Systems and methods for image reconstruction

A method for image reconstruction, implemented on a computing device having at least one processor and at least one storage device, the method comprising:

• obtaining a projection image of a subject acquired by an imaging device, the projection image including a first region with a normal exposure corresponding to a first portion of the subject and a second region with an overexposure corresponding to a second portion of the subject;
• using first pixel values of first pixels in the first region to correct second pixel values of second pixels in the second region, including:
• correcting, using the first pixel values of the first pixels in the first region, the second pixel values of the second pixels in the second region one by one starting from a second pixel adjacent to the first region;
• and
• reconstructing, based on the first pixel values of the first pixels in the first region and the corrected second pixel values of the second pixels in the second region, a target image of the subject.

A non-transitory computer readable medium, comprising at least one set of instructions for image reconstruction, wherein when executed by at least one processor of a computing device, the at least one set of instructions direct the at least one processor to perform operations including:

• obtaining a projection image of a subject acquired by an imaging device, the projection image including a first region with a normal exposure corresponding to a first portion of the subject and a second region with an overexposure corresponding to a second portion of the subject;
• using first pixel values of first pixels in the first region to correct second pixel values of second pixels in the second region, including:
• correcting, using the first pixel values of the first pixels in the first region, the second pixel values of the second pixels in the second region one by one starting from a second pixel adjacent to the first region;
• and
• reconstructing, based on the first pixel values of the first pixels in the first region and the corrected second pixel values of the second pixels in the second region, a target image of the subject;
• wherein the correcting, using the first pixel values of the first pixels in the first region, at least one of the second pixel values of the second pixels in the second region one by one starting from a second pixel adjacent to the first region includes:
• for a current second pixel to be corrected,
• determining a value reference pixel corresponding to the current second pixel, the value reference pixel being a first pixel in the first region or a corrected second pixel in the second region;
• determining a gradient reference pixel in the first region corresponding to the current second pixel;
• determining a local pixel gradient value of the gradient reference pixel;
• and
• determining, based on a reference pixel value of the value reference pixel and the local pixel gradient value of the gradient reference pixel, the corrected second pixel value of the current second pixel;
• wherein the determining a local pixel gradient value of the gradient reference pixel includes:
• determining, based on the gradient reference pixel, two gradient estimation pixels;
• and
• determining, based on pixel values of the two gradient estimation pixels and a count of pixels spacing the two gradient estimation pixels, the local pixel gradient value of the gradient reference pixel, wherein the determining, based on the gradient reference pixel, two gradient estimation pixels includes:
• designating a first pixel located in a same row as the gradient reference pixel and separated by a second count of pixels as one of the two gradient estimation pixels;
• and
• designating a first pixel located in the same row as the gradient reference pixel and separated by a third count of pixels as another gradient estimation pixel, the gradient reference pixel being between the two gradient estimation pixels.