CN112986286B - X-ray dual-field microscopy imaging detection system and imaging method thereof - Google Patents

Abstract

The invention provides an X-ray double-view microscopic imaging detection system, which comprises: an optical path lengthening device for extending the application of the system to enable a majority of the microscope objective to be integrated into the system; the double-view imaging device is used for acquiring images with different resolutions under two views; and the registration adjusting device is used for obtaining the registered original image. The invention also provides an imaging method based on the truncated data correction reconstruction of the X-ray double-field microscopic imaging detection system. The method corrects the bright ring artifact of the truncated data reconstruction image, so that the numerical value of the region-of-interest reconstruction image is closer to the true value. The invention realizes the reconstruction of the global image of the large sample, and the reconstructed image comprises the interested region with high resolution.

Description

X-ray dual-field microscope imaging detection system and imaging method thereof

technical field

The invention relates to the field of X-ray radiation imaging, in particular to an X-ray dual-view microscopic imaging detection system formed by dual optical paths and a reconstruction imaging method for truncation correction of dual-view data.

Background technique

X-ray computed tomography (CT), as a nondestructive evaluation technique, is widely used in internal sample detection in different fields, such as biomedicine, aerospace, construction, and geology. Sampling data is truncated when larger samples are imaged in a limited X-ray imaging field of view (FOV). In medicine, truncated data is also generated when only internal ROIs are imaged in order to reduce radiation dose. Truncated sampled data for reconstruction produces severe artifacts, including goblet artifacts and bright outer rings. To date, many methods have been proposed to reconstruct regions of interest (ROI) using truncated data. One of them is the use of back-projection filtering (BPF) based reconstruction algorithms (BPF-POCS). The BPF-POCS reconstruction algorithm can reconstruct the truncated data at both ends, but it needs to know a small part of the image in advance, and this prior knowledge is usually not easy to obtain. Another class of methods are preprocessing methods based on extrapolation. The method is based on fitting elliptical boundary segments or using symmetric mirroring and smoothing on truncated data. Truncated data is often supplemented with non-truncated data. The reconstructed images obtained by this method can reduce goblet artifacts and bright outer ring artifacts, but the reconstruction data obtained by this method are not accurate enough quantitatively. Other methods, such as the offset detector method, require a balance between sampling data acquisition time or radiation dose and computational complexity. Therefore, accurate imaging of truncated data and truncation artifact correction remain a challenge for X-ray CT imaging.

SUMMARY OF THE INVENTION

In view of this, the main purpose of the present invention is to provide an X-ray dual-field microscopic imaging detection system and an imaging method thereof, so as to partially solve at least one of the above technical problems.

In order to achieve the above purpose, as an aspect of the present invention, an X-ray dual-field microscopic imaging detection system is provided, comprising:

an optical path extension device for extending the application of the system so that most of the microscope objectives can be integrated into the system;

Dual field of view imaging device, used to obtain images with different resolutions in two fields of view;

A registration adjustment device for obtaining a registered original image.

Wherein, the optical path extension device includes:

Relay lens, used to expand the space in front of the objective lens for easy installation of beam splitters and optical path adjustment;

The sleeve with adjustable length is used for connecting the scintillator and the relay lens in the dual-field imaging device, and includes a fixing ring, an adjusting ring and a locking ring.

Wherein, the fixing ring is clamped and fixed on the relay lens with screws, and the other end of the fixing ring is connected with a sleeve adjusting ring with a screw thread. relative distance of the mirror.

Wherein, the dual-view imaging device includes two optical paths:

The total optical path consisting of scintillator, sleeve, relay and beam splitter;

The beam splitter splits the visible light into two branches.

The imaging fields and resolutions of the two branch optical paths are different; the beam splitter is used to separate the light beams before the objective lens is imaged, and then the objective lenses with different magnifications and the tube lenses matched with the objective lenses are used in the two branch optical paths. CCD to achieve.

Wherein, the scintillator is located at the working distance of the relay lens; the distance between the objective lens and the relay lens is the sum of the working distance of the objective lens and the working distance of the relay lens; the beam splitter is placed between the relay lens and the objective lens for convenience Any optional location for mounting; the CCD is located at the working distance of the tubescope.

Wherein, the focus adjustment method of the dual-view imaging device includes:

Adjust the front-end total optical path and the reflection branch optical path; specifically, change the relative position of the scintillator and the relay lens by rotating the sleeve adjustment ring, until the CCD of the optical path collects a clear image; with different installations and adjustments, the optical path objective lens and An infinite or finite beam path is formed between the tube mirrors;

Adjusting the optical path of the transmission branch; specifically including using a motorized precision stage to adjust the position of the magnification objective lens on the optical path of the transmission branch until the optical path is clearly imaged; with different installations and adjustments, the optical path objective lens and the tube lens can form infinity or Limited beam path.

Wherein, the registration adjustment device includes:

Reflector;

The installation and adjustment bracket includes a thickening table and an adjustment mechanism that can realize pitch and left-right rotation; the adjustment mechanism is fixed on the dark box of the detection system by two diagonal screws, and the rotation direction is adjusted by another two screws.

Wherein, the registration adjustment method of the registration adjustment device includes:

Use interpolation methods to process low-resolution images with large fields of view;

The processed low-resolution image of large field of view and the high-resolution image of small field of view are directly subtracted to obtain a difference map to calculate the offset of rows and columns;

The registration adjustment device is adjusted according to the offset, and then the sampled images are obtained to calculate the difference map; the iterative adjustment is performed in this way.

As another aspect of the present invention, there is provided an imaging method of the above-mentioned X-ray dual-field microscopy imaging detection system, comprising the following steps:

Acquire dual-field sampling data on the X-ray dual-field microscopic imaging detection system, of which one set is non-truncated large-field low-resolution data, and the other is truncated small-field high-resolution data;

Perform differential back-projection calculations on the dual-view sampling data to obtain two sets of differential back-projection images;

In the differential back-projection image, the differential back-projection image of the high-resolution data of the small field of view is used as the reference template image, and the low-resolution image of the large field of view is used as the input image; the registration algorithm is used for the registration calculation, and the affine transformation corresponding to the input image is obtained. The matrix is used for the input image to obtain a dual-field differential back-projection image that is finely registered by the algorithm;

Calculate the average value of the region of interest of the two sets of data after registration, and the ratio of the average value of the differential back-projection image of the small field of view divided by the average value of the differential back-projection image of the large field of view is used as a weighting coefficient multiplied by the differential back-projection image of the large field of view;

Use the non-truncated large-field low-resolution differential back-projection image to supplement the truncated small-field high-resolution differential back-projection image to obtain a non-truncated small-field high-resolution differential back-projection image, and complete the truncated data correction;

The reconstruction is completed by performing Hilbert transform and weighting on the non-truncated small-field high-resolution differential back-projection image.

Based on the above technical solutions, the X-ray dual-field microscope imaging detection system and the imaging method thereof of the present invention have at least a part of the following beneficial effects compared with the prior art:

The invention realizes the accurate imaging of the truncated data, and at the same time, the truncation artifact is well corrected. That is, the bright ring artifacts of the ROI reconstructed image are removed, and the value of the ROI reconstructed image is closer to the real value.

The invention provides an X-ray dual-view imaging detector, which can simultaneously obtain the global image of the tested sample and the local high-resolution image of the ROI, and solves the problem that the ROI resolution of the low-resolution global image is too low, resulting in unclear details. The detector can be used for digital radiography or CT imaging, etc.

The invention provides an X-ray image fusion method, which is used for correcting high-resolution ROI truncation data, assisting in correcting bright ring artifacts of reconstructed images and improving the accuracy of reconstruction numerical values. This method can be used for the sampled images of the X-ray dual-field imaging detector provided in this paper, and also for the images acquired multiple times at different resolutions by any detector.

Description of drawings

Fig. 1 is the X-ray dual-field microscopic imaging detection system of the present invention;

Fig. 2 schematically shows the mirror used for mechanical registration in Fig. 1 and its mounting and adjusting bracket;

Fig. 3 schematically shows the adjustable length sleeve of the optical path extension device in Fig. 1;

FIG. 4 is a flow chart of a method for correcting truncated data based on data fusion for ROI imaging according to the present invention.

In the above drawings, the meanings of the reference symbols are as follows:

1. Sleeve; 2. Relay lens; 3. Beam splitter; 4. Objective lens stage; 5-1, Objective lens; 5-2, Objective lens; 6. Tube lens; 7. Reflector and installation and adjustment bracket; 8 , CCD; 9, camera obscura device; 10, angle fine-tuning device; 11-1, pitch angle fine-tuning device; 11-2, left and right angle fine-tuning device; 12, angle fine-tuning device mounting hole; 13, thickening table; ; 15, sleeve cover; 16, adjusting ring; 17, locking ring; 18, fixing ring.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The purpose of the present invention is to obtain the sampling data of a large sample based on the X-ray micro-CT imaging system, without the need for prior information and without significantly increasing the amount of calculation, to reconstruct a high-resolution image of the ROI inside the sample, and to expand the X-ray image. Scope of application of X-ray micro-CT.

The invention discloses a dual-view X-ray microscopic imaging detection system. In this system, a relay lens is added to expand the space in front of the objective lens for easy installation of beamsplitters and optical path adjustment. The beam splitter separates the light to form two imaging branch optical paths. Each branch optical path uses an objective lens. The magnification and field of view of the two branch optical paths are different to form a double field of view, which can simultaneously obtain non-truncated low-resolution sampling data and truncated high-resolution sampling data. rate sampling data. In addition, in order to obtain the registered image, a mirror and its installation and adjustment bracket are added to the transmission branch light path of the detection system, and the registration of the dual-view system is realized by adjusting the posture of the mirror. The addition of the reflector makes the photosensitive chip of the optical path CCD not facing the radiation source, thus protecting the CCD.

The invention also discloses a truncation data correction method for data fusion. The method includes data registration and fusion. The initial registration of the transmission branch optical path and the reflection branch optical path is achieved by mechanical adjustment, which replaces the commonly used downsampling coarse registration calculation. In order to reduce the amount of data processing, save time and storage space, and avoid the accumulation of calculation errors caused by registration and fusion on hundreds or thousands of sampled images, the algorithm fine registration and fusion are not completed on the sampled images. Rather, it is done on Differential Back Projection (DBP) data obtained during the BPF reconstruction algorithm. Firstly, the differential back-projection calculation is performed on the sampled data to obtain two sets of DBP data. Algorithm fine registration is then performed on the truncated high-resolution DBP data and the non-truncated low-resolution DBP data. Then calculate the ratio of the average value of the ROI area of the non-truncated low-resolution and truncated high-resolution DBP data, and multiply the truncated high-resolution DBP data by the ratio to make the grayscale range of the two sets of DBP data consistent. Then use the non-truncated low-resolution DBP image to complete the edge data of the truncated high-resolution DBP image, and obtain the non-truncated high-resolution DBP image to complete the fusion. Finally, perform Hilbert transform and weighting, = get the reconstructed image.

As shown in Figure 1, it is a dual-field X-ray microscopic imaging detection system, which includes a sleeve 1, a relay lens 2, a beam splitter 3, an objective lens displacement stage 4, an objective lens 5-1, and an objective lens 5-2 , tube mirror 6, reflector and installation and adjustment bracket 7, CCD8, dark box device 9; wherein, the sleeve 1 and the relay lens 2 constitute an optical path extension device, and the scintillator is located at the front end of the sleeve 1. The beam splitter 3 also includes two branch optical paths formed by separating the visible light. The branch optical paths all include objective lens 5-1 or 5-2, tube lens 6 and CCD8. The reflector and its installation and adjustment bracket 7 constitute a mechanical registration adjustment device located in the transmission branch optical path. The optical path systems behind the optical path extension device are all enclosed in the dark box device 9, which not only realizes the protection from light but also facilitates the installation of components.

Different from the common X-ray optocoupler detection system, the present invention installs the beam splitter in the infinity optical path at the front end of the objective lens instead of the rear end of the objective lens, so as to achieve the purpose of including one objective lens in each of the two branch optical paths. The objective lens is the core element for realizing dual fields of view in the present invention. Objective lenses with different magnifications and fields of view are installed in the two branch optical paths to simultaneously obtain high-resolution data of small field of view and low-resolution data of large field of view.

In the specific design, according to the imaging system parameters, the side length of the beam splitter cube is preferably 25.4 mm, so the working distance of the objective lens is required to be large enough to install the beam splitter. The working distance of the microscope objective lens is generally several millimeters to more than thirty millimeters. In order to enable most objective lenses to be used in the optical path system, the present invention adds an optical path extension device at the front end of the objective lens, thereby expanding the available space for installing beam splitting. mirror and easy to adjust the light path.

Common objective lens magnifications are 1X, 2X, 4X, 5X, 10X, 20X and 40X. Theoretically, any brand of objective lens with any two magnifications can be combined for dual-field detection. The working distance of different types and brands of objective lenses is quite different, and the selection of objective lenses needs to consider the focus adjustment and image distortion of the two optical paths. Preferably, the two objective lenses of the branch optical path of the optical path use objective lenses of the same brand and type with different magnifications. In this example, Sigma MplanApo 2X and MplanApo 5X objective lenses are used. Its working distances are 34mm and 41mm, and the actual field of view (1/2 inch of the camera element) is 2.4 x 3.2mm and 0.96 x 1.28mm.

Preferably, the relay lens of the optical path extension device of the system uses a doublet lens. In this example, a pair of Atmund C-mount achromatic lenses are used, the magnification ratio is 1:1, the working distance is 60mm, the length is appropriate, and the working wavelength is 425-675nm, which is comparable to the wavelength of light emitted by the scintillator (central wavelength). 550nm) is highly matched.

The ratios of reflected light to transmitted light of common beam splitters are 1:1, 2:3 and 3:7, etc., which can be theoretically used in the dual-field X-ray microscopic imaging detection system of the present invention. Preferably, a beam splitter with a ratio of reflected light to transmitted light of 1:1 is used to reduce the difference in the number of photons and the difference in noise and the like between the two optical paths.

As shown in FIG. 2 , a mirror for mechanical registration and its installation and adjustment bracket are used to obtain the original image of registration, which is beneficial to subsequent processing. The device consists of an angle adjustment device 10 , a thickening table 11 , and a reflector 12 . The fixing structure 12 fixes the mechanical registration adjusting device on the rear panel of the camera obscura device 9 . The thickness of the thickening table 11 is determined according to the working distance of the tube mirror.

The angle adjustment device 10 is composed of two screws and three adjustment plates. Rotate the pitch angle adjustment screw 11-1 to drive the mirror to deflect in the pitch direction to change the imaging position of the image line. Similarly, turning the left and right angle adjustment screws 11-2 drives the mirror to deflect in the left and right directions, thereby changing the imaging position of the image column. Angle scales are designed around the pitch angle adjustment screw 11-1 and the left and right angle adjustment screws 11-2, so that the mirror posture can be adjusted more accurately.

In this example, the reflection branch light path uses a small magnification objective lens, and the transmission branch light path uses a large magnification objective lens. On the contrary, the adjustment method is similar. A simple sample such as a sphere with a diameter of 0.5-1 μm was selected as the imaging sample for the registration adjustment process. The mechanical registration method based on the mechanical registration adjusting device of the present invention is specifically:

Step 1: Obtain an image of the reflection branch light path as a reference image. Adjust the position of the sample on the sample stage so that the image center is located at or near the center of the reflection branch light path image to obtain a low-resolution image of the reflection branch light path. Use interpolation in the acquired image to get a "high" resolution image. The surrounding edge pixels are cut off, so that the remaining image pixels are consistent with the original image, and this image is used as the reference image. In this example, the bilinear interpolation method is used, and other suitable interpolation methods can also be used.

Step 2: The transmission branch optical path collects and acquires an image, and subtracts it from the reference image obtained in step 1 to obtain a difference image. Compute row and column position offsets on the difference image. Calculate the angle that the corresponding screw in the registration adjusting device needs to be rotated according to the deviation.

Step 3: Rotate the pitch angle adjustment screw 11-1 and the left and right angle adjustment screws 11-2 of the registration adjustment device to change the position of the mirror to change the position where the light reaches the detector. An image of the transmission branch light path is acquired for each adjustment.

Step 4: Repeat steps 2 and 3 until the position offset of rows and columns in the difference image is 0.

As shown in FIG. 3 , it is a schematic diagram of the structure of the adjustable length sleeve of the optical path extension device. In the present invention, an optical path extension device is designed in the dual-field X-ray microscopic imaging detection system, so that most microscope objective lenses (including plan achromatic objective lens, plan fluorite objective lens, superapochromatic objective lens, long working distance achromatic objective lens, etc.) objective lens, etc.) can be integrated into the system, expanding the application of the system. The optical path extension device includes a retractable sleeve and a relay lens. The sleeve connects the relay lens and the scintillator, including the sleeve cover 15 , the adjusting ring 16 , the locking ring 17 and the fixing ring 18 . The adjusting ring 16 and the locking ring 17 have internal threads, and the fixing ring 18 has corresponding external threads. The scintillator is installed at the front end of the adjusting ring 16, and the sleeve cover 15 is screwed onto the adjusting ring 16 to protect the scintillator and avoid light. The adjusting ring 16 and the locking ring 17 are assembled to the fixing ring 18 using threads, and the fixing ring 18 is clamped and fixed on the relay lens with screws.

The retractable sleeve is also used for focusing adjustment of the optical path, and the adjusting ring 16 spirals forward or backward to adjust the position of the scintillator in the optical path until the reflection branch optical path is clearly imaged. The scintillator is now located at the working distance of the relay lens.

Further, the transmission branch optical path of the present invention realizes clear imaging by adjusting the position of the optical path objective lens, specifically, the objective lens is installed on the objective lens displacement stage 4, and the motorized displacement stage is moved with the objective lens through the control software until the branch optical path collects a clear image. Image. Due to factors such as the installation error of the objective lens, tube lens and CCD, with different installation adjustments, when the optical path is clearly imaged, an infinite or finite optical path can be formed between the objective lens and the tube lens of the two branch optical paths.

As shown in FIG. 4 , it is a flowchart of a method for correcting truncated data based on data fusion for ROI imaging. The method is based on truncated high-resolution ROI data, and uses non-truncated low-resolution data for correction to obtain non-truncated high-resolution ROI data. The correction process includes data fine registration and fusion. This method proposes to reconstruct the sampled data using a back-projection filtering (BPF) algorithm, which first computes the DBP image, and then performs one-dimensional filtering on the DBP image along the PI line to reconstruct the image. The BPF algorithm can only calculate the image of the PI line where the selected ROI is located. Therefore, the registration and fusion of this method are not done in the sampled data but in the DBP image, which avoids a lot of data storage and processing time, and avoids the accumulation of calculation errors caused by registration and fusion in the sampled data respectively.

The specific process of the truncated data correction method is as follows: firstly, based on the X-ray dual-field microscopic detection device proposed by the present invention, preliminary registered truncated high-resolution sampling data and non-truncated low-resolution sampling data are obtained. Then, differential back-projection is performed to obtain DBP images, which are denoted as DBP1 and DBP2. Next, the registration algorithm is iterated on DBP1 and DBP2 to obtain finely registered images, denoted as DBPf1 and DBPf2. Next, the image after fine registration is fused to match the pixel value gray level, calculate the ratio of the average gray value of the ROI area of the fine registration image DBPf1 and DBPf2, and weight the ratio to the DBPf1 image to obtain the pixel gray value. The images with the same degree range are denoted as DBPw1 and DBPw2. Then, the DBPw2 image of the large field of view and the low-resolution image are used to supplement the edge of the high-resolution image of the small field of view DBPw1. The corrected DBPr1 image is subjected to Hilbert transform and weighting to obtain the ROI reconstruction image.

In this example, the Lucas-Kanade algorithm is used for fine registration, and the high-resolution image with a small field of view is used as a template image, and the low-resolution image with a large field of view is used as the image to be transformed for operation.

The correction method of the present invention can be applied to both a two-dimensional image of a slice of a certain layer and a three-dimensional image. For example, the two-dimensional or three-dimensional Lucas-Kanade algorithm is used in the fine registration of the algorithm, and the corresponding bilinear interpolation or trilinear interpolation is used in the operation process. The rest of the processing of 2D images is the same as that of 3D images. The algorithm fine-registration step in the present invention can use any suitable registration algorithm to achieve registration on DBP images.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned specific embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principle of the present invention, any modifications, equivalent replacements, improvements, etc. made should be included within the protection scope of the present invention.

Claims (4)

1. an X-ray dual-field microscopic imaging detection system, is characterized in that, comprises: an optical path extension device for extending the application of the system, enabling a variety of microscope objectives to be integrated into the system; Wherein, the optical path extension device includes: Relay lens, used to expand the space in front of the objective lens for easy installation of beam splitters and optical path adjustment; A sleeve with an adjustable length for connecting the scintillator and the relay lens in the dual-field imaging device, including a fixing ring, an adjusting ring and a locking ring; Wherein, the fixing ring is clamped and fixed on the relay lens with screws, and the other end of the fixing ring is connected with the adjusting ring with a screw thread. relative distance; Dual field of view imaging device, used to obtain images with different resolutions in two fields of view; Wherein, the dual-view imaging device includes two optical paths: The total optical path consisting of scintillator, sleeve, relay and beam splitter; The two branch optical paths formed after the beam splitter separates the visible light; The imaging fields and resolutions of the two branch optical paths are different; the beam splitter is used to separate the light beams before the objective lens is imaged, and then the objective lenses with different magnifications and the tube lenses matched with the objective lenses are used in the two branch optical paths. CCD to achieve; Wherein, the focus adjustment method of the dual-view imaging device includes: Adjust the front-end total optical path and the reflection branch optical path; specifically, change the relative position of the scintillator and the relay lens by rotating the sleeve adjustment ring, until the CCD of the optical path collects a clear image; with different installations and adjustments, the optical path objective lens and An infinite or finite beam path is formed between the tube mirrors; Adjusting the optical path of the transmission branch; specifically including using a motorized precision stage to adjust the position of the objective lens on the optical path of the transmission branch until the optical path is clearly imaged; with different installations and adjustments, an infinite or finite optical path is formed between the objective lens of the optical path and the tube lens ; a registration adjustment device for obtaining a registered original image; Wherein, the registration adjustment device includes: A reflector and an installation and adjustment bracket, the installation and adjustment bracket includes a thickening table and an adjustment mechanism capable of realizing pitch and left-right rotation; wherein, the reflector and the installation and adjustment bracket form a mechanical registration adjustment device located in the transmission branch light path, and the The adjustment mechanism is fixed on the dark box of the detection system by two diagonal screws, and the rotation direction is adjusted by the other two screws. 2. The X-ray dual-field microscopic imaging detection system according to claim 1, wherein the scintillator is located at the working distance of the relay lens; the distance between the objective lens and the relay lens is the working distance of the objective lens and the relay lens The sum of the working distances of the mirrors; the beam splitter is placed at any optional position between the relay lens and the objective lens that is convenient for installation; the CCD is located at the working distance of the tube lens. 3. The X-ray dual-field microscope imaging detection system according to claim 1, wherein the registration adjustment method of the registration adjustment device comprises: Use interpolation methods to process low-resolution images with large fields of view; The processed low-resolution image of the large field of view and the high-resolution image of the small field of view are directly subtracted to obtain a difference image to calculate the offset of rows and columns; The registration adjusting device is adjusted according to the offset, and the sampled image is obtained to calculate the difference image; the iterative adjustment is performed in this way. 4. An imaging method using the truncated data correction and reconstruction of the X-ray dual-field microscope imaging detection system as described in any one of claims 1-3, characterized in that, comprising the following steps: Acquire dual-field sampling data on the X-ray dual-field microscopic imaging detection system, of which one set is non-truncated large-field low-resolution data, and the other is truncated small-field high-resolution data; Perform differential back-projection calculations on the dual-view sampling data to obtain two sets of differential back-projection images; In the differential back-projection image, the differential back-projection image of the high-resolution data of the small field of view is used as the reference template image, and the low-resolution image of the large field of view is used as the input image; the registration algorithm is used for the registration calculation, and the affine transformation corresponding to the input image is obtained. The matrix is used for the input image to obtain a dual-field differential back-projection image that is finely registered by the algorithm; Calculate the average value of the region of interest of the two sets of data after registration, and the ratio of the average value of the differential back-projection image of the small field of view divided by the average value of the differential back-projection image of the large field of view is used as a weighting coefficient multiplied by the differential back-projection image of the large field of view; Use the non-truncated large-field low-resolution differential back-projection image to supplement the truncated small-field high-resolution differential back-projection image to obtain a non-truncated small-field high-resolution differential back-projection image, and complete the truncated data correction; The reconstruction is completed by performing Hilbert transform and weighting on the non-truncated small-field high-resolution differential back-projection image.

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