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WO2020192265A1 - Ct设备的几何参数标定件及标定方法 - Google Patents

Ct设备的几何参数标定件及标定方法 Download PDF

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Publication number
WO2020192265A1
WO2020192265A1 PCT/CN2020/073219 CN2020073219W WO2020192265A1 WO 2020192265 A1 WO2020192265 A1 WO 2020192265A1 CN 2020073219 W CN2020073219 W CN 2020073219W WO 2020192265 A1 WO2020192265 A1 WO 2020192265A1
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WIPO (PCT)
Prior art keywords
calibration
wire
wires
unit
plane
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PCT/CN2020/073219
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English (en)
French (fr)
Inventor
陈志强
张丽
赵振华
孙运达
金鑫
梁午阳
Original Assignee
同方威视技术股份有限公司
清华大学
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Application filed by 同方威视技术股份有限公司, 清华大学 filed Critical 同方威视技术股份有限公司
Priority to US15/733,630 priority Critical patent/US11340177B2/en
Publication of WO2020192265A1 publication Critical patent/WO2020192265A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/20—Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
    • G01V5/22—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
    • G01V5/226—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays using tomography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]
    • A61B6/032—Transmission computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/58—Testing, adjusting or calibrating thereof
    • A61B6/582—Calibration
    • A61B6/583—Calibration using calibration phantoms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/58—Testing, adjusting or calibrating thereof
    • A61B6/582—Calibration
    • A61B6/585—Calibration of detector units
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00—Details of radiation-measuring instruments
    • G01T7/005—Details of radiation-measuring instruments calibration techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V13/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00

Definitions

  • the present disclosure relates to the technical field of security inspection, and in particular to a geometric parameter calibration piece of CT equipment and a calibration method for calibrating geometric parameters of CT equipment by using the above calibration piece.
  • CT computed tomography
  • most CT equipment uses spiral cone-beam scanning, that is, a single target light source and arc detector are installed on a circular slip ring, the slip ring is rotated to collect projection data from different angles, and then reconstructed by analytical methods 3D CT image.
  • This type of equipment usually has only a single scanning plane, the relative position of the optical machine target and the detector is fixed, and the system involves fewer geometric parameters.
  • the geometric errors of the device will cause structural distortion of the reconstructed image, inaccurate values, and ring artifacts.
  • static CT equipment using distributed light sources has also begun to be used in the field of security inspection.
  • the static CT equipment has a single or multiple scanning planes, each scanning plane contains multiple light source targets, the targets can be arranged in straight lines, arcs and other shapes; the detector is composed of multiple detector arms, a single detector The arm can have various shapes such as a straight line, a broken line, or an arc shape.
  • static CT non-slip ring equipment has a fixed position of the X light source and detector.
  • Multi-plane scanning is used to ensure the angular coverage of the rays, and it has the advantages of fast scanning speed and low noise. Due to the particularity of scanning geometry, static CT equipment usually uses an iterative reconstruction method to obtain 3D images.
  • This method does not require geometric arrangement to meet specific conditions, but the positions of the optical machine target and the detector crystal need to be accurately positioned.
  • the coordinate system also needs to be unified.
  • the distributed light source is larger in size and weight compared with the single target point light source, and the mechanical error of the installation will be correspondingly larger. Due to the wide range of light source target points, the overall geometric deviation of the light source usually causes the target point position to deviate seriously from the design value, and the offset distance and offset direction of each target point may be different from each other, resulting in deformation of the reconstructed object and reconstruction value Inaccurate, and affect the spatial resolution and substance identification of the equipment. In addition, there will be errors in the installation of the detector arm, so it is necessary to perform geometric correction of the equipment.
  • the purpose of the present disclosure is to solve at least one aspect of the above-mentioned problems and defects in the prior art.
  • a geometric parameter calibration piece of a CT device including at least one calibration unit, each of the calibration units includes a plurality of calibration wires, the plurality of calibration wires Arranged regularly in the same plane.
  • the calibration wire is in the shape of a straight line, a broken line or a circular arc.
  • each of the calibration units further includes a fixing member configured to fix the plurality of calibration wires.
  • the multiple calibration wires are directly fixed on the conveyor belt of the CT device or in the channel of the CT device.
  • the multiple calibration wires in the calibration unit are arranged at equal intervals.
  • the plurality of calibration wires are parallel or at an angle with the conveying direction of the conveyor belt of the CT device.
  • the at least one calibration unit includes a first calibration unit, and a plurality of calibration wires of the first calibration unit are arranged in a horizontal plane or a vertical plane parallel to the conveying direction of the conveyor belt of the CT equipment. cloth.
  • the at least one calibration unit further includes a second calibration unit, and the plane where the multiple calibration wires of the second calibration unit are located is perpendicular to the plane where the multiple calibration wires of the first calibration unit are located. of.
  • the at least one calibration unit further includes a third calibration unit, and the plane where the multiple calibration wires of the third calibration unit are located is perpendicular to the plane where the multiple calibration wires of the first calibration unit are located. , And the second calibration unit and the third calibration unit are respectively located at two ends of the first calibration unit in a direction perpendicular to the conveying direction of the conveyor belt.
  • the calibration wire is cylindrical.
  • the diameter of the calibration wire is 0.5mm-5mm.
  • a method for calibrating the geometric parameters of a CT device by using the geometric parameter calibration piece according to the above-mentioned CT device including the following steps:
  • S2 Scan the calibration piece, and extract at least one set of projection slices containing the projection of the calibration wire on the scanning plane;
  • S5 Use the position matching algorithm to match the position of the centroid of the calibration wire obtained by S4 with the theoretical position calculated by S1, and then correct the position of the centroid of the calibration wire obtained by S4;
  • step S2 when there are multiple scanning planes, in step S2, at least one set of projection slices containing the projection of the calibration wire is extracted from each scanning plane, and the projection slices extracted by different scanning planes correspond to the calibration piece The same slice position; after step S6, the following steps are also included:
  • S7 Repeat S3 to S6 for each scanning plane to obtain the geometrical parameters of the detector and the position of the centroid of the calibration wire for each scanning plane;
  • Fig. 1 is a schematic structural diagram of a geometric parameter calibration piece of a CT device according to an exemplary embodiment of the present disclosure.
  • Fig. 2 is a schematic structural diagram of a geometric parameter calibration piece of a CT device according to another exemplary embodiment of the present disclosure.
  • Fig. 3 is a schematic structural diagram of a geometric parameter calibration piece of a CT device according to another exemplary embodiment of the present disclosure.
  • FIG. 4 is a schematic structural diagram of a geometric parameter calibration member of a CT device according to another exemplary embodiment of the present disclosure.
  • Fig. 5 is a flowchart of a method for calibrating geometric parameters of a CT device according to an exemplary embodiment of the present disclosure.
  • Fig. 6 is another flowchart of a geometric parameter calibration method of a CT device according to an exemplary embodiment of the present disclosure.
  • a geometric parameter calibration piece of CT equipment which includes at least one calibration unit, and each calibration unit includes multiple calibration wires, and the multiple calibration wires are in the same Arranged regularly in the plane.
  • Fig. 1 is a schematic structural diagram of a geometric parameter calibration piece of a CT device according to an exemplary embodiment of the present disclosure.
  • the geometric parameter calibration member of the CT equipment includes a calibration unit 10, and the calibration unit 10 includes a plurality of calibration wires 2 and a fixing member 1.
  • the multiple calibration wires 2 are regularly arranged in a horizontal plane parallel to the conveying direction of the conveyor belt.
  • the calibration wire 2 is usually made of a highly absorbent material, such as metal.
  • the calibration wire 2 may be flexible (for example, steel wire, etc.) or rigid (for example, steel rod, etc.).
  • Each calibration wire 2 has a linear shape, and the cross-sectional shape of the calibration wire 2 includes but is not limited to a cylindrical shape, and its diameter may be, for example, 0.5 mm-5 mm.
  • the fixing member 1 is configured to fix the multiple calibration wires 2 to ensure that the positions of the calibration wires 2 are fixed, so that the relative positions between the different calibration wires 2 conform to the theoretical design values.
  • the fixing member 1 may be made of a low-absorption material.
  • the calibration wire shown in this embodiment has a linear shape
  • the calibration wire 2 may also be in the shape of a broken line or a circular arc. Or other regular shapes.
  • the calibration wire 2 can also be directly fixed on the conveyor belt of the CT device or in the channel of the CT device.
  • the multiple calibration wires 2 in the calibration unit 10 are arranged parallel to each other and arranged at equal intervals to facilitate subsequent calculations.
  • the multiple calibration wires 2 are at an angle with the conveying direction of the conveyor belt of the CT device.
  • the multiple calibration wires 2 in the calibration unit 10 may also be parallel to the conveying direction of the conveyor belt.
  • Fig. 2 is a schematic structural diagram of a geometric parameter calibration piece of a CT device according to another exemplary embodiment of the present disclosure.
  • the multiple calibration wires 2 in the calibration unit 10 are parallel to each other and are arranged at equal intervals in a vertical plane parallel to the conveying direction of the conveyor belt of the CT equipment (shown by the arrow in Fig. 2).
  • the calibration wire 2 is at an angle with the conveying direction of the conveyor belt.
  • Fig. 3 is a schematic structural diagram of a geometric parameter calibration piece of a CT device according to another exemplary embodiment of the present disclosure.
  • the calibration element includes two calibration units: a first calibration unit 11 and a second calibration unit 12, wherein the first calibration unit 11 and the second calibration unit 12 each include a plurality of calibration wires 2 and a fixing member 1.
  • the multiple calibration wires 2 are arranged regularly, and each calibration wire 2 is linear.
  • the fixing member 1 is configured to fix the plurality of calibration wires 2.
  • the multiple calibration wires 2 in the first calibration unit 11 are arranged at equal intervals in a horizontal plane parallel to the conveying direction of the conveyor belt of the CT equipment (shown by the arrow in FIG. 3).
  • the plane where the multiple calibration wires 2 of the second calibration unit 12 are located is perpendicular to the plane where the multiple calibration wires 2 of the first calibration unit 11 are located, so that the entire calibration piece is L-shaped.
  • Fig. 4 is a schematic structural diagram of a geometric parameter calibration member of a CT device according to another exemplary embodiment of the present disclosure.
  • the calibration piece includes three calibration units: a first calibration unit 11, a second calibration unit 12, and a third calibration unit 13, wherein the first calibration unit 11, the second calibration unit 12 and the third calibration unit 13 each includes a plurality of calibration wires 2 and a fixing member 1, the plurality of calibration wires 2 are arranged regularly, and each of the calibration wires 2 is linear; the fixing member 1 is configured to fix the plurality of calibration wires 2.
  • the multiple calibration wires 2 in the first calibration unit 11 are arranged at equal intervals in a horizontal plane parallel to the conveying direction of the conveyor belt of the CT equipment (as shown by the arrows in FIG. 4).
  • the plane where the multiple calibration wires 2 of the second calibration unit 12 are located is perpendicular to the plane where the multiple calibration wires 2 of the first calibration unit 11 are located.
  • the plane on which the multiple calibration wires 2 of the calibration unit 11 are located is vertical, and the second calibration unit 11 and the third calibration unit 13 are respectively located at both ends of the first calibration unit 11 in a direction perpendicular to the conveying direction of the conveyor belt to Make the entire calibration piece U-shaped.
  • the present disclosure also provides a calibration method for calibrating the geometric parameters of CT equipment by using the above calibration element, which includes the following steps:
  • S2 Scan the calibration piece, extract the projection slice containing the projection of the calibration wire 2 in the scanning plane, specifically, place the calibration piece on the transmission belt of the CT equipment to scan the calibration piece.
  • the transmission belt runs at low speed to detect the calibration piece
  • the starting position ensures that the projections acquired by different scanning planes correspond to the projection slices at the same position of the calibration piece.
  • each scanning plane can extract, for example, three or more projection slices at equal intervals.
  • S3 Use an image processing method to obtain the position of the centroid of the calibration wire 2 on each projection slice. Due to the limitation of the crystal size of the detector, the detection accuracy of the position of the centroid of the calibration wire 2 is half the crystal width. Assuming that the calibration piece contains N calibration wires 2, a total of M groups of projection slices are collected. Due to the movement of the conveyor belt, the position of the centroid of the calibration wire 2 of each projection slice is different, so each scanning plane package collects M*N calibrations Wire projection data. If the target point k is beamed, the crystal mark of the true projection of the centroid of the calibration wire m on the plane of the detector is marked as
  • S4 For a single calibration wire m in the scanning plane, using the optical machine as the reference system, according to the intersection of the target point and the center of mass line of the calibration wire m and the detector, and the calibration wire m obtained in S3 The position of the centroid of, establishes an optimization model about the detector parameters and the position of the calibration wire, and solves the optimization model to obtain the positions of all the calibration wires in the scanning plane.
  • the geometric parameters related to the detector are related to the arrangement of the detector crystals. For example, a linear detector is determined by the starting position of the detector and the crystal arrangement direction, and an arc detector is determined by the center, radius and starting angle.
  • the parameters of the detector are denoted as (y, d), where y is the starting position of the detector and d is the direction vector of the detector crystal arrangement.
  • the linear equation of the detector is recorded as L(y, d), and the crystal size is recorded as ⁇ .
  • the position of the calibration wire m is denoted as x m
  • the position of the target point k is denoted as z k
  • the connection line between the calibration wire and the target is denoted as L(x m , z k ).
  • S5 Use a position matching algorithm to match the position of the centroid of the calibration wire m obtained by S4 with the theoretical position calculated by S1, and then correct the position of the centroid of the calibration wire m obtained by S4. Since both S3 and S4 have errors, and the positioning posture of the calibration piece is uncertain, the position of the centroid of the calibration wire m obtained by S4 is deviated from the theoretical position calculated by S1. The position of the centroid of the calibration wire calculated by S4 through the position matching algorithm And the theoretical position calculated by S1 Perform registration and then Perform calibration to obtain the final position of the calibration wire m
  • S6 In S4, replace the position of the calibration wire m with the corrected position in S5, and establish an optimized model of the detector parameters through all the calibration wires, and solve the optimized model to obtain the geometric parameters of the detector in the scanning plane. For example, establish the following optimization model based on the line of intersection relationship:
  • step S2 when there are multiple scan planes, in step S2, at least one set of projection slices containing calibration wire projections are extracted from each scan plane, and the different scan planes extract The projection slices correspond to the same slice position of the calibration part, and the starting position of the calibration part is detected to ensure that the projections obtained by different scanning planes correspond to the projection slices at the same position of the calibration part.
  • step S6 the following steps are included:
  • S7 Repeat S3 to S6 for each scanning plane to obtain the geometrical parameters of the detector and the position of the centroid of the calibration wire for each scanning plane, and
  • the calibration piece includes at least one calibration unit, and each of the calibration units includes multiple calibration wires, and the multiple calibration wires are The plane perpendicular to the conveying direction of the conveyor belt of the CT equipment is arranged according to a preset rule, and each of the calibration wires is in a straight line or other preset shapes.
  • the geometric parameter calibration parts of the CT equipment are easy to process, and can be applied to area array and linear array detectors, and can be used for geometric parameter calibration of spiral cone beam CT equipment and static CT equipment.

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Abstract

一种CT设备的几何参数标定件，该几何参数标定件包括至少一个标定单元（10），每个标定单元（10）均包括多根标定丝（2），多根标定丝（2）在同一平面内呈规则排布。该几何参数标定件易于加工，能够标定CT设备的几何参数，还公开了相应的标定方法，标定操作简单易实施。

Description

CT设备的几何参数标定件及标定方法
相关申请的交叉引用
本申请主张在2019年03月25日在中国专利局提交的中国专利申请No.201910226555.0的优先权，其全部内容通过引用包含于此。
技术领域
本公开涉及安检技术领域，尤其涉及一种CT设备的几何参数标定件及利用上述标定件标定CT设备的几何参数的标定方法。
背景技术
近几年，X射线计算机断层成像(computed tomography，CT)技术被广泛应用于医疗和安检领域。现阶段，绝大多数CT设备都采用螺旋锥束扫描方式，即将单靶点光源和弧形探测器安装至圆形滑环上，滑环转动以采集不同角度的投影数据，然后通过解析方法重建3维CT图像。该类型的设备通常只有单个扫描平面，光机靶点和探测器的相对位置固定不变，且系统涉及的几何参数较少。但是该设备的几何误差会造成重建图像的结构扭曲，数值不准和环状伪影等问题。除了螺旋锥束CT设备，采用分布式光源的静态CT设备也开始被应用于安检领域。静态CT设备拥有单个或多个扫描平面，每个扫描平面包含多个光源靶点，靶点可呈直线，弧形等形状排布；探测器由多个探测器臂拼接而成，单个探测器臂可以为直线、折线或弧形等多种形状。与螺旋锥束CT设备相比，静态CT无滑环设备的X光源和探测器位置固定不变，通过多平面扫描来保证射线的角度覆盖范围，并具有扫描速度快、噪声小等优点。由于扫描几何的特殊性，静态CT设备通常采用迭代重建方法获得3维图像，该方法不要求几何排布满足特定条件，但光机靶点和探测器晶体的位置需要精确定位，不同扫描平面的坐标系也需保持统一。然而，分布式光源与单靶点光源相比，体积、重量更大，安装的机械误差也会相应变大。由于光源靶点分布范围较广，光源整体的几何偏差通常会造成靶点位置严重偏离设计值，且每个靶点的偏移距离和偏移方向可能互不相同，造成重建物体形变，重建数值不准，并影响设备的空间分辨率和物质识别。另外，探测器臂的安装也会存在误差，因此对设备进行几何校正很有 必要性。
发明内容
本公开的目的旨在解决现有技术中存在的上述问题和缺陷的至少一个方面。
根据本公开一个方面的实施例，提供了一种CT设备的几何参数标定件，所述标定件包括至少一个标定单元，每个所述标定单元均包括多根标定丝，所述多根标定丝在同一平面内呈规则排布。
在一些实施例中，所述标定丝呈直线、折线或圆弧形状。
在一些实施例中，每个所述标定单元还包括：固定件，所述固定件被构造成用于固定所述多根标定丝。
在一些实施例中，所述多根标定丝直接固定在所述CT设备的传送带上或所述CT设备的通道内。
在一些实施例中，所述标定单元中的多根标定丝为等间隔排布。
在一些实施例中，所述多根标定丝与所述CT设备的传送带的传送方向平行或成一角度。
在一些实施例中，所述至少一个标定单元包括第一标定单元，所述第一标定单元的多根标定丝在平行于所述CT设备的传送带的传送方向的水平面内或者竖直面内排布。
在一些实施例中，所述至少一个标定单元还包括第二标定单元，所述第二标定单元的多根标定丝所在的平面与所述第一标定单元的多根标定丝所在的平面是垂直的。
在一些实施例中，所述至少一个标定单元还包括第三标定单元，所述第三标定单元的多根标定丝所在的平面与所述第一标定单元的多根标定丝所在的平面是垂直的，且所述第二标定单元和所述第三标定单元分别位于所述第一标定单元在垂直于所述传送带的传送方向的方向上的两端。
在一些实施例中，所述标定丝为圆柱形。
在一些实施例中，所述标定丝的直径为0.5mm-5mm。
根据本公开另一个方面的实施例，提供了一种利用根据上述CT设备的几何参数标定件对CT设备的几何参数进行标定的方法，包括以下步骤：
S1：根据标定件的几何参数计算标定丝的质心的理论位置；
S2：扫描所述标定件，在扫描平面抽取至少一组包含标定丝投影的投影切片；
S3：在所述投影切片上获取所述标定件的每根标定丝的质心的位置；
S4：针对每根标定丝，以光机为参考系，根据靶点和所述标定丝的质心连线与探测器的交点，以及S3中所获取的所述标定丝的质心的位置建立关于探测器参数和所述标定丝的质心的位置的优化模型，并求解该优化模型以获得该扫描平面内所有标定丝的质心的位置；
S5：使用位置匹配算法对S4获得的标定丝的质心的位置和S1计算得出的理论位置进行位置匹配，进而对S4获得的标定丝的质心的位置进行修正；
S6：基于标定丝的质心修正后的位置，并通过所有标定丝建立关于探测器参数的优化模型，求解该优化模型以获得该扫描平面的探测器几何参数。
在一些实施例中，当存在多个扫描平面时，在步骤S2中，在每个扫描平面抽取至少一组包含标定丝投影的投影切片，不同扫描平面所抽取的投影切片对应于所述标定件相同的切片位置；在步骤S6之后还包括以下步骤：
S7：对各扫描平面重复S3至S6，获取各扫描平面的探测器几何参数和标定丝的质心的位置的步骤；以及
S8：通过位置匹配算法，在统一的坐标系下表示S6中获得的标定丝的质心的位置，使标定丝在不同扫描平面内的质心的位置相同，以获取光机靶点和探测器晶体位置。
附图说明
图1为根据本公开的一种示例性实施例的CT设备的几何参数标定件的结构示意图。
图2为根据本公开的另一种示例性实施例的CT设备的几何参数标定件的结构示意图。
图3为根据本公开的再一种示例性实施例的CT设备的几何参数标定件的结构示意图。
图4为本公开的又一种示例性实施例的CT设备的几何参数标定件的结构示意图。
图5根据本公开的一种示例性实施例的CT设备的几何参数标定方法的流程图。
图6根据本公开的一种示例性实施例的CT设备的几何参数标定方法的另一流程图。
具体实施方式
虽然将参照含有本发明的较佳实施例的附图充分描述本发明，但在此描述之前应了解本领域的普通技术人员可修改本文中所描述的发明，同时获得本发明的技术效果。因此，须了解以上的描述对本领域的普通技术人员而言为一广泛的揭示，且其内容不在于限制本发明所描述的示例性实施例。
另外，在下面的详细描述中，为便于解释，阐述了许多具体的细节以提供对本披露实施例的全面理解。然而明显地，一个或多个实施例在没有这些具体细节的情况下也可以被实施。在其他情况下，公知的结构和装置以图示的方式体现以简化附图。
根据本公开的总体上的发明构思，提供了一种CT设备的几何参数标定件，其包括至少一个标定单元，每个所述标定单元均包括多根标定丝，所述多根标定丝在同一平面内呈规则排布。
图1为根据本公开的一种示例性实施例的CT设备的几何参数标定件的结构示意图。如图1所示，该CT设备的几何参数标定件包括一个标定单元10，该标定单元10包括多根标定丝2和固定件1。所述多根标定丝2在平行于传送带的传送方向的水平面内规则排布。标定丝2通常由高吸收材料制成，例如金属。标定丝2可以为柔性的(例如钢丝等)，也可以为刚性的(例如钢棒等)。每根标定丝2呈直线形状，标定丝2的横截面形状包括但不限于圆柱形，其直径例如可以为0.5mm-5mm。固定件1被构造成用于固定所述多根标定丝2，以保证标定丝2位置固定，从而使不同标定丝2之间的相对位置与理论设计值相符。固定件1可由低吸收材料制成。
需要说明的是，虽然在该实施例中示出的标定丝呈直线形状，然而本领域的技术人员应当理解，在本公开的其它一些实施例中，标定丝2也可以为折线、圆弧形状或其它规则的形状。此外，需要说明的是，本领域的技术人员应当理解，在本公开的其它一些实施例中，标定丝2也可以直接固定在CT设备的传送带上或CT设备的通道中。
如图1所示，在该示例性实施例中，标定单元10中的多根标定丝2彼此平行并且等间隔排布，以便于后续的计算。此外，在该实施例中，多根标定丝2与 CT设备的传送带的传送方向成一角度。然而，需要说明的是，本领域的技术人员应当理解，在本公开的其它一些实施例中，标定单元10中的多根标定丝2也可以平行于传送带的传送方向。
图2为根据本公开的另一种示例性实施例的CT设备的几何参数标定件的结构示意图。如图2所示，标定单元10中的多根标定丝2彼此平行并且在平行于CT设备的传送带的传送方向(如图2中箭头所示)的竖直面内等间隔排布，多根标定丝2与传送带的传送方向成一角度。
图3为根据本公开的再一种示例性实施例的CT设备的几何参数标定件的结构示意图。如图3所示，标定件包括两个标定单元：第一标定单元11和第二标定单元12，其中，第一标定单元11和第二标定单元12均包括多根标定丝2和固定件1，所述多根标定丝2呈规则排布，并且每根标定丝2呈直线状。固定件1被构造成用于固定所述多根标定丝2。第一标定单元11中的多根标定丝2在平行于CT设备的传送带的传送方向(如图3中箭头所示)的水平面内等间隔排布。第二标定单元12的多根标定丝2所在的平面与第一标定单元11的多根标定丝2所在的平面是垂直的，以使得整个标定件呈L形。
图4为根据本公开的又一种示例性实施例的CT设备的几何参数标定件的结构示意图。如图4所示，标定件包括三个标定单元：第一标定单元11、第二标定单元12和第三标定单元13，其中，第一标定单元11、第二标定单元12和第三标定单元13均包括多根标定丝2和固定件1，所述多根标定丝2呈规则排布，并且每根标定丝2呈直线状；固定件1被构造成用于固定所述多根标定丝2。其中，第一标定单元11中的多根标定丝2在平行于CT设备的传送带的传送方向(如图4中箭头所示)的水平面内等间隔排布。第二标定单元12的多根标定丝2所在的平面与第一标定单元11的多根标定丝2所在的平面是垂直的，第三标定单元13的多根标定丝2所在的平面与第一标定单元11的多根标定丝2所在的平面是垂直的，且第二标定单元11和第三标定单元13在垂直于传送带的传送方向的方向上分别位于第一标定单元11的两端，以使得整个标定件呈U形。
如图5所示，本公开还提供了一种利用上述标定件标定CT设备的几何参数的标定方法，包括以下步骤：
S1：根据标定件的设计参数，计算标定丝2质心的理论位置
Figure PCTCN2020073219-appb-000001
S2：扫描标定件，在扫描平面抽取包含标定丝2投影的投影切片，具体地，将标定件放置于CT设备的传动带上，以对标定件进行扫描，扫描过程中传动带 低速运行，检测标定件起始位置保证不同扫描平面获取的投影对应标定件相同位置的投影切片。此外，每个扫描平面可以等间隔地抽取例如3副以上的投影切片。
S3：使用图像处理方法在每个投影切片上获取标定丝2的质心的位置。由于受到探测器晶体尺寸的限制，标定丝2的质心的位置的检测精度为半个晶体宽度。假设标定件包含N根标定丝2，共采集了M组投影切片，由于传送带运动，每个投影切片的标定丝2的质心的位置各不相同，因此每个扫描平面包采集M*N根标定丝投影数据。如果靶点k出束，标定丝m的质心在探测器平面真实的投影的晶体标号记为
Figure PCTCN2020073219-appb-000002
S4：对于扫描平面内的单根标定丝m，以光机为参考系，根据靶点和所述标定丝m的质心连线与探测器的交点，以及S3中所获取的所述标定丝m的质心的位置建立关于探测器参数和所述标定丝的位置的优化模型，并求解该优化模型以获得该扫描平面内所有标定丝的位置。探测器相关的几何参数与探测器晶体的排布方式有关，例如直线探测器由探测器起始位置和晶体排布方向决定，弧形探测器由圆心、半径和起始角度决定。以直线探测器为例，探测器的参数记为(y,d)，其中y为探测器起始位置，d为探测器晶体排布方向向量。探测器直线方程记为L(y,d)，晶体尺寸记为δ。标定丝m的位置记为x m，靶点k的位置记为z k。标定丝与靶点连线记为L(x m,z k)。L(y,d)和L(x m,z k)两条直线相交于位置p k,m，对应晶体b k,m＝(p k,m-y)/δ。根据S3，靶点k和标定丝m在探测器平面上的投影晶体位置真实为
Figure PCTCN2020073219-appb-000003
通过最小化
Figure PCTCN2020073219-appb-000004
对参数(y,d)和x m进行优化。上述过程可描述为如下优化模型
Figure PCTCN2020073219-appb-000005
其中f(·,·)表示两条直线的交点坐标，||·|| p表示p范数。针对每根标定丝，求解上述优化模型获得所有标定丝的位置
Figure PCTCN2020073219-appb-000006
可使用模拟退火方法求解上述优化模型。
S5：使用位置匹配算法对S4获得的标定丝m的质心的位置和S1计算得出的理论位置进行位置匹配，进而对S4获得的标定丝m的质心的位置进行修正。由于S3和S4均存在误差，且标定件摆放姿态不定，S4所得到的标定丝m的质心的位置与S1计算得出的理论位置存在偏差。通过位置匹配算法将S4计算得出的标定丝的质心的位置
Figure PCTCN2020073219-appb-000007
和S1计算得出的理论位置
Figure PCTCN2020073219-appb-000008
进行配准，进而对
Figure PCTCN2020073219-appb-000009
进行校准，以获得标定丝m的最终位置
Figure PCTCN2020073219-appb-000010
S6：在S4中将标定丝m的位置替换为S5中修正后的位置，并通过所有标定丝建立关于探测器参数的优化模型，求解该优化模型已获得该扫描平面的探测器几何参数。例如根据交线关系建立关于如下优化模型：
Figure PCTCN2020073219-appb-000011
求解上述优化模型得到探测器几何参数y和d。
如图6所示，在本公开的一个示例性中，当存在多个扫描平面时，在步骤S2中，在每个扫描平面抽取至少一组包含标定丝投影的投影切片，不同扫描平面所抽取的投影切片对应于所述标定件相同的切片位置，检测标定件起始位置保证不同扫描平面获取的投影对应标定件相同位置的投影切片。此外，每个扫描平面例如可以等间隔地抽取例如3副以上的投影切片。在步骤S6之后还包括以下步骤：
S7:对各扫描平面重复S3至S6，获得各扫描平面的探测器几何参数和标定丝的质心的位置的步骤，以及
S8：通过位置匹配算法，在统一的坐标系下表示S6中获得的标定丝2的质心的位置，使标定丝2的质心在不同扫描平面的位置相同，以获取光机靶点和探测器晶体位置。以传送带的传送方向为z坐标轴方向，由于标定件位置保持不动随传送带前进，不同平面内标定丝在x-y平面的位置一致。通过位置匹配算法，在统一的坐标系下表示S6中获得的标定丝，使不同平面位置一致，相应的获取光机靶点和探测器晶体位置。
根据本公开上述实施例所述的CT设备的几何参数标定件及其标定方法，该标定件包括至少一个标定单元，每个所述标定单元均包括多根标定丝，所述多根标定丝在垂直于CT设备的传送带的传送方向的平面内按预设规则排布，并且每根所述标定丝呈直线或其他预设形状。使用时，将标定件放置于CT设备的传送带上或通道内，以对标定件进行扫描，通过标定丝在探测器平面的投影位置标定光机和探测器的相对位置，并获取标定丝的位置，以获得设备的光机靶点和探测器晶体位置。该CT设备的几何参数标定件易于加工，并且能够适用于面阵和线阵探测器，可用于对螺旋锥束CT设备和静态CT设备的几何参数标定。
本领域的技术人员可以理解，上面所描述的实施例都是示例性的，并且本 领域的技术人员可以对其进行改进，各种实施例中所描述的结构在不发生结构或者原理方面的冲突的情况下可以进行自由组合。
在详细说明本发明的较佳实施例之后，熟悉本领域的技术人员可清楚的了解，在不脱离随附权利要求的保护范围与精神下可进行各种变化与改变，且本发明亦不受限于说明书中所举示例性实施例的实施方式。

Claims (13)

  1. 一种CT设备的几何参数标定件，包括至少一个标定单元，每个所述标定单元均包括多根标定丝，所述多根标定丝在同一平面内呈规则排布。
  2. 根据权利要求1所述的标定件，其中，所述标定丝呈直线、折线或圆弧形状。
  3. 根据权利要求1所述的标定件，其中，每个所述标定单元还包括：固定件，所述固定件被构造成用于固定所述多根标定丝。
  4. 根据权利要求1所述的标定件，其中，所述多根标定丝直接固定在所述CT设备的传送带上或所述CT设备的通道内。
  5. 根据权利要求1-4中任一项所述的标定件，其中，所述标定单元中的多根标定丝为等间隔排布。
  6. 根据权利要求5所述的标定件，其中，所述多根标定丝与所述CT设备的传送带的传送方向平行或成一角度。
  7. 根据权利要求1-4中任一项所述的标定件，其中，所述至少一个标定单元包括第一标定单元，所述第一标定单元的多根标定丝在平行于所述CT设备的传送带的传送方向的水平面内或者竖直面内排布。
  8. 根据权利要求7所述的标定件，其中，所述至少一个标定单元还包括第二标定单元，所述第二标定单元的多根标定丝所在的平面与所述第一标定单元的多根标定丝所在的平面是垂直的。
  9. 根据权利要求8所述的标定件，其中，所述至少一个标定单元还包括第三标定单元，所述第三标定单元的多根标定丝所在的平面与所述第一标定单元的多根标定丝所在的平面是垂直的，且所述第二标定单元和所述第三标定单 元分别位于所述第一标定单元在垂直于所述传送带的传送方向的方向上的两端。
  10. 根据权利要求1-4中任一项所述的标定件，其中，所述标定丝为圆柱形。
  11. 根据权利要求10所述的标定件，其中，所述标定丝的直径为0.5mm-5mm。
  12. 一种利用根据权利要求1-11中任一项所述的CT设备的几何参数标定件对CT设备的几何参数进行标定的方法，包括以下步骤：
    S1：根据标定件的几何参数计算标定丝的质心的理论位置；
    S2：扫描所述标定件，在扫描平面抽取至少一组包含标定丝投影的投影切片；
    S3：在所述投影切片上获取所述标定件的每根标定丝的质心的位置；
    S4：针对每根标定丝，以光机为参考系，根据靶点和所述标定丝的质心连线与探测器的交点，以及S3中所获取的所述标定丝的质心的位置建立关于探测器参数和所述标定丝的质心的位置的优化模型，并求解该优化模型以获得该扫描平面内所有标定丝的质心的位置；
    S5：使用位置匹配算法对S4获得的标定丝的质心的位置和S1计算得出的理论位置进行位置匹配，进而对S4获得的标定丝的质心的位置进行修正；
    S6：基于标定丝的质心修正后的位置，并通过所有标定丝建立关于探测器参数的优化模型，求解该优化模型以获得该扫描平面的探测器几何参数。
  13. 根据权利要求12所述的方法，其中，当存在多个扫描平面时，在步骤S2中，在每个扫描平面抽取至少一组包含标定丝投影的投影切片，不同扫描平面所抽取的投影切片对应于所述标定件相同的切片位置；在步骤S6之后还包括以下步骤：
    S7：对各扫描平面重复S3至S6，获取各扫描平面的探测器几何参数和标定丝的质心的位置的步骤；以及
    S8：通过位置匹配算法，在统一的坐标系下表示S6中获得的标定丝的质 心的位置，使标定丝在不同扫描平面内的质心的位置相同，以获取光机靶点和探测器晶体位置。
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