Breast cross-sectional image reconstruction method and device, DBT system and readable storage medium

Abstract

The invention discloses a breast cross-sectional image reconstruction method and device, a DBT system and a readable storage medium, and relates to the technical field of image processing. According to the method, fitting relations between projection angles of a DBT system and parameter values of various geometric parameters can be obtained, and a projection transformation matrix between a projection coordinate system and a space coordinate system under a target projection angle can be determined based on the target projection angle of a breast projection image and the fitting relations; and transforming the mammary gland projection image based on the projection transformation matrix so as to reconstruct a mammary gland cross-sectional image in a space coordinate system. Since each fitting relationship is obtained based on the multi-frame projection data obtained by exposing the test die body by the DBT system, that is, each fitting relationship can represent the actual parameter value of the geometric parameter of the DBT system, the reconstruction of the breast cross-sectional image is carried out based on each fitting relationship; it can be ensured that the quality of the mammary gland cross-sectional image obtained through reconstruction is high.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and in particular to a method and device for reconstructing breast tomographic images, a DBT system, and a readable storage medium. Background Art

[0002] The digital breast tomosynthesis (DBT) system can collect a series of low-dose breast projection images within a limited angle range, and reconstruct breast tomographic images based on a series of breast projection images to assist doctors in diagnosis.

[0003] The quality of breast tomographic images reconstructed by DBT system is highly dependent on the geometric parameters of DBT system. However, due to the influence of the assembly accuracy of DBT system, there is an error between the actual parameter value of DBT system geometric parameters and the theoretical parameter value. Therefore, the reconstruction of breast tomographic images based on the theoretical parameter value will result in low quality of the reconstructed breast tomographic images. Summary of the invention

[0004] The present invention provides a method and device for reconstructing breast tomographic images, a DBT system, and a readable storage medium, which can solve the problem of low quality of breast tomographic images reconstructed in the related art. The technical solution is as follows:

[0005] In one aspect, a method for reconstructing a breast tomographic image is provided, the method comprising:

[0006] Obtaining a fitting relationship between the projection angle of the DBT system and parameter values ​​of various geometric parameters, wherein each fitting relationship is determined based on multiple frames of projection data obtained by exposing the test phantom by the DBT system;

[0007] Based on the target projection angle of the breast projection image and various fitting relationships, a projection transformation matrix between the projection coordinate system and the spatial coordinate system at the target projection angle is determined, wherein the projection transformation matrix is ​​determined based on target parameter values ​​of various geometric parameters corresponding to the target projection angle;

[0008] The breast projection image is transformed based on the projection transformation matrix to reconstruct a breast tomographic image in a spatial coordinate system.

[0009] Optionally, based on the target projection angle of the breast projection image and each fitting relationship, determining a projection transformation matrix between a projection coordinate system and a spatial coordinate system at the target projection angle includes:

[0010] Based on the target projection angle of the breast projection image, target parameter values ​​of various geometric parameters corresponding to the target projection angle are determined from various fitting relationships;

[0011] Based on the association relationship between each element in the projection transformation matrix and various geometric parameters, as well as the target parameter values ​​of the various geometric parameters, each element is obtained to obtain the projection transformation matrix.

[0012] Optionally, obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, including:

[0013] Expose the test phantom from multiple projection angles to obtain multiple frames of projection images;

[0014] For each frame of projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, the parameter values ​​of various geometric parameters under the projection angle of the projection image are determined;

[0015] For each geometric parameter, a fitting relationship between the projection angle and the parameter value of the geometric parameter is established based on the parameter value of the geometric parameter at each projection angle.

[0016] Optionally, for each frame of projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, the parameter values ​​of various geometric parameters at the projection angle of the projection image are determined, including:

[0017] For each frame of projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, determine the projection transformation matrix at the projection angle of the projection image;

[0018] Based on the association between each element in the projection transformation matrix and various geometric parameters, the parameter values ​​of various geometric parameters under the projection angle are determined.

[0019] Optionally, transforming the breast projection image based on the projection transformation matrix to reconstruct a breast tomographic image includes:

[0020] Performing filtering processing on the breast projection image to obtain a filtered breast projection image;

[0021] The filtered breast projection image is transformed based on the projection transformation matrix to reconstruct a breast tomographic image.

[0022] Optionally, filtering is performed on the breast projection image, including:

[0023] Performing Fourier transform on the breast projection image, and filtering the Fourier transform result to obtain a Fourier transform result after filtering;

[0024] Perform inverse Fourier transform on the Fourier transform result after filtering to obtain the breast projection image after filtering.

[0025] On the other hand, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the method for reconstructing breast tomographic images in the above aspect is implemented.

[0026] On the other hand, a DBT system is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method for reconstructing breast tomographic images is implemented.

[0027] In another aspect, a breast tomographic image reconstruction device is provided, the device comprising:

[0028] An acquisition module is used to obtain a fitting relationship between the projection angle of the DBT system and parameter values ​​of various geometric parameters, wherein each fitting relationship is determined based on multiple frames of projection data obtained by exposing the test phantom by the DBT system;

[0029] A determination module, for determining a projection transformation matrix between a projection coordinate system and a spatial coordinate system at a target projection angle based on a target projection angle of the breast projection image and various fitting relationships, wherein the projection transformation matrix is ​​determined based on target parameter values ​​of various geometric parameters corresponding to the target projection angle;

[0030] The reconstruction module is used to transform the breast projection image based on the projection transformation matrix to reconstruct the breast tomographic image in the spatial coordinate system.

[0031] Optionally, determine the module for:

[0032] Based on the target projection angle of the breast projection image, target parameter values ​​of various geometric parameters corresponding to the target projection angle are determined from various fitting relationships;

[0033] Based on the association relationship between each element in the projection transformation matrix and various geometric parameters, as well as the target parameter values ​​of the various geometric parameters, each element is obtained to obtain the projection transformation matrix.

[0034] The beneficial effects brought about by the technical solution provided by the present invention include at least:

[0035] The present invention provides a method and device for reconstructing a breast tomographic image, a DBT system, and a readable storage medium. The method can obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, and can determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system under the target projection angle based on the target projection angle of the breast projection image and each fitting relationship, and then transform the breast projection image based on the projection transformation matrix to reconstruct the breast tomographic image under the spatial coordinate system. Since each fitting relationship is obtained based on multiple frames of projection data obtained by exposing a test phantom by the DBT system, that is, each fitting relationship can characterize the actual parameter values ​​of the geometric parameters of the DBT system, the reconstruction of the breast tomographic image based on the each fitting relationship can ensure that the quality of the reconstructed breast tomographic image is high.

[0036] Furthermore, since the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters can be obtained, the fitting relationship can comprehensively and continuously reflect the changes of the parameter value with the projection angle. Therefore, the DBT system can quickly obtain the corresponding projection transformation matrix for any target projection angle, and then can realize rapid reconstruction of breast tomographic images according to the projection transformation matrix, thereby enhancing the applicability and flexibility of the DBT system.

[0037] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a flow chart of a breast tomographic image reconstruction method provided by an embodiment of the present invention;

[0039] Figure 2 is a flow chart of another breast tomographic image reconstruction method provided by an embodiment of the present invention;

[0040] Figure 3 is θ under multiple projection angles provided by the embodiment of the present invention x Schematic diagram of parameter values;

[0041] Figure 4 is θ under multiple projection angles provided by the embodiment of the present invention y Schematic diagram of parameter values;

[0042] Figure 5 is t at multiple projection angles provided by the embodiment of the present invention x Schematic diagram of parameter values;

[0043] Figure 6 is t at multiple projection angles provided by the embodiment of the present invention y Schematic diagram of parameter values;

[0044] Figure 7 is v under multiple projection angles provided by the embodiment of the present invention 0 Schematic diagram of parameter values;

[0045] Figure 8 is θ under multiple projection angles provided by the embodiment of the present invention z Schematic diagram of parameter values;

[0046] Fig. 9 is t at multiple projection angles provided by the embodiment of the present invention z Schematic diagram of parameter values;

[0047] Fig.10 The embodiment of the present invention provides multiple projection angles. Schematic diagram of parameter values;

[0048] Fig.11 The embodiment of the present invention provides multiple projection angles. Schematic diagram of parameter values;

[0049] Fig.12 The embodiment of the present invention provides multiple projection angles. Schematic diagram of parameter values;

[0050] Fig.13 The embodiment of the present invention provides t x with u 0 A schematic diagram of the relationship between

[0051] Fig.14 is a schematic diagram of a projection image provided by an embodiment of the present invention;

[0052] Fig.15 is a schematic diagram of a test phantom provided by an embodiment of the present invention;

[0053] Fig.16 A breast tomographic image reconstructed based on the parameter values ​​of a theory of geometric parameters;

[0054] Fig.17 A breast tomographic image reconstructed by the method provided by the embodiment of the present invention;

[0055] Fig.18 is a schematic structural diagram of a DBT system provided by an embodiment of the present invention;

[0056] Fig.19 The present invention is a block diagram of a breast tomographic image reconstruction device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0057] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0058] Figure 1 1 is a flow chart of a breast tomographic image reconstruction method provided by an embodiment of the present invention, and the method is applied to a DBT system. Figure 1 , the method comprising:

[0059] Step 101: Obtain a fitting relationship between the projection angle of a DBT system and parameter values ​​of various geometric parameters of the DBT system.

[0060] In an embodiment of the present invention, the computing device can obtain multiple frames of projection data of the test phantom at different projection angles, and determine the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters based on the multiple frames of projection data, and then send the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters to the DBT system. Thus, the DBT system can obtain various fitting relationships.

[0061] Alternatively, the DBT system can expose the test phantom from multiple projection angles to obtain multiple frames of projection images. Afterwards, the DBT system can determine the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters based on the position of the marker in the test phantom in the projection image and the spatial position of the marker. The DBT system includes a ray source and a flat panel detector. The projection angle refers to: the position and direction of the ray source relative to the flat panel detector.

[0062] Step 102: Based on the target projection angle of the breast projection image and the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters, determine the projection transformation matrix between the projection coordinate system and the space coordinate system at the target projection angle.

[0063] After scanning the breast of the scanned object, the DBT system can obtain multiple frames of breast projection images, and the target projection angles of any two frames of breast projection images in the multiple frames are different. For each frame of breast projection image, the DBT system can determine the target parameter values ​​of various geometric parameters corresponding to the target projection angle of the breast projection image based on the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters, and then determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system under the target projection angle according to each target parameter value. Among them, the projection coordinate system is the two-dimensional coordinate system where the breast projection image is located. The spatial coordinate system is the three-dimensional coordinate system where the reconstructed breast tomographic image is located.

[0064] Step 103: transform the breast projection image based on the projection transformation matrix to reconstruct a breast tomographic image in a spatial coordinate system.

[0065] For each breast projection image in the multiple frames of breast projection images, the DBT system can perform image transformation on the breast projection image based on the projection transformation matrix corresponding to the target projection angle, so as to map each pixel of the breast projection image to the spatial coordinate system where the tomographic image is located, thereby obtaining a breast tomographic image.

[0066] In summary, an embodiment of the present invention provides a method for reconstructing a breast tomographic image, which can obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, and can determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system at the target projection angle based on the target projection angle of the breast projection image and each fitting relationship, and then transform the breast projection image based on the projection transformation matrix to reconstruct the breast tomographic image in the spatial coordinate system. Since each fitting relationship is obtained based on multiple frames of projection data obtained by exposing a test phantom by the DBT system, that is, each fitting relationship can characterize the actual parameter values ​​of the geometric parameters of the DBT system, the reconstruction of the breast tomographic image based on the each fitting relationship can ensure that the quality of the reconstructed breast tomographic image is high.

[0067] Furthermore, since the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters can be obtained, the fitting relationship can comprehensively and continuously reflect the changes of the parameter value with the projection angle. Therefore, the DBT system can quickly obtain the corresponding projection transformation matrix for any target projection angle, and then can realize rapid reconstruction of breast tomographic images according to the projection transformation matrix, thereby enhancing the applicability and flexibility of the DBT system.

[0068] The embodiment of the present invention takes the DBT system, based on the multi-frame projection data obtained by exposing the test phantom, to obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters as an example, and exemplarily describes the reconstruction method of the breast tomographic image provided by the embodiment of the present invention. The method can be applied to the DBT system, such as the controller of the DBT system. Figure 2 , the method may include:

[0069] Step 201 : Expose the test phantom from multiple projection angles to obtain multiple frames of projection images of the test phantom.

[0070] In an embodiment of the present invention, before exposing the test phantom, the staff can place the test phantom at a preset position of the detector and fix it by a bracket. Afterwards, the controller can control the detector to be fixed, and control the ray source to rotate around the test phantom in a stepwise or continuous manner within an angle range to perform multi-angle exposure, so as to obtain projection images at multiple different projection angles. The controller can store the angle range in advance.

[0071] The test phantom may include a substrate and a plurality of markers disposed in the substrate. The absorption coefficient of the material making the markers is different from the absorption coefficient of the material making the substrate, thereby ensuring that the markers can be detected from the projection image.

[0072] Optionally, the substrate may be a rectangular parallelepiped made of polymethyl methacrylate (PMMA) material. The multiple markers may be multiple steel balls of the same size.

[0073] Step 202: for each frame of projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, determine the parameter values ​​of various geometric parameters at the projection angle of the projection image.

[0074] The position of the marker in the projection image may be: the projection coordinates of the marker in the projection coordinate system. The projection coordinate system may be a two-dimensional coordinate system established with the center point of the flat panel detector as the origin, the pixel row direction of the flat panel detector as the positive direction of the V axis, and the pixel column direction of the flat panel detector as the positive direction of the U axis.

[0075] The spatial position of the marker may be pre-stored in the controller. The spatial position of the marker may be: the coordinates of the feature point of the marker in the spatial coordinate system. The origin O of the spatial coordinate system may be a point in space (such as a vertex of the test phantom). The X-axis of the spatial coordinate system is parallel to the V-axis of the image coordinate system, the Y-axis of the spatial coordinate system is parallel to the U-axis of the image coordinate system, and the Z-axis of the spatial coordinate system may be perpendicular to the XOY plane.

[0076] Optionally, the position of the marker in the projection image may be the position of a feature point of the marker in the projection image. The feature point may be a center point.

[0077] In the embodiment of the present invention, the process of the controller executing step 202 may include:

[0078] Step B1, obtaining the position of the marker in the test phantom in the projection image.

[0079] For each frame of projection image, the controller can determine the region of interest (ROI) of the feature point of each marker in the projection image based on the projection angle corresponding to the projection image and the size of the test phantom, etc. In this way, it is possible to avoid interference in the extraction of feature points by areas other than the marker, thereby improving the accuracy and efficiency of determining the position of the marker.

[0080] Then, the controller can preprocess the region of interest and use an edge detection algorithm to extract the projection edge of the marker in the projection image. Afterwards, the controller can fit the projection edge and determine the center coordinates of the area surrounded by the fitted edge as the projection position of the marker. Optionally, the edge detection algorithm can be a canny operator, a prewitt operator, or a sobel operator in the gradient operator. In the case where the marker is a steel ball, the marker is elliptical in the projection image due to the influence of the projection angle and cone beam imaging, so the projection edge of the extracted marker can be elliptical fitted.

[0081] Since the controller can preprocess the region of interest, the noise in the region of interest can be reduced so that the controller can better detect the marker from the projection image based on the region of interest. Optionally, the preprocessing can include: image smoothing processing, morphological processing and binarization processing, etc.

[0082] Step B2: Based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system at the projection angle of the projection image.

[0083] In an embodiment of the present invention, the controller can solve the projection transformation matrix at the projection angle according to the position of the marker in the projection image and the spatial position of the marker. Specifically, the controller can obtain an equation that characterizes the transformation relationship between the projection coordinate system and the spatial coordinate system, and the equation includes the projection transformation matrix to be solved. Then, the controller can bring the position of the marker in the projection image and the spatial position of the marker into the equation for solving, thereby obtaining the projection transformation matrix at the projection angle of the projection image. Among them, the projection transformation matrix at each projection angle is used to characterize the transformation relationship between the position of the marker in the projection image and the spatial position of the marker at the projection angle.

[0084] Generally, the relationship between the spatial position of the marker and the position of the marker in the projection image can satisfy:

[0085]

[0086] In formula (1), (ui , v i ) is the position of the i-th marker in the projection image, and i is an integer greater than or equal to 1. (x i ,y i , z i ) is the spatial position of the i-th marker, w i is the distance weight from the ray source to the detector. P is the projection transformation matrix. The size of the projection transformation matrix P is 3 rows and 4 columns, and it satisfies:

[0087] Expanding formula (1) into an equation form yields:

[0088]

[0089] Eliminate the distance weight w from the ray source to the detector in formula (3): i After that, the following formula (3) can be obtained:

[0090] P 11 x i +P 12 y i +P 13 z i +P 14 -u i (P 31 x i +P 32 y i +P 33 z i +P 34 )=0

[0091] P 21 x i +P 22 y i +P 23 z i +P 24 -v i (P 31 x i +P 32 y i +P 33 z i +P 34 )=0

[0092] Formula (3)

[0093] By formatting the two equations in formula (3) into a matrix form, we can obtain an equation consisting of the position of the marker in the projection image, the spatial position, and the projection transformation matrix to be solved, which satisfies:

[0094] Ai p=0 Formula (4)

[0095] In formula (4), A i is a matrix with 2 rows and 12 columns, and A i satisfy: p is a column vector containing all elements of the projection matrix P, and p satisfies: p = (P 11 , P 12 , P 13 , P 14 , P 21 , P 22 , P 23 , P 24 , P 31 , P 32 , P 33 , P 34 ) T .

[0096] Step B3: based on the association between each element in the projection transformation matrix and various geometric parameters, determine the parameter values ​​of various geometric parameters under the projection angle.

[0097] The geometric parameters include the following parameters: θ x ,θ y ,θ z , v 0 ,t x ,t y ,t z and u 0 The relationship between each element in the projection transformation matrix and various geometric parameters can be obtained in advance. x ,θ y ,θ z are the angles between the flat panel detector and the X-axis, Y-axis, and Z-axis of the world coordinate system. u 、p v are the width and height of the pixels of the flat panel detector respectively. α is the distortion correction parameter for non-rectangular pixels in the detector. 0 、v 0 is the offset of the central line beam of the ray source relative to the central coordinate of the flat panel detector, that is, the coordinate of the central line beam. x ,t y ,t z are the offsets of the flat panel detector relative to the X-axis, Y-axis, and Z-axis of the world coordinate system. f is the distance from the ray source to the detector.

[0098] In the embodiment of the present invention, the association relationship between each element and various geometric parameters can be obtained through the following process:

[0099] In general, the projection transformation matrix P can also satisfy:

[0100] P=K[R|t] Formula (5)

[0101] Among them, in formula (5), K is the internal parameter matrix of the DBT system, R is the rotation matrix representing the rotation transformation from the spatial coordinate system to the projection coordinate system, and t is the offset vector representing the translation transformation from the spatial coordinate system to the projection coordinate system.

[0102] The internal parameter matrix K can satisfy:

[0103]

[0104] In formula (6), (u 0 , v 0 ) are the centerline coordinates.

[0105] Since any rotation operation can always be decomposed into the product of the rotation components in the three directions of the XYZ axis of the spatial coordinate system, the rotation matrix R can satisfy: R = Rx × Ry × Rz. Among them, Rx can satisfy: Ry can satisfy: Rz can satisfy:

[0106]

[0107] That is, the rotation matrix R can satisfy:

[0108]

[0109] According to formula (7), we can get:

[0110]

[0111] In an embodiment of the present invention, the K and R matrices can be obtained by performing RQ decomposition on the upper left 3 rows and 3 columns submatrix of the projection transformation matrix P, so that the geometric parameters in the matrix k and the geometric parameters in the matrix R and the relationship between the elements in the projection transformation matrix P can be obtained.

[0112] The offset vector t can be expressed as the superposition of the translation effects in the three directions of the XYZ axis of the spatial coordinate system, so the offset vector t can satisfy:

[0113]

[0114] Among them, tz, ty and tx satisfy:

[0115] t z =P 34 Formula (12)

[0116] t y =(P 24 -K 23 P 34 ) / K 22 Formula (13)

[0117] t x =(P 14 -t y P 12 -K 13 P 34 ) / K 11 Formula (14)

[0118] Through the above formulas (12) to (14), the correlation between each geometric parameter in the offset vector t and each element of the projection transformation matrix can be obtained.

[0119] Step 203: For each geometric parameter, based on the parameter value of the geometric parameter at each projection angle, a fitting relationship between the projection angle and the parameter value of the geometric parameter is established.

[0120] For each geometric parameter, the controller can determine a suitable fitting model according to the changing trend of the parameter value of the geometric parameter with the projection angle, and fit the numerical value of the geometric parameter at each projection angle according to the fitting model, so as to obtain the fitting relationship between the projection angle and the parameter value of the geometric parameter. For example, if the changing trend is a linear change, a linear regression model can be used as the fitting model for fitting. If the changing trend is a nonlinear change, a nonlinear regression model (such as a polynomial regression model) can be used as the fitting model for fitting. Using a suitable fitting model for fitting can make the fitting error within an acceptable range.

[0121] In the embodiment of the present invention, for the geometric parameter θ x ,θ y ,t x ,t y 、v 0 ,θ z ,t z , The controller can directly fit the parameter values ​​at each projection angle according to the fitting model to obtain the fitting relationship between the projection angle and the parameter value of the geometric parameter.

[0122] For the projection angle and u 0 The controller can directly adjust u at each projection angle according to the fitting model. 0 The parameter values ​​are fitted to obtain the projection angle and u 0Alternatively, the controller can first obtain the projection angle and t x The fitting relationship of x with u 0 The relationship between the projection angle and t x The fitting relationship of x with u 0 The correlation between the projection angle and u 0 The fitting relationship.

[0123] For example, the controller exposes the test phantom within the angle range of ±25° to obtain 25 projection images at different projection angles. The parameter values ​​of the geometric parameters at each projection angle obtained by the controller based on the 25 projection images can be as follows: Figures 3 to 12 As shown. x The corresponding u 0 The parameter values ​​are as follows Fig.13 shown.

[0124] See also Figures 3 to 7 It can be seen that the geometric parameter θ x ,θ y ,t x ,t y and v 0 The parameter values ​​of are linearly related to the projection angle. Figures 8 to 12 It can be seen that the geometric parameter θ z ,t z , The parameter values ​​of are nonlinearly related to the projection angle.

[0125] It can be seen that the controller can use a linear regression model to calculate θ at each projection angle. x ,θ y ,t x ,t y and v 0 The parameter values ​​of t are fitted, and the linear regression model is used to x u 0 In addition, the controller can use a nonlinear regression model to fit θ at each projection angle. z ,t z , The parameter values ​​are fitted to establish the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters.

[0126] Step 204: Acquire a breast projection image obtained by exposing the breast of the scanned object.

[0127] The DBT system can control the radiation source to rotate around the breast of the scanned object within an angle range to perform multi-angle exposure, thereby obtaining multi-frame breast projection images of the breast at multiple projection angles.

[0128] Step 205: Based on the target projection angle of the breast projection image, target parameter values ​​of various geometric parameters corresponding to the target projection angle are determined from various fitting relationships.

[0129] For the fitting relationship between the projection angle and the parameter value of each geometric parameter, the controller may determine the parameter value corresponding to the target projection angle in the fitting relationship as the target parameter value of the geometric parameter. The target projection angle may be acquired in advance.

[0130] Step 206: Based on the association between each element in the projection transformation matrix and various geometric parameters, as well as the target parameter values ​​of the various geometric parameters, each element in the projection transformation matrix is ​​obtained to obtain the projection transformation matrix.

[0131] For each element in the projection transformation matrix, the controller can bring the target parameter values ​​of various geometric parameters into the association relationship to obtain the element, thereby obtaining the projection transformation matrix. That is, the projection transformation matrix is ​​determined based on the target parameter values ​​of various geometric parameters corresponding to the target projection angle.

[0132] Step 207: filter the breast projection image to obtain a filtered breast projection image.

[0133] For each breast projection image in the multiple frames of breast projection images, the controller may perform filtering processing on the breast projection image to obtain a filtered breast projection image.

[0134] Since the controller can filter each frame of the breast projection image, it can suppress the low-frequency components in the breast projection image and enhance the high-frequency components, thereby improving the clarity and contrast of the breast projection image, and then ensuring that the quality of the reconstructed breast tomographic image is good.

[0135] In the embodiment of the present invention, the controller can directly use a filtering algorithm to filter each frame of breast projection image to obtain a filtered breast projection image. Optionally, the filtering algorithm can be a Gaussian filtering algorithm or a bilateral filtering algorithm.

[0136] Alternatively, the controller may perform Fourier transform on each frame of breast projection image, and filter the Fourier transform result to obtain a Fourier transform result after filtering. Then, the controller may perform inverse Fourier transform on the Fourier transform result after filtering to obtain a breast projection image after filtering.

[0137] Step 208: transform the filtered breast projection image based on the projection transformation matrix to reconstruct a breast tomographic image.

[0138] For each breast projection image in the multiple frames of breast projection images, the DBT system can perform image transformation on the breast projection image based on the projection transformation matrix corresponding to the target projection angle of the breast projection image, so as to map each pixel of the breast projection image to the spatial coordinate system where the reconstructed image is located, thereby obtaining a breast tomographic image.

[0139] Understandably, reference Fig.15 The inner walls of the first plate surface 01 and the second plate surface 02 of the base of the test phantom provided by the embodiment of the present invention can be provided with a plurality of slots. The slots on the first plate surface 01 correspond to the slots on the second plate surface 02 one by one and are parallel to each other. Each pair of slots can be embedded with a layer of a board with a plurality of markers. The number of markers on the plurality of layers can be different, and the orthographic projections on the target plane do not overlap. The target plane can be perpendicular to Fig.15 The test phantom is shown in height orientation.

[0140] When exposing the test phantom, the placement of each layer along the height direction of the test phantom can be flexibly adjusted. In this way, on the one hand, it is possible to avoid the markers on different layers from appearing in the projection image during the exposure process. Fig.14 The overlap shown in the included area 131 can avoid the inaccurate position of the marker determined based on the projection image; on the other hand, a larger imaging area can be covered to better cover the reconstruction space.

[0141] Fig.16 is a breast tomographic image reconstructed based on the parameter values ​​of a theory of geometric parameters. Fig.17 This is a breast tomographic image reconstructed using the method provided by the embodiment of the present invention. Fig.16 and Fig.17 It can be seen that in the breast tomographic image reconstructed by the method provided by the embodiment of the present invention, the tiny calcification points are clearer and the edges of the calcification points are sharper.

[0142] It is understandable that the order of the steps of the breast tomographic image reconstruction method provided by the embodiment of the present invention can be appropriately adjusted, and the steps can also be increased or decreased accordingly according to the situation. For example, step 201 to step 202 can be deleted according to the situation. Any technician familiar with the technical field can easily think of a method of change within the technical scope disclosed in this application, which should be included in the protection scope of this application, so it will not be repeated.

[0143] In summary, an embodiment of the present invention provides a method for reconstructing a breast tomographic image, which can obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, and can determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system at the target projection angle based on the target projection angle of the breast projection image and each fitting relationship, and then transform the breast projection image based on the projection transformation matrix to reconstruct the breast tomographic image in the spatial coordinate system. Since each fitting relationship is obtained based on multiple frames of projection data obtained by exposing a test phantom by the DBT system, that is, each fitting relationship can characterize the actual parameter values ​​of the geometric parameters of the DBT system, the reconstruction of the breast tomographic image based on the each fitting relationship can ensure that the quality of the reconstructed breast tomographic image is high.

[0144] Furthermore, since the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters can be obtained, the fitting relationship can comprehensively and continuously reflect the changes of the parameter value with the projection angle. Therefore, the DBT system can quickly obtain the corresponding projection transformation matrix for any target projection angle, and then can realize rapid reconstruction of breast tomographic images according to the projection transformation matrix, thereby enhancing the applicability and flexibility of the DBT system.

[0145] The embodiment of the present invention provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned breast tomographic image reconstruction method is implemented. Figure 1 or Figure 2 The reconstruction method of the breast tomographic image is shown.

[0146] Fig.18 is a schematic diagram of a DBT system structure provided by an embodiment of the present invention, such as Fig.18 As shown, the DBT system 17 may include a memory 1701, a processor 1702, and a computer program stored in the memory 1701 and executable on the processor 1702. When the processor 1702 executes the computer program, the breast tomographic image reconstruction method shown in the above embodiment is implemented. Figure 1 or Figure 2 The reconstruction method of the breast tomographic image is shown.

[0147] Fig.19 is a block diagram of a breast tomographic image reconstruction device provided by an embodiment of the present invention, which is applied to, for example Fig.19 As shown, the device 180 includes:

[0148] The acquisition module 1801 is used to obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, and each fitting relationship is determined based on multiple frames of projection data obtained by exposing the test phantom by the DBT system.

[0149] Determination module 1802 is used to determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system at the target projection angle based on the target projection angle of the breast projection image and various fitting relationships. The projection transformation matrix is ​​determined based on the target parameter values ​​of various geometric parameters corresponding to the target projection angle.

[0150] The reconstruction module 1803 is used to transform the breast projection image based on the projection transformation matrix to reconstruct the breast tomographic image in the spatial coordinate system.

[0151] Optionally, the determination module 1802 may be used to:

[0152] Based on the target projection angle of the breast projection image, target parameter values ​​of various geometric parameters corresponding to the target projection angle are determined from various fitting relationships;

[0153] Based on the association relationship between each element in the projection transformation matrix and various geometric parameters, as well as the target parameter values ​​of the various geometric parameters, each element is obtained to obtain the projection transformation matrix.

[0154] Optionally, the acquisition module 1801 may be used to:

[0155] Expose the test phantom from multiple projection angles to obtain multiple frames of projection images;

[0156] For each frame of projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, the parameter values ​​of various geometric parameters under the projection angle of the projection image are determined;

[0157] For each geometric parameter, a fitting relationship between the projection angle and the parameter value of the geometric parameter is established based on the parameter value of the geometric parameter at each projection angle.

[0158] Optionally, the acquisition module 1801 may be used to:

[0159] For each frame of projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, determine the projection transformation matrix at the projection angle of the projection image;

[0160] Based on the association between each element in the projection transformation matrix and various geometric parameters, the parameter values ​​of various geometric parameters under the projection angle are determined.

[0161] Optionally, the reconstruction module 1803 may be used to:

[0162] Performing filtering processing on the breast projection image to obtain a filtered breast projection image;

[0163] The filtered breast projection image is transformed based on the projection transformation matrix to reconstruct a breast tomographic image.

[0164] Optionally, the reconstruction module 1803 may be used to:

[0165] Performing Fourier transform on the breast projection image, and filtering the Fourier transform result to obtain a Fourier transform result after filtering;

[0166] Perform inverse Fourier transform on the Fourier transform result after filtering to obtain the breast projection image after filtering.

[0167] In summary, an embodiment of the present invention provides a device for reconstructing a breast tomographic image, which can obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, and can determine the projection transformation matrix between the projection coordinate system and the spatial coordinate system at the target projection angle based on the target projection angle of the breast projection image and each fitting relationship, and then transform the breast projection image based on the projection transformation matrix to reconstruct the breast tomographic image in the spatial coordinate system. Since each fitting relationship is obtained based on multiple frames of projection data obtained by exposing a test phantom by the DBT system, that is, each fitting relationship can characterize the actual parameter values ​​of the geometric parameters of the DBT system, the reconstruction of the breast tomographic image based on the each fitting relationship can ensure that the quality of the reconstructed breast tomographic image is high.

[0168] Furthermore, since the fitting relationship between the projection angle and the parameter values ​​of various geometric parameters can be obtained, the fitting relationship can comprehensively and continuously reflect the changes of the parameter value with the projection angle. Therefore, the DBT system can quickly obtain the corresponding projection transformation matrix for any target projection angle, and then can realize rapid reconstruction of breast tomographic images according to the projection transformation matrix, thereby enhancing the applicability and flexibility of the DBT system.

[0169] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0170] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0171] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0172] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0173] In addition, the terms "first", "second", etc. used in the embodiments of the present invention are only used for descriptive purposes and should not be understood as indicating or implying relative importance, or implicitly indicating the number of technical features indicated in the present embodiment. Therefore, the features defined by the terms "first", "second", etc. in the embodiments of the present invention can explicitly or implicitly indicate that the embodiment includes at least one of the features. In the description of the present invention, the word "multiple" means at least two or two or more, such as two, three, four, etc., unless otherwise clearly and specifically defined in the embodiments.

[0174] In the present invention, unless otherwise clearly specified or limited in the embodiments, the terms "installed", "connected", "connected" and "fixed" etc. in the embodiments should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integrated connection. It can be understood that it can also be a mechanical connection, an electrical connection, etc.; of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements, or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific implementation situation.

[0175] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0176] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for reconstructing a breast tomographic image, characterized in that: The method comprises: Obtaining a fitting relationship between the projection angle of the DBT system and parameter values ​​of various geometric parameters, wherein each fitting relationship is determined based on multiple frames of projection data obtained by exposing the test phantom by the DBT system; Based on the target projection angle of the breast projection image and each of the fitting relationships, determining a projection transformation matrix between the projection coordinate system and the spatial coordinate system at the target projection angle, wherein the projection transformation matrix is ​​determined based on target parameter values ​​of various geometric parameters corresponding to the target projection angle; The breast projection image is transformed based on the projection transformation matrix to reconstruct a breast tomographic image in the spatial coordinate system.

2. The method according to claim 1, characterized in that: Based on the target projection angle of the breast projection image and each of the fitting relationships, a projection transformation matrix between the projection coordinate system and the space coordinate system at the target projection angle is determined, including: Based on the target projection angle of the breast projection image, determining target parameter values ​​of various geometric parameters corresponding to the target projection angle from each of the fitting relationships; Based on the association relationship between each element in the projection transformation matrix and each of the geometric parameters, as well as the target parameter values ​​of each of the geometric parameters, each of the elements is obtained to obtain the projection transformation matrix.

3. The method according to claim 1, characterized in that Obtain the fitting relationship between the projection angle of the DBT system and the parameter values ​​of various geometric parameters, including: Expose the test phantom from multiple projection angles to obtain multiple frames of projection images; For each frame of the projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, determining parameter values ​​of various geometric parameters at the projection angle of the projection image; For each of the geometric parameters, a fitting relationship between the projection angle and the parameter value of the geometric parameter is established based on the parameter value of the geometric parameter at each of the projection angles.

4. The method according to claim 3, characterized in that For each frame of the projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, the parameter values ​​of various geometric parameters at the projection angle of the projection image are determined, including: For each frame of the projection image, based on the position of the marker in the test phantom in the projection image and the spatial position of the marker, determine the projection transformation matrix at the projection angle of the projection image; Based on the association between each element in the projection transformation matrix and the various geometric parameters, the parameter values ​​of the various geometric parameters at the projection angle are determined.

5. The method according to any one of claims 1 to 4, characterized in that: The breast projection image is transformed based on the projection transformation matrix to reconstruct the breast tomographic image, comprising: Performing filtering processing on the breast projection image to obtain the breast projection image after filtering processing; The breast projection image after filtering is transformed based on the projection transformation matrix to reconstruct the breast tomographic image.

6. The method according to claim 5, characterized in that The breast projection image is subjected to filtering processing, comprising: Performing Fourier transform on the breast projection image, and filtering the Fourier transform result to obtain the Fourier transform result after filtering; Perform inverse Fourier transform on the Fourier transform result after filtering to obtain the breast projection image after filtering.

7. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor, the method for reconstructing a breast tomographic image according to any one of claims 1 to 6 is implemented.

8. A DBT system, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for reconstructing a breast tomographic image according to any one of claims 1 to 6 is implemented.

9. A breast tomographic image reconstruction device, characterized in that: The device includes: An acquisition module, used to acquire a fitting relationship between the projection angle of the DBT system and parameter values ​​of various geometric parameters, wherein each fitting relationship is determined based on multiple frames of projection data obtained by exposing a test phantom by the DBT system; A determination module, configured to determine, based on a target projection angle of the breast projection image and each of the fitting relationships, a projection transformation matrix between a projection coordinate system and a spatial coordinate system at the target projection angle, wherein the projection transformation matrix is ​​determined based on target parameter values ​​of various geometric parameters corresponding to the target projection angle; A reconstruction module is used to transform the breast projection image based on the projection transformation matrix to reconstruct a breast tomographic image in the spatial coordinate system.

10. The device according to claim 9, characterized in that Identify modules for: Based on the target projection angle of the breast projection image, determining target parameter values ​​of various geometric parameters corresponding to the target projection angle from each of the fitting relationships; Based on the association relationship between each element in the projection transformation matrix and each of the geometric parameters, as well as the target parameter values ​​of each of the geometric parameters, each of the elements is obtained to obtain the projection transformation matrix.

Images