A prototype stationary digital breast tomosynthesis (s-DBT) system has been developed by retrofitting a Hologic Selenia
Dimension rotating gantry tomosynthesis scanner with a spatially distributed carbon nanotube (CNT) x-ray source array.
The goal is to improve the system spatial resolution by removing the x-ray tube motion induced focal spot blurring. The
CNT x-ray source array comprises 31 individually addressable x-ray beams covering 30° angular span. Each x-ray beam
has a minimum focal spot size of 0.64×0.61mm
(full-width-at-half-maximum), a stationary W anode operating up to
50kVp, and 1mm thick Al filter. The flux from each beam is regulated and varied using dedicated control electronics.
The maximum tube current is determined by the heat load of the stationary anode and depends on the energy, pulse
width and the focal spot size used. Stable operation at 28kVp, 27mA tube current, 250msec pulse width and 38mA tube
current, 183msec pulse width per exposure was achieved with extended lifetime. The standard ACR phantom was
imaged and analyzed to evaluate the image quality. The actual scanning speed depends on the number of views and the
readout time of the x-ray detector. With the present detector, 6 second scanning time at either 15 views or 31 views can
be achieved at 100mAs total imaging dose with a detector readout time of 240msec.
Tomosynthesis requires projection images from different viewing angles. Using a distributed x-ray source this can be
achieved without mechanical motion of the source with the potential for faster image acquisition speed. A distributed xray
tube has been designed and manufactured specifically for breast tomosynthesis. The x-ray tube consists of 31 field
emission x-ray sources with an angular range of 30°. The total dose is up to 100mAs with an energy range between 27
and 45 kVp. We discuss the source geometry and results from the characterization of the first prototype. The x-ray tube
uses field emission cathodes based on carbon nanotubes (CNT) as electron source. Prior to the manufacturing of the
sealed x-ray tube extensive testing on the field emission cathodes has been performed to verify the requirements for
commercial tomosynthesis systems in terms of emission current, focal spot size and tube lifetime.
Tomosynthesis imaging requires projection images from different viewing angles. Conventional systems use a moving xray
source to acquire the individual projections. Using a stationary distributed x-ray source with a number of sources that
equals the number of required projections, this can be achieved without any mechanical motion. Advantages are a
potentially faster image acquisition speed, higher spatial and temporal resolution and simple system design. We present
distributed x-ray sources based on carbon nanotube (CNT) field emission cathodes. The field emission cathodes deliver
the electrons required for x-ray production. CNT emitters feature a stable emission at high current density, a cold
emission, excellent temporal control of the emitted electrons and good configurability. We discuss the use of stationary
sources for two applications: (i) a linear tube for stationary digital breast tomosynthesis (sDBT), and (ii) a square tube for
on-board tomosynthesis image-guided radiation therapy (IGRT). Results from high energy distributed sources up to
160kVp are also presented.