CN117314988B - DBT reconstruction method for multi-angle projection registration - Google Patents

Abstract

The invention discloses a DBT reconstruction method for multi-angle projection registration, which includes the following steps: obtaining multi-angle projection data; preprocessing the projection data based on Beer's theorem to obtain preprocessed projection data; based on isocenter arc The motion displacement registration method performs block coordinate translation processing on the preprocessed projection data to obtain the translated projection data; performs image interpolation processing on the pixel vacancy values in the translated projection data to obtain the interpolated projection Data; based on the interpolated projection data, the DBT reconstruction layer is obtained and output based on the DBT reconstruction algorithm. By acquiring multi-angle projection data and based on the displacement registration method of isocentric arc motion, the central projection is standardized, which meets the different magnification requirements of different angle projections for the reconstruction layer, making the contrast higher and focusing on the texture of the reconstruction layer. Sharper, clearer borders and less prone to artifacts.

Description

A DBT reconstruction method for multi-angle projection registration

Technical field

The invention relates to a multi-angle projection registration DBT reconstruction method, belonging to the technical field of medical image processing.

Background technique

Breast cancer is a malignant tumor that occurs in breast epithelial tissue and seriously threatens women's life and health. Through early detection and timely diagnosis and treatment of breast cancer, 90% of patients can live longer. It can be seen that early screening for breast cancer is very important. Digital Breast Tomosynthesis (DBT) is a technology that uses a few projections within a limited angular range to perform three-dimensional breast imaging. In DBT, when the X-ray source follows a predetermined trajectory (usually 60° or less in the angular range) When moving (arc), multiple projections are obtained to reconstruct a cross-section parallel to the breast support plane. The entire data collection and scanning process takes a short time, and the limited-angle projection data collected by the scan contains all anatomical structure information of breast tissue at different angles. Compared with the currently widely used full-angle data collection method of computed tomography (CT), DBT has a small collection angle range and only collects 10 to 25 projection data within a small angle range, while CT has a large number of projections. Up to thousands. Therefore, the total radiation damage under DBT acquisition mode is much less than that of conventional CT.

However, in the current literature on DBT imaging, the displacement formula is derived using the parallel operation mode of the X-ray tube relative to the stationary detection surface. The contrast is low, the focusing effect is poor, the boundaries are blurred, and artifacts are easily produced.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a DBT reconstruction method for multi-angle projection registration. By acquiring multi-angle projection data and a displacement registration method based on isocentric arc motion, the center is realized. Projection standardization meets the different magnification requirements of the reconstruction layer for different angle projections, making the contrast higher, the texture of the focused reconstruction layer clearer, the boundary clearer, and artifacts less likely to occur.

In order to achieve the above objects, the present invention is achieved by adopting the following technical solutions:

The invention discloses a multi-angle projection registration DBT reconstruction method, which includes the following steps:

Obtain multi-angle projection data;

Preprocess the projection data based on Beer's theorem to obtain preprocessed projection data;

Based on the displacement registration method of isocentric arc motion, perform block coordinate translation processing on the preprocessed projection data to obtain the translated projection data;

Perform image interpolation processing on the pixel gap values in the translated projection data to obtain interpolated projection data;

According to the interpolated projection data and based on the DBT reconstruction algorithm, a DBT reconstruction layer is obtained and output.

Further, the acquisition of multi-angle projection data includes:

Based on the X-ray tube, the isocenter arc motion projection is performed, and the detector is used to shoot the X-ray projection at equal angle intervals to obtain multi-angle projection data.

Further, the expression of the preprocessed projection data is as follows:

;

in, Indicates the projection angle;/> Represents the preprocessed projection angle/> projection data;/> Represents the unpreprocessed projection angle/> projection data;/> Represents the logarithmic operation with constant e as the base.

Further, the displacement registration method of isocentric arc motion includes:

Get preprocessed projection data;

Based on the preset isocenter arc motion model with different reconstruction layer depths, calculate the displacement of the preprocessed projection data at different angles, and obtain the displacement of the projection data along the x-axis determined by the angle and reconstruction layer depth;

According to the displacement of the projection data along the x-axis, the preprocessed projection data is subjected to block coordinate translation processing to obtain translated projection data.

Further, the expression of the displacement of the projection data along the x-axis is as follows:

;

in, Indicates the projection angle;/> Indicates that the projection angle is/> The x-axis coordinate to be translated;/> Indicates the reconstruction layer depth;/> Indicates that when the reconstruction layer depth is/> , the projection angle is/> The displacement of the projection data along the x-axis; d represents the radius of the isocenter arc.

Further, the translated projection data is expressed as:

;

in, Represents the projection data after translation;/> Indicates that the projection angle is/> The x-axis coordinate after translation, ,/> Indicates that the projection angle is/> The x-axis coordinate to be translated;/> Indicates that the projection angle is/> The y-axis coordinate at;/> Indicates the reconstruction layer depth.

Further, the interpolated projection data is obtained, including:

Get the translated projection data;

Perform pixel gap search processing on the translated projection data to obtain pixel gap values;

According to the pixel vacancy value, a one-dimensional linear interpolation method is used to interpolate the adjacent pixels on both sides of the pixel vacancy value to obtain interpolated projection data.

Further, the expression of the one-dimensional linear interpolation method is as follows:

;

in, Represents the pixel gap value of the y-axis component in the translated projection data;/> Represents the pixel gap value Adjacent upper pixel value;/> Indicates the pixel vacant value/> The adjacent lower pixel value.

Compared with the prior art, the beneficial effects achieved by the present invention are:

By acquiring multi-angle projection data and based on the displacement registration method of isocentric arc motion, the present invention realizes the standardization of center projection, meets the different magnification requirements of different angle projections for the reconstruction layer, and improves the configuration of multi-angle projection. Accurate precision makes the contrast higher, the texture of the focused reconstruction layer clearer, the boundaries clearer, and artifacts are less likely to occur.

Description of the drawings

Figure 1 is a flow chart of a multi-angle projection registration DBT reconstruction method provided in this embodiment;

Figure 2 is a schematic diagram of the optimized X-ray tube performing isocentric arc motion mode provided in this embodiment;

Figure 3 is a schematic diagram of a parallel operation mode of an X-ray tube in the prior art;

Figure 4 shows breast image projection data collected from multiple angles;

Figure 5 shows the difference image of the focused reconstruction layer and the two focused reconstruction layers respectively obtained by using the existing technology and the method of this embodiment;

Figure 6 shows the effect of enlarging the marked points in Figure 5 by 800 times at equal proportions;

Figure 7 shows the focused reconstruction layer and the corresponding Fourier spectrum respectively obtained using the existing technology and the method of this embodiment.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present invention, but cannot be used to limit the scope of the present invention.

This embodiment provides a multi-angle projection registration DBT reconstruction method, which includes the following steps:

Obtain multi-angle projection data;

Preprocess the projection data based on Beer's theorem to obtain the preprocessed projection data;

Based on the displacement registration method of isocentric arc motion, the preprocessed projection data is processed by block coordinate translation to obtain the translated projection data;

Perform image interpolation processing on the pixel gap values in the translated projection data to obtain the interpolated projection data;

According to the interpolated projection data, based on the DBT reconstruction algorithm, the DBT reconstruction layer is obtained and output.

The technical concept of the present invention is: by acquiring multi-angle projection data and based on the displacement registration method of isocentric arc motion, the standardization of center projection is realized, which satisfies the different magnification requirements of different angle projections for the reconstruction layer, and improves the The registration accuracy of multi-angle projection makes the contrast higher, the texture of the focused reconstruction layer clearer, the boundaries clearer, and artifacts are less likely to occur.

As shown in Figure 1, the specific steps are as follows:

Step 1. Obtain multi-angle projection data.

Based on the X-ray tube, the isocenter arc motion projection is performed, and the X-ray flat panel detector is used to shoot the X-ray projections at equal angle intervals to obtain multi-angle projection data.

This embodiment collects projection data from 15 angles, and the total range of projection angles is 15°. Compared with traditional CT acquisition and projection, its projection angle range is smaller, the number of acquisitions is smaller, and it is less harmful to people.

As shown in Figure 2, the center line running on the center arc of the X-ray tube is defined as the z-axis. The intersection of the plane where the arc is located and the detector plane is defined as the x-axis. Then the intersection point of the z-axis and the detector plane is Center O, assuming 0° is projected with the Z axis as the center, the collected projection angle range is (-7.5°, 7.5°), and the projection data collected at 15 angles are -7×(7.5°/7), - 6×(7.5°/7), -5×(7.5°/7), -4×(7.5°/7), -3×(7.5°/7), -2×(7.5°/7), - 1×(7.5°/7), 0°, 1×(7.5°/7), 2×(7.5°/7), 3×(7.5°/7), 4×(7.5°/7), 5× (7.5°/7), 6×(7.5°/7), 7×(7.5°/7).

Step 2. Preprocess the projection data based on Beer's theorem, that is, perform a logarithmic transformation operation to obtain the preprocessed projection data.

The expression of the preprocessed projection data is as follows:

;

in, Indicates the projection angle;/> Represents the preprocessed projection angle/> projection data;/> Represents the unpreprocessed projection angle/> projection data;/> Represents the logarithmic operation with constant e as the base.

It should be noted that the unpreprocessed projection angle projection data/> Including the x-axis coordinate and y-axis coordinate projected on the detector plane without preprocessing, that is/> .

Preprocessed projection angle projection data/> , including the x-axis coordinate and y-axis coordinate projected on the detector plane after preprocessing, /> .

Indicates step 3. Based on the displacement registration method of isocentric arc motion, perform block coordinate translation processing on the preprocessed multi-angle projection data to obtain the translated projection data.

Step 3.1. Obtain the preprocessed projection data.

Step 3.2. Based on the preset isocentric arc motion model with different reconstruction layer depths, calculate the displacement of the preprocessed projection data at different angles, and obtain the displacement of the projection data along the x-axis determined by the angle and reconstruction layer depth. . Specifically, an isocenter arc motion model is constructed in advance, as shown in Figure 2. The center line of the X-ray tube isocenter arc movement is defined as the z-axis, and the intersection line between the plane where the arc is located and the detector plane is defined as x axis, then the intersection point of the z axis and the detector plane is the center O, and the straight line perpendicular to the x axis in the detector plane is the y axis.

The preprocessed projection angle The projection data of is expressed as/> , including the x-axis coordinate and y-axis coordinate of the projection of the detector plane. Next, step 3.3 of this embodiment will determine the x-axis coordinate/> Perform registration.

In this step, according to the distance from the detector plane, that is, the plane formed by the x-axis and the y-axis is a non-negative integer multiple of 1mm, 62 reconstruction layers of different depths are set above it, respectively labeled: 0, 1, 2, ... , 61, which means the maximum thickness of the reconstruction layer is set to 61mm.

with depth Take the reconstruction layer 61 as an example, mark point P/> For any point on the reconstruction layer, when the X-ray tube is at the central projection angle (i.e. 0°), the position of the X-ray tube is recorded as point R(0,d), then the ray RP intersects the x-axis at point N(x _N ,0), the projection of point P on the x-axis is recorded as point C/> , the projection of point P on the z-axis is recorded as point F/> ;

When the X-ray tube projection angle is θ, the position of the X-ray tube is recorded as point S (-dsinθ, dcosθ), then the ray SP intersects the x-axis at point M (x _M ,0), and the projection of point S on the x-axis It is marked as point H(-dsinθ,0), and the projection of point S on the z-axis is marked as point D(0,dcosθ).

Among them, d is the rotation radius of isocentric arc motion, To reconstruct the depth of the focusing layer, that is, to reconstruct the distance between the focusing layer and the X-ray detector plane, θ is the angle of the current projection of the X-ray tube relative to the center projection, and the projection of the center projection is 0°. /> is the x-axis coordinate of a point P on the reconstruction layer to be translated and aligned.

In the triangle constructed, ,/> , based on the similarity relationship:

;

Put the corresponding coordinates into the above two formulas to get:

.

In Figure 2, NM is the displacement along the x-axis on the detection surface relative to the central projection (projection angle is 0°) when the projection angle is, let =NM= x _M -x _N , then the expression of the displacement used for registration is as follows:

;

in, Indicates the projection angle;/> Indicates that the projection angle is/> The x-axis coordinate to be translated;/> Indicates the reconstruction layer depth;/> Indicates that when the reconstruction layer depth is/> , the projection angle is/> When , the displacement of the projection data along the x-axis; d represents the radius of the isocenter arc.

The first term of the displacement formula, , is a linear function related to the horizontal position and projection angle of the projected object. Its physical meaning is the linear transformation of the projection displacement on the x coordinate to achieve the standardization of the center projection;

The second term of the displacement formula, , only related to the projection angle/> Relevant, indicating different angles after normalization/> The relative displacement on the x-axis required when the projection is calibrated toward the center.

It is worth noting that when the detection surface also swings within a small angle ±φ with the X-ray tube at the same time, each displacement calculated by the above formula needs to be multiplied by , n=0,1,2,...m; 2m+1 is the number of projection angles. Usually the φ value is very small and can be ignored, so the cosine value is taken directly/> is 1.

Finally, the displacement along the x-axis of any point P on each reconstruction layer is obtained.

Step 3.3: According to the displacement of the projection data along the x-axis, perform block coordinate translation processing on the preprocessed projection data to obtain the translated projection data.

It should be noted here that the preprocessed projection data in step 2 includes the projection data of the detector plane at 15 projection angles, and the z-axis coordinate is 0 at this time. Steps 3.1 and 3.2 obtain the displacements of the x-axis components of different depth reconstruction layers and different projection angles. The preprocessed projection data is processed by block coordinate translation to obtain the translated projection data, which is equivalent to the original detector. Planar projection data accumulates multiple reconstruction layers of different depths.

Therefore, the projection data after translation is expressed as ,/> , where,/> Indicates that the projection angle is The x-axis coordinate after time translation,/> ,/> Indicates that the projection angle is/> The x-axis coordinate to be translated;/> Indicates that the projection angle is/> The y-axis coordinate at;/> Indicates the reconstruction layer depth.

Step 4: Perform image interpolation processing on the pixel vacancy values in the translated projection data to obtain interpolated projection data.

Get the translated projection data;

Perform pixel gap search processing on the translated projection data to obtain the pixel gap value;

According to the pixel vacancy value, a one-dimensional linear interpolation method is used to interpolate the adjacent pixels on both sides of the pixel vacancy value to obtain the interpolated projection data.

Specifically, after the preprocessed projection data is subjected to block coordinate translation processing, that is, after linear transformation of the x-axis component of the horizontal position, pixel gaps in the y-axis component are prone to occur.

In this step, first start with the translated projection data , find the pixel gap value of the y-axis component/> , take the pixel gap value/> The upper and lower adjacent pixels/> ,/> Find the average and interpolate it. The expression of interpolation is:

;

in, Represents the pixel gap value of the y-axis component in the translated projection data;/> Represents the pixel gap value Adjacent upper pixel value;/> Indicates the pixel vacant value/> The adjacent lower pixel value.

Image interpolation processing is shown in Figure 4. After the linear position transformation of the horizontal position of the projection data, pixel vacancies and other phenomena will appear. As the projection angle of the X-ray tube changes, the position of the projected image on the X-ray detector also undergoes corresponding displacements. , use the displacement registration formula proposed by this method to standardize, shift and register the projection image, and more accurate focus reconstruction layer information can be extracted.

Step 5: Output the DBT reconstruction layer based on the interpolated projection data.

In this step, the displacement superposition method (ShiftAndAdd, SAA) is used for DBT reconstruction, which mainly superimposes and averages the registered multiple projections, which has the advantage of being fast and simple. The advantages of the present invention will be demonstrated and analyzed based on this reconstruction method later.

In addition, you can also use the filtered back projection method (Filtered Back Projection, FBP), the maximum likelihood expectation maximum method (Maximum Likelihood Expectation Maximization, MLEM), the blind source separation based focusing layer separation reconstruction method (BlindSource Separation basedSeparatingtheFocusing Plane, BSFP) for DBT reconstruction.

In the current literature on the prior art, most of them use the mode of X-ray tube running parallel to the detection surface to derive the displacement formula. The derivation process is as follows:

Establish a coordinate system as shown in Figure 3. When the X-ray tube is located at the first projection angle, its projection on the x-axis is at , at this time, the X-rays pass through z, /> respectively on the z-axis. , fall to x ₁ and b ₁ respectively on the x-axis, corresponding to when the X-ray tube is located at the central projection angle, the rays emitted fall to x ₀ and 0 respectively on the x-axis. Define projection magnification/> , D represents the height of the X-ray tube. Record the depth at this time as/> When , the displacement of the projection of the first projection angle relative to the center projection on the x-axis is :

;

In the formula, Represents the x-axis projection component of the X-ray tube;/> Indicates that the reconstruction layer depth is/> projection magnification. The above formula shows that the displacement on the x-axis is related to the reconstruction depth and the position of the X-ray tube.

Then for the layer with reconstruction depth z, its x displacement is:

;

Then the reconstruction depth is z, The relative displacement between the projections on the x-axis is:

;

In the same way, when the X-ray tube is projected on the x-axis as When , the reconstruction depth is z,/> The relative displacement between the projections on the x-axis is:

.

In order to compare and verify that the displacement formula of the present invention can be used to register multiple projections more accurately, the focusing layer reconstruction effect after registration is compared between the displacement formula of the prior art and the displacement formula proposed by the present invention, as shown in Figure 4 HOLOGIC The focus layer reconstruction based on SAA for 15 projections collected by the company's DBT system is used as an example.

As shown in Figure 5, the reconstructed focusing layer of the same depth is selected for comparative analysis of visual contrast effects. Figure 5(a) is the reconstructed focusing layer corrected by the original method shown in Figure 3. After being corrected by the present invention, Figure 5(a) b) is the reconstructed focus layer image corrected by the present invention minus the reconstructed image corrected by the original method. Figure 5(c) is the difference diagram of Figure 5(a) and Figure 5(b). It can be seen that the difference between the two calibration points is very small near the middle part, but there is a big difference in the edge and both sides of the gland in the reconstructed image. The farther away from the central axis of the gland, the greater the difference.

For the four reconstructed calibration points marked in Figure 5(a) and (b), images of small dots at the same position were intercepted, and the reconstructed small dots were magnified 800 times for observation, as shown in Figure 6. Comparing Figure 6(a) and (b), Figure 6(a) has obvious artifacts on the side close to the middle axis; Figure 6(b) Although the processing result of the displacement formula proposed by this method also has a small amount of artifacts exists, but compared to Figure 6(a), it greatly reduces the artifacts of the reconstruction points; it can be seen from Figure 6(g) and Figure 6(h) that when the background is bright, Figure 6 (g) The contrast of the reconstructed points obtained using the original displacement formula is greatly reduced, and its boundary points become blurred; while Figure 6(h) is the corrected image. Not only is the focus better, but its contrast is also significantly increased, and the boundaries are more clearly. Comparison between Figure 6(a) and Figure 6(b), Figure 6(c) and Figure 6(d), Figure 6(e) and Figure 6(f), Figure 6(g) and Figure 6(h) , it can be verified that the registration accuracy of the displacement formula of the present invention is significantly higher than that of the original displacement formula, and the blurring and artifacts of the focus point are reduced.

Figure 7(a) and Figure 7(b) are respectively a comparison of the effects of reconstructed layers using projections registered by the original displacement method and the method of the present invention. The upper part is the reconstructed layer, and the lower part is its corresponding Fourier transform. Transform, FT) spectrum. From the comparison of the reconstructed focusing layers in Figure 7(a) and (b), after using the displacement registration formula of the present invention to correct the angle projection registration, the focused small metal in the reconstructed layer is clearer and the image contrast is higher. Analyzing the spectrum of the reconstruction layer, Figure 7(a) shows that the frequency is cleaner in the transverse direction, but there is more high-frequency noise in the longitudinal direction, which indicates that high-frequency noise is generated during the longitudinal calibration process. In contrast, the spectrum corresponding to the reconstruction layer in Figure 7(b) is cleaner both horizontally and vertically, indicating that after displacement correction by the method of the present invention, the projection registration is more accurate and more noise is avoided during the correction process. It can make the focus layer texture clearer, have higher contrast and suppress blur.

Those skilled in the art will understand that embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment that combines software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each process and/or block in the flowchart illustrations and/or block diagrams, and combinations of processes and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a use A device for realizing the functions specified in a process or processes in a flowchart and/or a block or blocks in a block diagram.

These computer program instructions may also be stored in a computer-readable memory that causes a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including the instruction means, the instructions The device implements the functions specified in a process or processes in the flowchart and/or in a block or blocks in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device, causing a series of operating steps to be performed on the computer or other programmable device to produce computer-implemented processing, thereby executing on the computer or other programmable device. Instructions provide steps for implementing the functions specified in a process or processes of a flowchart diagram and/or a block or blocks of a block diagram.

The above are only the preferred embodiments of the present invention. It should be pointed out that those of ordinary skill in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (4)

1. A DBT reconstruction method for multi-angle projection registration, comprising the steps of:

acquiring multi-angle projection data;

preprocessing the projection data based on the Bell theorem to obtain preprocessed projection data;

performing block coordinate translation processing on the preprocessed projection data based on a displacement registration method of the isocenter circular arc motion to obtain translated projection data;

performing image interpolation processing on the pixel blank value in the translated projection data to obtain interpolated projection data;

obtaining and outputting a digital mammary gland tomosynthesis DBT reconstruction layer based on a digital mammary gland tomosynthesis DBT reconstruction algorithm according to the interpolated projection data;

wherein the expression of the preprocessed projection data is as follows:

；

wherein,representing a projection angle; />Representing the projection angle after pretreatment +.>Is a projection data of the image sensor; />Representing the projection angle without pretreatment +.>Is a projection data of the image sensor; />A logarithmic operation based on a constant e;

the displacement registration method for the isocentric arc motion comprises the following steps:

acquiring preprocessed projection data;

calculating displacement amounts of the preprocessed projection data of different angles based on preset isocentric arc motion models of different reconstruction layer depths, and obtaining displacement amounts of the projection data determined by the angles and the reconstruction layer depths along an x-axis;

carrying out block coordinate translation processing on the preprocessed projection data according to the displacement of the projection data along the x-axis to obtain translated projection data;

the expression of the displacement amount of the projection data along the x-axis is as follows:

；

wherein,representing a projection angle; />Indicating that the projection angle is +.>An x-axis coordinate to be translated; />Representing a reconstructed layer depth; />Indicating when the reconstructed layer depth is +.>Projection angle is +.>The displacement of projection data along the x-axis;drepresenting the radius of the isocentric arc;

the translated projection data is expressed as:

；

wherein,representing the translated projection data; />Indicating that the projection angle is +.>The x-axis coordinates after the time-shift,，/>indicating that the projection angle is +.>An x-axis coordinate to be translated; />Indicating that the projection angle is +.>Y-axis coordinates at time; />Representing the reconstructed layer depth.

2. The DBT reconstruction method of multi-angle projection registration according to claim 1, wherein the acquiring multi-angle projection data comprises:

based on the X-ray tube, the projection of the isocentric arc motion is carried out, the X-ray projection is shot at equal angular intervals by using a detector, and multi-angle projection data are obtained.

3. The DBT reconstruction method of multi-angle projection registration according to claim 1, wherein obtaining interpolated projection data comprises:

acquiring translated projection data;

performing pixel vacancy searching processing on the translated projection data to obtain a pixel vacancy value;

and according to the pixel blank value, adopting a one-dimensional linear interpolation method to take pixels at two adjacent sides of the pixel blank value for interpolation, and obtaining the interpolated projection data.

4. The multi-angle projection registered DBT reconstruction method according to claim 3, wherein the one-dimensional linear interpolation is expressed as follows:

；

wherein,pixel null values representing the y-axis component in the translated projection data; />Representing pixel values of vacanciesAdjacent upper pixel values; />Representing pixel null value +.>Adjacent lower pixel values.