CN115813415A - Method for determining position of collimator slot of CT machine, collimator and CT machine - Google Patents
Method for determining position of collimator slot of CT machine, collimator and CT machine Download PDFInfo
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- CN115813415A CN115813415A CN202211141999.2A CN202211141999A CN115813415A CN 115813415 A CN115813415 A CN 115813415A CN 202211141999 A CN202211141999 A CN 202211141999A CN 115813415 A CN115813415 A CN 115813415A
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- A—HUMAN NECESSITIES
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Abstract
The invention provides a method for determining the position of a collimator slot of a CT machine, which comprises the following steps: the X-ray source emits X-rays which form a plurality of projections on the detector channel array through the aperture; obtaining a first barycentric position G (n, m) of each projection in the direction of a row of the array of channels; obtaining a second barycentric position G according to the first barycentric positions G (n, m) of all the projections; based on the second gravity center position G and the target position Z target The difference between them yields a first deviation Δ Z, i.e. Δ Z = G-Z target (ii) a Determining the position Z of the collimator slot from the first deviation DeltaZ optimal . The invention can quickly and accurately determine the position of the collimator slot. The invention also provides a collimator of the CT machine and the CT machine.
Description
Technical Field
The invention relates to a method for determining the position of a collimator slot of a CT machine, in particular to a method for determining the position of the collimator slot of the CT machine in the field of image medical treatment, a collimator and the CT machine.
Background
A Computed Tomography (CT) system is provided with a bulb, a collimator and a detector on an X-ray path, and an X-ray focus in the bulb emits X-rays to hit the detector through the collimator. To ensure accuracy, the tube, collimator and detector should all be in a scan plane perpendicular to the direction of movement of the bed (Z-direction in fig. 3). However, due to manufacturing and assembly errors of the components, accurate positioning is very difficult. More importantly, as the scanning mode (e.g., voltage and rotation speed) changes or the anode temperature increases, the focal point of the bulb moves during the scanning process, which causes the collimator to further shift out of the preset target position. Many researchers have been trying to find solutions to the above-mentioned problems to reduce and avoid the impact on image quality.
Some prior art methods have been introduced in terms of focus stability, by adding a closed control loop to control the focus, stabilizing the focus position during scanning. This inevitably increases the complexity of the system and the cost of development and maintenance.
Therefore, a more widely used method is from the viewpoint of adjusting the position of the collimator. The collimator slot is adjusted to an optimal position to ensure that the detector is always symmetrically illuminated by X-rays from the focal spot of the tube. However, in order to find the optimal position of the slot, the collimator has to be moved over multiple exposures and some iterative calculations are performed. This method is time consuming and results are not stable.
Disclosure of Invention
The invention aims to provide a method for determining the position of a collimator slot of a CT machine, which can quickly and accurately determine the position of the collimator slot.
The invention provides a method for determining the position of a collimator slot of a CT machine. The CT machine includes: an X-ray source emitting X-rays, a collimator, and a detector; the collimator comprises a collimator slot plate, and the collimator slot plate is provided with a collimator slot and a hole; the detector is composed of q rows and m columns of channel arrays and has a preset target position Z to which X-rays are required to be irradiated target . The method for determining the position of the collimator slot of the CT machine comprises the following steps: the X-ray source emits X-rays which form a plurality of projections on the detector channel array through the aperture; obtaining a first barycentric position G (n, m) of each projection in the direction of a row of the array of channels; obtaining a second barycentric position G based on the first barycentric positions G (n, m) of all projections; based on the second gravity center position G and the target position Z target The difference between them yields a first deviation Δ Z, i.e. Δ Z = G-Z target (ii) a Determining collimator slot from first deviation azPosition Z of optimal 。
The invention provides a method for determining the position of a collimator slot of a CT machine, which forms a plurality of projections on a detector by X-rays penetrating through holes on a collimator slot plate, firstly determines a first gravity center position of each projection on a channel array of the detector along the row direction according to a light intensity signal of the projection received on the detector, then averages all the first gravity center positions to obtain a second gravity center position, namely can determine the deviation of all the projections and a preset target position, and can quickly and accurately determine the position of the collimator slot by utilizing the deviation. Then, the collimator slot plate can be moved according to the position of the collimator slot, and the collimator is adjusted to the optimal position, so that the deviation of the focus position along the Z direction under various scanning conditions is effectively compensated.
In an exemplary embodiment of the method of determining the position of the collimator slots of a CT machine, in the step of obtaining a first barycentric position G (n, m) per projection in the direction of the row of the array of channels, the first barycentric position G (n, m) is obtained by the following formula:
n is the number of projections formed on the channel array by the detector as an X-ray hits through the aperture, s1 is the background noise of the detector signal under the current scanning conditions, p m,q (n) is the intensity of the X-rays received by the detector.
In an exemplary embodiment of the method for determining the position of the collimator slot of a CT machine, a second center of gravity position G is obtained from the first center of gravity positions G (n, m) of all projections by the following formula: g = ∑ Σ n (∑ m G (n, m)/m)/n. The second barycentric position G is averaged over all the first barycentric positions G (n, m).
In an exemplary embodiment of the method for determining the position of a collimator slot of a CT machine, the position Z of the collimator slot is determined as a function of the first deviation Δ Z optimal In the step (2), first the hole position deviation Δ P is determined from the first deviation Δ Z, and then the position Z of the collimator slot is determined from the hole position deviation Δ P optimal . Wherein the hole position deviation Δ PObtained from the following equation:
wherein d is FC Is the distance from the X-ray source to the trough plate, d FD Is the distance from the X-ray source to the detector, z pitch Is the spacing of adjacent channels of the detector in the direction of the row arrangement. From the obtained deviation of the position of the centre of gravity of the projection on the detector from the target position, i.e. the first deviation deltaz, and the geometrical relationship between the bulb, the collimator and the detector, the deviation of the position of the aperture can be determined, and then the deviation of the collimator slot.
In an exemplary embodiment of the method for determining the position of a collimator slot of a CT machine, the position Z of the collimator slot is determined from the hole position deviation Δ P optimal In the step (2), the position Z of the collimator slot is determined from the hole position deviation Δ P by the following formula optimal ：Z optimal ＝Z initial + Δ P + D, wherein Z initial D is the distance between the center of the hole and the center line of the collimator slot, which is the initial position of the collimator slot. The position of the collimator slot, that is, the optimal position of the collimator under the current scanning condition, can be determined according to the deviation of the collimator slot, the original position of the collimator, and the geometric relationship between the center of the hole and the collimator slot.
Another object of the present invention is to provide a collimator for a CT machine. The collimator includes a collimator slot plate. The collimator slot plate has a collimator slot and an aperture. The optimal position of the slot is determined using the above-described aperture scan-based method, and the collimator slot allows X-rays to pass through while the CT machine is scanning a patient.
The invention also provides a CT machine. The CT machine includes an X-ray source emitting X-rays, the collimator described above, and a detector. The detector is composed of m rows and q rows of channel arrays and has preset target positions Z to which X-rays need to be irradiated through the collimator target . The CT machine provided by the invention has the advantages that the position of the collimator slot is quickly and accurately determined, and the position of the focal point under different scanning conditions is effectively compensatedThe image quality is ensured to the maximum extent.
Drawings
The following drawings are only schematic illustrations and explanations of the present invention, and do not limit the scope of the present invention.
Fig. 1 shows a schematic illustration of an exemplary embodiment of a CT machine according to the present invention.
FIG. 2 is a flow chart illustrating a method for determining the position of a collimator slot of a CT machine according to an exemplary embodiment of the present invention.
Fig. 3 is a schematic view of a collimator slot plate in a plane formed by the X and Z directions of the coordinate system shown in fig. 1.
Description of the reference symbols
10 X-ray source
30. Detector
24. Collimator slot
26. Hole(s)
Detailed Description
In order to more clearly understand the technical features, objects and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals indicate the same or structurally similar but functionally identical elements.
"exemplary" means "serving as an example, instance, or illustration" herein, and any illustration, embodiment, or steps described as "exemplary" herein should not be construed as a preferred or advantageous alternative.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product.
In this document, "first", "second", etc. do not mean their importance or order, etc., but merely mean that they are distinguished from each other so as to facilitate the description of the document.
Fig. 1 shows a schematic view of an exemplary embodiment of a CT machine according to the present invention. The invention relates to a method for determining the position of a collimator slot by using a CT machine.
The CT machine comprises an X-ray source 10, a collimator and a probeAnd a detector 30. X-rays can be emitted by the X-ray source 10. The collimator includes a collimator slot plate 20 having a collimator slot 24 and an aperture 26. The detector consists of an array of m columns of q rows of channels, as shown in fig. 1, and in one exemplary embodiment the detector has q rows of channels, from 1 Row (1)) to q rows (Row (q)) arranged from left to right in fig. 1, each Row having m channels. The detector 30 has a target position Z to which X-rays are irradiated with a predetermined value target . The detector 30 receives the X-rays emitted from the X-ray source 10, and the X-rays form projections on the detector 30, the positions of which can be represented by the intensity of the projections received by the detector. In the CT machine, there is a set of three-dimensional rectangular coordinates, the Z-direction is the arrangement direction of the rows (Row) of channel arrays of the detector, the channel arrays are shown arranged from 1 Row to q rows along the Z-direction, the Y-direction is the direction in which the X-ray source 10 has the shortest distance to the detector 30, and the X-direction is perpendicular to the Y-and Z-directions, respectively. During a CT scan, X-rays pass through the aperture to form a plurality of projections onto the channel array of the detector. The position of these projections is indicated by the intensity of the projections received by the array of channels in the detector.
FIG. 2 is a flow chart illustrating a method for determining the position of a collimator slot of a CT machine according to an exemplary embodiment of the present invention.
As shown in fig. 2, the method for determining the position of the collimator slot of the CT machine includes the following steps:
s1: x-rays are emitted by an X-ray source, and the X-rays form a plurality of projections on the channel array by hitting a detector through the through hole.
S2: obtaining a first barycentric position G (n, m) of each projection in the arrangement direction of the rows of the lane array; in one exemplary embodiment, the first barycentric position G (n, m) is obtained from the following formula from each of the scan intensity sinograms projected in the arrangement direction of the rows of the channel array:
where m is the probeThe number of columns of the channel array of the detector, q the number of rows of the channel array of the detector, n the number of projections formed on the channel array by the detector as an X-ray hit through the aperture, and s1 the background noise of the detector signal under the current scanning conditions. The first barycentric position G (n, m) may be represented by position coordinates projected in the direction of the rows of the channel array. s1 is the background noise of the detector signal under the current scanning conditions, if p m,q (n) ≧ s1, this indicates that the detector array location is hit by X-rays through the aperture, and the signal data can be used for the calculation. If p is m,q (n)<s1, this position is not hit by the X-ray passing through the aperture.
S3: a second center of gravity position G is obtained from the first center of gravity positions G (n, m) of all projections. In an exemplary embodiment, G is obtained by averaging all first barycentric positions G (n, m):
G＝∑ n (∑ m G(n,m)/m)/n。
s4: based on the second gravity center position G and the target position Z target The difference between them yields a first deviation Δ Z, i.e. Δ Z = G-Z target (ii) a In an exemplary embodiment, the hole position deviation Δ P is determined from the first deviation Δ Z, and is obtained by the following equation:
S5: obtaining the position Z of the collimator slot according to the hole position deviation delta P optimal . In an exemplary embodiment, the position Z of the collimator slot is determined from the hole position deviation Δ P by the following formula optimal ：
Z optimal ＝Z initial + Δ P + D, wherein Z initial The initial position of the collimator slot, D, is the distance between the center of the hole and the centerline of the collimator slot. Determined position Z of collimator slot optimal Is the best standard in the current scanning modeStraight slot position.
Fig. 3 is a schematic view of a collimator slot plate in a plane formed by the X and Z directions of the coordinate system shown in fig. 1. The collimator slot plate 20 has a collimator slot 24 and an aperture 26 with a distance D between the center of the aperture 26 and the centerline of the collimator slot 24.
The method for determining the position of the collimator slot of the CT machine can adjust the collimator to the optimal position, effectively compensate the movement of the focus along the Z direction under various scanning conditions, and ensure the image quality to a greater extent.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications such as combinations, divisions or repetitions of features, which do not depart from the technical spirit of the present invention, should be included in the scope of the present invention.
Claims (7)
1. A method of determining a position of a collimator slot of a CT machine, the CT machine comprising: an X-ray source emitting X-rays, a collimator, and a detector; the collimator includes a collimator slot plate having collimator slots and apertures; the detector is composed of a q-row and m-column channel array and has a preset target position Z to which X-rays need to be irradiated target (ii) a The method for determining the position of the collimator slot of the CT machine is characterized by comprising the following steps:
the X-ray source emits X-rays, and the X-rays pass through the hole to hit the detector to form a plurality of projections on the channel array;
obtaining a first barycentric position G (n, m) of each projection in the arrangement direction of the rows of the channel array;
obtaining a second barycentric position G from said first barycentric positions G (n, m) of all projections;
according to the second gravity center position G and the target position Z target The difference between them yields a first deviation Δ Z, i.e. Δ Z = G-Z target (ii) a Determining the position Z of the collimator slot from the first deviation Δ Z optimal 。
2. The method of determining the position of the collimator slot of the CT machine according to claim 1, wherein in the step of obtaining the first barycentric position G (n, m) of each projection in the arrangement direction of the rows of the channel array, the first barycentric position G (n, m) is obtained by the following formula:
n is the number of projections formed on the channel array by the detector when the X-ray passes through the hole, s1 is the background noise of the detector signal under the current scanning condition, and p m,q (n) is the intensity of the X-rays received by the detector.
3. The method of claim 1, wherein the step of obtaining a second barycentric position G based on said first barycentric position G (n, m) of all projections is obtained by the following formula: g = ∑ Σ n (∑ m G(n,m)/m)/n。
4. The method of determining the position of a collimator slot of a CT machine of claim 1 wherein the position Z of the collimator slot is determined from the first deviation az optimal First, a hole position deviation Δ P is determined from the first deviation Δ Z, the hole position deviation Δ P being obtained by the following equation:
wherein d is FC Is the distance from the X-ray source to the trough plate, d FD Is the distance from the X-ray source to the detector, and z pitch Is the pitch of adjacent channels of the detector in the arrangement direction of the rows;
then determining the position Z of the collimator slot according to the hole position deviation delta P optimal 。
5. Method for determining the position of a collimator slot of a CT machine as claimed in claim 4, characterized in that the position Z of the collimator slot is determined from the hole position deviation Δ P optimal In the step (b), the position Z of the collimator slot is determined from the hole position deviation Δ P by the following formula optimal ：
Z optimal ＝Z initial + Δ P + D, wherein Z initial D is the distance between the center of the hole and the center line of the collimator slot, which is the initial position of the collimator slot.
6. A collimator of a CT machine is characterized in that: the collimator includes a collimator slot plate having: a collimator slot allowing the passage of X-rays during a CT scan, and
an aperture for determining the position of the collimator slot using the method of any one of claims 1-5.
7. A CT machine, comprising:
an X-ray source emitting X-rays;
the collimator of claim 6; and
a detector consisting of m rows and q rows of channel arrays and having a preset target position Z to which the X-rays need to be irradiated through the collimator target 。
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211141999.2A CN115813415A (en) | 2022-09-20 | 2022-09-20 | Method for determining position of collimator slot of CT machine, collimator and CT machine |
| PCT/CN2023/112282 WO2024060869A1 (en) | 2022-09-20 | 2023-08-10 | Method for determining position of collimator slot of ct machine, collimator, and ct machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211141999.2A CN115813415A (en) | 2022-09-20 | 2022-09-20 | Method for determining position of collimator slot of CT machine, collimator and CT machine |
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| Publication Number | Publication Date |
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| CN115813415A true CN115813415A (en) | 2023-03-21 |
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| CN202211141999.2A Pending CN115813415A (en) | 2022-09-20 | 2022-09-20 | Method for determining position of collimator slot of CT machine, collimator and CT machine |
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| CN (1) | CN115813415A (en) |
| WO (1) | WO2024060869A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9417194B2 (en) * | 2013-08-16 | 2016-08-16 | General Electric Company | Assessment of focal spot characteristics |
| CN108937994A (en) * | 2017-05-27 | 2018-12-07 | 上海西门子医疗器械有限公司 | The method of the moving distance of x-ray system and determining collimation barricade |
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- 2022-09-20 CN CN202211141999.2A patent/CN115813415A/en active Pending
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