WO2014000279A1 - G型臂x光机的三维图像生成方法及装置与g型臂x光机 - Google Patents

G型臂x光机的三维图像生成方法及装置与g型臂x光机 Download PDF

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Publication number
WO2014000279A1
WO2014000279A1 PCT/CN2012/077933 CN2012077933W WO2014000279A1 WO 2014000279 A1 WO2014000279 A1 WO 2014000279A1 CN 2012077933 W CN2012077933 W CN 2012077933W WO 2014000279 A1 WO2014000279 A1 WO 2014000279A1
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Prior art keywords
ray
arm
projection data
dimensional
dimensional image
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PCT/CN2012/077933
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English (en)
French (fr)
Inventor
厉夫兵
魏世宇
朱洵
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北京东方惠尔图像技术有限公司
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Priority to PCT/CN2012/077933 priority Critical patent/WO2014000279A1/zh
Priority to US14/411,392 priority patent/US9763640B2/en
Publication of WO2014000279A1 publication Critical patent/WO2014000279A1/zh

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    • 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
    • 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
    • A61B6/022—Stereoscopic imaging
    • 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
    • A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4007—Arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units
    • A61B6/4014—Arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units arranged in multiple source-detector units
    • 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
    • A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4064—Arrangements for generating radiation specially adapted for radiation diagnosis specially adapted for producing a particular type of beam
    • A61B6/4085—Cone-beams
    • 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
    • A61B6/44—Constructional features of apparatus for radiation diagnosis
    • A61B6/4429—Constructional features of apparatus for radiation diagnosis related to the mounting of source units and detector units
    • A61B6/4435—Constructional features of apparatus for radiation diagnosis related to the mounting of source units and detector units the source unit and the detector unit being coupled by a rigid structure
    • A61B6/4441—Constructional features of apparatus for radiation diagnosis related to the mounting of source units and detector units the source unit and the detector unit being coupled by a rigid structure the rigid structure being a C-arm or U-arm
    • 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
    • A61B6/44—Constructional features of apparatus for radiation diagnosis
    • A61B6/4476—Constructional features of apparatus for radiation diagnosis related to motor-assisted motion of the source unit
    • 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
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T11/00—2D [Two Dimensional] image generation
    • G06T11/003—Reconstruction from projections, e.g. tomography
    • G06T11/006—Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2211/00—Image generation
    • G06T2211/40—Computed tomography
    • G06T2211/421—Filtered back projection [FBP]

Definitions

  • the present invention relates to the field of medical devices, and in particular to a method and a device for generating a three-dimensional image of a G-arm X-ray machine and G-arm X-ray machine.
  • a method and a device for generating a three-dimensional image of a G-arm X-ray machine and G-arm X-ray machine BACKGROUND OF THE INVENTION
  • imaging methods of X-ray machines are usually given in two-dimensional images.
  • Existing solutions include Computed Tomography (CT), C-arm fluoroscopic images, and the like.
  • CT Computed Tomography
  • C-arm fluoroscopic images and the like.
  • the 2D image information can only give image data of a certain angle or a certain section, and cannot reflect the overall information of the imaged part.
  • Computed tomography is the use of parallel or sectoral X-rays to measure the angles of the detected objects at different angles.
  • the 360° line projection data is obtained by back projection calculation of the line projection data to obtain a reconstructed image of the two-dimensional slice.
  • the three-dimensional reconstructed image data of the target is obtained by merging the continuously acquired two-dimensional slice image data.
  • the CT is then used for tomography and then analyzed graphically.
  • the parallel or sectoral ray mechanism of CT makes the light field utilization of the X-ray tube low.
  • Cone Beam Computed Tomography uses a cone-shaped stereo beam source and an area array detector to fluoroscopy the object, so that the projection data of multiple sections of the measured object can be acquired in one scan.
  • the three-dimensional image of the target can be reconstructed through a series of perspective projections at different angles and according to the corresponding reconstruction algorithm.
  • the cone beam CT has the advantages of high radiation utilization and direct reconstruction of three-dimensional images.
  • the traditional C-arm X-ray machine is close to the application requirements of cone beam CT, so the CBCT technology has been conveniently applied on the C-arm X-ray machine.
  • the cone beam CT scanning process using a C-arm X-ray machine requires that the X-ray tube of the C-arm rotates at least 180°+2 ⁇ around the detection target, where ⁇ is the half-angle of the X-ray beam of the cone beam CT, and then utilizes The two-dimensional projection of the angle is three-dimensionally reconstructed.
  • the above algorithm for reconstructing a three-dimensional image based on two-dimensional projection image data can be found in LA Feldkamp, LC Davis and JW Kress. Practical cone-beam algorithm. J. Opt. Soc. Am. A, vol. 1, no. 6, 1984, Pp. 612-619.
  • This FDK algorithm is a classical approximate 3D image reconstruction algorithm. It has a simple mathematical form and is easy to implement.
  • K. Wiesent has made corresponding improvements to the FDK algorithm, see K. Wiesent, K. Barth, N. Navab, et al. Enhanced 3 -D-reconstruction algorithm for C-Arm Systems suitable for interventional procedures. IEEE Trans. Med. Imag., vol. 19, no. 5, 2000. pp. 391-403.
  • the above C-arm X-ray machine uses CBCT for three-dimensional image reconstruction, which has the following problems:
  • the X-ray tube of the C-arm needs to be rotated by at least 180°+2 ⁇ around the detection target, and the image acquisition time is long, so that the irradiation time of the target under X-ray is Long, low detection efficiency.
  • the intensity distribution of the space square of CBCT is uneven.
  • the intensity of the light field of the center beam is greater than the intensity of the light field at other positions, and the inconsistency of the intensity of the light field causes the gray of each perspective image. Degree changes.
  • the quality of the reconstructed three-dimensional image is affected.
  • the problem that the measured target has a long irradiation time under X-ray has not yet proposed an effective solution.
  • a primary object of the present invention is to provide a G-arm X-ray machine three-dimensional image generation method and apparatus and a G-arm X-ray machine to solve the cone-beam CT scan of the C-arm X-ray machine in the prior art.
  • the subject In the process of reconstructing a three-dimensional image, the subject is exposed to a long time under X-rays.
  • a three-dimensional image generating method of a G-arm X-ray machine is provided.
  • the method for generating a three-dimensional image of a G-arm X-ray machine comprises: controlling a G-arm to rotate from an initial angle to a target angle, and acquiring a plurality of groups of the measured object when the G-arm is at different angles during the rotation process Two-dimensional projection data, wherein each set of two-dimensional projection data includes two-way projection data; using multiple sets of two-dimensional projection data to perform calculation according to FDK algorithm or FDK correction algorithm to obtain a three-dimensional image of the measured object; image.
  • acquiring the plurality of sets of two-dimensional projection data of the measured object when the G-arm is at different angles during the rotation comprises: setting one image acquisition position within a range from an initial angle to a target angle; determining the G-arm in real time Rotation angle; When the G boom is rotated to each image acquisition position, a set of two-dimensional projection data is acquired by two X-ray receivers corresponding to the two X-ray tubes. Further, the angles of each two adjacent image acquisition positions are equal. Further, the angular difference between the initial angle and the target angle is 90°+ ⁇ , where ⁇ is the half-angle of the X-ray beam emitted by the X-ray tube.
  • the method further comprises: acquiring a set value of the current and the voltage of the X-ray tube; and starting the two X-ray tubes according to the set values of the current and the voltage.
  • the method further comprises: measuring a spatial distribution of the X-ray beam radiation intensity emitted by the two X-ray tubes to obtain a spatial distribution unevenness function, using multiple groups
  • the two-dimensional projection data is calculated according to the FDK algorithm or the FDK correction algorithm, including: calibrating a plurality of sets of two-dimensional projection data by using a spatial distribution unevenness function; and performing calculation by using the calibrated two-dimensional projection data according to the FDK algorithm or the FDK correction algorithm.
  • measuring the spatial distribution of the X-ray beam radiation intensity emitted by the two X-ray tubes to obtain a spatial distribution unevenness function includes: separately acquiring X-rays emitted by the two X-ray tubes through two X-ray receivers Beam projection brightness data after passing through the attenuation plate; calculating the spatial distribution unevenness function of the two X-ray beams by using the projection luminance data.
  • the method further comprises: separately calculating the average radiation intensity of the two X-ray beams, and using the spatial distribution unevenness function to multi-group two-dimensional projection
  • the calibration of the data includes: normalizing the plurality of sets of two-dimensional projection data according to the average radiation intensity of the two X-ray beams; and performing normalized processing of the plurality of sets of two-dimensional projection data by using the spatial distribution inhomogeneity function; calibration.
  • a three-dimensional image generating apparatus for a G-arm X-ray machine comprises: a motion control module for controlling
  • the G-arm rotates from the initial angle to the target angle;
  • the image data acquisition module is configured to acquire a plurality of sets of two-dimensional projection data of the measured object when the G-arm is at different angles, wherein each set of two-dimensional projection data includes two projection data ;
  • the plurality of sets of two-dimensional projection data are calculated according to the FDK algorithm or the FDK correction algorithm to obtain a three-dimensional image of the measured object; and the output module is configured to output a three-dimensional image of the measured object.
  • the three-dimensional image generating device of the G-arm X-ray machine further includes: a ray intensity calibration module for measuring a spatial distribution of X-ray beam radiation intensity emitted by two X-ray tubes to obtain a space Distribution unevenness function.
  • a G-arm X-ray machine comprising a three-dimensional image generating device of any of the G-arm X-ray machines described above is provided.
  • the three-dimensional image generating method of the G-arm X-ray machine includes: controlling the G-arm to rotate from the initial angle to the target angle, and maintaining the current and voltage of the two X-ray tubes unchanged during the rotation; The plurality of sets of two-dimensional projection data of the measured object when the G-arm is at different angles, wherein each set of two-dimensional projection data includes two projection data; using multiple sets of two-dimensional projection data according to the FDK algorithm or the FDK correction algorithm, Obtain a three-dimensional image of the object to be measured; output a three-dimensional image of the object to be measured.
  • FIG. 1A is a schematic view showing a G-arm in an initial angle in a G-arm X-ray machine according to an embodiment of the present invention
  • FIG. 1B is a G-arm in a G-arm X-ray machine according to an embodiment of the present invention
  • 2 is a schematic diagram of a three-dimensional image generating device of a G-arm X-ray machine according to an embodiment of the present invention
  • FIG. 3 is a schematic diagram of a three-dimensional image generating method of a G-arm X-ray machine according to an embodiment of the present invention
  • 4 is a schematic diagram of projection of cone beam X-rays on an X-ray receiver in a three-dimensional image generation method of a G-arm X-ray machine according to an embodiment of the present invention
  • FIG. 5A is a G-arm X-ray according to an embodiment of the present invention.
  • FIG. 5B is a schematic plan view showing a non-uniform spatial distribution of X-rays in a three-dimensional image generating method of a G-arm X-ray machine according to an embodiment of the present invention
  • FIG. 6 is a schematic diagram of two-way X-ray inconsistency test in a three-dimensional image generation method of a G-arm X-ray machine according to an embodiment of the present invention.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments. 1A and FIG.
  • FIG. 1B are schematic diagrams showing a G-arm in an initial angle state and a target angle state in a G-arm X-ray machine according to an embodiment of the present invention, as shown in FIG. 1, a single X-ray different from a C-arm.
  • the G-arm X-ray machine is fixedly provided with two X-ray tubes 1A, 2A and two X-ray receivers 1B, 2B corresponding thereto, and the G-arm 3 is a 3/4 arc structure.
  • the first X-ray tube 1A is for emitting lateral cone beam X-rays
  • the first X-ray receiver 1B is disposed on the G-arm 3 opposite to the first X-ray tube 1 A a position for receiving lateral cone beam X-rays transmitted through the object to be measured
  • a second X-ray tube 2A for emitting longitudinal cone beam X-rays
  • a second X-ray receiver 2B disposed on the G-arm 3
  • the second X-ray tube 2A is opposed to a position for receiving a cone beam X-ray transmitted through the longitudinal direction of the detection object.
  • the two X-ray tubes 1A, 2A need only be rotated counterclockwise or clockwise by 90°+y, that is, the G-arm 3 is rotated from the state of FIG. 1A to the state of FIG. 1B.
  • Obtaining 180°+2y fluoroscopic image data of the measured object saves half of the image acquisition time of the C-arm, that is, the exposure time of the measured object is reduced by half, effectively improving the detection efficiency.
  • the three-dimensional image generating device 4 of the G-arm X-ray machine controls the rotation of the G-arm 3 and acquires the two-dimensional projection data received by the first X-ray receiver 1B and the second X-ray receiver 2B during the rotation, and passes Two-dimensional projection data in multiple directions is calculated to generate a three-dimensional image of the object to be measured.
  • the connection between the first X-ray tube 1A and the first X-ray receiver 1B and the connection between the second X-ray tube 2A and the second X-ray receiver 2B are perpendicular to each other, and the object to be measured is placed in the circle of the G-arm 3 At the center of the arc.
  • the G-arm X-ray machine comprises two X-ray tubes and two X-ray receivers, and a G-arm that can rotate around the object to be measured, thereby simultaneously acquiring projection data of multiple orientations in two directions, reconstructing a tomographic image, and shortening the scanning. Time, improving imaging efficiency.
  • 2 is a schematic diagram of a three-dimensional image generating device of a G-arm X-ray machine according to an embodiment of the present invention. As shown in FIG.
  • a three-dimensional image generating device of a G-arm X-ray machine includes: a motion control module 21 For controlling the G-arm 3 to rotate from the initial angle to the target angle; the image data acquisition module 23 is configured to acquire a plurality of sets of two-dimensional projection data of the measured object when the G-arm 3 is at different angles, wherein each group is two-dimensionally
  • the projection data includes two projection data; the data processing module 25 is configured to perform calculation according to the FDK algorithm or the FDK correction algorithm by using multiple sets of two-dimensional projection data to obtain a three-dimensional image of the measured object; and the output module 27 is configured to output the measured A three-dimensional image of the object.
  • the motion control module 21 can be implemented by using a control device such as an industrial computer or a PLC to drive the motor of the rotating G boom;
  • the image data acquisition module 23 includes an image acquisition device for collecting the received image of the X-ray receiver and converting the digital image into a digital signal. form.
  • the data processing module 25 uses a computer, a digital processor (DSP), etc. to compute a powerful computing device.
  • the output module may be a display for displaying a three-dimensional image, or a memory for storing the three-dimensional image data for subsequent analysis.
  • Obtaining the full-view three-dimensional information of the measured object requires at least 180°+2y X-ray scanning of the measured object, and the structure of the dual X-ray scanning of the G-arm X-ray machine according to the embodiment of the present invention requires only the G-arm Frame 3
  • a 90°+2y scan of the target being measured can be completed by 90°+y. It is therefore preferable to set the angular difference between the initial angle and the target angle to be 90°+y.
  • the motion control module 21 sets N image acquisition positions in the orientation between the initial angle and the target angle, in the rotation process of the G-arm 3
  • the image data acquisition module 23 collects a set of two-dimensional projection data through the two X-ray receivers when the G boom is rotated to each of the image acquisition positions, so that during the rotation process N sets of two-dimensional projection images can be obtained.
  • N - 1 is equally divided between the initial angle and the target angle, and each of the equal-point positions plus the initial angular position and the target angular position are combined to obtain N image acquisition positions. That is to say, for each rotation (90°+ /N angle, two first X-ray receivers 1B, 2B respectively obtain a two-dimensional projection image of the position, and after rotating 90°+y, 2N two-dimensional images are obtained. Projecting an image. The magnitude of the intensity of the X-rays needs to be adjusted for different types of objects to be measured.
  • the 3D image generating device of the G-arm X-ray machine of the embodiment may further include an X-ray emission control module for acquiring The set values of the current and voltage of the X-ray tube 1A, IB; and the two X-ray tubes 1A, 1B are activated according to the set values of the current and voltage.
  • the current value of the X-ray tube is ensured.
  • the voltage value is kept constant, so that the intensity of the X-ray is kept stable, and the obtained two-dimensional projection image is guaranteed to have the same brightness.
  • the light field intensity of the central beam cannot be guaranteed to be equal to the light field at other positions.
  • the 3D image generating device of the X-ray machine may further be provided with a ray intensity calibration module for measuring the spatial distribution of the X-ray beam radiation intensity emitted by the two X-ray tubes 1A, IB to obtain a spatial distribution.
  • the uniformity function may be provided with a ray intensity calibration module for measuring the spatial distribution of the X-ray beam radiation intensity emitted by the two X-ray tubes 1A, IB to obtain a spatial distribution.
  • the data processing module 25 firstly uses the spatial distribution inhomogeneity function to calibrate the acquired sets of two-dimensional projection data, and then uses the calibrated two-dimensional projection data to perform calculation according to the FDK algorithm or the FDK correction algorithm.
  • the working process of the intensity calibration module is: collecting the projection brightness data of the X-ray beam emitted by the two X-ray tubes 1 A and 2A through the attenuation board by the two X-ray receivers 1B and 2B; respectively calculating the brightness data by using the projection brightness data
  • the spatial distribution non-uniformity function of the two X-ray beams is obtained.
  • the X-ray tube production process does not guarantee that the X-ray intensity of each X-ray tube is exactly the same under the same voltage and current, so the G-arm exists.
  • the intensity of the two X-ray tubes 1A, 2A after they are emitted from the emission window is also inconsistent, which results in an average brightening of the two-way fluoroscopic images.
  • the specific performance of a dark Therefore, it is necessary to obtain the relationship between the two X's in terms of the average light field intensity, and normalize the processing to improve the quality of the generated three-dimensional image.
  • the ray intensity calibration module is further configured to calculate an average radiant intensity of the two X-ray beams, and the data processing module 25 normalizes the plurality of sets of two-dimensional projection data according to the average radiance of the two X-ray beams; Then, the spatially distributed unevenness function is used to calibrate the normalized multi-group two-dimensional projection data, and the calibrated data is used for the FDK algorithm calculation. After the above-mentioned processing of the plurality of sets of two-dimensional projection data, the consistency of the images acquired by the different X-ray receivers can be ensured, and the quality of the generated three-dimensional images is higher.
  • the output module 27 can output the XZ section, the YZ section, and the XY section of the object to be measured by using the 3D image data obtained by the data processing module 25 in addition to the 3D image of the object to be measured.
  • the coordinates of the current position in the 3D target can be output corresponding to the three sections.
  • the output module 27 uses the display device, the entire display area can be divided into four blocks, and the XZ section, the YZ section, the XY section, and the generated three-dimensional image are respectively displayed.
  • the embodiment of the invention further provides a G-arm X-ray machine, which comprises a three-dimensional image generating device of any G-arm X-ray machine provided by the above content of the embodiment of the invention.
  • the embodiment of the present invention further provides a three-dimensional image method of a G-arm X-ray machine, which can be performed by any of the three-dimensional image generating devices provided by the above embodiments of the present invention, and FIG. 3 is an embodiment according to the present invention. As shown in FIG.
  • the method for generating a three-dimensional image of the G-arm X-ray machine includes: Step S31, controlling the G-arm to rotate from an initial angle to Target angle, in the process of obtaining, the plurality of sets of two-dimensional projection data of the measured object when the G-arm is at different angles, wherein each set of two-dimensional projection data includes two projection data; Step S33, using multiple sets of two-dimensional projection data The calculation is performed according to the FDK algorithm or the FDK correction algorithm to obtain a three-dimensional image of the object to be measured; and in step S35, a three-dimensional image of the object to be measured is output.
  • the number of two-dimensional projection images that need to be acquired can be obtained. Assuming that the number of images that each X-ray receiver needs to acquire is N, the object to be measured is acquired in the G-arm during the rotation in step S31.
  • the plurality of sets of two-dimensional projection data at different angles may include: setting N image acquisition positions within an initial angle to a target angle; determining a rotation angle of the G boom in real time; and rotating the G boom to each image When acquiring the position, a set of two-dimensional projection data is acquired by two X-ray receivers corresponding to the two X-ray tubes.
  • the angle of each two adjacent image acquisition positions can be set to an equal angle by dividing the initial angle to the target angle by N - 1 , and the position of each of the equal points plus the initial angular position and target A total of N image acquisition positions are obtained at the angular position.
  • Obtaining the full-view three-dimensional information of the measured object requires at least 180°+2y X-ray scanning of the measured object, and the structure of the dual X-ray scanning of the G-arm X-ray machine according to the embodiment of the present invention requires only the G-arm
  • the frame 3 is rotated by 90°+y to complete the 180°+2y scan of the target. It is therefore preferable to set the angular difference between the initial angle and the target angle to be 90°+y.
  • the image acquisition position is determined in an aliquot manner, and it is ensured that each rotation (90°+ /N angle, the two first X-ray receivers 1B, 2B respectively obtain a two-dimensional projection image of the position, and rotate After 90°+y, 2N two-dimensional projection images are obtained.
  • the method may further include: acquiring an X-ray tube The current and voltage settings; start the two X-ray tubes according to the current and voltage settings.
  • the current and voltage settings of the above X-ray tube are flexibly set according to the type of object to be measured.
  • the light field intensity of the center beam and the light field at other positions cannot be guaranteed.
  • the intensity is completely equal, and the inconsistency of the intensity of the light field causes a change in the gray level of each fluoroscopic image, so it is necessary to calibrate each of the optical field inhomogeneities of each X-ray.
  • the method Before controlling the rotation of the G-arm from the initial angle to the target angle, the method further comprises: measuring a spatial distribution of the X-ray beam radiation intensity emitted by the two X-ray tubes to obtain a spatial distribution unevenness function, Then, the step S31 uses multiple sets of two-dimensional projection data to perform calculation according to the FDK algorithm or the FDK correction algorithm, including: calibrating a plurality of sets of two-dimensional projection data by using a spatial distribution unevenness function; using the calibrated two-dimensional projection data according to FDK The algorithm or the FDK correction algorithm is used for calculation.
  • FIG. 4 is a cone in a three-dimensional image generation method of a G-arm X-ray machine according to an embodiment of the invention.
  • FIG. 5A is a perspective view showing a non-uniform spatial distribution of X-rays in a three-dimensional image generation method of a G-arm X-ray machine according to an embodiment of the present invention
  • FIG. Inventive embodiment A schematic plan view of the spatial distribution of X-rays in a three-dimensional image generation method of a G-arm X-ray machine.
  • the first X-ray tube 1 A and the first X-ray receiver 1B are exemplified, but the second X-ray tube 2A and the second X-ray receiver 2B measure the spatial distribution in the same manner.
  • 42 is the projection range of the cone X-ray beam on the X-ray receiver 1B
  • 0 point is the projection position of the center beam of the cone beam X-ray at the X-ray receiver 1B
  • the (x, y) point is At the projection position of the light beam 2 at the X-ray receiver 1B
  • the angle between the light beam 2 and the central light beam is from the point 0 to the point of (x, y) is r
  • 51 is a texture uniform attenuation plate
  • the first X-ray tube 1A The distance from the first X-ray receiver 1B is h
  • d r do is the distance between the beam 2 and the center beam passing through the attenuation plate 51, respectively.
  • the X-ray radiation intensity distribution at different voltage values of kV is uneven, varying with spatial position. It is assumed that the intensity of the center beam is I Q and the intensity of the beam at the point of (x, y) is I, as shown in FIG.
  • the X-ray tube emitted X-ray intensity unevenness distribution can be obtained by measuring image data received by the receiver.
  • the specific method is: placing a uniform attenuation plate 51 perpendicular to the central beam between the first X-ray tube and the first X-ray receiver 1B, and measuring the light field intensity data I x , y received by the X-ray receiver, As shown in FIG. 5, the light field intensity data I x , y received by the X-ray receiver is filtered by the filter to filter the light field intensity data, and then smoothed to obtain the processed light field intensity data I ( x ,
  • the attenuation of the beam should conform to Beer's law.
  • the unevenness of the outgoing light intensity of the X-ray tube at a kV voltage of coordinates (x, y) can be obtained.
  • p(x, y, kV) is: Where ⁇ is the X-ray attenuation coefficient of the attenuation plate 51 at the test voltage, and d Q is the thickness of the attenuation plate.
  • the X-ray exit light field intensity p of the X-ray tube is a function of position (x, y) and is also a function of voltage variation.
  • the spatial distribution unevenness function of the second X-ray tube can be measured using the same method.
  • P(x, y, kV) is made into a three-dimensional matrix, where the first two dimensions are the values of the coordinates (x, y) and the third dimension is the test voltage value.
  • Gradually changing the magnitude of the test voltage you can get a series of accurate data of the intensity variation of the outgoing light with voltage.
  • the data between the two voltage changes can be determined by interpolation. Thereby a spatial distribution unevenness function is obtained.
  • the X-ray tube production process does not guarantee that the X-ray intensity of each X-ray tube is exactly the same under the same voltage and current conditions. Therefore, the intensity of the two X-ray tubes 1A, 2A after exiting from the emission window is also present in the G-arm.
  • FIG. 6 is a schematic diagram of two-way X-ray inconsistency test in a three-dimensional image generation method of a G-arm X-ray machine according to an embodiment of the present invention.
  • two X-ray tubes are combined. Can not guarantee the exact same. Therefore, even if the same input signal is set, the X-ray radiation intensity of the two X-ray tubes is not uniform except for the unevenness.
  • the same attenuation plate 51 is placed between the two X-ray sources and the X receiver, and perpendicular to the X-ray beam, the light field received by the X-ray receiver is measured.
  • the intensity data is filtered, and the optical field intensity data is filtered to obtain first X-ray average radiation data I x 'y) and second X-ray radiation data r 2 (x, y), respectively.
  • the angle of the opening angle, ⁇ is the arc integral space.
  • the three-dimensional image generation method separately calculates the spatial distribution unevenness function of the two X-ray beams by using the projection luminance data, and may further comprise: respectively calculating the average radiation intensity of the two X-ray beams, thereby utilizing the spatial distribution unevenness function to the plurality of groups
  • the calibration of the two-dimensional projection data includes: normalizing the plurality of sets of two-dimensional projection data according to the average radiation intensity of the two X-ray beams; and normalizing the group two-dimensional projection by using the spatial distribution unevenness function pair The data is calibrated.
  • the three-dimensional image generating method of the G-arm X-ray machine includes: controlling the G-arm to rotate from the initial angle to the target angle, and maintaining the current and voltage of the two X-ray tubes during the rotation Unchanged
  • the data acquisition time is greatly reduced, the illumination time of the measured object under the X-ray is effectively reduced, and the three-dimensional image of the measured object is directly output, reflecting the overall information of the measured object.
  • modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices.
  • they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or they may be Multiple modules or steps are made into a single integrated circuit module.
  • the invention is not limited to any specific combination of hardware and software.

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Abstract

本发明提供了一种G型臂X光机的三维图像生成方法及装置与G型臂X光机，包括：控制G臂架从初始角度旋转至目标角度，在旋转过程中保持两路X射线管的电流和电压不变；获取被测对象在G型臂处于不同角度时的多组二维投影数据，其中每组二维投影数据包括两路投影数据；利用多组二维投影数据按照FDK算法或FDK修正算法进行计算，以得到被测对象的三维影像；输出被测对象的三维影像。从而通过获取两路投影数据，大大减少了数据的获取时间，有效降低了被测对象在X射线下的照射时间，直接输出被测对象的三维图像，反映了被测对象的全貌信息，解决了现有技术被测目标在X光下的照射时间长的问题。

Description

G型臂 X光机的三维图像生成方法及装置与 G型臂 X光机 技术领域 本发明涉及医疗器械领域， 具体而言， 涉及一种 G型臂 X光机的三维图像生成方 法及装置与 G型臂 X光机。 背景技术 目前 X光机的成像方式通常以二维影像方式给出， 现有的方案包括计算断层成像 ( Computed Tomography, CT ) , C型臂透视影像等等。 但二维影像信息只能给出某个 角度或某个断面的影像数据， 不能反映成像部位的全貌信息。 近年来， 也出现了利用二维投影图像进行三维图像重建的技术， 主要有以下几种： 计算机断层成像技术是利用平行或扇面 X射线对被检测目标的切面进行不同角度 的射线投影测量， 得到 360°的线投影数据， 通过将线投影数据进行反投影计算， 得到 二维切片的重建图像。 然后通过将连续获取的二维切片图像数据进行拼叠， 得到目标 的三维重建图像数据。从而利用 CT进行断层扫描， 然后以图像方式分析。但 CT的平 行或扇面射线机制使得 X射线管的光场利用率低。 锥束 CT ( Cone Beam Computed Tomography, CBCT ) 利用锥形立体束射线源和面 阵探测器对物体进行射线透视投影， 因而一次扫描即可获取被测物体多个截面的投影 数据。 通过一系列不同角度的透视投影， 并根据相应的重建算法可以重建目标的三维 图像。相对于传统 CT的平面射线束， 锥束 CT具有射线利用率高、可直接重建三维图 像等优势。传统的 C型臂 X光机接近锥束 CT的应用要求， 因而 CBCT技术在 C型臂 X光机上得到了方便应用。利用 C型臂 X光机进行锥束 CT扫描过程需要将 C型臂的 X射线管围绕检测目标至少旋转 180°+2γ，其中 γ为锥束 CT的 X射线束的半张角，然 后利用多角度的二维投影进行三维重建。 以上基于二维投影图像数据重建三维图像的算法基础可参见 L.A. Feldkamp, L.C. Davis and J.W. Kress. Practical cone-beam algorithm. J. Opt. Soc. Am. A, vol. 1, no. 6, 1984, pp. 612-619。 这种 FDK算法是经典的近似三维图像重建算法， 具有数学形式简 单， 实现容易， 并且当锥角较小时， 能够取得较好的重建效果， 得到了广泛的应用。 为了适用于 C型臂的实际测量情况， K. Wiesent对 FDK算法进行相应的改进， 可参见 K. Wiesent, K. Barth, N. Navab, et al. Enhanced 3 -D-reconstruction algorithm for C-Arm systems suitable for interventional procedures. IEEE Trans. Med. Imag., vol. 19, no. 5, 2000. pp. 391-403。 但是以上 C型臂 X光机利用 CBCT进行三维图像重建的方法存在以下问题：
1、 利用 C型臂 X光机进行锥束 CT扫描过程需要将 C型臂的 X射线管围绕检测 目标至少旋转 180°+2γ， 图像获取时间长， 使被测目标在 X光下的照射时间长， 检测 效率低。
2、 CBCT的空间广场强度分布不均匀， 这时因为 X射线束， 中心射线束的光场强 度大于其它位置的光场强度， 而这种光场强度的不一致性会引起每幅透视图像的灰度 变化。 从而导致以此为依据重建的三维图像质量受到影响。 针对现有技术中存在的利用 C型臂 X光机进行锥束 CT扫描重建三维图像的过程 中， 被测目标在 X光下的照射时间长的问题， 目前尚未提出有效的解决方案。 发明内容 本发明的主要目的是提供一种 G型臂 X光机的三维图像生成方法及装置与 G型 臂 X光机， 以解决现有技术中的 C型臂 X光机进行锥束 CT扫描重建三维图像的过程 中， 被测目标在 X光下的照射时间长的问题。 为了实现上述目的， 根据本发明的一个方面， 提供了一种 G型臂 X光机的三维图 像生成方法。 本发明提供的一种 G型臂 X光机的三维影像生成方法包括： 控制 G臂架从初始 角度旋转至目标角度， 在旋转过程中获取被测对象在 G型臂处于不同角度时的多组二 维投影数据， 其中每组二维投影数据包括两路投影数据； 利用多组二维投影数据按照 FDK算法或 FDK修正算法进行计算， 以得到被测对象的三维影像； 输出被测对象的 三维影像。 进一步地， 在旋转过程中获取被测对象在 G型臂处于不同角度时的多组二维投影 数据包括： 在初始角度至目标角度的范围内设置 Ν个图像获取位置； 实时判断 G臂架 的旋转角度； 当 G臂架旋转至各个图像获取位置时， 通过与两路 X射线管对应设置的 两路 X射线接收器采集一组二维投影数据。 进一步地， 每两个相邻的图像获取位置的角度相等。 进一步地， 初始角度至目标角度之间的角度差为 90°+γ， 其中 γ为 X射线管发射 的 X射线束的半张角。 进一步地， 在控制 G臂架从初始角度旋转至目标角度之前还包括： 获取 X射线管 的电流和电压的设置值； 按照电流和电压的设置值启动两路 X射线管。 进一步地， 在控制 G臂架从初始角度旋转至目标角度之前还包括： 对两路 X射线 管发出的 X射线束辐射强度的空间分布进行测量以得出空间分布不均匀度函数， 利用 多组二维投影数据按照 FDK算法或 FDK修正算法进行计算包括： 利用空间分布不均 匀度函数对多组二维投影数据进行校准；利用校准后的二维投影数据按照 FDK算法或 FDK修正算法进行计算。 进一步地，对两路 X射线管发出的 X射线束辐射强度的空间分布进行测量以得出 空间分布不均匀度函数包括：通过两路 X射线接收器分别采集两路 X射线管发出的 X 射线束通过衰减板后的投影亮度数据； 利用投影亮度数据分别计算两路 X射线束的空 间分布不均匀度函数。 进一步地， 利用投影亮度数据分别计算两路 X射线束的空间分布不均匀度函数之 后还包括： 分别计算两路 X射线束的平均辐射强度， 利用空间分布不均匀度函数对多 组二维投影数据进行校准包括： 根据两路 X射线束的平均辐射强度对多组二维投影数 据进行归一化计算； 利用空间分布不均匀度函数对进行归一化处理后的多组二维投影 数据进行校准。 根据本发明的另一个方面， 提供了一种 G型臂 X光机的三维影像生成装置。 本发明提供的 G型臂 X光机的三维影像生成装置包括： 运动控制模块， 用于控制
G臂架从初始角度旋转至目标角度； 影像数据采集模块， 用于获取被测对象在 G型臂 处于不同角度时的多组二维投影数据， 其中每组二维投影数据包括两路投影数据； 数 据处理模块，用于利用？ 多组二维投影数据按照 FDK算法或 FDK修正算法进行计算， 以得到被测对象的三维影像； 输出模块， 用于输出被测对象的三维影像。 进一步地， 本发明提供的 G型臂 X光机的三维影像生成装置还包括： 射线强度校 准模块，用于对两路 X射线管发出的 X射线束辐射强度的空间分布进行测量以得出空 间分布不均匀度函数。 根据本发明的另一个方面， 提供了一种 G型臂 X光机， 该 G型臂 X光机包括上 述任一种的 G型臂 X光机的三维影像生成装置。 根据本发明的技术方案， G型臂 X光机的三维影像生成方法包括： 控制 G臂架从 初始角度旋转至目标角度， 在旋转过程中保持两路 X射线管的电流和电压不变； 获取 被测对象在 G型臂处于不同角度时的多组二维投影数据， 其中每组二维投影数据包括 两路投影数据； 利用多组二维投影数据按照 FDK算法或 FDK修正算法进行计算， 以 得到被测对象的三维影像； 输出被测对象的三维影像。 从而通过获取两路投影数据， 大大减少了数据的获取时间， 有效降低了被测对象在 X射线下的照射时间， 直接输出 被测对象的三维图像， 反映了被测对象的全貌信息。 附图说明 说明书附图用来提供对本发明的进一步理解， 构成本申请的一部分， 本发明的示 意性实施例及其说明用于解释本发明， 并不构成对本发明的不当限定。 在附图中： 图 1A是根据本发明实施例的 G型臂 X光机中 G臂架位于初始角度的示意图； 图 1B是根据本发明实施例的 G型臂 X光机中 G臂架位于目标角度的示意图； 图 2是根据本发明实施例的 G型臂 X光机的三维影像生成装置示意图； 图 3是根据本发明实施例的 G型臂 X光机的三维影像生成方法的示意图； 图 4是根据本发明实施例的 G型臂 X光机的三维影像生成方法中锥束 X射线在 X 射线接收器上的投影示意图； 图 5A是是根据本发明实施例的 G型臂 X光机的三维影像生成方法中 X射线空间 分布不均匀的立体示意图； 图 5B是是根据本发明实施例的 G型臂 X光机的三维影像生成方法中 X射线空间 分布不均匀的平面示意图； 图 6是根据本发明实施例的 G型臂 X光机的三维影像生成方法中两路 X射线不 一致性测试的示意图。 具体实施方式 需要说明的是， 在不冲突的情况下， 本申请中的实施例及实施例中的特征可以相 互组合。 下面将参考附图并结合实施例来详细说明本发明。 图 1A和图 IB是根据本发明实施例的 G型臂 X光机中的 G臂架位于初始角度状 态和目标角度状态的示意图， 如图 1所示， 不同于 C型臂的单路 X射线管， G型臂 X 光机固定设置有两路 X射线管 1A、 2A和与之对应设置的两路 X射线接收器 1B、 2B , G臂架 3为 3/4圆弧结构。 在 G臂架 3位于初始位置时， 第一 X射线管 1A用于发射 横向的锥束 X射线， 第一 X射线接收器 1B设置于 G臂架 3与所述第一 X射线管 1 A 相对的位置， 用于接收透过被测对象的横向的锥束 X射线； 第二 X射线管 2A用于发 射纵向的锥束 X射线， 第二 X射线接收器 2B， 设置于 G臂架 3与所述第二 X射线管 2A相对的位置， 用于接收透过检测对象的纵向的锥束 X射线。 在对被测对象扫描过 程中， 两路 X射线管 1A、 2A只需要同时逆时针或顺时针旋转 90°+y， 即 G臂架 3从 图 1A的状态旋转到图 1B的状态， 便可获得被测目标的 180°+2y透视图像数据， 比 C 型臂的图像获取时间节省了一半， 即被测对象的受照时间降低一半， 有效地提高了检 测效率。
G型臂 X光机的三维影像生成装置 4控制 G臂架 3旋转并在旋转过程中，获取第 一 X射线接收器 1B和第二 X射线接收器 2B接收到的二维投影数据， 并通过多个方 向的二维投影数据通过计算生成被测对象的三维影像。 其中第一 X射线管 1A与第一 X射线接收器 1B的连线和第二 X射线管 2A与第二 X射线接收器 2B的连线互相垂直， 被测对象置于 G臂架 3所在圆弧的圆心处。 该 G型臂 X光机包括两路 X射线管和两 路 X射线接收器、可绕被测对象旋转的 G臂架， 从而双向同时采集多个方位的投影数 据， 重建断层图像， 缩短了扫描时间， 提高了成像效率。 图 2是根据本发明实施例的 G型臂 X光机的三维影像生成装置示意图，如图 2所 示， 本发明实施例 G型臂 X光机的三维影像生成装置， 包括： 运动控制模块 21， 用 于控制 G臂架 3从初始角度旋转至目标角度； 影像数据采集模块 23，用于获取被测对 象在 G型臂 3处于不同角度时的多组二维投影数据， 其中每组二维投影数据包括两路 投影数据； 数据处理模块 25， 用于利用多组二维投影数据按照 FDK算法或 FDK修正 算法进行计算， 以得到被测对象的三维影像； 输出模块 27， 用于输出被测对象的三维 影像。 上述运动控制模块 21可以使用工控机、 PLC等控制装置实现， 来驱动旋转 G 臂架的电机； 影像数据采集模块 23，包括图像采集装置用于采集 X射线接收器的接收 图像， 转换为数字信号形式。 数据处理模块 25使用计算机、 数字处理器 （DSP) 等运 算功能强大的计算装置。 输出模块， 可以是显示器用于显示三维影像， 或者存储器， 用于保存所述三维影像数据以供后续分析使用。 获得被测对象的全貌三维信息至少需要对被测对象进行 180°+2y的 X射线扫描， 根据本发明实施例的 G型臂 X光机的双路 X射线扫描的结构， 只需要对 G臂架 3旋 转 90°+y就可以完成对被测目标的 180°+2y的扫描。 因此优选地可以设定初始角度至 目标角度之间的角度差为 90°+y。 一般而言， 获取的二维投影图像的数目越多， 生成 的三维影像质量更高， 但是扫描的效率以及数据处理的速度相对较慢， 所以根据生成 三维影像的具体要求可以得出需要获取的二维投影图像的数目， 假定每路 X射线接收 器需要获取的图像数目为 N，运动控制模块 21在初始角度至目标角度之间的方位设置 N个图像获取位置， 在 G臂架 3旋转过程中实时判断 G臂架的旋转角度， 影像数据采 集模块 23当 G臂架旋转至各个所述图像获取位置时， 通过两路 X射线接收器采集一 组二维投影数据， 这样在旋转过程中就可以得到 N组二维投影图像。 优选地， 可以保证每两个相邻的所述图像获取位置的角度相等。 将初始角度至目 标角度之间进行 N - 1等分，每个等分点位置加上初始角度位置和目标角度位置共得到 N个图像获取位置。 也就说每旋转 （90°+ /N角度， 两路第一 X射线接收器 1B、 2B 就分别获得该位置的一幅二维投影图像， 旋转 90°+y后就得到了 2N幅二维投影图像。 针对不同类型的被测对象， X射线的强度的大小需要进行调整， 因此本实施例的 G型臂 X光机的三维影像生成装置还可以包括 X射线发射控制模块， 用于在获取 X 射线管 1A、 IB的电流和电压的设置值； 并按照所述电流和电压的设置值启动两路 X 射线管 1A、 1B。在 G臂架 3旋转过程中， 保证 X射线管的电流值和电压值保持恒定， 从而使 X射线的强度保持稳定， 保证得到的二维投影图像亮度一致。 但是限于 X射线管的工艺水平， 不能保证中心射线束的光场强度等于其它位置处 的光场强度， 而这种光场强度的不一致性会引起每幅透视图像的灰度变化， 因此需要 对每路 X射线的光场不均匀性各自进行标定。 因此，本实施例的 G型臂 X光机的三维影像生成装置还可以设置射线强度校准模 块， 该射线强度校准模块用于对两路 X射线管 1A、 IB发出的 X射线束辐射强度的空 间分布进行测量以得出空间分布不均匀度函数。数据处理模块 25首先利用该空间分布 不均匀度函数对获取到的多组二维投影数据进行校准， 然后利用校准后的二维投影数 据按照 FDK算法或 FDK修正算法进行计算。 射线强度校准模块的工作流程为： 通过 两路 X射线接收器 1B、 2B分别采集两路 X射线管 1 A、 2A发出的 X射线束通过衰减 板后的投影亮度数据； 利用该投影亮度数据分别计算得出两路 X射线束的空间分布不 均匀度函数。 另外， X射线管的生产工艺并不能保证每个 X射线管在相同的电压电流情况下发 出的 X射线强度完全一致， 因此 G臂存在两路 X射线管 1A、 2A从发射窗口射出之 后的强度也不一致，这就导致两路透视图像的平均亮度不相同， 具体表现为一明一暗， 因此还需要得到两路 X在平均光场强度方面的关系， 并进行归一化处理， 以提高生成 的三维影像的质量。此时射线强度校准模块还用于分别计算两路 X射线束的平均辐射 强度， 数据处理模块 25根据所述两路 X射线束的平均辐射强度对多组二维投影数据 进行归一化计算； 然后利用空间分布不均匀度函数对进行归一化处理后的多组二维投 影数据进行校准， 并将校准后的数据用于 FDK算法计算。 经过上述处理的多组二维投影数据， 可以保证了不同 X射线接收器获取到图像的 一致性， 使生成的三维影像质量更高。 输出模块 27， 除了输出被测对象的三维影像外， 还可以利用数据处理模块 25得 出的三维影像数据对被测对象的 XZ断面、 YZ断面、 XY断面进行输出。 输出时还可 以将当前位置在三维目标中的坐标与三个断面处进行对应输出。在输出模块 27使用显 示装置的情况下， 可以将整个显示区域分为四块， 分别显示 XZ断面、 YZ断面、 XY 断面、 以及生成的三维影像。 本发明实施例还提供了一种 G型臂 X光机，包括本发明实施例上述内容所提供的 任一种 G型臂 X光机的三维影像生成装置。 本发明实施例还提供了一种 G型臂 X光机的三维影像方法，该方法可以通过本发 明上述实施例所提供的任一种三维影像生成装置来执行， 图 3是根据本发明实施例的 G型臂 X光机的三维影像方法的示意图， 如图 3所示， 本发明实施例的 G型臂 X光 机的三维影像生成方法包括： 步骤 S31， 控制 G臂架从初始角度旋转至目标角度， 在旋转过程中获取被测对象 在 G型臂处于不同角度时的多组二维投影数据， 其中每组二维投影数据包括两路投影 数据； 步骤 S33， 利用多组二维投影数据按照 FDK算法或 FDK修正算法进行计算， 以 得到被测对象的三维影像； 步骤 S35， 输出被测对象的三维影像。 根据生成三维影像的具体要求可以得出需要获取的二维投影图像的数目， 假定每 路 X射线接收器需要获取的图像数目为 N， 则步骤 S31中旋转过程中获取被测对象在 G型臂处于不同角度时的多组二维投影数据可以包括： 在初始角度至目标角度的范围 内设置 N个图像获取位置； 实时判断 G臂架的旋转角度； 当 G臂架旋转至各个图像 获取位置时，通过与两路 X射线管对应设置的两路 X射线接收器采集一组二维投影数 据。 每两个相邻的图像获取位置的角度可以设置为相等的角度， 具体方法为将初始角 度至目标角度之间进行 N - 1等分，每个等分点的位置加上初始角度位置和目标角度位 置共得到 N个图像获取位置。 获得被测对象的全貌三维信息至少需要对被测对象进行 180°+2y的 X射线扫描， 根据本发明实施例的 G型臂 X光机的双路 X射线扫描的结构， 只需要对 G臂架 3旋 转 90°+y就可以完成对被测目标的 180°+2y的扫描。 因此优选地可以设定初始角度至 目标角度之间的角度差为 90°+y。 此时按照等分的方式确定图像获取位置， 就可以保 证每旋转 （90°+ /N角度， 两路第一 X射线接收器 1B、 2B就分别获得该位置的一 幅二维投影图像， 旋转 90°+y后就得到了 2N幅二维投影图像。 为了保证 X射线的强度符合扫描被测对象的要求，在控制 G臂架从初始角度旋转 至目标角度之前还可以包括： 获取 X射线管的电流和电压的设置值； 按照电流和电压 的设置值启动两路 X射线管。 在 G臂架 3旋转过程中， 保证 X射线管的电流值和电 压值保持恒定， 从而使 X射线的强度保持稳定， 上述 X射线管的电流和电压的设置值 根据被测对象的类型不同， 灵活设定。 限于 X射线管的工艺水平， 不能保证中心射线束的光场强度与其它位置处的光场 强度完全相等， 而这种光场强度的不一致性会引起每幅透视图像的灰度变化， 因此需 要对每路 X射线的光场不均匀性各自进行标定。标定的具体流程为： 在控制 G臂架从 初始角度旋转至目标角度之前还包括：对两路 X射线管发出的 X射线束辐射强度的空 间分布进行测量以得出空间分布不均匀度函数， 那么上述步骤 S31中利用多组二维投 影数据按照 FDK算法或 FDK修正算法进行计算包括： 利用空间分布不均匀度函数对 多组二维投影数据进行校准； 利用校准后的二维投影数据按照 FDK算法或 FDK修正 算法进行计算。 其中，对两路 X射线管发出的 X射线束辐射强度的空间分布进行测量以得出空间 分布不均匀度函数的具体流程为：通过两路 X射线接收器分别采集两路 X射线管发出 的 X射线束通过衰减板后的投影亮度数据；利用投影亮度数据分别计算两路 X射线束 的空间分布不均匀度函数。下面结合附图对 X射线空间不均匀性的测试方法进行介绍： 图 4是根据本发明实施例的 G型臂 X光机的三维影像生成方法中锥束 X射线在 X 射线接收器上的投影示意图； 图 5A是是根据本发明实施例的 G型臂 X光机的三维影 像生成方法中 X射线空间分布不均匀的立体示意图， 图 5B是是根据本发明实施例的 G型臂 X光机的三维影像生成方法中 X射线空间分布不均匀的平面示意图。图中以第 一 X射线管 1 A和第一 X射线接收器 1B为例， 但第二 X射线管 2A和第二 X射线接 收器 2B使用同样的方式进行空间分布的测量。 在以上图中， 42为锥形 X射线束在 X射线接收器 1B上的投影范围， 0点为锥束 X射线的中心光束在 X射线接收器 1B的投影位置， （x， y)点为光束 2在 X射线接收 器 1B的投影位置， 光束 2与中心光束的夹角为^ 0点至 （x， y) 点的距离为 r， 51 为质地均匀的衰减板， 第一 X射线管 1A和第一 X射线接收器 1B的距离为 h， dr do 分别为光束 2和中心光束穿过衰减板 51的距离。 对第一 X射线管 1A， 在单位为 kV的不同电压值下的 X射线辐射强度分布是不 均匀的， 随着空间位置的不同而变化。 假定其在中心光束的强度为 IQ， 在 （x， y) 点 处的光束强度为 I， 如图 5所示。 该 X射线管发射的 X辐射强度不均匀度分布情况可 通过测量接收器接收的图像数据来获取。具体方法为： 在第一 X射线管和第一 X射线 接收器 1B之间垂直直于中心光束放置一质地均匀的衰减板 51， 测量 X射线接收器接 收的光场强度数据 Ix，y， 如图 5所示， 再将 X射线接收器接收的光场强度数据 Ix，y， 通 过滤波器对光场强度数据进行滤波后， 进行平滑处理， 得到处理后的光场强度数据 I(x，
当强度为 I的单能 X射线穿过结构均匀的衰减板后， 该射线束的衰减应符合 Beer 定律。 考虑到中心光束与光束 2的夹角关系^ 及光线穿透衰减板的路径长度 4、 do 关系， 可求得在坐标 (x,y)某 kV电压下 X射线管的出射光强不均匀度 p(x,y,kV)为：
Figure imgf000011_0001
其中 μ为衰减板 51在测试电压下的 X射线衰减系数， dQ为衰减板的厚度。 可见 X射线管的 X射线出射光场强度 p为位置 (x,y)的函数， 同时也是随电压变化的函数。 使用同样的方法可以测量第二 X射线管的空间分布不均匀度函数。 将 p(x,y,kV)制成三维矩阵， 其中前两维为坐标 (x,y)的值， 第三维为测试电压值。 逐渐改变测试电压的大小， 可得到一系列出射光强不均匀度随电压变化的准确数据， 两次电压变化之间的数据可通过插值方式确定。 从而得到空间分布不均匀度函数。 上 述步骤 S31中利用多组二维投影数据按照 FDK算法或 FDK修正算法进行计算时， 就 需要首先利用空间分布不均匀度函数对多组二维投影数据进行校准， 消除二维图像中 所有点的数据受空间分布的影响； 然后利用校准后的二维投影数据按照 FDK算法或 FDK修正算法进行计算。 另外， X射线管的生产工艺并不能保证每个 X射线管在相同的电压电流情况发出 的 X射线强度完全一致， 因此 G臂存在两路 X射线管 1A、 2A从发射窗口射出之后 的强度也不一致， 这就导致两路透视图像的平均亮度不相同， 具体表现为一明一暗， 因此还需要得到两路 X在平均光场强度方面的关系， 并进行归一化处理， 以提高生成 的三维影像的质量。 图 6是根据本发明实施例的 G型臂 X光机的三维影像生成方法中两路 X射线不 一致性测试的示意图， 通常情况下， 由于 X射线管的生产工艺限制， 两路 X射线管并 不能保证完全相同。 因此， 即使设置相同的输入信号， 两路 X射线管的 X射线辐射强 度除了不均匀之外， 其平均辐射强度也不相同。 因此， 还需要确定这两路 X射线辐射 强度的不一致程度， 并通过补偿消除这种不一致程度。 如图 6所示， 在相同的输入条 件下， 将同一衰减板 51分别置于两路 X射线发射源与 X接收器之间， 且垂直于 X射 线束， 测量 X射线接收器接收的光场强度数据， 并对光场强度数据进行滤波， 分别得 到第一路 X射线平均辐射数据 I x'y)和第二路 X射线辐射数据 r2(x,y)。 根据 Beer定律及不均匀 强度 I (x,y,kV)，再根据下式计算每路 平均辐射数据 Iare: Iave {kV) = y, kV)dn , 其中 y 为锥束 X射线的半
Figure imgf000012_0001
张角大小， Ω为弧度积分空间。 从而利用该方法可以求得第一路 X 射强度数据 Iavel(kV)和第二路 X射 线平均辐射强度数据 Iare2(kV)。令;；( 可求得两路 X射线平均辐射强度
Figure imgf000012_0002
之间的关系， 从而利用; 7(« 则可以将将双路 X射线束投影归一化为在 Iavel(kV)单独 作用下的投影。 那么本发明实施例的 G型臂 X光机的三维影像生成方法利用投影亮度数据分别计 算两路 X射线束的空间分布不均匀度函数之后还可以包括：分别计算两路 X射线束的 平均辐射强度， 从而利用空间分布不均匀度函数对多组二维投影数据进行校准包括： 根据两路 X射线束的平均辐射强度对多组二维投影数据进行归一化计算； 利用空间分 布不均匀度函数对进行归一化处理后的组二维投影数据进行校准。 根据本发明的技术方案， G型臂 X光机的三维影像生成方法包括： 控制 G臂架从 初始角度旋转至目标角度， 在旋转过程中保持两路 X射线管的电流和电压不变； 获取 被测对象在 G型臂处于不同角度时的多组二维投影数据， 其中每组二维投影数据包括 两路投影数据； 利用多组二维投影数据按照 FDK算法或 FDK修正算法进行计算， 以 得到被测对象的三维影像； 输出被测对象的三维影像。 从而通过获取两路投影数据， 大大减少了数据的获取时间， 有效降低了被测对象在 X射线下的照射时间， 直接输出 被测对象的三维图像， 反映了被测对象的全貌信息。 显然， 本领域的技术人员应该明白， 上述的本发明的各模块或各步骤可以用通用 的计算装置来实现， 它们可以集中在单个的计算装置上， 或者分布在多个计算装置所 组成的网络上， 可选地， 它们可以用计算装置可执行的程序代码来实现， 从而， 可以 将它们存储在存储装置中由计算装置来执行， 或者将它们分别制作成各个集成电路模 块， 或者将它们中的多个模块或步骤制作成单个集成电路模块来实现。 这样， 本发明 不限制于任何特定的硬件和软件结合。 以上仅为本发明的优选实施例而已， 并不用于限制本发明， 对于本领域的技术人 员来说， 本发明可以有各种更改和变化。 凡在本发明的精神和原则之内， 所作的任何 修改、 等同替换、 改进等， 均应包含在本发明的保护范围之内。

Claims

权 利 要 求 书
1. 一种 G型臂 X光机的三维影像生成方法， 其特征在于， 包括：
控制 G臂架从初始角度旋转至目标角度， 在旋转过程中获取被测对象在 G 型臂处于不同角度时的多组二维投影数据， 其中每组所述二维投影数据包括两 路投影数据；
利用所述多组二维投影数据按照 FDK算法或 FDK修正算法进行计算， 以 得到所述被测对象的三维影像；
输出所述被测对象的三维影像。
2. 根据权利要求 1所述的三维影像生成方法， 其特征在于， 在旋转过程中获取被 测对象在 G型臂处于不同角度时的多组二维投影数据包括：
在所述初始角度至所述目标角度的范围内设置 N个图像获取位置； 实时判断 G臂架的旋转角度；
当 G臂架旋转至各个所述图像获取位置时，通过与所述两路 X射线管对应 设置的两路 X射线接收器采集一组二维投影数据。
3. 根据权利要求 2所述的三维影像生成方法， 其特征在于， 每两个相邻的所述图 像获取位置的角度相等。
4. 根据权利要求 1所述的三维影像生成方法， 其特征在于， 所述初始角度至所述 目标角度之间的角度差为 90°+γ， 其中 γ为所述 X射线管发射的 X射线束的半 张角。
5. 根据权利要求 1所述的三维影像生成方法， 其特征在于， 在控制 G臂架从初始 角度旋转至目标角度之前， 还包括：
获取所述 X射线管的电流和电压的设置值；
按照所述电流和电压的设置值启动两路 X射线管。
6. 根据权利要求 1至 5中任一项所述的三维影像生成方法， 其特征在于，
在控制 G臂架从初始角度旋转至目标角度之前还包括： 对两路 X射线管发出的 X射线束辐射强度的空间分布进行测量以得出空间 分布不均匀度函数，
利用所述多组二维投影数据按照 FDK算法或 FDK修正算法进行计算包括: 利用所述空间分布不均匀度函数对所述多组二维投影数据进行校准； 利用校准后的二维投影数据按照 FDK算法或 FDK修正算法进行计算。
7. 根据权利要求 6所述的三维影像生成方法， 其特征在于， 对两路 X射线管发出 的 X射线束辐射强度的空间分布进行测量以得出空间分布不均匀度函数包括： 通过所述两路 X射线接收器分别采集所述两路 X射线管发出的 X射线束 通过衰减板后的投影亮度数据；
利用所述投影亮度数据分别计算两路所述 X射线束的空间分布不均匀度函 数。
8. 根据权利要求 7所述的三维影像生成方法， 其特征在于， 利用所述投影亮度数据分别计算两路所述 X射线束的空间分布不均匀度函 数之后还包括： 分别计算两路 X射线束的平均辐射强度，
利用所述空间分布不均匀度函数对所述多组二维投影数据进行校准包括： 根据所述两路 X射线束的平均辐射强度对所述多组二维投影数据进行归一 化计算；
利用所述空间分布不均匀度函数对进行归一化处理后的多组二维投影数据 进行校准。
9. 一种 G型臂 X光机的三维影像生成装置， 其特征在于， 包括：
运动控制模块， 用于控制 G臂架从初始角度旋转至目标角度； 影像数据采集模块，用于获取被测对象在 G型臂处于不同角度时的多组二 维投影数据， 其中每组所述二维投影数据包括两路投影数据；
数据处理模块， 用于利用所述多组二维投影数据按照 FDK算法或 FDK修 正算法进行计算， 以得到所述被测对象的三维影像；
输出模块， 用于输出所述被测对象的三维影像。
10. 根据权利要求 9所述的三维影像生成装置， 其特征在于， 还包括： 射线强度校准模块，用于对两路 X射线管发出的 X射线束辐射强度的空间 分布进行测量以得出空间分布不均匀度函数。
11. 一种 G型臂 X光机， 其特征在于， 包括如权利要求 9或权利要求 10所述的 G 型臂 X光机的三维影像生成装置。
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