Purpose: To develop a two-dimensional (2D) stationary thermionic x-ray source array for breast tomosynthesis, in order to dramatically improve image quality and reduce acquisition time.
Methods: A Multiple X-ray source Array (MXA) was developed with 11 focal spots distributed along a ~28 cm long rotating anode shaft which supports eleven ~10 cm diameter anode disks. Individual thermionic (hot) grid-pulsed cathode assemblies supply pulsed electron beams which strike the end of each disk. All x-ray sources are within the same vacuum enclosure and are individually addressable using TTL control electronics. Coupled with a flat panel detector, this 11-source array of x-ray sources was used to collect tomosynthesis data using an orange as a test object. By adding a second row of cathodes on the other side of the anode disks, two rows of 11 x-ray focal spots will produce a 2D array (2 x 11) of sources for breast tomosynthesis. A breast CT data set was used to simulate 22 projection images with the 2D source distribution, and a model-based iterative reconstruction algorithm with spatially invariant regularization was used to reconstruct tomosynthesis images.
Results: The 11-source x-ray tube demonstrated rapid acquisition, robust performance at 35 kV, and small focal spots (~0.3 mm each). Computer simulation of the proposed 2D array tomosynthesis system with 22 source positions shows a marked improvement for in-plane sharpness and thinner slices. Acquisition time using a 20 FPS detector would be 1.1 sec.
Conclusion: All clinical breast tomosynthesis systems use a one-dimensional arc with acquisition times ranging from 3.7 to 25 s. Due to constraints on acquisition time, moving sources are not practical for 2D geometry tomosynthesis. The proposed stationary hot-cathode source array provides rapid acquisition (1.1 s for 22 sources) for low motion artifact tomosynthesis images with much better slice separation and in-plane object delineation.
Funding Support, Disclosures, and Conflict of Interest: JMB is a stockowner and board member in Izotropic Corp, has funding from Canon Medical Systems, is on the board of ICRU, receives a stipend from AAPM as Editor-in-Chief of Medical Physics, and receives book royalties from Wolters Kluwer. JMB and JHS have patent-pending with royalties from The Phantom Lab.