# US 2016/0366353 A1 · Image processing apparatus, radiation imaging apparatus, image processing method, and storage medium > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0366353 A1 - Document ID: US20160366353A1 - Status: Published application - Kind: A1 - Application number: 15/172,638 - Filed: 2016-06-03 - Published: 2016-12-15 - Earliest claimed: 2015-06-12 - Assignees: Canon Kabushiki Kaisha - Applicants: Canon Kabushiki Kaisha - Inventors: Tsuyoshi Kobayashi - Web page: https://patentgrep.com/patent/US20160366353A1 ## CPC - A61B 6/5205: {involving processing of raw data to produce diagnostic data} - A61B 6/5258: {involving detection or reduction of artifacts or noise} - G06T 5/50: using two or more images, e.g. averaging or subtraction - G06T 5/70: Denoising; Smoothing - G06T 5/92: based on global image properties - H04N 23/30: for generating image signals from X-rays - H04N 25/63: applied to dark current - H04N 25/67: applied to fixed-pattern noise, e.g. non-uniformity of response - A61B 6/487: {involving fluoroscopy} - G06T 2207/10116: X-ray image - G06T 2207/20224: Image subtraction - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An image processing apparatus includes: a dark correction unit configured to obtain a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; an addition value obtaining unit configured to analyze pixel values included in a plurality of dark corrected images and, based on an analysis result of the pixel values including a negative pixel value, obtain an addition value used to correct the negative pixel value; and an adding unit configured to add the addition value to the pixel values of the dark corrected image. ## Claims ### Claim 1 An image processing apparatus comprising: a dark correction unit configured to obtain a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; an addition value obtaining unit configured to analyze pixel values included in a plurality of dark corrected images and, based on an analysis result of the pixel values including a negative pixel value, obtain an addition value used to correct the negative pixel value; and an adding unit configured to add the addition value to the pixel values of the dark corrected image. ### Claim 2 (depends on 1) The apparatus according to claim 1, further comprising an evaluation value obtaining unit configured to analyze the pixel values included in the plurality of dark corrected images and obtain the analysis result of the pixel values including the negative pixel value as an evaluation value, wherein the addition value obtaining unit obtains the addition value used to correct the negative pixel value based on a variation in the evaluation value caused by an elapse of time. ### Claim 3 (depends on 2) The apparatus according to claim 2, wherein the addition value obtaining unit obtains, as the variation in the evaluation value caused by the elapse of time, a difference between an evaluation value of a current frame as a processing target and an addition value of a preceding frame to the current frame, and obtains the addition value of the current frame based on a result of determining whether an absolute value of the difference exceeds a threshold. ### Claim 4 (depends on 3) The apparatus according to claim 3, wherein if the absolute value of the difference between the evaluation value of the current frame and the addition value of the preceding frame to the current frame is not less than the threshold, and the difference between the evaluation value of the current frame and the addition value of the preceding frame is a negative value smaller than 0, the addition value obtaining unit corrects the evaluation value of the current frame based on a value obtained by subtracting the threshold from the addition value of the preceding frame. ### Claim 5 (depends on 3) The apparatus according to claim 3, wherein if the absolute value of the difference between the evaluation value of the current frame and the addition value of the preceding frame to the current frame is not less than the threshold, and the difference between the evaluation value of the current frame and the addition value of the preceding frame is not less than 0, the addition value obtaining unit corrects the evaluation value of the current frame based on a value obtained by adding the threshold to the addition value of the preceding frame. ### Claim 6 (depends on 4) The apparatus according to claim 4, wherein if the absolute value of the difference does not exceed the threshold, the addition value obtaining unit obtains the addition value of the current frame based on the addition value of the preceding frame and the evaluation value of the current frame, and if the absolute value of the difference is not less than the threshold, the addition value obtaining unit obtains the addition value of the current frame based on the addition value of the preceding frame and the corrected evaluation value. ### Claim 7 (depends on 2) The apparatus according to claim 2, wherein the evaluation value obtaining unit analyzes the pixel values included in the dark corrected image, and obtains an analysis result of a predetermined ratio of pixel values including a negative pixel value as the evaluation value, and the addition value obtaining unit obtains the addition value used to correct the negative pixel value based on a result of determining whether the variation in the evaluation value caused by the elapse of time exceeds a threshold. ### Claim 8 An image processing apparatus comprising: a dark correction unit configured to obtain a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; an evaluation value obtaining unit configured to analyze pixel values included in the dark corrected image and obtain an analysis result of the pixel values including a negative pixel value as an evaluation value; a statistic information obtaining unit configured to obtain statistic information based on a plurality of evaluation values obtained along with an elapse of time; an addition value obtaining unit configured to obtain an addition value used to correct the negative pixel value based on a variation in the evaluation values with respect to the statistic information; and an adding unit configured to add the addition value to the pixel values of the dark corrected image. ### Claim 9 (depends on 8) The apparatus according to claim 8, wherein the evaluation value obtaining unit generates a histogram of pixel values for the dark corrected image if the pixel values of the dark corrected image include a negative pixel value smaller than 0, obtains pixel values of points corresponding to a predetermined ratio from a lower side of the histogram, and obtains the evaluation value based on a result of determining whether the obtained pixel value is a negative value smaller than 0. ### Claim 10 (depends on 9) The apparatus according to claim 9, wherein the evaluation value obtaining unit generates the histogram after excluding, from all pixels of a detection unit configured to detect radiation, pixel values in a region where the radiation is blocked. ### Claim 11 (depends on 9) The apparatus according to claim 9, wherein the evaluation value obtaining unit multiplies the total number of pixels of the detection unit configured to detect the radiation by the predetermined ratio, and specifies the pixel values of the points corresponding to the predetermined ratio. ### Claim 12 (depends on 9) The apparatus according to claim 9, wherein if the obtained pixel value is smaller than 0 based on a determination result, the evaluation value obtaining unit obtains an absolute value of the pixel value as the evaluation value. ### Claim 13 (depends on 9) The apparatus according to claim 9, wherein if the obtained pixel value is not less than 0 based on the determination result, the evaluation value obtaining unit obtains the evaluation value set to 0. ### Claim 14 (depends on 9) The apparatus according to claim 9, wherein if the negative pixel value is not included in the dark corrected image, the evaluation value obtaining unit obtains the evaluation value set to 0. ### Claim 15 (depends on 8) The apparatus according to claim 8, wherein the evaluation value obtaining unit analyzes the pixel values included in the dark corrected image, and obtains the analysis result of the predetermined ratio of the pixel values including the negative pixel value as the evaluation value, and the addition value obtaining unit obtains the addition value used to correct the negative pixel value based on a result of determining whether the variation in the evaluation values with respect to the statistic information exceeds the threshold. ### Claim 16 (depends on 15) The apparatus according to claim 15, wherein if the variation in the evaluation values with respect to the statistic information does not exceed the threshold based on the determination result, the addition value obtaining unit obtains, as the addition value, the evaluation value obtained by the evaluation value obtaining unit. ### Claim 17 (depends on 15) The apparatus according to claim 15, wherein if the variation in the evaluation values with respect to the statistic information is not less than the threshold based on the determination result, the addition value obtaining unit obtains, as the addition value, the statistic information obtained by the statistic information obtaining unit. ### Claim 18 (depends on 15) The apparatus according to claim 15, wherein the statistic information obtaining unit obtains, as the statistic information, an average value based on evaluation values of a plurality of frames captured in the past and a standard deviation based on the evaluation values, and obtains the threshold based on the standard deviation, and the addition value obtaining unit obtains the addition value used to correct the negative pixel value based on a result of determining whether an absolute value of a difference between the average value and an evaluation value of a current frame as a processing target exceeds the threshold. ### Claim 19 A radiation imaging apparatus comprising: a radiation generator configured to generate radiation; a detection unit configured to detect the radiation; and an image processing apparatus configured to process image data detected by the detection unit, the image processing apparatus comprising: a dark correction unit configured to obtain a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; an addition value obtaining unit configured to analyze pixel values included in a plurality of dark corrected images and, based on an analysis result of the pixel values including a negative pixel value, obtain an addition value used to correct the negative pixel value; and an adding unit configured to add the addition value to the pixel values of the dark corrected image. ### Claim 20 An image processing method comprising: obtaining a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; analyzing pixel values included in a plurality of dark corrected images and, based on an analysis result of the pixel values including a negative pixel value, obtaining an addition value used to correct the negative pixel value; and adding the addition value to the pixel values of the dark corrected image. ### Claim 21 An image processing method comprising: obtaining a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; analyzing pixel values included in the dark corrected image and obtaining an analysis result of the pixel values including a negative pixel value as an evaluation value; obtaining statistic information based on a plurality of evaluation values obtained along with an elapse of time; obtaining an addition value used to correct the negative pixel value based on a variation in the evaluation values with respect to the statistic information; and adding the addition value to the pixel values of the dark corrected image. ### Claim 22 A computer-readable storage medium storing a program that causes a computer to function as each unit of an image processing apparatus, the image processing apparatus comprising: a dark correction unit configured to obtain a dark corrected image by removing a dark image obtained in a state without radiation irradiation from an object image obtained by radiation irradiation; an addition value obtaining unit configured to analyze pixel values included in a plurality of dark corrected images and, based on an analysis result of the pixel values including a negative pixel value, obtain an addition value used to correct the negative pixel value; and an adding unit configured to add the addition value to the pixel values of the dark corrected image.