Estimating visceral fat by dual-energy x-ray absorptiometry

• US 20060074288A1
• Filed: 10/04/2004
• Published: 04/06/2006
• Est. Priority Date: 10/04/2004
• Status: Active Grant

• Current Assignee: Hologic Incorporated
• Original Assignee: Hologic Incorporated
• Inventors: Kelly, Thomas, Ruth, Christopher, Wilson, Kevin E.
• Granted Patent: US 7,725,153 B2
• Time in Patent Office: Days
• US Class Current: 600/407
• CPC Class Codes: A61B 5/4869 Determining body composition
• CPC Class Codes: A61B 5/4872 Body fat
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/50 specially adapted for specific body parts; specially adapted for specific clinical applications
• CPC Class Codes: A61B 6/505 for diagnosis of bone

Abstract

A system and a method of using dual-energy absoptiometry to estimate visceral fat metrics and display results, preferably as related to normative data. The process involves deriving x-ray measurements for respective pixel positions related to a two-dimensional projection image of a body slice containing visceral fat as well as subcutaneous fat; at least some of the measurements being dual-energy x-ray measurements, processing the measurements to derive estimates of metrics related to the visceral fat in the slice; and using the resulting estimates.

Claims

1. A method of using dual-energy absorptiometry to estimate visceral fat comprising:

deriving x-ray measurements for respective pixel positions related to a two-dimensional projection image of a body slice containing visceral fat as well as subcutaneous fat;

wherein at least some of the measurements are dual-energy x-ray measurements;

processing the measurements to derive an estimate of the visceral fat; and

using the estimate of visceral fat.

2. A method as in claim 1 in which the processing comprises using the x-ray measurements to estimate lean tissue in the body slice, and using the estimates of fat and lean tissue to calculate a percentage visceral fat % Fat_v.

3. A method as in claim 1 in which the processing comprises using the x-ray measurements to estimate total fat and subcutaneous fat in the body slice and reducing the estimate of total fat to account for estimated subcutaneous fat in deriving the estimate of visceral fat.

4. A method as in claim 1 in which the processing step comprises using the x-ray measurements to estimate dimensions of the body slice and using the estimated dimensions to estimate subcutaneous and visceral fat in the body slice.

5. A method as in claim 1 in which the processing step comprises using the x-ray measurement to estimate (a) a major and a minor axis of an ellipse approximating the body slice, and (b) a portion of the major axis related to subcutaneous fat.

6. A method as in claim 1 in which the deriving step comprises deriving at least some of the measurement from an AP or a PA view of the body.

7. A method as in claim 6 in which the deriving step further comprises deriving at least some of the x-ray measurements from a lateral view of the body.

8. A method as in claim 6 in which the processing comprises using x-ray measurements derived from the lateral view to estimate a minor axis of an ellipse approximating the body slice.

9. A method as in claim 1 in which the processing step comprises using the x-ray measurements to estimate (a) an area at that approximates the area of the body slice matching a plane of propagation of x-rays used to derive the x-ray measurements, (b) an area α

_v that approximates the area of the portion of the body slice that contains visceral fat, (c) a total fat content M_t(Fat)of the body slice, (d) an area α

_s that approximates the area of subcutaneous fat in the body slice, and (d) visceral fat content Fat_v in the body slice approximated as Fat_v=(M_t(fat)−

α

_swρ

_s), where w is an estimate of a thickness of the body slice and ρ

_s is an estimate of density of fat.

10. A method as in claim 9 in which the processing comprises using the x-ray measurements to estimate a major and a minor axis of an ellipse that approximates the area of the body slice and using the axes to estimate the area α

_t.

11. A method as in claim 10 including using the x-ray measurements to estimate lean tissue in the body slice and using the estimates of fat and lean tissue to calculate a percentage metric for visceral fat content in the body slice.

12. A method as in claim 11 in which the processing step comprises deriving individual estimates of visceral fat for each of a number of the pixel positions in said projection image.

13. A method as in claim 12 in which the processing step uses information related to the individual estimates of visceral fat for a number of the pixel positions to estimate visceral fat pertaining to selected regions in the patient'"'"'s body.

14. A method as in claim 13 in which the processing step comprises using the x-ray measurements to estimate subcutaneous fat in x-ray paths from a source individually for a number of the pixel positions, and using the estimates for the paths in estimating visceral fat in said paths.

15. A method as in claim 14 in which the processing step comprises using the estimates of visceral fat along the paths to estimate visceral fat associated with individual organs of the patient.

25. A method as in claim 1 in which the processing step includes deriving visceral fat metrics and information regarding relationships of the metrics to comparable metrics for selected normative ranges, and the using step includes displaying said information regarding relationships.

16. A dual-energy x-ray absorptiometry system comprising:

a data acquisition unit comprising a source and a detector of x-rays, deriving x-ray measurements for respective pixel positions related to a two-dimensional projection image of a body slice containing visceral fat as well as subcutaneous fat, wherein at least some of the measurements are dual-energy x-ray measurements;

a computer processing unit processing the measurements to derive an estimate of the visceral fat; and

a user interface and results display controlling the data acquisition unit and using the estimate of visceral fat for display, storage, and/or further processing.

17. A system as in claim 16 in which the processing unit comprises programmed circuitry estimating (a) an area at that approximates the area of the body slice along a plane of propagation of x-rays used to derive the x-ray measurements, (b) an area α

_v that approximates the area of the portion of the body slice that contains visceral fat, (c) a total fat content Mt(Fat)of the body slice, (d) an area α

_s that approximates the area of subcutaneous fat in the body slice, and (d) visceral fat content Fat_v in the body slice approximated as Fat_v=(M_t(fat)−

α

_swρ

_s), where w is an estimate of a thickness of the body slice and ρ

_s is an estimate of density of fat.

18. A system as in claim 17 in which the processing unit further comprises programmed circuitry using the x-ray measurements to estimate a major and a minor axis of an ellipse that approximates the area of the body slice and using the axes to estimate the area at.

19. A system as in claim 18 in which the processing unit further includes programmed circuitry using the x-ray measurements to estimate lean tissue in the body slice and using the estimates of fat and lean tissue to calculate a percentage metric for visceral fat content in the body slice.

20. A system as in claim 16 in which the processing unit includes programmed circuitry deriving individual estimates of visceral fat for each of a number of the pixel positions.

21. A system as in claim 20 in which the processing unit includes programmed circuitry using information related to the individual estimates of visceral fat for at least some of the pixel positions to estimate fat associated with individual organs in the viscera.

22. A system as in claim 21 in which the processing unit includes programmed circuitry using the x-ray measurements to estimate subcutaneous fat in x-ray paths from a source of x-rays individually for a number of pixel positions, and using the estimates for the paths in estimating visceral fat in said paths.

23. A system as in claim 22 in which the processing unit includes programmed circuitry using the estimates of visceral fat along the paths to estimate visceral fat in selected regions of the body slice.

24. A system as in claim 16 in which the processing unit includes programmed circuitry deriving visceral fat metrics and information regarding relationships of the metrics to comparable metrics for selected normative ranges, and the display displays said information regarding relationships.