CN111399072B

CN111399072B - X-ray projection optimization imaging method and system

Info

Publication number: CN111399072B
Application number: CN202010211038.9A
Authority: CN
Inventors: 请求不公布姓名
Original assignee: Suzhou Qiying Medical Technology Co ltd
Current assignee: Suzhou Qiying Medical Technology Co ltd
Priority date: 2020-03-24
Filing date: 2020-03-24
Publication date: 2023-07-04
Anticipated expiration: 2040-03-24
Also published as: CN111399072A

Abstract

An X-ray projection optimizing imaging method and system, which are characterized in that after a plurality of projection images are obtained by setting a ray source and a detector which are positioned at two sides of a measured object and performing micro-motion shooting around the measured object, a plurality of projection images are subjected to plane reconstruction and superposition averaging, and an optimized projection image with corrected magnification is obtained. The invention obtains the projection image with clear boundary and accurate measurement by using the distance from the smaller ray source to the detector and using the multi-projection irradiation assisted by the magnification correction algorithm.

Description

X-ray projection optimization imaging method and system

Technical Field

The invention relates to a technology in the field of image processing, in particular to an X-ray projection optimization imaging method and system.

Background

Current X-ray two-dimensional projection imaging is typically a cone-beam imaging modality, i.e., a point-like light source that emits X-rays onto a flat panel detector surface. In cone-beam imaging, the closer the object is to the detector, the less magnification if the source-to-detector distance is fixed. Since the magnification of different positions is different in the imaging of the object, the magnification of the projection images of different positions is different, and accurate measurement cannot be performed. To solve the problem of inaccurate measurement, it is desirable to use a parallel beam X-ray imaging method, i.e., the magnification is constant at any position. However, this type of imaging cannot be achieved in practical products, and existing X-ray devices typically achieve near unity magnification by increasing the distance of the focal spot of the source from the detector and placing the imaged object close to the detector.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an X-ray projection optimal imaging method and an X-ray projection optimal imaging system, wherein the projection image with clear boundary and accurate measurement is obtained by using a smaller distance from a ray source to a detector through multiple projection irradiation and an amplification correction algorithm, namely, the amplification consistency of any position is realized.

The invention is realized by the following technical scheme:

the invention relates to an X-ray projection optimization imaging method, which comprises the steps of performing micro-motion shooting around a measured object by arranging a radiation source and a detector which are positioned at two sides of the measured object, obtaining a plurality of projection images, and performing planar reconstruction and superposition averaging on the plurality of projection images to obtain an optimized projection image with corrected magnification.

The micro shooting means that: the radiation source and the detector are controlled to synchronously move in a small range around the center of the imaging object, and the moving range can be a space angle of-6 to 6 degrees; exposing and shooting are carried out simultaneously in the moving process; the method comprises the following steps: the method comprises the steps of controlling a radiation source and a detector to synchronously rotate clockwise or anticlockwise within-6 degrees in a plane with a measured object as a circle center, and synchronously rotating or linearly moving the radiation source and the detector in a direction perpendicular to the plane with the center of the imaged object of the template as a rotation center, wherein the movement range is matched with the rotation range of the plane with the circle center; and (5) performing exposure shooting simultaneously in the moving process.

The radius between the ray source and the circle center is 400 mm-600 mm.

The radius between the detector and the circle center is 200 mm-300 mm.

The planar reconstruction refers to: firstly, determining a reconstruction plane, namely a plane Si perpendicular to a 90-degree X-ray path, and carrying out plane reconstruction, namely back projection on acquired projection images Pj with different angles to each reconstruction plane Si, namely Si=Si+BP (Pj), wherein: BP is a back projection operation procedure, i.e. the signals acquired by each pixel of the detector are mapped to corresponding positions of the reconstruction plane Si according to the X-ray propagation path.

The planar reconstruction is preferably carried out by filtering the images obtained by the plurality of micro shooting before reconstruction.

The superposition average refers to: and accumulating the obtained reconstructed images on the plurality of Si planes according to the respective pixel correspondence, and then carrying out arithmetic average.

Technical effects

The invention integrally solves the problem of inaccurate image measurement caused by different imaging magnification at different positions of the cone beam; compared with the prior art, the invention can obviously reduce the distance from a larger radiation source to a detector in the prior art, saves the equipment space, improves the measurement precision and solves the problem of cone beam amplification imaging.

Drawings

FIG. 1 is a schematic diagram of the method of the present invention;

FIG. 2 is a schematic plan reconstruction;

FIG. 3 is a schematic diagram comparing the principles of the prior art with the embodiment;

in the figure: (a) X-ray parallel beam imaging (a), (b) long distance cone beam imaging (c) short distance cone beam imaging;

FIG. 4 is a schematic diagram showing the effect of the embodiment;

in the figure: (a) a parallel beam X-ray projection image of a hollow cube; (b) is a short-range cone-beam imaging result; (c1) For rotation around an object in a horizontal plane (one dimension), the 5 projection data angles are 84 °, 87 °, 90 °, 93 ° and 96 °, respectively; (c2) The data acquisition mode based on (c 1) is adopted, but each projection image is subjected to high-pass filtering, and then the back projection is carried out, so that the acute angle of the edge of the object is improved; (d1) For rotation around the object in the horizontal plane (one dimension) and translation in the vertical direction (the second dimension) with the detector, the 5 projection data angles are 84 °, 87 °, 90 °, 93 ° and 96 °, respectively, the corresponding detector translation ranges are-3 cm, -1.5cm,0cm,1.5cm and 3cm obtained simulated parallel beam projections;

fig. 5 is a schematic diagram of an embodiment application.

Detailed Description

Taking X-ray imaging of a hollow cube as an example in this embodiment, as can be seen from fig. 3, (a) the image is a parallel beam image, and the projected image edge of the hollow cube is sharp; in contrast, (c) the magnification of the front and rear surfaces of the cube is not the same due to the magnification of the cone beam, resulting in edges in the image that are blurred, and the dimensions of the cube are difficult to measure from (c). All in practical cone beam X-ray imaging, the source is usually located far from the object, as shown in figure (b), in order to be able to obtain accurate measurement data. In fig. (b), the distance from the source to the center of the object is 1.6 meters and the distance from the center of the object to the detector is 0.2 meters; in figure (c), the source is 0.6 meters from the center of the object and the center of the object is 0.2 meters from the detector.

However, the method of fig. 3 (b) has the obvious disadvantage that the whole X-ray imaging system is very bulky.

As shown in fig. 2, the present embodiment includes the steps of:

step 1) performing micro-motion shooting around a detected object by controlling a ray source and a detector to obtainProjection data P at each rotation angle _i ；

Step 2) as shown in FIG. 2, the object to be measured is divided into a plurality of imaging planes S _i In a simulated 90 parallel beam imaging, each imaging plane S is due to the different distances from the source and detector in the 90 projection orientation _i With respective corresponding magnification ratios for projection data P _j Back projection to S _i A plane.

Step 3) back-projecting the corrected image onto an imaging plane S _i The method specifically comprises the following steps: according to any X-ray of the cone beam in figure 2 passing through the imaging plane S _i Finally reach the detector P _j,(x,y) Position (x, y), where j is the j-th projection data, and calculating the (x, y) position of the detector on the imaging plane S under the projection angle of the corresponding deflection degree of the jog shooting according to the imaging geometric relation _i The position on the upper surface is (x _i ,y _i ) Correspondingly realize the imaging plane S _i Back projection onto:

step 4) performing superposition averaging on all imaging planes to obtain simulated parallel beam projection, namely

Where N is the number of imaging planes.

As shown in fig. 5, a system for implementing the method includes: synchronous rotation shooting unit, plane rebuilding unit, stack correcting unit, wherein: the synchronous rotation shooting unit respectively controls the ray source and the detector to perform micro-motion shooting around the measured object and obtain a plurality of projection images, the synchronous rotation shooting unit outputs rotation phase information and the projection images to the plane reconstruction unit, the plane reconstruction unit is connected with the rotation shooting unit and transmits projection image information at different positions, the superposition correction unit is connected with the plane reconstruction unit, and data superposition of all imaging planes are averaged.

As shown in fig. 4, in order to obtain a simulated parallel beam projection using the above method, it can be seen from the figure that the edge blurring effect of the image is greatly improved, but the blurring correction in one direction is due to the other direction. It can be seen from the figure that the edge blurring effect of the image is greatly improved compared with (b) and (c), and that the blurring correction effect in both directions is good. Fig. 4 (d 2) is a data acquisition method based on fig. 4 (d 1), but the sharpness of the object edge is improved as a result of high-pass filtering each projection image and then back-projecting.

The foregoing embodiments may be partially modified in numerous ways by those skilled in the art without departing from the principles and spirit of the invention, the scope of which is defined in the claims and not by the foregoing embodiments, and all such implementations are within the scope of the invention.

Claims

1. A system for implementing an X-ray projection optimized imaging method, comprising: synchronous rotation shooting unit, plane rebuilding unit, stack correcting unit, wherein: the synchronous rotation shooting unit is used for respectively controlling the ray source and the detector to perform micro-motion shooting around the measured object and obtaining a plurality of projection images, outputting rotation phase information and the projection images to the plane reconstruction unit, connecting the plane reconstruction unit with the rotation shooting unit and transmitting projection image information at different positions, connecting the superposition correction unit with the plane reconstruction unit, and superposing and averaging the data of all imaging planes;

the X-ray projection optimization imaging means that: performing micro-motion shooting around the measured object by arranging a ray source and a detector which are positioned at two sides of the measured object, obtaining a plurality of projection images, and performing planar reconstruction and superposition averaging on the plurality of projection images to obtain an optimized projection image with corrected magnification;

the planar reconstruction refers to: firstly, determining a reconstruction plane, namely a plane Si perpendicular to a 90-degree X-ray path, and carrying out plane reconstruction, namely back projection on acquired projection images Pj with different angles to each reconstruction plane Si, namely Si=Si+BP (Pj), wherein: BP is a back projection operation process, namely, according to an X-ray propagation path, mapping signals acquired by each pixel of the detector to a corresponding position of a reconstruction plane Si;

the superposition average refers to: the reconstructed images on the obtained Si planes are accumulated according to the respective pixel correspondence and then are subjected to arithmetic average;

the micro shooting means that: the radiation source and the detector are controlled to synchronously move in a small range around the center of the imaging object, and the moving range can be a space angle of-6 to 6 degrees; exposing and shooting are carried out simultaneously in the moving process;

the radius between the ray source and the circle center is 400 mm-600 mm; the radius between the detector and the circle center is 200 mm-300 mm;

the planar reconstruction refers to: filtering the images obtained by a plurality of micro shooting before reconstruction;

the X-ray projection optimization imaging specifically comprises the following steps:

step 1) performing micro-motion shooting around an object to be detected by controlling a ray source and a detector to obtain projection data P under each rotation angle _i ；

Step 2) dividing the measured object into a plurality of imaging planes S _i In a simulated 90 parallel beam imaging, each imaging plane S is due to the different distances from the source and detector in the 90 projection orientation _i With respective corresponding magnification ratios for projection data P _j Back projection to S _i A plane;

step 3) back-projecting the corrected image onto an imaging plane S _i The method specifically comprises the following steps: any X-ray in the cone beam passes through the imaging plane S _i Finally reach the detector P _j,(x,y) Position (x, y), where j is the j-th projection data, and calculating the (x, y) position of the detector on the imaging plane S under the projection angle of the corresponding deflection degree of the jog shooting according to the imaging geometric relation _i The position on the upper surface is (x _i ,y _i ) Correspondingly realize the imaging plane S _i Back projection onto:

Where N is the number of imaging planes.