Methods and apparatus for calcification scoring

• US 6,233,304 B1
• Filed: 11/25/1998
• Issued: 05/15/2001
• Est. Priority Date: 11/25/1998
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Buchanan, Robert A., Mitsa, Theophano, Hu, Hui
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/199,513
• Time in Patent Office: 902 Days
• Field of Search: 378/4, 378/8, 378/15, 378/37, 378/98, 378/98.2, 378/98.8
• US Class Current: 378/8
• CPC Class Codes: G06T 7/0012 Biomedical image inspection

Abstract

The present invention, in one form, is a method for generating a calcification score in a CT image data using a scoring algorithm. In accordance with one embodiment of the algorithm, a calcium score is determined by identifying a scorable region in the image data, defining at least one region of interest in the scorable region, and determining a density score. After determining a calcium score for each region of interest, a total calcium score is determined. In addition, to correct for unequal and/or non-contiguous spacing of the slices of image data, a weighted total calcium score is determined.

Claims

1. A method of determining coronary artery calcification in computed tomography image data, said method comprising the steps of:

collecting at least one slice of image data;

identifying at least one region of interest;

determining a density score for each region of interest; and

determining a calcification score using the density score,

wherein the density score, DS, for each region of interest is determined in accordance with;

$\mathrm{DS}=\{\begin{array}{cc}0& \text{If}<br><br>\text{\hspace{1em}<br><br>}<br><br>H_P\le <br><br>\left(\mathrm{LT}-1\right)\\ \left(S*H_P\right)-C& \text{If}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{LT}\le <br><br>H_P\le <br><br>\left(\mathrm{UT}-1\right)\\ \left(S*\mathrm{UT}\right)-C& \text{If}<br><br>\text{\hspace{1em}<br><br>}<br><br>H_P\ge <br><br>\mathrm{UT}\end{array}$

where;

H_P=a CT number of pixel P,

LT=an lower threshold number,

UT=an upper threshold number,

S=a scaling factor, and

C=a constant.

2. A method in accordance with claim 1 further comprising the step of identifying a scorable region prior to identifying at least one region of interest.

3. A method of determining coronary artery calcification in computed tomography image data, said method comprising the steps of:

collecting at least one slice of image data;

identifying at least one region of interest;

determining a density score for each region of interest;

determining a slice calcium score of each region of interest using the density score in accordance with;

${\mathrm{CS}}_R=A_P*\left(\underset{1}{\overset{P_R}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{DS}}_P\right);<br><br>\text{\hspace{1em}<br><br>}<br><br>\text{and}$

determining a total calcium score using each slice calcium score;

where;

CS_R=a calcium score of each region of interest,

A_P=an area of a pixel P,

P_R=a number of scalable pixels in the region of interest, and

DS_P=a density score of pixel P.

4. A method in accordance with claim 3 wherein determining the total calcium score comprises the step of determining a weighted total calcium score.

5. A method in accordance with claim 4 wherein determining the weighted total calcium score is in accordance with:

$\mathrm{TCS}=N*\left(\underset{1}{\overset{R}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{CS}}_R*F*G\right)\right)$

where;

N=a normalization factor,

F=a scale factor,

G=G₁+G₂,

G₁=a distance between a previous slice and a current slice,

G₂=a distance between the current slice and a subsequent slice,

R=a number of regions of interest.

6. A system for determining a level of calcification in image data, the image data from a tomographic scan, said system comprising an x-ray source and a detector array, said system configured to:

collect at least one slice of image data;

identify at least one region of interest;

determine a density score for each region of interest; and

determine a calcification score using said density score;

wherein said density score for each region of interest is determined in accordance with;

$\mathrm{DS}=\{\begin{array}{cc}0& \text{If}<br><br>\text{\hspace{1em}<br><br>}<br><br>H_P\le <br><br>\left(\mathrm{LT}-1\right)\\ \left(S*H_P\right)-C& \text{If}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{LT}\le <br><br>H_P\le <br><br>\left(\mathrm{UT}-1\right)\\ \left(S*\mathrm{UT}\right)-C& \text{If}<br><br>\text{\hspace{1em}<br><br>}<br><br>H_P\ge <br><br>\mathrm{UT}\end{array}$

where;

H_P=a CT number of pixel P,

LT=an lower threshold number,

UT=an upper threshold number,

S=a scaling factor, and

C=a constant.

7. A system in accordance with claim 6 further configured to identify a scorable region prior to identifying at least one region of interest.

8. A system in accordance with claim 6 wherein said detector array is a multislice detector array.

9. A system for determining a level of calcification in image data, the image data from a tomographic scan, said system comprising an x-ray source and a detector array, said system configured to:

collect at least one slice of image data;

identify at least one region of interest;

determine a density score for each region of interest;

determine a slice calcium score of each region of interest using said density score in accordance with;

${\mathrm{CS}}_R=A_P*\left(\underset{1}{\overset{P_R}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{DS}}_P\right);<br><br>\text{\hspace{1em}<br><br>}<br><br>\text{and}$

determine a total calcium score using each slice calcium score,

where;

CS_R=a calcium score of each region of interest,

A_P=an area of a pixel P,

P_R=a number of scalable pixels in the region of interest, and

DS_P=a density score of pixel P.

10. A system in accordance with claim 9 wherein to determine said total calcium score, said system is configured to determine a weighted total calcium score.

11. A system in accordance with claim 10 wherein said weighted total calcium score is determined in accordance with:

$\mathrm{TCS}=N*\left(\underset{1}{\overset{R}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{CS}}_R*F*G\right)\right)$

where;

N=a normalization factor,

F=a scale factor,

G=G₁+G₂,

G₁=a distance between a previous slice and a current slice,

G=a distance between a prior slice and a subsequent slice, and

R=a number of regions of interest.