CT image scattering correction method and system, intelligent terminal and storage medium

Abstract

The invention discloses a CT image scattering correction method and system, an intelligent terminal and a storage medium, and relates to the technical field of radiation imaging, and the method comprises the steps: obtaining first photon intensity determined based on empty field scanning; performing CT scanning on the test die body to be subjected to scattering correction to obtain second photon intensity containing scattering photons after penetrating through the test die body; determining a scattering projection value according to the first photon intensity and the second photon intensity; determining projection deviation according to the second photon intensity and a pre-constructed nonlinear scattering correction model; determining a corrected projection value according to the scattering projection value and the projection deviation; and performing image reconstruction according to the correction projection value to obtain a target correction CT image corresponding to the test die body. Therefore, CT image scattering correction can be realized on the premise of ensuring the image quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation imaging, and particularly relates to a CT image scatter correction method and system, an intelligent terminal and a storage medium. BACKGROUND

[0002] At present, the application of computed tomography (CT) is more and more extensive. Scatter correction is a hot and difficult problem of CT imaging. In the CT data acquisition process, the detector used is a planar detector, which is inevitably affected by scattering, resulting in cup-shaped artifacts or strip or band-shaped artifacts between high-attenuation materials in the acquired image, reducing the image contrast, making the CT value inaccurate, and seriously affecting the image quality.

[0003] In the prior art, the scatter correction is usually based on a hardware improvement method. The hardware method removes the scatter artifacts by preventing scattered photons from reaching the detector, including collimator correction, anti-scattering grid correction, filter correction, air gap correction and the like. However, the hardware method usually increases the proportion of original X-rays in the scanning process, reduces the signal-to-noise ratio of the image, and affects the image quality. Therefore, the prior art is not conducive to realizing the CT image scatter correction under the premise of ensuring the image quality.

[0004] Therefore, the related technology needs to be improved and developed. SUMMARY

[0005] The main purpose of the present application is to provide a CT image scatter correction method, system, intelligent terminal and storage medium, which aims to solve the technical problem that the scatter correction based on the hardware improvement method in the related art is not conducive to realizing the CT image scatter correction under the premise of ensuring the image quality.

[0006] To achieve the above purpose, the first aspect of the present application provides a CT image scatter correction method, wherein the CT image scatter correction method comprises:

[0007] obtaining a first photon intensity determined based on an empty field scan;

[0008] performing CT scanning on a test phantom to be scattered corrected to obtain a second photon intensity containing scattered photons after passing through the test phantom;

[0009] determining a scatter projection value according to the first photon intensity and the second photon intensity;

[0010] determining a projection deviation according to the second photon intensity and a pre-constructed nonlinear scatter correction model;

[0011] determining a corrected projection value according to the scatter projection value and the projection deviation;

[0012] According to the corrected projection value, image reconstruction is performed to obtain a target corrected CT image corresponding to the test phantom.

[0013] Optionally, the pre-constructed nonlinear scatter correction model is determined based on a preset projection deviation calculation formula and a set of calibration coefficients.

[0014] The set of calibration coefficients includes a plurality of groups of calibration coefficients corresponding to a plurality of scanning angles.

[0015] Optionally, the projection deviation calculation formula is used to calculate the projection deviation according to the photon intensity of the scattered photons and the calibration coefficients.

[0016] Optionally, the projection deviation calculation formula is as follows:

[0017]

[0018] Where Δp j is the projection deviation, N represents the total order of expansion, n represents the current order of expansion, B nj represents the calibration coefficient corresponding to the nth order of expansion at the jth scanning angle, and I tj represents the photon intensity of the scattered photons at the jth scanning angle.

[0019] Optionally, the CT scanning of the test phantom to be scattered corrected to obtain the second photon intensity after passing through the test phantom includes:

[0020] Full-angle CT scanning of the test phantom to be scattered corrected is performed to obtain the second photon intensity after passing through the test phantom at a target angle.

[0021] Optionally, the determination of the projection deviation according to the second photon intensity and the pre-constructed nonlinear scatter correction model includes:

[0022] A set of target calibration coefficients corresponding to the target angle in the nonlinear scatter correction model is obtained.

[0023] The projection deviation is calculated according to the second photon intensity and the target calibration coefficient through the projection deviation calculation formula.

[0024] Optionally, the image reconstruction according to the corrected projection value to obtain the target corrected CT image corresponding to the test phantom includes:

[0025] The corrected projection value is input into an image reconstruction device.

[0026] The image reconstruction device is used for image reconstruction based on a preset image reconstruction algorithm to obtain a target corrected CT image of the test phantom after correction of the scattering artifacts.

[0027] The image reconstruction algorithm is a filtered back-projection algorithm or an iterative reconstruction algorithm.

[0028] The second aspect of the present application provides a CT image scattering correction system, wherein the CT image scattering correction system comprises:

[0029] A first data acquisition module is configured to acquire first photon intensity determined based on the empty field scanning.

[0030] A second data acquisition module is configured to perform CT scanning on a test phantom to be corrected for scattering to acquire second photon intensity containing scattered photons after passing through the test phantom.

[0031] A scattering projection value calculation module is configured to determine a scattering projection value based on the first photon intensity and the second photon intensity.

[0032] A projection deviation determination module is configured to determine a projection deviation based on the second photon intensity and a pre-constructed nonlinear scattering correction model.

[0033] A deviation correction module is configured to determine a corrected projection value based on the scattering projection value and the projection deviation.

[0034] An image reconstruction module is configured to perform image reconstruction based on the corrected projection value to obtain a target corrected CT image of the test phantom.

[0035] The third aspect of the present application provides an intelligent terminal, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the computer program is executed by the processor to implement the steps of any one of the CT image scattering correction methods.

[0036] The fourth aspect of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of any one of the CT image scattering correction methods.

[0037] As can be seen from the above, in this application, the first photon intensity determined based on the empty field scan is obtained; a CT scan is performed on the test phantom to be scattered to obtain the second photon intensity containing scattered photons after passing through the test phantom; a scattering projection value is determined based on the first photon intensity and the second photon intensity; a projection deviation is determined based on the second photon intensity and a pre-constructed nonlinear scattering correction model; a corrected projection value is determined based on the scattering projection value and the projection deviation; and image reconstruction is performed based on the corrected projection value to obtain the target corrected CT image corresponding to the test phantom.

[0038] Compared with existing technologies, the CT image scattering correction method provided in this application only requires obtaining the first photon intensity determined based on the empty field scan and the second photon intensity containing scattered photons obtained after passing through the test phantom by the CT scan. Then, it is combined with a pre-constructed nonlinear scattering correction model to perform calculations to achieve scattering correction, obtain the corrected projection value, and reconstruct the image based on the corrected projection value. In this way, no hardware improvements are required, and scattering correction is achieved without affecting the image signal-to-noise ratio, which is beneficial for achieving CT image scattering correction while ensuring image quality. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic flowchart of a CT image scattering correction method provided in an embodiment of this application;

[0041] Figure 2 This is a schematic diagram of the statistical distribution of scattered photon intensity at different angles provided in an embodiment of this application;

[0042] Figure 3 This is a schematic flowchart of a CT image scattering correction method provided in an embodiment of this application;

[0043] Figure 4 This is a schematic diagram of a CT image provided in an embodiment of this application;

[0044] Figure 5 This is a cross-sectional view of a scattering artifact correction method provided in an embodiment of this application;

[0045] Figure 6 This is a schematic diagram of the constituent modules of a CT image scattering correction system provided in an embodiment of this application;

[0046] Figure 7 This is a block diagram illustrating the internal structure of a smart terminal provided in an embodiment of this application. Detailed Implementation

[0047] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0048] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0049] It should also be understood that the terminology used in this application specification is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this application specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0050] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0051] As used in this specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to classification." Similarly, the phrases "if determined" or "if classified to [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once classified to [the described condition or event]," or "in response to classification to [the described condition or event]."

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0053] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0054] Currently, CT imaging technology is being used more and more widely, and scattering correction during the CT imaging process is receiving increasing attention. However, the distribution of scattered photons is complex and diverse, making the mathematical characterization of scattering models difficult.

[0055] In existing technologies, scattering correction is typically performed based on hardware improvements. Hardware methods remove scattering artifacts by preventing scattered photons from reaching the detector, including collimator correction, backscattering grating correction, filter plate correction, and air gap correction.

[0056] In one application scenario, scattering correction can also be performed using software methods. Software methods estimate the scattered signal from the projected scattering data, then subtract the estimated scattering value from the projected data to generate scattering-corrected projected data. These methods include convolution methods, Monte Carlo simulation correction methods, Boltzmann transport equation scattering estimation methods, scattering correction plate methods, and deep learning methods.

[0057] Hardware-based methods typically increase the proportion of raw X-rays during scanning, reducing the image signal-to-noise ratio and impacting image quality. Software-based Monte Carlo methods are time-consuming, so they are often combined with other methods, such as parameter reduction and GPU acceleration, to improve the efficiency of scattering estimation. The accuracy of the model built by convolution-based scattering correction methods directly determines the scattering estimation effect, making it impossible to accurately estimate scattering for objects with complex structures. Deep learning-based scattering correction methods offer high correction stability, and the manifestation of scattering artifacts in different tested objects is quantifiable; however, the actual scan data lacks corresponding ideal data completely unaffected by scattering artifacts.

[0058] To address at least one of the aforementioned technical problems, the present application proposes the following approach: obtaining a first photon intensity determined based on a spatial scanning process; performing a CT scan on the test phantom to be scattered to obtain a second photon intensity containing scattered photons after passing through the test phantom; determining a scattering projection value based on the first and second photon intensities; determining a projection deviation based on the second photon intensity and a pre-constructed nonlinear scattering correction model; determining a corrected projection value based on the scattering projection value and the projection deviation; and reconstructing an image based on the corrected projection value to obtain a target-corrected CT image corresponding to the test phantom.

[0059] Compared with existing technologies, the CT image scattering correction method provided in this application only requires obtaining the first photon intensity determined based on the empty field scan and the second photon intensity containing scattered photons obtained after passing through the test phantom by the CT scan. Then, it is combined with a pre-constructed nonlinear scattering correction model to perform calculations to achieve scattering correction, obtain the corrected projection value, and reconstruct the image based on the corrected projection value. In this way, no hardware improvements are required, and scattering correction is achieved without affecting the image signal-to-noise ratio, which is beneficial for achieving CT image scattering correction while ensuring image quality.

[0060] like Figure 1 As shown in the embodiments of this application, a CT image scattering correction method is provided. Specifically, the method includes the following steps:

[0061] Step S100: Obtain the first photon intensity determined based on the empty field scan;

[0062] Step S200: Perform a CT scan on the test phantom to be scattered to obtain the intensity of the second photon containing scattered photons after passing through the test phantom.

[0063] Step S300: Determine the scattering projection value based on the first photon intensity and the second photon intensity.

[0064] Step S400: Determine the projection deviation based on the second photon intensity and the pre-built nonlinear scattering correction model.

[0065] Step S500: Determine the corrected projection value based on the above-mentioned scattering projection value and the above-mentioned projection deviation;

[0066] Step S600: Reconstruct the image based on the above-mentioned corrected projection values ​​to obtain the target corrected CT image corresponding to the above-mentioned test phantom.

[0067] The first photon intensity mentioned above is the photon intensity obtained under empty-field scanning. It should be noted that the specific scenario for obtaining the first photon intensity and the specific settings of the scanning equipment are the same as those for constructing the nonlinear scattering correction model, in order to obtain better scattering correction results.

[0068] The aforementioned test phantom is the scanning object used during CT scans. Its specific configuration and adjustment can be tailored to actual needs and are not limited here. The pre-built nonlinear scattering correction model is a pre-built model used to characterize the relationship between the intensity of scattered photons and the projection deviation.

[0069] Compared with existing technologies, the CT image scattering correction method provided in this application only requires obtaining the first photon intensity determined based on the empty field scan and the second photon intensity containing scattered photons obtained after passing through the test phantom by the CT scan. Then, it is combined with a pre-constructed nonlinear scattering correction model to perform calculations to achieve scattering correction, obtain the corrected projection value, and reconstruct the image based on the corrected projection value. In this way, no hardware improvements are required, and scattering correction is achieved without affecting the image signal-to-noise ratio, which is beneficial for achieving CT image scattering correction while ensuring image quality.

[0070] Specifically, the aforementioned pre-constructed nonlinear scattering correction model is determined based on a preset projection deviation calculation formula and calibration coefficient set;

[0071] The aforementioned calibration coefficient set includes multiple sets of calibration coefficients that correspond one-to-one with multiple scanning angles. These calibration coefficients are calibrated during model building. During scattering correction using the model, only the corresponding pre-calibrated coefficients need to be obtained, which improves data processing efficiency.

[0072] Specifically, the above projection deviation calculation formula is used to calculate and determine the projection deviation based on the photon intensity containing scattered photons and the calibration coefficient.

[0073] In this embodiment of the application, the above-mentioned projection deviation calculation formula is as follows:

[0074]

[0075] Where, Δp j The projection bias is N, where N represents the total order of the expansion, n represents the current order of the expansion, and B represents the projection bias. nj I represents the calibration coefficient corresponding to the nth order expansion at the j-th scanning angle. tj This represents the photon intensity containing scattered photons at the j-th scanning angle.

[0076] It should be noted that the specific value of the total order of the expansion can be set and adjusted according to actual needs. In this embodiment, it is preferably 3, but this is not a specific limitation. In formula (1), I tj n Representing I tj The nth power.

[0077] Specifically, the above-mentioned test phantom to be scattered undergoes a CT scan to obtain the intensity of the second photon after passing through the test phantom, including:

[0078] The test phantom to be scattered was subjected to full-angle CT scanning to obtain the intensity of the second photon after passing through the test phantom at the target angle.

[0079] Furthermore, based on the aforementioned second photon intensity and the pre-constructed nonlinear scattering correction model, the projection bias is determined, including:

[0080] Obtain a set of target calibration coefficients corresponding to the target angle in the above nonlinear scattering correction model;

[0081] The projection deviation is calculated using the projection deviation calculation formula based on the second photon intensity and the target calibration coefficient.

[0082] In one application scenario, the above-mentioned image reconstruction based on the above-mentioned corrected projection values ​​to obtain the target corrected CT image corresponding to the above-mentioned test phantom includes:

[0083] Input the above corrected projection values ​​into the image reconstruction device;

[0084] Using the aforementioned image reconstruction device, image reconstruction is performed based on a preset image reconstruction algorithm to obtain the target corrected CT image corresponding to the aforementioned test phantom after scattering artifact correction.

[0085] The image reconstruction algorithms mentioned above are either filtered back-projection algorithms or iterative reconstruction algorithms.

[0086] In this embodiment, the reconstruction device is a computer. In actual applications, other devices with image reconstruction capabilities can also be used, and no specific limitation is made here. It should be noted that in this embodiment, the filtered back projection (FBP) algorithm or iterative reconstruction algorithm is used for image reconstruction, but this is not intended as a specific limitation.

[0087] This application further elaborates on the aforementioned CT image scattering correction method based on a specific application scenario. Specifically, the statistical distribution of scattered photons depends on the type of scattered photon; different types of scattered photons exhibit different distribution patterns. By exploring the prior rules governing the statistical distribution of different types of scattered photons, corresponding scattered photon models are established for each type. Using the scattered photon estimation model, a nonlinear scattering correction model is established to achieve simple and effective scattering correction of CT data. This application proposes a simple and efficient scattering correction technique, establishes a nonlinear scattered photon estimation theory, constructs a scattering correction model, achieves scattering artifact correction, and improves image contrast and image quality.

[0088] In a specific application scenario, a corresponding nonlinear scattering correction model is pre-constructed. Specifically, in X-ray CT, the total intensity of scattered photons detected after X-rays pass through an object (i.e., the total intensity of scattered photons, including all signals received by the detector) is I. t Overall, it represents the initial photon intensity I after the object has decayed. pThe total intensity of scattered photons (i.e., the intensity of scattered photons, which only includes the signal contributed by scattering and does not include the initial photon) I S The sum is:

[0089] I t =I p +I S =I0∫S(E)e -μ(E)L dE+I S (2);

[0090] Where I0 is the initial photon intensity when the X-ray does not pass through the object, S(E) is the normalized effective spectrum of the multicolor CT system, and μ(E) and L represent the linear attenuation coefficient of the object and its path length, respectively.

[0091] Therefore, the total projection p including scattering t It can be represented as:

[0092]

[0093] Where ln represents the natural logarithm to the base e, and SPR = I S / I p , which represents the ratio of the total intensity of the scattered photons to the intensity of the initial photons after attenuation.

[0094] The projection deviation Δp caused by scattering can be calculated from the unscattered projection p and the total projection p including scattering. t The difference is expressed as:

[0095]

[0096] Using Taylor expansion, the linearized mapping of the projection bias Δp is approximated as:

[0097]

[0098] Where W represents the number of Taylor expansions.

[0099] Substituting the SPR, the projection deviation based on the total intensity of scattered photons and the initial photon intensity is:

[0100]

[0101] To achieve scattering correction in CT data, it is necessary to estimate the scattered photons. This application explores the statistical distribution of different types of scattered photon intensities and designs a scattered photon estimation model. Scattered photons are mainly composed of Compton scattering, Rayleigh scattering, and multiple scattering. By simulating the intensity distribution of scattered photons using the Monte Carlo method, we found that the scattered photon distribution has the following characteristics:

[0102] 1) The intensity of scattered photons varies with the angle of the scanned object;

[0103] 2) At a scanning angle, Rayleigh scattering and multiple scattering account for a small proportion of the total scattering and can be approximated as uniformly distributed scattered photons;

[0104] 3) The intensity of Compton scattering accounts for a large proportion of the total scattering and depends on the outline shape of the front view of the scanned object, and is negatively correlated with the photoelectric effect photon intensity.

[0105] Figure 2 This is a schematic diagram illustrating the statistical distribution of scattered photon intensity at different angles, provided in an embodiment of this application. Specifically, Figure 2 The photon intensity distribution of the scanned object at 180 degrees and 90 degrees is shown, where, Figure 2 Part (a) represents the distribution of photon intensity due to the photoelectric effect, part (b) represents the distribution of photon intensity due to Compton scattering, part (c) represents the distribution of photon intensity due to Rayleigh scattering, and part (d) represents the distribution of photon intensity due to multiple scattering. Figure 2 In the image, the first row represents the photon intensity distribution of the scanned object at 180 degrees, and the second row represents the photon intensity distribution of the scanned object at 90 degrees. Based on Figure 2 The distribution statistics shown require different estimation models to be established for different types of scattered photons at different angles.

[0106] Intensity I of Rayleigh scattered photons R The proportion is relatively small and the distribution is relatively uniform, which can be approximated by the constant term C. 0R express:

[0107] I R =C 0R (7);

[0108] Similarly, the intensity I of multiple scattered photons M Its proportion is relatively small and its distribution is relatively uniform, which can be approximated by the constant term C. 0M express:

[0109] I M =C 0M (8);

[0110] Therefore, the sum of the photon intensities from Rayleigh scattering and multiple scattering can be approximated as:

[0111] I R +I M =C 0R +C 0M =C0 (9);

[0112] It should be noted that C 0R and C 0M The value of can be determined according to the actual scenario, and no specific limitation is made here.

[0113] Intensity I of Compton scattered photons C It can be approximated by the sum of powers of the reciprocals of the photon intensity from the photoelectric effect:

[0114]

[0115] Total intensity of scattered photons I S It can be represented as:

[0116]

[0117] Among them, I p It is the photon intensity of the photoelectric effect, I S It is the total intensity of scattered photons, I C It is the Compton scattered photon intensity, I M It is the intensity of multiple scattered photons, I R It represents the intensity of Rayleigh scattered photons; K is the order of the coefficient, and C... k These are the coefficients to be calibrated. Since the intensity of scattered photons varies with the scanning angle, different coefficients are needed to represent scattered photons at different angles. Therefore, the estimation model for the total intensity of scattered photons at the j-th angle can be represented by the following nonlinear function:

[0118]

[0119] Where j represents the index of the projection angle, I pj I is the photoelectric effect photon intensity at the j-th angle. Sj I is the total intensity of scattered photons at the j-th angle. Cj I is the Compton scattering photon intensity at the j-th angle. Mj I is the intensity of multiple scattered photons at the j-th angle. Rj C is the intensity of Rayleigh scattered photons at the j-th angle; kj These are the coefficients to be calibrated at the j-th angle. It should be noted that I... Sj with I S In practice, they represent the same physical meaning. The subscript j specifically refers to the corresponding physical parameter at the j-th angle. The same applies to other parameters, such as I. M with I Mj This will not be elaborated upon here.

[0120] Based on the estimated total intensity I of scattered photons at the j-th angle Sj The projection deviation based on the initial photon intensity at the j-th angle can be obtained as follows:

[0121]

[0122] The projection deviation based on the initial photon intensity in the above equation can be simplified to a nonlinear expression:

[0123]

[0124] Among them, B nj It is the coefficient to be calibrated at the j-th angle.

[0125] Due to the intensity of scattered photons I S Much smaller than I t The total photon intensity i including scattered photons t Photon intensity i approximating the photoelectric effect p The projection deviation based on the total photon intensity including scattering at the j-th angle is obtained:

[0126]

[0127] Furthermore, based on the above formula (15), the projection deviation calculation formula as shown in formula (1) is obtained, and the corresponding calibration coefficient B is determined through coefficient calibration. nj This allows for the determination of a nonlinear scattering correction model. During scattering correction, it is not necessary to calculate the value of the scattered photons; only the intensity of the total number of scattered photons collected is needed. The projection deviation is directly estimated based on the established scattering correction model, and scattering correction in the projection domain is performed. No additional information is required, enabling simple and effective scattering correction. It should be noted that the coefficients B of the nonlinear scattering correction model at each scanning angle can be obtained through experimental calibration. nj .

[0128] In a specific application scenario, the above-mentioned CT image scattering correction method can be applied to a CT image scattering correction system. Figure 3 This is a schematic flowchart of a CT image scattering correction method provided in an embodiment of this application. It should be noted that, as... Figure 3 As shown, the CT image scattering correction method specifically includes two parts: coefficient calibration and error correction, which can be implemented by the calibration module and the correction module, respectively.

[0129] Specifically, in the coefficient calibration stage, it is necessary to determine the coefficient B in formula (15). nj The coefficients B of the nonlinear scattering correction model at each scanning angle j can be obtained through calibration. nj The specific calibration process is as follows:

[0130] Step 1: Data Collection

[0131] Acquire scan data for coefficient calibration of the nonlinear scattering correction model. Set scanning conditions such as scanning voltage and current of the X-ray source and detector acquisition frame rate.

[0132] 1. Empty field scanning data: When no scanning phantom is placed, the initial photon intensity under the scanning conditions is collected using a flat panel detector and denoted as I0.

[0133] 2. Scattered Scan Data: Without using collimators or other anti-scattering devices, a flat panel detector is used to perform a full-angle CT scan of a standard phantom (such as a cylindrical water phantom or a skull phantom containing equivalent bone and soft tissue materials). The scanning angle range is typically 0° to 360°, and projection data from multiple angles are acquired using a step-by-step or continuous rotation method. The intensity of the scattered photons after passing through the object at the j-th angle is acquired and denoted as I. tj .

[0134] 3. Scatter-free scan data: Under the same scanning conditions, using a collimator (to suppress scattering) and adjusting the collimator slit to <1mm, perform a full-angle CT scan on the same phantom as described above, and obtain the photon intensity of approximately scatter-free photons at the j-th angle after passing through the object, denoted as I. pj .

[0135] Step 2: Model coefficient calibration:

[0136] The coefficients of the nonlinear scattering correction model are calibrated based on the scanning data described above. This nonlinear scattering correction model includes calibration coefficients corresponding to different scanning angles, determined by the scanning intensity at different scanning angles.

[0137] 1. Calculate the reference projection value: based on the initial photon intensity I0 and the photon intensity I of the unscattered photon at the j-th angle. pj Calculate the reference projection value

[0138] 2. Calculate the projection value including scattering: This is based on the initial photon intensity I0 and the photon intensity I of the scattered photon at the j-th angle. tj Calculate the projection value including scattering.

[0139] 3. Calculate the projection deviation: This is based on the projection value p including scattering at the j-th angle. tj Compared with the reference projection value p j Calculate the scattering projection deviation Δp j =p j -p tj ;

[0140] 4. Linear regression fitting: For each angle j, the nonlinear scattering correction model constructed according to formula (1) is derived from the scattering projection deviation Δp. j and the intensity of scattered photons I tj The coefficients B of the nonlinear scattering correction model at the j-th scanning angle are calibrated. njIn this embodiment of the application, the value of N is set to N=3, but this is not a specific limitation. Then, formula (1) can be expressed as the following formula (16):

[0141]

[0142] Furthermore, the calibrated coefficient set {B} is obtained through linear regression fitting. 0j B 1j B 2j B 3j}

[0143] Step 3: Coefficient storage:

[0144] The calibration coefficient set [B] corresponding to the 360° angle 0j B 1j B 2j B 3j Save it to a document for scattering correction.

[0145] It should be noted that the above steps can be executed separately by the data acquisition unit, coefficient calibration unit, and coefficient storage unit of the CT image scattering correction system. Furthermore, the coefficient calibration process can also be pre-executed, allowing it to be directly invoked during error correction without requiring calibration every time.

[0146] Furthermore, in the scattering error correction stage, the coefficients B of the calibrated nonlinear scattering correction model can be used as a basis. nj Scattering correction is then performed on the data from other scanned phantoms. The specific correction process is as follows:

[0147] Step 1: Data Acquisition (Physical Equipment: CT Scanning Equipment):

[0148] The same scanning conditions as the calibration phantom are set, including the scanning voltage and current of the X-ray source, the detector acquisition frame rate, etc., and a full-angle CT scan is performed on the test phantom (such as a skull phantom). The outer contour size of the test phantom is included in the contour size of the calibration phantom, and the initial placement position of the test phantom is approximately the same as that of the calibration phantom.

[0149] 1. Field scanning data: Use the field scanning data I0 (i.e., the first photon intensity) collected during the calibration phase. It should be noted that the first photon intensity can be the photon intensity collected during the coefficient calibration phase, or it can be obtained by re-collecting the field scanning data under the same environment. No specific limitation is made here.

[0150] 2. Acquiring Scattered Scan Data: Without using a collimator, a flat panel detector is used to perform a full-angle CT scan of the test phantom to be corrected for scattering. The intensity of the scattered photons after passing through the object at the j-th angle (i.e., the second photon intensity) is collected and denoted as I. tj .

[0151] Step 2: Correct the scattering projection:

[0152] 1. Calculate the projection value including scattering: This is based on the initial photon intensity I0 and the photon intensity I of the scattered photon at the j-th angle. tj Calculate the projection value including scattering (i.e., the scattering projection value).

[0153] 2. Application of a nonlinear scattering correction model: Based on the photon intensity I of the scattered photon at the j-th angle. pj The nonlinear scattering correction model of formula (1) and the calibrated coefficient set {B 0j B 1j B 2j B 3j} Calculate the projection deviation caused by scattering

[0154] 3. Generate corrected projection value: The corrected projection value p is obtained by summing the estimated scattering projection deviation with the collected scattering projection value. j =p tj +Δp j .

[0155] Step 3: Image Reconstruction (Physical Equipment: Reconstruction Computer):

[0156] 1. Input data: Projected datasets after all angle corrections {p j};

[0157] 2. Processing procedure: Image reconstruction is performed using filtered back projection (FBP) or iterative reconstruction algorithms;

[0158] 3. Output data: CT images after scattering artifact correction.

[0159] It should be noted that the above steps can be performed by the data acquisition unit, scattering correction unit, and image reconstruction unit of the CT image scattering correction system, respectively.

[0160] To further verify the effectiveness of the method in this application, the embodiments of this application also conduct further verification based on the skull phantom data. Figure 4 This is a schematic diagram of a CT image provided in an embodiment of this application, wherein, Figure 4 The image on the left is the uncorrected image. Figure 4The image on the right side of the middle section is a corrected version based on the scheme described in this application. Figure 5 This is a cross-sectional view of a scattering artifact correction method provided in an embodiment of this application. Based on Figure 4 It can be seen that the contrast of the corrected image is significantly improved. Based on Figure 5 As can be seen, the CT data processed by the solution of this application is corrected, which shows that the solution of this application can effectively remove scattering artifacts in the reconstructed image and improve image quality.

[0161] Thus, in this embodiment, a nonlinear scattered photon estimation model is constructed for different types of scattered photons. Based on the scattered photon estimation model, a new projection deviation formula is derived from the projection transformation, establishing a novel nonlinear scattering correction model. This model only requires the total number of scattered photons to achieve scattering correction, without needing additional information, thus making the calculation simpler and more efficient. Furthermore, the solution in this application directly estimates the projection deviation without estimating the scattered photons, making it even more efficient.

[0162] It should be noted that in the embodiments of this application, the Rayleigh scattering photon intensity and the multiple scattering photon intensity are represented by constant terms, while the Compton scattering photon intensity is represented by a power of the reciprocal of the photoelectric effect photon intensity, which is a simple approximation. In one application scenario, this scattered photon estimation can be designed with a different scattered photon estimation model than that of this application to achieve scattering correction.

[0163] It should be further explained that when calibrating the coefficients, the scanning angles can be grouped (for example, divided into groups of 30 degrees each), thereby reducing the amount of coefficient calibration and reducing the accuracy error caused by the difference between the calibration phantom and the test phantom.

[0164] like Figure 6 As shown, corresponding to the above-described CT image scattering correction method, this application embodiment also provides a CT image scattering correction system, which includes:

[0165] The first data acquisition module 610 is used to acquire the first photon intensity determined based on the space field scan.

[0166] The second data acquisition module 620 is used to perform a CT scan on the test phantom to be scattered and corrected, and to acquire the intensity of the second photon containing scattered photons after passing through the test phantom.

[0167] The scattering projection value calculation module 630 is used to determine the scattering projection value based on the first photon intensity and the second photon intensity.

[0168] The projection deviation determination module 640 is used to determine the projection deviation based on the second photon intensity and the pre-built nonlinear scattering correction model.

[0169] The deviation correction module 650 is used to determine the corrected projection value based on the above-mentioned scattering projection value and the above-mentioned projection deviation;

[0170] The image reconstruction module 660 is used to reconstruct the image based on the above-mentioned corrected projection values ​​to obtain the target corrected CT image corresponding to the above-mentioned test phantom.

[0171] Thus, it is only necessary to obtain the first photon intensity determined based on the empty field scan and the second photon intensity containing scattered photons obtained from the CT scan after passing through the test phantom. Then, the scattering correction is calculated by combining it with a pre-built nonlinear scattering correction model to obtain the corrected projection value and perform image reconstruction based on the corrected projection value. No hardware improvements are required, and scattering correction is achieved without affecting the image signal-to-noise ratio, which is beneficial for achieving CT image scattering correction while ensuring image quality.

[0172] It should be noted that the specific structure and implementation of the above-mentioned CT image scattering correction system and its various modules or units can be referred to the corresponding descriptions in the above method embodiments, and will not be repeated here.

[0173] It should be noted that the division of the various modules of the above-mentioned CT image scattering correction system is not unique and is not intended as a specific limitation.

[0174] Based on the above embodiments, this application also provides a smart terminal, the principle block diagram of which can be as follows: Figure 7 As shown. The aforementioned intelligent terminal includes a processor, memory, network interface, and display screen connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements the steps of any of the aforementioned CT image scattering correction methods. The display screen of the intelligent terminal can be a liquid crystal display (LCD) or an e-ink display.

[0175] Those skilled in the art will understand that Figure 7 The block diagram shown is only a partial structural diagram related to the solution of this application and does not constitute a limitation on the smart terminal on which the solution of this application is applied. The specific smart terminal may include more or fewer components than shown in the figure, or combine some components, or have different component arrangements.

[0176] In one embodiment, a smart terminal is provided, the smart terminal including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of any of the CT image scattering correction methods provided in the embodiments of this application.

[0177] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of any CT image scattering correction method provided in this application.

[0178] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0179] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the above device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above device can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0180] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0181] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0182] In the embodiments provided in this application, it should be understood that the disclosed systems / terminal devices and methods can be implemented in other ways. For example, the system / terminal device embodiments described above are merely illustrative. For instance, the division of modules or units described above is merely a logical functional division, and in actual implementation, it can be divided in other ways. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0183] If the integrated modules / units described above are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, and software distribution media, etc. It should be noted that the content included in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction.

[0184] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions are not in essence a departure from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for scattering correction in CT images, characterized in that, The method includes: Obtain the first photon intensity determined based on the spatial field scan; A CT scan was performed on the test phantom to be scattered to obtain the intensity of the second photon containing scattered photons after passing through the test phantom; The scattering projection value is determined based on the first photon intensity and the second photon intensity; The projection bias is determined based on the intensity of the second photon and the pre-constructed nonlinear scattering correction model. The corrected projection value is determined based on the scattered projection value and the projection deviation; Image reconstruction is performed based on the corrected projection values ​​to obtain the target corrected CT image corresponding to the test phantom.

2. The CT image scattering correction method according to claim 1, characterized in that, The pre-constructed nonlinear scattering correction model is determined based on a preset projection deviation calculation formula and calibration coefficient set; The calibration coefficient set includes multiple sets of calibration coefficients that correspond one-to-one with multiple scanning angles.

3. The CT image scattering correction method according to claim 2, characterized in that, The projection deviation calculation formula is used to calculate and determine the projection deviation based on the photon intensity containing scattered photons and the calibration coefficient.

4. The CT image scattering correction method according to claim 3, characterized in that, The formula for calculating the projection deviation is: Where, Δp j The projection bias is N, where N represents the total order of the expansion, n represents the current order of the expansion, and B represents the projection bias. nj I represents the calibration coefficient corresponding to the nth order expansion at the j-th scanning angle. tj This represents the photon intensity containing scattered photons at the j-th scanning angle.

5. The CT image scattering correction method according to claim 2, characterized in that, The step of performing a CT scan on the test phantom to be scattered and corrected, and obtaining the intensity of the second photon after passing through the test phantom, includes: The test phantom to be scattered is subjected to a full-angle CT scan to obtain the second photon intensity after passing through the test phantom at the target angle.

6. The CT image scattering correction method according to claim 5, characterized in that, The step of determining the projection bias based on the second photon intensity and a pre-constructed nonlinear scattering correction model includes: Obtain a set of target calibration coefficients corresponding to the target angle in the nonlinear scattering correction model; The projection deviation is calculated using the projection deviation calculation formula based on the second photon intensity and the target calibration coefficient.

7. The CT image scattering correction method according to any one of claims 1 to 6, characterized in that, The step of reconstructing the image based on the corrected projection value to obtain the target corrected CT image corresponding to the test phantom includes: The corrected projection value is input into the image reconstruction device; The image reconstruction device is used to reconstruct the image based on a preset image reconstruction algorithm to obtain the target corrected CT image of the test phantom after scattering artifact correction. The image reconstruction algorithm is either a filtered back-projection algorithm or an iterative reconstruction algorithm.

8. A CT image scattering correction system, characterized in that, The system includes: The first data acquisition module is used to acquire the first photon intensity determined based on the empty field scan. The second data acquisition module is used to perform a CT scan on the test phantom to be scattered and corrected, and to acquire the intensity of the second photon containing scattered photons after passing through the test phantom. A scattering projection value calculation module is used to determine the scattering projection value based on the first photon intensity and the second photon intensity; The projection deviation determination module is used to determine the projection deviation based on the second photon intensity and a pre-built nonlinear scattering correction model. A deviation correction module is used to determine a corrected projection value based on the scattered projection value and the projection deviation; The image reconstruction module is used to reconstruct the image based on the corrected projection value to obtain the target corrected CT image corresponding to the test phantom.

9. A smart terminal, characterized in that, The smart terminal includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the CT image scattering correction method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the CT image scattering correction method as described in any one of claims 1 to 7.

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