Method for correcting angle of x-ray tube and medical device including the same

Abstract

The present invention provides a table buckie alignment method for an X-ray tube during X-ray imaging, comprising: a step of rotating the X-ray tube by a plurality of reference angles and obtaining a sensor angle, which is a sensor output value corresponding to the rotation angle of the X-ray tube from an angle sensor provided in the X-ray tube at each reference angle; a step of obtaining a vertical separation distance from the X-ray tube to the table buckie; a step of obtaining a horizontal separation distance between a reference position of the table buckie and an alignment position of the table buckie aligned with the optical axis of the X-ray tube at each of the plurality of reference angles; a step of deriving an actual angle using the horizontal separation distance and the vertical separation distance; and a step of generating a correction map that defines the correspondence relationship between the sensor angle and the actual angle.

Description

Technology Field

[0001] The present invention relates to a medical device for X-ray imaging, and more specifically, to a tube angle correction method and a medical device including the same, which can improve the alignment accuracy of the X-ray optical axis and the table bucky by accurately correcting the angle of the X-ray tube by generating a correction map that defines the correspondence relationship between a sensor angle acquired from an angle sensor provided in an X-ray tube and an actual angle derived from actual imaging geometry. Background Technology

[0002] To perform oblique projection in a medical X-ray imaging device, it is necessary to tilt the X-ray tube at a predetermined angle and align the position of the table bucky with the X-ray optical axis.

[0003] Generally, X-ray tubes are equipped with angle sensors, and a method is used to control the position of a table bucky based on the sensor angle output by this sensor. For example, Japanese Patent Publication No. JP 9-10196 discloses a technique for aligning the X-ray radiation axis with the center of the bucky by utilizing the travel distance between the bucky device and the X-ray tube.

[0004] However, in the conventional technology described above, the phenomenon in which the sensor angle does not coincide with the angle formed by the actual X-ray optical axis is not sufficiently considered due to complex factors, such as the offset of the angle sensor itself, machining tolerances and clearances of mechanical parts like the rotation axis, link mechanism, gears, and bearings of the tube support structure, alignment deviations during device installation, and hysteresis caused by differences in gravitational load and friction conditions depending on the direction of tube movement. If such errors occur, the X-ray optical axis deviates from the center of the table bucky, which can lead to problems such as image distortion, reduced resolution, and increased patient radiation exposure resulting from re-imaging.

[0005] In particular, conventionally, tube angles were corrected using simple correction tables based on sensor angles or linear interpolation methods; however, these methods had the problem of failing to provide sufficient alignment performance in environments requiring large angle changes and precise alignment, such as oblique shooting. The problem to be solved

[0006] The problem to be solved by the present invention is to provide a tube angle correction method and a medical device that improve the angle correction accuracy of an X-ray tube regardless of the sensor angle error by deriving an actual angle using the SID, which is the distance between the X-ray tube and the table bucky, and the travel distance of the table bucky, and generating a correction map by configuring the correspondence relationship between the sensor angle acquired at a plurality of reference angles and the actual angle as a correction node.

[0007] In addition, the problem to be solved by the present invention is to provide a tube angle correction method and a medical device that secure stable correction performance over a wide angle range even with limited correction data by enabling the actual angle corresponding to any sensor angle to be derived by shape-preserving interpolation within the defined area of ​​the correction map and by linear extrapolation outside the defined area.

[0008] In particular, the problem to be solved by the present invention is to provide a tube angle correction method and a medical device capable of calculating the travel distance of a table buckie from the current SID and a correction angle corresponding to an arbitrary sensor angle based on a correction map, and continuously updating the correction map by reflecting the travel distance readjusted by the user as a new correction node.

[0009] The problems to be solved through the various embodiments of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0010] To solve the above problem, the technical concept of the present invention provides a method for correcting the angle of an X-ray tube during imaging of an X-ray imaging device, comprising: a step of rotating the X-ray tube by a plurality of reference angles and obtaining a sensor angle, which is a sensor output value corresponding to the rotation angle of the X-ray tube from an angle sensor provided in the X-ray tube at each reference angle; a step of obtaining a SID, which is the distance between the X-ray tube and a table buckie; a step of obtaining a displacement distance, which is the distance between a reference position of the table buckie and an alignment position of the table buckie aligned with the optical axis of the X-ray tube at each of the plurality of reference angles; a step of deriving an actual angle using the SID and the displacement distance; and a step of generating a correction map that defines the correspondence relationship between the sensor angle and the actual angle.

[0011] In one embodiment of the present invention, the step of generating the correction map may include: configuring the sensor angle and the actual angle into a pair of correction nodes for each of the plurality of reference angles; and deriving a correction angle corresponding to any sensor angle input based on the plurality of correction nodes.

[0012] In one embodiment of the present invention, the step of configuring the correction nodes is configured by converting the sensor angle and the actual angle into tangent functions, and the definition range of the plurality of correction nodes is from the correction node having the minimum sensor angle among the plurality of correction nodes to the correction node having the maximum sensor angle, and within the definition range, the plurality of correction nodes are connected by third-order interpolation for shape preservation sections to derive a correction angle corresponding to any sensor angle, and outside the definition range, a correction angle corresponding to any sensor angle can be derived by linear extrapolation using the endpoint slope.

[0013] In one embodiment of the present invention, the plurality of reference angles are set for each of the positive rotation direction and the negative rotation direction of the X-ray tube, and the correction map can be generated separately for each rotation direction.

[0014] In one embodiment of the present invention, the step of generating the correction map may generate the correction map by considering the rotational approach direction of the X-ray tube reaching an arbitrary sensor angle and deriving a correction angle for each rotational approach direction for the arbitrary sensor angle.

[0015] In one embodiment of the present invention, the method may further include the step of obtaining a correction angle corresponding to any sensor angle based on the correction map; and the step of calculating the travel distance of the table bucket through the correction angle and the SID.

[0016] In one embodiment of the present invention, the method may further include the steps of: obtaining a recalculated movement distance after the table bucky has moved according to the calculated movement distance, and then recalculating the position of the table bucky by the user; and creating a new correction node based on the recalculated movement distance and updating the correction map.

[0017] To solve the above problem, the technical concept of the present invention provides a medical device for X-ray imaging comprising: a tube unit including an X-ray tube that irradiates X-rays, an angle sensor that outputs a sensor angle corresponding to the rotation angle of the X-ray tube, and a lift that adjusts the height of the X-ray tube; a table unit including a top board, a table buckie movably disposed below the top board, and a position detection unit that detects the position of the table buckie; and a control unit that receives data from the angle sensor and the position detection unit and generates a correction map; wherein the control unit derives an actual angle corresponding to the sensor angle at each reference angle based on an SID, which is the distance between the X-ray tube and the table buckie obtained while the X-ray tube is rotated to a plurality of reference angles, and a displacement distance between the reference position of the table buckie and the alignment position of the table buckie aligned with the optical axis of the X-ray tube, and generates the correction map that defines the correspondence relationship between the sensor angle and the actual angle.

[0018] Specific details of other embodiments are included in the detailed description and drawings. Effects of the invention

[0019] According to embodiments of the present invention, the actual angle is derived from the SID, which is the distance between the X-ray tube and the table bucky, and the travel distance of the table bucky, without relying solely on the sensor angle. This allows for the generation of a correction map that reflects complex error factors such as sensor offset, machining tolerance, and installation deviation, thereby improving the angle correction accuracy of the X-ray tube.

[0020] According to another embodiment of the present invention, by applying shape-preserving interpolation within the defined area of ​​the correction map and linear extrapolation outside the defined area, stable correction performance can be secured over a wide angle range with only a limited number of correction points.

[0021] According to another embodiment of the present invention, the position of the table buckie at any sensor angle can be automatically controlled based on a correction map, and when the position of the table buckie is readjusted by the user, the correction map can be updated by creating a new correction node with the readjustment distance, so that the correction accuracy can be improved with repeated use.

[0022] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0023] FIG. 1 is a schematic perspective view of a medical device according to one embodiment of the present invention. FIG. 2 is a front conceptual diagram schematically showing the configuration of a medical device according to one embodiment of the present invention. FIG. 3 is a flowchart schematically illustrating a calibration procedure according to one embodiment of the present invention. FIG. 4 is a conceptual diagram schematically illustrating the process of deriving the actual angle when tilting an X-ray tube to the right according to one embodiment of the present invention. FIG. 5 is a conceptual diagram schematically illustrating the process of deriving the actual angle when an X-ray tube is tilted to the left according to one embodiment of the present invention. FIG. 6 is a conceptual diagram schematically showing a correction map according to one embodiment of the present invention. FIG. 7 is a conceptual diagram schematically showing a correction map reflecting hysteresis according to one embodiment of the present invention. FIG. 8 is a flowchart schematically illustrating a practical bucky control procedure according to one embodiment of the present invention. FIG. 9 is a flowchart schematically illustrating a feedback-based correction map update procedure according to one embodiment of the present invention. Specific details for implementing the invention

[0024] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0025] The embodiments described herein will be explained with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of the films and regions are exaggerated for effective explanation of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention.

[0026] In the various embodiments of this specification, terms such as first, second, third, etc., have been used to describe various components, but these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0027] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0028] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. Hereinafter, the concept of the present invention and embodiments thereof will be described in detail with reference to the drawings.

[0029] In this specification, "sensor angle (SA)" refers to a sensor output value output by an angle sensor (120) provided in an X-ray tube (110), and may mean a value corresponding to the rotation angle of the X-ray tube (110). The sensor angle (SA) may not completely coincide with the actual optical axis direction of the X-ray tube (110) due to complex factors such as the offset of the angle sensor (120), the machining tolerance of the tube support structure, and alignment deviations during device installation.

[0030] In this specification, "actual angle (RA)" may refer to an angle geometrically derived from the SID (VL100), which is the distance between the X-ray tube (110) and the table bucky (220), and the travel distance (HL200) of the table bucky (220). Unlike the sensor angle (SA), the actual angle (RA) is calculated based on actual imaging geometry and therefore may not be affected by sensor deviation.

[0031] In this specification, "correction map (AM)" may refer to a mapping relationship that defines the correspondence between a sensor angle (SA) acquired at a plurality of reference angles and an actual angle (RA). When an arbitrary sensor angle (SA) is input into the correction map (AM), a corresponding correction angle can be derived.

[0032] In this specification, "SID (VL100)" is an abbreviation for Source to Image Distance and may refer to the vertical distance from the focal point of the X-ray tube (110) to the receiving surface of the table bucky (220). SID (VL100) may change accordingly if the height of the X-ray tube (110) or the height of the table unit (200) changes. SID (VL100) may be a basic parameter used for deriving the actual angle (RA) and calculating the travel distance (HL200).

[0033] In this specification, "distance traveled (HL200)" may refer to the distance the table bucky (220) travels in the horizontal direction from the reference position of the table bucky (220) to the alignment position. During calibration, it may be a value detected by the position detection unit (230) after the user aligns the table bucky (220) with respect to the crosshairs of the collimator at each reference angle. During shooting, it may be a value calculated using the correction angle and the current SID (VL100).

[0034] In this specification, "corrected angle" refers to an angle derived by inputting an arbitrary sensor angle (SA) into a correction map (AM), and may represent an estimated value of the actual angle (RA). Since the corrected angle is an angle in which the error included in the sensor angle (SA) has been corrected, it can correspond more accurately to the actual optical axis direction of the X-ray tube (110).

[0035] FIG. 1 is a schematic perspective view of a medical device (1000) according to one embodiment of the present invention. FIG. 2 is a schematic front conceptual view of the configuration of a medical device (1000) according to one embodiment of the present invention.

[0036] Referring to FIGS. 1 and 2, the medical device (1000) may include a tube unit (100), a table unit (200), and a control unit (300).

[0037] The medical device (1000) may be a device for imaging the internal structure of the human body using X-rays. The medical device (1000) may support various imaging modes, including oblique projection. Oblique projection may be an imaging method in which X-rays are irradiated while the X-ray tube (110) is tilted at a predetermined angle to project a specific part of the human body in an oblique direction. Oblique projection may be used to effectively image anatomical structures such as the spine, pelvis, and sinuses.

[0038] In order to perform oblique imaging, the optical axis of the X-ray tube (110) may need to be precisely aligned with the center of the table bucky (220). If the optical axis deviates from the center of the table bucky (220), problems such as image distortion, reduced resolution, and grid cutoff may occur. Additionally, if re-imaging is required due to misalignment, unnecessary radiation exposure to the patient may increase. The medical device (1000) according to the present invention can accurately perform alignment of the table bucky (220) with respect to the X-ray tube (110) using a correction map (AM).

[0039] The tube unit (100) may include an X-ray tube (110), an angle sensor (120), and a lift (130).

[0040] The X-ray tube (110) may be configured to generate X-rays and irradiate a target for imaging. The X-ray tube (110) may include a cathode and an anode. When electrons emitted from the cathode are accelerated by a high voltage and collide with a target on the anode, X-rays may be generated. The generated X-rays may be emitted to the outside through an irradiation window formed in the housing of the X-ray tube (110).

[0041] In one embodiment, the X-ray tube (110) may include a collimator. The collimator can limit the X-ray irradiation area to prevent unnecessary radiation exposure. The collimator may include a light field function that emits a visible light beam. The light field can visually indicate the X-ray irradiation area to enable identification of the shooting position.

[0042] The collimator can project a crosshair onto a top board (210) by reflecting light generated from an internal light source through a mirror and passing it through a transparent acrylic window engraved with a crosshair. The crosshair may serve as a means to visually indicate the center position of the X-ray optical axis. In the calibration procedure, the user can verify the alignment position by aligning the center of the projected crosshair with a reference marker on the table bucky (220).

[0043] The X-ray tube (110) may be configured to be rotatable (tilting) around a rotation axis. The rotation axis may be a horizontal axis passing through the focal point of the X-ray tube (110). When the X-ray tube (110) rotates, the direction of the X-ray optical axis may change.

[0044] In the present specification, when the X-ray tube (110) is viewed from the front, the direction in which the optical axis tilts to the right between the X-ray tube (110) and the table bucky (220) by rotating clockwise is called the positive (+) rotation direction, and the direction in which the optical axis tilts to the left by rotating counterclockwise is called the negative (-) rotation direction.

[0045] For example, referring to FIG. 4, the X-ray tube (110) is shown tilted in a positive rotational direction so that the optical axis is tilted to the right, and referring to FIG. 5, the X-ray tube (110) is shown tilted in a negative rotational direction so that the optical axis is tilted to the left. In one embodiment, the rotational range of the X-ray tube (110) may be up to about 30 to 45 degrees in the positive rotational direction and the negative rotational direction, respectively.

[0046] An angle sensor (120) may be provided in an X-ray tube (110). The angle sensor (120) may output a sensor angle (SA) corresponding to the rotation angle of the X-ray tube (110). In one embodiment, the angle sensor (120) may include at least one of an encoder, a potentiometer, a MEMS gyroscope, or an inclinometer.

[0047] In one embodiment, the angle sensor (120) may be an incremental encoder or an absolute encoder. An incremental encoder can measure the relative rotation angle by outputting a change in the amount of rotation as a pulse signal. An absolute encoder can maintain the current angle even after power is cut off by outputting the absolute position of the rotation axis.

[0048] In one embodiment, the resolution of the angle sensor (120) may be in the range of 0.01 degrees to 0.5 degrees. Generally, the higher the resolution of the angle sensor (120), the more the precision of the sensor angle (SA) may be improved, but the cost of a high-resolution sensor may increase.

[0049] Meanwhile, even if the resolution of the sensor angle (SA) is high, a complex error may occur between the sensor angle (SA) and the actual optical axis direction due to the offset of the sensor itself, the machining tolerance of the tube support structure, and the installation deviation. This error may appear in the range of 0.03 to 0.5 degrees regardless of the resolution of the sensor, and even with this level of error, the alignment position of the table bucky (220) may deviate by more than several millimeters.

[0050] Since the correction map (AM) according to the present invention can correct such complex errors, high alignment accuracy can be secured even when using a relatively low-resolution angle sensor (120). Through this, alignment performance can be maintained while reducing the manufacturing cost of the medical device (1000) without using an expensive high-precision angle sensor.

[0051] In one embodiment, the sensor angle (SA) output from the angle sensor (120) may be displayed on the display of the control unit (300). The user can check and adjust the rotation angle of the X-ray tube (110) based on the sensor angle (SA) displayed on the display. However, since the sensor angle (SA) may contain complex errors as described above, there may be a difference between the sensor angle (SA) displayed on the display and the angle actually formed by the X-ray optical axis.

[0052] The lift (130) can adjust the height of the X-ray tube (110). The lift (130) can be configured in the form of a column (stand). The X-ray tube (110) can be mounted so as to be movable up and down along the lift (130). When the height of the X-ray tube (110) is changed by the lift (130), the SID (VL100) from the X-ray tube (110) to the table bucky (220) can be changed.

[0053] In one embodiment, the lift (130) may be driven by an electric motor. The lift (130) may include a lift position sensor for detecting the current height of the X-ray tube (110). The control unit (300) may receive the current height of the X-ray tube (110) from the lift position sensor and obtain an SID (VL100) by calculating the difference from the height of the table unit (200). Through this, the current SID (VL100) can be identified in real time even if the height of the X-ray tube (110) changes. In one embodiment, the movement range of the lift (130) may be approximately 600 mm to 1800 mm.

[0054] In another embodiment, the lift (130) may be operated manually. In this case, the user manually adjusts the height of the X-ray tube (110), and the current height may be detected by a scale or position sensor provided on the lift (130). The SID (VL100) may also be obtained by the user reading the scale and manually inputting it into the control unit (300).

[0055] In one embodiment, the lift (130) may include a counterbalancing mechanism. The counterbalancing mechanism may offset the weight of the X-ray tube (110) so that the user can adjust the height of the X-ray tube (110) with less force. The counterbalancing mechanism may be at least one of a spring type, a gas cylinder type, or a counterweight type.

[0056] In one embodiment, the tube unit (100) may be configured to be movable in a horizontal direction in addition to vertical movement along the lift (130). For example, the lift (130) may be mounted on a ceiling rail or a floor rail and slide along the major or minor axis of the table unit (200). In this case, the tube unit (100) may further include a horizontal position sensor for detecting the horizontal movement position.

[0057] When the tube unit (100) moves in a horizontal direction, the relative horizontal position between the X-ray tube (110) and the table bucky (220) may change. In this case, the control unit (300) receives the current horizontal position of the tube unit (100) from a horizontal position sensor and can correct the travel distance (HL200) by reflecting the amount of horizontal movement of the tube unit (100) when controlling the position of the table bucky (220). Through this, the alignment accuracy of the X-ray optical axis and the table bucky (220) can be maintained even when the tube unit (100) is in a horizontally moved state.

[0058] In another embodiment, the tube unit (100) may be configured as a fixed type that does not move in the horizontal direction. In this case, the position change of the X-ray tube (110) may be limited to vertical movement by the lift (130) and tilting around a rotation axis. For convenience of explanation, the following description will focus on an embodiment in which the tube unit (100) is fixed, but the same principle may be applied to an embodiment in which the tube unit (100) can move horizontally.

[0059] The table unit (200) may include a top board (210), a table buckle (220), and a position detection unit (230).

[0060] The top board (210) may be a plate-like member forming the upper surface of the table unit (200). The top board (210) may provide a surface on which the subject (patient) lies. The top board (210) may be formed of a material with high X-ray transmittance. In one embodiment, the top board (210) may be formed of at least one of carbon fiber (CFRP), phenolic resin, or acrylic material. A top board (210) made of carbon fiber material may simultaneously provide high strength and low X-ray absorption rate.

[0061] The table buckie (220) may be movably positioned on the lower part of the top board (210). The table buckie (220) may accommodate a detector (or film cassette) for forming an X-ray image. In one embodiment, the table buckie (220) may accommodate a digital detector (flat panel detector). In another embodiment, the table buckie (220) may accommodate a CR (Computed Radiography) cassette.

[0062] The table bucky (220) may be configured to slide along the longitudinal axis of the table unit (200) from the bottom of the top board (210). The sliding of the table bucky (220) may be guided by a rail or a guide member. In one embodiment, the sliding of the table bucky (220) may be automatically driven by an electric motor. In another embodiment, the sliding of the table bucky (220) may be performed by manual operation by a user.

[0063] In one embodiment, the table bucky (220) may include a grid for removing scattered radiation. The grid may have a structure in which lead strips parallel to the X-ray transmission direction are arranged at regular intervals. The grid must be precisely aligned with the X-ray optical axis to maximize the effect of removing scattered radiation. If the grid is misaligned with the X-ray optical axis, grid cutoff may occur, causing the density of the image to become non-uniform. Therefore, the precise alignment of the table bucky (220) can also contribute to preventing grid cutoff.

[0064] The position detection unit (230) can detect the position of the table bucky (220). The position detection unit (230) can detect the distance traveled from the reference position of the table bucky (220). The reference position can be set to a position where the center of the table bucky (220) is aligned with the X-ray optical axis when the X-ray tube (110) is at 0 degrees (vertical state). In an embodiment where the tube unit (100) is movable in the horizontal direction as described above, since the vertical projection position of the X-ray optical axis changes when the horizontal position of the tube unit (100) changes, the reference position can also be updated in correspondence with the current horizontal position of the tube unit (100). In this case, the control unit (300) can automatically update the reference position based on position information received from the horizontal position sensor of the tube unit (100).

[0065] In one embodiment, the position detection unit (230) may include at least one of a linear encoder, a linear potentiometer, or a position detection switch. The linear encoder may include a scale positioned along the sliding path of the table bucky (220) and a read head mounted on the table bucky (220). The linear encoder can detect the travel distance of the table bucky (220) with high resolution (e.g., 0.1 mm or less). The linear potentiometer can detect the position by utilizing the principle that the resistance value changes according to the movement of the table bucky (220). Although the linear potentiometer may have lower resolution than the linear encoder, it may have a simple structure and be inexpensive.

[0066] In one embodiment, the position detection unit (230) can transmit the position information of the detected table bucket (220) to the control unit (300) in real time. The control unit (300) can calculate the current travel distance (HL200) of the table bucket (220) based on the received position information. Additionally, when the control unit (300) automatically controls the position of the table bucket (220), it can determine whether the table bucket (220) has reached a target position based on feedback from the position detection unit (230).

[0067] In one embodiment, the position detection unit (230) may include a home position detection function. The home position detection function may be a function that detects when the table buckle (220) is located at a reference position. Home position detection may be performed by at least one of a micro switch, an optical sensor, or a magnetic sensor. The reference position can be accurately set at the start of the calibration procedure by the home position detection function.

[0068] In one embodiment, the table unit (200) may be configured to be height-adjustable. The table unit (200) may include a base portion fixed to the floor and a table body disposed on the base portion so as to be movable in the vertical direction. The table body may include a top board (210), a table buckle (220), and a position detection unit (230). The table unit (200) may include a table height sensor for detecting the current height of the table body. In one embodiment, the table height sensor may be an encoder.

[0069] When the height of the table unit (200) changes, the SID (VL100) from the X-ray tube (110) to the table buckie (220) may change. The control unit (300) receives the current height of the X-ray tube (110) from a lift position sensor provided on the lift (130) and receives the current height of the table unit (200) from a table height sensor, and can calculate the SID (VL100) based on the difference between the two. Through this, the current SID (VL100) can be accurately determined even if either the height of the X-ray tube (110) or the height of the table unit (200) changes.

[0070] The control unit (300) receives data from the angle sensor (120) and the position detection unit (230) to generate a correction map (AM), and can control the position of the table bucket (220) based on the correction map (AM).

[0071] Specifically, the control unit (300) may be configured to obtain a sensor angle (SA) at each reference angle from an angle sensor (120) while the X-ray tube (110) is rotated to a plurality of reference angles, obtain a SID (VL100) from the X-ray tube (110) to a table buckie (220) and a travel distance (HL200) from a reference position of the table buckie (220) to an alignment position aligned with the X-ray optical axis, derive an actual angle (RA) from the SID (VL100) and the travel distance (HL200), configure the sensor angle (SA) and the actual angle (RA) into a pair of correction nodes (AM_N), and generate a correction map (AM) that derives a correction angle corresponding to any sensor angle (SA) based on the plurality of correction nodes (AM_N).

[0072] Additionally, the control unit (300) may be configured to obtain a correction angle corresponding to an arbitrary sensor angle (SA) based on a correction map (AM) when shooting, and to calculate a travel distance (HL200) corresponding to the correction angle and the current SID (VL100).

[0073] In one embodiment, the control unit (300) may include a processor, memory, and a display. The processor may perform operations for generating a calibration map (AM), deriving an actual angle (RA), and controlling the position of the table bucky (220). The memory may store data of the calibration map (AM), calibration history, and control parameters. In one embodiment, the memory may include non-volatile memory (FRAM, EEPROM, or flash memory) so that the calibration map (AM) data may be retained even when the power is cut off. The display may display at least one of the current sensor angle (SA), actual angle (RA), SID (VL100), the position of the table bucky (220), and the calibration status.

[0074] In one embodiment, the control unit (300) may include a verification means for verifying the integrity of the correction map (AM). The verification means may verify whether the correction map (AM) data is corrupted using a Cyclic Redundancy Check (CRC) or a checksum. If corruption of the correction map (AM) data is detected, the control unit (300) may output a notification to the user requesting recalibration.

[0075] In one embodiment, the control unit (300) may include a motor drive unit for automatically controlling the position of the table bucket (220) or may be connected to communicate with an external motor drive unit. The control unit (300) may output a control signal to automatically move the table bucket (220) to a position corresponding to the travel distance (HL200) calculated by the correction map (AM).

[0076] In one embodiment, the control unit (300) may include a wired or wireless communication interface. The control unit (300) may receive a shooting protocol by communicating with a hospital information system (HIS), a picture archiving and transmission system (PACS), or a radiology information system (RIS). The control unit (300) may be configured to automatically reference a correction map (AM) based on the target angle included in the received shooting protocol and to control the position of the table bucky (220).

[0077] FIG. 3 is a flowchart schematically illustrating a calibration procedure according to an embodiment of the present invention. FIG. 4 is a conceptual diagram schematically illustrating the process of deriving the actual angle (RA) when the X-ray tube (110) is tilted to the right according to an embodiment of the present invention. FIG. 5 is a conceptual diagram schematically illustrating the process of deriving the actual angle (RA) when the X-ray tube (110) is tilted to the left according to an embodiment of the present invention. FIG. 6 is a conceptual diagram schematically illustrating a correction map (AM) according to an embodiment of the present invention. FIG. 7 is a conceptual diagram schematically illustrating a correction map (AM_H) reflecting hysteresis according to an embodiment of the present invention.

[0078] Referring to FIGS. 3 to 7, the tube angle correction method according to the present invention may include a process of generating a correction map (AM) through a correction procedure. The correction procedure may be performed when installing the medical device (1000), during a periodic inspection, or after a component of the tube unit (100) or table unit (200) is replaced.

[0079] Referring to FIG. 3, the calibration procedure may include a sensor angle acquisition step (S110), a SID acquisition step (S120), a travel distance acquisition step (S130), an actual angle derivation step (S140), a calibration node configuration step (S150), a completion determination step (S160), and a calibration map generation step (S170).

[0080] In the sensor angle acquisition step (S110), the X-ray tube (110) may be rotated to one of a plurality of reference angles, and the sensor angle (SA) may be acquired from the angle sensor (120). The plurality of reference angles may be angles that are pre-set to ensure the precision of the calibration. In one embodiment, the plurality of reference angles may be set at predetermined intervals in the positive direction and the negative direction, respectively, including 0 degrees (origin). For example, the plurality of reference angles may be set to a total of 9 points, including 0 degrees, +5 degrees, +10 degrees, +15 degrees, +20 degrees, -5 degrees, -10 degrees, -15 degrees, and -20 degrees.

[0081] In another embodiment, a plurality of reference angles can be set with a narrow interval in an angle range with a high shooting frequency and a wide interval in an angle range with a low shooting frequency. For example, they can be set with a 2.5-degree interval in the 0 to 10-degree range and with a 5-degree interval in the 10 to 20-degree range. Through this, the correction precision can be improved in the angle range frequently used in clinical practice.

[0082] In another embodiment, the number of reference angles may be 5 to 15. As the number of reference angles increases, the precision of the correction map (AM) may be improved, but the time required for the calibration procedure may increase. As the number of reference angles decreases, the calibration procedure may be faster, but the precision of the correction map (AM) may decrease. In one embodiment, the number of reference angles may be 7 to 9, and within this range, a balance between calibration time and calibration precision can be ensured.

[0083] In one embodiment, the acquisition of the sensor angle (SA) may be performed after a predetermined stabilization time has elapsed at each reference angle. Since residual vibration due to inertia may exist immediately after the X-ray tube (110) is rotated, the measurement precision can be improved by acquiring the sensor angle (SA) after waiting for the stabilization time. The stabilization time may be 0.5 seconds to 3 seconds.

[0084] In one embodiment, the acquisition of the sensor angle (SA) may be repeated multiple times, and the average value may be used. For example, the sensor angle (SA) may be measured repeatedly 3 to 10 times at each reference angle, and the average of the measurements may be used as the sensor angle (SA) at the corresponding reference angle. Through this, measurement errors caused by sensor noise can be reduced.

[0085] In the vertical separation distance acquisition step (S120), the SID (VL100) from the X-ray tube (110) to the table bucky (220) can be acquired. The SID (VL100) may be the vertical distance from the focal point of the X-ray tube (110) to the receiving surface of the table bucky (220). In one embodiment, the SID (VL100) may be calculated by detecting the current height of the X-ray tube (110) from a position sensor provided on the lift (130) and subtracting the height of the table unit (200).

[0086] In one embodiment, the SID (VL100) is acquired once at the start of the calibration procedure and the same value can be used throughout the calibration procedure. That is, the height of the X-ray tube (110) may not change during the calibration procedure. In another embodiment, the SID (VL100) can be acquired individually at each reference angle. In this case, an accurate actual angle (RA) can be derived even if there is a change in the height of the lift (130).

[0087] In one embodiment, SID (VL100) may be in the range of about 900 mm to 1200 mm. The shorter the SID (VL100), the larger the actual angle (RA) can be calculated for the same travel distance (HL200). The longer the SID (VL100), the smaller the actual angle (RA) can be calculated for the same travel distance (HL200).

[0088] In the horizontal separation distance acquisition step (S130), the distance traveled (HL200) between the reference position of the table bucky (220) and the alignment position of the table bucky (220) aligned with the optical axis of the X-ray tube (110) at the current reference angle can be acquired.

[0089] Here, alignment may mean a state in which the center of the optical axis of the X-ray emitted from the X-ray tube (110) coincides with the center of the detector housed in the table bucky (220). When imaging is performed in an aligned state, distortion of the X-ray image can be minimized and grid cutoff can be prevented.

[0090] The reference position may be the position of the table bucky (220) where the X-ray optical axis is aligned with the center of the table bucky (220) when the X-ray tube (110) is at 0 degrees (vertical state). The reference position may be set at the first step of the calibration procedure. Specifically, after positioning the X-ray tube (110) at 0 degrees, the user may move the table bucky (220) so that the center of the crosshairs projected by the aforementioned collimator coincides with the reference marker of the table bucky (220). The position of the table bucky (220) at this time may be set as the reference position.

[0091] The alignment position may be the position where the table bucky (220) is moved so that the X-ray optical axis is aligned with the center of the table bucky (220) at each reference angle. Specifically, when the X-ray tube (110) is tilted to a specific reference angle (e.g., +10 degrees), the X-ray optical axis is tilted so that the center of the optical axis deviates from the current position of the table bucky (220). At this time, the user can manually or automatically slide the table bucky (220) while visually checking the center of the crosshairs projected by the collimator to adjust the position so that the center of the crosshairs aligns again with the reference marker of the table bucky (220). When the center of the crosshairs aligns with the reference marker, the X-ray optical axis and the center of the table bucky (220) are aligned at that reference angle, so the position of the table bucky (220) at this time can be determined as the alignment position.

[0092] The travel distance (HL200) may be the horizontal distance from the reference position to the alignment position. Once the alignment position is determined, the position detection unit (230) can detect the distance traveled by the table buck (220) from the reference position to the alignment position and transmit it to the control unit (300) as the travel distance (HL200). That is, when the user adjusts the position of the table buck (220) based on the crosshairs, the position detection unit (230) can automatically detect the travel distance and obtain the travel distance (HL200).

[0093] In one embodiment, the sign of the travel distance (HL200) may be determined according to the direction of movement of the table bucky (220). For example, if it moves in a positive direction (see FIG. 4) from a reference position, the travel distance (HL200) may have a positive value, and if it moves in a negative direction (see FIG. 5), the travel distance (HL200) may have a negative value.

[0094] Referring to FIGS. 4 and 5, in the actual angle derivation step (S140), the actual angle (RA) can be derived using the travel distance (HL200) and SID (VL100).

[0095] FIG. 4 may show the X-ray tube (110) tilted to the right, and FIG. 5 may show the X-ray tube (110) tilted to the left. As illustrated in FIG. 4 and FIG. 5, the focal point of the X-ray tube (110), the alignment position of the table bucky (220), and the direct position of the X-ray tube (110) may form the three vertices of a right triangle. In this right triangle, the length of the vertical side may correspond to SID (VL100), and the length of the horizontal side may correspond to the travel distance (HL200). The actual angle (RA) may be defined as the angle between the vertical side and the hypotenuse (direction of the X-ray optical axis).

[0096] In one embodiment, the actual angle (RA) can be calculated as an inverse tangent function of the ratio of the travel distance (HL200) to the SID (VL100). That is, the actual angle (RA) can be arctan(travel distance / SID). This formula can directly calculate the geometric angle formed by the X-ray optical axis based on the actual imaging geometry. Unlike the sensor angle (SA), the actual angle (RA) is not affected by sensor offset, machining tolerances, and installation deviations, so it can be used as a reference value for correction.

[0097] As illustrated in FIG. 4, when the X-ray tube (110) is tilted to the right, the table bucky (220) moves to the right from the reference position to form a positive displacement (HL200), and a positive actual angle (RA) can be derived in correspondence. As illustrated in FIG. 5, when the X-ray tube (110) is tilted to the left, the table bucky (220) moves to the left from the reference position to form a negative displacement (HL200), and a negative actual angle (RA) can be derived in correspondence.

[0098] As described above, the value displayed on the control unit (300) in FIGS. 4 and 5 is the sensor angle (SA), and the geometrically depicted angle may be the actual angle (RA). The difference between the sensor angle (SA) and the actual angle (RA) may be the object to be corrected by the correction map (AM).

[0099] In the correction node configuration step (S150), the sensor angle (SA) acquired at the current reference angle and the derived actual angle (RA) can be configured as a pair of correction nodes (AM_N). The correction nodes (AM_N) may be ordered pairs of (sensor angle, actual angle). Since correction nodes (AM_N) are configured for each of multiple reference angles, multiple correction nodes (AM_N) can be secured once the correction procedure is completed.

[0100] In the completion determination step (S160), it can be determined whether measurements for all reference angles have been completed. If measurements for all reference angles have not been completed (No), the process can be returned to the sensor angle acquisition step (S110) and the same process can be repeated for the next reference angle. If measurements for all reference angles have been completed (Yes), the process can proceed to the correction map generation step (S170).

[0101] In the correction map generation step (S170), a correction map (AM) can be generated based on a plurality of correction nodes (AM_N). The correction map (AM) can be configured to derive a corresponding actual angle (RA) when an arbitrary sensor angle (SA) is input.

[0102] Referring to FIG. 6, the correction map (AM) can be defined in a coordinate system where the x-axis is the sensor angle (SA) and the y-axis is the actual angle (RA). A plurality of correction nodes (AM_N) can each be represented as points corresponding to the (sensor angle, actual angle) coordinates.

[0103] The definition area (AM_SA) of the correction map (AM) may be a range of sensor angles from the correction node having the minimum sensor angle to the correction node having the maximum sensor angle among a plurality of correction nodes (AM_N). For example, if the reference angle is from -20 degrees to +20 degrees, the definition area (AM_SA) may be a range from the sensor angle corresponding to -20 degrees to the sensor angle corresponding to +20 degrees.

[0104] Within the defined region (AM_SA), multiple correction nodes (AM_N) can be connected by cubic interpolation for shape-preserving intervals to derive the actual angle (RA) corresponding to any sensor angle (SA). Cubic interpolation for shape-preserving intervals may be an interpolation method that connects adjacent correction nodes (AM_N) using a cubic polynomial, while limiting the slope of each interval so that an overshoot or undershoot does not occur in the interpolation curve that deviates from the increasing or decreasing trend of the correction nodes (AM_N). Through this, it is possible to prevent the interpolation curve from exhibiting physically irrational shapes (e.g., intervals where the sensor angle increases but the actual angle decreases).

[0105] In one embodiment, cubic interpolation for each shape-preserving section can be performed by the PCHIP (Piecewise Cubic Hermite Interpolating Polynomial) algorithm. The PCHIP algorithm can preserve monotonicity for each section while satisfying both the function value and the slope at each correction node (AM_N).

[0106] In another embodiment, at least one of linear interpolation, quadratic spline interpolation, or cubic spline interpolation may be used as the interpolation method. However, linear interpolation may result in a bending point between correction nodes (AM_N), causing the correction value to change discontinuously. Cubic spline interpolation forms a smooth curve overall, but overshoot may occur between correction nodes (AM_N). In contrast, shape-preserving interval cubic interpolation can form a smooth curve while preventing overshoot, so it may be more suitable for correcting the sensor angle (SA).

[0107] Outside the defined region (AM_SA), the actual angle (RA) corresponding to an arbitrary sensor angle (SA) can be derived by linear extrapolation using the endpoint slope. Specifically, if a sensor angle smaller than the minimum sensor angle in the defined region (AM_SA) is input, the actual angle (RA) can be derived by linearly extending the value using the slope at the correction node with the minimum sensor angle. Similarly, if a sensor angle larger than the maximum sensor angle in the defined region (AM_SA) is input, the actual angle (RA) can be derived by linearly extending the value using the slope at the correction node with the maximum sensor angle.

[0108] Linear extrapolation can provide correction values ​​even in areas where correction data does not exist. This allows for stable correction performance over a wide range of angles to be secured using only a limited number of correction points. However, since correction accuracy may be lower in the extrapolation area than in the interpolation area, it may be advisable to set the reference angle range during correction to encompass the angle range used in actual shooting.

[0109] In one embodiment, the correction map (AM) may be generated separately into a first correction map corresponding to a positive rotation direction and a second correction map corresponding to a negative rotation direction. The first correction map may be generated based on a correction node (AM_N) obtained at a reference angle of the positive rotation direction (e.g., 0 degrees, +5 degrees, +10 degrees, +15 degrees, +20 degrees). The second correction map may be generated based on a correction node (AM_N) obtained at a reference angle of the negative rotation direction (e.g., 0 degrees, -5 degrees, -10 degrees, -15 degrees, -20 degrees). Since the gravitational load and friction conditions acting on the X-ray tube (110) may differ in the positive rotation direction and the negative rotation direction, the correction accuracy may be improved by generating a correction map separately for each direction.

[0110] When shooting, the control unit (300) can obtain the actual angle (RA) by selecting a first correction map when the current sensor angle (SA) is a positive value and a second correction map when it is a negative value.

[0111] In another embodiment, the correction map (AM) may be generated as a single correction map by integrating the correction nodes (AM_N) of the positive rotation direction and the negative rotation direction. In FIG. 6, the positive direction correction node (AM_N) and the negative direction correction node (AM_N) are shown consecutively in a single coordinate system, which may correspond to an embodiment of a single correction map.

[0112] In one embodiment, when generating a correction map (AM), the sensor angle (SA) and the actual angle (RA) can be converted into tangent functions to perform interpolation. Since the actual angle (RA) is defined as arctan(HL200 / VL100), tan(RA) = HL200 / VL100, so in the tangent domain, the actual angle can be converted into a simple ratio of distances. Accordingly, interpolation in the tangent domain may be more stable than interpolation in the angle domain. The result interpolated in the tangent domain can be converted back to the angle domain through an inverse tangent function.

[0113] Specifically, when an arbitrary sensor angle (SA) is input, tan(sensor angle) is input into the correction map (AM) to derive a corrected tangent value yq, and the corrected angle can be calculated by the formula Corrected Angle = arctan(yq). Here, yq is a value derived by interpolation or extrapolation of the correction map (AM), and may be an estimated value based on tan(actual angle) data acquired during calibration. In this way, the correction map (AM) operates in the tangent domain, and the final corrected angle can be restored to the angle domain by an inverse tangent transformation.

[0114] In one embodiment, data of the correction map (AM) may be stored in a non-volatile memory of the control unit (300). The non-volatile memory may be at least one of Ferroelectric RAM (FRAM), EEPROM, or flash memory. FRAM may be suitable for storing the correction map (AM) where frequent data updates are required, as it has a fast read / write speed and a write life that is virtually infinite.

[0115] In one embodiment, the data structure of the correction map (AM) may include SID (VL100) information, a sensor angle array and an actual angle array of a positive direction correction node (AM_N), a sensor angle array and an actual angle array of a negative direction correction node (AM_N), and a CRC32 checksum for the integrity verification described above.

[0116] Referring to FIG. 7, the hysteresis correction map (AM_H) can be configured to derive different actual angles (RA) depending on the rotational approach direction of the X-ray tube (110) for the same sensor angle (SA).

[0117] The X-ray tube (110) is a structure having a significant weight, and the assembly state of the mechanical parts supporting it, such as a stand, rail, rotation axis, link mechanism, gear, and bearing, may interact in a complex manner. There are machining tolerances and clearances between the mechanical parts, and the direction of the gravitational load and friction conditions may vary depending on the rotational direction of the X-ray tube (110).

[0118] As a result, even if the same angle position is reached, the clearance of the mechanism part acts differently depending on the rotational approach direction, so a direction-dependent deviation may occur in the output value of the angle sensor (120).

[0119] This direction-dependent deviation can be called mechanical hysteresis. For example, even when reaching the same +10 degree position, the output value of the angle sensor (120) may be slightly different depending on whether the approach is made in the direction of increasing the angle (+5 degrees to +10 degrees) or in the direction of decreasing the angle (+15 degrees to +10 degrees).

[0120] As shown in FIG. 7, in the hysteresis correction map (AM_H), two curves with different arrow directions may be displayed at the same sensor angle (SA) position. The curve when approaching in the direction of increasing angle and the curve when approaching in the direction of decreasing angle may represent slightly different paths.

[0121] In one embodiment, the correction procedure of the hysteresis correction map (AM_H) may acquire correction nodes (AM_N) by approaching each reference angle from both directions. For example, for a reference angle of +10 degrees, correction nodes (AM_N) may be acquired by approaching from +5 degrees to +10 degrees, and separately, correction nodes (AM_N) may be acquired by approaching from +15 degrees to +10 degrees. Based on the correction nodes (AM_N) acquired in both directions, a hysteresis correction map (AM_H) that derives different actual angles (RA) for each rotational approach direction may be generated.

[0122] In another embodiment, the hysteresis correction map (AM_H) can estimate the correction value during reverse approach (direction in which the angle decreases) in the positive rotation direction using correction data in the negative rotation direction, without separately acquiring the correction node (AM_N) while approaching each reference angle from both directions.

[0123] Specifically, calibration data measured in the direction where the absolute value of the angle increases in the negative direction (e.g., 0 degrees → -5 degrees → -10 degrees) may be similar to the hysteresis characteristics when approaching in the direction where the angle decreases in the positive direction (e.g., +10 degrees → +5 degrees → degrees), since it is due to physically identical counterclockwise rotation.

[0124] Similarly, calibration data measured in the direction of increasing angle from the positive direction can be utilized to estimate hysteresis characteristics when approaching in the direction of decreasing absolute angle value from the negative direction. This allows for the correction of errors caused by hysteresis without separately measuring approaches in both directions from each reference angle, thereby reducing the time required for the calibration procedure.

[0125] In one embodiment, the current rotational approach direction of the X-ray tube (110) during actual shooting can be determined by comparing the previous sensor angle (SA) and the current sensor angle (SA). If the current sensor angle (SA) is greater than the previous sensor angle (SA), it can be determined that the approach is in a direction of increasing angle. If the current sensor angle (SA) is smaller than the previous sensor angle (SA), it can be determined that the approach is in a direction of decreasing angle. A correction curve corresponding to the determined rotational approach direction can be selected to derive the actual angle (RA). In another embodiment, the current rotational approach direction can be determined by the driving command direction of the motor driving the X-ray tube (110).

[0126] In one embodiment, the error in the sensor angle (SA) due to hysteresis may be in the range of about 0.01 degrees to 0.1 degrees. An error of this magnitude may result in the alignment position of the table bucky (220) deviating by about 0.17 mm to 1.75 mm in an environment where the SID (VL100) is 1000 mm. By using a hysteresis correction map (AM_H), this error can be corrected to improve alignment accuracy.

[0127] In one embodiment, when the magnitude of the hysteresis is less than or equal to a preset threshold (e.g., 0.02 degrees), the control unit (300) may use a single correction map (AM) instead of a hysteresis correction map (AM_H). This allows unnecessary complexity to be eliminated when the hysteresis is at a negligible level.

[0128] In one embodiment, the correction map (AM) or hysteresis correction map (AM_H) may be automatically verified after the completion of the calibration procedure. The verification method may be to calculate the residual between the corrected angle derived by the correction map (AM) and the actual angle (RA) measured during calibration for each reference angle used in the calibration. If the residual is within a preset tolerance range (e.g., 0.01 degrees), the calibration may be determined to have been successfully completed. If the residual exceeds the tolerance range, recalibration may be requested.

[0129] In one embodiment, the control unit (300) may store a calibration history including the creation date and time of the calibration map (AM), the reference angle used during calibration, the SID (VL100), the sensor angle (SA) and actual angle (RA) of each calibration node (AM_N), the residual, and information on the calibration performer. The calibration history may be utilized for maintenance and quality control of the medical device (1000).

[0130] FIG. 8 is a flowchart schematically illustrating a practical bucky control procedure according to an embodiment of the present invention. FIG. 9 is a flowchart schematically illustrating a feedback-based correction map update procedure according to an embodiment of the present invention.

[0131] Referring to FIG. 8, the actual bucky control procedure may be a process of automatically controlling the position of the table bucky (220) at any sensor angle (SA) based on a correction map (AM) generated by a correction procedure. The actual bucky control procedure may include a sensor angle acquisition step (S210), a correction angle acquisition step (S220), a SID acquisition step (S230), a movement distance calculation step (S240), a bucky position control step (S250), and a shooting execution step (S260).

[0132] In the sensor angle acquisition step (S210), the current sensor angle (SA) of the X-ray tube (110) can be acquired from the angle sensor (120). When a user (radiologist) rotates the X-ray tube (110) to a target angle, the angle sensor (120) can output a sensor angle (SA) corresponding to the current rotation angle. The control unit (300) can receive the output sensor angle (SA).

[0133] In one embodiment, the acquisition of the sensor angle (SA) can be performed continuously in real time. The control unit (300) can acquire the sensor angle (SA) at a predetermined sampling period (e.g., 10 ms to 100 ms) to monitor the rotational state of the X-ray tube (110) in real time.

[0134] In one embodiment, the control unit (300) can proceed to a subsequent step by determining that the X-ray tube (110) is settled at a target angle when the rate of change of the sensor angle (SA) satisfies a preset stabilization condition (e.g., a change amount of 0.01 degrees or less for three consecutive times or more). This prevents correction from being performed while the X-ray tube (110) is in motion.

[0135] In the actual angle acquisition step (S220), the control unit (300) can acquire a correction angle corresponding to the current sensor angle (SA) by referring to a previously stored correction map (AM). As described above, since the correction map (AM) is generated in the calibration procedure and stored in the non-volatile memory of the control unit (300), when shooting, the current sensor angle (SA) can be input into the correction map (AM) without a separate calibration process, and the corresponding correction angle can be acquired immediately.

[0136] In one embodiment, when a hysteresis correction map (AM_H) is used, the control unit (300) can determine the current rotation approach direction by comparing the previous sensor angle (SA) and the current sensor angle (SA), and obtain the actual angle (RA) by selecting a correction curve corresponding to the determined direction.

[0137] In the vertical separation distance acquisition step (S230), the SID (VL100) from the current X-ray tube (110) to the table bucky (220) can be acquired. The SID (VL100) during the calibration procedure and the SID (VL100) during the current imaging may differ due to changes in the height of the X-ray tube (110). Therefore, it may be desirable to acquire the current SID (VL100) for each imaging session.

[0138] In one embodiment, the SID (VL100) can be automatically obtained from a position sensor provided in the lift (130). In another embodiment, the SID (VL100) can be manually entered by a user. For example, a user can read a scale displayed on the lift (130) and input it into the control unit (300).

[0139] In this way, since the correction map (AM) defines the relationship between the sensor angle (SA) and the actual angle (RA) in the angle domain, the same correction map (AM) can be effectively applied even if the SID (VL100) differs from that at the time of calibration. That is, the correction map (AM) can provide an angle correction relationship independent of the SID (VL100), and the SID (VL100) can be reflected in the step of calculating the travel distance (HL200) after angle correction.

[0140] In the distance calculation step (S240), the distance (HL200) that the table bucket (220) must travel can be calculated using the acquired correction angle and the current SID (VL100). In one embodiment, the distance (HL200) can be calculated as the product of the SID (VL100) and the tangent value of the correction angle. That is, distance = SID × tan(correction angle).

[0141] For example, if the correction angle is 10 degrees and the SID (VL100) is 1000 mm, the travel distance (HL200) can be calculated as approximately 176.3 mm. If the actual angle (RA) is 10 degrees and the SID (VL100) is 1100 mm, the travel distance (HL200) can be calculated as approximately 193.9 mm. In this way, even with the same correction angle, the travel distance of the table bucky (220) can vary depending on the SID (VL100).

[0142] In the bucky position control step (S250), the table bucky (220) can be moved to a position corresponding to the calculated travel distance (HL200). The control unit (300) can control the table bucky (220) to a position moved by the travel distance (HL200) from the reference position.

[0143] In one embodiment, the control unit (300) receives the current position of the table buckie (220) from the position detection unit (230), calculates the difference from the target position, and outputs a motor drive signal. When the table buckie (220) reaches the target position, the motor drive may be stopped. Through this, automatic alignment can be performed without the user needing to manually move the table buckie (220).

[0144] In one embodiment, the control unit (300) may perform closed-loop position control based on feedback from the position detection unit (230). The closed-loop position control may include Proportional-Integral-Derivative (PID) control or a variation thereof. By the closed-loop position control, the position error of the table bucky (220) may converge within a preset allowable range (e.g., ±0.5 mm).

[0145] In another embodiment, the movement of the table bucket (220) may be performed manually. In this case, the control unit (300) may display the difference between the target position and the current position numerically or graphically on a display and guide the user to move the table bucket (220) manually to reach the target position. The control unit (300) may output an alignment completion notification (visual or auditory notification) when the current position matches the target position.

[0146] In the shooting execution step (S260), after the position of the table bucky (220) is controlled, X-rays can be irradiated to perform the shooting. X-rays emitted from the X-ray tube (110) can pass through the target to be shot and reach the detector housed in the table bucky (220). Since the X-ray optical axis and the center of the table bucky (220) are accurately aligned by the correction map (AM), image distortion can be minimized and grid cutoff can be prevented.

[0147] In one embodiment, the control unit (300) can finally check the alignment status before performing the shot. Specifically, the control unit (300) can check whether the alignment error is within a preset allowable range by comparing the current sensor angle (SA), the actual angle (RA) obtained by the correction map (AM), the current SID (VL100), the calculated travel distance (HL200), and the current position of the table bucky (220). If the alignment error exceeds the allowable range, the control unit (300) can block the shot or output a warning to the user. This prevents shooting in a poorly aligned state, thereby reducing unnecessary radiation exposure and re-shooting for the patient.

[0148] Referring to FIG. 9, the feedback-based correction map update procedure may be performed after the bucky position control step (S250) of FIG. 8. The feedback-based correction map update procedure may include a readjustment determination step (S310), a readjustment movement distance acquisition step (S320), a correction node creation step (S330), and a correction map update step (S340).

[0149] In the readjustment determination step (S310), the user can determine whether the position of the table bucket (220) has been readjusted.

[0150] After the position of the table buckie (220) is automatically controlled by the correction map (AM), if the user determines that there is a fine alignment error when checking the crosshairs projected by the collimator, the user can manually readjust the position of the table buckie (220). In one embodiment, the user can finely adjust the position of the table buckie (220) using the control panel of the control unit (300) or the manual operation handle of the table unit (200).

[0151] If no readjustment by the user occurs (No), the process proceeds to the shooting execution step (S260) and shooting can be performed immediately. If readjustment by the user occurs (Yes), the process proceeds to the readjustment movement distance acquisition step (S320).

[0152] In one embodiment, the control unit (300) monitors the output value of the position detection unit (230) after the bucky position control step (S250) and can automatically determine that readjustment by the user has occurred if the position change of the table bucky (220) exceeds a preset threshold (e.g., 0.5 mm).

[0153] In another embodiment, the user can explicitly indicate that the readjustment is complete by pressing the "Readjustment Confirmation" button displayed on the display of the control unit (300).

[0154] In the readjustment travel distance acquisition step (S320), the readjustment travel distance of the table bucky (220) readjusted by the user can be acquired. The readjustment travel distance may be the horizontal distance from the reference position to the current position of the readjusted table bucky (220). The readjustment travel distance may be detected by the position detection unit (230).

[0155] In the correction node creation step (S330), a new correction node (AM_N) can be created based on the readjustment travel distance. Specifically, a new actual angle (RA') can be calculated using the readjustment travel distance and the current SID (VL100). The new actual angle (RA') can be calculated as arctan(readjustment travel distance / SID). The control unit (300) can create a pair of new correction nodes (AM_N) using the current sensor angle (SA) and the new actual angle (RA').

[0156] In the correction map update step (S340), the correction map (AM) can be updated based on the new correction node (AM_N).

[0157] In one embodiment, if a new correction node (AM_N) falls within the same sensor angle (SA) range as a correction node (AM_N) already present in the existing correction map (AM), the actual angle (RA) of the existing correction node (AM_N) may be replaced (updated) with a new actual angle (RA'). If the new correction node (AM_N) is located between existing correction nodes (AM_N), the new correction node (AM_N) may be added to the existing correction map (AM) to increase the density of the correction nodes (AM_N). An increase in the density of the correction nodes (AM_N) improves the precision of interpolation, thereby improving the accuracy of the correction map (AM).

[0158] In one embodiment, when a new correction node (AM_N) is added, the control unit (300) can regenerate the interpolation function of the correction map (AM) based on the updated set of correction nodes (AM_N). The regeneration of the interpolation function can be performed by third-order interpolation for each shape-preserving interval.

[0159] In another embodiment, if the new correction node (AM_N) has a value significantly different from the existing correction node (AM_N), the control unit (300) may not immediately reflect the new correction node (AM_N) and may request confirmation from the user. For example, if the difference between the new actual angle (RA') and the existing actual angle (RA) exceeds a preset threshold (e.g., 0.5 degrees), the control unit (300) may output a warning on the display and request approval from the user. This prevents contamination of the correction map (AM) due to user operation errors.

[0160] In one embodiment, the control unit (300) may store the data of the updated correction map (AM) in non-volatile memory and recalculate and store the CRC32 checksum together. This allows the updated correction map (AM) to be maintained even after the power is cut off.

[0161] In one embodiment, the control unit (300) may store the update history of the calibration map (AM). The update history may include the update date and time, the value of the calibration node (AM_N) before the update, the value of the calibration node (AM_N) after the update, and the reason for the update (user readjustment). The update history may be used to track the trend of change in the calibration map (AM). For example, if readjustment occurs repeatedly within a specific angle range, it may indicate that mechanical wear or sensor degradation is progressing within that range. In this case, the control unit (300) may output a notification recommending inspection or recalibration of the relevant part to the user.

[0162] In one embodiment, if the number of updates to the correction map (AM) exceeds a preset number (e.g., 50 times), the control unit (300) may recommend re-performing the entire correction procedure. Since the overall consistency of the correction map (AM) may deteriorate if multiple local updates accumulate, periodic full re-correction may be desirable.

[0163] In one embodiment, the control unit (300) may automatically perform verification after updating the correction map (AM). The verification may be to calculate the residual between the travel distance (HL200) calculated by the updated correction map (AM) and the actual position readjusted by the user. If the residual is within a preset allowable range (e.g., 0.3 mm), it may be determined that the update has been successfully completed.

[0164] After the correction map update step (S340), the process proceeds to the shooting execution step (S260) to perform X-ray irradiation and shooting.

[0165] In this way, through the feedback-based correction map update procedure according to the present invention, fine alignment errors detected by the user at the shooting site can be reflected in the correction map (AM) in real time. Through this, the accuracy of the correction map (AM) can be continuously improved with repeated use of the medical device (1000), and the increase in alignment errors caused by mechanical wear, changes in sensor characteristics, etc. due to long-term use can be suppressed.

[0166] Although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above. Various modifications are possible by those skilled in the art without departing from the essence of the invention as claimed in the patent claims, and such modifications should not be understood individually from the technical spirit or perspective of the present invention. Explanation of the symbols

[0167] 1000: Medical device 100: Tube unit 110: X-ray tube 120: Angle sensor 130: Lift 200: Table Unit 210: Topboard 220: Table Buckie 230: Position detection unit 300: Control unit

Claims

Claim 1 A method for correcting the angle of an X-ray tube during imaging with an X-ray imaging device comprises: a step in which, when the X-ray tube is rotated to a plurality of reference angles, a control unit obtains a sensor angle, which is a sensor output value corresponding to the rotation angle of the X-ray tube, from an angle sensor provided in the X-ray tube at each reference angle; a step in which the control unit obtains a SID, which is the distance between the X-ray tube and a table buckie; a step in which the control unit obtains a travel distance, which is the distance between a reference position of the table buckie and an alignment position of the table buckie aligned with the optical axis of the X-ray tube, at each of the plurality of reference angles; a step in which the control unit derives an actual angle using the SID and the travel distance; and a step in which the control unit generates a correction map that defines the correspondence relationship between the sensor angle and the actual angle; wherein the step of generating the correction map comprises configuring the sensor angle and the actual angle into a pair of correction nodes for each of the plurality of reference angles. A tube angle correction method comprising: a step of deriving a correction angle corresponding to an arbitrary sensor angle input based on the plurality of correction nodes; wherein the definition range of the plurality of correction nodes extends from a correction node having a minimum sensor angle to a correction node having a maximum sensor angle among the plurality of correction nodes, wherein within the definition range, the plurality of correction nodes are connected by third-order interpolation for shape preservation sections to derive a correction angle corresponding to an arbitrary sensor angle, and outside the definition range, a correction angle corresponding to an arbitrary sensor angle is derived by linear extrapolation using endpoint slopes. Claim 2 delete Claim 3 A tube angle correction method according to claim 1, wherein the step of configuring the correction node is configured by converting the sensor angle and the actual angle into tangent functions, respectively. Claim 4 A tube angle correction method according to claim 1, wherein the plurality of reference angles are set for each of the positive and negative rotation directions of the X-ray tube, and the control unit separately generates the correction map for each rotation direction. Claim 5 A tube angle correction method according to claim 4, wherein in the step of generating the correction map, the control unit generates the correction map by considering the rotational approach direction of the X-ray tube reaching an arbitrary sensor angle and deriving a correction angle for each rotational approach direction for the arbitrary sensor angle. Claim 6 A tube angle correction method according to claim 1, further comprising: a step in which the control unit obtains a correction angle corresponding to an arbitrary sensor angle based on the correction map; and a step in which the control unit calculates the travel distance of the table bucket through the correction angle and the SID. Claim 7 A tube angle correction method according to claim 6, further comprising: a step in which, after the table bucky moves according to the calculated travel distance, the control unit obtains a readjusted travel distance in which the position of the table bucky is readjusted by the user; and a step in which the control unit creates a new correction node based on the readjusted travel distance and updates the correction map. Claim 8 A medical device for X-ray imaging, comprising: a tube unit including an X-ray tube for irradiating X-rays, an angle sensor for outputting a sensor angle corresponding to the rotation angle of the X-ray tube, and a lift for adjusting the height of the X-ray tube; a table unit including a top board, a table bucket movably disposed below the top board, and a position detection unit for detecting the position of the table bucket; A medical device comprising: a control unit that receives data from the angle sensor and the position detection unit and generates a correction map; wherein the control unit derives an actual angle corresponding to a sensor angle at each reference angle based on an SID, which is the distance between the X-ray tube and the table buckie obtained while the X-ray tube is rotated to a plurality of reference angles, and a displacement distance between a reference position of the table buckie and an alignment position of the table buckie aligned with the optical axis of the X-ray tube; wherein the control unit configures the sensor angle and the actual angle into a pair of correction nodes, derives a correction angle corresponding to an arbitrary sensor angle by third-order interpolation for each shape preservation section within the defined range of the plurality of correction nodes, and derives a correction angle corresponding to an arbitrary sensor angle by linear extrapolation using an endpoint slope outside the defined range, thereby generating the correction map.

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