CN104614010A - Method of building flexibility matrix based on ultrasonic focusing information - Google Patents
Method of building flexibility matrix based on ultrasonic focusing information Download PDFInfo
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- CN104614010A CN104614010A CN201510083590.3A CN201510083590A CN104614010A CN 104614010 A CN104614010 A CN 104614010A CN 201510083590 A CN201510083590 A CN 201510083590A CN 104614010 A CN104614010 A CN 104614010A
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Abstract
The invention provides a method of building a flexibility matrix based on ultrasonic focusing information. The method comprises the steps of measuring the size of a focal spot of a focusing ultrasonic transducer; dividing a measuring object into I disturbance areas; obtaining a boundary survey voltage vector without ultrasonic focusing; disturbing each disturbance area by focusing ultrasonic wave to obtain the boundary survey voltage vector with ultrasonic focusing; and calculating a flexibility value of an i position of each disturbance area, so as to obtain the flexibility distribution of the overall measuring field. According to the method provided by the invention, errors caused by carrying image rebuilding work through the flexibility matrix or the flexibility matrix updating method in an empty field at present can be alleviated, therefore the image rebuilding quality can be improved.
Description
Technical field
The invention belongs to process technical field of imaging, particularly relate to and build sensitivity matrix method based on focus ultrasonic disturbance information.
Background technology
Electricity tomography (ElectricalTomography, ET) technology is a kind of process imaging technique grown up the eighties in 20th century, have that radiationless, structure is simple, fast response time, non-intruding, the advantage such as visual and with low cost, it has broad application prospects in fields such as clinical medicine monitoring and industrial multiphase flow measurements.But because ET has soft field, its image reconstruction process is the solution procedure of a non-linear inverse problem.
Sensitivity matrix is often used for the reverse temperature intensity process of ET, and the introducing of sensitivity matrix can make this non-linear inverse problem linearization, and then simplifies solution procedure.The accuracy of sensitivity matrix directly affects the precision of ET image reconstruction.Sensitivity matrix reflects the disturbance of cell parameters to the impact of border detected value, and the value of Boundary Detection point is to the sensitivity of cell parameters change " perception " in other words.Sensitivity matrix itself does not have analytical expression, usually has two kinds of computing method: (1) test method of perturbation, is namely directly obtained by test according to definition, (2) simulation calculation method, comprise and asking for according to being defined by simulation calculation, and utilize the reciprocity character of electromagnetic field to solve, the expression formula of its impedance sensitivity provided (Geselowitz D B by Geselowitz the earliest in 1971, An application of electrocardiographic lead theory to impedanceplethysmography, IEEE Trans.Biomed.Eng., 1971, 18 (1): 38-41), and give reduced form (LehrJ by Lehr, A vectorderivation useful in impedance plethysmographic field calculations, IEEE Trans.Biomed.Eng., 1972, 19 (2): 156-157).
For test method of perturbation, as 2013, Liu Ze was published in " Chinese journal of scientific instrument " (Chinese Journal of ScientificInstrument) the 34th volume, 1982-1988 page, be entitled as the article of " electromagnetic chromatographic sensitivity matrix experimental test procedures " (Experimentalmeasurementmethod of sensitivity matrix for electromagnetic tomography), first the boundary survey data of one group of barnyard (namely not having inclusions) are obtained, then successively test sample is placed on each subdivision cell position in sensor, obtain the boundary survey data after test sample disturbance, these data again with barnyard Data Comparison, namely sensitivity matrix is obtained according to sensitivity matrix definition.But, because test sample is the disturbance produced barnyard, the sensitivity matrix of what this kind of method calculated is barnyard, instead of measure the sensitivity matrix of thing field.For simulation calculation method, as 2014, Zhao Jia was published in " measurement science and technology " (Measurement Science andTechnology) the 25th volume, document number is 085401, the article being entitled as " one is the sparse reconstruction algorithm of electricity tomography fast " (A fast sparsereconstruction algorithm for electrical tomography) is used, it is the distribution by simulation calculation sensitivity matrix, the Utopian direct problem model arranged due to simulation process is often difficult to consistent with real system, cause the sensitivity matrix calculated accurately can not reflect the impact of the small sample perturbations of real system medium on border measured value.And be truly distributed as unknown quantity to be asked due to medium, by simulation calculation is also the sensitivity matrix of barnyard, instead of measures the sensitivity matrix of thing field.In current ET image reconstruction algorithm research process, the dielectric distribution change usually in supposition field domain is little, is gone out the sensitivity matrix of barnyard, and then utilize this sensitivity matrix to solve the image reconstruction inverse problem of ET by test or simulation calculation.
But it should be noted that sensitivity matrix is the result that local linear is similar to, change with the change of distribution of conductivity, we need to solve the sensitivity matrix measuring thing field in theory.In current image reconstruction process, assumed sensitivity matrix is constant, and use the sensitivity matrix of barnyard, this certainly will bring comparatively big error to image reconstruction result.In order to alleviate this problem, as the people such as W Q Yang were published in " measurement science and technology " (Measurement Science & Technology) the 14th volume in 2002, R1-R13 page, be entitled as in the survey article of " Image Reconstruction Algorithms of ECT System " (Image reconstruction algorithms for electrical capacitance tomography) and mention, the reconstruction image utilizing pilot process to obtain based on the image reconstruction algorithm of sensitivity matrix renewal carries out renewal calculating to sensitivity matrix, image reconstruction is carried out again with the sensitivity matrix after renewal, to improve the quality of rebuilding image.But sensitivity matrix renewal process needs to carry out direct problem and solves, more consuming time.The more important thing is that the reconstruction image that pilot process obtains and true medium are distributed with deviation, therefore, compared to the sensitivity matrix measuring thing field, the sensitivity matrix that the method calculates still has error.
Summary of the invention
For the problems referred to above, the object of this invention is to provide a kind of method of sensitivity matrix of component electricity tomography.The method to the scanning disturbance of measuring thing field, utilizes disturbance information by concentration ultrasonic, measures the sensitivity matrix of thing field according to method of perturbation approximate treatment.Thus the error that alleviation adopts the sensitivity matrix of barnyard or sensitivity matrix update method to carry out image reconstruction work at present to bring, improve image reconstruction quality.For achieving the above object, the present invention takes following technical scheme:
A kind of based on focus ultrasonic disturbance information structure sensitivity matrix method, the method is by the scanning disturbance of concentration ultrasonic to measurement thing field, utilize the boundary survey voltage vector of focus supersonic wave disturbance fore-and-aft survey, the sensitivity matrix of computation and measurement thing field, comprises following step:
1) focal spot size of focused transducer is measured
Make microphone aim at focused transducer, and make the sensing unit of microphone be in the focal spot place of focused transducer, regulate the position of microphone, measure the focal spot size of focused transducer;
2) measurement thing field is divided into I disturbance region, determines the positional information of each disturbance region, and concentration ultrasonic intends the scanning sequency to each disturbance region
The focal spot size obtained is measured according in measurement thing field size and step 1, measurement thing field is divided into I disturbance region, division principle is: focused transducer can complete the scanning to whole measurement thing field, and each disturbance region is not overlapping, and disturbance region is focal spot institute overlay area; Record the positional information of each disturbance region, and determine that concentration ultrasonic intends the scanning sequency to each disturbance region, from 1 to I;
3) without in focus ultrasonic situation, to excitation, the measurement of measuring thing field enforcement electricity tomography, boundary survey voltage vector φ is obtained
By applying current excitation or voltage drive on exciting electrode, realize applying electrical stimuli to measurement thing field, gather the boundary voltage in each potential electrode under cycle motivation circulation measurement pattern, form boundary survey voltage vector φ, complete and once encourage measuring process;
4) in focus ultrasonic situation, each disturbance region i of focus supersonic wave disturbance, simultaneously again to excitation, the measurement of measuring thing field enforcement electricity tomography, obtains boundary survey voltage vector φ
i
By focused transducer perpendicular to measurement thing field, to each disturbance region i, 1≤i≤I, while focus supersonic wave disturbance, all complete a step 3) in the excitation measuring process of electrod-array, measure the boundary survey voltage vector φ of thing field when obtaining focus supersonic this disturbance region of wave disturbance
i;
5) step 3 is utilized) and step 4) measure the boundary voltage signal psi and φ that obtain respectively
i, by the Sensitirity va1ue of following formulae discovery each disturbance region i position, be designated as A
i,
A
i＝φ
i-φ
A
ibe the Sensitirity va1ue measuring each disturbance region i position, thing field;
6) the sensitivity profile A of whole measurement thing field is obtained
By the Sensitirity va1ue of each disturbance region position, integrating step 1) in the positional information of each disturbance region, obtain the sensitivity profile A of whole measurement thing field.
The present invention is owing to taking above technical scheme, and it has the following advantages:
(1) the present invention obtains according to method of perturbation approximate treatment the sensitivity matrix measuring thing field, instead of the sensitivity matrix of barnyard.
(2) the present invention obtains sensitivity matrix by test, and compared to emulated computation method, this method and real system have better consistance.
(3) the present invention is in the sensitivity matrix process of computation and measurement thing field, utilizes concentration ultrasonic to produce disturbance to measurement focusing territory, thing field medium, by Measured Boundary magnitude of voltage, and then calculates the Sensitirity va1ue focusing on territory.Being determined because focus on the size in territory by focused transducer parameter, is generally millimeter magnitude, and the sensitivity matrix that institute can obtain degree of precision in this way distributes.
Accompanying drawing explanation
The following drawings describes the embodiment selected by the present invention, is exemplary drawings and non exhaustive or restricted, wherein:
Fig. 1 is the electric signal excitation measurement pattern schematic diagram of two-dimentional thing field;
The measurement Su-field models of Fig. 2 (a) for arranging;
Fig. 2 (b) measures the barnyard model corresponding to Su-field models for Fig. 2 (a);
Fig. 3 is the sensitivity matrix result between the Different electrodes pair that calculates of different sensitivity matrix computational approach.
Embodiment
Be described in detail of the present invention below in conjunction with drawings and Examples.
Be illustrated based on focus ultrasonic disturbance information structure sensitivity matrix method of the present invention below in conjunction with accompanying drawing and embodiment, be intended to describe as embodiments of the invention, be not can manufactured or utilize unique forms, also should comprise within the scope of the invention the embodiment that other can realize identical function.
The present invention is based on focus ultrasonic disturbance information structure sensitivity matrix method and probably can be divided into following seven steps:
(1) focal spot size in the focusing territory of focused transducer is measured.
Fixed-focus ultrasonic transducer and microphone, make microphone aim at focused transducer, and make the sensing unit of microphone be in the focal spot place of focused transducer, regulate the position of microphone, measure the focal spot size of focused transducer.
(2) measurement thing field is divided into I disturbance region, determines the positional information of each disturbance region, and concentration ultrasonic intends the disturbance order to each disturbance region.
According to measuring the size of thing field and focusing on the focal spot size in territory, measurement thing field is divided into I disturbance region, division principle is: focused transducer can complete the scanning to whole measurement thing field, and each disturbance region is not overlapping, and disturbance region is focal spot institute overlay area.Record the positional information of each disturbance region, and determine that concentration ultrasonic intends the disturbance order to each disturbance region, from 1 to I.
(3) without under focus supersonic wave disturbance, realize the excitation of electricity tomography, measuring process, obtain boundary survey voltage vector φ.
Without under focus supersonic wave disturbance, electrical stimuli, measurement are carried out to measurement thing field, obtain boundary survey voltage vector φ.Measure thing field, 16 equally distributed rectangle potential electrode for circle, adopt the cycle motivation circulation measurement pattern of adjacent actuators, adjacent measurement, and exciting electrode is not measured, obtain 208 boundary survey magnitudes of voltage altogether, namely φ is the vector of 1*208 dimension.The electric signal excitation measurement pattern of two dimension thing field as shown in Figure 2, wherein current excitation is applied to the electrode being numbered 1, the electrode being numbered 2 is ground-electrode, measures and calculates electromotive force value difference on 3, No. 4 adjacent electrodes as the boundary voltage vector do not had in focus supersonic wave disturbance situation.
(4) under focus supersonic wave disturbance, concentration ultrasonic acts on i-th disturbance region, again realizes excitation, the measuring process of electricity tomography simultaneously, obtains boundary survey voltage vector φ
i.
Focused transducer is perpendicular to the two-dimensional imaging cross section measuring thing field, and concentration ultrasonic acts on i-th disturbance region, 1≤i≤I.According to acoustoelectric effect principle, the conductivity of i-th disturbance region changes.
While concentration ultrasonic focuses on i-th disturbance region, the excitation of electrod-array in completing steps 3, measuring process again, obtains the boundary survey voltage vector φ measuring thing field when concentration ultrasonic focuses on this disturbance region
i, φ
ialso be the vector of 1*208 dimension.
(5) Sensitirity va1ue of i-th disturbance region is calculated.
Utilize thing field boundary voltage vector φ and φ obtained respectively in step 3 and step 4
i, according to following formula, calculate the Sensitirity va1ue of i-th disturbance region,
A
i＝φ
i-φ
A
ibe the Sensitirity va1ue measuring i-th disturbance region in thing field.
(6) judge whether transducer completes the disturbance to all disturbance regions, and obtain the Sensitirity va1ue of corresponding disturbance region position.If completed, then implementation step 7; If do not completed, then change the disturbance region position of focus supersonic wave disturbance, make i=i+1, and jump to step 4.
Intend, in the disturbance region information measuring the interscan generation of thing field, judging whether transducer completes the focusing disturbance to all disturbance regions, and obtaining the Sensitirity va1ue of corresponding disturbance region according to the concentration ultrasonic determined in step 2.If completed, then implementation step 7; If do not completed, then change the disturbance region position of focus supersonic wave disturbance, even i=i+1, and jump to step 4.
(7) the sensitivity matrix distribution A of whole measurement thing field is obtained.
By the Sensitirity va1ue of each disturbance region, the positional information of each disturbance region in integrating step 1, obtains the sensitivity matrix distribution A of whole measurement thing field.In this example, the focal spot radius of concentration ultrasonic is 1.2mm, and measuring thing field radius is 3cm, and concentration ultrasonic carries out non-overlapping focusing scanning to whole measurement thing field, totally 489 disturbance regions.So the dimension of the sensitivity matrix calculated is 208*489.
In order to feasibility and the validity of the sensitivity matrix method based on focus ultrasonic disturbance information of the present invention are more objectively described, distinct methods is adopted to calculate sensitivity matrix.The measurement Su-field models of Fig. 2 (a) for arranging, background conductance rate is 0.5S/m, and dielectric conductance rate is 2S/m.Fig. 2 (b) measures the barnyard model corresponding to Su-field models for (a), and namely background conductance rate is 0.5S/m, and thing does not have inclusions in field.Fig. 3 shows the sensitivity matrix result between Different electrodes that different sensitivity matrix computational approach calculates pair, wherein the first sensitivity matrix being classified as the barnyard utilizing Geselowitz theory calculate, this sensitivity matrix is the general sensitivity matrix of current researcher; Second sensitivity matrix being classified as the measurement thing field utilizing Geselowitz theory calculate; 3rd sensitivity matrix being classified as the measurement thing field that the sensitivity matrix method based on focus ultrasonic disturbance information calculates.
Sensitivity matrix distribution in comparison diagram 3 between secondary series (sensitivity matrix of Geselowitz theoretical method computation and measurement thing field) and first row (Geselowitz theoretical method calculates the sensitivity matrix of barnyard) Different electrodes pair, the sensitivity matrix that barnyard can be found out and the sensitivity matrix gap measuring thing field larger.So in current research work, assumed sensitivity matrix is constant, uses the sensitivity matrix of barnyard, comparatively big error certainly will be brought to image reconstruction result.
Sensitivity matrix distribution in comparison diagram 3 between secondary series (sensitivity matrix of Geselowitz theoretical method computation and measurement thing field) and the 3rd row (sensitivity matrix of measurement thing field based on focus ultrasonic disturbance information builds) Different electrodes pair, the disturbance utilizing concentration ultrasonic can be seen, the sensitivity matrix of the measurement thing field calculated according to sensitivity matrix and the Geselowitz method of the measurement thing field of method of perturbation approximate treatment is distributed with good consistance, the validity of the sensitivity matrix method that builds based on focus ultrasonic disturbance information that this checking proposes.Here it may be noted that, because true medium distribution is unknown amount to be asked, Geselowitz method cannot be utilized under actual conditions to calculate the sensitivity matrix measuring thing field, but utilize and build based on focus ultrasonic disturbance information the sensitivity matrix that sensitivity matrix method but can calculate dielectric distribution thing field to be asked, and be effective.
Sensitivity matrix between first row in further comparison diagram 3 (Geselowitz method calculates barnyard sensitivity matrix) and the 3rd row (sensitivity matrix based on the measurement thing field that focus ultrasonic disturbance information builds) Different electrodes pair distributes, the disturbance utilizing concentration ultrasonic can be found out, sensitivity matrix distribution according to the measurement thing field of method of perturbation approximate treatment distributes closer to the dielectric distribution characteristic of true thing field than the barnyard sensitivity matrix utilizing Geselowitz method to calculate general at present, there is more dielectric distribution information, image reconstruction accuracy can be improved.
Sensitivity matrix method based on focusing ultrasonic wave disturbance information of the present invention, it is mainly used in biological tissue's dielectric distribution imaging, but also can be applicable to industrial multiphase flow measurement, when being applied to commercial measurement, should be noted that reasonable installation focus supersonic scanister, ensure that concentration ultrasonic is to measurement thing field disturbance effectively.
Schematic above the present invention and embodiment thereof to be described; this description is not restricted; shown in accompanying drawing is also one embodiment of the present invention; if any those of ordinary skill in the art when not departing from the invention aim; without create shape design the version similar with the present invention or embodiment, all should protection scope of the present invention be belonged to.
Claims (1)
1. one kind builds sensitivity matrix method based on focus ultrasonic disturbance information, the method is by the scanning disturbance of concentration ultrasonic to measurement thing field, utilize the boundary survey voltage vector of focus supersonic wave disturbance fore-and-aft survey, the sensitivity matrix of computation and measurement thing field, comprises following step:
1) focal spot size of focused transducer is measured
Make microphone aim at focused transducer, and make the sensing unit of microphone be in the focal spot place of focused transducer, regulate the position of microphone, measure the focal spot size of focused transducer;
2) measurement thing field is divided into I disturbance region, determines the positional information of each disturbance region, and concentration ultrasonic intends the scanning sequency to each disturbance region
The focal spot size obtained is measured according in measurement thing field size and step 1, measurement thing field is divided into I disturbance region, division principle is: focused transducer can complete the scanning to whole measurement thing field, and each disturbance region is not overlapping, and disturbance region is focal spot institute overlay area; Record the positional information of each disturbance region, and determine that concentration ultrasonic intends the scanning sequency to each disturbance region, from 1 to I;
3) without in focus ultrasonic situation, to excitation, the measurement of measuring thing field enforcement electricity tomography, boundary survey voltage vector φ is obtained
By applying current excitation or voltage drive on exciting electrode, realize applying electrical stimuli to measurement thing field, gather the boundary voltage in each potential electrode under cycle motivation circulation measurement pattern, form boundary survey voltage vector φ, complete and once encourage measuring process;
4) in focus ultrasonic situation, each disturbance region i of focus supersonic wave disturbance, simultaneously again to excitation, the measurement of measuring thing field enforcement electricity tomography, obtains boundary survey voltage vector φ
i
By focused transducer perpendicular to measurement thing field, to each disturbance region i, 1≤i≤I, while focus supersonic wave disturbance, all complete a step 3) in the excitation measuring process of electrod-array, measure the boundary survey voltage vector φ of thing field when obtaining focus supersonic this disturbance region of wave disturbance
i;
5) step 3 is utilized) and step 4) measure the boundary voltage signal psi and φ that obtain respectively
i, by the Sensitirity va1ue of following formulae discovery each disturbance region i position, be designated as A
i,
A
i＝φ
i-φ
A
ibe the Sensitirity va1ue measuring each disturbance region i position, thing field;
6) the sensitivity profile A of whole measurement thing field is obtained
By the Sensitirity va1ue of each disturbance region position, integrating step 1) in the positional information of each disturbance region, obtain the sensitivity profile A of whole measurement thing field.
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