CN109513123B - High-resolution three-dimensional passive cavitation imaging method based on hemispherical array - Google Patents
High-resolution three-dimensional passive cavitation imaging method based on hemispherical array Download PDFInfo
- Publication number
- CN109513123B CN109513123B CN201811627424.5A CN201811627424A CN109513123B CN 109513123 B CN109513123 B CN 109513123B CN 201811627424 A CN201811627424 A CN 201811627424A CN 109513123 B CN109513123 B CN 109513123B
- Authority
- CN
- China
- Prior art keywords
- cavitation
- array
- ultrasonic
- imaging
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000003384 imaging method Methods 0.000 title claims abstract description 90
- 239000011159 matrix material Substances 0.000 claims abstract description 39
- 238000000034 method Methods 0.000 claims abstract description 28
- 238000011068 loading method Methods 0.000 claims abstract description 15
- 230000006835 compression Effects 0.000 claims abstract description 4
- 238000007906 compression Methods 0.000 claims abstract description 4
- 230000010354 integration Effects 0.000 claims description 4
- 230000004044 response Effects 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 230000007547 defect Effects 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 description 9
- 230000009467 reduction Effects 0.000 description 5
- 238000009210 therapy by ultrasound Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 238000012544 monitoring process Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000005070 sampling Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 230000003044 adaptive effect Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- 238000002604 ultrasonography Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000008499 blood brain barrier function Effects 0.000 description 2
- 210000001218 blood-brain barrier Anatomy 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 238000002560 therapeutic procedure Methods 0.000 description 2
- 208000003174 Brain Neoplasms Diseases 0.000 description 1
- 238000002679 ablation Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000007917 intracranial administration Methods 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 238000011897 real-time detection Methods 0.000 description 1
- 210000003625 skull Anatomy 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 230000002537 thrombolytic effect Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Images
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N7/00—Ultrasound therapy
- A61N7/02—Localised ultrasound hyperthermia
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N7/00—Ultrasound therapy
- A61N2007/0004—Applications of ultrasound therapy
- A61N2007/0021—Neural system treatment
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/022—Liquids
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Acoustics & Sound (AREA)
- Animal Behavior & Ethology (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Biomedical Technology (AREA)
- Veterinary Medicine (AREA)
- Engineering & Computer Science (AREA)
- Radiology & Medical Imaging (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
Abstract
The invention provides a high-resolution three-dimensional passive cavitation imaging method based on a hemispherical array, which comprises the following steps: the method comprises the steps of delaying cavitation signals passively received by an ultrasonic hemispherical array transducer, constructing a covariance matrix, carrying out diagonal loading processing on the covariance matrix, calculating an optimal weighting vector according to the diagonally loaded covariance matrix, weighting the delay signals by using the optimal weighting vector, combining and superposing the obtained delay weighted signals to obtain an aperture autocorrelation output signal, then extracting a second harmonic component from the aperture autocorrelation output signal, calculating the cavitation intensity of an imaging position in a three-dimensional imaging area, and carrying out linear interpolation and logarithmic compression to obtain a high-resolution three-dimensional passive cavitation image. The invention can effectively reduce the width of the main lobe and the level of the side lobe and overcome the defects of the traditional hemisphere array passive cavitation imaging method in the aspect of space resolution performance.
Description
Technical Field
The invention belongs to the technical field of ultrasonic detection and ultrasonic imaging, and particularly relates to a high-resolution three-dimensional passive cavitation imaging method based on a hemispherical array.
Background
The cavitation detection and imaging technology is always a hotspot of research in the biomedical ultrasound field, and can be divided into an active type and a passive type according to the working mode of an ultrasonic transducer, wherein the active cavitation detection and imaging are realized mainly by transmitting focused wave pulses or plane wave pulses and simultaneously receiving cavitation signals by a single-array-element ultrasonic transducer and a diagnosis ultrasonic transducer. In the passive detection and imaging of the cavitation, the transmission of the ultrasonic transducer is closed, and only the cavitation signal is passively received, so that the influence of the focused ultrasonic signal generating the cavitation on the transmission pulse is avoided, and the real-time detection and imaging of the cavitation in the focused ultrasonic irradiation process can be realized.
In the passive detection and imaging of cavitation, the one-dimensional time detection mainly utilizes a single-array-element ultrasonic transducer to passively receive a cavitation signal to study the change rule of cavitation activity along with time, analyzes the frequency characteristic of cavitation according to Fourier transform, and further utilizes a frequency spectrum to calculate the cavitation dose, thereby realizing the quantitative analysis of cavitation. However, the cavitation itself is a random transient physical process, and the position and distribution of the cavitation in the space cannot be obtained by one-dimensional time detection, so that effective characterization of the cavitation generated in the focused ultrasound treatment process is difficult. Therefore, in recent years, a two-dimensional planar imaging technology for cavitation has been developed, which is developed on the basis of one-dimensional time detection, and mainly includes closing the transmission of a linear array transducer or a phased array transducer to enable all array elements to receive cavitation signals at the same time, and then performing image reconstruction according to a passive beam forming algorithm, so as to perform real-time monitoring and feedback on cavitation generated in focused ultrasound therapy.
The two-dimensional passive cavitation imaging technology can only see one plane, can not realize the omnibearing monitoring of cavitation in a three-dimensional space, and is not suitable for parts needing fine treatment, such as the cranium. In transcranial ultrasound treatment, such as blood brain barrier opening, researchers have implemented real-time monitoring of cavitation activity during transcranial ultrasound treatment using an ultrasonic hemispherical array transducer, wherein the ultrasonic hemispherical array transducer is slightly larger than the human skull in size, and the geometric focal length is the center of a hemisphere. The surface of the ultrasonic hemispherical array transducer is distributed with a plurality of array elements, the array elements can acquire cavitation signals generated in the transcranial ultrasonic treatment process, and the distribution of the intracranial cavitation in a three-dimensional space can be obtained by adopting a beam forming algorithm for reconstruction. And because the aperture of the hemispherical array is much larger than that of a linear array transducer or a phased array transducer, the imaging resolution performance of the hemispherical array is better than that of a one-dimensional array. However, the most traditional delay, superposition and integration method is adopted in the existing hemispherical array passive cavitation imaging method, and the method is a blind beam synthesis method, can generate larger main lobe width and higher side lobe level, and reduces the spatial accuracy degree of cavitation source positioning, thereby being not beneficial to detection and imaging of the transcranial focused ultrasound treatment cavitation.
In view of the above, it is necessary to provide a high-resolution three-dimensional passive cavitation imaging method based on a hemispherical array.
Disclosure of Invention
The invention aims to provide a high-resolution three-dimensional passive cavitation imaging method based on a hemispherical array.
In order to achieve the purpose, the invention adopts the following technical scheme:
the method comprises the following steps: calculating the distance between any imaging position in the interested three-dimensional imaging area and each array element position of the ultrasonic hemispherical array transducer; acquiring and storing cavitation signals passively received by each array element of the ultrasonic hemispherical array transducer;
step two: according to the distance between a certain imaging position in the interested three-dimensional imaging area and each array element position of the ultrasonic hemispherical array transducer, carrying out time delay processing on the cavitation signal obtained in the step one to obtain a time delay signal, constructing a covariance matrix by using the time delay signal, carrying out diagonal loading on the covariance matrix to improve the robustness of the covariance matrix, and calculating an optimal weighting vector according to the diagonally loaded covariance matrix and a guide vector;
step three: weighting the delay signals by using the optimal weighting vector obtained in the step two to obtain delay weighted signals of each array element of the ultrasonic hemispherical array transducer, multiplying the delay weighted signals of every two array elements in the ultrasonic hemispherical array transducer, performing symbolization, absolute value conversion and evolution processing to obtain combined signals, superposing all the combined signals of each array element of the ultrasonic hemispherical array transducer to obtain the summed signals of the array element, and superposing all the summed signals to obtain aperture autocorrelation output signals;
step four: extracting a second harmonic component from the output signal of the aperture autocorrelation obtained in the step three, and integrating the square of the second harmonic component in a certain time interval to obtain the cavitation intensity of an imaging position in the interested three-dimensional imaging area;
step five: and repeating the second step to the fourth step until obtaining the cavitation intensity of all imaging positions in the interested three-dimensional imaging area, and obtaining a three-dimensional passive cavitation image according to the cavitation intensity.
Preferably, in the step one, the ultrasonic hemispherical array transducer works in a mode of only passive receiving but not transmitting, the ultrasonic hemispherical array transducer is matched with the programmable digital ultrasonic imaging platform, and transmitting is setApodizing, receiving apodization parameter, and collecting cavitation signal p by programmable digital ultrasonic imaging platformi(t); a certain imaging position (x, y, z) in the three-dimensional imaging region of interest and each array element position (x) of the ultrasonic hemispherical array transduceri,yi,zi) The distance between them is calculated using the following formula:
wherein, a rectangular coordinate system is established by taking the sphere center of the ultrasonic hemispherical array transducer as an origin, and the spatial coordinate x of each array element of the ultrasonic hemispherical array transducer is calculatedi、yiAnd ziX, y and z are spatial coordinates of the certain imaging position in the coordinate system; wherein, i is 1,2, N is the number of array elements of the ultrasonic hemispherical array transducer.
Preferably, the second step specifically comprises the following steps:
(2.1) for the collected cavitation signal pi(t) carrying out delay processing to obtain a delay signal of each array element:
si(t,x,y,z)＝pi[t+di(x,y,z)/c]
wherein c is the sound propagation speed in the medium;
(2.2) constructing a delay signal matrix s (t, x, y, z) [ s ] according to the delay signal of each array element obtained in the step (2.1)1(t,x,y,z)；s2(t,x,y,z,t)；...；sN(t,x,y,z)]According to the constructed delay signal matrix in the cavitation signal acquisition time interval [ T ]0,T0+ΔT]Constructing a covariance matrix:
wherein, T0The time is the initial time of cavitation signal acquisition, and the delta T is the time length of the cavitation signal acquisition;
and (2.3) carrying out diagonal loading on the covariance matrix obtained in the step (2.2), and then calculating the optimal weighting vector of the self-adaptive beam forming according to the covariance matrix and the steering vector after the diagonal loading:
wherein,
is a covariance matrix after diagonal loading, a ═ 1,1]TIs a steering vector of N rows by 1 column.
Preferably, the third step specifically comprises the following steps:
(3.1) weighting the delay signal of each array element obtained in the step (2.1) according to the optimal weighting vector obtained in the step (2.3) to obtain a delay weighted signal of each array element:
wherein, wiThe ith element of the optimal weighting vector w obtained in the step (2.3), wherein i is 1, 2.
(3.2) multiplying the delay weighted signals of the ith array element and the jth array element:
wherein, i is 1, 2., N-1, j is i +1, i + 2., N;
(3.3) performing symbolization, absolute value and evolution processing on the multiplication result obtained in the step (3.2) to obtain a combined signal
Superposing all combined signals of the ith array element to obtain a summation signal of the ith array element (i ═ 1, 2.., N-1):
and (3.4) superposing the summation signals of the N-1 array elements obtained in the step (3.3) again to obtain an output signal of the aperture autocorrelation:
preferably, the step four specifically includes the following steps:
(4.1) extracting a second harmonic component from the output signal of the aperture autocorrelation obtained in step (3.4) by using a band-pass filter, namely:
h (t) is a unit impulse response of the band-pass filter, and represents convolution operation of a signal;
(4.2) squaring the second harmonic component obtained in the step (4.1) and collecting the second harmonic component in a cavitation signal collecting time interval [ T [ ]0,T0+ΔT]The integration is performed to obtain the intensity of the imaging position (x, y, z):
preferably, the step five specifically comprises the following steps: traversing all imaging positions in the interested three-dimensional imaging area, obtaining the intensity of all imaging positions, performing linear interpolation and logarithmic compression on the intensity to obtain a three-dimensional passive cavitation image, and setting a dynamic range to display the image.
Preferably, the three-dimensional imaging region of interest is centered on the center of a sphere of the ultrasonic hemispherical array transducer.
The invention has the beneficial effects that:
the invention relates to a high-resolution three-dimensional passive cavitation imaging technology for an ultrasonic hemispherical array transducer, aiming at the defects of the traditional hemispherical array passive cavitation imaging method, a cavitation signal passively received by a hemispherical array is subjected to time delay processing, a covariance matrix is further constructed according to the time delay signal and is subjected to diagonal loading processing to improve robustness, and then an optimal weighting vector is obtained to weight the time delay signal of each array element; and then, combining and superposing the delay weighted signals in pairs to obtain aperture autocorrelation output signals, and extracting second harmonic components from the aperture autocorrelation output signals, so that the main lobe width and the side lobe level in the x, y and z directions are effectively reduced, the spatial resolution performance of hemispherical array three-dimensional passive cavitation imaging is remarkably improved, and the positioning of a cavitation source in a three-dimensional space is more accurate.
Drawings
Fig. 1 is a three-dimensional view (a) and a top view (b) of an ultrasonic hemispherical array transducer in the present invention.
FIG. 2 is a flow chart of a high-resolution three-dimensional passive cavitation imaging method based on a hemispherical array in the invention.
Fig. 3 shows the results of the cavitation signal (a) and covariance matrix (b) collected by the hemispherical array, the covariance matrix (c) after diagonal loading, the spectrum distribution (d) of the delay weighted signal, the spectrum distribution (e) of the aperture autocorrelation output signal, and the extracted second harmonic component (f) in the present invention.
Fig. 4 shows the results of three-dimensional passive cavitation imaging according to the prior art and the proposed method.
FIG. 5 is a resolution curve obtained from the results of three-dimensional passive cavitation imaging.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Referring to fig. 1, the radius of an ultrasonic hemispherical array transducer (called a hemispherical array transducer for short) is 15cm, the number of array elements is 128, and the ultrasonic hemispherical array transducer can be directly matched with an existing ultrasonic imaging platform; different from an ultrasonic linear array transducer, all array elements of the ultrasonic hemispherical array transducer are not distributed at equal intervals completely, and the distance range between every two array elements shown in fig. 1 is 3.0-3.5 cm.
Referring to fig. 2, the high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array comprises the following specific steps:
(1) matching an ultrasonic hemispherical array transducer with a programmable digital ultrasonic imaging platform, and setting transmitting apodization sumReceiving apodization parameters, making the hemispherical array transducer work in a passive receiving mode instead of a transmitting mode, and collecting cavitation signals pi(t), wherein i is 1,2, and N is the number of array elements of the hemispherical array transducer;
(2) establishing a rectangular coordinate system by taking the sphere center of the hemispherical array as an origin, and calculating the space coordinate x of each array element in the hemispherical arrayi、yiAnd zi：
zi＝rcosθi
Wherein r is the radius of the hemispherical array, thetaiAnd
the azimuth angle and the pitch angle of the ith array element are respectively;
(3) setting a three-dimensional imaging area of interest as a cube area with the origin of a hemispherical array as the center, wherein the side length of the cube can be generally selected from 10mm to 30mm, and calculating an imaging position (x, y, z) in the three-dimensional imaging area and each array element position (x) of the hemispherical arrayi,yi,zi) The distance between:
(4) carrying out time delay processing on the acquired cavitation signals to obtain a time delay signal of each array element:
si(t,x,y,z)＝pi[t+di(x,y,z)/c]
wherein c is the sound propagation speed in the medium;
(5) constructing a delay signal matrix s (t, x, y, z) [ s ] according to the delay signals of each array element obtained in the step (4)1(t,x,y,z)；s2(t,x,y,z,t)；...；sN(t,x,y,z)]In the cavitation signal acquisition time interval [ T ]0,T0+ΔT]Constructing a covariance matrix:
wherein, T0Is the initial time of cavitation signal acquisition, and Δ T is the time length of cavitation signal acquisition [ ·]TRepresents a transpose of the matrix;
(6) when the sampling data is less, the covariance matrix estimation has errors, which causes the main lobe distortion and the side lobe increase of the self-adaptive beam synthesis; in order to obtain a robust covariance matrix under the limited data sampling condition, carrying out diagonal loading on the covariance matrix obtained in the step (5):
wherein, epsilon is set to be delta times of the trace of the covariance matrix R (x, y, z), namely epsilon is delta trace { R (x, y, z) }, trace {. cndot } represents the trace operation of the matrix, and I is an identity matrix of N rows by N columns;
(7) according to the covariance matrix after diagonal loading obtained in the step (6)
Calculating the optimal weighting vector of the adaptive beam forming:
wherein, a ═ 1, 1., 1]TA steering vector of N rows by 1 column [ ·]-1Representing the inversion of the matrix;
(8) weighting the delay signal of each array element obtained in the step (4) according to the optimal weighting vector obtained in the step (7) to obtain a delay weighted signal of each array element:
wherein, wiThe ith element of the optimal weighting vector w obtained in the step (7), wherein i is 1, 2.
(9) Multiplying the delay weighted signals of the ith array element and the jth array element:
wherein, i is 1, 2., N-1, j is i +1, i + 2., N;
(10) the result obtained by multiplying the delay weighted signals in the step (9) is multiplied with the delay weighted signal of the ith array element
So that the result is signed, absolute-valued, and squared to obtain a combined signal:
(11) from step (10), there will be N-1 combined signals for the 1 st element, N-2 combined signals for the 2 nd element, and so on, with 1 combined signal for the N-1 st element. Superposing all combined signals of the ith array element to obtain a summation signal of the ith array element (i ═ 1, 2.., N-1):
(12) adding the summation signals of the N-1 array elements obtained in the step (11) again, which is equivalent to performing autocorrelation processing (called aperture autocorrelation in the invention) on the receiving aperture of the hemispherical array transducer, so that the effective aperture is increased; the aperture autocorrelation output signal is:
(13) because the delay weighted signals of the ith array element and the jth array element in the step (9) have similar frequency spectrum distribution, direct current components and second harmonic components are respectively generated after multiplication, and the second harmonic components are selected for imaging in order to improve the imaging resolution;
(14) designing a band-pass filter to extract a second harmonic component from the output signal of the aperture autocorrelation obtained in step (12), namely:
h (t) is a unit impulse response of the band-pass filter, and represents convolution operation of a signal;
(15) squaring the second harmonic component obtained in the step (14) and collecting the second harmonic component in a cavitation signal collecting time interval [ T ]0,T0+ΔT]The integration is performed to obtain the intensity of the imaging position (x, y, z):
(16) and (5) repeating the steps (3) to (15) until the intensities of all the imaging positions in the interested three-dimensional imaging area are calculated, performing linear interpolation and logarithmic compression on the intensities of all the imaging positions to obtain a three-dimensional passive cavitation image, and setting a dynamic range to display the image.
The percentage of full width at half maximum reduction and the amplitude of side lobe level reduction are respectively adopted to quantitatively evaluate the advantages of the method in the two aspects of space resolution improvement and side lobe level inhibition compared with the prior method.
Finding the three-dimensional coordinate (x) of the maximum intensity value from the three-dimensional passive cavitation image0,y0,z0) Accordingly, resolution curves in the x, y and z directions are obtained. In order to evaluate the advantage of the method provided by the invention in the aspect of main lobe width reduction, firstly, the full width at half maximum (the width corresponding to the maximum intensity value reduced to-6 dB) of the obtained resolution curve is calculated, and then the percentage of full width reduction of the method provided by the invention compared with the existing method is calculated; to evaluateAnd obtaining the sidelobe levels in the x direction, the y direction and the z direction according to the obtained resolution curve, and then calculating the amplitude of the sidelobe level reduction of the method provided by the invention compared with the existing method.
Referring to fig. 3, fig. 3(a) shows the collected cavitation signal, wherein the focused ultrasound irradiation frequency is set to 0.3MHz, the sampling rate is set to 20MHz, and the number of sampling points is set to 4000 points; fig. 3(b) to fig. 3(f) are the results obtained when the imaging position is (0mm,0mm,0mm), where fig. 3(b) is the covariance matrix constructed according to step (5), fig. 3(c) is the covariance matrix obtained according to the diagonal loading method described in step (6) (where δ is set to 0.1), fig. 3(d) is the spectral distribution of the delay weighted signal described in step (8), and the result shows that the cavitation signal is a steady-state cavitation signal (the center frequency is 0.6MHz), fig. 3(e) is the spectral distribution of the aperture autocorrelation output signal described in step (12), and it is obvious that the aperture autocorrelation output signal has significant direct current component and second harmonic component (1.2MHz), and fig. 3(f) is the second harmonic component extracted according to step (14).
Referring to FIG. 4, taking the imaging result obtained by the cavitation source located at (0mm,0mm,0mm) as an example, FIG. 4(a), FIG. 4(b) and FIG. 4(c) are respectively the x-y section, x-z section and y-z section of the hemispherical array three-dimensional passive cavitation image obtained by the proposed method according to the present invention, FIG. 4(d), FIG. 4(e) and FIG. 4(f) are respectively the x-y section, x-z section and y-z section of the hemispherical array three-dimensional passive cavitation image obtained by the prior art method, and the dynamic range of the image display is set to 80 dB; obviously, the method provided by the invention can effectively improve the imaging quality, and the positioning of the cavitation source in the three-dimensional space is more accurate.
Referring to fig. 5, taking the resolution curves obtained from the cavitation source at (0mm,0mm,0mm) as an example, fig. 5(a), 5(b), 5(c) are the resolution curves in the x, y and z directions, respectively, wherein the results of the prior art method and the present invention method are shown in each figure. Compared with the prior art, the method provided by the invention has smaller half-height width and lower side lobe level; through calculation, the half widths in the x direction, the y direction and the z direction of the existing method are respectively 0.548mm, 0.557mm and 1.120mm, while the half widths of the method provided by the invention are respectively 0.180mm, 0.185mm and 0.566mm, namely the half widths are respectively reduced by 67.2%, 66.8% and 49.5%; the side lobe levels in the x direction, the y direction and the z direction of the existing method are respectively-99.4 dB, -99.8dB and-94.4 dB, while the side lobe levels of the method provided by the invention are respectively-51.0 dB, -49.5dB and-46.6 dB, namely the side lobe levels are respectively reduced by-48.4 dB, -50.3dB and-47.8 dB, and the above results quantitatively prove the superiority of the invention.
The invention has the following advantages:
the invention abandons the traditional hemispherical array three-dimensional passive cavitation imaging method, and organically combines the minimum variance adaptive beam synthesis and the aperture autocorrelation, wherein the adaptive beam synthesis improves the robustness of a covariance matrix through diagonal loading, and assigns a proper weight coefficient to the signal of each array element according to the obtained optimal weighting vector, so that the resolution of the imaging method is improved; the aperture autocorrelation processing is equivalent to further increasing the effective receiving aperture of the ultrasonic hemispherical array transducer, meanwhile, the multiplication of the delay weighted signals generates high-frequency second harmonic components, and the imaging resolution is improved again due to the increase of the aperture and the improvement of the frequency, so that the high-resolution three-dimensional passive cavitation imaging is finally realized.
The high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array can be used for all-around real-time monitoring in aspects of transcranial ultrasonic therapy, such as brain tumor ultrasonic thermal ablation, transcranial ultrasonic thrombolysis, blood brain barrier opening and the like, and has important significance for adjusting treatment parameters, optimizing treatment schemes, analyzing and evaluating treatment effects and the like.
Claims (7)
1. A high-resolution three-dimensional passive cavitation imaging method based on a hemispherical array is characterized in that: the method comprises the following steps:
the method comprises the following steps: calculating the distance between any imaging position in the interested three-dimensional imaging area and each array element position of the ultrasonic hemispherical array transducer; acquiring cavitation signals passively received by each array element of the ultrasonic hemispherical array transducer;
step two: according to the distance between a certain imaging position in the interested three-dimensional imaging area and each array element position of the ultrasonic hemispherical array transducer, carrying out time delay processing on the cavitation signal to obtain a time delay signal, constructing a covariance matrix by using the time delay signal, carrying out diagonal loading on the covariance matrix, and calculating an optimal weighting vector according to the diagonally loaded covariance matrix and a guide vector;
step three: weighting the delay signals by using the optimal weighting vector to obtain delay weighted signals of each array element of the ultrasonic hemispherical array transducer, multiplying the delay weighted signals of every two array elements in the ultrasonic hemispherical array transducer, performing symbolization, absolute value conversion and evolution processing to obtain combined signals, superposing all the combined signals of each array element of the ultrasonic hemispherical array transducer to obtain a summation signal of the array element, and superposing all the summation signals to obtain an aperture autocorrelation output signal;
step four: extracting a second harmonic component from the output signal of the aperture autocorrelation, and integrating the square of the second harmonic component in a certain cavitation signal acquisition time interval to obtain the cavitation intensity of the certain imaging position;
step five: and repeating the second step to the fourth step until obtaining the cavitation intensity of all imaging positions in the interested three-dimensional imaging area, and obtaining a three-dimensional passive cavitation image according to the cavitation intensity.
2. The high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array as claimed in claim 1, characterized in that: in the first step, the ultrasonic hemispherical array transducer works in a mode of only passive receiving but not transmitting, and a programmable digital ultrasonic imaging platform acquires a cavitation signal p received by the ultrasonic hemispherical array transduceri(t); the distance between a certain imaging position in the interested three-dimensional imaging area and each array element position of the ultrasonic hemispherical array transducer is calculated by adopting the following formula:
wherein x isi、yiAnd ziThe spatial coordinates of the ith array element of the ultrasonic hemispherical array transducer in a rectangular coordinate system established by taking the sphere center of the ultrasonic hemispherical array transducer as an origin are x, y and z, the spatial coordinates of a certain imaging position in the coordinate system are i 1, 2.
3. The high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array as claimed in claim 1, characterized in that: the second step specifically comprises the following steps:
(2.1) for the collected cavitation signal pi(t) carrying out time delay treatment to obtain a time delay signal of each array element of the ultrasonic hemispherical array transducer:
si(t,x,y,z)＝pi[t+di(x,y,z)/c]
where c is the speed of sound propagation in the medium and di(x, y, z) is the distance between the certain imaging position and the ith array element position of the ultrasonic hemispherical array transducer, and i is 1, 2.
(2.2) constructing a delay signal matrix s (t, x, y, z) [ s ] according to the delay signal of each array element obtained in the step (2.1)1(t,x,y,z)；s2(t,x,y,z,t)；...；sN(t,x,y,z)]According to the constructed delay signal matrix in the cavitation signal acquisition time interval [ T ]0,T0+ΔT]Constructing a covariance matrix:
wherein, T0The time is the initial time of cavitation signal acquisition, and the delta T is the time length of the cavitation signal acquisition;
and (2.3) carrying out diagonal loading on the covariance matrix obtained in the step (2.2), and calculating the optimal weighting vector of self-adaptive beam forming according to the covariance matrix and the steering vector after diagonal loading:
wherein,
and a is a guide vector for the covariance matrix after diagonal loading.
4. The high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array as claimed in claim 1, characterized in that: the third step specifically comprises the following steps:
(3.1) weighting the delay signal of each array element of the ultrasonic hemispherical array transducer according to the optimal weighting vector to obtain the delay weighted signal of each array element:
wherein, wiIs the ith element, s, of the optimal weight vector wi(t, x, y, z) is a delay signal of the ith array element, i is 1, 2.
(3.2) multiplying the delay weighted signals of the ith array element and the jth array element:
wherein, i is 1, 2., N-1, j is i +1, i + 2., N;
(3.3) performing symbolization, absolute value and evolution processing on the multiplication result obtained in the step (3.2) to obtain a combined signal
And superposing all the combined signals of the ith array element to obtain a summation signal of the ith array element, wherein i is 1, 2.
And (3.4) superposing the summation signals of the N-1 array elements obtained in the step (3.3) again to obtain an output signal of the aperture autocorrelation:
5. the high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array as claimed in claim 1, characterized in that: the fourth step specifically comprises the following steps:
(4.1) extracting a second harmonic component from the output signal of the aperture autocorrelation with a band pass filter:
wherein, Q (t, x, y, z) is the output signal of the aperture autocorrelation, h (t) is the unit impulse response of the band-pass filter, and represents the convolution operation of the signal;
(4.2) squaring the second harmonic component obtained in the step (4.1) and collecting the second harmonic component in a cavitation signal collecting time interval [ T [ ]0,T0+ΔT]The integration is performed to obtain the intensity of the imaging position (x, y, z):
and x, y and z are space coordinates of the certain imaging position in a rectangular coordinate system established by taking the spherical center of the ultrasonic hemispherical array transducer as an origin.
6. The high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array as claimed in claim 1, characterized in that: the fifth step specifically comprises the following steps: traversing all imaging positions in the interested three-dimensional imaging region, obtaining the intensity of the corresponding imaging position according to the second step to the fifth step, then performing linear interpolation and logarithmic compression on the intensities of all the imaging positions to obtain a three-dimensional passive cavitation image, and then setting a dynamic range to display the image.
7. The high-resolution three-dimensional passive cavitation imaging method based on the hemispherical array as claimed in claim 1, characterized in that: the three-dimensional imaging region of interest is centered on the center of the sphere of the ultrasonic hemispherical array transducer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811627424.5A CN109513123B (en) | 2018-12-28 | 2018-12-28 | High-resolution three-dimensional passive cavitation imaging method based on hemispherical array |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811627424.5A CN109513123B (en) | 2018-12-28 | 2018-12-28 | High-resolution three-dimensional passive cavitation imaging method based on hemispherical array |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109513123A CN109513123A (en) | 2019-03-26 |
| CN109513123B true CN109513123B (en) | 2020-05-19 |
Family
ID=65798477
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811627424.5A Active CN109513123B (en) | 2018-12-28 | 2018-12-28 | High-resolution three-dimensional passive cavitation imaging method based on hemispherical array |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109513123B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110575201B (en) * | 2019-10-09 | 2021-12-24 | 珠海医凯电子科技有限公司 | Ultrasonic microbubble cavitation imaging method and device based on reverse Golay code |
| CN111415408B (en) * | 2020-04-14 | 2022-06-07 | 西安交通大学 | Microsecond-level multi-scale space-time imaging and feature map calculation method and system for ultrasonic cavitation |
| CN112023283B (en) * | 2020-08-03 | 2021-09-07 | 西安交通大学 | Annular multi-array ultrasonic passive imaging method and system based on high-order aperture autocorrelation |
| CN112218239B (en) * | 2020-09-04 | 2023-03-10 | 北京爱笔科技有限公司 | Position determination method, position determination device, computer equipment and storage medium |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103267800A (en) * | 2013-05-03 | 2013-08-28 | 西安交通大学 | Cavitation micro-bubble high signal-to-noise ratio ultrasonic rapidly imaging and dynamic dimension distribution estimating method |
| WO2017126037A1 (en) * | 2016-01-19 | 2017-07-27 | オリンパス株式会社 | Ultrasonic medical device |
| US9743909B1 (en) * | 2013-05-15 | 2017-08-29 | University Of Washington Through Its Center For Commercialization | Imaging bubbles in a medium |
| CN108324324A (en) * | 2018-03-12 | 2018-07-27 | 西安交通大学 | It is a kind of ultrasound low frequency through cranial capacity super-resolution three-dimensional contrast imaging method and system |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103175761B (en) * | 2013-03-13 | 2015-10-28 | 西安交通大学 | A kind of method that evanishment is in the solution estimated microvesicle group Size Distribution |
| CN104535645B (en) * | 2014-12-27 | 2016-06-29 | 西安交通大学 | Microsecond differentiates the three-dimensional cavitation quantitative imaging method of cavitation spatial and temporal distributions |
| EP3503974A1 (en) * | 2016-08-26 | 2019-07-03 | Koninklijke Philips N.V. | Detection of treatment failure for mild hyperthermia |
| CN107260217B (en) * | 2017-07-17 | 2018-07-17 | 西安交通大学 | The passive imaging method of three-dimensional and system for brain focused ultrasonic cavitation real time monitoring |
-
2018
- 2018-12-28 CN CN201811627424.5A patent/CN109513123B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103267800A (en) * | 2013-05-03 | 2013-08-28 | 西安交通大学 | Cavitation micro-bubble high signal-to-noise ratio ultrasonic rapidly imaging and dynamic dimension distribution estimating method |
| US9743909B1 (en) * | 2013-05-15 | 2017-08-29 | University Of Washington Through Its Center For Commercialization | Imaging bubbles in a medium |
| WO2017126037A1 (en) * | 2016-01-19 | 2017-07-27 | オリンパス株式会社 | Ultrasonic medical device |
| CN108324324A (en) * | 2018-03-12 | 2018-07-27 | 西安交通大学 | It is a kind of ultrasound low frequency through cranial capacity super-resolution three-dimensional contrast imaging method and system |
Non-Patent Citations (3)
| Title |
|---|
| "看清"颅内血管——高分辨率经颅超声诊疗***;宗瑜瑾 路舒宽 万明习;《中国医学物理学杂志》;20161231;全文 * |
| 3-D Finite Element Analysis on Brain Injury Mechanism;Y. Kurosawa;《30th Annual International IEEE EMBS Conference》;20080824;全文 * |
| Transcranial Assessment and Visualization;Costas D. Arvanitis;《IEEE TRANSACTIONS ON MEDICAL IMAGING》;20150630;全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109513123A (en) | 2019-03-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109513123B (en) | High-resolution three-dimensional passive cavitation imaging method based on hemispherical array | |
| Nguyen et al. | A spatial coherence approach to minimum variance beamforming for plane-wave compounding | |
| JP6932192B2 (en) | Methods and systems for filtering ultrasound image clutter | |
| Nilsen et al. | Beamspace adaptive beamforming for ultrasound imaging | |
| US8254654B2 (en) | Sidelobe suppression in ultrasound imaging using dual apodization with cross-correlation | |
| CN103536316B (en) | Method for self-adaptation ultrasonic imaging of spatio-temporally smoothed coherence factor type | |
| US7867166B2 (en) | Statistical estimation of ultrasonic propagation parameters for aberration correction | |
| CN109431536B (en) | A kind of the Real-time High Resolution spatial and temporal distributions imaging method and system of focused ultrasonic cavitation | |
| EP4169451A1 (en) | Systems and methods for improving ultrasound image quality by applying weighting factors | |
| CN108670304B (en) | Ultrasonic plane wave imaging method based on improved DMAS algorithm | |
| Wang et al. | MVDR-based coherence weighting for high-frame-rate adaptive imaging | |
| US11737733B2 (en) | Method of, and apparatus for, determination of position in ultrasound imaging | |
| CN111265245B (en) | Passive cavitation imaging method and system based on double-constraint robust Capon beam synthesis and multiple apodization cross-correlation | |
| CN104887266B (en) | Method for small-area three-dimensional passive cavitation imaging and three-dimensional composite imaging based on area array | |
| CN112023283B (en) | Annular multi-array ultrasonic passive imaging method and system based on high-order aperture autocorrelation | |
| CN106940883B (en) | Ultrasonic imaging method based on point spread function simulation and compressed sensing of ultrasonic system | |
| Mamistvalov et al. | Compressed Fourier-domain convolutional beamforming for sub-Nyquist ultrasound imaging | |
| CN107137111A (en) | A kind of Ultrasound beamforming method | |
| Sakhaei | Optimum beamforming for sidelobe reduction in ultrasound imaging | |
| Guenther et al. | Optimal apodization design for medical ultrasound using constrained least squares part II simulation results | |
| CN114519752A (en) | High-resolution fast-calculation passive ultrasonic imaging method and system | |
| Xu et al. | Adaptive minimum variance beamforming combined with phase coherence imaging for ultrasound imaging | |
| Wang et al. | A mixed transmitting–receiving beamformer with a robust generalized coherence factor: Enhanced resolution and contrast | |
| Wang et al. | High frame rate adaptive imaging using coherence factor weighting and the MVDR method | |
| Avanji et al. | Adaptive 3D MV beamforming in medical ultrasound imaging |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |