University of North Carolina at Chapel Hill Graduate School
Doi
Abstract
Digital breast tomosynthesis systems (DBT) use a single thermionic x-ray source that moves around the breast in a fixed angular span. As a result, all current DBT system requires the mechanical motion of the x-ray source during the scan, limiting image quality either due to the focal spot blurring or a long scan time. This causes an unfavorable reduction in the in-plane resolution compared to 2D mammography. Our research group developed and demonstrated a first generation stationary digital breast tomosynthesis (s-DBT) system that uses a linear carbon nanotube (CNT) x-ray source array. Since the stationary sources are not subject to focal spot blurring, and images can be acquired rapidly, the in-plane system resolution is improved. Additionally, image acquisition time is independent of angular span since there is no motion, allowing for large angular spans, and increased depth resolution. The improved resolution of the first generation s-DBT system over continuous motion (CM) DBT has been demonstrated with image evaluation phantoms and a human specimen study. The first generation s-DBT is currently undergoing clinical trials at the University of North Carolina Cancer Hospital. Limitations associated with the first generation system, such as limited tube flux, and limited x-ray energy, placed limitations on our clinical trials and future clinical implementation. Also, the limited angular span could be improved for increased depth resolution, as there is no cost on patient imaging time. The goal of this thesis work was to design construct and characterize a second generation s-DBT system, capable of faster image acquisition times, and higher depth resolution than our first generation system. The second generation s-DBT system was built using a newly designed distributed CNT x-ray source array. The system was then characterized and compared to the first generation system and two commercially available DBT systems. Using physical measurements that are used in medical imaging, the system showed significant improvement in resolution over the first generation system and both commercially available systems, coupled with equal or faster image acquisition times. A separate study investigating the feasibility of contrast enhanced (CE) imaging was conducted, where the system showed capability in both temporal subtraction (TS) and dual energy (DE) imaging.Doctor of Philosoph
