, and store;
4. the image model that utilize 2., result of calculation 3. and thresholding rule obtains is masked as the value coding of each pixel on the m bar scanning line, and coding rule is exactly that additional mark is positioned on the pixel value, and pixel value is selected B ' number according to the image model sign
According to or the C data; Thereby obtain mixing an intermediate object program of back image m bar scanning line, and store;
5. wait after 2., 3., 4. step is finished of some the scanning lines in back, all images point on the laterally level and smooth again C image m bar scanning line, and store as mixing the back result.The flag bit of above-mentioned intermediate object program is not participated in level and smooth calculating when laterally level and smooth, and the image model sign that promptly level and smooth back is every does not change.But show that for flag bit this intermediate object program pixel value is that to change its pixel value be 0 to participate in level and smooth calculating for the point of B ' data.
Above-mentioned two-dimensional filtering method or be not only applicable to colorful blood energy diagram image signal based on the mixing post-processing approach of two-dimensional filtering also is applicable to colorful blood variance image signal and colorful blood velocity image signal.Difference is that its two dimension smoothly need be finished according to the direction of speed when handling colorful blood velocity image signal.If it is 3 C data symbols are identical, then consistent with above-mentioned steps.If having in 3 just has negatively, then the choosing point consistent with the intermediate point symbol done at 2 and smoothly got final product.Equally, the above 3 smoothly only is the level and smooth subclass of some points on two one dimension directions, is used for the example explanation.
The benefit of this processing method is the effect that minimizing " black hole " and inhibition " isolated point " coloured image are more arranged through B image after level and smooth and C image.
Ultrasonic color blood flow imaging device of the present invention is seen Fig. 1 to Fig. 3, comprises ultrasonic probe 1, radiating circuit 2, receives amplifying circuit 3, and emission or reception ultrasonic scanning signal are used; Described reception amplifying circuit 3 is connected successively with A/D change-over circuit 4, wave beam synthesis circuit 5, and black-and-white signal processing module 61 and colorful blood processing module 62 are connected in parallel in after the wave beam synthesis circuit 5; Described colorful blood processing module 62 comprises that two groups of orthogonal demodulation circuits 621, low-pass filter circuit 622, wall filtering circuit 623 connect respectively successively, the parallel again input auto-correlation processor 624 of resulting two groups of signals, thus produce color Doppler flow signals; The color Doppler flow signals of described output is divided two-way, and one is sent to threshold judgement module 63, and another is sent to and mixes post-processing module 64 and the signal of aforementioned black-and-white signal processing module 61 outputs and the signal mixing post processing of threshold judgement module 63 outputs; Described result is delivered to display 8 through colorful digital scan converter 7, it is characterized in that, described colorful blood processing module 62 also comprises asks mould module 625 to produce the black and white tissue image signal for threshold judgement module 63 usefulness; The described mould of asking is that envelope to I, Q two paths of signals after the quadrature demodulation carries out.
Be sent to the black and white tissue image signal of threshold judgement module 63 or be sent to the color blood-stream image signal, the black and white tissue image signal that mix post-processing module 64 and through two-dimentional smoothing circuit 65 pretreatment, better effect can be arranged in advance.
On actual Project Realization, the circuit of above numerical portion or module can be by DSP (Digital SignalProcessing) technology, the generation of especially described several picture signals, judging process and the related method step of mixing post processing all can use high-speed real-time digital signal processing chip DSP (Digital Signal Processor) to realize, and use DSP on-chip memory or plug-in memorizer as required.Wherein, when for example realizing local two-dimentional smothing filtering with dsp chip, 3 smoothly are equivalent to addition and multiplication, are equivalent to multiply by 0.33334 divided by 3, less demanding to calculating real-time; Because the data of handling this moment have been view data, only need the colorful blood channel B view data of three scanning lines of storage and the C view data of three scanning lines in addition, also very low to the requirement of memorizer.Under the situation that resource allows in the DSP sheet, can not need plug-in memorizer.
The list of references of enumerating in this manual and quoting is as follows:
1.D.H.Evants,W.N.Mcdicken,Doppler?ultrasound-physics,instrumentation?and?signalprocessing,second?edition,JOHN?WILEY?&?SONS,LTD,2000
2.Torp?H.Bjaerum?S,Quality?versus?frame?rate?in?the?color?flow?imaging:anexperimental?study?based?on?off-line?processing?of?RF-signals?recorded?frompatients,pp1229-12321996IEEE?Ultrasonics?Symposium
3.Forestieri?SF,Median?temporal?filtering?of?ultrasonic?data,US?patent?5413105,May9,1995
4.M.J.Washburn,et.al.ultrasound?color?flow?display?optimization?by?adjustment?ofthreshold?using?sampling,US?patent?6071241,Jun.6,2000
5.M.J.Washburn,et.al.ultrasound color flow?display optimization,US patent6126176,Doc.19,2000