Background technology
The rhythmic expansion of thorax and dwindling, thus complete air-breathing with exhale, respiratory movement that Here it is.Motion (high frequency motion), respiratory movement and people's movement or the shake of sick bed (translation motion) etc. of the regular pollex of heart itself (heart movement), capillary all can cause the translation motion of human heart entirety in three dimensions.In x-ray imaging system, due to the combined influence of above-mentioned motion, can there is two-dimension translational motion in coronary artery on radiography face.Therefore, the projection of the motion that coronary angiography image records on the one hand heart on two dimensional surface, is also superimposed with the two-dimension translational motion on radiography face of coronary artery that respiratory movement, high frequency motion and the translation motion of human body cause simultaneously.
Obtain more approaching two-dimentional angiogram under truth and for blood vessel 3 D reconstructing, need these motions automatically to separate.Prior art is generally independently to extract respectively doing more physical exercises, and extracts respirometric a kind of way and be in the time extracting the above-mentioned motion of human body by setting in advance gauge point, and they are carried out to sequential tracks.According to respirometric feature, people can move together with other organs in kinetoplast in breathing.It is generally acknowledged, these organs can carry out three-dimensional translation along with the motion of lung, and their motion is all synchronous.So the motion of supposing the heart that respiratory movement causes is also consistent with the motion of the organ adjacent with it on radiography plan, can find other the more structural unique points outside heart to serve as a mark a little in radiography figure.In whole sequence, follow the tracks of these gauge points, obtain the motion conditions of these gauge points, then by the respiratory movement on approximate the motion of these gauge points two-dimensional projection's face for this reason.Another kind of way utilizes these can not follow the architectural feature point that heart moves together equally, and difference is that the latter is the motion of recording these gauge points in radiography.Therefore, require just each unique point to be chosen and mark before radiography.Obviously, this two schemes is all defective.The former applicability is very poor, because can not guarantee all to exist in each frame radiography figure the gauge point (other the more structural unique points outside heart) that meets this condition, and look for this point also to need experience (need to know quite well human anatomic structure).In the time there is not above unique point in radiography figure, respiratory movement is difficult to be extracted.The latter's realization needs great many of experiments control, improper to general clinical practice.In addition, in above-mentioned two kinds of methods, whether human body exists other motion effectively not show in the time carrying out physiological activity, and the analysis that will carry out other motions is extracted to patient and can be brought secondary injury.
In addition, also have a kind of method to realize under both arms x ray contrast condition, its isolating cardiac motion from respirometric thought is: the two width radiography figure that get the different projection angles of synchronization, wherein corresponding coronary artery blood vessel is carried out to three-dimensional reconstruction, obtain the blood vessel three-dimensional spatial distribution in this moment.So, all radiography figure in the respiratory cycle, to after mating and rebuilding, are obtained to one group of three-dimensional structure sequence, the space displacement vector between them is respiratory movement.Comparatively speaking, can obtain reliable respiratory movement estimated result by the method, still, due to the constraint of both arms x ray contrast condition, can not apply widely in practice, and the method can not extract the motor message except heart signal and breath signal.
Summary of the invention
For the deficiencies in the prior art, the object of the invention is to propose a kind of single armed x ray angiographic image parameter decomposition method of estimation of doing more physical exercises, form data sequence by tracking structure unique point, and utilize the method for empirical mode decomposition (EMD) automatically to extract heart, breathing, high frequency and the translation motion of human body.
For realizing above goal of the invention, the present invention by the following technical solutions:
A kind of single armed x ray angiographic image sequences parameter decomposition method of estimation of doing more physical exercises, comprises the following steps:
(1) choose blood vessel structure unique point;
(2) the blood vessel structure unique point of choosing is carried out from motion tracking in whole radiography graphic sequence;
(3) in the tracking sequence s (n) of point, choosing length is n
s=k*N
1the sequence of (k > 1)
(4) will
motion y (n) in motion x (n) and the y direction being decomposed in x direction, more respectively x (n) and y (n) are carried out to EMD decomposition, obtain the each self-movement signal after EMD decomposes;
(5) according to priori physiological knowledge, each independent signal is sorted out accordingly.
Compared with prior art, the present invention has following beneficial effect:
(1), compared to simple manual tracking, automatically choose that approach that blood vessel structure unique point and EMD combine extracts each periodic motion automatically and aperiodic motion has applicability and dirigibility widely, almost applicable to all radiography sequence chart;
(2) simultaneously,, compared to directly organizing the method that identification point is followed the tracks of by dependent imaging means is again set near heart, the present invention has greater security and operability.This is because the label that tissue adds is in vivo generally Invasibility, can produce infringement more or less to human body self, and it is all numerous and diverse that whole process is extracted in the interpolation of its label, imaging, eliminating, respiratory movement, for bringing inevitable trouble and error in practical operation;
(3) unique point that the inventive method is chosen relates to the blood vessels at different levels of left and right coronary artery, has considered the movable information of left and right coronary artery, thereby has better reliability and accuracy.
Accompanying drawing explanation
With reference to explanation below, by reference to the accompanying drawings, can there is best understanding to the present invention.In the accompanying drawings, identical part can be represented by identical label.
Fig. 1 is the process flow diagram of preferred embodiment of the present invention;
Fig. 2 (a) and Fig. 2 (b) are respectively radiography figure and the corresponding blood vessel structure figure of this radiography figure choosing in the embodiment of the present invention, and corresponding projection angle is (26.5 ° ,-20.9 °);
Fig. 3 (a), 3 (b), Fig. 3 (c), 3 (d), Fig. 3 (e), 3 (f), Fig. 3 (g), 3 (h), Fig. 3 (i), 3 (j) are respectively a left sided sequence original signal, high-frequency signal, heart signal, the breath signal peace shifting signal curve map in X-axis and Y-axis;
Fig. 4 (a) and Fig. 4 (b) are respectively radiography figure and the corresponding blood vessel structure figure of this radiography figure choosing in the embodiment of the present invention, and corresponding projection angle is (42.3 °, 26.8 °);
Fig. 5 (a), 5 (b), Fig. 5 (c), 5 (d), Fig. 5 (e), 5 (f), Fig. 5 (g), 5 (h), Fig. 5 (i), 5 (j) are respectively a right side sequence original signal, high-frequency signal, heart signal, the breath signal peace shifting signal curve map in X-axis and Y-axis.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with accompanying drawing and exemplary embodiment, the present invention is further elaborated.Should be appreciated that exemplary embodiment described herein is only in order to explain the present invention, the scope of application being not intended to limit the present invention.
The inventive method utilizes EMD method automatically to extract heart, breathing, translation and other motions.As shown in Figure 1, comprise the following steps:
(1) choose blood vessel structure unique point
According to the guidance of the knowledge such as physiology and anatomy, the unique point of mark needs can concentrated expression to go out the movable information of blood vessel entirety, and therefore, the different point of selected shape comprises the starting point and ending point of each vessel segment, and each flex point between vessel segment.And in the contrastographic picture sequence under two different projection angles, to all unique point numberings, characteristic of correspondence point has identical numbering mutually.As shown in Figure 2 and Figure 4, be respectively at projected angle in a pair of radiography figure of (26.5 ° ,-20.9 °) and (42.3 °, 26.8 °), exist 5 different points of the shape after numbering (white point in figure), their relation is to name one to one according to numeral.
(2) separate empirical mode decomposition (EMD) method of doing more physical exercises
Heart and human body respiration motion are all periodic motions, it is much smaller that but respirometric frequency is compared heart movement, in general, the frequency of heart proper motion is 60~100 beats/min, its cycle is 0.6-1.0s, the respirometric cycle is much longer, is generally 3-6s, may be longer quietly time.On the other hand, heart movement is more violent, and respirometric amplitude is less, and the displacement producing is less, is a process relatively stably.For self vibrations of capillary, than heart movement and respiratory movement, it is more violent, and the cycle is shorter, it is generally acknowledged that its cycle is less than 0.6s, and rangeability is little.Be aperiodic motion and the feature of translation motion maximum is it, be easy to distinguish with respect to periodic motion.
According to these features of above-mentioned each motor message in radiography figure, can automatically separate heart, breathing, translation and high frequency motion by the method for empirical mode decomposition (EMD).Introduce EMD method below.
1) EMD method
The starting point of EMD is that the concussion in signal is regarded as to local.In fact, if see variation (2 minimal values between 2 adjacent extreme points assessing signal x (t), respectively at t-and t+ place), need to define (part) radio-frequency component { d (t), t-≤t≤t+}(local detail), this radio-frequency component is corresponding with concussion, and concussion is between 2 minimal values and passed through maximum value (certainly appearing between 2 minimal values).For complete this figure, also need to define (part) low-frequency component m (t) (local trend), x (t)=m (t)+d (t) like this, (t-≤t≤t+).For all vibrations compositions of whole signal, to decompose if can find suitable method to carry out this type of, this process can be applied to the remaining composition of all local trends, and therefore the constituent of a signal can be pulled out out by the mode of iteration.
For a signal x (t) to be decomposed, carry out effective EMD decomposition step as follows:
(1) find out all extreme points of x (t);
(2) by method of interpolation, minimum point is formed to lower envelope emin (t), maximum value is formed to coenvelope emax (t);
(3) computation of mean values m (t)=(emin (t)+emax (t))/2;
(4) detach detail signal d (t)=x (t)-m (t);
(5) to remaining m (t), make x (t)=m (t), repeating step (1)-(5), until the average of d (t) is 0, or till meeting stopping criterion.
In practice, said process need to redefine by a screening process, first iterative step of screening process is that detail signal d (t) is repeated to (1)-(5) step, until the average of d (t) is 0, or meets certain stopping criterion and just stop iteration.
Once meet stopping criterion, detail signal d (t) now is just called as intrinsic mode functions (Intrinsic Mode Function is called for short IMF), and the corresponding residual signal of d (t) calculates by the 5th step.By above process, the quantity of extreme point is accompanied by the generation of residual signal and fewer and feweri, and whole decomposable process can produce limited IMF, and this limited IMF is exactly needed independently signal.
2) separation algorithm
Suppose that in radiography graphic sequence, on coronary artery blood vessel, certain puts p (x, the curve movement of x axial coordinate y) is x (n) (frame number that n is angiogram frames), the curve movement of y axial coordinate is y (n), make s (n)=(x (n), y (n)), s (n) can be resolved into formula below:
S (n)=c (n)+r (n)+h (n)+L (n) is c (n)=(x wherein
c(n), y
c(n)) the motion of the kinetic puncta vasculosa of expression heart; R (n)=(x
r(n), y
r(n)) represent the motion that respiratory movement causes; H (n)=(x
h(n), y
h(n)) represent because of human body tremble or blood vessel self beat produce motion, be generally regarded as radio-frequency component; L (n)=(x
l(n), y
l(n)) expression translation motion (comprise the movement of people's health in angiographic procedure, and the movement of radiography equipment etc.).For convenience of representing, all use s (n) to represent that the puncta vasculosa of extraction is along the changes in coordinates curve of x axle, y axle below, the puncta vasculosa that c (n) expression heart movement causes is along the changes in coordinates curve of x axle, y axle, the puncta vasculosa that r (n) expression respiratory movement causes is along the changes in coordinates curve of x axle, y axle, the puncta vasculosa that h (n) expression high frequency motion causes is along the changes in coordinates curve of x axle, y axle, and L (n) represents the changes in coordinates curve of translation motion along x axle, y axle.Therefore, be exactly the operation to x (n) and y (n) respectively to the operation of s (n), be exactly respectively to x to the operation of c (n)
cand y (n)
c(n) operation is exactly respectively to x to the operation of r (n)
rand y (n)
r(n) operation is exactly respectively to x to the operation of h (n)
hand y (n)
h(n) operation is exactly respectively to x to the operation of L (n)
land y (n)
l(n) operation.
Specific algorithm is as follows:
Step1: the blood vessel structure unique point of choosing in (1) is carried out from motion tracking in whole radiography graphic sequence;
Step2: choosing length in the tracking sequence s (n) of point is n
s=k*N
1the sequence of (k > 1)
if the length of original series s (n) is n, choosing sequence length is n
s=n-n%N
1, also, make n
sn
1integral multiple, wherein N
1for the cycle of heart movement, % is remainder symbol.
Step3: will
motion y (n) in motion x (n) and the y direction being decomposed in x direction, more respectively x (n) and y (n) are carried out to EMD decomposition, obtain the each self-movement signal after EMD decomposes;
Step4: each independent signal is sorted out accordingly according to priori physiological knowledge.
The each motor message decompositing in conjunction with EMD method by priori physiological knowledge is analyzed, can determine the composition of the each movable information of easy confirmation, specifically see Fig. 3 (a)-3 (j) and Fig. 5 (a)-5 (j), wherein, heart signal curve map, breath signal curve map and high-frequency signal curve map are respectively tracking 5 curve maps that unique point obtains above, the dotted line of translation signal represents the motion of the skeletal muscle of manually following the tracks of, and is the curve map being extracted by EMD method and solid line represents.
From Fig. 3 (a)-3 (j) and Fig. 5 (a)-5 (j), isolated each motor message can be found out, the heart signal of each unique point and breath signal have obvious regularity; High-frequency signal is such as, due to the impact of many factors (blood vessel self trembles and the trembling etc. of people) uneven, but it is all outside the scope of physiological knowledge, so it is all classified as to high-frequency signal; And the translation signal automatically being extracted by EMD method is substantially identical with the translation signal that manually tracking skeletal muscle extracts, thereby there is very strong practicality.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any modifications of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.