CT (Computed Tomography) system with front movement collimation linkage control and control method

Abstract

The invention discloses a front movement collimation linkage control CT system and a control method.The CT system comprises an X-ray source, a front collimation assembly, a detector assembly, a patient support and a control unit, and the detector assembly is provided with a non-rectangular effective sensitive area and a non-sensitive area surrounding the effective sensitive area; the front collimation assembly comprises a Z-direction main blade and an X-direction auxiliary blade, the main blade is used for setting the isocenter coverage width, and the auxiliary blade is used for conducting fine cutting in an opening of the main blade; the patient support has X-direction preset positioning and mechanical locking functions; the control unit is configured to control the auxiliary blade in the scanning process, so that the projection boundary of the auxiliary blade on the detector is always located on the inner side of the non-sensitive area, and a preset safety belt is kept in the effective sensitive area. Through linkage control of conformal shielding of the non-rectangular detector, the X-direction auxiliary blade and X-direction preset positioning of the patient support, the imaging quality is guaranteed, and meanwhile the radiation dosage of the patient and invalid irradiation of the detector are remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of CT system control technology, and particularly to the invention title. Background Technology

[0002] Currently, in the field of CT imaging technology, traditional CT systems generally use rectangular X-ray fields to irradiate near-circular or circular fields of view (FOV), resulting in a large amount of ineffective radiation in the corner areas of the detector. This not only increases the unnecessary radiation dose to the patient but also introduces additional scattering noise, reducing image quality. Although existing technologies have attempted to alleviate this problem through static corner occlusion or changes in detector shape, these solutions are difficult to adapt to different scan coverage widths and changes in patient position, and cannot effectively eliminate ineffective X-ray radiation while ensuring image quality. In particular, there is a lack of a systematic solution that can achieve coordinated operation of conformal occlusion in non-sensitive areas and fine cropping within the field of view. Summary of the Invention

[0003] In view of this, the present invention proposes a CT system and control method with forward collimation linkage control, which can significantly reduce patient radiation dose and reduce ineffective detector irradiation while ensuring image quality. The present invention provides the following technical solution: A CT system with front collimation linkage control includes an X-ray source, a front collimation assembly, a detector assembly, a patient support, and a control unit. The detector assembly has a non-rectangular effective sensitive area and a non-sensitive area surrounding the effective sensitive area; The forward collimation assembly includes a Z-axis main blade and an X-axis auxiliary blade, wherein the main blade is used to set the isocentric coverage width, and the auxiliary blade is used to perform fine trimming inside the opening of the main blade. The patient stent has X-axis preset positioning and mechanical locking functions; The control unit is configured to control the auxiliary blade during the scanning process, so that its projection boundary on the detector is always located inside the non-sensitive area and maintains a preset safety zone with the effective sensitive area.

[0004] Optionally, the non-rectangular effective sensitive area can be cross-shaped, circular, elliptical, rounded rectangle, or polygonal; The non-sensitive area is achieved through module removal, pixel removal, solid removal, or masking.

[0005] Optionally, the width of the seat belt is not less than 0.5 mm and not more than 1 mm; The full-time envelope of the projected boundary of the auxiliary blade is always located inside the non-sensitive region.

[0006] Optionally, the Z-direction main blade is configured to dynamically adjust its opening according to the target isocenter coverage width. The target isocenter coverage width can be a preset set of discrete values ​​or a continuously variable value. Furthermore, the Z-direction main blade can be completely closed during the X-ray tube preheating or testing phase to form a fully shielded safety state, preventing X-rays from irradiating the detector.

[0007] Optionally, the control unit adopts a feedforward and closed-loop control strategy to control the X-axis auxiliary blade to extend locally into the X-axis inside the opening of the main blade, so that its projection boundary on the detector dynamically matches the contour of the non-sensitive area, thereby realizing the linkage control of conformal shading of the non-sensitive area and fine trimming within the FOV. The X-axis auxiliary blade eliminates invalid X-axis illumination by conformally shading the non-sensitive area.

[0008] Optionally, the X-direction displacement range of the patient stent is ±50mm, and the positioning accuracy is no greater than 0.5mm; The X-ray preset positioning is performed only before exposure or between scan segments, and the patient stent is mechanically locked during X-ray exposure to ensure the stability of the patient's position during imaging.

[0009] The present invention further discloses a front collimation device for a CT system, comprising: The Z-axis arranged main blade group is used to set the isocentric coverage width; The auxiliary blades, arranged in the X direction, are located inside the opening of the main blades; The drive mechanism is used to control the position and orientation of the main blades and auxiliary blades; The control module is configured to control the auxiliary blades so that their projected boundary on the detector is always inside the non-sensitive area and to maintain the safety belt.

[0010] The present invention further discloses a detector assembly for a CT system having a non-rectangular effective sensitive area, the effective sensitive area being cross-shaped, having a first sensitive strip extending in the Z direction and a second sensitive strip extending in the X direction; The non-sensitive area is arranged around the effective sensitive area; the width of the first sensitive strip in the Z direction is greater than the width of the second sensitive strip in the Z direction; The non-sensitive zone is configured to receive the projection of the auxiliary collimating blades, achieving zero or near-zero illumination.

[0011] This invention further discloses a linkage control method for a CT system, comprising: Receive target center coverage width and patient eccentricity information; Calculate the Z-axis main blade opening based on the preset geometric relationship; Determine the pose of the X-axis auxiliary blade to ensure that its projection boundary on the detector is always located inside the non-sensitive area; The patient stent is pre-positioned in the X-axis, and the region of interest is aligned with the area in the effective sensitive area of ​​the detector that can meet the isocentric coverage width of the target. During the scanning process, the full-time envelope of the auxiliary blade projection boundary is kept inside the non-sensitive area.

[0012] Optionally, the Z-axis main blade opening is based on the formula Calculation, where The half-width of the symmetrical opening in the Z-direction on the collimation plane. The total opening width of the isocentric planes. It is the geometric magnification factor at the isocenter; The control process follows the principle of full-time envelope determination to ensure that the occlusion boundary at any time is inside the non-sensitive area and leaves a safety zone.

[0013] According to the technical solution of the present invention, the dynamic projection boundary of the auxiliary blade is precisely controlled throughout the scanning process through the pre-movement collimation linkage control mechanism, ensuring that it is always located inside the non-sensitive area of ​​the detector and maintains a safe distance, thereby achieving zero or near-zero irradiation in the non-sensitive area and significantly reducing the radiation dose received by the patient. At the same time, combined with the patient stent X-axis preset positioning function and the optimized design of the non-rectangular detector, the problem of ineffective corner irradiation caused by the rectangular X-ray field irradiating the circular field of view in the traditional CT system is effectively solved, and the inherent defect of insufficient effective field of view of the non-rectangular detector is overcome. The region of interest is accurately positioned in a wider sensitive area in the Z-axis, which not only ensures the imaging quality, but also reduces detector surface scattering through the on-demand coverage mechanism, extends the service life of the equipment, and achieves a synergistic improvement in dose optimization and imaging performance. Attached Figure Description

[0014] For illustrative and not limiting purposes, the present invention will now be described in conjunction with embodiments and accompanying drawings, wherein: Figure 1 This is a schematic diagram of the YZ plane structure and coordinate definition of the CT system in an embodiment of the present invention; Figure 2 This is a schematic diagram of the XY plane structure and coordinate definition of the CT system in an embodiment of the present invention; Figure 3 This is a schematic diagram of the effective sensitive area and non-sensitive area of ​​an exemplary cross-shaped detector in an embodiment of the present invention. Figure 4 This is a schematic diagram showing the positional relationship between the front collimating main blade and the auxiliary blade in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the conformal matching degree between the auxiliary collimation blades and the non-sensitive area of ​​the detector in an embodiment of the present invention; Figure 6 This is a schematic diagram of the patient stent's X-axis pre-positioning movement in an embodiment of the present invention; Figure 7 This is a schematic diagram of the linkage control process in an embodiment of the present invention. Detailed Implementation

[0015] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0016] It should be noted that, where there is no conflict, the embodiments and features of the embodiments in this application can be combined with each other. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0017] refer to Figure 1 This embodiment discloses a CT system with forward collimation linkage control, including an X-ray source 101, a forward collimation component 102, a detector component 103, a patient support 104, and a control unit. The system adopts a standard CT geometry, with the rotation center O as the origin of the coordinate system, defining the X-axis as the transverse direction, the Y-axis as the direction of the line connecting the X-ray source and the detector, and the Z-axis as the longitudinal direction (patient bed feed direction).

[0018] like Figure 1 As shown, in the YZ plane, the distance between the X-ray source 101 and the isocenter plane is... y iso The pre-collimation assembly 102 is located between the X-ray source 101 and the detector assembly 103, at a distance from the X-ray source 101 of [missing information]. y c The distance between detector assembly 103 and X-ray source 101 is y d When the system is in operation, the X-ray source 101 and the detector assembly 103 acquire projection data by sending and receiving data.

[0019] like Figure 1 , Figure 2 and Figure 4 As shown, in the XY plane, the front collimation assembly 102 includes a Z-direction main blade 401 and an X-direction auxiliary blade 402, which together constitute a variable-shape X-ray beam confinement device. The front collimation assembly 102 can be one or more sets to meet the target isocentric coverage width requirements for continuous or segmented targets. W use The patient stent 104 has X-axis translation capability and can be precisely positioned within a range of ±50mm, with a positioning accuracy of no more than 0.5mm.

[0020] refer to Figure 3 The detector assembly 103 has a non-rectangular effective sensitive area 301 and a non-sensitive area 302 surrounding the effective sensitive area. In this embodiment, the effective sensitive area 301 is designed in a cross shape, including a first sensitive strip 301a extending in the Z direction and a second sensitive strip 301b extending in the X direction, wherein the width of the first sensitive strip 301a in the Z direction is greater than the width of the second sensitive strip 301b in the Z direction, to fully consider the characteristics of human anatomy and enable the Z-direction sensitive strip to cover more longitudinal structures. The non-sensitive area 302 is implemented by a module removal method, that is, removing the edge modules of the detector during the manufacturing process to form a clear boundary of the non-sensitive area. In other embodiments, the non-sensitive area 302 can also be implemented by pixel removal (disabling the readout circuit of a specific area), physical removal (physically removing the edge of the detector), or masking (adding X-ray-impermeable material for coverage), or a combination of these methods. The function of the non-sensitive area 302 is to receive the projection of the auxiliary collimator blades to achieve zero or near-zero radiation, thereby reducing unnecessary radiation dose.

[0021] Reference Figure 4 The front collimation assembly 102 includes a Z-axis main blade 401 and an X-axis auxiliary blade 402. The Z-axis main blade 401 is used to set the isocenter coverage width, supporting multiple discrete or continuously variable values ​​such as 16cm, 8cm, 4cm, and 2cm. During the X-ray tube preheating or testing phase, the Z-axis main blade 401 is completely closed to form a full-shield safety state, preventing X-rays from irradiating the detector, protecting the detector components, and extending their service life. The X-axis auxiliary blade 402 is located inside the opening of the main blade and does not participate in the longitudinal coverage setting; it is only used for fine trimming inside the opening of the main blade. The control unit controls the X-axis auxiliary blade 402 to extend partially along the X-axis inside the opening of the main blade, so that its projection boundary on the detector dynamically matches the contour of the non-sensitive area. Figure 5 As shown, the distance parameter between the projection boundary and the boundary of the non-sensitive area 302 is Δrx. The control unit ensures that the distance is not less than 0.5mm and not greater than 1mm, forming a safety belt 501, ensuring that the full-time domain envelope of the auxiliary blade projection boundary is always located inside the non-sensitive area 302, realizing the linkage control of conformal occlusion in the non-sensitive area and fine trimming within the FOV.

[0022] Reference Figure 6The patient stent 104 features X-axis preset positioning and mechanical locking. Before scanning, the control unit receives patient eccentricity information and controls the drive mechanism to preset the patient stent in the X-axis, with a displacement range of ±50mm and a positioning accuracy of no more than 0.5mm. For example, when a larger Z-axis coverage width is required, the control unit moves the patient stent to the X-axis position, placing the region of interest 602 within the first sensitive strip 301a, thereby fully utilizing the wider sensitive area in the Z-axis. X-axis preset positioning is performed only before exposure or between scan segments, and the patient stent remains mechanically locked during X-ray exposure to ensure the stability of the patient's position during imaging.

[0023] refer to Figure 5 The core of this implementation lies in achieving geometric conformity between the auxiliary blades and the non-sensitive area of ​​the detector, ensuring precise system operation through rigorous mathematical models and engineering specifications. Assume the front collimation plane is located at... At that location, the detector plane is located At that point, the center plane is located At this point, the projection magnification factor is At any point on the collimation plane Coordinates projected onto the detector plane Satisfy geometric relations: Furthermore, in actual control, the following is introduced: and ,in The safe distance between the auxiliary blade projection boundary and the non-sensitive area boundary in the X direction is set to 0.5-1mm in this embodiment; Characterizes the degree of overscan control in the Z-axis, and is dynamically adjusted according to clinical needs. For example... Figure 5 As shown. The control unit ensures that the auxiliary blades maintain a certain distance from the boundary of the non-sensitive area by calculating the projected boundary of the auxiliary blades on the detector. A safe distance is maintained, forming a safety zone 501. Crucially, this implementation employs a full-time-domain envelope determination principle to ensure geometric conformity. The full-time-domain envelope of the projected boundary is the union of the auxiliary blade projected boundaries throughout the entire scanning process, used to constrain the occlusion boundary at any given time. Conformity requirements: Throughout the entire scanning process, the full-time-domain envelope of the projected boundary always falls inside the non-sensitive area and maintains a safety zone of no more than 1 mm from the effective sensitive area. For example... Figure 5 As shown, the control unit ensures, through pre-calculation and real-time monitoring, that the projected position of the auxiliary blades never exceeds this envelope range at any point during the entire scanning process, thus fundamentally avoiding the risk of the effective sensitive area being accidentally obscured. Furthermore, the calculation of the Z-axis main blade opening is based on the following geometric relationship: Let... For the target isocenter coverage width, Let be the total opening width of the isocentric planes, then ,in, s The half-width of the symmetrical opening in the Z-direction on the collimation plane. This represents the isocentric geometric magnification factor. To achieve the aforementioned geometric conformity, the control unit employs a combined feedforward and closed-loop control strategy. Feedforward control is based on pre-calculated theoretical pose trajectories, while closed-loop control uses a high-precision encoder mounted on the auxiliary blades to provide real-time position information, or performs visual inspection, to dynamically correct the projected boundaries. During the system calibration phase, X-ray projections are generated using a dedicated test phantom for direct measurement and verification. and Indicators are used to ensure that system performance meets design requirements.

[0024] Therefore, this implementation method achieves significant clinical benefits through the coordinated design of a non-rectangular detector and anterior collimation: the layout of the cross-shaped effective sensitive area and the surrounding non-sensitive area, combined with the precise trimming of the X-axis auxiliary blade inside the opening of the main blade, ensures that the projection boundary of the auxiliary blade is always accurately located inside the non-sensitive area and maintains a 0.5-1mm safety zone, achieving zero or near-zero irradiation in the non-sensitive area and significantly reducing the patient's radiation dose; the multi-level coverage width adjustment of the Z-axis main blade and the full shielding function during the X-ray tube preheating stage not only meet different scanning needs but also effectively protect the detector; at the same time, the X-axis preset positioning function within ±50mm of the patient support precisely moves the region of interest into the wider sensitive strip in the Z-axis, solving the problem of insufficient effective field of view of the non-rectangular detector. The three working together reduce ineffective irradiation and scattering noise, improve image quality, and extend the service life of the equipment, achieving a dual improvement in radiation safety and imaging performance.

[0025] refer to Figure 7 This embodiment further discloses a linkage control method applicable to the above-mentioned CT system, the method comprising: Initialization: The system starts up, enters the "Start / Prepare for Scan" state, and loads default parameters; Parameter reception: Target center coverage width W use and geometric parameters ; Mode determination: Determine if the current mode is "warm-up / test mode": If it is warm-up / test mode, then set... W use =0, so that the main blade and auxiliary blade are completely closed to form a fully occluded safety state, and the process ends after "exposure and acquisition" is performed; if it is a normal scanning mode, then the subsequent steps are performed. Main blade opening calculation: The Z-axis main blade opening is calculated based on geometric relationships. The formula is as follows: ,in, s The half-width of the symmetrical opening in the Z-direction on the collimation plane. The total opening width of the isocentric planes. It is the geometric magnification factor of the isocenter; according to the formula Perform trajectory calculation on the main blade; Auxiliary blade pose determination: Calculate the pose of the auxiliary blade in the X direction to ensure that its projection boundary on the detector is always located inside the non-sensitive area, and the safety belt width is kept between 0.5mm and 1mm. Position setting and distribution: The calculated position parameters of the main blades and auxiliary blades are distributed to the drive mechanism; Sensor feedback and geometric correction: Obtain the actual position information of the blade through encoders or optical markers; Geometric verification judgment: Check whether the geometric verification standard Δr is met. x ≤1mm and Δr z ≤1mm: If the target is not met, perform geometric fine-tuning and closed-loop compensation, and return to step 6 to reissue the position setting; if the target is met, continue to the next step. Patient stent positioning: Control the patient stent to perform preset positioning in the X-axis, aligning the region of interest with the area in the detector's effective sensitive area that can meet the target's isocentric coverage width; Exposure and Acquisition: Perform X-ray exposure and acquire projection data; Process complete: Scan finished, system enters standby mode.

[0026] Therefore, this linkage control method first provides a full shielding safety state during the preheating / testing phase to prevent X-ray leakage; secondly, it employs a closed-loop control strategy during normal scanning to ensure that the geometric parameters always satisfy Δr. x ≤1mm and Δr z A stringent requirement of ≤1mm is maintained. When geometric verification fails to meet the standard, the system automatically performs fine-tuning and compensation until the accuracy requirement is met, thus ensuring the reliability of conformal shading in non-sensitive areas. X-ray movement of the patient stent is only performed after geometric verification is achieved and remains locked during X-ray exposure, ensuring the stability of the patient's position during imaging. This design effectively solves the problem of ineffective irradiation in traditional CT systems, achieving a significant reduction in radiation dose and an improvement in image quality.

[0027] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0028] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of each embodiment or some parts of the embodiments.

[0029] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A CT system with front collimation linkage control, comprising an X-ray source, a front collimation assembly, a detector assembly, a patient support, and a control unit, characterized in that: The detector assembly has a non-rectangular effective sensitive area and a non-sensitive area surrounding the effective sensitive area; The forward collimation assembly includes a Z-axis main blade and an X-axis auxiliary blade, wherein the main blade is used to set the isocentric coverage width, and the auxiliary blade is used to perform fine trimming inside the opening of the main blade. The patient stent has X-axis preset positioning and mechanical locking functions; The control unit is configured to control the auxiliary blade during the scanning process, so that its projection boundary on the detector is always located inside the non-sensitive area and maintains a preset safety zone with the effective sensitive area.

2. The CT system according to claim 1, characterized in that, The non-rectangular effective sensitive area can be cross-shaped, circular, elliptical, rounded rectangle, or polygonal; The non-sensitive area is achieved through module removal, pixel removal, solid removal, or masking.

3. The CT system according to claim 1, characterized in that, The width of the seat belt shall be no less than 0.5 mm and no more than 1 mm; The full-time envelope of the projected boundary of the auxiliary blade is always located inside the non-sensitive region.

4. The CT system according to claim 1, characterized in that, The Z-axis main blade is configured to dynamically adjust its opening based on the target isocenter coverage width. The target isocenter coverage width can be a preset set of discrete values ​​or a continuously variable value. Furthermore, the Z-axis main blade can be completely closed during the X-ray tube preheating or testing phase to form a fully shielded safety state, preventing X-rays from irradiating the detector.

5. The CT system according to any one of claims 1-4, characterized in that, The control unit adopts a feedforward and closed-loop control strategy to control the X-axis auxiliary blade to extend locally into the X-axis inside the opening of the main blade, so that its projection boundary on the detector dynamically matches the contour of the non-sensitive area, realizing the linkage control of conformal shading of the non-sensitive area and fine trimming within the FOV. The X-axis auxiliary blade eliminates invalid X-axis illumination by conformally shading the non-sensitive area.

6. The CT system according to claim 1, characterized in that, The X-axis displacement range of the patient stent is ±50mm, and the positioning accuracy is no greater than 0.5mm; The X-ray preset positioning is performed only before exposure or between scan segments, and the patient stent is mechanically locked during X-ray exposure to ensure the stability of the patient's position during imaging.

7. A front collimation device for a CT system, characterized in that, include: The Z-axis arranged main blade group is used to set the isocentric coverage width; The auxiliary blades, arranged in the X direction, are located inside the opening of the main blades; The drive mechanism is used to control the position and orientation of the main blades and auxiliary blades; The control module is configured to control the auxiliary blades so that their projected boundary on the detector is always inside the non-sensitive area and to maintain the safety belt.

8. A detector assembly for a CT system, characterized in that: It has a non-rectangular effective sensitive area, which is cross-shaped and has a first sensitive strip extending in the Z direction and a second sensitive strip extending in the X direction; Non-sensitive areas are arranged around the effective sensitive areas; The width of the first sensitive strip in the Z direction is greater than the width of the second sensitive strip in the Z direction; The non-sensitive zone is configured to receive the projection of the auxiliary collimating blades, achieving zero or near-zero illumination.

9. A linkage control method for a CT system, characterized in that, include: Receive target center coverage width and patient eccentricity information; Calculate the Z-axis main blade opening based on the preset geometric relationship; Determine the pose of the X-axis auxiliary blade to ensure that its projection boundary on the detector is always located inside the non-sensitive area; The patient stent is pre-positioned in the X-axis, and the region of interest is aligned with the area in the effective sensitive area of ​​the detector that can meet the isocentric coverage width of the target. During the scanning process, the full-time envelope of the auxiliary blade projection boundary is kept inside the non-sensitive area.

10. The linkage control method according to claim 8, characterized in that, The Z-axis main blade opening is based on the formula Calculation, where The half-width of the symmetrical opening in the Z-direction on the collimation plane. The total opening width of the isocentric planes. It is the geometric magnification factor at the isocenter; The control process follows the principle of full-time envelope determination to ensure that the occlusion boundary at any time is inside the non-sensitive area and leaves a safety zone.

Images