Carbon nanotube electron field emitters for x-ray imaging of human breast cancer

For imaging human breast cancer, digital breast tomosynthesis (DBT) has been shown to improve image quality and breast cancer detection in comparison to two-dimensional (2D) mammography. Current DBT systems have limited spatial resolution and lengthy scan times. Stationary DBT (s-DBT), utilizing an array of carbon nanotube (CNT) field emission x-ray sources, provides increased spatial resolution and potentially faster imaging than current DBT systems. This study presents the results of detailed evaluations of CNT cathodes for x-ray breast imaging tasks. The following were investigated: high current, long-term stability of CNT cathodes for DBT; feasibility of using CNT cathodes to perform a 2D radiograph function; and cathode performance through several years of imaging. Results show that a breast tomosynthesis system using CNT cathodes could run far beyond the experimentally tested lifetime of one to two years. CNT cathodes were found capable of producing higher currents than typical DBT would require, indicating that the s-DBT imaging time can be further reduced. The feasibility of using a single cathode of the s-DBT tube to perform 2D mammography in 4 s was demonstrated. Over the lifetime of the prototype s-DBT system, it was found that both cathode performance and transmission rate were stable and consistent.