CN109738465A - A CT detection device and system - Google Patents

Abstract

The invention discloses a CT detection device and system, wherein the device includes a radiation source, a rotating disk and a CT detector; wherein, the CT detector includes N detection plates; the radiation source is arranged at one end of the rotating disk; The plate is arranged at the other end of the rotating disk, and the line connecting the imaging area center point of each detection plate and the ray source focus of the radiation source is perpendicular to the outer surface where the imaging area center point of each detection plate is located; The plate is the reference, and the rest of the detection plates are symmetrically distributed along the line connecting the center point of the imaging area of the central detection plate and the focal point of the ray source. From the perspective of reconstruction algorithm, the present invention realizes the problem of complete utilization of data based on the helical scanning T-FDK algorithm (herein referred to as ST-FDK), and realizes the problem of equipment miniaturization.

Description

A CT detection device and system

technical field

The invention belongs to the technical field of security inspection, and in particular relates to a CT detection device and system.

Background technique

Among the X-ray-based explosives inspection technologies, X-ray computed tomography imaging technology (referred to as "CT technology") is highly valued in the field of security inspection due to its own unique advantages. The only EDS (Explosive Detection System) security inspection equipment certified by the Federal Aviation Administration (FAA) in the United States is CT equipment, which shows the status of X-ray CT technology in the field of security inspection.

X-ray CT security inspection technology obtains the tomographic image of the scanned object by reconstructing the CT projection data, and realizes the identification of dangerous objects in the scanned object by analyzing the characteristic data in the tomographic image.

In traditional CT equipment, the distribution of detector devices is shown in Figure 1, where 1 is the ray source, 2 is the rotatable disk supporting the ray source and the detector, and 3 is the detector. Its characteristics are: the detectors are arranged continuously and distributed in the same standard circle with the target point of the ray source as the center, so that the dose range of the X-ray beam received by the detector components at the same time is similar, which can reduce the work of subsequent algorithm processing. At the same time, the spatial resolution of the center and the edge in the same tomographic image is similar, and the standard reconstruction algorithm of the standard arc detector can be used. However, the size of the equipment in such a layout will be relatively large, resulting in a much larger footprint than conventional security inspection machines, which is one of the key factors limiting the large-scale application of X-ray CT security inspection equipment in the field of security inspection, especially for hand luggage inspection. For CT equipment, the site is sensitive to the size of the equipment, so it is necessary to design miniaturized CT equipment, and the key point of miniaturization is the design of the optical path layout of the CT.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, a CT detection device and system are provided, and from the perspective of the reconstruction algorithm, the complete utilization of the data based on the helical scanning T-FDK algorithm (abbreviated as ST-FDK here) is realized. problem, and realize the problem of equipment miniaturization.

The object of the present invention is achieved through the following technical solutions: a CT detection device comprising: a radiation source, a rotating disk and a CT detector; wherein, the CT detector includes N detection plates; the radiation source is arranged at one end of the rotating disk; The detection plates are arranged at the other end of the rotating disk, and the line connecting the imaging area center point of each detection plate and the ray source focus of the radiation source is perpendicular to the outer surface where the imaging area center point of each detection plate is located; The central detection plate is used as the reference, and the rest of the detection plates are symmetrically distributed along the line connecting the center point of the imaging area of the central detection plate and the focal point of the ray source.

In the above CT detection device, the line connecting the center point of the imaging area of the central detection panel and the center point of the imaging area of each of the remaining detection panels is perpendicular to the line connecting the center point of the imaging area of each of the remaining detection panels and the focus of the ray source. .

In the above CT detection device, the angle γ1 between the line connecting the center point of the imaging area of the central detection plate and the focus of the ray source and the line connecting the center point of the imaging area of the second detection plate on the left and the focus _of the ray source is obtained by the following formula: :

Among them, β ₁ is the angle between the line connecting the left boundary point of the center detector and the ray source focus and the line connecting the center point of the imaging area of the center detector plate and the ray source focus, L is the width of the detector plate, and the center detector plate The adjacent left probe plate is defined as the second probe plate from the left.

In the above CT detection device, the angle γk between the line connecting the center point of the imaging area of the central detection plate and the focus of the ray source and the line connecting the center point of the imaging area of the _k -th detection plate on the left and the focus of the ray source is obtained by the following formula: :

Among them, β _k is the angle between the line connecting the left boundary point of the k-th detector on the left and the ray source focus and the line connecting the center point of the imaging area of the center detection plate and the ray source focus, k=2, 3, 4… ,

In the above CT detection device, the relationship between β _k and β _k-1 is as follows:

β _k =2*γ _k-1 -β _k-1 ,

Among them, β _k-1 is the angle between the line connecting the left boundary point of the k-1th detector on the left and the focus of the ray source and the line connecting the center point of the imaging area of the center detection plate and the focus of the ray source, γ _k-1 is the angle between the line connecting the center point of the imaging area of the central detection plate and the focus of the ray source and the line connecting the center point of the imaging area of the k-1th detector plate on the left and the focus of the ray source, k=2, 3, 4… ,

In the above CT detection device, the radiation source is a CT radiation source.

A CT system, comprising: any of the CT detection devices according to claims 1 to 6, a conveyor belt, a data processing computer, a conveyor belt motor, a slip ring motor and a motion control computer; wherein the CT detection device comprises a ray source, Rotating disk and CT detector; the ray source and CT detector are arranged on the rotating disk, the CT detector is connected with the data processing computer, the conveyor belt motor and the slip ring motor are connected with the motion control computer; the motion control computer controls the conveyor belt motor to drive the conveyor belt at a constant speed Movement, the motion control computer controls the slip ring motor to rotate at a constant speed; the detected object is placed on the transmission belt, the conveyor belt drives the detected object into the detection channel, and the rotating disk rotates around the conveyor belt at a constant speed; the radiation source emits radiation, and the CT detector receives the radiation from the CT radiation source The data processing computer completes the acquisition, storage and all data processing of CT projection data.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention proposes not only based on the compact structure design consideration, but also based on the complete utilization of projection data and improvement of the reconstruction algorithm. However, when the optical path layout proposed by the invention is adopted and the T-FDK reconstruction algorithm is used, the projection data collected by the detector can still be fully utilized. This conclusion is also applicable to the reconstruction algorithm of spiral orbit T-FDK, namely ST-FDK.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be considered limiting of the invention. Also, the same components are denoted by the same reference numerals throughout the drawings. In the attached image:

Fig. 1 is the schematic diagram of the detector device of the prior art;

2 is a schematic structural diagram of a CT detection device provided by an embodiment of the present invention;

3 is a schematic diagram of the positional relationship between N detection plates and the focus of a ray source provided by an embodiment of the present invention;

4 is a schematic diagram of fan beam rearrangement provided by an embodiment of the present invention;

5 is a schematic diagram of Cone-parallel rearrangement provided in an embodiment of the present invention;

6 is a top view of a rearrangement geometry provided by an embodiment of the present invention;

7 is a schematic structural diagram of a CT system provided by an embodiment of the present invention;

FIG. 8 is another schematic structural diagram of a CT detection apparatus provided by an embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be more thoroughly understood, and will fully convey the scope of the present disclosure to those skilled in the art. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

FIG. 2 is a schematic structural diagram of a CT detection device provided by an embodiment of the present invention; FIG. 3 is a schematic diagram of the positional relationship between N detection plates and a ray source focus provided by an embodiment of the present invention. As shown in FIG. 2 and FIG. 3 , the CT detection device includes: a radiation source 1 , a rotating disk 2 and a CT detector 3 .

The CT detector 3 includes N detection plates; each detection plate has its own corresponding center point 5 of the imaging area.

The radiation source 1 is arranged at one end of the rotating disk 2 . The rotating disk 2 includes a center of rotation 4 .

N detection plates are arranged at the other end of the rotating disk 2, and the line connecting the imaging area center point of each detection plate and the ray source focus 7 of the radiation source 1 is perpendicular to the outer surface where the imaging area center point of each detection plate is located ; Among them, with the central detection plate 8 as the benchmark, the remaining detection plates are symmetrically distributed along the line connecting the center point of the imaging area of the central detection plate 8 and the ray source focus 7 . Specifically, the N detection boards include the central detection board 8 and the rest of the detection boards, and the number of detection boards located on the left side of the central detection board 8 is The number of detection boards located on the right side of the central detection board 8 is

The line connecting the imaging area center point of the central detection panel 8 and the imaging area center point of each of the remaining detection panels is perpendicular to the corresponding connection line between the imaging area center point of each remaining detection panel and the ray source focus 7 . Specifically, as shown in FIG. 3 , the line connecting the center point of the imaging area of the center detection plate 8 and the center point of the imaging area of the second left detection plate 9 and the center point of the imaging area of the second left detection plate 9 is the same as the center point of the imaging area of the second left detection plate 9 The line connecting the ray source focus 7 is vertical. The line connecting the center point of the imaging area of the center detection plate 8 and the center point of the imaging area of the third left detection plate 10 is perpendicular to the line connecting the center point of the imaging area of the third left detection plate 10 and the ray source focus 7 . The line connecting the imaging area center point of the center detection plate 8 and the imaging area center point of the left k-th detection plate 11 is perpendicular to the connection line between the imaging area center point of the left k-th detection plate 11 and the ray source focus 7 . The line connecting the center point of the imaging area of the center detection plate 8 and the center point of the imaging area of the second right detection plate 12 is perpendicular to the line connecting the center point of the imaging area of the second right detection plate 12 and the ray source focus 7 . The line connecting the center point of the imaging area of the center detection plate 8 and the center point of the imaging area of the third right detection plate 13 is perpendicular to the line connecting the center point of the imaging area of the third right detection plate 13 and the ray source focus 7 . The line connecting the imaging area center point of the center detection plate 8 and the imaging area center point of the right k-th detection plate 14 is perpendicular to the connection line between the imaging area center point of the right k-th detection plate 14 and the ray source focus 7 .

The distance from the center point of the imaging area of each detector panel to the ray source focus 7 and the connection line between the center point of the imaging area of the detector panel and the ray source focus 1 and the connection between the center point of the imaging area of the center detection panel 8 and the ray source focus 7 The cosine of the angle between the lines (ie along the direction of the central beam 6) is proportional to the cosine.

As shown in FIG. 3 , the included angle γ1 between the line connecting the center point of the imaging area of the central detection panel 8 and the ray source focus 7 and the line connecting the center point of the imaging area of the second left-side detection panel 9 and the ray source focus ₇ Obtained by the following formula:

Among them, β ₁ is the angle between the line connecting the left boundary point of the center detector and the ray source focus 7 and the line connecting the center point of the imaging area of the center detector plate 8 and the ray source focus 7, L is the width of the detector plate, and The left detection plate adjacent to the central detection plate 8 is defined as the second detection plate 9 on the left.

The included angle γk between the line connecting the center point of the imaging area of the central detection panel 8 and the ray source focus 7 and the line connecting the center point of the imaging area of the _k -th detection panel 11 on the left and the ray source focus 7 is obtained by the following formula:

Among them, β _k is the angle between the line connecting the left boundary point of the k-th detector on the left and the ray source focus 7 and the line connecting the center point of the imaging area of the center detection plate 8 and the ray source focus 7, k=2,3 ,4…,

The relationship between β _k and β _k-1 is as follows:

β _k =2*γ _k-1 -β _k-1 ,

Among them, β _k-1 is the angle between the line connecting the left boundary point of the k-1 th detector on the left and the ray source focus 7 and the line connecting the center point of the imaging area of the central detection plate 8 and the ray source focus 7, γ _k-1 is the angle between the line connecting the center point of the imaging area of the central detection plate 8 and the ray source focus 7 and the line connecting the center point of the imaging area of the k-1th detector plate on the left and the ray source focus 7, k= 2,3,4…,

Spiral cone beam scanning is the most commonly used scanning method in commercial security CT, and the most commonly used reconstruction algorithm is still the analytical approximate reconstruction algorithm. Among them, the representative algorithms are the spiral FDK algorithm and the improved algorithm based on the FDK algorithm, which can be collectively referred to as the FDK-based algorithm. Under the condition of circular orbit scanning, T-FDK is a classic improved algorithm in FDK algorithm. The steps of T-FDK algorithm are to first rearrange the projection data from cone beam to oblique parallel beam, as shown in Figures 4 and 5 below. The rearranged data is projected onto the virtual detector at the center of rotation, like a tent. Figure 6 is a top view of the rearrangement geometry.

The process of cone beam rearrangement is similar to that of fan beam rearrangement into parallel beams, as shown in Figures 4 and 5. The rearrangement formula is:

(θ, t) are coordinates in parallel beam geometry, and (β, γ) are coordinates in fan beam and cone beam geometry. Set the ray source and detector to rotate counterclockwise around the object. For the projection of the fan beam, the projection relationship before and after rearrangement is as follows:

For the cone beam rearrangement process, the rearrangement formula is as follows:

It can be found that the relationship between the height on both sides of the "tent" and the middle height is:

where γ is the angle between the rearranged parallel beam and the center beam before rearrangement. As mentioned above, the rearranged data is projected onto a virtual detector at the center of rotation, like a tent. When using the filtered back-projection algorithm for reconstruction, the filtering direction is the horizontal direction, and part of the data needs to be discarded, which is not conducive to the improvement of the reconstructed image quality and the improvement of the image signal-to-noise ratio, in order to make full use of the projection data on the detection. The optical path layout of the detector designed in this patent is not on the standard arc, and the distance from the center point of the imaging area of each detector board to the focus of the ray source is the angle between the line connecting the center point of the imaging area of the detector board and the focus point of the ray source and the center beam is proportional to the cosine of . This is where the design idea of this patent lies.

Preferably, see Figure 3, a side view in the direction of movement of the conveyor. Let the angle between the left boundary of the central detection plate and the central beam be β ₁ , the angle between the left boundary of the second adjacent detection plate on the left and the central beam is β ₂ , and so on, the third adjacent left The angle between the left boundary of the block detection plate and the central beam is β ₃ , and the angle between the left boundary of the adjacent left k-th detection plate and the central beam is β _k . 7 is the focus of the ray source, 8 is the center detection board (here, the first detection board is agreed), 9 is the second detection board on the left, 10 is the third detection board on the left, and 11 is the kth detection board on the left board, 12 is the second detection board on the right, 13 is the third detection board on the right, and 14 is the k-th detection board on the right.

FIG. 7 is a schematic structural diagram of a CT system provided by an embodiment of the present invention. As shown in FIG. 7 , the CT system includes a CT detection device, a conveyor belt 50 , a data processing computer 90 , a conveyor belt motor 60 , a slip ring motor 80 and a motion control computer 70 . in,

The CT detection device includes a radiation source 1, a rotating disk 2 and a CT detector 3;

The ray source 1 and the CT detector 3 are arranged on the rotating disk 2, the CT detector 3 is connected to the data processing computer 90, and the conveyor belt motor 60 and the slip ring motor 80 are both connected to the motion control computer 70;

The motion control computer 70 controls the conveyor belt motor 60 to drive the conveyor belt to move at a uniform speed, and the motion control computer 70 controls the slip ring motor 80 to rotate at a uniform speed;

The detected object 40 is placed on the transmission belt 50, the conveyor belt 50 drives the detected object 40 into the detection channel, and the rotating disc 2 rotates around the conveyor belt at a constant speed;

The ray source 1 emits rays, the CT detector 3 receives ray photon signals from the CT ray source 1, and the data processing computer 90 completes the collection, storage and all data processing of CT projection data.

This embodiment proposes not only considering the compact structure design, but also the full utilization of projection data and improvement of the reconstruction algorithm. As is known to all, for the T-FDK reconstruction algorithm for circular orbits, some data will be discarded after data rearrangement. However, when the optical path layout proposed in this embodiment is adopted and the T-FDK reconstruction algorithm is used, the projection data collected by the detector can still be fully utilized. This conclusion can be extended to helical scan reconstruction.

Fig. 8 is another preferred embodiment. In the layout shown in Fig. 8, the central beam is located in the middle of the middle two detection plates. In this case, the total number of detection plates is even. Similarly, each detection plate The distance from the center point of the plate imaging area to the ray source focus is proportional to the cosine value of the included angle between the center point of the panel imaging area and the ray source focus and the center beam. Those skilled in the art should know that this arrangement is also within the protection scope of this patent.

The above-mentioned embodiments are only preferred specific implementations of the present invention, and general changes and substitutions made by those skilled in the art within the scope of the technical solutions of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A CT detection apparatus, comprising: the device comprises a ray source (1), a rotating disk (2) and a CT detector (3); wherein,

the CT detector (3) comprises N detection plates;

the ray source (1) is arranged at one end of the rotating disk (2);

the N detection plates are arranged at the other end of the rotating disk (2), and a connecting line of a central point of an imaging area of each detection plate and a ray source focus (7) of the ray source (1) is vertical to the outer surface where the central point of the imaging area of each detection plate is located; the central detection plate (8) is taken as a reference, and the rest detection plates are symmetrically distributed along the connecting line of the central point of the imaging area of the central detection plate (8) and the focal point (7) of the ray source.

2. The CT detection apparatus of claim 1, wherein: the connecting line of the central point of the imaging area of the central detection plate (8) and the central point of the imaging area of each of the other detection plates is vertical to the connecting line of the central point of the imaging area of each of the other corresponding detection plates and the focal point (7) of the ray source.

3. The CT detection apparatus of claim 1, wherein: the included angle gamma between the connecting line of the central point of the imaging area of the central detection plate (8) and the focal point (7) of the ray source and the connecting line of the central point of the imaging area of the second detection plate (9) on the left and the focal point (7) of the ray source₁Obtained by the following formula:

wherein, β₁The included angle between the connecting line of the left boundary point of the central detector and the ray source focal point (7) and the connecting line of the central point of the imaging area of the central detection plate (8) and the ray source focal point (7), L is the width dimension of the detection plate, and the left detection plate adjacent to the central detection plate (8) is defined as a second detection plate (9) on the left.

4. The CT detection apparatus of claim 1, wherein: an included angle gamma between a connecting line of a central point of an imaging area of the central detection plate (8) and the radiation source focal point (7) and a connecting line of a central point of an imaging area of the kth detection plate (11) on the left and the radiation source focal point (7)_kObtained by the following formula:

wherein, β_kThe connecting line of the left boundary point of the kth detector on the left and the ray source focal point (7) and the central point of the imaging area of the central detection plate (8)An included angle with the connecting line of the ray source focal point (7),

5. the CT detection device of claim 4, wherein β_kAnd β_k-1The following equation:

β_k＝2*γ_k-1-β_k-1，

wherein, β_k-1The included angle between the connecting line of the left boundary point of the kth-1 left detector and the ray source focal point (7) and the connecting line of the central point of the imaging area of the central detection plate (8) and the ray source focal point (7) is gamma_k-1Is an included angle between a connecting line of a central point of an imaging area of a central detection plate (8) and a focal point (7) of a ray source and a connecting line of a central point of an imaging area of a kth-1 th detection plate on the left and the focal point (7) of the ray source,

6. the CT detection apparatus of claim 1, wherein: the ray source (1) is a CT ray source.

7. A CT system, comprising: the CT detection device of any of claims 1 to 6, a conveyor belt (50), a data processing computer (90), a conveyor belt motor (60), a slip ring motor (80), and a motion control computer (70); wherein,

the CT detection device comprises a ray source (1), a rotating disk (2) and a CT detector (3);

the ray source (1) and the CT detector (3) are arranged on the rotating disk (2), the CT detector (3) is connected with a data processing computer (90), and the conveyer belt motor (60) and the slip ring motor (80) are both connected with the motion control computer (70);

the motion control computer (70) controls the conveyor belt motor (60) to drive the conveyor belt to move at a constant speed, and the motion control computer (70) controls the slip ring motor (80) to rotate at a constant speed;

the detected object (40) is placed on the transmission belt (50), the transmission belt (50) drives the detected object (40) to enter the detection channel, and the rotating disc (2) rotates around the transmission belt at a constant speed;

the ray source (1) emits rays, the CT detector (3) receives ray photon signals from the CT ray source (1), and the data processing computer (90) finishes the acquisition and storage of CT projection data and all data processing work.