CN112330764B - Biological endoscopic photoacoustic image reconstruction method and system for compensating acoustic reflection - Google Patents
Biological endoscopic photoacoustic image reconstruction method and system for compensating acoustic reflection Download PDFInfo
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- A—HUMAN NECESSITIES
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Abstract
The invention relates to a method and a system for reconstructing a biological endoscopic photoacoustic image by compensating acoustic reflection. The method comprises the following steps: acquiring plane ultrasonic waves generated by an imaging plane in a simulated tissue by adopting a numerical simulation method; acquiring an original optical signal in an imaging plane in the imaging catheter by using an ultrasonic detector; determining an ideal photoacoustic signal using the planar ultrasound and the original optical signal; and determining an initial sound pressure distribution image after suppressing the reflection artifact on the imaging plane according to the ideal photoacoustic signal. The invention reduces the reflection artifact in the image and improves the image quality.
Description
Technical Field
The invention relates to the technical field of medical imaging, in particular to a method and a system for reconstructing a biological endoscopic photoacoustic image by compensating acoustic reflection.
Background
In biological Endoscopic Photoacoustic tomography (EPAT), the acoustic characteristics of biological tissues have non-uniformity of spatial distribution, and when ultrasonic waves (i.e., photoacoustic signals) generated by Photoacoustic effect propagate in the tissues in all directions, a part of the ultrasonic waves propagating away from an ultrasonic detector may be reflected by sound-dense tissues located at a deeper layer and propagate back to the surface of the detector, similar to a virtual sound source, resulting in problems of reflection artifacts, distortion, reduced imaging depth, and the like in Photoacoustic images. In order to improve the imaging quality, the acoustic reflection problem is a key problem to be solved by the endoscopic photoacoustic tomography technology.
Disclosure of Invention
The invention aims to provide a method and a system for reconstructing a biological endoscopic photoacoustic image by compensating acoustic reflection so as to reduce reflection artifacts in the image and improve the image quality.
In order to achieve the purpose, the invention provides the following scheme:
a method of biological endoscopic photoacoustic image reconstruction with compensation for acoustic reflections, comprising:
acquiring plane ultrasonic waves generated by an imaging plane in a simulated tissue by adopting a numerical simulation method;
acquiring an original optical signal in an imaging plane in the imaging catheter by using an ultrasonic detector; an imaging plane in the imaging catheter is perpendicular to the imaging catheter; the ultrasonic detector is positioned at the top end of the imaging catheter;
determining an ideal photoacoustic signal using the planar ultrasound and the original optical signal; the ideal photoacoustic signal is a photoacoustic signal that does not include clutter;
and determining an initial sound pressure distribution image after suppressing the reflection artifact on the imaging plane according to the ideal photoacoustic signal.
Optionally, the obtaining of the planar ultrasonic wave generated by the imaging plane in the simulated tissue by using the numerical simulation method specifically includes:
establishing an X-Y plane rectangular coordinate system on the imaging plane by taking the center of the imaging guide pipe as a coordinate origin, taking the horizontal rightward direction as the positive direction of an X axis and taking the direction vertical to the X axis as the positive direction of a Y axis;
using formulas
Determining the plane ultrasonic wave;
wherein the content of the first and second substances,
to point to an amplitude of k t X has a component of k x The unit vector of the wave vector of (a),
e σ is a unit vector of the directed plane ultrasonic wave, e σ ＝(cosσ,sinσ) T R = (x, y) is a point in the imaging plane; omega belongs to R 2 Is a two-dimensional imaging region; sigma belongs to [0 DEG, 360 DEG ] is the incident angle of the single plane ultrasonic wave relative to the positive direction of the X axis; p is a radical of us (r,k t σ) is the incident angle σ and the wave number k t The sound pressure of the planar ultrasonic wave at the position r; k is a radical of t = ω/c is the wave number of the plane ultrasonic wave; c is the propagation velocity of the ultrasound in the tissue; ω is the frequency of the ultrasonic wave; k is a radical of x Is ultrasonic along the X-axisSpatial wave number in the positive direction, and | k x |＜k t ；γ ρ (r) and γ κ (r) an acoustic heterogeneity parameter, γ, related to density and compressibility, respectively κ (r)＝κ(r)/κ 0 (r)-1，γ ρ (r)＝1-ρ 0 (r)/ρ(r)，ρ 0 (r) and κ 0 (r) is the density and compressibility, respectively, of the homogeneous medium at location r, and ρ (r) and κ (r) are the density and compressibility, respectively, of the heterogeneous medium at location r.
Optionally, the determining an ideal photoacoustic signal by using the planar ultrasonic wave and the original optical signal specifically includes:
using formulas
Determining the ideal photoacoustic signal;
wherein, P us (r n ,σ l ) Is a position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix,
original photoacoustic signal matrix P of NxM dimensions pa E is the identity matrix and β is the dimensional factor.
Optionally, the determining an initial sound pressure distribution image after suppressing a reflection artifact on the imaging plane according to the ideal photoacoustic signal specifically includes:
and carrying out normalization and graying processing on the ideal photoacoustic signal, and determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
A system for biological endoscopic photoacoustic image reconstruction with compensation for acoustic reflections, comprising:
the plane ultrasonic wave determining module is used for acquiring plane ultrasonic waves generated by an imaging plane in a simulated tissue by adopting a numerical simulation method;
the original optical signal acquisition module is used for acquiring an original optical signal in an imaging plane in the imaging catheter by using the ultrasonic detector; an imaging plane in the imaging catheter is perpendicular to the imaging catheter; the ultrasonic detector is positioned at the top end of the imaging catheter;
an ideal photoacoustic signal determining module for determining an ideal photoacoustic signal using the planar ultrasonic wave and the original optical signal; the ideal photoacoustic signal is a photoacoustic signal that does not include clutter;
and the initial sound pressure distribution image determining module is used for determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane according to the ideal photoacoustic signal.
Optionally, the planar ultrasonic determination module specifically includes:
the plane rectangular coordinate system building unit is used for building an X-Y plane rectangular coordinate system on the imaging plane by taking the center of the imaging guide pipe as a coordinate origin, taking the horizontal rightward direction as the positive direction of an X axis and taking the direction vertical to the X axis as the positive direction of a Y axis;
a plane ultrasonic wave determining unit for using the formula
Determining the plane ultrasonic wave;
wherein, the first and the second end of the pipe are connected with each other,
to point at an amplitude of k t X component is k x The unit vector of the wave vector of (a),
e σ as a unit vector of the directed planar ultrasonic wave, e σ ＝(cosσ,sinσ) T R = (x, y) is a point in the imaging plane; omega belongs to R 2 Is a two-dimensional imaging region; sigma belongs to [0 DEG, 360 DEG ] is the incident angle of the single plane ultrasonic wave relative to the positive direction of the X axis; p is a radical of us (r,k t σ) is the incident angle σ and the wave number k t The sound pressure of the planar ultrasonic wave at the position r; k is a radical of t = ω/c is the wave number of the plane ultrasonic wave; c is the propagation velocity of the ultrasound in the tissue; ω is the frequency of the ultrasonic wave; k is a radical of x Is ultrasonic wave along the positive direction of X-axisSpace wave number of (1), and | k x |＜k t ；γ ρ (r) and γ κ (r) an acoustic heterogeneity parameter, γ, related to density and compressibility, respectively κ (r)＝κ(r)/κ 0 (r)-1，γ ρ (r)＝1-ρ 0 (r)/ρ(r)，ρ 0 (r) and κ 0 (r) is the density and compressibility, respectively, of the homogeneous medium at location r, and ρ (r) and κ (r) are the density and compressibility, respectively, of the heterogeneous medium at location r.
Optionally, the ideal photoacoustic signal determining module specifically includes:
an ideal photoacoustic signal determining unit for utilizing the formula
Determining the ideal photoacoustic signal;
wherein, P us (r n ,σ l ) Is a position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix,
original photoacoustic signal matrix P of NxM dimensions pa E is the identity matrix and β is the dimensional factor.
Optionally, the initial sound pressure distribution image determining module specifically includes:
and the initial sound pressure distribution image determining unit is used for carrying out normalization and graying processing on the ideal photoacoustic signal and determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
according to the method and the system for reconstructing the biological endoscopic photoacoustic image for compensating the acoustic reflection, provided by the invention, the planar ultrasonic wave generated by the imaging plane in the simulated tissue is obtained by adopting a numerical simulation method, namely the planar ultrasonic wave is generated by adopting the numerical simulation method and is used for simulating the photoacoustic signal generated by the tissue. Acquiring an original optical signal in an imaging plane in an imaging catheter by using an ultrasonic detector, namely sampling at different angles in acoustic inhomogeneous tissues by using the ultrasonic detector to obtain the original optical signal; determining an ideal photoacoustic signal using the planar ultrasonic wave and the original optical signal; and determining an initial sound pressure distribution image after suppressing the reflection artifact on the imaging plane according to the ideal photoacoustic signal. The invention can effectively reduce the reflection artifacts in the EPAT image, improve the focusing effect of the image and improve the imaging precision.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a schematic flow chart of a method for reconstructing a biological endoscopic photoacoustic image by compensating acoustic reflection according to the present invention;
FIG. 2 is a schematic diagram of the EPAT imaging principle of a cross section of a cavity;
FIG. 3 is a schematic view of the incidence of a single plane ultrasonic wave;
fig. 4 is a schematic structural diagram of a system for reconstructing a biological endoscopic photoacoustic image with compensated acoustic reflection according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for reconstructing a biological endoscopic photoacoustic image by compensating acoustic reflection so as to reduce reflection artifacts in the image and improve the image quality.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic flow chart of a method for reconstructing a biological endoscopic photoacoustic image by compensating for acoustic reflection according to the present invention, and as shown in fig. 1, the method for reconstructing a biological endoscopic photoacoustic image by compensating for acoustic reflection according to the present invention comprises:
s101, acquiring plane ultrasonic waves generated by an imaging plane in the simulated tissue by adopting a numerical simulation method.
S101 specifically includes:
an X-Y plane rectangular coordinate system is established on the imaging plane with the center of the imaging catheter as the origin of coordinates, the horizontal rightward direction as the positive direction of the X axis, and the direction perpendicular to the X axis as the positive direction of the Y axis, as shown in fig. 2.
Using formulas
The planar ultrasound is determined.
Wherein the content of the first and second substances,
to point to an amplitude of k t X component is k x The unit vector of the wave vector of (a),
e σ as a unit vector of the directed planar ultrasonic wave, e σ ＝(cosσ,sinσ) T R = (x, y) is a point in the imaging plane as shown in fig. 3; omega belongs to R 2 Is a two-dimensional imaging region; sigma belongs to [0 DEG, 360 DEG ] is the incident angle of the single plane ultrasonic wave relative to the positive direction of the X axis; p is a radical of us (r,k t σ) is the incident angle σ and the wave number k t The sound pressure of the planar ultrasonic wave at the position r; k is a radical of t = ω/c is the wave number of the plane ultrasonic wave; c is the propagation velocity of the ultrasound in the tissue; ω is the frequency of the ultrasonic wave; k is a radical of x Is the spatial wave number of the ultrasonic wave in the positive direction of the X axis, and k x |＜k t ；γ ρ (r) and γ κ (r) an acoustic heterogeneity parameter, γ, related to density and compressibility, respectively κ (r)＝κ(r)/κ 0 (r)-1，γ ρ (r)＝1-ρ 0 (r)/ρ(r)，ρ 0 (r) and κ 0 (r) is the density and compressibility, respectively, of the homogeneous medium at location r, and ρ (r) and κ (r) are the density and compressibility, respectively, of the heterogeneous medium at location r.
S102, acquiring an original optical signal in an imaging plane in the imaging catheter by using an ultrasonic detector; an imaging plane in the imaging catheter is perpendicular to the imaging catheter; the ultrasound probe is located at the tip of the imaging catheter.
S103, determining an ideal photoacoustic signal by using the plane ultrasonic wave and the original optical signal; the ideal photoacoustic signal is a photoacoustic signal that does not include clutter.
S103 specifically comprises the following steps:
using formulas
The ideal photoacoustic signal is determined.
Wherein, P us (r n ,σ l ) Is a position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix,
original photoacoustic signal matrix P of dimension N x M pa E is the identity matrix and β is the dimensional factor.
The process of specifically determining the ideal photoacoustic signal is as follows:
using the formula p pa (r,t)＝p h (r,t)+p sc (r, t) determines that the original photoacoustic signal is a superposition of the ideal photoacoustic signal and the reflected clutter signal.
Wherein t is from [0,T ∈ [ ]]Is the measurement time of the ultrasound probe, T is the measurement time limit; p is a radical of pa (r,t)、p h (r, t) and p sc (r, t) are the original photoacoustic signal at time t at location r in the imaging plane, respectivelyThe acoustic pressure of the desired photoacoustic signal and the reflected clutter signal.
Will be formula p pa (r,t)＝p h (r,t)+p sc (r, t) into a frequency domain matrix, i.e. P pa ＝P h +P sc 。
Wherein, P pa Is an N × M dimensional original photoacoustic signal matrix:
P h is an ideal photoacoustic signal matrix of dimension N × M:
P sc is a reflection clutter signal matrix of dimension N × M:
in the formula (I), the compound is shown in the specification,
and
respectively, the position r in the imaging plane n Wave number of
N =1,2, a.., N, M =1,2, a.., M, N is the number of measurement positions in the imaging plane, and M is the length of the acoustic pressure time series acquired by the detector at each measurement position.
According to Born's approximation, the reflection clutter is expressed as planar ultrasound and ideal photoacoustic signals:
where N =1,2,.., N, β are dimensional factors, vectors
Is a matrix P sc N-th row of (1), vector
Is a matrix P h N th row of (1), P us (r n ,σ l ) Is position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix. P is us (r n ,σ l ) Comprises the following steps:
wherein N =1,2,.., N, M =1,2,.., M,
is the position r in the imaging plane n At an incident angle of sigma l E is [0 degree, 360 degree ], wave number is
The sound pressure of the plane ultrasonic wave of (2).
Respectively taking the matrix P pa 、P h 、P sc Line n of (1), in conjunction with formula P pa ＝P h +P sc Obtaining:
wherein N =1,2
Is a matrix P pa Row n.
Finally according to the formula
Determining the ideal photoacoustic signal.
And S104, determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane according to the ideal photoacoustic signal.
S104 specifically comprises the following steps:
and carrying out normalization and graying processing on the ideal photoacoustic signal, and determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
Fig. 4 is a schematic structural diagram of a system for reconstructing a biological endoscopic photoacoustic image by compensating for acoustic reflection according to the present invention, and as shown in fig. 4, the system for reconstructing a biological endoscopic photoacoustic image by compensating for acoustic reflection according to the present invention comprises: a plane ultrasonic wave determination module 401, an original optical signal acquisition module 402, an ideal photoacoustic signal determination module 403, and an initial sound pressure distribution image determination module 404.
The planar ultrasound determination module 401 is configured to acquire planar ultrasound generated by an imaging plane in a simulated tissue by using a numerical simulation method.
The original light signal acquisition module 402 is configured to acquire an original light signal in an imaging plane in the imaging catheter using the ultrasound probe; an imaging plane in the imaging catheter is perpendicular to the imaging catheter; the ultrasound probe is located at the tip of the imaging catheter.
An ideal photoacoustic signal determining module 403 is used for determining an ideal photoacoustic signal by using the planar ultrasonic wave and the original optical signal; the ideal photoacoustic signal is a photoacoustic signal that does not include clutter.
The initial sound pressure distribution image determining module 404 is configured to determine, according to the ideal photoacoustic signal, an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
The plane ultrasonic determination module 401 specifically includes: the ultrasonic imaging device comprises a plane rectangular coordinate system construction unit and a plane ultrasonic determination unit.
The plane rectangular coordinate system constructing unit is used for establishing an X-Y plane rectangular coordinate system on the imaging plane by taking the center of the imaging guide pipe as a coordinate origin, taking the horizontal rightward direction as the positive direction of an X axis and taking the direction perpendicular to the X axis as the positive direction of a Y axis.
The plane ultrasonic wave determining unit is used for utilizing the formula
The planar ultrasound is determined.
Wherein the content of the first and second substances,
to point to an amplitude of k t X has a component of k x The unit vector of the wave vector of (a),
e σ as a unit vector of the directed planar ultrasonic wave, e σ ＝(cosσ,sinσ) T R = (x, y) is a point in the imaging plane; omega belongs to R 2 Is a two-dimensional imaging region; sigma belongs to [0 DEG, 360 DEG ] is the incident angle of the single plane ultrasonic wave relative to the positive direction of the X axis; p is a radical of us (r,k t σ) is the incident angle σ and the wave number k t The sound pressure of the planar ultrasonic wave at the position r; k is a radical of t = ω/c is the wave number of the plane ultrasonic wave; c is the propagation velocity of the ultrasound in the tissue; ω is the frequency of the ultrasonic wave; k is a radical of x Is the spatial wave number of the ultrasonic wave in the positive direction of the X axis, and k x |＜k t ；γ ρ (r) and γ κ (r) an acoustic heterogeneity parameter, γ, related to density and compressibility, respectively κ (r)＝κ(r)/κ 0 (r)-1，γ ρ (r)＝1-ρ 0 (r)/ρ(r)，ρ 0 (r) and κ 0 (r) is the density and compressibility, respectively, of the homogeneous medium at location r, and ρ (r) and κ (r) are the density and compressibility, respectively, of the heterogeneous medium at location r.
The ideal photoacoustic signal determining module 403 specifically includes: an ideal photoacoustic signal determining unit.
The ideal photoacoustic signal determining unit is for utilizing the formula
The ideal photoacoustic signal is determined.
Wherein, P us (r n ,σ l ) Is a position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix,
original photoacoustic signal matrix P of NxM dimensions pa E is the identity matrix and β is the dimensional factor.
The initial sound pressure distribution image determining module 404 specifically includes: an initial sound pressure distribution image determining unit.
And the initial sound pressure distribution image determining unit is used for carrying out normalization and graying processing on the ideal photoacoustic signal and determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (4)
1. A method of biological endoscopic photoacoustic image reconstruction with compensation for acoustic reflections, comprising:
acquiring plane ultrasonic waves generated by an imaging plane in a simulated tissue by adopting a numerical simulation method;
acquiring an original optical signal in an imaging plane in the imaging catheter by using an ultrasonic detector; an imaging plane in the imaging catheter is perpendicular to the imaging catheter; the ultrasonic detector is positioned at the top end of the imaging catheter;
determining an ideal photoacoustic signal using the planar ultrasonic wave and the original optical signal; the ideal photoacoustic signal is a photoacoustic signal that does not include clutter;
determining an initial sound pressure distribution image after suppressing reflection artifacts on the imaging plane according to the ideal photoacoustic signal;
the method for acquiring the plane ultrasonic wave generated by the imaging plane in the simulated tissue by adopting the numerical simulation method specifically comprises the following steps:
establishing an X-Y plane rectangular coordinate system on the imaging plane by taking the center of the imaging guide pipe as a coordinate origin, taking the horizontal rightward direction as the positive direction of an X axis and taking the direction vertical to the X axis as the positive direction of a Y axis;
using a formula
Determining the plane ultrasonic wave;
wherein the content of the first and second substances,
is a unit vector of a wave vector, the pointing amplitude of the wave vector is the same as the wave number of the plane ultrasonic wave, the X component of the wave vector is the same as the space wave number of the ultrasonic wave in the positive direction of the X axis,
e σ is a unit vector pointing to the planar ultrasonic wave,
e σ ＝(cosσ,sinσ) T r = (x, y) is a point in the imaging plane; omega belongs to R 2 Is a two-dimensional imaging region; sigma belongs to [0 DEG, 360 DEG ] is the incident angle of the single plane ultrasonic wave relative to the positive direction of the X axis; p is a radical of us (r,k t σ) is the incident angle σ and the wave number k t The sound pressure of the planar ultrasonic wave at the position r; k is a radical of formula t = ω/c is the wave number of the plane ultrasonic wave; c is the propagation velocity of the ultrasound in the tissueDegree; ω is the frequency of the ultrasonic wave; k is a radical of formula x Is the spatial wave number of the ultrasonic wave in the positive direction of the X axis, and k x |＜k t ；γ ρ (r) and gamma κ (r) an acoustic heterogeneity parameter, γ, related to density and compressibility, respectively κ (r)＝κ(r)/κ 0 (r)-1，γ ρ (r)＝1-ρ 0 (r)/ρ (r), ρ 0 (r) and κ 0 (r) being the density and compressibility, respectively, of the homogeneous medium at location r, and ρ (r) and κ (r) being the density and compressibility, respectively, of the heterogeneous medium at location r;
the determining an ideal photoacoustic signal by using the planar ultrasonic wave and the original optical signal specifically includes:
using a formula
Determining the ideal photoacoustic signal;
wherein, P us (r n ,σ l ) Is a position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix,
original photoacoustic signal matrix P of NxM dimensions pa E is the identity matrix and β is the dimensional factor.
2. The method according to claim 1, wherein the determining an initial sound pressure distribution image after suppressing reflection artifacts on the imaging plane according to the ideal photoacoustic signal comprises:
and carrying out normalization and graying processing on the ideal photoacoustic signal, and determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
3. A system for biological endoscopic photoacoustic image reconstruction with compensation for acoustic reflections, comprising:
the plane ultrasonic wave determining module is used for acquiring plane ultrasonic waves generated by an imaging plane in a simulated tissue by adopting a numerical simulation method;
the original optical signal acquisition module is used for acquiring an original optical signal in an imaging plane in the imaging catheter by using the ultrasonic detector; an imaging plane in the imaging catheter is perpendicular to the imaging catheter; the ultrasonic detector is positioned at the top end of the imaging catheter;
an ideal photoacoustic signal determining module for determining an ideal photoacoustic signal using the planar ultrasonic wave and the original optical signal; the ideal photoacoustic signal is a photoacoustic signal that does not include clutter;
an initial sound pressure distribution image determining module, configured to determine, according to the ideal photoacoustic signal, an initial sound pressure distribution image after reflection artifact suppression on the imaging plane;
the plane ultrasonic wave determination module specifically comprises:
the plane rectangular coordinate system building unit is used for building an X-Y plane rectangular coordinate system on the imaging plane by taking the center of the imaging guide pipe as a coordinate origin, taking the horizontal rightward direction as the positive direction of an X axis and taking the direction vertical to the X axis as the positive direction of a Y axis;
a plane ultrasonic wave determining unit for using the formula
Determining the plane ultrasonic wave;
wherein the content of the first and second substances,
is a unit vector of a wave vector, the pointing amplitude of the wave vector is the same as the wave number of the plane ultrasonic wave, the X component of the wave vector is the same as the space wave number of the ultrasonic wave along the positive direction of the X axis,
e σ as a unit vector of the directed planar ultrasonic wave, e σ ＝(cosσ,sinσ) T R = (x, y) is a point in the imaging plane; omega belongs to R 2 Is a two-dimensional imaging region; σ e [0 °,360 °) is the incident angle of a single plane ultrasonic wave with respect to the positive direction of the X-axisDegree; p is a radical of formula us (r,k t σ) is the incident angle σ and the wave number k t The sound pressure of the planar ultrasonic wave at the position r; k is a radical of t = ω/c is the wave number of the plane ultrasonic wave; c is the propagation velocity of the ultrasound in the tissue; ω is the frequency of the ultrasonic wave; k is a radical of x Is the spatial wave number of the ultrasonic wave in the positive direction of the X-axis, and | k x |＜k t ；γ ρ (r) and γ κ (r) an acoustic heterogeneity parameter, γ, related to density and compressibility, respectively κ (r)＝κ(r)/κ 0 (r)-1，γ ρ (r)＝1-ρ 0 (r)/ρ(r)，ρ 0 (r) and κ 0 (r) is the density and compressibility, respectively, of the homogeneous medium at location r, and ρ (r) and κ (r) are the density and compressibility, respectively, of the heterogeneous medium at location r;
the ideal photoacoustic signal determination module specifically includes:
an ideal photoacoustic signal determining unit for utilizing the formula
Determining the ideal photoacoustic signal;
wherein, P us (r n ,σ l ) Is a position r n At an incident angle of sigma l The planar ultrasonic signals at different time instants form an M x M dimensional diagonal matrix,
original photoacoustic signal matrix P of NxM dimensions pa E is the identity matrix and β is the dimensional factor.
4. The system for biological endoscopic photoacoustic image reconstruction with acoustic reflection compensation according to claim 3, wherein the initial sound pressure distribution image determining module specifically comprises:
and the initial sound pressure distribution image determining unit is used for carrying out normalization and graying processing on the ideal photoacoustic signal and determining an initial sound pressure distribution image after reflection artifact suppression on the imaging plane.
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