APPARATUS AND METHOD FOR CONTEXT-ORIENTED BLENDING OF RECONSTRUCTED IMAGES

• US 20190236763A1
• Filed: 01/30/2018
• Published: 08/01/2019
• Est. Priority Date: 01/30/2018
• Status: Active Grant

• Current Assignee: Canon Medical Systems Corporation (Canon Inc.)
• Original Assignee: Canon Medical Systems Corporation (Canon Inc.)
• Inventors: Chan, Chung, Yu, Zhou, Zhou, Jian
• Granted Patent: US 10,643,319 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/463 characterised by displaying multiple images or images and diagnostic data on one display
• CPC Class Codes: A61B 6/5235 combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
• CPC Class Codes: A61B 6/5258 involving detection or reduction of artifacts or noise
• CPC Class Codes: G06T 11/006 Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
• CPC Class Codes: G06T 11/008 Specific post-processing after tomographic reconstruction, e.g. voxelisation, metal artifact correction
• CPC Class Codes: G06T 2207/10081 Computed x-ray tomography [CT]
• CPC Class Codes: G06T 2207/20216 Image averaging
• CPC Class Codes: G06T 2207/30016 Brain
• CPC Class Codes: G06T 2207/30061 Lung
• CPC Class Codes: G06T 2210/41 Medical
• CPC Class Codes: G06T 2211/424 Iterative
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/70 Denoising; Smoothing

Abstract

A method and apparatus is provided generate a display image that optimize a tradeoff between resolution and noise by using blending weights/ratio based on the content/context of the image. The blending weights control the relative weights when combining multiple computed tomography (CT) images having different degrees of smoothing/denoising to generate a display image having the optimal tradeoff lying within the continuum between/among the CT images. The blending weights are automated based on information indicating the content/context of the display image (e.g., the segmented tissue type, average attenuation, and the display setting such as window width and window level). Thus, indicia indicating content/context of the image determine the weighting coefficients, which are used in a weighted sum, e.g., to combine the plurality of images with different noise/smoothing parameters into a single blended image, which is displayed.

Claims

1. An apparatus, comprising:

circuitry configured to

obtain a plurality of images representing respective computed tomography (CT) reconstructed images with different degrees of denoising,

receive one or more indicia indicating content and/or context of a display image to be displayed on a display,

determine weighting coefficients based on the one or more indicia, combine the plurality of images using the weighting coefficients to generate a blended image, and

control a display to display the blended image as the display image.

2. The apparatus according to claim 1, wherein the circuitry is further configured to obtain the plurality of images having the respective denoising parameters by

reconstructing each of the plurality of images by optimizing respective cost functions, each cost function having a data fidelity term and a product between a regularization parameter and a regularization term, wherein

the regularization parameter is used to parametrize the different degrees of denoising of the respective images of the plurality of images.

3. The apparatus according to claim 1, wherein the circuitry is further configured to determine the weighting coefficients by

receiving an instruction to display the display image according to one or more display parameters, the one or more indicia including the one or more display parameters, and

determining the weighting coefficients based on the one or more display parameters.

4. The apparatus according to claim 1, wherein the circuitry is further configured to combine the plurality of images using the weighting coefficients by

summing, as a weighted summation, multiplication products of respective images of the plurality of images, respectively, with corresponding weighting coefficients of the weighting coefficients.

5. The apparatus according to claim 3, wherein the circuitry is further configured to determine the weighting coefficients based on the one or more indicia, wherein the on the one or more indicia include at least one of a window width of attenuation values to be displayed and a slice thickness of the display image.

6. The apparatus according to claim 5, wherein the circuitry is further configured to determine the weighting coefficients between a first image of the plurality of images and a second image of the plurality of images, for which the first image is denoised more than the second image, the weighting coefficients being determined such that, for relative contributions to the blended image of the first and second images,

a contribution of the first image relative is increased relative to a contribution of the second image, when the window width becomes narrower,

the contribution of the first image is increased relative to the contribution of the second image, when the slice thickness becomes thinner,

the contribution of the second image is increased relative to the contribution of the first image, when the window width becomes wider, and

the contribution of the second image is increased relative to the contribution of the first image, when the slice thickness becomes thicker.

7. The apparatus according to claim 1, wherein the circuitry is further configured to

determine the weighting coefficients to be functions of a position, the position being a position within the blended image, and the weighting coefficients being determined by

obtaining, using the one or more indicia, a spatially dependent parameter, which is a function of the position,

mapping, for each of the positions within the blended image, a respective value of the spatially dependent parameter at a position to the weighting coefficients at the position based on one or more predefined functions to generate a weighting coefficients map, and

combine the plurality of images using the weighting coefficients map by

determining, for each of the positions in the blended image, a value of attenuation at a position in the blended image using the corresponding weighting coefficients of the weighting coefficients map at the position.

8. The apparatus according to claim 1, wherein the circuitry is further configured to determine the weighting coefficients so that:

when the one or more indicia indicate a brain trauma application, the weighting coefficients adjust a relative contribution to the blended image from images of the plurality of images to realize more smoothing and less noise in a soft-tissue region and to less smoothing and more noise in a bone region,

when the one or more indicia indicate a lung imaging application, a first image of the plurality of images is generated to have a high-resolution and the weighting coefficients adjust the relative contribution to the blended image to be predominantly the first image in a lung region and in a soft-tissue region the relative contribution to the blended image realizes more smoothing and less resolution than in the lung region,

when the one or more indicia indicate an angiography application, the weighting coefficients adjust the relative contribution to the blended image to realize less smoothing and more noise in a contrast-agent region and more smoothing and less noise elsewhere, and

when the one or more indicia indicate a contrast-enhanced application, the weighting coefficients adjust the relative contribution to the blended image to realize less smoothing and more noise in a contrast-enhanced region and more smoothing and less noise elsewhere.

9. The apparatus according to claim 1, wherein the circuitry is further configured to determine the weighting coefficients, wherein the weighting coefficients are a blending map in which a value of the weighting coefficients depends on a position in the blended image, such that for each position in the blended image the weighting coefficients sum to a predefined constant, and values of the blending map are determined by one of

averaging attenuation values in a neighborhood of one or more images of the plurality of images corresponding to a position in the blended image to generate an average attenuation, and applying a first function to the generated average attenuation to generate a value of the blending map corresponding to the position in the blended image, and

segmenting one or more images of the plurality of images into regions according to a plurality of region types, and applying a predefined lookup table to assign values to the blending map according to a respective region type corresponding to the position in the blended image.

10. The apparatus according to claim 1, wherein the circuitry is further configured to determine the weighting coefficients, wherein the plurality of region types include two or more of a lung type, an air type, an adipose type, a water type, a muscle type, a soft-tissue type, a cancellous-bone type, a cortical-bone type, a brain-tissue type, and a bone type.

11. The apparatus according to claim 1, wherein the circuitry is further configured to determine the weighting coefficients using a first function relating an attenuation value to a value of the weighting coefficients, such that:

for large attenuation values, the first function outputs weighting coefficients that increase a relative contribution of a first image of the plurality of images that has less smoothing,

for medium attenuation values, the first function outputs weighting coefficients that increase a relative contribution of a second image of the plurality of images that has more smoothing,

for small attenuation values, the first function outputs weighting coefficients that increase the relative contribution of the first image, wherein

the large attenuation values are greater than the medium attenuation values, which are greater than the small attenuation values,

the first image has finer resolution and more noise than the second image, and

a relative contribution represents a percentage of the blended image corresponding to an image of the plurality of images.

12. The apparatus according to claim 1, wherein the circuitry is further configured to obtain the plurality of images having the different degrees of denoising by one or more of

generating the plurality of images using iterative reconstruction to minimize a cost function including a regularization term multiplied by a first constant, and the respective images of the plurality of images are generated using different values for the first constant,

applying a post-reconstruction denoising method parameterized by a second constant to a reconstructed image, wherein the plurality of images are generated by noising the reconstructed image using different values for the second constant, and

applying a pre-reconstruction denoising method parameterized by a third constant to a sinogram, wherein the plurality of images are reconstructed from a plurality of denoised sinograms, which are generated by denoising the sinogram using different values for the third constant.

13. The apparatus according to claim 1, wherein the circuitry is further configured to receive the one or more indicia, wherein the one or more indicia include one or more of a display setting of window width of a displayed attenuation, a display setting of window level of the displayed attenuation, a display setting of slice thickness, information of a clinical application, information of an imaged body part, and information of a patient.

14. The apparatus according to claim 9, wherein the circuitry is further configured to determine the weighting coefficients, so that the blending map is further based on information of a material decomposition.

15. A computed tomography (CT) scanner, comprising:

an X-ray source configured to emit X-rays;

a detector configured to receive the X-rays at a plurality of detector elements and generate projection data representing an intensity of the X-rays at the plurality of detector elements; and

circuitry configured to

generate a plurality of images representing respective CT images reconstructed images from the projection data, each of the plurality of images having a different degree of denoising with respect to others of the plurality of images,

receive one or more indicia indicating content and/or context of a display image to be displayed on a display,

determine weighting coefficients based on the one or more indicia,

combine the plurality of images using the weighting coefficients to generate a blended image, and

control a display to display the blended image as the display image.

16. A method, comprising:

obtaining a plurality of images representing respective computed tomography (CT) reconstructed images with different degrees of denoising,

receiving one or more indicia indicating content and/or context of a display image to be displayed on a display,

determining weighting coefficients based on the one or more indicia,

combining the plurality of images using the weighting coefficients to generate a blended image, and

controlling a display to display the blended image as the display image.

17. The method according to claim 16, wherein the determining of the weighting coefficients further includes

representing the weighting coefficients as a blending map in which a value of the weighting coefficients depends on position in the blended image such that for each position in the blended image the weighting coefficients sum to a predefined constant, and values of the blending map are determined by one of

averaging attenuation values in a neighborhoods of one or more images of the plurality of images corresponding to a position in the blended image to generate an average attenuation, and applying a first function to the generated average attenuation to generate a value of the blending map corresponding to the position in the blended image, and

segmenting one or more images of the plurality of images into regions according to a plurality of region types, and applying a predefined lookup table to assign values to the blending map according to a respective region type corresponding to the position in the blended image.

18. The method according to claim 16, further comprising

receiving an instruction to display the display image according to one or more display parameters, the one or more display parameters being included in the one or more indicia, and

the determining of the weighting coefficients based on the one or more indicia further includes that the weighting coefficients are based on the one or more display parameters, wherein the one or more display parameters includes at least one of a window width of attenuation values of the display image and a slice thickness of the display image,

the weighting coefficients change to increase a contribution to the blended image of a first image of the plurality of images relative to a contribution to the blended image of a second image of the plurality of images, when the slice thickness decreases or when the window width decreases, the first image being denoised more than the second image, and

the weighting coefficients change to increase the contribution to the blended image of the second image relative to the contribution to the blended image of the second image when the slice thickness increases or when the window width increases.

19. The method according to claim 16, wherein

the determining of the weighting coefficients further includes that the weighting coefficients are functions of a position, the position being a position within the blended image, the weighting coefficients being determined by

obtaining, using the one or more indicia, a spatially dependent parameter, which is a function of the position,

mapping, for each of the positions within the blended image, a respective value of the spatially dependent parameter at a position to the weighting coefficients at the position based on one or more predefined functions to generate a weighting coefficients map, and

the combining of the plurality of images using the weighting coefficients is performed by determining, for each of the positions in the blended image, a value of attenuation at a position in the blended image using the corresponding weighting coefficients of the weighting coefficients map at the position.

20. A non-transitory computer readable storage medium including executable instruction, wherein the instructions, when executed by circuitry, cause the circuitry to perform the method according to claim 16.