Method and apparatus of scoring an arterial obstruction

• US 6,996,262 B2
• Filed: 05/20/2002
• Issued: 02/07/2006
• Est. Priority Date: 05/20/2002
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Li, Jianying
• Primary Examiner(s): Miriam, Daniel
• Assistant Examiner(s): Mistry, ONeal R.
• Application Number:
  US10/151,510
• Publication Number:
  US 20030215124A1
• Time in Patent Office: 1,359 Days
• Field of Search: 382/128, 382/130, 382/154, 600/485, 600/486, 600/407
• US Class Current: 382/131
• CPC Class Codes: G06T 2207/30101 Blood vessel; Artery; Vein; Vascular
• CPC Class Codes: G06T 7/0012 Biomedical image inspection
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes

Abstract

The present invention is directed to a method and apparatus of scoring an arterial obstruction. The present invention includes identifying a particular group of pixels corresponding to a calcified region of coronary artery of a patient and based on the satisfaction of a number of thresholds connectivity criteria, determining a calcification score of that calcified region as indicative of the patient'"'"'s risk of cardiovascular disease including atherosclerosis, heart attack, heart failure, and stroke. The present invention further includes determining the scaling factor unique to a particular imaging slice of data to provide a value of calcium weight and volume that is indicative of the true obstruction and true volume of the calcified region.

Claims

1. A method of scoring an arterial obstruction comprising the steps of:

acquiring images for a number of slices of a subject;

determining a set of the images corresponding to an arterial obstruction that contains calcium;

determining a slice thickness for each image of the set;

determining an area of the arterial obstruction on each image;

determining a product of the slice thickness of each image and the area of the arterial obstruction of each image;

modifying each product by a scaling factor;

summing the modified products for the set of images; and

determining a characteristic of the arterial obstruction therefrom.

2. The method of claim 1 further comprising the step of determining a volume of the arterial obstruction.

3. The method of claim 1 further comprising the step of modifying each product by an effective density of each image and summing the modified products and determining a weight of the arterial obstruction therefrom.

4. The method of claim 3 further comprising the step of determining the effective density of each image from a calibration curve.

5. The method of claim 4 further comprising the step of determining the effective density of each image by determining a relationship between obstruction density and mean CT number of the calcium.

6. The method of claim 1 wherein the scaling factor for each image includes a ratio of maximum CT number for the arterial obstruction on cach image and maximum CT number for the arterial obstruction on all images.

7. The method of claim 1 wherein the arterial obstruction includes a region of calcium in a coronary artery of the subject.

8. A method of coronary artery calcification scoring comprising the steps of:

(A) acquiring imaging data for a number of imaging slices of a patient;

(B) identifying a set of pixels of the imaging data corresponding to calcium in a coronary artery of the patient;

(C) determining an area of the calcium in each imaging slice;

(D) determining a subset of pixels to be considered for calcification scoring;

(E) determining a thickness of each imaging slice;

(F) modifying the area of the calcium of each imaging slice by a corresponding slice thickness and determining a volume of the calcium in each imaging slice therefrom;

(G) modifying each volume by a corresponding calibration factor for each imaging slice; and

(H) summing the modified volumes to determine a total volume of the calcium in the coronary artery of the patient.

9. The method of claim 8 wherein the imaging data is CT imaging data and further comprising the steps of:

determining a maximum CT number for the subset of pixels;

determining a maximum CT number for each imaging slice; and

determining the corresponding calibration factor for each imaging slice from the maximum CT number for the subset of pixels and the maximum CT number for each imaging slice.

10. The method of claim 9 wherein the calibration factor for each imaging slice includes a ratio of the maximum CT number for the subset of pixels and the maximum CT number for each imaging slice.

11. The method of claim 10 wherein the ratio includes $\frac{I_{{\max }_i}}{G_{\max }};$

where I_maxi equals the maximum CT number of the calcium for an imaging slice and G_max equals the maximum CT number of the calcium for the subset of pixels.

12. The method of claim 11 wherein $V=\sum _{}$

i⁢

ImaxiGmax⁢

⁢

Ai⁢

St;

where;

V equals the total volume of the calcium;

i represents a particular imaging slice;

I_maxi equals the maximum CT number of the calcium for an imaging slice;

G_max equals the maximum CT number of the calcium for the subset of pixel;

A_i equals the area of the calcium of an imaging slice; and

S_t equals the slice thickness of an imaging slice.

13. The method of claim 8 further comprising the step of determining an area threshold for the calcium and determining if the area of the calcium for each imaging slice exceeds a pre-determined area threshold and, if so, adjusting the area threshold.

14. The method of claim 13 further comprising the step of repeating steps (C)–

(H) if the area of the calcium for each imaging slice exceeds the pre-determined area threshold.

15. The method of claim 8 further comprising the step of determining mean CT numbers for the calcium identified by the set of pixels and determining an effective density of each imaging slice from a calibration curve.

16. The method of claim 15 wherein the step of modifying the volumes includes the step of modifying each volume by a corresponding effective density D_i.

17. The method of claim 16 wherein:

$W=\underset{i}{\sum <br><br>}<br><br>\frac{I_{{\max }_i}}{G_{\max }}·<br><br>A_i·<br><br>D_i·<br><br>S_t;<br><br>$

where;

W equals a total weight of the calcium;

i represents a particular imaging slice;

I_maxi equals the maximum CT number of the calcium for an imaging slice;

G_max equals the maximum CT number of the calcium for the subset of pixels;

A_i equals the area of calcium of an imaging slice;

S_t equals the slice thickness of an imaging slice; and

D_i equals an effective density of calcium in an imaging slice.

18. The method of claim 15 wherein the calibration curve represents a relationship between effective calcium density and mean CT number of the calcium.

19. A computer readable storage medium having a computer program stored thereon and representing a set of instructions that when executed by a computer causes the computer to:

initiate a multi-slice scan of a subject;

acquire imaging data of the subject for a number of imaging slices;

determine a portion of the imaging data corresponding to calcium;

determine a maximum CT number of the portion;

determine a maximum CT number for calcium in each imaging slice;

determine a scaling factor for each imaging slice from the maximum CT number for calcium in each imaging slice and the maximum CT number of the portion;

determine an area of the calcium in each imaging slice;

modify each area by a corresponding slice thickness; and

determine a weighted sum of each imaging area modified by the corresponding slice thickness and the quantification factor.

20. The computer readable storage medium of claim 19 wherein the set of instructions further causes the computer to determine an effective density of the calcium of each imaging slice.

21. The computer readable storage medium of claim 20 wherein the set of instructions to determine a weighted sum includes instructions to modify each imaging area by a corresponding slice thickness, the scaling factor, and the effective density.

22. The computer readable storage medium of claim 20 wherein the set of instructions further causes the computer to determine the effective density from a calibration curve stored as a look-up table in memory of an imaging apparatus used to acquire the imaging data.

23. The computer readable storage medium of claim 20 wherein the set of instructions further causes the computer to determine a mean CT number of the calcium of each imaging slice.

24. A radiation emitting imaging apparatus for acquiring imaging data of a subject and for determining a calcification score from the imaging data, the radiation emitting imaging apparatus comprising;

a rotatable gantry having an opening therein to receive a subject to be scanned;

an HF electromagnetic energy source configured to project HF electromagnetic energy toward the subject;

a detector assembly configured to detect HF electromagnetic energy attenuated by the subject;

a data acquisition system connected to the detector assembly and configured to receive electrical signals from the detector assembly indicative of the HF electromagnetic energy detected; and

a computer programmed to;

generate a set of imaging data from die electrical signals;

arrange the imaging data to correspond to a number of imaging slices, each imaging slice having a slice thickness;

determining a portion of the imaging data corresponding to calcium;

determine a maximum CT number of the calcium;

determine a maximum CT number of the calcium in each imaging slice;

determine an area of the calcium in each imaging slice;

modify each area by a slice thickness and a ratio of the maximum CT number of the calcium for a corresponding imaging slice and the maximum CT number of the calcium; and

sum each modified area to determine a calcification score.

25. The radiation emitting imaging apparatus of claim 24 wherein the calcification score includes a volume of the calcium.

26. The radiation emitting imaging apparatus of claim 24 further comprising a look-up table and wherein the computer is further programmed to determine a mean CT number of the calcium in cach imaging slice and determine an effective density of the calcium in each imaging slice from the mean CT number and data stored on the look-up table.

27. The radiation emitting imaging apparatus of claim 25 wherein the computer is further programmed to modify each area by a slice thickness, an effective density, and a ratio of a corresponding maximum CT number for calcium and the maximum CT number of the calcium for cach imaging slice to determine a obstruction of the calcium.

28. A CT imaging system comprising:

means for acquiring imaging data of a coronary artery of a subject, the imaging data corresponding to a number of imaging slices;

means for isolating a portion of the imaging data corresponding to a calcium obstruction in the coronary artery;

means for determining a thickness of each imaging slice;

means for determining an area of the calcium obstruction in each imaging slice;

means for determining a maximum CT number of the calcium obstruction in each imaging slice;

means for determining a maximum CT number of the calcium obstruction;

means for weighting a product of the area of the calcium in each imaging slice and the thickness of each imaging slice by a ratio of the maximum CT number of the calcium obstruction in each imaging slice and the maximum CT number of the calcium obstruction; and

means for summing the weighted products.

29. A method of scoring an arterial obstruction comprising the steps of:

acquiring images for a number of slices of a subject;

determining a set of the images corresponding to an arterial obstruction;

determining a slice thickness for each image of the set;

determining an area of the arterial obstruction on each image;

determining an effective density of each image from a calibration curve by determining a relationship between arterial obstruction density and mean CT number of calcium;

determining a product of the slice thickness of each image and the area of the arterial obstruction of each image;

modifying each product by a sealing factor that includes modifying each product by the effective density of each image;

summing the modified products for the set of images; and

determining a characteristic of the arterial obstruction therefrom, wherein the characteristic includes a weight of the arterial obstruction.