A focal point adjustment system and method for a static CT

Abstract

The application discloses a focus adjusting system and method of static CT. The focus adjusting system comprises a ray source support installed on a rack and provided with a ray source ring, the ray source ring is in the shape of a ring and surrounded by a plurality of ray sources; a detector ring is arranged on the ray source support; an imaging object support is installed on one side of the ray source support and provided with an imaging object ring, the imaging object ring is in the shape of a ring and surrounded by a plurality of imaging objects, the plurality of imaging objects correspond to the plurality of ray sources one by one; a focus adjusting part comprises a plurality of focus adjusting units, the plurality of focus adjusting units are connected with the plurality of ray sources respectively to drive the corresponding ray sources to move back and forth; a controller is arranged on the rack and used for exposure control of the plurality of ray sources; the controller is also used for calculation of focus offset of each ray source; the controller is also used for control of movement of each focus adjusting unit to adjust the focus position of each ray source. According to the application, the geometric relationship between the theoretical focus position and the detector can be ensured to be accurate.

Description

Technical Field

[0001] This invention relates to a focus adjustment system for static CT, and also to a corresponding focus adjustment method, belonging to the field of computed tomography technology. Background Technology

[0002] The X-ray source of a static CT scanner consists of multiple X-ray sources arranged in a ring. The focal point of each X-ray source needs to be coplanar in the XY plane. However, due to the manufacturing error of approximately ±1.5mm in the X-ray source core, the focal point of the X-ray source in the installed static CT scanner may have a large deviation. This affects the geometric relationship between the X-ray source and components such as the beam limiter and detector, making it difficult to perform accurate calibration of the static CT scanner.

[0003] The alignment of the X-ray source focal spot with the detector at the theoretical center directly affects the quality of the reconstructed image. In some cases, static CT can use up to 24 X-ray sources, and it is necessary to ensure that the focal spot of each X-ray source coincides with the detector at the theoretical center, with the error controlled within ±1 pixel.

[0004] Chinese invention patent ZL 201711121001.1 discloses a geometric calibration device for a static cone-beam CT imaging system. This device includes several cold cathode X-ray tubes arranged linearly or in an arc to form a multi-beam X-ray source array, where each cold cathode X-ray tube serves as an X-ray emission source. A support frame has pre-reserved adjustment space along the X, Y, and Z axes, allowing the position of each cold cathode X-ray tube to be adjusted in each of the three directions (X, Y, or Z) after it is mounted on the support frame. By adjusting each cold cathode X-ray tube in the three directions (X, Y, or Z), precise calibration of the geometric position of each X-ray source is achieved, resulting in extremely high calibration accuracy.

[0005] However, although the above technical solutions can adjust the position of each X-ray source, they cannot find the focal offset of each X-ray source in the static CT system. Therefore, it is not easy to realize the physical adjustment after the focal position of the static CT system is offset, and thus it is impossible to guarantee the accuracy of the geometric relationship between the theoretical focal position and the detector. Summary of the Invention

[0006] The primary technical problem to be solved by this invention is to provide a focus adjustment system for static CT.

[0007] Another technical problem to be solved by the present invention is to provide a focus adjustment method for static CT.

[0008] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0009] According to a first aspect of the present invention, a focus adjustment system for static CT is provided, comprising:

[0010] A radiation source support is mounted on a frame, and a radiation source ring is mounted on the radiation source support. The radiation source ring is formed by multiple radiation sources arranged in a circular shape.

[0011] A detector ring is mounted on the radiation source support, and the axis of the detector ring coincides with the axis of the radiation source ring.

[0012] An imaging object support is installed on one side of the X-ray source support. An imaging object ring is installed on the imaging object support. The imaging object ring is formed by multiple imaging objects in a circular shape. The axis of the imaging object ring coincides with the axis of the detector ring. Each of the multiple imaging objects corresponds to one of the multiple X-ray sources, so that each X-ray source can emit X-rays toward the corresponding imaging object and form a projected image on the detector ring.

[0013] The focus adjustment unit includes multiple focus adjustment units, each of which is connected to a plurality of X-ray sources. Each focus adjustment unit drives the corresponding X-ray source to reciprocate along the axial direction of the detector ring.

[0014] A controller, mounted on the frame, is electrically connected to multiple X-ray sources to control the exposure of the multiple X-ray sources. The controller is also electrically connected to the detector ring to calculate the focal offset of each X-ray source based on the projected image of the detector ring. The controller is also electrically connected to the focal adjustment unit to control each focal adjustment unit to move the corresponding X-ray source along the axial direction of the detector ring based on the focal offset of each X-ray source, thereby adjusting the focal position of each X-ray source respectively.

[0015] Preferably, the focal offset of each X-ray source is calculated based on the projected image of the detector ring, specifically including:

[0016] The coordinates of the actual pixel points of each X-ray source in the preset spatial coordinate system are determined based on the projected image of the detector ring; wherein the preset spatial coordinate system is constructed with the theoretical focus as the origin, the axial direction of the detector ring as the Z-axis, the horizontal direction perpendicular to the Z-axis and passing through the origin as the X-axis, and the vertical direction perpendicular to the Z-axis and passing through the origin as the Y-axis.

[0017] The focal offset Z of each X-ray source is calculated using the following formula. 偏 ;

[0018] Z 偏 = (Actual pixels - Theoretical pixels) / (SID - SOD) * SOD * Pixel size;

[0019] The detector ring is composed of multiple pixels, each of which has corresponding coordinates in a preset spatial coordinate system; SID represents the dimension from the focal point of the X-ray source to the detector surface; SOD represents the radius of the X-ray source focal point ring.

[0020] Preferably, the focus adjustment unit specifically includes:

[0021] An adjustment seat is mounted on the radiation source support.

[0022] An adjusting screw is installed on the adjusting base and connected and fixed to the radiation source. The axis of the adjusting screw is parallel to the axis of the detector ring. Rotating the adjusting screw can drive the radiation source to reciprocate along the axis of the detector ring.

[0023] Preferably, the imaging ring includes a plurality of T-shaped prisms and a light-transmitting ring;

[0024] Multiple T-shaped prisms are evenly arranged around the axis of the X-ray source support on the side of the imaging object support facing the X-ray source support, and together form a ring. Each of the multiple T-shaped prisms corresponds to a multiple X-ray source. The light-transmitting ring is disposed on the side of the multiple T-shaped prisms away from the imaging object support for transmitting X-rays.

[0025] Preferably, the radiation source support is provided with a waist-shaped hole, the length direction of which is parallel to the axial direction of the detector ring;

[0026] The frame is provided with a guide pin, which is disposed in the waist-shaped hole so that the X-ray source support and the frame can move relative to each other within the range of motion of the waist-shaped hole, so as to adjust the position of the X-ray source support in the direction of the detector annular axis.

[0027] Preferably, the imaging object holder is detachably mounted on one side of the X-ray source holder.

[0028] Preferably, a positioning groove is provided on one side of the X-ray source bracket, and a positioning post is provided on the side of the imaging object bracket facing the X-ray source bracket, wherein the positioning post is inserted into or separated from the positioning groove.

[0029] According to a second aspect of the present invention, a focus adjustment method for static CT is provided, comprising the following steps:

[0030] Exposure is performed through a radiation source ring, so that each radiation source emits X-rays toward the corresponding imaging object and forms a projected image on the detector ring.

[0031] Projected images of each radiation source are acquired through the detector ring;

[0032] The controller acquires the projected images of each ray source and calculates the projection offset of each ray source.

[0033] Determine whether the projection offset of each radiation source exceeds the preset reasonable deviation range;

[0034] If the deviation is within the acceptable range, no focus adjustment is required. If the deviation is within the acceptable range, the controller will control the focus adjustment unit to move each of the X-ray sources to be adjusted along the detector ring axis according to the focus offset of each X-ray source to be adjusted. After focus adjustment, the X-ray sources will be exposed again to re-acquire the projection image of the adjusted X-ray sources until the projection offset of all X-ray sources does not exceed the preset reasonable deviation range.

[0035] Preferably, the exposure method of the X-ray source ring includes at least:

[0036] Multiple X-ray sources are exposed one by one in a preset order; or, at least two X-ray sources are exposed simultaneously and in a preset order.

[0037] Among them, the projected images of at least two X-ray sources exposed at the same time do not overlap.

[0038] Preferably, before the X-ray source ring is exposed, the imaging object holder with the imaging object ring is pre-installed on the X-ray source support; and after the focus is adjusted, the imaging object holder with the imaging object ring is removed from the X-ray source support.

[0039] Compared with the prior art, the present invention has the following technical effects:

[0040] 1. It can find the accurate system focus offset position of static CT, and then make physical adjustments to make multiple X-ray sources coplanar in the XY plane, thereby ensuring the accurate geometric relationship between the theoretical focus position and the detector.

[0041] 2. By setting up an imaging ring, multiple imaging objects are respectively associated with multiple X-ray sources, allowing for individual focus adjustment of each X-ray source. Furthermore, this imaging ring is detachable for repeated use.

[0042] 3. The theoretical projection position is based on the Z-axis center of the detector ring, which eliminates the need for adjustment of the detector ring in the Z-axis direction, thereby improving the convenience of installing and fixing the detector ring. Attached Figure Description

[0043] Figure 1 A schematic diagram illustrating the focus adjustment principle of a focus adjustment system for static CT provided in the first embodiment of the present invention;

[0044] Figure 2 for Figure 1 A structural diagram from another angle;

[0045] Figure 3 This is a schematic diagram of the combined structure of the frame and the radiation source support in the first embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of the combined structure of the imaging object support and the imaging object ring in the first embodiment of the present invention;

[0047] Figure 5 The flowchart illustrates a focus adjustment method for static CT scans according to a second embodiment of the present invention. Detailed Implementation

[0048] The technical content of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0049] First Embodiment

[0050] like Figures 1 to 3 As shown, the first embodiment of the present invention provides a focus adjustment system for static CT, including a gantry 10, a radiation source support 1, a detector ring 2, an imaging support 3, an imaging ring 4, a focus adjustment unit 5, and a controller.

[0051] Specifically, the X-ray source support 1 includes a base 11 and an annular body 12. The base 11 is mounted on a frame 10 and has an oblong hole 111 formed therein, the length of which is parallel to the axis of the annular body 12. A guide pin 110 is provided on the frame 10 and is disposed within the oblong hole 111, allowing the X-ray source support 1 and the frame 10 to move relative to each other within the range of motion of the oblong hole 111, thereby adjusting the position of the X-ray source support 1 along the axis of the annular body 12. Multiple X-ray sources 101 are mounted on the annular body 12, and the multiple X-ray sources 101 are arranged in a ring around the axis of the annular body 12.

[0052] The detector ring 2 is attached to the inner ring surface of the annular body 12, and the axis of the detector ring 2 coincides with the axis of the X-ray source ring for image detection.

[0053] like Figure 4 As shown, the imaging object holder 3 is mounted on one side of the X-ray source holder 1. Furthermore, a positioning post 31 is provided on the side of the imaging object holder 3 facing the X-ray source holder 1, and correspondingly, a positioning groove is provided on one side of the X-ray source holder 1. The positioning post 31 engages or disengages with the positioning groove to detachably mount the imaging object holder 3 onto the X-ray source holder 1. An imaging object ring 4 is mounted on the imaging object holder 3, as shown in the figure. Figure 4As shown, the imaging ring 4 includes multiple T-shaped prisms 41 and a light-transmitting ring 42. The T-shaped prisms 41 are made of metal and are evenly arranged around the axis of the detector ring 2 on the side of the imaging support 3 facing the X-ray source support 1, forming a circular ring. Each T-shaped prism 41 corresponds to one of the multiple X-ray sources 101. The light-transmitting ring 42 is circular and made of a material with high light transmittance. It is positioned on the side of the multiple T-shaped prisms 41 away from the imaging support 3 to transmit X-rays and support the multiple T-shaped prisms, ensuring that the T-shaped prisms are evenly installed within the light-transmitting ring 42. It is understood that in one embodiment of the present invention, multiple imaging objects can be formed using the multiple T-shaped prisms 41 and the light-transmitting ring 42, and each imaging object corresponds to one of the multiple X-ray sources 101, so that each X-ray source 101 can emit X-rays toward its corresponding imaging object and form a projected image on the detector ring 2.

[0054] In this embodiment, the focus adjustment unit 5 includes multiple focus adjustment units 51, each of which is connected to a plurality of X-ray sources 101. Each focus adjustment unit 51 drives its corresponding X-ray source 101 to reciprocate along the axial direction of the detector ring 2, thereby achieving focus adjustment of each X-ray source 101. Figure 3 As shown, in this embodiment, the focus adjustment unit 51 includes an adjustment seat 511 and an adjustment screw 512. The adjustment seat 511 is disposed on the X-ray source bracket 1; the adjustment screw 512 is mounted on the adjustment seat 511 and connected and fixed to the X-ray source 101. The axial direction of the adjustment screw 511 is parallel to the axial direction of the detector ring 2. By rotating the adjustment screw 512, the X-ray source 101 can be driven to reciprocate along the axial direction of the detector ring 2, thereby realizing the focus adjustment of the X-ray source 101. In addition, in one embodiment of the present invention, the adjustment screw 511 moves 0.5 mm for each revolution and 0.05 mm for each small division. The specific adjustment can be made according to the actual offset position of the focus of each X-ray source 101.

[0055] A controller is mounted on the rack 10 and is electrically connected to multiple X-ray sources 101 for exposure control. The controller is also electrically connected to the detector ring 2 to calculate the focal offset of each X-ray source 101 based on the projected image of the detector ring 2 according to a preset algorithm. Furthermore, the controller is electrically connected to a focal adjustment unit 5 to control each focal adjustment unit 51 to move the corresponding X-ray source 101 along the axial direction of the detector ring 2 based on the focal offset of each X-ray source 101, thereby adjusting the focal position of each X-ray source 101.

[0056] In the above embodiments, the focal offset of each radiation source is calculated in the following manner:

[0057] First, the coordinates of the actual pixels of each X-ray source 101 in a preset spatial coordinate system are determined based on the projected image of detector ring 2. This preset spatial coordinate system is constructed with the theoretical focal point as the origin, the axis of detector ring 2 as the Z-axis, the horizontal direction perpendicular to the Z-axis and passing through the origin as the X-axis, and the vertical direction perpendicular to the Z-axis and passing through the origin as the Y-axis. Then, the focal offset Z-axis of each X-ray source 101 is calculated using the following formula.

[0058] Z-bias = (actual pixels - theoretical pixels) / (SID - SOD) * SOD * pixel size;

[0059] The detector ring is composed of multiple pixels, each of which has corresponding coordinates in a preset spatial coordinate system; SID represents the dimension from the focal point of the X-ray source to the detector surface; SOD represents the radius of the X-ray source focal point ring.

[0060] Understandably, in practical use, this focus adjustment system first imports the projected images into a preset algorithm program to find the center point of each projected image; then, it checks the pixel position of the center point on detector ring 2 and uses a formula to find the offset position of each X-ray source 101; finally, by finding the accurate X-ray source focus offset position, it adjusts the X-ray source focus to the theoretically correct position. Thus, by finding the accurate system focus offset position in static CT, physical adjustment is achieved, ensuring that multiple X-ray sources are coplanar in the XY plane, thereby guaranteeing the accurate geometric relationship between the theoretical focus position and detector 2.

[0061] Second Embodiment

[0062] like Figure 5 As shown, based on the first embodiment, the second embodiment of the present invention also provides a focus adjustment method for static CT, specifically including steps S1 to S5:

[0063] S1: Exposure of X-ray source 101.

[0064] Specifically, exposure is performed through a radiation source ring, so that each radiation source 101 emits X-rays toward its corresponding imaging object, forming a projected image on the detector ring 2. In this embodiment, the exposure method of the radiation source ring includes at least: multiple radiation sources 101 are exposed one by one in a preset order; or at least two radiation sources are exposed simultaneously and sequentially in a preset order; wherein the projected images of the at least two simultaneously exposed radiation sources 101 do not overlap.

[0065] S2: Acquire projection images of each X-ray source 101 through detector ring 2.

[0066] S3: Calculate the projection offset of each ray source 101.

[0067] Specifically, the controller acquires the projected images of each X-ray source 101 to find the center point of each projected image; then, the pixel position of the center point on the detector ring 2 is checked, and the projection offset of each X-ray source 101 is found using the above formula.

[0068] S4: Determine whether the projection offset of each X-ray source 101 exceeds the preset reasonable deviation range.

[0069] Specifically, if the projection offset of the X-ray source 101 does not exceed the preset reasonable deviation range, no focus adjustment is required. Conversely, if it does exceed the range, the controller controls the focus adjustment unit 5 to move each X-ray source 101 along the axis of the detector ring 2 according to its focus offset, thereby adjusting the focus. After focus adjustment, the adjusted X-ray source 101 is re-exposed to re-acquire the projected image of the adjusted X-ray source 101 until the projection offset of all X-ray sources 101 does not exceed the preset reasonable deviation range.

[0070] S5: Remove the imaging object support 3.

[0071] Specifically, before exposure of the X-ray source ring, the imaging object holder 3 with the imaging object ring 4 is pre-installed on the X-ray source holder 1. After focus adjustment is completed, the imaging object holder 3 with the imaging object ring 4 is removed from the X-ray source holder 1. This allows the imaging object holder 3 with the imaging object ring 4 to be reused for focus adjustment of other static CT systems.

[0072] In summary, the static CT focus adjustment system and method provided by the embodiments of the present invention have the following beneficial effects:

[0073] 1. It can find the accurate system focus offset position of static CT, and then make physical adjustments to make multiple X-ray sources coplanar in the XY plane, thereby ensuring the accurate geometric relationship between the theoretical focus position and the detector.

[0074] 2. By setting up an imaging ring, multiple imaging objects are respectively associated with multiple X-ray sources, allowing for individual focus adjustment of each X-ray source. Furthermore, this imaging ring is detachable for repeated use.

[0075] 3. The theoretical projection position is based on the Z-axis center of the detector ring, which eliminates the need for adjustment of the detector ring in the Z-axis direction, thereby improving the convenience of installing and fixing the detector ring.

[0076] The focus adjustment system and method for static CT provided by this invention have been described in detail above. Any obvious modifications made by those skilled in the art without departing from the essence of this invention will constitute an infringement of the patent rights of this invention and will incur corresponding legal liability.

Claims

1. A focus adjustment system for static CT, characterized in that... include: A radiation source support is mounted on a frame, and a radiation source ring is mounted on the radiation source support. The radiation source ring is formed by multiple radiation sources arranged in a circular shape. A detector ring is mounted on the radiation source support, and the axis of the detector ring coincides with the axis of the radiation source ring. An imaging object holder is installed on one side of the X-ray source holder. An imaging object ring is installed on the imaging object holder. The imaging object ring is formed by multiple imaging objects arranged in a circular shape. The axis of the imaging object ring coincides with the axis of the detector ring. Each of the multiple imaging objects corresponds one-to-one with a multiple of the multiple radiation sources, so that each radiation source can emit X-rays toward the corresponding imaging object and form a projected image on the detector ring; wherein, the imaging object ring includes multiple T-shaped prisms and a light-transmitting ring; the multiple T-shaped prisms are evenly arranged around the axis of the radiation source support on the side of the imaging object support facing the radiation source support, and together form a ring shape, with each of the multiple T-shaped prisms corresponding one-to-one with a multiple of the radiation sources; the light-transmitting ring is disposed on the side of the multiple T-shaped prisms away from the imaging object support, so as to transmit X-rays; The focus adjustment unit includes multiple focus adjustment units, each of which is connected to a plurality of X-ray sources. Each focus adjustment unit drives the corresponding X-ray source to reciprocate along the axial direction of the detector ring. A controller, mounted on the frame, is electrically connected to multiple X-ray sources for exposure control of the sources. The controller is also electrically connected to the detector ring to calculate the focal offset of each X-ray source based on the projected image of the detector ring. Furthermore, the controller is electrically connected to the focal adjustment unit to control each focal adjustment unit to move its corresponding X-ray source along the axial direction of the detector ring based on the focal offset of each X-ray source, thereby adjusting the focal position of each X-ray source. Specifically, calculating the focal offset of each X-ray source based on the projected image of the detector ring includes: The coordinates of the actual pixel points of each X-ray source in the preset spatial coordinate system are determined based on the projected image of the detector ring; wherein the preset spatial coordinate system is constructed with the theoretical focus as the origin, the axial direction of the detector ring as the Z-axis, the horizontal direction perpendicular to the Z-axis and passing through the origin as the X-axis, and the vertical direction perpendicular to the Z-axis and passing through the origin as the Y-axis. The focal offset Z-off of each X-ray source is calculated using the following formula; Pixel size; The detector ring is composed of multiple pixels, each of which has corresponding coordinates in a preset spatial coordinate system; SID represents the dimension from the focal point of the X-ray source to the detector surface; SOD represents the radius of the X-ray source focal point ring.

2. The focus adjustment system as described in claim 1, characterized in that... The focus adjustment unit specifically includes: An adjustment seat is mounted on the radiation source support. An adjusting screw is installed on the adjusting base and connected and fixed to the radiation source. The axis of the adjusting screw is parallel to the axis of the detector ring. Rotating the adjusting screw can drive the radiation source to reciprocate along the axis of the detector ring.

3. The focus adjustment system as described in claim 1, characterized in that: The radiation source support is provided with a waist-shaped hole, and the length direction of the waist-shaped hole is parallel to the axial direction of the detector ring; The frame is provided with a guide pin, which is disposed in the waist-shaped hole so that the X-ray source support and the frame can move relative to each other within the range of motion of the waist-shaped hole, so as to adjust the position of the X-ray source support in the direction of the detector annular axis.

4. The focus adjustment system as described in claim 1, characterized in that: The imaging support is detachably mounted on one side of the X-ray source support.

5. The focus adjustment system as described in claim 4, characterized in that: A positioning groove is provided on one side of the X-ray source bracket, and a positioning post is provided on the side of the imaging object bracket facing the X-ray source bracket. The positioning post is inserted into or separated from the positioning groove.

6. A focus adjustment method for static CT, applied to the focus adjustment system as described in any one of claims 1-5, characterized in that, The focus adjustment method includes the following steps: Exposure is performed through a radiation source ring, so that each radiation source emits X-rays toward the corresponding imaging object and forms a projected image on the detector ring. Projected images of each radiation source are acquired through the detector ring; The controller acquires the projected images of each ray source and calculates the projection offset of each ray source. Determine whether the projection offset of each radiation source exceeds the preset reasonable deviation range; If the deviation is within the acceptable range, no focus adjustment is required. If the deviation is within the acceptable range, the controller will control the focus adjustment unit to move each of the X-ray sources to be adjusted along the detector ring axis according to the focus offset of each X-ray source to be adjusted. After focus adjustment, the X-ray sources will be exposed again to re-acquire the projection image of the adjusted X-ray sources until the projection offset of all X-ray sources does not exceed the preset reasonable deviation range.

7. The focus adjustment method as described in claim 6, characterized in that... The exposure methods of the X-ray source ring include at least: Multiple X-ray sources are exposed one by one in a preset order; or, at least two X-ray sources are exposed simultaneously and in a preset order. Among them, the projected images of at least two X-ray sources exposed at the same time do not overlap.

8. The focus adjustment method as described in claim 6, characterized in that: Before exposure of the X-ray source ring, the imaging object holder with the imaging object ring is pre-installed on the X-ray source support; and after the focus is adjusted, the imaging object holder with the imaging object ring is removed from the X-ray source support.

Images