An X-ray shielding assembly and a front collimator thereof

Abstract

The present invention discloses an X-ray shielding assembly and a front collimator thereof. The shielding assembly includes a pair of tungsten plates, a gap for X-rays to pass through is formed between the tungsten plates, the gap has a first plane area of ​​preset length surrounded by a hyperbola, the first plane area is used to trim the drum-shaped part of the X-ray projection projected onto the detector into a straight line; the two ends of the first plane area have a second plane area surrounded by a double straight line, the second plane area is used to trim the straight part of the X-ray projection projected onto the detector into a drum shape, so as to realize the auxiliary detector detection and control of the limit width of the X-ray projection after the beam is limited. Therefore, the shielding assembly can not only make the X-ray projection projected onto the detector rectangular, but also realize the auxiliary detector detection and control of the limit width of the X-ray projection after the beam is limited, so as to avoid the patient from bearing additional doses.

Description

Technical Field

[0001] The invention relates to an X-ray shielding assembly (shielding assembly for short), and also relates to a front collimator for CT comprising the shielding assembly, belonging to the technical field of computer tomography. Background Art

[0002] CT (Computed Tomography) is a medical diagnostic device widely used in the medical field. At present, a front collimator is generally set on CT to limit excess X-rays, reduce the dose to patients, reduce scattered rays, and improve image quality. The front collimator is achieved by placing two independent tungsten plates in parallel, with a parallel gap at both ends between the two tungsten plates for the required X-rays to pass through. Unnecessary X-rays will be blocked by the tungsten plates, and the X-rays that pass through will be projected onto an arc detector with the X-ray focus as the center. According to different scanning requirements, the width of the X-rays passing through is different, and the size of the gap between the two tungsten plates is also different. The size of the gap can be adjusted by the relative movement between the two tungsten plates.

[0003] At present, there are two main types of tungsten plate structures commonly used: one is a flat tungsten plate with a simple structure and a small space size; the other is an arc-shaped tungsten plate with the X-ray focus as the center (such as Figure 1 The arc-shaped tungsten plate 3) shown in the figure has a slightly complex structure and a relatively large spatial dimension. Figure 2 As shown in the figure, the X-ray projection produced by the flat tungsten plate is wide in the middle and narrow at both ends, which is a drum-shaped projection; Figure 3 As shown, the X-ray projection produced by the arc-shaped tungsten plate is a rectangular projection; it is generally considered that the rectangular projection is better and it does not expose the patient to additional doses.

[0004] However, when the maximum effective width of the detector needs to be fully utilized, the X-ray projection width is often greater than the width of the detector. In order to minimize the additional dose to the patient, we need to control the maximum width of the X-ray projection. Because there are a part of the detectors at both ends of the arc structure that do not participate in image reconstruction and only serve as reference channels, by using this part of the detectors and the characteristics of the convex part of the drum-shaped projection, when the other detectors can receive X-rays, but only the two ends of the reference detector in the width direction cannot receive them, we believe that the patient will not receive additional doses at this time. Rectangular projection cannot use this method to control the maximum width of the X-ray projection. Summary of the invention

[0005] The primary technical problem to be solved by the present invention is to provide an X-ray shielding component.

[0006] Another technical problem to be solved by the present invention is to provide a front collimator including the above-mentioned X-ray shielding assembly.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] According to a first aspect of an embodiment of the present invention, there is provided an X-ray shielding assembly, comprising a pair of tungsten plates, a gap for X-rays to pass through formed between the tungsten plates, the gap having a first plane area of ​​a preset length surrounded by a hyperbola, the first plane area being used to trim a drum-shaped portion of the X-ray projection projected onto the detector into a straight line; both ends of the first plane area have a second plane area surrounded by a double straight line, the second plane area being used to trim the straight portion of the X-ray projection projected onto the detector into a drum shape, so as to assist the detector in detecting and controlling the maximum width of the X-ray projection after beam limiting.

[0009] Preferably, the tungsten plate is a flat tungsten plate.

[0010] Preferably, each of the flat tungsten plates has a shielding end surface with the same shape and size.

[0011] Preferably, the middle of the shielding end surface has an outwardly protruding arc surface of a preset length, and both ends of the shielding end surface have straight planes.

[0012] Preferably, the flat-plate tungsten plates are placed in parallel, and the shielding end surface of one of the flat-plate tungsten plates is aligned with the shielding end surface of another of the flat-plate tungsten plates.

[0013] Preferably, the first plane region is formed between the arc-shaped surfaces of the flat tungsten plates, and the second plane region is formed between the planes of the flat tungsten plates.

[0014] Preferably, the preset length of the arc surface is expressed as:

[0015] L'=2*tg(β / 2*L min

[0016] Among them, L min represents the minimum distance from the focus of the X-ray to the edge of the gap between the two flat tungsten plates, and β represents the range of the detector arc angle corresponding to the maximum field angle of the computed tomography scanner.

[0017] Preferably, after the X-rays pass through the first plane area, the X-ray projection widths projected onto the detector are the same.

[0018] Preferably, the X-ray projection width is expressed as:

[0019] D n =S n *Rn / L n

[0020] Among them, S n Indicates the gap width at a certain position between two flat tungsten plates, R n Indicates the distance from the focus of the X-ray to a certain position on the arc edge of the arc detector, L n Indicates the distance from the focus of the X-ray to a certain edge position of the slit.

[0021] According to a second aspect of an embodiment of the present invention, there is provided a front collimator including the above-mentioned X-ray shielding assembly.

[0022] The shielding assembly provided by the present invention, by setting a shielding end face on a flat tungsten plate and forming a gap having a first plane area and a second plane area between the two shielding end faces, can not only make the X-ray projection projected onto the effective imaging field of view of the detector rectangular, but also can realize the auxiliary detector detection and control of the limit width of the X-ray projection after the beam is limited, so as to avoid the patient from receiving an additional dose. In addition, the shielding assembly can save the material for making the tungsten plate to the greatest extent, so that the shielding assembly has the characteristics of simple structure, small space occupation, low cost, light weight, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the use of an existing arc-shaped tungsten plate in combination with a detector;

[0024] Figure 2 Schematic diagram of the drum-shaped projection produced by the flat tungsten plate on the detector;

[0025] Figure 3 Schematic diagram of the rectangular projection produced by the arc-shaped tungsten plate on the detector;

[0026] Figure 4 This is a schematic diagram of the structure of the shielding assembly provided by the present invention;

[0027] Figure 5 A schematic diagram of an X-ray projection generated on a detector by a shielding assembly provided by the present invention;

[0028] Figure 6 A front view of the shielding assembly provided by the present invention in combination with a detector;

[0029] Figure 7 A side view of the shielding assembly provided by the present invention in combination with a detector. DETAILED DESCRIPTION

[0030] The technical content of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0031] In the existing shielding assembly of the front collimator, if the shielding assembly adopts a flat tungsten plate, then when the projection width of the X-ray after being limited is smaller than the width of the arc detector (hereinafter referred to as the detector), the projection of the X-ray on the effective imaging field of view of the detector after passing through the gap between the two flat tungsten plates is a drum shape, and the reference channels at both ends of the detector (such as Figure 6 The reference channel 5 shown does not participate in image reconstruction, while the other parts of the detector (imaging field of view) are used for image reconstruction. Therefore, the drum-shaped part of the X-ray projection of the flat tungsten plate on the effective imaging field of view of the detector will exceed the imaging field of view of the detector, causing the patient to bear an additional dose (radiation); if the shielding component uses an arc-shaped tungsten plate, then when the maximum effective width of the detector needs to be fully utilized, the width of the X-ray projection after beam limiting is often required to be greater than the width of the detector. At this time, it is difficult to use the reference channels at both ends of the detector to determine whether the opening of the front collimator (beam limiter) (the gap between the two arc-shaped tungsten plates) is close to the limit, that is, it is difficult to determine whether the width of the X-ray projection after beam limiting matches the maximum effective width of the detector, which will result in excess X-rays exceeding the imaging field of view of the detector, causing the patient to bear an additional dose (radiation).

[0032] Therefore, in order to solve the above problems existing in the two shielding components of the existing front collimator, the present invention provides a new type of X-ray shielding component. Figure 4 As shown, the shielding assembly includes a pair of tungsten plates 1, a gap 2 for X-rays to pass through is formed between the pair of tungsten plates 1, and the gap 2 has a first plane area 201 of a preset length surrounded by a hyperbola, and the first plane area 201 is used to trim the drum-shaped part of the X-ray projection projected onto the detector (referring to the effective imaging field of view of the detector) into a straight line; at both ends of the first plane area 201, there are second plane areas 202 surrounded by double straight lines, and the second plane area 202 is used to trim the drum-shaped part of the X-ray projection projected onto the detector (referring to the effective imaging field of view of the detector) into a straight line. Figure 6 The straight portion of the X-ray projection on the arc-shaped detector 4 (referring to the effective imaging field of view of the detector) is trimmed into a drum shape to achieve auxiliary detector detection and control of the maximum width of the X-ray projection after beam limiting. That is, when the maximum effective width of the detector needs to be fully utilized, the reference channel of the detector (such as Figure 6 The reference channel 5) shown detects and determines whether the width of the X-ray projection after beam limiting matches the maximum effective width of the detector to avoid the patient from receiving additional dose (radiation).

[0033] Specifically, Figure 4As shown, each tungsten plate 1 in the shielding assembly can be a flat tungsten plate. Each flat tungsten plate has a shielding end face, and the shielding end faces of each flat tungsten plate are the same in shape and size. Each shielding end face has an outwardly protruding arc surface 101 of a preset length in the middle, and each shielding end face has a straight plane 102 at both ends; each flat tungsten plate is placed in parallel, and the shielding end face of one flat tungsten plate is aligned with the shielding end face of another flat tungsten plate. At this time, a first plane area 201 is formed between the arc surfaces 101 of the shielding end faces of the two flat tungsten plates, and a second plane area 202 is formed between the planes 102 of the shielding end faces of the two flat tungsten plates. As shown Figure 5 As shown, the curved surface 101 of the shielding end surface of the two flat tungsten plates can be used to trim the drum-shaped portion of the X-ray projection that passes through the first plane area 201 between the two curved surfaces 101 (the gap between the two curved surfaces 101) and is projected onto the detector (referring to the effective imaging field of view of the detector) into a straight line, so that the X-ray projection is located in the imaging field of view of the detector, thereby avoiding the drum-shaped portion of the X-ray projection exceeding the imaging field of the detector and causing the patient to be exposed to an additional dose; the plane 102 of the shielding end surface of the two flat tungsten plates can be used to trim the straight portion of the X-ray projection that passes through the second plane area 202 between the two planes 102 (the gap between the two planes 102) and is projected onto the detector (referring to the effective imaging field of view of the detector) into a drum shape, so as to assist the detector in detecting and controlling the maximum width of the X-ray projection after beam limiting, so that the projection width of the X-ray after beam limiting fits the maximum effective width of the detector, thereby avoiding redundant X-ray projection exceeding the imaging field of the detector and causing the patient to be exposed to an additional dose (radiation).

[0034] Since the distance between the shielding end faces of the two flat tungsten plates directly affects the size of the gap 1, the two flat tungsten plates can be controlled to move toward each other according to actual conditions to adjust the size of the gap 1 formed between the two flat tungsten plates so that the X-rays have different projection widths.

[0035] Among them, Figure 6 As shown, the length of the arc surface 101 of the shielding end surface of the two flat tungsten plates is equal to the distance L from the focus of the X-ray to the edge of the gap 2 between the two flat tungsten plates (the distance from the focus of the X-ray to the different edge positions of the gap 2 are L1, L2...L n , n is a positive integer), and the range of the detector 4 radian angle β corresponding to the maximum FOV (Field of Vision) of the CT (Computed Tomography) machine. Therefore, according to the trigonometric function relationship, the length of the arc surface 101 (such as Figure 4 shown).

[0036] L'=2*tg(β / 2*L min (1)

[0037] Among them, L min It represents the minimum distance from the focus of X-rays to the edge of the gap 2 between the two flat tungsten plates, and β represents the range of the detector arc angle β corresponding to the maximum FOV (Field of Vision) of CT.

[0038] like Figure 4 , Figure 6 and Figure 7 As shown in FIG. 1 , since the X-ray projection onto the arc detector 4 after passing through the first plane area 201 between the arc-shaped curved surfaces 101 of the two flat tungsten plates is rectangular, the projection width of the X-ray projected onto the arc detector 4 is the same. Assume that the distance L from the focus of the X-ray to the edge of the gap 2 between the two flat tungsten plates (the distances from the focus of the X-ray to different edge positions of the gap 2 are L1, L2, ... L n , n is a positive integer), the distance R from the focus to the arc edge of the arc detector 4 (the distances from the focus to the arc edge of the arc detector 4 at different positions are R1, R2…R n , n is a positive integer), the width of the gap 2 between the two flat tungsten plates is S (the widths of the gaps at different positions between the two flat tungsten plates are S1, S2…S n , n is a positive integer), the projection width of the X-ray passing through the slit 2 and projected onto the arc detector 4 is D (the projection widths of the X-ray passing through the slit 2 and projected onto the arc detector (referring to the effective imaging field of view of the arc detector) are D1, DS2…D n , n is a positive integer); according to the following formula,

[0039] L n / R n =S n / D n (2)

[0040] It can be obtained that the projection width of the X-ray passing through the gap 2 and projected onto the arc detector (referring to the effective imaging field of view of the arc detector) is expressed as:

[0041] D n =S n *R n / L n (3)

[0042] Since the X-rays include multiple X-ray beams, the projection width of the X-rays projected onto the arc detector (referring to the effective imaging field of view of the arc detector) after each beam passes through the first plane area 201 is the same, which is specifically expressed as:

[0043] S1*R1 / L1=S2*R2 / L2=…=S n *R n / L n (4)

[0044] When the width of the X-ray projection after beam limiting is smaller than the width of the detector, the curved surface 101 of the shielding end faces of the two flat tungsten plates can be used to trim the drum-shaped portion of the X-ray projection that passes through the first plane area 201 (the gap between the two curved surfaces 101) between the two curved surfaces 101 and is projected onto the detector (referring to the effective imaging field of view area of ​​the detector) into a straight line, so that the X-ray projection that passes through the shielding component and is projected onto the effective field of view of the detector is rectangular, thereby preventing the drum-shaped portion of the X-ray projection from exceeding the imaging field of the detector and causing the patient to be exposed to additional doses.

[0045] When the width of the X-ray projection after beam limiting is greater than the width of the detector, not only can the curved surface 101 of the shielding end faces of the two flat tungsten plates be used to trim the drum-shaped portion of the X-ray projection that passes through the first plane area 201 (the gap between the two curved surfaces 101) between the two curved surfaces 101 and is projected onto the detector (referring to the effective imaging field of view area of ​​the detector) into a straight line, so that the X-ray projection that passes through the shielding component and is projected onto the effective field of view angle of the detector is rectangular; the plane 102 of the shielding end faces of the two flat tungsten plates can also be used to trim the straight portion of the X-ray projection that passes through the second plane area 202 (the gap between the two planes 102) between the two planes 102 and is projected onto the detector (referring to the effective imaging field of view area of ​​the detector) into a drum shape. If the reference channels 5 at both ends of the detector (such as Figure 6 This indicates that the projection width of the limited X-rays matches the maximum effective width of the detector, thus avoiding excess X-ray projection beyond the imaging field of view of the detector, which would cause the patient to receive additional dose (radiation).

[0046] The shielding assembly provided by the present invention can not only make the X-ray projection projected onto the effective imaging field of the detector rectangular by setting a shielding end face on the flat tungsten plate, and forming a gap having a first plane area and a second plane area between the two shielding end faces, but also can realize the auxiliary detector detection and control of the limit width of the X-ray projection after the beam is limited, so as to avoid the patient from receiving an additional dose. In addition, the shielding assembly can save the material for making the tungsten plate to the greatest extent, so that the shielding assembly has the characteristics of simple structure, small space occupation, low cost, light weight, etc.

[0047] In addition, the present invention also provides a front collimator including the above-mentioned X-ray shielding assembly. The front collimator can be applied to any existing CT. Through the front collimator, the two flat tungsten plates can be controlled to move toward each other, so as to adjust the size of the gap 1 formed between the two flat tungsten plates, so that the X-rays have different projection widths. For example, the motor and code disk of the front collimator can be used to control the two flat tungsten plates to move toward each other, so as to adjust the size of the gap 1 formed between the two flat tungsten plates. Among them, the structure and principle of the front collimator and the shielding assembly will not be described one by one.

[0048] The above is a detailed description of the X-ray shielding assembly and the front collimator provided by the present invention. For those skilled in the art, any obvious changes made to it without departing from the essential spirit of the present invention will fall within the protection scope of the patent right of the present invention.

Claims

1. An X-ray shielding assembly, characterized in that The invention comprises a pair of tungsten plates, a gap for X-rays to pass through is formed between the tungsten plates, the gap has a first plane area of ​​preset length surrounded by a hyperbola, the first plane area is used to trim the drum-shaped part of the X-ray projection projected onto the detector into a straight line; the two ends of the first plane area have a second plane area surrounded by a double straight line, the second plane area is used to trim the straight part of the X-ray projection projected onto the detector into a drum shape, so as to assist the detector in detecting and controlling the maximum width of the X-ray projection after beam limiting.

2. The X-ray shielding assembly according to claim 1, characterized in that: The tungsten plate is a flat plate.

3. The X-ray shielding assembly according to claim 2, characterized in that: Each of the flat tungsten plates has a shielding end surface with the same shape and size.

4. The X-ray shielding assembly according to claim 3, characterized in that: The middle of the shielding end surface is provided with an outwardly protruding arc surface of a preset length, and both ends of the shielding end surface are provided with straight planes.

5. The X-ray shielding assembly according to claim 4, characterized in that: The flat-plate tungsten plates are placed in parallel, and the shielding end surface of one of the flat-plate tungsten plates is aligned with the shielding end surface of the other flat-plate tungsten plate.

6. The X-ray shielding assembly according to claim 5, characterized in that: The first plane region is formed between the arc-shaped surfaces of the flat tungsten plates, and the second plane region is formed between the planes of the flat tungsten plates.

7. The X-ray shielding assembly according to claim 4, characterized in that: The preset length of the arc surface is expressed as: L'=2*tg(β / 2)*L min Among them, L min represents the minimum distance from the focus of the X-ray to the edge of the gap between the two flat tungsten plates, and β represents the range of the detector arc angle corresponding to the maximum field angle of the computed tomography scanner.

8. The X-ray shielding assembly according to claim 1, characterized in that: The X-ray projection widths of the X-rays projected onto the detector after passing through the first plane area are the same.

9. The X-ray shielding assembly according to claim 8, characterized in that: The X-ray projection width is expressed as: D n =S n *R n / L n Among them, S n Indicates the gap width at a certain position between two flat tungsten plates, R n Indicates the distance from the focus of the X-ray to a certain position on the arc edge of the arc detector, L n Indicates the distance from the focus of the X-ray to a certain edge position of the slit.

10. A front collimator, characterized in that The invention comprises the X-ray shielding assembly as claimed in any one of claims 1 to 9.

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