Methods and apparatus for artifact reduction

• US 7,415,145 B2
• Filed: 12/30/2003
• Issued: 08/19/2008
• Est. Priority Date: 12/30/2003
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hsieh, Jiang, Fox, Stanley Haim
• Primary Examiner(s): Ahmed; Samir A.
• Assistant Examiner(s): BLOOM, NATHAN J
• Application Number:
  US10/749,033
• Publication Number:
  US 20050147320A1
• Time in Patent Office: 1,694 Days
• Field of Search: 382131-132, 382/154, 382/275, 382/261
• US Class Current: 382/131
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: G06T 2207/10081 Computed x-ray tomography [CT]
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06V 10/30 Noise filtering
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A method for facilitating a reduction in image artifacts is provided. The method includes receiving data regarding a scan of an object, reconstructing a plurality of images using the received data to form a three-dimensional image space, determining an orientation for a maximum intensity pixel operation, locating the maximum intensity pixels within a plurality of ray paths in accordance with the determined orientation, and filtering around each maximum intensity pixel along each ray path.

Claims

1. A method for facilitating a reduction in image artifacts, said method comprising:

receiving data regarding a scan of an object;

reconstructing a plurality of images using the received data to form a three-dimensional image space;

calculating a horizontal projection of the image by summing the reconstructed images in the horizontal direction;

calculating a vertical projection of the image by summing the reconstructed images in the vertical direction;

calculating an aspect ratio by taking a ratio of an intensity of the horizontal projection and the vertical projection; and

filtering based on the aspect ratio.

2. A method in accordance with claim 1 wherein said calculating an aspect ratio comprises calculating the ratio of the intensity of the horizontal projection over the vertical projection.

3. A method in accordance with claim 2 wherein said calculating the ratio of the intensity of the horizontal projection over the vertical projection comprises locating and averaging a plurality of maximum projection samples.

4. A method in accordance with claim 1 further comprising determining a scaling function using

$s$

( t ) = { 1 , t ≥

t h t - t l t h - t l , t l ≤

t <

t h 0 t <

t l

where;

t is the total mass in the reconstructed image calculated by at least one of the horizontal projection and the vertical projection; and

t_h and t_l are parameters.

5. A method in accordance with claim 1 further comprises determining a smoothed image from the reconstructed image.

6. A method in accordance with claim 1 further comprises determining a final image using

$I^{\prime }$

⁡

( x , y ) = k ·

r ·

s ⁡

( t ) ·

F ⁡

( x , y ) + [ 1 - k ·

r ·

s ⁡

( t ) ] ⁢

I ⁡

( x , y )

where;

k is a scaling factor;

r is an aspect ratio;

s(t) is the scaling function;

F(x,y) is a smoothed image;

I(x,y) is a reconstructed image; and

I′

(x,y) is a final image, the final image is the weighted sum of the original image with the filtered image.

7. An imaging system comprising:

a radiation source;

a radiation detector; and

a computer operationally coupled to said radiation source and said detector, said computer configured to;

receive data regarding a scan of an object;

reconstruct a plurality of images using the received data to form a three-dimensional image space;

calculating a horizontal projection of the image by summing the reconstructed images in the horizontal direction;

calculating a vertical projection of the image by summing the reconstructed images in the vertical direction;

calculate an aspect ratio by taking a ratio of an intensity of the horizontal projection and the vertical projection; and

filter based on the aspect ratio.

8. An imaging system in accordance with claim 7 wherein to calculate an aspect ratio said computer is further configured to calculate the ratio of the intensity of the horizontal projection over the vertical projection.

9. An imaging system in accordance with claim 7 wherein to calculate the ratio of the intensity of the horizontal projection over the vertical projection said computer is further configured to locate and to average a plurality of maximum projection samples.

10. An imaging system in accordance with claim 7 wherein said computer is further configured to determine a scaling function using

$s$

( t ) = { 1 , t ≥

t h t - t l t h - t l , t l ≤

t <

t h 0 t <

t l

where;

t is the total mass in the reconstructed image calculated by at least one of the horizontal projection and the vertical projection; and

t_h and t_l are parameters.

11. An imaging system in accordance with claim 7 wherein said computer is further configured to determine a smoothed image from the reconstructed image.

12. An imaging system in accordance with claim 7 wherein said computer is further configured to determine a final image using

$I^{\prime }$

⁡

( x , y ) = k ·

r ·

s ⁡

( t ) ·

F ⁡

( x , y ) + [ 1 - k ·

r ·

s ⁡

( t ) ] ⁢

I ⁡

( x , y )

where;

k is a scaling factor;

r is an aspect ratio;

s(t) is a scaling function;

F(x,y) is a smoothed image;

I(x,y) is a reconstructed image; and

I′

(x,y) is a final image, wherein the final image is the weighted sum of the original image with the filtered image.

13. A computer readable storage medium encoded with a program configured to instruct a computer to:

receive data regarding a scan of an object;

reconstruct a plurality of images using the received data to form a three-dimensional image space;

calculate a horizontal projection of the image by summing the reconstructed images in the horizontal direction;

calculate a vertical projection of the image by summing the reconstructed images in the vertical direction;

calculate an aspect ratio by taking a ratio of an intensity of the horizontal projection and the vertical projection; and

filter based on the aspect ratio.

14. A computer readable medium in accordance with claim 13 wherein to calculate an aspect ratio said program is further configured to calculate the ratio of the intensity of the horizontal projection over the vertical projection.

15. A computer readable medium in accordance with claim 13 wherein to calculate the ratio of the intensity of the horizontal projection over the vertical projection said program is further configured to locate and to average a plurality of maximum projection samples.

16. A computer readable medium in accordance with claim 13 wherein said program is further configured to determine a scaling function using

$s$

( t ) = { 1 , t ≥

t h t - t l t h - t l , t l ≤

t <

t h 0 t <

t l

where;

t is the total mass in the reconstructed image calculated by at least one of the horizontal projection and the vertical projection; and

t_h and t_l are parameters.

17. A computer readable medium in accordance with claim 13 wherein said program is further configured to determine a smoothed image from the reconstructed image.

18. A computer readable medium in accordance with claim 13 wherein said program is further configured to determine a final image using

$I^{\prime }$

⁡

( x , y ) = k ·

r ·

s ⁡

( t ) ·

F ⁡

( x , y ) + [ 1 - k ·

r ·

s ⁡

( t ) ] ⁢

I ⁡

( x , y )

where;

k is a scaling factor;

r is an aspect ratio;

s(t) is the scaling function;

F(x,y) is a smoothed image;

I(x,y) is a reconstructed image; and

I′

(x,y) is a final image, the final image is the weighted sum of the original image with the filtered image.