Method for correcting ct ray intensity, ct device, and storage medium

Abstract

The application discloses a CT ray light intensity correction method, a CT device and a storage medium. The CT ray light intensity correction method comprises the following steps: acquiring reference light intensity data of an X-ray source in a state that reference channels on both sides of a detector are not blocked; calculating a light intensity reference value based on the reference light intensity data; acquiring working light intensity data of the X-ray source under different rotation angles of the CT in an actual working state of the CT; determining first abnormal data according to the working light intensity data being lower than the light intensity reference value and an absolute value of a deviation between the working light intensity data and the light intensity reference value being greater than a first threshold value; determining a first abnormal data angle interval through a rotation angle corresponding to the first abnormal data; and regarding abnormal data corresponding to lower limit and upper limit values of the first abnormal data angle interval as end point data.

Description

Technical Field

[0001] This application relates to the field of CT technology, and more specifically, to a CT beam intensity correction method, a CT device, and a storage medium. Background Technology

[0002] Computerized Tomography (CT) imaging relies on X-ray intensity to calculate the attenuation distribution of an object and reconstruct the image. Reference channels are located on both sides of the detector to monitor the incident X-ray intensity in real time and compensate for signal deviations caused by fluctuations in the X-ray tube current and voltage. During normal scanning, the object is located at the center of rotation, and the reference channels on both sides are unobstructed. However, if the object is too large or severely eccentric, both reference channels will be blocked simultaneously, resulting in the loss of real-time intensity reference signals.

[0003] To address the signal loss problem, current solutions typically employ normalized estimation using air scan data combined with scan current, or directly determine the obstruction area using a single threshold. However, these solutions have significant drawbacks in practical applications: 1. Inaccurate identification of abnormal interval boundaries: Single threshold judgment is difficult to adapt to complex light intensity changes, often leading to misjudgment of the start and end points of the occlusion interval, either mistakenly including normal data into the abnormal interval or missing the real occlusion data.

[0004] 2. Poor anti-interference ability: There is a deviation between the measured result of the X-ray tube current and the actual result. When correcting the data of the abnormal interval based on the current, the correction result will have a significant deviation from the normal data of the adjacent interval, causing the data in that section to jump. Summary of the Invention

[0005] This application aims to solve the problem of real-time signal loss caused by the obstruction of the bilateral reference channels, which easily leads to inaccurate identification of the boundary of the abnormal data angle interval. It provides a CT beam intensity correction method that does not rely on current measurement, thus avoiding the error introduced by inaccurate current measurement, reducing imaging artifacts, and improving image quality under complex scanning conditions.

[0006] To achieve the above objectives, a first aspect of this application proposes a CT beam intensity correction method, comprising: The reference light intensity data of the X-ray source is acquired when the reference channels on both sides of the detector are unobstructed. Calculate the reference light intensity value based on the reference light intensity data; Under the actual working conditions of CT, obtain the working light intensity data of the X-ray source at different rotation angles of CT; If the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is judged as the first abnormal data. The first abnormal data angle range is determined by the rotation angle corresponding to the first abnormal data. The abnormal data corresponding to the lower limit and upper limit of the first abnormal data angle range are the endpoint data. Based on the endpoint data, M consecutive working light intensity data adjacent to the endpoint data and arranged sequentially are selected outside the first abnormal data angle interval. If the absolute value of the deviation of N consecutive working light intensity data from the light intensity reference value is less than the second threshold among the M working light intensity data outside the abnormal angle interval, the first abnormal data and N consecutive working light intensity data are determined as the second abnormal data, where N≥2, M>N, and M and N are both integers. The actual abnormal data angle range is determined by combining the rotation angle corresponding to the second abnormal data.

[0007] This application pre-acquires reference light intensity data and calculates a reference light intensity value when the reference channels on both sides of the detector are unobstructed. During actual scanning, in cases where the measured object is too large or severely eccentric, causing simultaneous obstruction of both reference channels and loss of real-time light intensity reference signal, this application first uses a first threshold to initially screen the working light intensity data, obtaining a first abnormal data angle range to avoid missing abnormal data. Then, using a second threshold combined with a judgment method based on N consecutive data, data outside the first abnormal data angle range is rigorously screened to filter out the abnormal data missed in the first judgment, obtaining the actual abnormal data angle range and ensuring the accuracy of the abnormal data angle range boundary. Through the above correction method, this application can more accurately define the range of abnormal data caused by obstruction even without a real-time reference signal, providing a reliable basis for the subsequent calculation of the actual light intensity of the abnormal data angle range, helping to reduce image artifacts and improve the imaging quality of the CT system under complex scanning conditions.

[0008] In some embodiments, the CT beam intensity correction method further includes: If, among M consecutive working light intensity data on any side outside the first abnormal data angle interval, the absolute value of the deviation between N consecutive working light intensity data and the light intensity reference value is less than a second threshold, then the comparison between the deviation of the corresponding working light intensity data on the corresponding side and the light intensity reference value and the second threshold is stopped.

[0009] In some embodiments, if the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is determined to be first abnormal data. The angle range of the first abnormal data is determined by the rotation angle corresponding to the first abnormal data, including: The working light intensity data of CT scans for at least one week are divided into multiple data segments according to the order of the scans. The standard deviation of the working light intensity data in each data segment is calculated, and the preset multiple of the minimum standard deviation is used as the first threshold. If the light intensity value of the working light intensity data in each data segment is lower than the light intensity reference value and the deviation exceeds the first threshold, the working light intensity data is determined to be the first abnormal data, and the angle range of the first abnormal data is determined by the rotation angle corresponding to the first abnormal data.

[0010] In some embodiments, the standard deviation of the working light intensity data within each data segment is calculated, and a preset multiple of the minimum standard deviation is used as a first threshold, including: use The formula calculates the standard deviation of each data segment, where, Standard deviation, These are different working light intensity data within the same data segment. The number of data segments, It is an integer greater than or equal to 2; Use at least three times the minimum standard deviation as the first threshold.

[0011] In some embodiments, calculating a reference value for light intensity in an unobstructed state based on reference light intensity data includes: Obtain reference light intensity data under unobstructed conditions and the corresponding first current value ; Obtain the second current value under actual working conditions ; use The formula calculates the reference value of light intensity, where, This is the reference value for light intensity.

[0012] In some embodiments, different working light intensity data correspond to a CT rotation angle, and the working light intensity data and the corresponding rotation angle form a data pair. The CT light intensity correction method further includes: Extract data pairs located outside the abnormal data angle range, fit the working light intensity data outside the abnormal data angle range using a preset function, solve for the most probable value of the unknown coefficient of the preset function, and substitute the rotation angle corresponding to the abnormal data angle range into the preset function to determine the theoretical working light intensity data of the abnormal fluctuation range. CT images are generated using theoretical working light intensity data.

[0013] In some embodiments, the preset function is a polynomial function of order less than 4. The preset function is used to fit the working light intensity data outside the angular range of the abnormal data, and the most probable values ​​of the unknown coefficients of the preset function are determined, including: The most probable value of the unknown coefficient is obtained by fitting the working light intensity data located outside the angular range of the abnormal data using methods such as the least squares method.

[0014] In some embodiments, generating CT images using theoretical working light intensity data includes: Using formula The attenuation of the theoretical working light intensity data is calculated, the attenuation beam is used to construct the projection data, and a CT image is generated based on the attenuation. in, This is the attenuation amount. The initial light intensity, This represents the intensity of transmitted light that decreases after passing through the target object.

[0015] A second aspect of this application provides a CT device, comprising: The acquisition module is used to acquire reference light intensity data of the X-ray source when the reference channels on both sides of the detector are unobstructed, and to acquire working light intensity data of the X-ray source at different rotation angles in the actual working state of CT. The processing module, which communicates with the acquisition module, is configured as follows: Calculate the reference light intensity value under unobstructed conditions based on reference light intensity data; If the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is judged as the first abnormal data, so as to obtain the angle range of the first abnormal data. Based on the endpoint data, M working light intensity data that are adjacent to the endpoint data and arranged sequentially are selected outside the first abnormal data angle interval. If the absolute value of the deviation of N consecutive working light intensity data from the light intensity reference value is less than the second threshold among the M working light intensity data outside the abnormal angle interval, the first abnormal data and the N consecutive working light intensity data are determined as the second abnormal data, where N≥2, M>N, and M and N are both integers. The actual abnormal data angle range is determined by combining the rotation angle corresponding to the second abnormal data.

[0016] In a third aspect, this application provides a storage medium, which is a computer-readable storage medium storing a computer program that, when executed by a processor, implements the CT beam intensity correction method described in the first aspect. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 A flowchart provided in this application; Figure 2 This is a schematic diagram of a scanning phantom when the X-ray source in a CT scanner rotates. Figure 3A The image generated from the unprocessed light intensity data after a CT scanner irradiates a cylindrical water phantom. Figure 3B The image is generated by processing the light intensity data of a cylindrical water phantom irradiated by a CT device according to this application. Detailed Implementation

[0018] 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 some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linked," and "socketing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] One embodiment of this application provides a CT beam intensity correction method, applied to a CT device. The CT device mainly includes a gantry, an X-ray source, a detector, and a processing module.

[0024] The X-ray source is mounted on a rack and configured to emit a cone-shaped or fan-shaped beam of light around the scanning area. Detectors are arranged in an arc or ring shape to receive the rays passing through the scanning area. Reference channels are located at both edges of the detectors; these channels, when unobstructed, should directly receive the initial light intensity emitted by the X-ray source to monitor the stability of the radiation output.

[0025] Figure 2 The diagram shows an X-ray source and detector rotating together to irradiate a phantom (the object under test). When rotated to certain angles, positions 103 and 104 of the dual-channel system are blocked by the phantom. If the intensity of the blocked light is not processed, such as... Figure 3A As shown, artifacts will appear in the middle of the image.

[0026] The processing module (such as a computer or embedded processor) is communicatively connected to the detector and X-ray source to receive the light intensity signal collected by the detector and execute the CT X-ray light intensity correction method of this application. During the scanning process, the object under test (such as a medical patient or industrial workpiece) is placed at the center of rotation. As the gantry rotates, the X-ray source and detector rotate synchronously around the object under test to obtain light intensity data at different rotation angles.

[0027] The following is combined with Figure 1 The following description will be based on a CT beam intensity correction method according to some embodiments of this application.

[0028] This application provides a CT beam intensity correction method, including: S100. Acquire reference light intensity data of the X-ray source under unobstructed conditions on both sides of the detector's reference channels; S200, Calculate the reference light intensity value based on the reference light intensity data; S300. Under the actual working state of CT, acquire the working light intensity data of the X-ray source of CT at different rotation angles; S400. If the working light intensity data is lower than the light intensity reference value and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is determined to be the first abnormal data. The first abnormal data angle range is determined by the rotation angle corresponding to the first abnormal data. The abnormal data corresponding to the lower limit and upper limit of the first abnormal data angle range are the endpoint data. S500. Based on the endpoint data, select M working light intensity data that are adjacent to the endpoint data and arranged sequentially outside the first abnormal data angle interval. If the absolute value of the deviation of N consecutive working light intensity data from the light intensity reference value is less than the second threshold among the M working light intensity data outside the abnormal angle interval, determine the first abnormal data and the N consecutive working light intensity data as the second abnormal data, where N≥2, M>N, and M and N are both integers. S600. Determine the actual abnormal data angle range by combining the rotation angle corresponding to the second abnormal data.

[0029] In step S300, during the formal scanning operation of the CT equipment, the detector and the X-ray source rotate synchronously around the scanning center. At each rotation sampling angle, the real-time X-ray light intensity value output by the current X-ray source and received through the reference channel is collected synchronously, and a complete set of light intensity sampling data corresponding to all angles is collected.

[0030] During a CT scan, the X-ray tube (X-ray source) and detector rotate in a circle. The equipment acquires angular positions at fixed intervals (such as 0°, 1°, 2°...360°, a complete scan is 360°), and each acquisition moment corresponds to a unique rotation angle.

[0031] Working light intensity data refers to the ray intensity detected in real time by both reference channels during formal scanning and placement of the object under test.

[0032] When the object being measured is eccentric or too large, the reference channels on both sides will be blocked by the object at certain angles, and the working light intensity collected at that angle will be significantly lower than the normal level.

[0033] With the CT rotation angle as the horizontal axis and the working light intensity value collected at the corresponding angle as the vertical axis, all sampling points can form a light intensity variation curve; each sampling point simultaneously has two pieces of information: the rotation angle and the working light intensity data corresponding to that angle.

[0034] N can be an integer greater than or equal to 2, for example, it can be any value between 2 and 10.

[0035] The first abnormal data angle interval is composed of multiple sampling point data components. Each sampling point's first abnormal data corresponds to a unique rotation angle. The minimum and maximum rotation angles among all the first abnormal data are taken as the lower limit and upper limit values, respectively. The interval formed by the lower limit and upper limit values ​​is the first abnormal data angle interval. The first abnormal data angle interval is the angle range obtained from the coarse screening.

[0036] The abnormal data angle interval in this application is an angle interval with the CT rotation angle as the boundary. After filtering out all actual abnormal data, the rotation angle corresponding to each actual abnormal data is extracted. The minimum angle is taken as the starting boundary of the interval and the maximum angle is taken as the ending boundary of the interval. The continuous angle range enclosed by the starting boundary and the ending boundary is the abnormal data angle interval. This angle interval represents the complete angle range in which the bilateral reference channels are synchronously blocked by the object during the scanning process. Each angle in the interval corresponds to working light intensity data with abnormal attenuation.

[0037] Traverse all sampling points throughout the entire cycle and select all sampling points that simultaneously meet the S400 judgment condition; form a continuous sampling point set by continuously distributing sampling points along the time sequence / rotation angle. Take the minimum value among all working light intensity data in this sampling point set as the lower limit value of light intensity in the first abnormal data angle interval; take the maximum value among all working light intensity data in the suspicious sampling point set as the upper limit value of light intensity in the first abnormal data angle interval.

[0038] This application pre-acquires reference light intensity data and calculates a reference light intensity value when the reference channels on both sides of the detector are unobstructed. During actual scanning, in cases where the measured object is too large or severely eccentric, causing simultaneous obstruction of both reference channels and loss of real-time light intensity reference signal, this application first uses a first threshold to initially screen the working light intensity data, obtaining a first abnormal data angle range to avoid missing abnormal data. Then, using a second threshold combined with a judgment method based on N consecutive data, data outside the first abnormal data angle range is rigorously screened to filter out the abnormal data missed in the first judgment, obtaining the actual abnormal data angle range and ensuring the accuracy of the abnormal data angle range boundary. Through the above correction method, this application can more accurately define the range of abnormal data caused by obstruction even without a real-time reference signal, providing a reliable basis for the subsequent calculation of the actual light intensity of the abnormal data angle range, helping to reduce image artifacts and improve the imaging quality of the CT system under complex scanning conditions.

[0039] In some embodiments, the CT beam intensity correction method further includes: S510. If, among M consecutive working light intensity data on any side outside the first abnormal data angle interval, there are N consecutive working light intensity data whose absolute value of the deviation from the light intensity reference value is less than a second threshold, then stop comparing the deviation of the corresponding working light intensity data on the corresponding side from the light intensity reference value with the second threshold.

[0040] M consecutive working light intensity data: Starting from the working light intensity data corresponding to the upper and lower limits of the first abnormal data angle interval, M working light intensity data are extracted sequentially and arranged continuously on the same side outside the first abnormal data angle interval (the working light intensity data are usually arranged in the order of CT rotation angle).

[0041] The first abnormal data can be selected from either side outside the angle range, which can be the side with an angle less than the lower limit of the range or the side with a rotation angle greater than the upper limit of the range. The working light intensity data on both sides can be judged independently using the S500 step.

[0042] Since S400 is a coarse screening for abnormal data, some abnormal data is missed. The first abnormal data angle range obtained after S400 is not the actual abnormal data angle range. Therefore, S500 uses the two endpoints of the first abnormal data angle range as a reference to continuously select M working light intensity data points outward for secondary screening to obtain the second abnormal data. The second abnormal data is the actual abnormal data after correcting the first abnormal data. Based on the rotation angle corresponding to the actual abnormal data, the maximum and minimum values ​​of the corresponding rotation angle in the actual abnormal data are retrieved as the upper and lower limits of the actual abnormal data angle range. These serve as the boundaries for subsequent theoretical calculations of the actual abnormal data.

[0043] Once N consecutive working light intensity data meet the S500 judgment condition, the boundary of the actual abnormal data interval is determined. The judgment of the working light intensity data of S500 on the same side of the first abnormal data angle interval is immediately interrupted, thereby avoiding invalid judgment of a large number of irrelevant data outside the first abnormal data angle interval. This reduces the workload of secondary screening of abnormal data outside the first abnormal data interval and effectively improves the overall correction efficiency.

[0044] In some embodiments, step S400 includes: S410. Divide the working light intensity data of CT scans for at least one week into multiple data segments according to the order of scanning, calculate the standard deviation of the working light intensity data in each data segment, and use the preset multiple of the minimum standard deviation as the first threshold. S420. If the light intensity value of the working light intensity data in each data segment is lower than the light intensity reference value and the deviation exceeds the first threshold, the working light intensity data is determined to be the first abnormal data, and the angle range of the first abnormal data is determined by the rotation angle corresponding to the first abnormal data.

[0045] During a CT scan, the X-ray source and detector rotate around the center of rotation, completing one full rotation to cover all scanning angles, and collecting working light intensity data corresponding to each of the rotation angles; a continuous light intensity sampling sequence of no less than one full rotation is selected as the working light intensity data.

[0046] Based on the order of scanning acquisition time / rotation angle, all sampling points are divided into multiple continuous and non-overlapping data segments. For example, a whole circle has 1000 sampling points, which are divided into 4 segments with 250 sampling points in each segment.

[0047] Only a few angles have bilateral channel obstruction during the entire scanning process, and the vast majority of segments have unobstructed normal light intensity. After segmentation, unobstructed segments can be separated, and the fluctuation of the unobstructed segments can be used to represent the normal noise level of the equipment. The overall fluctuation statistics will not be raised by abnormal data caused by obstruction.

[0048] The preset multiplier can be, but is not limited to, 3 to 5 times, to form a coarse screen of actual light intensity data to prevent abnormal data from being missed.

[0049] In this embodiment, by extracting at least one week's worth of scan data and calculating the standard deviation in segments, the minimum standard deviation representing the inherent small fluctuations of the equipment is selected, and then multiplied by a preset factor to obtain a first threshold. The first threshold is automatically generated based on the actual light intensity fluctuations of this scan, eliminating the need for manual pre-entry of a fixed threshold. This approach is adaptable to CT equipment with different tube voltages, tube currents, and aging levels, solving the problem of poor universality of fixed thresholds. Within the complete scan cycle, only local intervals have bilateral channel obstruction, resulting in large light intensity fluctuations and a higher standard deviation in the obstructed sections. By dividing the entire scan data into multiple data segments and taking the minimum standard deviation, this data segment corresponds to an effective segment without obstruction and only exhibits normal small fluctuations in the X-ray tube. The first threshold is calculated based on this segment, preventing the large light intensity drops caused by obstruction from raising the fluctuation benchmark, ensuring that the first threshold only reflects the normal noise level of the equipment itself. Simultaneously, S420 performs preliminary screening of abnormal data to prevent the omission of abnormal light intensity data and reduces the computational workload of subsequent corrections.

[0050] In some embodiments, step S410 involves calculating the standard deviation of the working light intensity data within each data segment and using a preset multiple of the minimum standard deviation as a first threshold, including: use The formula calculates the standard deviation of each data segment, where, Standard deviation These are different working light intensity data within the same data segment. The number of data segments, It is an integer greater than or equal to 2; Use at least three times the minimum standard deviation as the first threshold.

[0051] The standard deviation formula is used to quantify the light intensity fluctuation of each segment and the number of data segments is limited to no less than 2 to ensure the validity of the calculation. The minimum standard deviation is selected to represent the normal fluctuation of the CT equipment under unobstructed conditions. Then, at least 3 times is taken as the first threshold to reserve a reasonable error tolerance range. This can prevent too much valid data from being misjudged as abnormal data, provide reliability for the screening of abnormal light intensity data, reduce the workload of subsequent correction of the first abnormal data, and improve efficiency.

[0052] In some embodiments, the first threshold can also be a percentage of the light intensity reference value. Alternatively, the scanning period can be divided into multiple data segments, and the maximum and minimum values ​​of the working light intensity data of each data segment can be extracted. The single-segment light intensity range can be calculated to characterize the signal fluctuation amplitude of this segment. The minimum value among all segment ranges can be selected and multiplied by a preset coefficient to generate the first threshold.

[0053] In some embodiments, step S200 includes: Obtain reference light intensity data under unobstructed conditions and the corresponding first current value ; Obtain the second current value under actual working conditions ; use The formula calculates the reference value of light intensity, where, This is the reference value for light intensity.

[0054] This embodiment first acquires the reference light intensity and corresponding tube current under unobstructed calibration conditions, then reads the actual scanning working tube current, and calculates the light intensity reference value through a linear proportional formula. Then, it completes current compensation by utilizing the physical characteristic that X-ray light intensity is proportional to tube current. This can eliminate the light intensity baseline deviation caused by the scanning milliampere value, eliminate the need to repeatedly perform air scanning calibration, adapt to scanning conditions with arbitrary tube current parameters, avoid distortion of the first threshold judgment due to different working tube currents (the working tube currents of different CT devices may be different), and improve the universality and accuracy of occlusion recognition.

[0055] In some embodiments, with the reference channels on both sides of the detector unobstructed, reference light intensity data of the X-ray source is acquired, reference light intensity data corresponding to all rotation angles are collected, the arithmetic mean of all sampling points is taken, and this average value is directly used as the light intensity reference value for this imaging.

[0056] In some embodiments, a low-order polynomial is used to fit the dynamically changing reference light intensity sequence to obtain a continuous and smooth reference light intensity fitting curve. Normalize the curve point by point to obtain a continuous curve. The standard reference light intensity at that location can be obtained by interpolation at any rotation angle.

[0057] In some embodiments, different working light intensity data correspond to a CT rotation angle, and the working light intensity data and the corresponding rotation angle form a data pair. The CT light intensity correction method further includes: S600. Extract data pairs located outside the abnormal data angle range, substitute them into the preset function to solve the unknown coefficients of the preset function, and substitute the rotation angle corresponding to the abnormal data angle range into the preset function to determine the theoretical working light intensity data of the abnormal fluctuation range. S700 generates CT images using theoretical working light intensity data.

[0058] By creating a one-to-one correspondence between working light intensity data and CT rotation angle, effective data pairs outside the abnormal data angle range that are not affected by obstruction are selected to solve the preset function coefficients. A light intensity mapping function that fits the entire angle is fitted using the real light intensity data outside the abnormal data angle range. The theoretical working light intensity data in the unobstructed state within the abnormal fluctuation range is then calculated using this function. This replaces the original light intensity signal that is distorted by workpiece obstruction, eliminating the light intensity attenuation deviation caused by obstruction. This ensures that the light intensity data used for CT reconstruction is complete, continuous, and matches the actual X-ray output level of the equipment, effectively avoiding artifacts in the reconstructed image caused by obstruction, thereby improving the CT image quality and demonstrating strong versatility.

[0059] In some embodiments, the preset function is a polynomial function of less than order 4. The process includes extracting data pairs located outside the abnormal data angle range, fitting the working light intensity data outside the abnormal data angle range using the preset function, and solving for the most probable values ​​of the unknown coefficients of the preset function, including: The most probable value of the unknown coefficient is obtained by fitting the working light intensity data located outside the angular range of the abnormal data using methods such as the least squares method.

[0060] Taking a second-order polynomial function as an example, , The unknown coefficients of the preset function are defined, with the CT rotation angle as the independent variable x and the working light intensity data as the dependent variable y. All valid working light intensity data outside the abnormal angle range are extracted to obtain multiple sets of valid sample data pairs (x...). i , The algorithm calculates the difference between the fitted light intensity value for each angle and the actual collected light intensity value. All differences are squared and summed to obtain the total sum of squared errors. Using the sum of squared errors avoids the problem of positive and negative errors canceling each other out, while amplifying the influence of outlier fitting points with larger deviations, thus ensuring overall fitting accuracy. The core of the least squares method is to continuously adjust the unknown coefficients of the polynomial through mathematical iteration, continuously reducing the total sum of squared errors until the total error reaches its global minimum. The set of coefficient values ​​at this point represents the most probable values ​​of all unknown coefficients. Once the sum of squared errors converges to its minimum and the coefficient values ​​stabilize, the complete optimal polynomial fitting function can be determined.

[0061] By using effective working light intensity data outside the actual abnormal angle range as samples and employing the second-order polynomial least squares method for fitting, this application can construct a light intensity benchmark curve that highly matches the CT rotation angle after eliminating the interference of abnormal data. Since the error sum of squares objective function assigns higher weights to larger deviations, it can effectively suppress the influence of local noise, making the fitted curve closer to the true light intensity change trend. Simultaneously, by using continuous and stable effective data outside the abnormal range to determine the polynomial unknown coefficients, the contamination of the fitting results by the abnormal angle range is avoided. Thus, while ensuring fitting accuracy, reliable correction and completion of missing or distorted light intensity data within the abnormal angle range are achieved, significantly improving the overall stability and accuracy of CT beam light intensity correction.

[0062] In other examples, the unknown coefficients can be solved by solving a system of equations. For example, the preset function could be a third-order polynomial function, such as... , Indicates the rotation angle. Indicates working light intensity. These are the unknown coefficients. Three data pairs can be retrieved from the range of abnormal data to establish three systems of equations for solving. A third-order polynomial function is obtained. Based on the determined abnormal data angle interval, the theoretical working light intensity corresponding to the abnormal angle interval can be obtained. Finally, based on the theoretical working light intensity data and the actual working light intensity data outside the abnormal data angle interval, a CT image is constructed.

[0063] In some embodiments, generating CT images using theoretical working light intensity data includes: Using formula The attenuation of the theoretical working light intensity data is calculated, the attenuation beam is used to construct the projection data, and a CT image is generated based on the attenuation. in, This is the attenuation amount. The initial light intensity, This represents the intensity of transmitted light that decreases after passing through the target object.

[0064] The theoretical light intensity data corresponding to all rotation angles and the effective working light intensity data outside the abnormal data range are substituted into the attenuation rate calculation formula one by one to obtain the attenuation amount A under each scanning angle. The attenuation amounts of all angles are combined in an orderly manner to form a complete projection data array without obstruction or distortion.

[0065] Using attenuation projection data from all angles as input, standard CT reconstruction algorithms (such as filtered back projection, iterative reconstruction, etc.) are used to perform tomographic calculations. Based on the attenuation distribution of rays at different angles, the linear attenuation coefficient distribution of materials at each location within the scanned section is inferred, and finally, a tomographic CT image is output.

[0066] By converting the light intensity ratio into linear attenuation projection data through the attenuation formula, which conforms to the physical law of X-ray attenuation, the interference of light intensity distortion caused by workpiece obstruction on the projection value is eliminated. This allows the projection attenuation at each angle to truly reflect the absorption characteristics of the object being measured. Based on the corrected theoretical light intensity data, attenuation beam calculation and tomographic reconstruction are performed, which can significantly reduce obstruction artifacts and grayscale distortion, and improve the quality of CT images.

[0067] Figure 3B The image is a CT image generated after the light intensity data of both channels have been processed by the CT light intensity correction method of this application. It can be seen in the image that... Figure 3A In comparison, the artifacts in the middle disappear, significantly improving the quality of CT images.

[0068] The following description uses a CT device according to some embodiments of this application as an example.

[0069] This application provides a CT device in which the aforementioned CT beam intensity correction method is used. The CT device includes an acquisition module and a processing module. The acquisition module acquires reference beam intensity data of the X-ray source in an unobstructed state between the reference channels on both sides of the detector, and acquires working beam intensity data of the X-ray source at different rotation angles during actual CT operation. The processing module is communicatively connected to the acquisition module and is configured as follows: Calculate the reference light intensity value under unobstructed conditions based on reference light intensity data; If the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than the first threshold, it is judged as the first abnormal data, so as to obtain the angle range of the first abnormal data. Based on the endpoint data, select M working light intensity data that are adjacent to the endpoint data and arranged sequentially outside the first abnormal data angle interval. If the absolute value of the deviation of N consecutive working light intensity data from the light intensity reference value is less than the second threshold among the M working light intensity data outside the abnormal angle interval, the first abnormal data and N consecutive working light intensity data are determined as the second abnormal data, where N≥2, M>N, and M and N are both integers. The actual abnormal data angle range is determined by combining the rotation angle corresponding to the second abnormal data.

[0070] The acquisition module is the data acquisition unit of a CT scanner. It can be a hardware combination including detector signal acquisition circuitry, analog-to-digital converter chip, and data transmission bus, or a software acquisition unit integrating acquisition drivers.

[0071] The processing module is the computing unit of the CT equipment (such as an industrial control board, embedded processor, etc.).

[0072] The following description uses a storage medium from some embodiments of this application as an example.

[0073] This application provides a storage medium, which is a computer-readable storage medium, storing a computer program. When the computer program is executed by a processor, it implements the CT beam intensity correction method of the first aspect.

[0074] This application also provides a computer-readable storage medium, including but not limited to physical media capable of storing computer program code such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks. The computer-readable storage medium stores a computer program containing complete program instructions for executing the aforementioned CT beam intensity correction method. When the processor of the CT device reads and runs the computer program, it can sequentially execute the CT beam intensity correction method.

[0075] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0076] Obviously, those skilled in the art should understand that the various units or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device, or fabricating them separately as individual integrated circuit modules, or fabricating multiple modules or steps into a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0077] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for CT beam intensity correction, characterized in that, include: The reference light intensity data of the X-ray source is acquired when the reference channels on both sides of the detector are unobstructed. Calculate the reference light intensity value based on the reference light intensity data; Under the actual working condition of CT, the working light intensity data of the X-ray source under different rotation angles of CT are obtained; If the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is judged as the first abnormal data. The first abnormal data angle range is determined by the rotation angle corresponding to the first abnormal data. The abnormal data corresponding to the lower limit and upper limit of the first abnormal data angle range are the endpoint data. Based on the endpoint data, M working light intensity data that are adjacent to and continuously arranged outside the first abnormal data angle interval are selected sequentially. If the absolute value of the deviation of N consecutive working light intensity data from the light intensity reference value is less than the second threshold among the M working light intensity data outside the abnormal angle interval, the first abnormal data and the N consecutive working light intensity data are determined as the second abnormal data, where N≥2, M>N, and M and N are both integers. The actual abnormal data angle range is determined by combining the rotation angle corresponding to the second abnormal data.

2. The CT beam intensity correction method according to claim 1, characterized in that, The CT beam intensity correction method also includes: If, among M consecutive working light intensity data on any side outside the first abnormal data angle interval, the absolute value of the deviation between N consecutive working light intensity data and the light intensity reference value is less than a second threshold, then the comparison between the deviation of the corresponding working light intensity data on the corresponding side and the light intensity reference value and the second threshold is stopped.

3. The CT beam intensity correction method according to claim 1, characterized in that, If the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is determined to be first abnormal data. The angle range of the first abnormal data is determined by the rotation angle corresponding to the first abnormal data, including: The working light intensity data from at least one week of CT scans are divided into multiple data segments according to the order of the scans. The standard deviation of the working light intensity data in each data segment is calculated, and the preset multiple of the minimum standard deviation is used as the first threshold. If the light intensity value of the working light intensity data in each of the data segments is lower than the light intensity reference value and the deviation exceeds the first threshold, the working light intensity data is determined to be the first abnormal data, and the angle range of the first abnormal data is determined by the rotation angle corresponding to the first abnormal data.

4. The CT beam intensity correction method according to claim 3, characterized in that, Calculate the standard deviation of the working light intensity data within each data segment, and use a preset multiple of the minimum standard deviation as a first threshold, including: use The formula calculates the standard deviation of each data segment, where, Standard deviation, These are different working light intensity data within the same data segment. The number of data segments, It is an integer greater than or equal to 2; Use at least three times the minimum standard deviation as the first threshold.

5. The CT beam intensity correction method according to any one of claims 1-4, characterized in that, The calculation of the reference light intensity value under unobstructed conditions based on the reference light intensity data includes: Obtain reference light intensity data under unobstructed conditions and the corresponding first current value ; Obtain the second current value under actual working conditions ; use The formula calculates the light intensity reference value, where, The light intensity reference value is denoted as .

6. The CT beam intensity correction method according to any one of claims 1-4, characterized in that, Different working light intensity data correspond to a CT rotation angle, and the working light intensity data and the corresponding rotation angle form a data pair. The CT light intensity correction method further includes: Extract the data pairs located outside the abnormal data angle range, fit the working light intensity data outside the abnormal data angle range using a preset function, solve for the most probable value of the unknown coefficient of the preset function, and substitute the rotation angle corresponding to the abnormal data angle range into the preset function to determine the theoretical working light intensity data of the abnormal fluctuation range. CT images are generated using the theoretical working light intensity data.

7. The CT beam intensity correction method according to claim 6, characterized in that, The preset function is a polynomial function of order less than 4. The process of fitting the working light intensity data outside the angular range of the abnormal data using the preset function and solving for the most probable values ​​of the unknown coefficients of the preset function includes: The most probable value of the unknown coefficient is obtained by fitting the working light intensity data located outside the angular range of the abnormal data using methods such as the least squares method.

8. The CT beam intensity correction method according to claim 6, characterized in that, The process of generating CT images using the theoretical working light intensity data includes: Using formula The attenuation of the theoretical working light intensity data is calculated, the attenuation beam forms projection data, and the CT image is generated based on the attenuation. in, This is the attenuation amount. The initial light intensity, The intensity of transmitted light is attenuated after passing through the target object.

9. A CT scanner, characterized in that, include: The acquisition module is used to acquire reference light intensity data of the X-ray source when the reference channels on both sides of the detector are unobstructed, and to acquire working light intensity data of the X-ray source at different rotation angles in the actual working state of CT. The processing module is communicatively connected to the acquisition module, and the processing module is configured to: Calculate the reference light intensity value under unobstructed conditions based on the reference light intensity data; If the working light intensity data is lower than the light intensity reference value, and the absolute value of the deviation between the working light intensity data and the light intensity reference value is greater than a first threshold, it is judged as the first abnormal data, so as to obtain the angle range of the first abnormal data. Based on the endpoint data, M working light intensity data that are adjacent to the endpoint data and arranged sequentially are selected outside the first abnormal data angle interval. If the absolute value of the deviation of N consecutive working light intensity data from the light intensity reference value is less than the second threshold among the M working light intensity data outside the abnormal angle interval, the first abnormal data and the N consecutive working light intensity data are determined as the second abnormal data, where N≥2, M>N, and M and N are both integers. The actual abnormal data angle range is determined by combining the rotation angle corresponding to the second abnormal data.

10. A storage medium, said storage medium being a computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the CT beam intensity correction method as described in any one of claims 1-9.

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