Method for correcting for beam hardening in a CT image

• US 6,600,801 B2
• Filed: 10/17/2001
• Issued: 07/29/2003
• Est. Priority Date: 10/17/2000
• Status: Expired due to Term

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Raupach, Rainer
• Primary Examiner(s): ARANA, LOUIS M
• Application Number:
  US09/981,478
• Publication Number:
  US 20020097830A1
• Time in Patent Office: 650 Days
• Field of Search: 378/4, 378/5, 378/6, 378/7, 378/16, 378/901
• US Class Current: 378/4
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• 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 2211/424 Iterative
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A method for correcting for beam hardening in an initial CT image, which is composed of pixels arranged in a matrix, correction data are determined from the initial image by re-projection of the pixels from the initial image at a large number of projection angles, the pixels from the initial image being compared with a threshold value for each of the projection angles during the re-projection, and the re-projection being carried out for only those pixels from the initial image which have a pixel value above the threshold value. The correction data are used to determine a corrected image from the initial image.

Claims

1. A method for correcting for beam hardening in an initial CT image, composed of pixels arranged in a matrix, comprising the steps of:

obtaining correction data from said initial image by re-projecting the pixels therein at a plurality of projection angles using only pixels from said initial image for each projection angle having a pixel value above a threshold value; and

producing a corrected image from said initial image using said correction data.

2. A method as claimed in claim 1 wherein the pixels in said initial image having a pixel value above said threshold value are identified during said re-projection.

3. A method as claimed in claim 1 wherein the pixels in said initial image having a pixel value above said threshold value are determined before re-projecting said pixels, and comprising the steps of storing said pixels from said initial image having a pixel value above said threshold value, as stored pixels, and using said stored pixels for re-projection for each of said projection angles.

4. A method as claimed in claim 3 comprising storing said stored pixels in dataset which, for each of said stored pixels, contains coordinates of a center of each stored pixel and the pixel value of each stored pixel.

5. A method as claimed in claim 3 comprising storing said stored pixels in a data set which, for each of said stored pixels, contains a linear index and a pixel value.