CBCT device based on general image sensor

Abstract

The invention discloses a CBCT (cone beam computed tomography) device based on a general image sensor. The CBCT device comprises a main control computer, a bracket, a rotary suspension arm, a cone beam X-ray source and an imaging part, the imaging part is composed of a scintillator, a plane mirror and a zoom camera. The cone-beam X-ray penetrates through a measured object and irradiates the scintillator, and the scintillator converts an energy signal carried by the X-ray into a visible light signal. And after the visible light signal is reflected by the plane mirror, a light path deflects by 90 degrees, and is imaged on an image sensor of the zoom camera through the lens. The provided CBCT device uses a general image sensor which is higher in resolution, lower in noise level and lower in cost compared with an existing flat panel detector. In addition, the circuit part of the imaging part is prevented from being irradiated by X-rays, so that the service life is greatly prolonged. Besides, the view field range of the camera on the scintillator can be changed by changing the focal length, meanwhile, the spatial resolution capability of the CBCT device is changed, and the configuration flexibility of the CBCT device can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of X-ray imaging, and more specifically, to a CBCT device based on a universal image sensor. Background Technology

[0002] Currently, commercially available large-area X-ray flat panel detectors suffer from problems such as large pixel size, low spatial resolution, and high cost. For example, large-area X-ray flat panel detectors commonly used in CBCT (Cone Beam Computed Tomography) typically have pixel sizes greater than 100 micrometers, far exceeding the pixel sizes of general-purpose image sensors, which are typically 2-5 micrometers. Pixel size is a key factor affecting imaging spatial resolution. Besides pixel size, the photoelectric conversion efficiency and signal-to-noise ratio (SNR) of the flat panel detector and image sensor are also crucial factors affecting image quality. In recent years, with the rapid development of general-purpose image sensor technology and the rapid improvement of manufacturing processes, their performance in electronic circuits, such as photoelectric conversion efficiency and SNR, has become increasingly stronger, with some performance characteristics far exceeding those of flat panel detectors. Although the area of ​​a single pixel in a general-purpose image sensor is much smaller than that of a flat panel detector, the advantages of the former in photoelectric conversion efficiency and SNR are sufficient to compensate for the disadvantage of a smaller photosensitive area per pixel, thereby improving the overall X-ray imaging quality. Furthermore, general-purpose image sensors have a cost advantage over large-area X-ray flat panel detectors. Summary of the Invention

[0003] This invention proposes a CBCT device based on a universal image sensor, replacing the existing large-area X-ray flat panel detector with a universal image sensor. This invention is achieved through the following technical solution:

[0004] This invention discloses a CBCT device based on a universal image sensor, comprising:

[0005] Support bracket: Used to mount the rotary motor and support the imaging unit and cone-beam X-ray source;

[0006] Rotary motor: used to drive the boom to rotate;

[0007] The boom is used to mount the cone-beam X-ray source and imaging unit.

[0008] Cone-beam X-ray source: Used to emit cone-beam X-rays;

[0009] Imaging unit: Used to receive cone-beam X-rays and create images;

[0010] Scintillator: Used to convert the energy signal carried by X-rays into a visible light signal;

[0011] Plane mirror: used to reflect the visible light signal emitted by the scintillator to the zoom camera;

[0012] Zoom camera: Used to receive and record visible light signals from a scintillator reflected by a plane mirror, equipped with a general-purpose image sensor;

[0013] Main control computer; used to control the rotating motor, cone-beam X-ray source, and zoom camera;

[0014] The rotary motor is connected to the boom, and the imaging unit and the cone-beam X-ray source are fixedly mounted on the boom. The main control computer is connected to the rotary motor, the cone-beam X-ray source and the camera via cables. The imaging unit includes a rectangular hollow cavity structure, a scintillator on the side wall of the rectangular hollow cavity structure corresponding to the position of the cone-beam X-ray source, a plane mirror located inside the rectangular hollow cavity structure and behind the scintillator, and a zoom camera located above the plane mirror and inside the rectangular hollow cavity structure. The central axis of the cone-beam X-ray emitted by the cone-beam X-ray source is perpendicularly incident on the center of the scintillator, and the irradiation range of the cone-beam X-ray covers the entire scintillator.

[0015] As a further improvement, the zoom camera described in this invention is located outside the range of cone-beam X-ray irradiation.

[0016] As a further improvement, the optical axis of the zoom camera described in this invention is perpendicular to the central axis of the cone-beam X-ray and intersects at the center of the plane mirror.

[0017] As a further improvement, the optical axis of the zoom camera described in this invention is at a 45° angle of incidence to the plane mirror, and the central axis of the cone-beam X-ray is at a 45° angle of incidence to the plane mirror.

[0018] As a further improvement, the zoom camera of the present invention focuses on the virtual image plane after the scintillator plane is reflected by the plane mirror.

[0019] As a further improvement, the zoom camera of the present invention changes its field of view on the scintillator by changing its focal length, thereby changing its spatial resolution on the scintillator.

[0020] As a further improvement, the present invention calibrates the zoom camera once for each preset focal length to determine the scintillator size corresponding to a single pixel and to eliminate imaging distortion of the zoom camera lens.

[0021] As a further improvement, the scintillator described in this invention can be easily disassembled and installed from the outside of the device.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. By replacing the dedicated large-area X-ray flat panel detector in the existing CBCT device with a zoom camera equipped with a general-purpose image sensor, the general-purpose image sensor can receive and record the visible light signal of the scintillator. The advantages of the general-purpose image sensor in terms of photoelectric conversion efficiency and signal-to-noise ratio are enough to make up for its disadvantage of having a smaller photosensitive area per pixel than the large-area X-ray flat panel detector, thereby improving the overall X-ray imaging quality.

[0024] 2. A zoom camera equipped with a universal image sensor replaces the dedicated large-area X-ray flat panel detector in existing CBCT devices to receive and record visible light signals from the scintillator. The universal image sensor and the cone-beam X-ray source are connected by the following optical path design: the optical axis of the zoom camera equipped with the universal image sensor is perpendicular to the central axis of the cone-beam X-ray and intersects at the center of the plane mirror. The optical axis of the zoom camera is at a 45° angle of incidence to the plane mirror, and the central axis of the cone-beam X-ray is at a 45° angle of incidence to the plane mirror. The zoom camera is focused on the virtual image plane of the scintillator plane after reflection by the plane mirror, so that the zoom camera is outside the irradiation range of the cone-beam X-ray, avoiding the problem of shortened service life caused by the universal image sensor and other electronic components inside the zoom camera being exposed to X-ray irradiation.

[0025] 3. Since general-purpose image sensors and zoom lenses have cost advantages in mass production, replacing the dedicated large-area X-ray flat panel detector in existing CBCT devices with a zoom camera equipped with a general-purpose image sensor can significantly reduce the hardware cost of CBCT devices.

[0026] 4. Unlike existing CBCT devices where the large-area X-ray flat panel detector must be integrated with the scintillator to form an integrated device, in this invention, the general-purpose image sensor and the scintillator are installed separately. The scintillator can be easily removed and installed from the outside of the device. When the performance of the scintillator degrades, the scintillator can be replaced separately, making use and maintenance more convenient.

[0027] 5. By presetting the focal lengths of multiple zoom cameras, the zoom camera is calibrated once for each preset focal length. This is used to determine the scintillator size corresponding to a single pixel of the general image sensor and to eliminate the imaging distortion parameters of the zoom camera lens. This can provide a variety of corresponding CBCT devices with field of view and spatial resolution capabilities, enabling a single CBCT device to have a variety of different combinations of detection range and spatial resolution to meet a variety of different application requirements. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the principle of the CBCT device based on a general image sensor according to the present invention;

[0029] Figure 2This is a three-dimensional appearance schematic diagram of the CBCT device based on a universal image sensor according to the present invention.

[0030] In the diagram, 1 is the support frame, 2 is the rotary motor, 3 is the boom, 4 is the cone-beam X-ray source, 5 is the imaging unit, 6 is the object under test, 7 is the scintillator, 8 is the plane mirror, 9 is the zoom camera, and 10 is the main control computer. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. For the sake of brevity, some content known in the art has been omitted when describing the processes, conditions, experimental methods, etc. of the embodiments of the present invention, and the present invention does not have any particular limitations on such content.

[0032] The following will combine Figure 1 The CBCT device based on a universal image sensor of the present invention will be described in further detail.

[0033] The CBCT device based on a general-purpose image sensor mentioned in this invention mainly includes:

[0034] Support 1: Used to mount the rotary motor 2 and support the imaging unit 5 and the cone-beam X-ray source 4;

[0035] Rotary motor 2: used to drive the boom 3 to rotate;

[0036] boom 3: used to install cone-beam X-ray source 4 and imaging unit 5;

[0037] Cone-beam X-ray source 4: Used to emit cone-beam X-rays;

[0038] Imaging unit 5: Used to receive cone-beam X-rays and perform imaging;

[0039] Scintillator 7: Used to convert the energy signal carried by X-rays into a visible light signal;

[0040] Plane mirror 8: used to reflect the visible light signal emitted by scintillator 7 to zoom camera 9;

[0041] Zoom camera 9: Used to receive and record visible light signals reflected by scintillator 7 from plane mirror 8, and equipped with a general image sensor;

[0042] Main control computer 10; used to control rotary motor 2, cone-beam X-ray source 4 and camera;

[0043] like Figure 1As shown, the rotary motor 2 is connected to the boom 3. The imaging unit 5 and the cone-beam X-ray source 4 are fixedly mounted on the boom 3. The main control computer 10 is connected to the rotary motor 2, the cone-beam X-ray source 4, and the camera via cables. The imaging unit 5 includes a rectangular hollow cavity structure, a scintillator 7 on the side wall of the rectangular hollow cavity structure corresponding to the position of the cone-beam X-ray source 4, a plane mirror 8 located inside the rectangular hollow cavity structure and behind the scintillator 7, and a zoom camera 9 located above the plane mirror 8 and inside the rectangular hollow cavity structure. The central axis of the cone-shaped X-ray emitted by the X-ray source 4 is perpendicularly incident on the center of the scintillator 7. The irradiation range of the cone-shaped X-ray covers the entire scintillator 7. The zoom camera 9 is located outside the irradiation range of the cone-shaped X-ray. The optical axis of the zoom camera 9 is perpendicular to the central axis of the cone-shaped X-ray and intersects the center of the plane mirror 8. The optical axis of the zoom camera 9 is at a 45° angle of incidence to the plane mirror 8. The central axis of the cone-shaped X-ray is at a 45° angle of incidence to the plane mirror 8. The zoom camera 9 is focused on the virtual image plane of the scintillator 7 after reflection by the plane mirror 8. A cone-beam X-ray passes through the object under test 6 and strikes the scintillator 7. The energy carried by the X-ray photons is converted by the scintillator 7 into visible light containing information about the object under test 6. This light is then imaged through a plane mirror 8 and a zoom lens onto the imaging surface of an image sensor, capturing and recording an image containing information about the object under test 6. A rotating motor 2 drives a boom 3, which in turn drives the imaging unit 5 and the cone-beam X-ray source 4 to rotate around the object under test 6. During this rotation, multiple images containing information about the object under test 6 are captured and recorded, while the rotation position of the motor is also recorded. Finally, the CT image of the object under test 6 is obtained through image processing.

[0044] The zoom camera 9 changes its field of view on the scintillator 7 by altering its focal length, thereby changing its spatial resolution on the scintillator 7. For each preset focal length, the zoom camera 9 is calibrated to determine the size of the scintillator 7 corresponding to a single pixel and to eliminate imaging distortion in the zoom camera 9 lens. The scintillator 7 can be easily attached and detached from the device.

[0045] The specific steps for calibrating a zoom camera 9 are as follows:

[0046] S1 adjusts the focal length of the zoom camera 9 so that the field of view just covers the scintillator 7, and then focuses on the plane of the scintillator 7.

[0047] S2 removes the scintillator 7, holds the checkerboard calibration board near the original plane of the scintillator 7, and takes a set of about 20 images of the calibration board in different poses using the zoom camera 9;

[0048] S3 uses a set of calibration board images obtained in step S2 to calibrate the intrinsic parameters and distortion coefficients of the zoom camera 9 in the current state using Zhang Zhengyou's checkerboard calibration method;

[0049] S4 adjusts the focal length of the zoom camera 9 to a smaller field of view than in step S1, and then focuses on the plane of the scintillator 7.

[0050] The S5 handheld checkerboard calibration board was placed near the original scintillator 7 plane, and a set of about 20 images of the calibration board in different poses were taken by the zoom camera 9.

[0051] S6 uses a set of calibration board images obtained in step S5 to calibrate the intrinsic parameters and distortion coefficients of the zoom camera 9 in the current state using Zhang Zhengyou's checkerboard calibration method.

[0052] S7 Repeat steps S4 to S6 to obtain the zoom camera 9 intrinsic parameters and distortion coefficients corresponding to several different focal length positions;

[0053] S8 stores the intrinsic parameters and distortion coefficients of the zoom camera 9 corresponding to multiple different focal length positions obtained in steps S3 and S7 in the main control computer 10 for subsequent image distortion correction and CBCT data 3D reconstruction and other processing.

[0054] The CBCT device based on a general-purpose image sensor mentioned in this invention is not limited to the embodiments described above. Various modifications and improvements can be made without departing from the principle of this invention.

[0055] The scope of protection of this invention is not limited to the embodiments described above. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A CBCT device based on a general-purpose image sensor, characterized in that, include: Support bracket: Used to mount the rotary motor and support the imaging unit and cone-beam X-ray source; Rotary motor: used to drive the boom to rotate; The boom is used to mount the cone-beam X-ray source and imaging unit. Cone-beam X-ray source: Used to emit cone-beam X-rays; Imaging unit: Used to receive cone-beam X-rays and create images; Scintillator: Used to convert the energy signal carried by X-rays into a visible light signal; Plane mirror: used to reflect the visible light signal emitted by the scintillator to the zoom camera; Zoom camera: Used to receive and record visible light signals from a scintillator reflected by a plane mirror, equipped with a general-purpose image sensor; Main control computer; used to control the rotating motor, cone-beam X-ray source, and zoom camera; The rotary motor is connected to the boom, and the imaging unit and the cone-beam X-ray source are fixedly mounted on the boom. The main control computer is connected to the rotary motor, the cone-beam X-ray source, and the camera via cables. The imaging unit includes a rectangular hollow cavity structure, a scintillator on the side wall of the rectangular hollow cavity structure corresponding to the position of the cone-beam X-ray source, a plane mirror located inside the rectangular hollow cavity structure and behind the scintillator, and a zoom camera located above the plane mirror and inside the rectangular hollow cavity structure. The central axis of the cone-beam X-ray emitted by the cone-beam X-ray source is perpendicularly incident on the center of the scintillator, and the irradiation range of the cone-beam X-ray covers the entire scintillator.

2. The CBCT device based on a general-purpose image sensor according to claim 1, characterized in that, The zoom camera is located outside the range of the cone-beam X-ray irradiation.

3. The CBCT device based on a universal image sensor according to claim 1 or 2, characterized in that, The optical axis of the zoom camera is perpendicular to the central axis of the cone-beam X-ray and intersects at the center of the plane mirror.

4. The CBCT device based on a universal image sensor according to claim 3, characterized in that, The optical axis of the zoom camera is at a 45° angle of incidence to the plane mirror, and the central axis of the cone-beam X-ray is at a 45° angle of incidence to the plane mirror.

5. The CBCT device based on a universal image sensor according to claim 4, characterized in that, The zoom camera focuses on the virtual image plane after the scintillator plane is reflected by the plane mirror.

6. The CBCT device based on a universal image sensor according to claim 1, 2, 4, or 5, characterized in that, The zoom camera changes its field of view on the scintillator by changing its focal length, thereby changing its spatial resolution on the scintillator.

7. The CBCT device based on a universal image sensor according to claim 6, characterized in that, For each preset focal length of the zoom camera, the zoom camera is calibrated once to determine the scintillator size corresponding to a single pixel and to eliminate imaging distortion of the zoom camera lens.

8. The CBCT device based on a universal image sensor according to claim 7, characterized in that, The scintillator can be easily removed and installed from the outside of the device.

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