Directed X-ray fields for tomosynthesis

1. A radiographic imaging system for tomosynthesis x-ray imaging and general projection radiography x-ray imaging, the radiographic imaging system comprising:

an x-ray source assembly comprising:

a plurality of distributed x-ray sources in a ring formation, the distributed x-ray sources supported by a ring shaped structure, each of the distributed x-ray sources operable at a first power level for said tomosynthesis x-ray imaging; and

a central x-ray source at or near a the central axis of the ring shaped structure, the central x-ray source supported by a central support structure and operable at a second power level greater than the first power level for said general projection radiography x-ray imaging;

an x-ray generator;

a control unit connected to the x-ray generator to control activation of the distributed x-ray sources and the central x-ray source; and

a collimator formed in a shape of a ring and comprising a first plurality of openings through the ring, the first plurality of openings each configured to provide fixed collimation for one of the plurality of distributed x-ray sources.

2. The radiographic imaging system of claim 1 , wherein the collimator is configured to collimate x-ray beams from the distributed x-ray sources such that the collimated x-ray beams overlap at a first distance from the distributed x-ray sources.

3. The radiographic imaging system of claim 1 , wherein the distributed x-ray sources are housed in the same vacuum chamber or in the same radiation shielding.

4. The radiographic imaging system of claim 1 , further comprising:

a moveable transport frame; and

an adjustable support structure coupled to the moveable transport frame;

wherein the x-ray source assembly is mounted to the adjustable support structure and is configured to direct x-ray radiation towards a subject from the distributed x-ray sources and/or the central x-ray source.

5. A radiographic imaging system for tomosynthesis x-ray imaging and projection x-ray imaging, the radiographic imaging system including:

a first x-ray source;

a first collimator to collimate the first x-ray source, the first collimator configured to be adjustable in at least two transverse dimensions;

a plurality of distributed x-ray sources;

a ring shaped structure configured to support the plurality of distributed x-ray sources in a ring formation, wherein the first x-ray source is at or near a central axis of the ring shaped structure; and

a second collimator formed in a shape of a ring, the second collimator comprising a plurality of openings each configured to collimate one of the plurality of distributed x-ray sources.

6. The radiographic imaging system of claim 5 , wherein each of the plurality of distributed x-ray sources is configured to output x-rays at a first power level sufficient for tomosynthesis imaging, the first x-ray source is configured to output x-rays at a second power level sufficient for standard projection radiography, and wherein the first power level is less than the second power level.

7. The radiographic imaging system of claim 5 , wherein the first x-ray source comprises a radiation shield or a vacuum chamber.

8. The radiographic imaging system of claim 6 , further comprising a first generator connected to the first x-ray source and a second generator connected to the plurality of distributed x-ray sources.

9. The radiographic imaging system of claim 5 , wherein the second collimator comprises at least four openings each movable between first and second positions to provide different focal lengths for at least two of the distributed x-ray sources.

10. The radiographic imaging system of claim 5 , further comprising:

a moveable transport frame;

an adjustable support structure coupled to the moveable transport frame; and

control circuitry in the moveable transport frame and coupled to the plurality of distributed x-ray sources, the control circuitry configured to receive projection images each corresponding to one of the plurality of distributed x-ray sources for reconstruction of a tomosynthesis image, wherein the plurality of distributed x-ray sources is mounted to the adjustable support structure.

11. The system of claim 2 , wherein the collimator comprises a second plurality of openings each configured to collimate one of the distributed x-ray sources such that the x-ray beams collimated by the second plurality of openings overlap at a second distance from the distributed x-ray sources.

12. The system of claim 2 , wherein the collimated x-ray beams overlap within an area of a radiographic detector positioned at the first distance from the distributed x-ray sources.

13. The system of claim 11 , wherein the x-ray beams collimated by the second plurality of openings overlap within an area of a radiographic detector positioned at the second distance from the distributed x-ray sources.

14. The system of claim 5 , wherein the plurality of openings each comprises a fixed shape opening.

15. The radiographic imaging system of claim 1 , wherein the collimator is configured to slide or rotate between a first fixed focal length position and a second fixed focal length position to provide different focal lengths for the plurality of distributed x-ray sources.

16. The radiographic imaging system of claim 5 , wherein the second collimator is configured to slide or rotate between a first fixed focal length position and a second fixed focal length position to provide different focal lengths for the plurality of distributed x-ray sources.