Method for adjusting collimator, controller, collimator and CT machine

Abstract

The application provides an adjusting method for a collimator of a CT machine. The adjusting method for the collimator of the CT machine comprises the following steps in each X-ray working and stopping scanning cycle: a detecting step (S10) for judging whether X-rays are generated on an anode plate; if the detecting step (S10) detects X-rays, a controller calculates a Z-direction thermal offset amount of a slot plate at this time (S20), wherein α represents a current cycle; the controller drives the slot plate to move along the Z-direction by the thermal offset amount (S22); if the detecting step (S10) does not detect X-rays, the controller calculates a total Z-direction thermal offset amount of the slot plate at the end of this time (S30); the controller calculates a cooling displacement amount of the slot plate at this time according to a stopping time of the X-rays (S32); and the controller drives the slot plate to move (S34).

Description

Technical Field

[0001] This invention relates to a method for adjusting a collimator for a CT scanner, and more specifically to a method for adjusting a collimator for a CT scanner, a controller for the collimator, a collimator, and a CT scanner. Background Technology

[0002] In computed tomography (CT) scans, instability in the focal position of the X-ray tube can lead to decreased image quality and even image artifacts. There are several reasons for focal shift, but the primary cause is the thermal condition of the X-ray tube.

[0003] As is well known, during scanning, the anode plate of an X-ray tube expands due to heat, causing the focal point to shift in one direction along the Z-axis. After scanning stops, as the temperature decreases, the anode plate rotates and shifts in the opposite direction. This phenomenon is particularly pronounced in the Z-axis of a tubular tube. Without intervention, X-rays passing through the collimator (TCO) will deviate from the effective detector area, thus reducing image quality. Figure 1 As shown, the CT scanner includes an anode plate 10 for generating X-rays. The collimator for the CT scanner includes a slotted plate 20 and a controller 40. When the anode plate is heated and expands, the focal point 12 moves to 12' along the Z-axis in one direction, thus deflecting the X-rays when scanning the target 32 ​​on the scanning stage 30.

[0004] To address this issue, the most common method for compensating for focus shift is thermal z-control. It uses real-time data acquired by the detector to calculate the required movement distance of the slot plate, ensuring that the ray remains within the effective area of ​​the scanned target 32.

[0005] like Figure 2 As shown, the Z-axis offset in segment P represents the Z-axis offset of the slot plate during scanning. Since there is no X-ray irradiation during the scan stop period between the end of the previous scan and the start of the next scan, thermal Z-axis control is impossible. Therefore, when the scan stops, the slot plate has no Z-axis offset during the scan stop period. When the next scan begins, the actual focal position deviates significantly from the slot plate position, resulting in a decrease in image quality at the beginning of the scan. Summary of the Invention

[0006] The purpose of this invention is to provide a method for adjusting the collimator of a CT scanner, which can control the offset of the slot plate during the scanning stop phase and improve the image quality of the CT scanner.

[0007] This invention provides a collimator for a CT scanner. The CT scanner includes an anode plate. The collimator includes a slot plate and a controller. The collimator adjustment method for the CT scanner includes the following steps during each X-ray operation and shutdown scan cycle: a detection step to determine whether X-ray irradiation is generated from the anode plate; if the detection step detects X-rays, the controller calculates the Z-axis thermal offset of the slot plate during this scan. Where α represents the current cycle; the controller drives the slot plate to move a thermal offset along the Z direction; if no X-ray is detected in the detection step, the controller calculates the total thermal offset of the slot plate in the Z direction at the end of this scan. The controller calculates the cooling displacement of the slot plate at the time of X-ray cessation. The controller drives the slot plate to move.

[0008] The collimator adjustment method for CT scanners provided by this invention, through "learning control," allows the collimator to control its offset during the scanning stop phase based on the total offset of the previous scan and the time of scan stop. This minimizes large-scale movement of the collimator at the start and end of the scan, thereby reducing the risk of image quality degradation.

[0009] In one illustrative embodiment of the collimator adjustment method for a CT scanner, the cooling offset at the time of this stop... Total thermal offset for this scan The function f(ΔT) with respect to the current stopping time ΔTα α The difference is: This allows the use of a linear model to estimate the cooling offset when the scan stops, cools down, and then is repeated.

[0010] In another illustrative embodiment of the collimator adjustment method for a CT scanner, the function f(ΔT) of the current stop time... α f(ΔT) is a linear function, i.e.: α )=κ·ΔT α , where κ is the thermal coefficient of the anode plate. During the scan stop ΔT, the X-ray tube experiences cooling because no scan is being performed. Therefore, the focal spot position continuously drifts in the opposite direction of heating. Thus, a linear equation in units of time ΔT is established to estimate the required slot plate position before the next scan.

[0011] In another illustrative embodiment of the collimator adjustment method for a CT scanner, the following step is further included in each X-ray operation and stop scan cycle: comparing the cooling offset at the time of the current stop. The predetermined cooling position Z of the slot plate min If cooling offset Not less than the predetermined cooling position Z minThe controller drives the slot plate to move by a cooling offset. If cooling offset Less than the predetermined cooling position Z min The controller then drives the slot plate to move to the predetermined cooling position Z. min When the calculated slot plate offset exceeds the predetermined value, the offset changes linearly; when the calculated slot plate offset is less than the predetermined value, the slot plate offsets by the predetermined value.

[0012] In another illustrative embodiment of the collimator adjustment method for a CT scanner, the total thermal offset for this scan... Total cooling offset from the previous scan Thermal offset of this scan The sum is:

[0013] In another illustrative embodiment of the collimator adjustment method for a CT scanner, the thermal offset during this scan... This is the sum of the offsets of the slot plate moving successively during this scan, i.e.: Where n is the total number of times the slot plate moves during this scan. Therefore It can also be expressed as: Therefore, the thermal offset during the scan can be a gradient change.

[0014] In another illustrative embodiment of the collimator adjustment method for a CT scanner, the function f(ΔT) of the current stop time... α f(ΔT) is a linear function, i.e.: α )=κ·ΔT α , where κ is the thermal coefficient of the anode plate. Therefore, the thermal offset during the scan can change linearly.

[0015] In another illustrative embodiment of the collimator adjustment method for a CT scanner, the following step is further included in each X-ray operation and stop scan cycle: comparing the thermal offset calculated during the current scan. The predetermined thermal offset Z of the slot plate max If the calculated thermal offset Not greater than the predetermined thermal offset Z max The controller drives the slot plate to move by a thermal offset. If the calculated thermal offset Greater than the predetermined thermal offset Z max The controller then drives the slot plate to move by a predetermined thermal offset Z. max During the scanning process, the anode plate is heated. When the calculated offset of the slot plate does not exceed the predetermined value, the offset changes linearly. When the calculated offset of the slot plate is greater than the predetermined value, the slot plate offsets by the predetermined value.

[0016] The present invention also provides a controller for a collimator of a CT scanner, the controller including a control module for performing the above steps.

[0017] The present invention provides a collimator for a CT scanner, which includes a slot plate and the controller described above.

[0018] The present invention also provides a CT scanner that includes the collimator described above.

[0019] The controller, collimator, and CT scanner provided by this invention can control the offset of the slot plate during the scanning stop phase or simultaneously control the offset of the slot plate during the scanning phase based on the total offset of the previous scan and the time of stopping the scan, so that the slot plate does not jump significantly during the scanning or stopping of the CT scanner, and the image quality remains stable. Attached Figure Description

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 The diagram shows a prior art collimator used in CT scanners where the anode plate shifts in the Z direction.

[0022] Figure 2 This demonstrates how the Z-axis offset changes over time in existing methods for compensating for focus offset.

[0023] Figure 3 The diagram illustrates one embodiment of the collimator adjustment method for a CT scanner according to the present invention.

[0024] Figure 4 The diagram illustrates one embodiment of the collimator adjustment method for a CT scanner according to the present invention.

[0025] Figure 5 Showing according to Figure 3 The Z-axis offset changes over time in the collimator adjustment method for a CT scanner, as shown.

[0026] Figure 6 Showing according to Figure 4 The Z-axis offset changes over time in the collimator adjustment method for a CT scanner, as shown. Detailed Implementation

[0027] To provide a clearer understanding of the technical features, objectives, and effects of the invention, specific embodiments of the invention are now described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate components with the same or similar structures but the same function.

[0028] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0029] The various figures in this document are not strict mathematical and / or geometrical limitations, and also include errors that are understandable to those skilled in the art and permissible in manufacturing or use.

[0030] Figure 3 The diagram illustrates a schematic implementation of a method for adjusting the collimator of a CT scanner. Figure 3 As shown, the method for adjusting the collimator of a CT scanner includes the following steps in each X-ray scan cycle during operation and shutdown:

[0031] S10: Detection step, to determine whether X-rays are generated from the anode plate;

[0032] S20: If X-rays are detected in the detection step, the controller calculates the Z-axis thermal offset of the slot plate during this scan. Where α represents the current loop;

[0033] S22: Thermal offset of the controller-driven slot plate moving along the Z direction;

[0034] S30: If no X-rays are detected in the detection step (S10), the controller calculates the total thermal offset of the slot plate in the Z direction at the end of this scan.

[0035] S32: The controller calculates the cooling displacement of the slot plate at the time of X-ray cessation based on the cessation time of the X-ray. S34: The controller drives the slot plate to move.

[0036] Figure 4 The diagram illustrates a schematic implementation of a method for adjusting the collimator of a CT scanner. Figure 4 As shown, the method for adjusting the collimator of a CT scanner includes the following steps in each X-ray scan cycle during operation and shutdown:

[0037] S10: Detection step, to determine whether X-rays are generated from the anode plate;

[0038] S20: If X-rays are detected in the detection step, the controller calculates the Z-axis thermal offset of the slot plate during this scan. Where α represents the current loop;

[0039] S22: Thermal offset of the controller-driven slot plate moving along the Z direction;

[0040] S30: If no X-rays are detected in the detection step, the controller calculates the total thermal offset of the slot plate in the Z direction at the end of this scan. Total thermal offset of this scan Total cooling offset from the previous scan Thermal offset of this scan The sum is: Thermal offset of this scan This is the sum of the offsets of the slot plate moving successively during this scan, i.e.: Where: n is the total number of times the slot plate moves during this scan.

[0041] S32: The controller calculates the cooling displacement of the slot plate at the time of X-ray cessation based on the cessation time of the X-ray. Cooling offset at the time of this stop Total thermal offset for this scan The function f(ΔT) with respect to the current stopping time ΔTα α The difference is: The function of the current stopping time f(ΔT) α f(ΔT) is a linear function, i.e.: α )=κ·ΔT α , where κ is the thermal coefficient of the anode plate;

[0042] S341: Compare the cooling offset at the time of this stop The predetermined cooling position Z of the slot plate min ;

[0043] S342: If cooling offset Not less than the predetermined cooling position Z min The controller drives the slot plate to move by a cooling offset.

[0044] S344: If cooling offset Less than the predetermined cooling position Z min The controller then drives the slot plate to move to the predetermined cooling position Z. min .

[0045] Figure 5 Showing according to Figure 3 The diagram illustrates how the Z-axis offset changes over time in the collimator adjustment method for a CT scanner. (Example:) Figure 5 As shown, (a) shows the time of X-ray scanning or pausing. (b) is a graph showing the Z-axis offset over time. Figure 5 As shown, during the scanning stop time, the controller calculates the cooling displacement of the slot plate at the time of the stop based on the X-ray stop time. The offset is linear within the stopping time ΔT.

[0046] Figure 6 Showing according to Figure 4 The diagram illustrates the change in Z-axis offset over time in the collimator adjustment method for a CT scanner. The thermal offset amount during the current scan is shown in step S30. The controller can be used to determine the thermal coefficient κ of this scan. Hα And the scan time ΔT Hα The calculation shows that: Wherein: κ Hα It is determined by a lookup table stored in the controller. The Z-axis offset changes over time in this adjustment method as follows: Figure 6 As shown, (a) shows the time of X-ray scanning or stopping. (b) is a graph showing the Z-axis offset over time. Figure 5 As shown, the thermal offset during the scan time The offset is linear. During the scan stop time, the controller calculates the cooling displacement of the slot plate at the time of the X-ray stop, based on the X-ray stop time. The offset is linear within the stopping time ΔT.

[0047] The present invention also provides a controller for a collimator of a CT scanner, the controller including a control module for performing the above steps.

[0048] The present invention provides a collimator for a CT scanner, which includes a collimator slot and the aforementioned controller.

[0049] The present invention also provides a CT scanner that includes the collimator described above.

[0050] The controller, collimator, and CT scanner provided by this invention can control the offset of the slot plate during the scanning stop phase or simultaneously control the offset of the slot plate during the scanning phase based on the total offset of the previous scan and the time of stopping the scan, so that the slot plate does not jump significantly when the CT scanner is scanning or stopping, and the image quality remains stable.

[0051] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0052] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation schemes or modifications made without departing from the spirit of the present invention, such as combinations, divisions or repetitions of features, should be included within the scope of protection of the present invention.

Claims

1. A method for adjusting a collimator for a CT scanner, the CT scanner including an anode plate (10), the collimator including a slotted plate (20) and a controller (40), the adjustment method comprising the following steps in each X-ray operation and shutdown scanning cycle: S10: Detection step, to determine whether X-rays are generated from the anode plate; S20: If X-rays are detected in the detection step (S10), the controller calculates the Z-axis thermal offset of the slot plate during this scan. , where α represents the current loop; S22: The controller drives the slot plate to move the thermal offset along the Z direction by the specified amount; Its features are: S30: If no X-rays are detected in the detection step (S10), the controller calculates the total thermal offset of the slot plate in the Z direction at the end of this scan. ; S32: The controller calculates the cooling offset of the slot plate at the time of X-ray scattering based on the X-ray scattering time. ;and S34: The controller drives the slot plate to move; The cooling offset at the time of this stop The total thermal offset mentioned in this scan With this stop time α function The difference is: 。 2. The adjustment method as described in claim 1, characterized in that: The function of the current stop time It is a linear function, that is: ， in It is the thermal coefficient of the anode plate.

3. The adjustment method as described in claim 1, characterized in that... The adjustment method further includes the following steps in each X-ray operation and scan stop cycle: S341: Compare the cooling offset at the time of this stop. With the predetermined cooling position of the slot plate ; S342: If the cooling offset amount Not less than the predetermined cooling position The controller then drives the slot plate to move the cooling offset amount. ; S344: If the cooling offset Smaller than the predetermined cooling position The controller then drives the slot plate to move to the predetermined cooling position. .

4. The adjustment method as described in claim 1, characterized in that: The total thermal offset mentioned in this scan Total cooling offset from the previous scan Z-axis thermal offset as described in this scan The sum is: 。 5. The adjustment method as described in claim 4, characterized in that: The Z-axis thermal offset described in this scan This is the sum of the offsets of the slot plate moving successively during this scan, i.e.: ， Where: n is the total number of times the slot plate moves during this scan.

6. The adjustment method as described in claim 4, characterized in that: The Z-axis thermal offset described in this scan The controller is based on the thermal coefficient of this scan. and the time of this scan The calculation yields the following result: , in: It is determined by a lookup table stored in the controller.

7. The adjustment method as described in claim 6, characterized in that: The adjustment method further includes the following steps in each X-ray operation and scan stop cycle: Compare the total thermal offset calculated during this scan. The predetermined thermal offset of the slot plate ; If the calculated total thermal offset Not greater than the predetermined thermal offset The controller then drives the slot plate to move the total thermal offset. ; If the calculated total thermal offset Greater than the predetermined thermal offset The controller then drives the slot plate to move by the predetermined thermal offset. .

8. A controller for a collimator of a CT scanner, the controller (40) including a control module for performing the steps of claim 1.

9. A collimator for a CT scanner, comprising a slotted plate (20) and a controller (40) as claimed in claim 8.

10. A CT scanner comprising a collimator as described in claim 9.

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