COMPUTED-TOMOGRAPHY METHOD AND DEVICE

Abstract

An imaging method comprises the steps of: putting an object in a detection region, and biasing a detector (1-8) relative to the object; moving an imaging system along a longitudinal Z axis, enabling a ray source (1-7) and the detector (1-8) to synchronously perform circular movement around the object, performing scanning and data collection, and supplementing the data; and reconstructing the collected data to obtain a complete object image. The imaging method combines detector biasing and spiral scanning, solves the problem that an image splicing method used in conventional CT imaging generates artifacts, reduces the usage area of the detector, and reduces system cost.

Claims

1. An imaging method, comprising: putting an object in a detection region, and biasing a detector relative to the object, to make a portion of data of scanning the object with a ray source be obtained by the detector; moving an imaging system which consists of the ray source and the detector along a longitudinal Z axis, enabling the ray source and the detector to synchronously perform circular movement around the object, and performing scanning and data collection; and reconstructing collected data to obtain a complete object image.

2. The imaging method according to claim 1, further comprising: when the collected data is constructed, supplementing the collected data, wherein supplementing the collected data comprises: at an angle of α.sub.1, projection data of a point f(x,h) in a region to be reconstructed being not collected by the detector; a focus of the ray source at the angle of α.sub.1 and the point f(x,h) in the region to be reconstructed being connected to form a straight line, where an angle between the straight line and a line defined by the focus of the ray source at the angle of α.sub.1 and a rotation center of an imaging system is Δα; and to supplement missing data of the point f(x,h) at the angle of α.sub.1, when the ray source moves to a position α.sub.2, using measurement values at a position where the straight line is intersected with the detected to perform data supplement, where α.sub.2=α.sub.1+180°±Δα, and the imaging system comprises the ray source and the detector.

3. The imaging method according to claim 1, wherein a maximum rate of the object moving along the longitudinal Z axis is p/t, where p is a height of the detector in the Z-axis direction, and t is a time period for the ray source and the detector to rotate 360 degrees.

4. The imaging method according to claim 1, wherein the ray source and the detector rotate at least 360 degrees around the object.

5. The imaging method according to claim 1, wherein a line defined by a focus of the ray source and a center of the ray source and the detecting component is intersected with the detector, and the detecting component comprises the detector.

6. The imaging method according to claim 1, wherein the object is a living body who stands within the detection region.

7. The imaging method according to claim 1, wherein the object is a person who stands or sits within the detection region.

8. An imaging method, comprising: putting an object in a detection region and biasing a detector relative to the object, to make a portion of data of scanning the object with a ray source be obtained by the detector; according to requirements of two-dimensional projection imaging range, repeating the following steps to adjust an imaging range and performing image splicing, so as to realize target imaging region positioning, where the following steps comprise: i) first, adjusting a position of the detector and obtaining, from the detector, data of a first projection of the object by the ray source, moving the detector in a horizontal direction or moving an imaging system (comprising the ray source and the detector) in a vertical direction to obtain data of a second projection of the object by the ray source to supplement data that was not acquired in the first projection; combining the data of the first projection with the data of the second projection; and if a first desired projection image is not obtained, continuing repeating the step i) to collect more projection images at different positions until the first desired projection image is obtained; ii) afterwards, rotating the ray source together with a detecting component by 90 degrees relative to the object; and iii) afterwards, adjusting the position of the detector according to the step i) and obtaining, from the detector, data of a third projection of the object by the ray source, moving the detector in the horizontal direction or moving the imaging system (comprising the ray source and the detector) in the vertical direction to obtain data of a fourth projection of the object by the ray source to supplement data that was not acquired in the third projection; combining the data of the third projection with the data of the fourth projection; and if a second desired projection image is not obtained, continuing repeating the step iii) to meet requirements of target imaging region positioning under a current degree; moving the object along a longitudinal Z axis, enabling the ray source and the detector to synchronously perform circular movement around the object, and performing scanning and data collection; and reconstructing the collected data to obtain a complete object image.

9. The imaging method according to claim 8, further comprising: when the collected data is constructed, supplementing the collected data, wherein supplementing the collected data comprises: at an angle of α.sub.1, projection data of a point f(x,h) in a region to be reconstructed being not collected by the detector; a focus of the ray source at the angle of α.sub.1 and the point f(x,h) in the region to be reconstructed being connected to form a straight line, where an angle between the straight line and a line defined by the focus of the ray source at the angle of α.sub.1 and a rotation center of an imaging system is Δα; to supplement missing data of the point f(x,h) at the angle of α.sub.1, when the ray source moves to a position α.sub.2, using measurement values at a position where the straight line is intersected with the detected to perform data supplement, where α.sub.2=α.sub.1+180°±Δα, and the imaging system comprises the ray source and the detector.

10. The imaging method according to claim 8, wherein a maximum rate of the object moving along the longitudinal Z axis is p/t, where p is a height of the detector in the Z-axis direction, and t is a time period for the ray source and the detector to rotate 360 degrees.

11. The imaging method according to claim 8, wherein the ray source and the detector rotate at least 360 degrees around the object.

12. The imaging method according to claim 8, wherein a line defined by a focus of the ray source and a center of the ray source and the detecting component is intersected with the detector, and the detecting component comprises the detector.

13. The imaging method according to claim 8, wherein the object is a living body who stands within the detection region.

14. The imaging method according to claim 8, wherein the object is a person who stands or sits within the detection region.

15. The imaging method according to claim 1, wherein the detector is a flat panel detector.

16. An imaging device configured to implement the imaging method according to claim 1, comprising: a frame body, configured to move upward or downward; a rotation frame which is flexibly connected with the frame body and comprises a sliding rail structure; a data transmission component which is disposed at a joint between the frame body and the rotation frame and connected with a power line and a data line respectively; a ray source disposed on the rotation frame; and a detector which slides on the sliding rail structure.

17. The imaging device according to claim 16, wherein the sliding rail structure comprises at least one sliding rail.

18. The imaging method according to claim 16, wherein the joint between the frame body and the rotation frame is a rotation center, and when the rotation frame rotates, an area covered by the ray source and the detector always surrounds the rotation center.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 schematically illustrates a structural diagram of an imaging device which implements an imaging method according to an embodiment of the present disclosure;

[0037] FIG. 2 schematically illustrates a structural diagram of a data transmission component shown in FIG. 1 according to an embodiment of the present disclosure;

[0038] FIG. 3 schematically illustrates a structural diagram of a detector shown in FIG. 1 according to an embodiment of the present disclosure;

[0039] FIG. 4 schematically illustrates a CT diagram of imaging data of a first projection of the object by the ray source obtained from the detector according to an embodiment of the present disclosure;

[0040] FIG. 5 schematically illustrates a CT diagram of imaging data of a second projection of the object by the ray source obtained from the detector according to an embodiment of the present disclosure;

[0041] FIG. 6 schematically illustrates combining the data of the first projection with the data of the second projection to obtain a complete projection image;

[0042] FIG. 7 schematically illustrates a diagram of performing bias scanning and imaging to an object according to an embodiment of the present disclosure;

[0043] FIG. 8 schematically illustrates a diagram of supplementing missing data for one-side bias scanning when an imaging method provided in an embodiment of it) the present disclosure is employed;

[0044] FIG. 9 schematically illustrates a trajectory diagram of scanning an object by using an imaging method provided in an embodiment of the present disclosure;

[0045] FIG. 10 schematically illustrates a projection image which is generated by imaging data collected by scanning an object using an imaging method provided in an embodiment of the present disclosure; and

[0046] FIG. 11 schematically illustrates a flow chart of an imaging method according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0047] Technical solutions of the present disclosure are described in detail in conjunction with accompanying figures. Embodiments of the present disclosure are used to describe but not limit the technical solutions of the present disclosure. Although the present disclosure is described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present disclosure can be modified or equivalently replaced without departing from the spirit and scope of the present disclosure, which should be contained in the scope of claims of the present disclosure.

[0048] FIG. 1 schematically illustrates a structural diagram of an imaging device which implements an imaging method according to an embodiment of the present disclosure, FIG. 2 schematically illustrates a structural diagram of a data transmission component shown in FIG. 1 according to an embodiment of the present disclosure, and FIG. 3 schematically illustrates a structural diagram of a detector shown in FIG. 1 according to an embodiment of the present disclosure. Referring to FIGS. 1, 2 and 3, a CT scanning system (for example, a cone-shaped beam CT) is designed to include an imaging part (1-2) and a pillar part (1-1). The imaging part (1-2) is a sliding structure in the pillar part (1-1), which can move upward and downward in a vertical direction.

[0049] A power line (1-5) and a data line (1-6) are connected via a slip ring system (1-3) instead of a conventional wire, so that a detecting component (1-4) and a ray source (1-7) can continuously rotate around an object to prevent wire entanglement.

[0050] The detecting component (1-4) includes two parallel guide rails (1-9), and a detector (1-8) slides on the two parallel guide rails (1-9). In some embodiments, the guide rails may be a sliding rail structure which facilitates adjusting a horizontal position of the detector for full-field imaging, to solve a positioning problem caused by biasing the detector. An area of the detector (1-8) may be smaller than an area between the two parallel guide rails (1-9). In some embodiments, the detector (1-8) may be a cone-shaped beam CT flat panel detector with a length of 18 cm and a width of 7 cm. During a CT scanning process, the imaging part moves, and the detector and the ray source rotate around the object, to realize spiral scanning.

[0051] FIG. 7 schematically illustrates a diagram of performing bias scanning and imaging to an object according to an embodiment of the present disclosure. The detector of the CT imaging system is placed biased relative to the object, and a line defined by a focus (3-1) of the ray source and a center (3-3) of the ray source and the detecting component is intersected with a flat panel detector (3-2). Referring to FIGS. 1, 3 and 7, the detector (1-8) is fixed on a guide rail in an X direction, and the flat panel detector (1-8) is electrically controlled to move along the guide rails (1-9). The detector (1-8) is biased, that is, the detector is biased to one side of the X direction, where a circular shaded portion is a target region (2-4) to be performed with image reconstruction. During a CT scanning process, the imaging part (1-2) moves along a longitudinal Z axis. Meanwhile, the ray source (1-7) and the detecting component (1-4) perform circular movement around the object. X rays are exposed and data is collected, where a scanning trajectory is shown in FIG. 9. In some embodiments, the object may be a person who stands or sits within the detection region.

[0052] A maximum rate of the object moving along the longitudinal Z axis is p/t, where p is a height of the detector in the Z-axis direction, and t is a time period for the ray source and the detector to rotate 360 degrees. For example, if the height of the detector in the Z-axis direction is 7 cm, and the time period for CT scanning of a circle is 10 seconds, a movement rate of the object during the CT scanning process is 0.7 cm per second. A rotation rate of the ray source and the detector is 36 degrees per second.

[0053] Referring to FIG. 7, the ray source emits X rays (3-1), and the detector detects X-ray signals (3-2) and performs continuous circular movement around the object to be scanned, until a moving distance of the imaging part of the CT scanning system completely covers the object to be scanned and the ray source rotates at least 360 degrees. A rotation center of the circular movement performed by the ray source and the detector can be referred to the point (1-0) in FIG. 1 or the point (3-3) in FIG. 7. A data collection system consisting of the ray source and the detector does not need to completely cover the whole plane to be imaged. Instead, it only needs to ensure that, during the rotation along the rotation center, an area covered by the ray source and the detector always includes the rotation center.

[0054] FIG. 9 schematically illustrates a trajectory diagram of CT scanning using an imaging method provided in an embodiment of the present disclosure. At a same angle of the ray source, with the movement of the object along the longitudinal Z axis, different portions (Z1, Z2 and Z3) of the object are scanned. Projections data is collected by the detector and further imaged, as shown in FIG. 10.

[0055] To image objects with different specifications or perform imaging using detectors with different specifications, whether the object is located at a central imaging region is detected. FIG. 4 schematically illustrates features of an image formed in bias spiral CT. As an area of the detector is relatively small, imaging of one time cannot cover a horizontal structure of a complete object but only covers a first partial feature (2-1). The flat panel detector slides along the slide rails to perform another imaging, to obtain a second partial feature (2-2) (referring to FIG. 5). The second partial feature can supplement content that was not presented in the first partial feature. The results in the two imaging processes are combined to obtain a complete head projection image (2-3) (referring to FIG. 6). A projection image with the ray source at a direction of 90° may be obtained in a similar way, to determine whether the object is located in the central imaging plane.

[0056] FIG. 11 schematically illustrates a flow chart of an imaging method according to an embodiment of the present disclosure. The imaging method includes:

[0057] step 10, putting an object in a detection region and biasing a detector relative to the object, to make a portion of data of scanning the object with a ray source be obtained by the detector;

[0058] according to requirements of two-dimensional projection imaging range, adjusting an imaging range and performing image splicing, so as to realize target imaging region positioning;

[0059] where the above step includes:

[0060] step 211, adjusting a position of the detector and obtaining, from the detector, data of a first projection of the object by the ray source; step 212, moving the detector in a horizontal direction or moving an imaging system (including X ray source and X-ray detector) in a vertical direction to obtain data of a second projection of the object by the ray source to supplement data that was not acquired in the first projection; step 213, combining the data of the first projection with the data of the second projection to obtain a complete projection image; and if a first desired projection image is not obtained, continuing repeating the steps 221 to 223 to collect more projection images at different positions until the first desired projection image is obtained;

[0061] afterwards, step 221, rotating the ray source together with a detecting component by 90 degrees relative to the object; and

[0062] afterwards, step 231, obtaining, from the detector, data of a third projection of the object by the ray source; step 232, moving the detector in the horizontal direction or moving the imaging system (including the X ray source and the X-ray detector) in the vertical direction to obtain data of a fourth projection of the object by the ray source to supplement data that was not acquired in the third projection; S233, combining the data of the third projection with the data of the fourth projection to obtain a complete projection image at a position where the ray source is rotated by 90 degrees; and if a second desired projection image is not obtained, continuing repeating the steps 231 to 233 to meet requirements of target imaging region positioning under a current degree;

[0063] step 30, moving the object along a longitudinal Z axis, enabling the ray source and the detector to synchronously perform circular movement around the object, and performing X-ray scanning and data collection; and

[0064] step 40, reconstructing the collected data to obtain a complete object image.

[0065] During image reconstruction, data needs to be supplemented.

[0066] In the embodiments, as the detector has a relatively small size, projection imaging at one angle cannot cover a complete target imaging region. Thus, three-dimensional volume data reconstruction strategy based on contralateral image supplement is employed. FIG. 8 schematically illustrates a diagram of supplementing missing data for one-side bias scanning when the imaging method provided in the embodiment of the present disclosure is employed. Referring to FIG. 8, when the ray source moves to an angle of α.sub.1 and a position of h.sub.1 (4-1), X ray signals can be detected by the detector only at a partial region (4-4) in FIG. 4, while there is no detector for a plane indicated by a region (4-5) in FIG. 4 to perform data collection. To supplement missing signals of the region (4-5), the ray source should rotate to other positions to enable the detector to collect projection data for supplement. Take missing data supplement shown as dotted line (4-2) in FIG. 4 as an example. When the ray source is located at an original position (α.sub.1, h.sub.1), as a horizontal size of the detector is not great enough to cover the whole imaging plane, projection data of the ray source at the original position (α.sub.1, h.sub.1) is supplemented by projection data of the ray source at a position α.sub.2 (4-3), which is shown as dotted lines in FIG. 4. The dotted line (4-2) in FIG. 4 should be intersected with the ray source at the position α.sub.2 and a plane where the detector corresponding to the ray source at the position α.sub.2 is located.

[0067] The above procedure can be interpreted as follows. At the angle of α.sub.1, projection data of a point f(x,h) in a region to be reconstructed is not collected by the detector. In this situation, a focus of the ray source at the angle of α.sub.1 and the point f(x,h) in the region to be reconstructed are connected to form a straight line. An angle between the straight line and a line defined by the focus of the ray source at the angle of α.sub.1 and a rotation center of the imaging system is Δα. To supplement missing data of the point f(x,h) at the angle of α.sub.1, when the ray source moves to the position α.sub.2 (α.sub.2=α.sub.1+180°±Δα), measurement values at a position where the straight line is intersected with the detected are used to perform data supplement. When the ray source is taken as the vision, the detector is out of sight at its right view, and the ray source rotates rightward, projection data at the angle of α.sub.2=α.sub.1+180°−Δα is obtained; when the ray source is taken as the vision, the detector is out of sight at its right view, and the ray source rotates leftward, projection data at the angle of α.sub.2=α.sub.1+180°+Δα is obtained; when the ray source is taken as the vision, the detector is out of sight at its left view, and the ray source rotates leftward, projection data at the angle of α.sub.2=α.sub.1+180°−Δα is obtained; when the ray source is taken as the vision, the detector is out of sight at its left view, and the ray source rotates rightward, projection data at the angle of α.sub.2=α.sub.1+180°+Δα is obtained

[0068] The supplemented data may be used for filtering. With NVIDIA's graphics computing card and CUDA parallel computing technology, in accordance with the classic filter back projection reconstruction algorithm, three-dimensional volume data is reconstructed. The three-dimensional volume data reconstruction includes two parts, image filtering and back projection. In the image filtering, complete projection data obtained by the method described in the above supplement strategy is used to filter; and in the back projection step, only the filtered data directly measured at each angle is used for back projection, while the data supplemented by the supplement strategy is not subjected to the back projection.

[0069] Currently, although some cone-shaped beam CT enterprise has used a translation method of a ray source and a detector to perform CT scanning on two positions and then perform image slicing to achieve long Z-axis coverage, the method requires additional movement of a scanning device. As a result, the overall scan time period is increased, and it is prone to cause unnecessary movement artifacts in the image.

[0070] Some cone-shaped beam CT enterprise employs a detector biasing method to expand an imaging view. However, the method only expands the imaging view on an X-Y plane but cannot expand the imaging view in a Z direction. Embodiments of the present disclosure provide methods which combine detector biasing with spiral scanning and expand imaging views on both an X-Y plane and a Z direction. Further, a large view projection imaging can be realized using a flat panel detector with a relatively small area.