Calibration phantom comprising a reflectance calibration target and a plurality of radio-opaque markers

1. A calibration phantom comprising:

a surface having a reflectance calibration target with a pattern indicative of one or more spatial reference positions; and

a plurality of radio-opaque markers positionally correlated to the one or more spatial reference positions of the reflectance calibration target, wherein one or more of the plurality of radio-opaque markers are disposed on the reflectance calibration target.

2. The calibration phantom of claim 1 , wherein the pattern includes a checkerboard pattern.

3. The calibration phantom of claim 2 , wherein one or more of the plurality of radio-opaque markers are positioned at intersection points along the reflectance calibration target.

4. The calibration phantom of claim 1 , wherein the pattern provides point clouds, curves, or lines.

5. The calibration phantom of claim 1 , wherein the surface is configured to reflect the pattern, the pattern comprising projected light from an illumination source.

6. The calibration phantom of claim 1 , wherein the pattern of the reflectance calibration target is perceptible to a viewer.

7. The calibration phantom of claim 1 , wherein one or more of the plurality of radio-opaque markers comprise metal beads.

8. A calibration phantom, comprising:

a housing including a surface;

a calibration target on a selected area of the surface, the calibration target formed as a patterned image using visible or near-visible illumination; and

a plurality of radio-opaque markers spatially disposed at predetermined positions within the selected area.

9. The calibration phantom of claim 8 , wherein the patterned image comprises a regularly repeating pattern.

10. The calibration phantom of claim 8 , wherein the patterned image comprises pattern features that point to at least one of the plurality of radio-opaque markers.

11. An imaging system comprising:

an x-ray source;

a radiographic detector configured to acquire one or more x-ray images of a subject positioned between the x-ray source and the radiographic detector;

a camera coupled to the x-ray source,

wherein the camera is configured to acquire one or more reflectance images of a surface of the subject; and

a calibration phantom positioned between the x-ray source and the radiographic detector,

the calibration phantom comprising:

a surface having a reflectance pattern thereon, the reflectance pattern visible on a selected area of the surface, the reflectance pattern configured to be captured by the camera; and

one or more radio-opaque markers within the selected area, the one or more radio-opaque markers configured to be captured by the radiographic detector.

12. The imaging system of claim 11 , wherein the reflectance pattern comprises a regularly repeating pattern.

13. The imaging system of claim 11 , wherein the reflectance pattern comprises pattern features positioned to point to at least one of the one or more radio-opaque markers.

14. A method for calibration of a radiographic imaging apparatus, the method executed at least in part by a computer, comprising:

providing a calibration target having a surface;

projecting a visible pattern on the surface of the calibration target;

acquiring a reflectance image of the visible pattern;

processing the acquired reflectance image to derive one or more spatial reference positions from the calibration target based on the visible pattern;

acquiring a radiographic image of one or more radio-opaque markers disposed within the visible pattern on the surface of the calibration target;

processing the acquired radiographic image to derive one or more positions of the one or more radio-opaque markers;

correlating the one or more spatial reference positions from the calibration target with the one or more positions of the one or more radio-opaque markers and generating transformation parameters; and

displaying, storing, or transmitting a radiographic image conditioned by the transformation parameters.

15. The method of claim 14 , wherein acquiring the reflectance image of the calibration target comprises acquiring an image generated using structured illumination.

16. The method of claim 14 , wherein acquiring the radiographic image of the one or more radio-opaque markers comprises acquiring a projection image from a cone-beam computed tomography apparatus.

17. The method of claim 14 , further comprising projecting a regularly repeating visible pattern on the surface of the calibration target.

18. The method of claim 14 , further comprising disposing at least one of the one or more radio-opaque markers at an intersection point of the visible pattern on the surface of the calibration target.

19. The method of claim 14 , further comprising forming features in the visible pattern of the calibration target that point to at least one of the one or more radio-opaque markers.