Digital breast tomosynthesis (DBT) is a limited angle computed tomography technique that can distinguish tumors from its overlying breast tissues and has potentials for detection of cancers at a smaller size and earlier stage. Current prototype DBT scanners are based on the regular full-field digital mammography systems and require partial isocentric motion of an x-ray tube over certain angular range to record the projection views. This prolongs the scanning time and, in turn, degrades the imaging quality due to motion blur. To mitigate the above limitations, the concept of a stationary DBT (s-DBT) scanner has been recently proposed based on the newly developed spatially distributed multibeam field emission x-ray (MBFEX) source technique using the carbon nanotube. The purpose of this article is to evaluate the performance of the 25-beam MBFEX source array that has been designed and fabricated for the s-DBT system. The s-DBT system records all the projection images by electronically activating the multiple x-ray beams from different viewing angles without any mechanical motion. The configuration of the MBFEX source is close to the published values from the Siemens Mammomat system. The key issues including the x-ray flux, focal spot size, spatial resolution, scanning time, beam-to-beam consistency, and reliability are evaluated using the standard procedures. In this article, the authors describe the design and performance of a distributed x-ray source array specifically designed for the s-DBT system. They evaluate the emission current,current variation, lifetime, and focal spot sizes of the source array. An emission current of up to 18 mA was obtained at effective focal spot size. The experimentally measured focal spot sizes are comparable to that of a typical commercial mammography tube without motion blurring. Trade-off between the system spatial resolution, x-ray flux, and scanning time are also discussed. Projection images of a breast phantom were collected using the x-ray source array from 25 different viewing angles without motion. These preliminary results demonstrate the feasibility of the proposed s-DBT scanner. The technology has the potential to increase the resolution and reduce the imaging time for DBT. With the present design of 25 views, they demonstrated experimentally the feasibility of achieving 11 s scanning time at full detector resolution with source resolution without motion blur. The flexibility in configuration of the x-ray source array will also allow system designers to consider imaging geometries that are difficult to achieve with the conventional single-source rotating approach.
One of the authors (O.Z.) acknowledges supports from NCI (Grant No. U54CA119343) and the Lineberger Comprehensive Cancer Center and the University Cancer Research Fund at the University of North Carolina. One of the authors (X.C.) was supported by a graduate fellowship from NIBIB (Grant No. R33EB004204-S). The authors thank Dr. J. Geng and Dr. B. Gao of Xintek for technical assistance in CNT cathode fabrication and Dr. Sprenger of XinRay for discussions on x-ray focal spot measurement. They acknowledge discussions with Professor E. Pisano and Ms. E. Cole of UNC Radiology and Professor Y. Chen of SIU.
II.A. MBFEX source design and construction
II.B. Control electronics and interface
II.C. CNT field emission cathode
II.D. X-ray focal spot size measurement
II.E. System modulation transfer function
II.F. Entrance exposure value distribution
II.G. X-ray intensity uniformity
II.H. Spectrum measurement
II.I. Phantom imaging
III.A. X-ray tubecurrent
III.C. Cathode-to-cathode consistency
III.D. X-ray focal spots
III.E. Modulation transfer function
III.F. Entrance exposure value distribution
III.G. X-ray intensity uniformity
III.H. Spectrum measurement
III.I. Breast phantom imaging
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