CN-121978746-A - Detector ring, computer tomography apparatus and method for determining sampling parameters thereof

CN121978746ACN 121978746 ACN121978746 ACN 121978746ACN-121978746-A

Abstract

The detector ring of a computer tomography apparatus is formed by a plurality of detector units (10) arranged along the circumferential direction thereof, and the detection surface of each detector unit (10) is parallel to the axis (L) of the detector ring. Adjacent sides (11) of adjacent two detection surfaces are arranged parallel to and opposite each other, which sides are inclined with respect to the axis of the detector ring. The detector ring enables the computed tomography apparatus to effectively eliminate ring artifacts. The invention also provides a computer tomography device comprising the detector ring and a method for determining sampling parameters of the computer tomography device.

Inventors

HUANG YIXING
LIU FENGLIN
WANG AO
YU HAIJUN

Assignees

北京大学

Dates

Publication Date: 20260505
Application Date: 20260209

Claims (11)

1. Detector ring for a computed tomography apparatus, characterized in that the detector ring is formed by a plurality of detector units (10) arranged in its circumferential direction, the detection surface of each detector unit (10) being parallel to the axis (L) of the detector ring, adjacent sides (11) of two adjacent detection surfaces being arranged parallel to and opposite each other, the sides (11) being inclined with respect to the axis of the detector ring.
2. The detector ring of claim 1, wherein the side edges are inclined at an angle relative to the axis 45 DEG or less.
3. Computer tomography apparatus, characterized by comprising a detector ring according to any of claims 1 to 2.
4. A computed tomography apparatus as claimed in claim 3, characterized in that the computed tomography apparatus is a circumferential computed tomography apparatus, a helical computed tomography apparatus or a multisource static computed tomography apparatus, the normalized pitch of the computed tomography apparatus Calculated by formula (1): (1) Wherein, the In order to scan the moving distance of the inspection bed along the Z-axis direction during one circle, the Z-axis is a coordinate axis parallel to the axis of the detector ring in a space rectangular coordinate system O-XYZ and passes through the circle center of a ray source rotation track, the origin of the space rectangular coordinate system is fixed relative to the position of the inspection bed, and the X-axis is parallel to the width direction of the inspection bed; for the maximum coverage height of the ray in the Z-axis during one scan, it is calculated by equation (2): (2) In the formula (2), the amino acid sequence of the formula (2), Is the radius of the circle where the rotation track of the ray source is located, Is the theoretical radius of the detector ring, is the radius of the circle in which the center of each detector unit (10) is located, For each of said detector units (10) an effective height in the Z-axis direction, , wherein, For each of the detector units (10) the number of pixels in the Z-axis direction, Is the height of a single said pixel in said detector unit (10) in the Z-axis direction when not tilted.
5. A computed tomography apparatus as claimed in claim 4, wherein, When the computed tomography apparatus is a circumferential computed tomography apparatus, the normalized pitch is 0; When the computed tomography apparatus is a helical computed tomography apparatus, the normalized pitch , Wherein, the To scan the coverage height of the ray at the X-axis coordinate R along the Z-axis direction during one revolution, Calculated by formula (3): (3) or When the computed tomography apparatus is a multisource static computed tomography apparatus, the normalized pitch , Wherein, the To scan the coverage height of the ray at the X-axis coordinate R along the Z-axis direction during one revolution, Calculated by formula (4): (4) In the formula (4), the amino acid sequence of the compound, Is the offset distance along the Z axis between the plane of the rotation track of the ray source and the plane of the center of each detector unit (10).
6. A method of determining sampling parameters of a computed tomography apparatus as claimed in any one of claims 3 to 5, characterized in that the method of determining comprises: establishing a space rectangular coordinate system, wherein the origin of the space rectangular coordinate system is fixed relative to the position of the examination bed, the coordinate axis which passes through the center of a circle where the rotation track of the ray source is positioned and is parallel to the axis of the detector ring is a Z axis, the width direction which is parallel to the examination bed is an X axis, and Based on the space rectangular coordinate system, sampling parameters are obtained through a constructed ray parameter equation.
7. The method for determining the spatial rectangular coordinate system according to claim 6, wherein the sampling parameters are an effective view angle number and an angle sparsity, and the step of obtaining the sampling parameters by a constructed ray parameter equation based on the spatial rectangular coordinate system specifically comprises: Constructing a ray parameter equation based on the space rectangular coordinate system and solving to obtain an effective view index set, wherein elements in the effective view index set are effective views, under a certain effective view, a certain point x on the detected object can be hit by rays and the emergent rays can hit effective pixels of the detector unit to generate scanning data for imaging, and And calculating the effective view number and the angle sparsity according to the effective view index set, wherein the effective view number is the number of the effective views hitting all x points in the effective view index set, and the angle sparsity is the normalized variance of the angle interval between two adjacent effective views.
8. The method of determining as in claim 7, wherein the ray parameter equation Represented by formula (5): (5) Wherein, the For the angle of view of the same angle The position of the corresponding source in the space rectangular coordinate system is represented by formula (6): (6), In the formula (6), the amino acid sequence of the compound, Is the radius of the circle where the rotation track of the ray source is located, For the angle of view of the same angle The included angle between the connecting line of the corresponding ray source and the origin of coordinates O and the positive axis of the X-axis, For the s-th angular view of the c-th scan cycle, In order to scan the number of weeks, For each angular view of equal angles per scan cycle, Represented by formula (7): (7), In the formula (7), the amino acid sequence of the compound, At the start angle of week 0, For each of the scan Zhou Naxiang adjacent view angle step sizes, For an overall rotation increment between two adjacent scan cycles, For the angle of view of the same angle The Z-axis coordinate of the corresponding radiation source, For a circumferential computed tomography apparatus, , For a helical computed tomography apparatus, , For a multi-source static computed tomography apparatus, , Wherein: For the angle of view of the same angle The Z-axis coordinate of the corresponding source at the start position, A distance of movement of the examination couch along the Z-axis direction during one scan; At said equiangular viewing angle for the ith detector element Lower (th) The position coordinates of the centers of the individual pixels are expressed by the formula (8): (8) In the formula (8), the amino acid sequence of the compound, To be able to be viewed from the same angular angle The center position coordinates of the i-th said detector unit hit by the ray emitted by the corresponding ray source are expressed by formula (9): (9) In the formula (9), the amino acid sequence of the compound, The theoretical radius of the detector ring is the radius of the circle in which the center of each detector unit is located, In order to be in the X-O-Y plane, the azimuth angle of the center of the ith detector unit is the angle of view between the line connecting the center of the ith detector unit and the origin of coordinates O and the same angle The included angle of the connecting line of the corresponding ray source and the origin of coordinates O, Is the offset distance along the Z axis between the plane of the rotation track of the ray source and the plane of the center of each detector unit, For the pixel index of the center of the i-th said detector unit, The width of each of the pixels in the detector unit in the direction perpendicular to the Z-axis when not tilted, Is the height of each of the pixels in the detector unit in the Z-axis direction when not tilted, To tilt the detector unit in the width direction Is used for the unit step vector of (a), For the detector unit after tilting in the height direction Is used for the unit step vector of (a), For the angle of inclination to be the same, And Represented by the respective formulas (10) and (11): (10) (11) Wherein, the Is a tangential unit vector, the tangential direction is perpendicular to the Z-axis direction, , Is an axial unit vector which is parallel to the Z-axis direction, 。
9. The determination method of claim 8, wherein the set of active view indices Represented by formula (12): (12) Wherein, the I is the index sequence of the detector units on the detector ring, Indexing pixels on each of the detector cells, pixels For the pixel located in the m-th row and n-th column of the i-th said detector cell, Is shown at the angle of equal angles The angle of view is at the same angle The radiation emitted by the corresponding radiation source is able to hit the pixel of the i-th said detector unit ; A set of active pixel indices for an i-th said detector cell; To be at the angle of the equal angle From the angle of the equal angle The corresponding source is directed to the pixel of the i-th said detector unit Is used for the radiation parameter equation of (a), For the length of the sheet, the sheet is, Indicating whether or not the point on the subject can be viewed from the equiangular perspective The lower hit is solved.
10. The method of determining as recited in claim 9 wherein said effective number of views For the number of elements in the set of effective view indices, represented by equation (13): formula (13).
11. The method of determining according to claim 10, wherein the angular sparsity Represented by formula (14): (14) Wherein, the For ideal uniform sampling, the angular separation between adjacent two effective viewing angles, ; For non-ideal uniform sampling, the angular separation between adjacent two effective viewing angles is represented by equation (15): (15) In the formula (15), the amino acid sequence of the compound, To spot the object to be inspected Is used to determine the viewing angle of the (i) th active viewing angle, Wherein 。

Description

Detector ring, computer tomography apparatus and method for determining sampling parameters thereof Technical Field The present invention relates to the field of computed tomography, and in particular, to a detector ring, a computed tomography apparatus including the detector ring, and a method for determining sampling parameters of the computed tomography apparatus. Background Computed tomography (Computed Tomography, CT) has been the core tool for modern medical diagnostics and industrial detection since 1971 by Hounsfield's invention as a non-invasive imaging technique. Early circumferential computed tomography (RCT) apparatus required a single revolution of the source-detector ring around the object to acquire data, and then the couch was moved stepwise in the Z-axis direction, which was suitable for static imaging but inefficient. A Helical Computed Tomography (HCT) device introduced in the 90 s of the 20 th century forms a helical trajectory by a combination of source-detector ring rotation and continuous couch movement, enabling faster data acquisition and continuous volume imaging. Multisource stationary computed tomography (ct) apparatus (MSSCT) represents a more advanced architecture, employing multiple stationary sources (e.g., 24 or more) distributed around the circumference of the source ring, combined with couch motion and source activation sequences, to achieve parallel acquisition without mechanical rotation, thereby reducing motion-induced image blurring and being suitable for dynamic imaging. To meet the requirement of large field imaging, detector stitching technology is becoming a core means of expanding the performance of computed tomography devices. The technology skillfully avoids the process and cost bottleneck of manufacturing the giant monomer detector by precisely arranging a plurality of detector units with standard sizes to form a large-scale array. In the conventional apparatus, MSSCT as shown in fig. 1 is taken as an example, a plurality of ray sources are uniformly arranged to form a ray source ring, which is coaxial with the detector ring, and their axes L coincide with the Z axis in the space rectangular coordinate system O-XYZ, the origin of the space rectangular coordinate system being a certain point fixed with respect to the position of the examination table, for example, the geometric center of the object under examination, the X axis being parallel to the width direction of the examination table, and the Y axis being perpendicular to both the X axis and the Z axis. The detector units are usually formed into a detector ring by means of vertical stitching, i.e. in the detector ring, the detector units are arranged vertically in the circumferential direction of the detector ring, as shown in the partially expanded view of the 5 detector units shown in the lower right part of fig. 1, with the sides 11 of the detector units being parallel to the Z-axis. The layout has simple structure and easy integration. However, as shown in fig. 1, the vertical split layout of the detector ring makes adjacent sides of the two adjacent detection surfaces spaced by a slit G that cannot receive radiation, the slit G being formed by the rims of the two adjacent detector units and a gap due to assembly errors or the like, a fixed and vertically penetrating linear sampling deletion is formed in the projection space. These fixed missing bands appear as periodic fringes as the device is rotated and scanned, which in turn are back-projection magnified in the reconstructed image, forming an annular artifact centered on the axis. Such artifacts severely reduce the quantitative accuracy of the image and destroy the image structure, and may mask microscopic lesions or structural defects in high-accuracy medical diagnosis and industrial nondestructive testing. Disclosure of Invention It is an object of the present invention to provide a detector ring for a computed tomography apparatus which enables the computed tomography apparatus to effectively eliminate ring artifacts. It is a further object of the present invention to provide a computed tomography apparatus comprising a detector ring as described above, which is capable of effectively eliminating ring artifacts. It is a further object of the present invention to provide a method for determining sampling parameters of a computed tomography apparatus, which is capable of simply and conveniently determining the sampling parameters of the computed tomography apparatus, and determining whether the computed tomography apparatus can effectively eliminate the ring artifact. The invention provides a detector ring of a computed tomography device, which is formed by arranging a plurality of detector units along the circumferential direction of the detector ring. The detection surface of each detector unit is parallel to the axis of the detector ring. Adjacent sides of adjacent two detection faces are arranged parallel to and opposite each other, which side