Annular artifact correction method and electronic equipment

Abstract

The invention provides a ring artifact correction method and electronic equipment, and relates to the technical field of medical treatment. According to the specific implementation scheme, the electronic equipment obtains a projection image, the projection image comprises a shadow area, and one shadow point in the shadow area corresponds to one annular artifact; the electronic equipment determines the position information of the annular artifact corresponding to the shadow point based on the position information of the shadow point in the shadow area; and the electronic equipment corrects the ring artifacts based on the position information of the ring artifacts corresponding to the shadow points. Thus, the position information of the ring artifact corresponding to the shadow point is determined, and correction of the ring artifact is performed in a targeted manner in combination with the position information of the ring artifact, so that the ring artifact can be removed more accurately, and the correction accuracy of the ring artifact is improved.

Description

Technical Field

[0001] This disclosure relates to the field of medical technology, and in particular to a method and electronic device for correcting ring artifacts. Background Technology

[0002] When using cone beam computed tomography (CBCT) for imaging, a beam stop array (BSA, or X-ray blocking array) is usually used for scattering correction to avoid poor image quality caused by scattering of X-ray signals emitted by the CBCT light source.

[0003] However, because the BSA is fixed in position and blocks the X-ray signal, the CBCT detector cannot receive the X-ray signal at the blocked position of the BSA. This results in a shadow area in the CBCT projection image, which in turn causes ring artifacts in the reconstructed image when the projection image is reconstructed. Summary of the Invention

[0004] This disclosure provides a method and electronic device for correcting ring artifacts, which can be used to specifically remove rings from ring artifacts, thereby improving the accuracy of ring artifact correction.

[0005] According to one aspect of this disclosure, a method for correcting ring artifacts is provided, the method comprising: Acquire a projected image, which includes a shadow region. A shadow point in the shadow region corresponds to a ring artifact. Based on the location information of the shadow points in the shadow region, determine the location information of the annular artifacts corresponding to the shadow points; The annular artifacts are corrected based on the location information of the annular artifacts corresponding to the shadow points.

[0006] In some possible implementations, the location information of the annular artifact is used to indicate the position of the stripes of the annular artifact in a polar coordinate image, which is obtained by converting a slice image of the annular artifact in the reconstructed image. Based on the location information of the shadow points in the shadow region, the location information of the ring artifacts corresponding to the shadow points is determined, including: Based on the location information of the shadow points, the ring radius and slice position of the ring artifact corresponding to the shadow points in the reconstructed image are determined; Perform polar coordinate transformation on the slice images corresponding to the slice positions in the reconstructed image to obtain polar coordinate images; The position of the ring artifact in the polar coordinate image is determined based on the ring radius, thus obtaining the position information of the ring artifact.

[0007] In some possible implementations, based on the location information of the shadow points, the ring radius and slice position of the ring artifact corresponding to the shadow points in the reconstructed image are determined, including: Based on the first position coordinates of the shadow point, the ring radius of the ring artifact corresponding to the shadow point in the reconstructed image is determined. The first position coordinates are the coordinates in the horizontal direction of the projected image. Based on the second position coordinates of the shadow point, the slice position of the ring artifact corresponding to the shadow point in the reconstructed image is determined. The second position coordinates are the coordinates in the vertical direction of the projected image.

[0008] In some possible implementations, the method further includes: Based on the first offset, the first position coordinates of the shadow point are corrected. The first offset is the offset in the horizontal direction of the projected image. Based on the second offset, the second position coordinates of the shadow point are corrected. The second offset is the offset in the vertical direction of the projected image.

[0009] In some possible implementations, the annular artifacts are corrected based on the positional information of the annular artifacts corresponding to the shadow points, including: In a polar coordinate image, the stripe positions indicated by the position information of the ring artifacts are filtered to obtain a filtered polar coordinate image. Based on the polar coordinate images before and after filtering, the ring artifacts in the slice image are corrected.

[0010] In some possible implementations, the ring artifacts in the slice image are corrected based on the polar coordinate image before and after filtering, including: The difference image between the polar coordinate image before filtering and the polar coordinate image after filtering is determined to obtain the first ring image, which is the image of the ring artifact in the polar coordinate system. The first ring image is transformed into Cartesian coordinates to obtain the second ring image, which is the image of the ring artifact in the Cartesian coordinate system. Determine the difference image between the slice image and the second ring image.

[0011] In some possible implementations, the positional information of the annular artifact is used to indicate the position of the stripes in the sinusoidal image, which is obtained by converting the projected image; Based on the location information of the shadow points in the shadow region, the location information of the ring artifacts corresponding to the shadow points is determined, including: Based on the location information of the shadow points and multiple preset projection angles, the projected image is transformed to obtain a sinusoidal image; The position of the ring artifact in the sine image is determined based on the position information of the shadow points, thus obtaining the position information of the ring artifact.

[0012] In some possible implementations, the annular artifacts are corrected based on the positional information of the annular artifacts corresponding to the shadow points, including: In a sinusoidal image, the stripe positions indicated by the position information of the ring artifacts are filtered to obtain a filtered sinusoidal image. Based on the sinusoidal image before and after filtering, the ring artifacts in the projection image are corrected.

[0013] In some possible implementations, the ring artifacts in the projected image are corrected based on the sinusoidal image before and after filtering, including: The difference image between the sinusoidal image before and after filtering is determined to obtain the third ring image, which is the sinusoidal image of the ring artifact. The third ring image is transformed to obtain the fourth ring image, which is the projection image of the ring artifact; Determine the difference image between the projected image and the fourth ring image.

[0014] In some possible implementations, the method further includes: Acquire a first shadow image, which is used to indicate the shadowed area in the projected image; Based on the first shadow image, the shadow area in the projected image is determined.

[0015] In some possible implementations, acquiring the first shadow image includes: Obtain the empty field image, which is the projected image when there is no object being scanned; Image segmentation is performed on the empty field image to obtain the shadowed and non-shadowed regions in the empty field image; Based on the shadow and non-shadow regions in the empty field image, the empty field image is binarized to obtain the first shadow image.

[0016] In some possible implementations, the shadow area is a target shadow area, which is the area within the shadow area excluding the penumbra; the method further includes: Obtain a second shadow image, which is used to indicate the areas other than the penumbra region in the shadow region of the projected image; Based on the second shadow image, the target shadow region in the projected image is determined.

[0017] In some possible implementations, acquiring the second shadow image includes: Obtain the penumbra information of the projected image. The penumbra information is used to indicate the penumbra region in the shadow area of ​​the projected image. The first shadow image is processed based on the penumbra information to obtain the second shadow image. The first shadow image is used to indicate the shadow area in the projected image.

[0018] In some possible implementations, obtaining penumbra information of the projected image includes: From the multiple pixels included in the shadow area of ​​the projected image, select the target pixel, which is the pixel whose ray intensity is greater than the ray intensity threshold; Obtain the position information of the target pixel as the penumbra information of the projected image.

[0019] In some possible implementations, the target pixel is a pixel carrying a first marker, and the method further includes: Add a first marker to pixels whose ray intensity is greater than the ray intensity threshold.

[0020] In some possible implementations, the method further includes: Add a second marker to pixels whose ray intensity is less than or equal to the ray intensity threshold.

[0021] In some possible implementations, the first shadow image is processed based on penumbra information to obtain a second shadow image, including: Based on penumbra information, pixel value transformation is performed on pixels belonging to the penumbra region in the shadow area of ​​the first shadow image to obtain the second shadow image.

[0022] According to another aspect of this disclosure, an electronic device is provided, comprising: At least one processor; and The memory is communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the ring artifact correction method provided in this disclosure.

[0023] According to another aspect of this disclosure, a non-transitory computer-readable storage medium is provided storing computer instructions for causing the electronic device to perform the ring artifact correction method provided in this disclosure.

[0024] According to another aspect of this disclosure, a computer program product is provided, including a computer program that, when executed by a processor, implements the ring artifact correction method provided in this disclosure.

[0025] The technical solution provided in this disclosure determines the location information of the ring artifacts corresponding to the shadow points, and then performs targeted correction of the ring artifacts based on the location information of the ring artifacts, which can more accurately remove the ring artifacts and thus improve the accuracy of the ring artifact correction.

[0026] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0027] The accompanying drawings are provided to better understand this solution and do not constitute a limitation of this disclosure. Wherein: Figure 1 This is a schematic diagram of the implementation environment of a method for correcting ring artifacts according to an embodiment of this disclosure; Figure 2 This is a cross-sectional schematic diagram of an image scanning device shown in an embodiment of this disclosure; Figure 3 This is a schematic diagram of a BSA shown in an embodiment of this disclosure; Figure 4 This is a schematic flowchart illustrating a method for correcting ring artifacts according to an embodiment of this disclosure; Figure 5 This is a schematic diagram of an empty field image shown in an embodiment of this disclosure; Figure 6 This is a schematic diagram illustrating a first shadow image according to an embodiment of the present disclosure; Figure 7 This is a schematic diagram of a second shadow image shown in an embodiment of this disclosure; Figure 8 This is a schematic diagram of a penumbra region shown in an embodiment of this disclosure; Figure 9 This is a schematic flowchart illustrating another method for correcting annular artifacts according to an embodiment of this disclosure; Figure 10 This is a diagram illustrating the positional relationship between annular artifacts and detector shadow points, as shown in an embodiment of this disclosure. Figure 11 This is a schematic diagram of a polar coordinate image shown in an embodiment of this disclosure; Figure 12 This is a schematic flowchart illustrating another method for correcting annular artifacts according to an embodiment of this disclosure; Figure 13 This is a schematic diagram of a sine wave according to an embodiment of the present disclosure; Figure 14 This is a block diagram of an electronic device for a method of correcting ring artifacts according to an embodiment of this disclosure. Detailed Implementation

[0028] The exemplary embodiments of this disclosure are described below with reference to the accompanying drawings, including various details of the embodiments to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this disclosure. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0029] The collection, storage, use, processing, transmission, provision, and disclosure of user personal information involved in the technical solution disclosed herein comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0030] First, the application scenarios involved in the embodiments of this disclosure are described. The ring artifact correction method provided in the embodiments of this disclosure can be applied to the field of medical technology, specifically to the scenario of medical image scanning.

[0031] In medical imaging, CBCT is used to scan a subject (such as a patient) to obtain projected images of the subject from multiple angles. Then, based on these projected images, computer graphics and image processing techniques are used to convert the original projected images into reconstructed images suitable for diagnosis. Because reconstructed images provide clearer and more detailed information about the internal structures of the human body, the accuracy of disease diagnosis can be improved.

[0032] When using CBCT scanning for imaging, because CBCT uses cone-beam X-rays as its light source, the X-ray signal may interact with the scanned object during the imaging process, resulting in scattering. This scattering of the X-ray signal can lead to poor reconstructed image quality, such as decreased contrast and inaccurate computed tomography (CT) values.

[0033] In CBCT, contrast is used to characterize the differences in X-ray signal absorption by different tissues of the scanned object. For example, bone absorbs X-ray signals strongly and therefore appears as a high-brightness area in the reconstructed image. Conversely, soft tissue absorbs X-ray signals weakly and therefore appears as a low-brightness area in the reconstructed image. However, X-ray signal scattering can reduce CBCT contrast, thus affecting the quality of the reconstructed image. The CT value in CBCT is a quantitative indicator measuring the absorption capacity of different tissues of the scanned object for X-ray signals. However, X-ray signal scattering can introduce additional scattered signals, leading to errors in CT value calculation and thus affecting the quality of the reconstructed image.

[0034] To overcome the problem of poor image quality caused by the scattering of X-ray signals emitted by the CBCT light source, a beam blocking element (BSA) is typically placed between the CBCT light source and the scanned object, or between the CBCT detector and the scanned object, to achieve scatter correction. The BSA is a plate composed of multiple high-absorption (high-attenuation) beam blocking elements (such as lead or tungsten cylinders). These beam blocking elements block X-ray signals, ensuring that the detector receives only scattered signals in the shadowed area corresponding to the beam blocking element. Understandably, due to the low-frequency characteristics of the scattered signal (i.e., low spatial frequency), this means that the scattered signal changes more slowly and is more uniformly distributed in space. Therefore, by measuring the scattered signal received by the CBCT detector and combining it with interpolation methods (such as bilinear interpolation, spline interpolation, etc.), the scattering distribution of the entire imaging area can be obtained, thus enabling scatter correction.

[0035] Thus, the BSA (Browser Aspect) can accurately measure the scattered signal, thereby removing scattering artifacts caused by CBCT. However, because the BSA is fixed in position and blocks the X-ray signal, the CBCT detector cannot receive the X-ray signal at the blocked location, resulting in shadowed areas (such as shadowed areas at fixed pixel positions) in the CBCT projection image. Even if interpolation is used to complete the X-ray information in the shadowed areas, the high-frequency characteristics of the X-ray signal (i.e., high spatial frequency) mean that the X-ray signal changes more rapidly and its distribution is more complex in space. Therefore, interpolation cannot completely recover the high-frequency structural information in the shadowed areas. Consequently, reconstruction based on the projection image can cause ring artifacts in the reconstructed image. For example, each shadow point on the detector may correspond to a ring artifact on the cross-section of the reconstructed image.

[0036] In related technologies, the common method for correcting ring artifacts is to filter the entire reconstructed image to obtain a corrected reconstructed image. However, on the one hand, filtering may mistakenly identify structural information in the reconstructed image as ring artifacts and correct them accordingly, resulting in additional ring artifacts in the corrected reconstructed image. On the other hand, filtering may reduce the high-frequency components of the reconstructed image, and the contrast of soft tissues often depends on these high-frequency components for differentiation. When the high-frequency components of the reconstructed image are excessively suppressed, the contrast of soft tissues decreases, thereby reducing the diagnostic value of the reconstructed image. Furthermore, filtering may lead to inaccurate correction of ring artifacts. For example, incomplete ring removal or overcorrection of normal tissues may result in noticeable ring artifacts still remaining in the corrected reconstructed image.

[0037] Based on this, the present disclosure provides a method for correcting annular artifacts. By determining the location information of the annular artifacts corresponding to the shadow points, and then specifically correcting the annular artifacts based on this location information, the annular artifacts can be removed more accurately, thereby improving the accuracy of annular artifact correction. Compared with related technologies, by specifically correcting annular artifacts based on their location information, it is possible to avoid mistaking structural information in the reconstructed image for annular artifacts and correcting it accordingly, thus avoiding the appearance of additional annular artifacts in the corrected reconstructed image. Furthermore, specifically correcting annular artifacts based on their location information can remove annular artifacts more accurately, avoiding a decrease in soft tissue contrast due to a reduction in high-frequency components in the reconstructed image, thereby ensuring the diagnostic value of the reconstructed image. Moreover, specifically correcting annular artifacts based on their location information can avoid incomplete annular removal or overcorrection of normal tissue, thus preventing the presence of obvious annular artifacts in the corrected reconstructed image.

[0038] Figure 1 This is a schematic diagram illustrating the implementation environment of a method for correcting annular artifacts according to an embodiment of this disclosure. See also... Figure 1 The implementation environment includes: image scanning device 101 and electronic device 102.

[0039] The imaging scanning device 101 is used to acquire images of the tumor site and surrounding normal tissue of the scanned object. In some embodiments, the imaging scanning device 101 may be a CBCT device.

[0040] In this embodiment of the present disclosure, the image scanning device 101 is used to acquire projected images of the scanned object at multiple angles and send the projected images at multiple angles to the electronic device 102 so that the electronic device 102 can perform a method for correcting ring artifacts.

[0041] Electronic device 102 is a device connected to image scanning device 101. In some embodiments, electronic device 102 may be at least one of devices such as smartphones, smartwatches, desktop computers, laptops, virtual reality terminals, augmented reality terminals, wireless terminals, and laptop computers. In other embodiments, electronic device 102 may be an independent physical server, a server cluster composed of multiple physical servers, a distributed file system, or at least one of cloud servers providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks, and big data or artificial intelligence platforms. This disclosure does not limit the specific implementation of these embodiments. The image scanning device 101 and electronic device 102 can communicate via a wired or wireless network.

[0042] In this embodiment of the disclosure, the electronic device 102 is used to acquire a projected image, which includes a shadow region. A shadow point in the shadow region corresponds to a ring artifact. Based on the position information of the shadow point in the shadow region, the position information of the ring artifact corresponding to the shadow point is determined. Based on the position information of the ring artifact corresponding to the shadow point, the ring artifact is corrected.

[0043] Figure 2 This is a cross-sectional schematic diagram of an image scanning device according to an embodiment of this disclosure. See also... Figure 2 The image scanning device includes: a frame 201, a light source 202, a support device 203, a detector 204, and a BSA 205.

[0044] The frame 201 can be a rotatable frame. The light source 202 and detector 204 are mounted opposite each other on the frame 201, and the BSA 205 is positioned below the light source 202. The light source 202 emits X-rays (imaging rays). The support device 203 supports the object being scanned, such as a support bed. The detector 204 acquires the X-rays transmitted from the light source 202 through the BSA 205 and the scanned object, as well as the scattered signals in the event of scattering.

[0045] BSA205 is used to block the transmission of X-rays. Figure 3 This is a schematic diagram of a BSA according to an embodiment of this disclosure. See also Figure 3 A BSA can include n*n beam blocking elements, such as Figure 3 The lead or tungsten points shown form an n*n array, where n is a positive integer greater than 0. Figure 3 Let's take n=9 as an example to illustrate BSA.

[0046] In some embodiments, when the object being scanned is on the support device 203, the rotation of the frame 201 can drive the light source 202, BSA 205, and detector 204 to scan around the object at multiple angles, and multiple angle projection images can be acquired on the detector 204. Here, the BSA 205 can rotate around its own central axis in its horizontal plane by a preset angle, such as 45 degrees.

[0047] It should be noted that the light source 202, BSA 205, and detector 204 can also be mounted on the gantry of a radiotherapy device. The gantry is equipped with a radiotherapy head that emits therapeutic rays for radiotherapy. Rotation of the gantry allows the light source 202, BSA 205, and detector 204 to scan the radiotherapy subject from multiple angles. Multiple projected images can be captured on the detector 204, providing image guidance for the radiotherapy subject.

[0048] The following is based on Figure 1 The implementation environment shown will be used to describe the methods provided in the embodiments of this disclosure.

[0049] Figure 4 This is a schematic flowchart illustrating a method for correcting ring artifacts according to an embodiment of this disclosure. In some embodiments, the method for correcting ring artifacts is performed by an electronic device. Figure 4 As shown, the method includes the following steps.

[0050] S401, Electronic device acquires projected image.

[0051] The projected image includes a shadowed area, and a shadow point within the shadowed area corresponds to a ring-shaped artifact. In some possible implementations, the projected image may include projected images from multiple angles acquired by the image scanning device. It is understood that the multiple angle projected images acquired by the image scanning device are projected images from multiple angles acquired for the scanned object. Exemplarily, in this embodiment, I will be referred to as I in subsequent implementations. object To refer to projected images.

[0052] The aforementioned multiple angles refer to the multiple angles (such as the rotation angle of the gantry) used by the image scanning device during scanning and imaging. The range of the multiple angles can be (0 degrees, 360 degrees). In some possible implementations, the multiple angles can be evenly distributed, such as adjacent angles being spaced by the same angle (e.g., 1 degree). Alternatively, in other possible implementations, the multiple angles can be non-uniformly distributed, such as adjacent angles being spaced by different angles. Alternatively, in other possible implementations, the multiple angles can also be specific angles selected according to specific needs, such as one or more key angles selected from (0 degrees, 360 degrees). This disclosure does not limit this aspect.

[0053] In some embodiments, the electronic device may use a first shadow image to determine shadow areas in a projected image. The corresponding process may be: the electronic device acquires the first shadow image; then, the electronic device determines the shadow areas in the projected image based on the first shadow image.

[0054] In this embodiment, the first shadow image is used to indicate the shadow area in the projected image. In this disclosure, the first shadow image may be referred to as a mask image, used to indicate the location of the shadow area in the projected image. Exemplarily, the first shadow image is used to indicate the pixel location of the shadow area in the projected image, such as pixel coordinates. In some possible implementations, the first shadow image is a binary image. A binary image is an image where the pixel value is 0 or 1, where 0 represents black and 1 represents white. Exemplarily, in this disclosure, the first shadow image will subsequently be referred to as mask1.

[0055] In some possible implementations, taking the example that a pixel with a pixel value of 1 in the first shadow image corresponds to a shadow region, the process of determining the shadow region in the projected image based on the first shadow image can be as follows: First, determine the position of a first pixel with a pixel value of 1 from the first shadow image. Then, for each angle of the projected image, determine a second pixel position corresponding to the first pixel position, and use the determined second pixel position as the position of the shadow region. Here, the first pixel position refers to the position of the shadow region in the first shadow image, and the second pixel position refers to the position of the shadow region in the projected image.

[0056] In some other possible implementations, taking the example that a pixel with a value of 0 in the first shadow image corresponds to a shadow region, the process of determining the shadow region in the projected image based on the first shadow image can be as follows: determine the position of the third pixel with a value of 0 in the first shadow image. Furthermore, for each angle of the projected image, determine the position of the fourth pixel corresponding to the third pixel position, and use the determined second pixel position as the position of the shadow region. Here, the third pixel position refers to the position of the shadow region in the first shadow image, and the fourth pixel position refers to the position of the shadow region in the projected image.

[0057] In the above embodiments, by using the first shadow image, the shadow area in the projected image at each angle can be accurately determined, thereby improving the accuracy of determining the shadow area.

[0058] The process by which an electronic device acquires the first shadow image may include the following steps one through three.

[0059] Step 1: The electronic device acquires an image of the empty field.

[0060] Here, the empty field image is the projected image when there is no object being scanned. Exemplarily, in this embodiment of the disclosure, I will be used as a reference for... air To refer to an empty field image.

[0061] In some embodiments, the image scanning device acquires an empty field image even when no object is being scanned. The image scanning device then sends the empty field image to an electronic device, which in turn receives the empty field image.

[0062] For example, an image scanning device sends an empty field image at a target angle to an electronic device. The target angle is one of a set of preset angles. The electronic device then receives the empty field image at the target angle.

[0063] For example, the image scanning device sends empty-field images from multiple angles to the electronic device. The electronic device then receives these empty-field images from multiple angles and averages them to obtain an averaged empty-field image. The averaging process involves averaging the pixel values ​​at the same location in the multiple images. Thus, by averaging the empty-field images from multiple angles, a more representative empty-field image can be obtained, laying the foundation for subsequently obtaining a highly accurate first shadow image.

[0064] Step 2: The electronic device performs image segmentation on the empty field image to obtain the shadowed and non-shadowed regions in the empty field image.

[0065] Image segmentation refers to the process of dividing an image into multiple non-overlapping regions. In this embodiment of the disclosure, image segmentation is used to distinguish shadowed regions from other regions (i.e., non-shadowed regions) in an empty field image. It is understood that shadowed regions refer to regions formed by the obstruction of the beam blocking element of the BSA, while non-shadowed regions refer to unobstructed regions.

[0066] For example, Figure 5 This is a schematic diagram of an empty field image shown in an embodiment of this disclosure. See also... Figure 5 The shaded area can include Figure 5 Multiple shaded points in the image, and non-shaded areas may include Figure 5 The area outside of several shaded points. Understandably, the pixel values ​​in shaded areas are generally lower (darker), while the pixel values ​​in unshaded areas are higher (brighter).

[0067] In some embodiments, the electronic device may perform image segmentation based on a preset pixel threshold. The corresponding process may include: identifying pixels with pixel values ​​less than the preset pixel threshold from a plurality of pixels in an empty field image; defining the region formed by pixels with pixel values ​​less than the preset pixel threshold as a shadow region; and defining other regions outside the shadow region as non-shadow regions. The preset pixel threshold is used to filter pixels located in shadow regions. It is understood that pixels with pixel values ​​less than the preset pixel threshold are considered to be located in shadow regions.

[0068] In other embodiments, the electronic device may perform image segmentation based on an image segmentation model. The corresponding process may include: inputting an empty field image into the image segmentation model, processing the empty field image through the image segmentation model to obtain shadowed and non-shadowed regions in the empty field image. The image segmentation model is used to identify shadowed and non-shadowed regions in the image.

[0069] It is worth noting that electronic devices can also use other methods to achieve the above-mentioned image segmentation of empty field images, such as image segmentation based on clustering algorithms or image segmentation based on edge detection. This disclosure does not limit the scope of the embodiments.

[0070] Step 3: The electronic device performs binarization processing on the empty field image based on the shadow and non-shadow regions in the empty field image to obtain the first shadow image.

[0071] Binarization refers to converting pixel values ​​in an image to 0 or 1, thereby converting the image into a binary image.

[0072] In some embodiments, the electronic device converts the pixel values ​​of pixels included in the shadowed regions of an empty field image to 0, and converts the pixel values ​​of pixels included in the non-shadowed regions to 1. For example, Figure 6 This is a schematic diagram illustrating a first shadow image according to an embodiment of this disclosure. See also... Figure 6 As shown in (1), the pixel value of the shaded area is 0, which is represented by black shadow points, and the pixel value of the non-shaded area is 1, which is represented by white areas.

[0073] Alternatively, in other embodiments, the electronic device converts the pixel values ​​of pixels included in the shadowed regions of the open field image to 1, and converts the pixel values ​​of pixels included in the non-shadowed regions to 0. For example, see [link to example]. Figure 6 As shown in (2), the pixel value of the shaded area is 1, which is represented by white shadow points, and the pixel value of the non-shaded area is 0, which is represented by black areas.

[0074] Based on steps one through three above, image segmentation is performed on the empty field image to determine multiple shadow points in the empty field image, thereby generating a binarized first shadow image. Acquiring the empty field image allows for the determination of the scattering distribution when no object is being scanned, which is beneficial for subsequent identification of the shadow regions formed on the detector by each beam blocker in the BSA. Furthermore, binarization significantly improves the effectiveness of subsequent ring artifact correction.

[0075] Furthermore, in some other embodiments, the shadow region can be a target shadow region. The target shadow region is any area within the shadow region other than the penumbra. The electronic device can use the second shadow image to determine the target shadow region in the projected image. The corresponding process can be: the electronic device acquires the second shadow image; then, the electronic device determines the target shadow region in the projected image based on the second shadow image.

[0076] The second shadow image is used to indicate areas other than the penumbra region in the shadow region of the projected image. In this embodiment, the second shadow image can also be called a mask image, used to indicate the positions of areas other than the penumbra region in the shadow region of the projected image. Exemplarily, the second shadow image is used to indicate the pixel positions, such as pixel coordinates, of areas other than the penumbra region in the shadow region of the projected image. In some possible implementations, the second shadow image is also a binary image. Exemplarily, in this embodiment, the second projected image will subsequently be referred to as mask2. It is understood that the second shadow image is obtained by removing the penumbra region from the first shadow image.

[0077] It is worth noting that the process by which the electronic device determines the target shadow region in the projected image based on the second shadow image is similar to the process described above, where the electronic device determines the shadow region in the projected image based on the first shadow image, and will not be repeated here. Thus, since the second shadow image is obtained by removing the penumbra region from the first shadow image, the shadow region in the second shadow image is smaller, resulting in fewer and finer ring artifacts in the subsequent reconstructed image. Therefore, using the second shadow image to determine the shadow region in the projected image at various angles can help correct subsequent ring artifacts.

[0078] The process of an electronic device acquiring a second shadow image may include the following steps one to two.

[0079] Step 1: The electronic device acquires the penumbra information of the projected image.

[0080] The penumbra information is used to indicate the penumbra region within the shadow area of ​​the projected image.

[0081] In some possible implementations, after the electronic device determines the shadow region in the projected image based on the first shadow image, it can select a target pixel from the multiple pixels included in the shadow region of the projected image. Then, the electronic device obtains the position information of the target pixel as the penumbra information of the projected image.

[0082] In this context, the target pixel is defined as a pixel whose ray intensity is greater than a ray intensity threshold. In some possible implementations, after determining the shadow region of the projected image using the first shadow image, ray starvation filtering is performed on the grayscale value of each pixel within each shadow region of the projected image to filter out pixels with ray intensity greater than the ray intensity threshold, thereby obtaining the target pixel. Ray starvation filtering involves filtering the grayscale value of each pixel based on ray intensity. The ray intensity threshold is a pre-set user-experienced value, such as a ray intensity value within 100.

[0083] In some possible implementations, the target pixel is a pixel carrying a first label. For example, when performing ray-hunting screening on the grayscale value of each pixel, a first label can be added to pixels with ray intensity greater than a ray intensity threshold, such as labeling them as usable point 0, and a second label can be added to pixels with ray intensity less than or equal to the ray intensity threshold, such as labeling them as unusable point 1. It is understood that the pixels with the first label are also pixels belonging to the penumbra region.

[0084] Step 2: The electronic device processes the first shadow image based on the penumbra information to obtain the second shadow image.

[0085] In some possible implementations, the electronic device can perform pixel value transformation on the pixels belonging to the penumbra region in the shadow area of ​​the first shadow image based on penumbra information to obtain a second shadow image.

[0086] For example, using the first shadow image as Figure 6 Taking the image shown in (1) as an example, the electronic device can determine the pixels belonging to the penumbra region in the shadow area of ​​the first shadow image based on the penumbra information, and convert the pixel value of the determined pixels from 0 to 1 to obtain the image shown in (1). Figure 7 The second shaded image shown in (1). Exemplarily, Figure 7 This is a schematic diagram illustrating a second shadow image according to an embodiment of this disclosure. See also... Figure 7 As shown in (1), the pixel value of the shaded area is 0, which is represented as a black shadow point, and the pixel value of the non-shaded area is 1, which is represented as a white area. Figure 6 By comparing the first shaded image shown in (1), it can be found that, Figure 7 The shadow area, i.e. the black shadow point, of the second shadow image shown in (1) is smaller.

[0087] For example, taking the first shadow image as... Figure 6 Taking the image shown in (2) as an example, the electronic device can determine the pixels belonging to the penumbra region in the shadow area of ​​the first shadow image based on the penumbra information, and change the pixel value of the determined pixels from 1 to 0 to obtain the image shown in (2). Figure 7 The second shaded image shown in (2). See also Figure 7 As shown in (2), the pixel value of the shaded area is 1, which is represented by a white shaded point, while the pixel value of the non-shaded area is 0, which is represented by a black area. Figure 6 By comparing the first shaded image shown in (2), it can be found that, Figure 7 The shadow area, i.e. the white shadow point, of the second shadow image shown in (2) is smaller.

[0088] In the above embodiments, by using the penumbra information of the target pixel point, i.e. the available point carrying the first mark, to update the first shadow image such as mask1, a second shadow image such as mask2 with more available points can be obtained.

[0089] For example, Figure 8 This is a schematic diagram illustrating a penumbra region according to an embodiment of this disclosure. See also... Figure 8 The penumbra is the edge region located between the shaded region (the region to be interpolated) and the non-shaded region (i.e., the ideal data region). Thus, by removing the penumbra from the shaded region and incorporating it into the non-shaded region, the shaded region in the second shadow image is smaller and the non-shaded region is larger. This preserves as much structural information of the scanned object as possible, resulting in fewer and finer ring artifacts in the subsequent reconstructed image. Therefore, using the second shadow image to determine the shadow region in the projected image at various angles can help correct subsequent ring artifacts.

[0090] S402. The electronic device determines the position information of the ring artifact corresponding to the shadow point based on the position information of the shadow point in the shadow area.

[0091] In some possible implementations, after acquiring the projected image based on S401 above and determining the shadow region in the projected image based on the first shadow image or the second shadow image, the position information of each shadow point in the shadow region is also determined. In this embodiment of the disclosure, the position information of the shadow point can be the position coordinates of the center of the shadow point, such as the position coordinates of the center of the shadow point in the detector coordinate system. Here, the center of the shadow point refers to the geometric center or centroid of the shadow point.

[0092] The detector coordinate system is a two-dimensional coordinate system established on the detector plane, used to describe the two-dimensional coordinates of each pixel in the projected image. For example, the detector coordinate system can be a UV coordinate system. For instance, the origin (0, 0) of the UV coordinate system can be located at the center of the detector. It is worth noting that the origin (0, 0) of the UV coordinate system is aligned with the line connecting the light source (i.e., the focal point) and the isocenter (ISO). The U-axis is the coordinate axis along the row direction of the detector, typically a horizontal axis. The V-axis is the coordinate axis along the column direction of the detector, typically a vertical axis. Accordingly, the position information of the shadow points can be represented using (u, v), where u represents the horizontal coordinate of the projected image, and v represents the vertical coordinate of the projected image.

[0093] S403. The electronic device corrects the ring artifacts based on the position information of the ring artifacts corresponding to the shadow points.

[0094] In some embodiments of this disclosure, the position information of the annular artifact is used to indicate the fringe position of the annular artifact in a polar coordinate image. The polar coordinate image is obtained by converting a slice image of the annular artifact in the reconstructed image. Accordingly, S403 can be replaced by: the electronic device determining the fringe position of the annular artifact in the polar coordinate image based on the position information of the annular artifact corresponding to the shadow point. Furthermore, the electronic device corrects the annular artifact based on the fringe position of the annular artifact in the polar coordinate image. Thus, a method for correcting annular artifacts in the reconstruction domain is provided. The embodiments of this disclosure will be discussed later in conjunction with... Figure 9 The method for correcting ring artifacts based on polar coordinate images is introduced, but will not be elaborated upon here.

[0095] In other embodiments of this disclosure, the position information of the annular artifact is used to indicate the fringe position of the annular artifact in a sinusoidal image. The sinusoidal image is obtained by converting a projected image. Accordingly, S403 described above can be replaced by: the electronic device determining the fringe position of the annular artifact in the sinusoidal image based on the position information of the annular artifact corresponding to the shadow point. Furthermore, the electronic device corrects the annular artifact based on the fringe position of the annular artifact in the sinusoidal image. Thus, a method for correcting annular artifacts in the projection domain is provided. The embodiments of this disclosure will be discussed later in conjunction with... Figure 12 The method for correcting ring artifacts based on sinusoidal images is introduced, but will not be elaborated upon here.

[0096] The technical solution provided in this disclosure determines the location information of the ring artifacts corresponding to the shadow points, and then performs targeted correction of the ring artifacts based on the location information of the ring artifacts, which can more accurately remove the ring artifacts and thus improve the accuracy of the ring artifact correction.

[0097] In some embodiments of this disclosure, the positional information of the annular artifact is used to indicate the position of the stripes in a polar coordinate image. The following is based on... Figure 9 This paper introduces a method for correcting annular artifacts based on polar coordinate images, which enables the correction of annular artifacts in the reconstruction domain. Figure 9 This is a schematic flowchart illustrating another method for correcting annular artifacts according to an embodiment of this disclosure. In some embodiments, the method for correcting annular artifacts is performed by an electronic device. Figure 9 As shown, with an electronic device as the executing entity, the method includes the following steps.

[0098] S901, Electronic equipment acquires projected images.

[0099] The content of S901 is the same as that shown in S401 above, and will not be repeated here.

[0100] S902. The electronic device determines the ring radius and slice position of the ring artifact corresponding to the shadow point in the reconstructed image based on the position information of the shadow point.

[0101] In some possible implementations, the electronic device determines the radius of the ring artifact corresponding to the shadow point in the reconstructed image based on the first position coordinates of the shadow point. Here, the first position coordinates refer to the coordinates in the horizontal direction of the projected image, i.e., u.

[0102] For example, Figure 10 This is a diagram illustrating the positional relationship between a ring-shaped artifact and a detector shadow point, as shown in an embodiment of this disclosure. See also... Figure 10 Based on the geometric relationships of the CBCT system, it can be found that... Figure 10 The triangle formed by the light source (focus), ISO, and tangent point is similar to the triangle formed by the center of the light source, the detector, and the shadow point. Therefore, the following relationship function exists (1).

[0103] (1) In the formula, This represents the radius of the ring-shaped artifact corresponding to the shaded point in the reconstructed image; This represents the first position coordinate of the shaded point, i.e., u; Indicates the distance between the light source and the ISO; This indicates the distance between the light source and the detector.

[0104] Based on the above relational function (1), the electronic device determines the ring radius of the ring artifact corresponding to the shadow point in the reconstructed image based on the first position coordinates of the shadow point, the distance between the light source and ISO, the distance between the light source and the detector, and the following formula (2).

[0105] (2) In the above embodiments, a method for determining the ring radius of a ring artifact in a reconstructed image is provided, which can quickly and accurately determine the ring radius of a ring artifact in a reconstructed image, laying the foundation for subsequent correction of ring artifacts.

[0106] In some possible implementations, the electronic device determines the slice position of the annular artifact corresponding to the shadow point in the reconstructed image based on the second position coordinates of the shadow point. Here, the second position coordinates refer to the coordinates in the vertical direction of the projected image, i.e., v.

[0107] For example, the electronic device determines the slice position of the ring artifact corresponding to the shadow point in the reconstructed image based on the second position coordinates of the shadow point, the distance between the light source and the ISO, the distance between the light source and the detector, and the following formula (3).

[0108] (3) In the formula, This indicates the slice position of the ring artifact corresponding to the shaded point in the reconstructed image; Indicates the second position coordinates of the shaded point; Indicates the distance between the light source and the ISO; This indicates the distance between the light source and the detector.

[0109] The slice position of the annular artifact in the reconstructed image is determined based on its slice position in the reconstructed coordinate system. The reconstructed coordinate system is a three-dimensional coordinate system established in the image reconstruction space, used to describe the three-dimensional coordinates of each voxel in the reconstructed image within this system. For example, the reconstructed coordinate system could be as follows: Figure 10 The diagram shows an XYZ coordinate system. The origin of the XYZ coordinate system (0, 0, 0) is typically located at ISO. It is worth noting that the X-axis in the XYZ coordinate system corresponds to the U-axis in the UV coordinate system, and the Y-axis in the XYZ coordinate system corresponds to the V-axis in the UV coordinate system.

[0110] In the above embodiments, a method is provided to determine the slice position of the ring artifact in the reconstructed image, which can quickly and efficiently determine the slice position of the ring artifact in the reconstructed image, laying the foundation for subsequent ring artifact correction.

[0111] Furthermore, in some possible implementations, the electronic device may also correct the first position coordinates of the shadow point based on the first offset. Here, the first offset is the offset in the horizontal direction of the projected image.

[0112] For example, the electronic device may also correct the first position coordinates of the shadow point based on the first offset, the first position coordinates of the shadow point and the following formula (4).

[0113] (4) In the formula, Indicates the first position coordinates of the shaded point; This indicates the horizontal offset of the projected image, such as the offset in the u direction.

[0114] Similarly, in some possible implementations, the electronic device can also correct the second position coordinates of the shadow point based on the second offset. Here, the second offset is the offset in the vertical direction of the projected image.

[0115] For example, the electronic device may also correct the second position coordinates of the shadow point based on the second offset, the second position coordinates of the shadow point and the following formula (5).

[0116] (5) In the formula, Indicates the second position coordinates of the shaded point; This represents the offset in the vertical direction of the projected image, such as the offset in the v direction.

[0117] In the above implementation, by correcting the first position coordinates of the shadow point with the first offset and the second position coordinates of the shadow point with the second offset, more accurate position coordinates can be obtained, laying the foundation for subsequent accurate correction of annular artifacts.

[0118] S903. The electronic device performs polar coordinate transformation on the slice image corresponding to the slice position in the reconstructed image to obtain a polar coordinate image.

[0119] The reconstructed image is a three-dimensional image obtained by converting a two-dimensional projected image using a reconstruction algorithm, such as a CBCT image, i.e., a CBCT reconstructed image. A slice image refers to a two-dimensional cross-sectional image extracted from the reconstructed image. Exemplarily, in this embodiment, I(x, y, z) will be used to refer to the reconstructed image, and I(x, z) will refer to the slice image corresponding to the slice position in the reconstructed image.

[0120] In some embodiments, the electronic device acquires a reconstructed image and determines a slice image in the reconstructed image that corresponds to the slice position. Then, the electronic device performs a polar coordinate transformation on the slice image in the reconstructed image that corresponds to the slice position to obtain a polar coordinate image.

[0121] In some possible implementations, the process of an electronic device acquiring a reconstructed image may be as follows: the electronic device interpolates the shadow regions in a projection image from multiple angles based on a first shadow image or a second shadow image to obtain a reconstructed image. The interpolation can be any of nearest neighbor interpolation, bilinear interpolation, piecewise interpolation, or spline interpolation, and this disclosure does not limit the specific interpolation method used.

[0122] In addition, the electronic device can also perform log transformation on the projected image at each angle according to Beer's Law and the following formula (6) to obtain the object attenuation line integral of the projected image at each angle.

[0123] (6) In the formula, Represents the object attenuation line integral of the projected image; Represents an empty field image; This represents a projected image.

[0124] Furthermore, after obtaining the object attenuation line integrals of the projected images from various angles, object attenuation line integral images from each angle can be obtained. Then, the electronic device can interpolate the shadow regions in the object attenuation line integral images from multiple angles based on the first shadow image or the second shadow image to obtain a reconstructed image. Here, the object attenuation line integral image refers to an image reflecting the internal structure of an object, generated by measuring the attenuation of rays (such as X-rays or gamma rays) as they pass through the object. Thus, generating object attenuation line integral images of the projected images from various angles through log transform allows for subsequent interpolation and reconstruction of the object attenuation line integral images, improving the accuracy of image reconstruction.

[0125] In some possible implementations, the process of the electronic device performing polar coordinate transformation on the sliced ​​image can be as follows: the electronic device transforms the sliced ​​image from a Cartesian coordinate system to a polar coordinate system, for example, from (x, z) coordinates to (r, θ) coordinates. Exemplarily, in this embodiment of the disclosure, P(r, θ) will be used to refer to the polar coordinate image, where r is the radius and θ is the polar angle.

[0126] For example, Figure 11 This is a schematic diagram of a polar coordinate image shown in an embodiment of this disclosure. See also... Figure 11 In a polar coordinate image, one dimension is the radius r and the other dimension is the polar angle θ. The ring artifact appears as stripes in the polar coordinate image.

[0127] S904. The electronic device determines the position of the stripes of the annular artifact in the polar coordinate image based on the ring radius, thereby obtaining the position information of the annular artifact.

[0128] Wherein, S902 to S904 correspond to the above Figure 4 S402 in the text refers to the electronic device determining the position information of the ring artifact corresponding to the shadow point based on the position information of the shadow point in the shadow area.

[0129] S905. In a polar coordinate image, the electronic device filters the stripes at the position indicated by the position information of the ring artifact to obtain a filtered polar coordinate image.

[0130] In some embodiments, the electronic device determines the fringe position of the annular artifact in the polar coordinate image based on the ring radius of the annular artifact in the reconstructed image. Then, the electronic device performs one-dimensional median filtering along the radial direction on the fringes at the determined fringe positions to obtain a filtered polar coordinate image.

[0131] One-dimensional median filtering refers to replacing the original value of a data point with the median of all values ​​within its neighborhood. By using one-dimensional median filtering, image boundaries can be preserved while eliminating noise points. For locations other than stripe positions, filtering may not be performed, or a small filter kernel may be used. This disclosure does not limit this. A small filter kernel refers to a small-sized filter kernel, such as a 3×3 or 5×5 matrix. Exemplarily, in this disclosure, P will be used subsequently. filt (r, θ) is used to refer to the filtered polar coordinate image.

[0132] In the above embodiments, based on the ring radius of the ring artifact in the reconstructed image, one-dimensional median filtering is performed on the stripes at the specified stripe positions along the radial direction, which can achieve accurate filtering of stripes in polar coordinate images, thereby obtaining a filtered polar coordinate image, that is, a polar coordinate image without straight lines.

[0133] In other embodiments, the electronic device determines the fringe position of the annular artifact in the polar coordinate image based on the ring radius of the annular artifact in the reconstructed image. Then, the electronic device performs wavelet Fourier transform straightening processing along the radial direction on the fringes at the fringe position to obtain a filtered polar coordinate image.

[0134] Among them, wavelet Fourier transform is used to remove straight lines or stripes in a specific direction in the frequency domain. It is worth noting that when performing wavelet Fourier transform, the parameters of the wavelet Fourier algorithm can be adaptively adjusted according to the stripe position corresponding to the ring artifacts of BSA, thereby achieving more accurate filtering.

[0135] In the above embodiments, based on the ring radius of the ring artifact in the reconstructed image, wavelet Fourier straight-line removal processing is performed on the stripes at the specified stripe positions along the radial direction. This can also achieve accurate filtering of stripes in the polar coordinate image, thereby obtaining the filtered polar coordinate image, i.e., a polar coordinate image without straight lines.

[0136] S906. Electronic equipment corrects ring artifacts in sliced ​​images based on polar coordinate images before and after filtering.

[0137] In some embodiments, the electronic device determines the difference image between the polar coordinate image before filtering and the polar coordinate image after filtering to obtain a first ring image. The first ring image is the image of the ring artifact in polar coordinates. The electronic device performs a Cartesian coordinate transformation on the first ring image to obtain a second ring image. The second ring image is the image of the ring artifact in Cartesian coordinates. Furthermore, the electronic device determines the difference image between the slice image and the second ring image, thus obtaining the corrected slice image.

[0138] For example, in this embodiment of the disclosure, P is used. ring Let (r, θ) represent the first ring image, then P ring (r, θ) = P(r, θ) - P filt (r, θ). In some possible implementations, after obtaining the first ring image P ring After (r, θ), we can also analyze the first ring image P. ring (r, θ) is used to perform one-dimensional mean filtering along the θ direction to remove interference structures outside the loop.

[0139] Furthermore, for the first ring image P ring The second ring image R(x, z) is obtained by performing a Cartesian coordinate transformation on (r, θ). The second ring image R(x, z) is then subtracted from the original slice image I(x, z). This completes the correction of the ring artifact.

[0140] Wherein, S905 to S906 correspond to the above Figure 4 S403 in the text refers to the process by which the electronic device corrects the ring artifacts based on the position information of the ring artifacts corresponding to the shadow points.

[0141] It is worth noting that the above Figure 9 The illustrated embodiment describes the correction process for ring artifacts in a slice image corresponding to a single slice location at a shaded point. In this embodiment, the above process needs to be repeated for slice images corresponding to all slice locations at all shaded points. Figure 9 The process shown completes the correction of ring artifacts caused by all shadow points.

[0142] In the above Figure 9 In the illustrated embodiment, the positional information of the shadow points in the shadow region caused by BSA in the projected image is used to deduce the prior positional information of the ring radius and slice position of the ring artifact in the reconstructed image. Then, combined with the prior positional information of the ring radius and slice position of the ring artifact in the reconstructed image, the fringe position of the ring artifact in the polar coordinate image is deduced. Then, targeted ring removal is performed, which can remove the ring artifact more accurately and improve the accuracy of ring artifact correction.

[0143] In other embodiments of this disclosure, the location information of the annular artifact is used to indicate the position of the stripes in the sinusoidal image. The following is based on... Figure 12 This paper introduces a method for correcting annular artifacts based on sinusoidal images, which enables the correction of annular artifacts in the projection domain. Figure 12 This is a schematic flowchart illustrating another method for correcting annular artifacts according to an embodiment of this disclosure. In some embodiments, the method for correcting annular artifacts is performed by an electronic device. Figure 12As shown, with an electronic device as the executing entity, the method includes the following steps.

[0144] S1201, Electronic device acquires projected image.

[0145] The content of S1201 is the same as that shown in S401 above, and will not be repeated here.

[0146] S1202. The electronic device converts the projected image into a sinusoidal image based on the position information of the shadow point and multiple preset projection angles.

[0147] In some embodiments, for each shadow point, the electronic device, based on the second position coordinate (v) of the shadow point, traverses a plurality of preset projection angles and extracts the first position coordinate (u) corresponding to the second position coordinate from the projected images of the plurality of preset projection angles, thereby obtaining a sine graph at the v coordinate of each shadow point. Exemplarily, in this embodiment, the sine graph will subsequently be referred to as S(u, viewangle). Here, viewangle represents the frame angle, i.e., the plurality of preset projection angles.

[0148] For example, Figure 13 This is a schematic diagram of a sinusoidal image shown in an embodiment of this disclosure. See also... Figure 13 In a sinusoidal image, one dimension is the detector's u-coordinate, and the other dimension is the projection angle. The ring artifact appears as stripes in the sinusoidal image.

[0149] S1203. The electronic device determines the position of the ring artifact in the sine image based on the position information of the shadow point, and obtains the position information of the ring artifact.

[0150] Wherein, S1202 to S1203 correspond to the above Figure 4 S402 in the text refers to the electronic device determining the position information of the ring artifact corresponding to the shadow point based on the position information of the shadow point in the shadow area.

[0151] S1204. In a sinusoidal image, the electronic device filters the stripes at the stripe positions indicated by the position information of the ring artifacts to obtain a filtered sinusoidal image.

[0152] In some embodiments, the electronic device determines the position of the ring artifact in the fringe of the sinusoidal image based on the first position coordinates (i.e., u) of the shadow point. Then, the electronic device performs one-dimensional median filtering or wavelet Fourier straight-line removal processing on the fringe at the determined fringe position to obtain the filtered sinusoidal image.

[0153] S1205. The electronic device corrects the ring artifacts in the projected image based on the sinusoidal image before and after filtering.

[0154] In some embodiments, the electronic device determines the difference image between the sinusoidal image before filtering and the sinusoidal image after filtering to obtain a third ring image. The third ring image is a sinusoidal image of the ring artifact. The electronic device then transforms the third ring image to obtain a fourth ring image. The fourth ring image is a projected image of the ring artifact. Furthermore, the electronic device determines the difference image between the projected image and the fourth ring image, thus obtaining the corrected projected image.

[0155] Wherein, S1204 to S1205 correspond to the above Figure 4 S403 in the text refers to the process by which the electronic device corrects the ring artifacts based on the position information of the ring artifacts corresponding to the shadow points.

[0156] It is worth noting that the above Figure 12 The illustrated embodiment describes a process for correcting ring artifacts in a sinusoidal image obtained by converting a projected image. In this embodiment, the above process needs to be repeated for all sinusoidal images corresponding to all projected images. Figure 12 The process shown corrects the ring artifacts caused by shadow points in all projected images. Then, interpolation and reconstruction are performed based on the corrected projected images to improve the accuracy of image reconstruction.

[0157] In the above Figure 12 In the illustrated embodiment, the position information of the shadow points in the shadow area caused by BSA in the projected image is used to deduce the stripe position of the ring artifact in the sine image, and then targeted ring removal is performed, thereby more accurately removing the ring artifact and improving the accuracy of ring artifact correction.

[0158] According to embodiments of the present disclosure, the present disclosure also provides an electronic device, including at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the ring artifact correction method provided in the present disclosure.

[0159] According to embodiments of this disclosure, this disclosure also provides a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to cause an electronic device to perform the ring artifact correction method provided in this disclosure.

[0160] According to embodiments of this disclosure, this disclosure also provides a computer program product, including a computer program that, when executed by a processor, implements the ring artifact correction method provided in this disclosure.

[0161] Figure 14 This is a block diagram of an electronic device for a method of correcting ring artifacts according to an embodiment of this disclosure. See also: Figure 14 Electronic device 1400 is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic device 1400 may also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present disclosure described and / or claimed herein.

[0162] like Figure 4 As shown, the electronic device 1400 includes a computing unit 1401, which can perform various appropriate actions and processes according to a computer program stored in read-only memory (ROM) 1402 or a computer program loaded from storage unit 1408 into random access memory (RAM) 1403. The RAM 1403 may also store various programs and data required for the operation of the electronic device 1400. The computing unit 1401, ROM 1402, and RAM 1403 are interconnected via a bus 1404. An input / output (I / O) interface 1405 is also connected to the bus 1404.

[0163] Multiple components in electronic device 1400 are connected to I / O interface 1405, including: input unit 1406, such as keyboard, mouse, etc.; output unit 1407, such as various types of monitors, speakers, etc.; storage unit 1408, such as disk, optical disk, etc.; and communication unit 1409, such as network card, modem, wireless transceiver, etc. Communication unit 1409 allows electronic device 1400 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0164] The computing unit 1401 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 1401 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any suitable processor, controller, microcontroller, etc. The computing unit 1401 performs the various methods and processes described above, such as the ring artifact correction method. For example, in some embodiments, the ring artifact correction method may be implemented as a computer software program tangibly contained in a machine-readable medium, such as storage unit 1408. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 1400 via ROM 1402 and / or communication unit 1409. When the computer program is loaded into RAM 1403 and executed by computing unit 1401, one or more steps of the ring artifact correction method described above can be performed. Alternatively, in other embodiments, computing unit 1401 can be configured to perform the ring artifact correction method by any other suitable means (e.g., by means of firmware).

[0165] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard parts (ASSPs), systems-on-chip (SoCs), complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0166] The program code used to implement the methods of this disclosure may be written in any combination of one or more programming languages. This program code may be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may be executed entirely on a machine, partially on a machine, as a standalone software package partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0167] In the context of this disclosure, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory, read-only memory, erasable programmable read-only memory (EPROM or flash memory), optical fibers, compact disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0168] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device for displaying information to the user, such as a cathode ray tube (CRT) or liquid crystal display (LCD) monitor; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0169] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as a data server), or computing systems that include middleware components (e.g., an application server), or computing systems that include frontend components (e.g., a user computer with a graphical user interface or web browser through which a user can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., a communication network). Examples of communication networks include local area networks (LANs), wide area networks (WANs), and the Internet.

[0170] Computer systems can include clients and servers. Clients and servers are generally located far apart and typically interact via communication networks. Client-server relationships are created by computer programs running on the respective computers and having a client-server relationship with each other. Servers can be cloud servers, servers in distributed systems, or servers incorporating blockchain technology.

[0171] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this disclosure can be achieved, and this is not limited herein.

[0172] The specific embodiments described above do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A method for correcting ring artifacts, characterized in that, include: Acquire a projection image, the projection image including a shadow region, wherein a shadow point in the shadow region corresponds to a ring artifact; Based on the position information of the shadow points in the shadow region, determine the position information of the annular artifact corresponding to the shadow points; The annular artifacts are corrected based on the position information of the annular artifacts corresponding to the shadow points.

2. The method according to claim 1, characterized in that, The position information of the annular artifact is used to indicate the position of the stripes of the annular artifact in the polar coordinate image, which is obtained by converting the slice image of the annular artifact in the reconstructed image; The step of determining the position information of the annular artifact corresponding to the shadow point based on the position information of the shadow point in the shadow region includes: Based on the location information of the shadow point, determine the ring radius and slice position of the ring artifact corresponding to the shadow point in the reconstructed image; The reconstructed image is transformed into polar coordinates by performing a polar coordinate transformation on the slice image corresponding to the slice position to obtain the polar coordinate image. Based on the ring radius, the position of the stripes in the polar coordinate image of the ring artifact is determined, and the position information of the ring artifact is obtained.

3. The method according to claim 2, characterized in that, The step of determining the ring radius and slice position of the ring artifact corresponding to the shadow point in the reconstructed image based on the position information of the shadow point includes: Based on the first position coordinates of the shadow point, the ring radius of the ring artifact corresponding to the shadow point in the reconstructed image is determined, where the first position coordinates are the coordinates in the horizontal direction of the projected image; Based on the second position coordinates of the shadow point, the slice position of the ring artifact corresponding to the shadow point in the reconstructed image is determined, where the second position coordinates are the coordinates in the vertical direction of the projected image.

4. The method according to claim 3, characterized in that, The method further includes: Based on the first offset, the first position coordinates of the shadow point are corrected, where the first offset is the offset in the horizontal direction of the projected image; Based on the second offset, the second position coordinates of the shadow point are corrected, where the second offset is the offset in the vertical direction of the projected image.

5. The method according to claim 2, characterized in that, The step of correcting the annular artifact based on the position information of the annular artifact corresponding to the shadow point includes: In the polar coordinate image, based on the fringe positions indicated by the position information of the annular artifact, the fringe at the fringe positions is filtered to obtain the filtered polar coordinate image; Based on the polar coordinate image before and after filtering, the ring artifacts in the slice image are corrected.

6. The method according to claim 5, characterized in that, The correction of ring artifacts in the sliced ​​image based on the polar coordinate image before and after filtering includes: The difference image between the polar coordinate image before filtering and the polar coordinate image after filtering is determined to obtain the first ring image, which is the image of the ring artifact in the polar coordinate system; The first ring image is transformed into Cartesian coordinates to obtain the second ring image, which is the image of the ring artifact in Cartesian coordinates. Determine the difference image between the slice image and the second ring image.

7. The method according to claim 1, characterized in that, The position information of the annular artifact is used to indicate the position of the stripes of the annular artifact in the sinusoidal image, which is obtained by converting the projected image; The step of determining the position information of the annular artifact corresponding to the shadow point based on the position information of the shadow point in the shadow region includes: Based on the location information of the shadow points and multiple preset projection angles, the projected image is converted to obtain the sine image; Based on the position information of the shadow points, the position of the stripes in the sine image of the annular artifact is determined, and the position information of the annular artifact is obtained.

8. The method according to claim 7, characterized in that, The step of correcting the annular artifact based on the position information of the annular artifact corresponding to the shadow point includes: In the sinusoidal image, based on the position information of the ring artifact indicating the stripe position, the stripes at the stripe position are filtered to obtain the filtered sinusoidal image; Based on the sinusoidal image before and after filtering, the ring artifacts in the projection image are corrected.

9. The method according to claim 8, characterized in that, The step of correcting the ring artifacts in the projected image based on the sinusoidal image before and after filtering includes: The difference image between the sinusoidal image before filtering and the sinusoidal image after filtering is determined to obtain the third ring image, which is the sinusoidal image of the ring artifact; The third ring image is transformed to obtain a fourth ring image, which is the projection image of the ring artifact; Determine the difference image between the projected image and the fourth ring image.

10. The method according to claim 1, characterized in that, The method further includes: A first shadow image is obtained, which is used to indicate the shadow area in the projected image; Based on the first shadow image, the shadow area in the projected image is determined.

11. The method according to claim 10, characterized in that, The acquisition of the first shadow image includes: Acquire an empty field image, which is a projected image when there is no object being scanned; The empty field image is segmented to obtain the shadowed and non-shadowed regions in the empty field image; Based on the shadow and non-shadow regions in the empty field image, the empty field image is binarized to obtain the first shadow image.

12. The method according to claim 1, characterized in that, The shadowed area is the target shadowed area, which is the area within the shadowed area excluding the penumbra; the method further includes: A second shadow image is obtained, which is used to indicate areas other than the penumbra region in the shadow region of the projected image; Based on the second shadow image, the target shadow region in the projected image is determined.

13. The method according to claim 12, characterized in that, The acquisition of the second shadow image includes: Obtain the penumbra information of the projected image, wherein the penumbra information is used to indicate the penumbra region in the shadow region of the projected image; The first shadow image is processed based on the penumbra information to obtain the second shadow image, wherein the first shadow image is used to indicate the shadow area in the projected image.

14. The method according to claim 13, characterized in that, The process of processing the first shadow image based on the penumbra information to obtain the second shadow image includes: Based on the penumbra information, the pixel values ​​of the pixels belonging to the penumbra region in the shadow region of the first shadow image are transformed to obtain the second shadow image.

15. An electronic device, characterized in that, include: At least one processor; as well as A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method as described in any one of claims 1 to 14.

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