In this paper we report the development of a high resolution dynamic micro-computed tomography (CT) scanner
with a stationary mouse bed using a compact carbon nanotube (CNT)
x-ray tube. The scanner comprises a
rotating x-ray tube and detector pair and a stationary and a horizontally positioned small animal bed. The system
is optimized for in vivo mouse cardiac imaging. Its performance is evaluated with CT scans of phantoms and
free-breathing mice. The modulation transfer function (MTF) at 10% is 5 lp/mm. At single frame acquisition,
mouse cardiac micro-CT at 20msec temporal resolution has been demonstrated by prospectively gating the
imaging acquisitions to both respiration and cardiac signals.
We have designed and built a stationary digital breast tomosynthesis (DBT) system containing a carbon nanotube
based field emission x-ray source array to examine the possibility of obtaining a reduced scan time and improved
image quality compared to conventional DBT systems. There are 25 individually addressable x-ray sources in our
linear source array that are evenly angularly spaced to cover an angle of 48°. The sources are turned on sequentially
during imaging and there is no motion of either the source or the detector. We present here an iterative reconstruction
method based on a modified Ordered-Subset Convex (MOSC) algorithm that was employed for the reconstruction of
images from the new DBT system. Using this algorithm based on a maximum-likelihood model, we reconstruct on
non-cubic voxels for increased computational efficiency resulting in high in-plane resolution in the images. We have
applied the reconstruction technique on simulated and phantom data from the system. Even without the use of the
subsets, the reconstruction of an experimental 9-beam system with 960×768 pixels took less than 6 minutes (10
iterations). The projection images of a simulated mammography accreditation phantom were reconstructed using
MOSC and a Simultaneous Algebraic Reconstruction technique (SART) and the results from the comparison between
the two algorithms allow us to conclude that the MOSC is capable of delivering excellent image quality when used in
tomosynthesis image reconstruction.
A prototype physiologically gated micro-computed tomography (micro-CT) system based on a field emission
micro-focus x-ray source has been developed for in vivo imaging of small animal models. The novel x-ray
source can generate radiation with a programmable waveform that can be readily synchronized and gated with
non-periodic physiological signals. The system performance is evaluated using phantoms and sacrificed and
anesthetized mouse models. Prospective respiratory-gated CT images of anesthetized free-breathing mice are
collected using this scanner at 100msec temporal resolution and 10 lp/mm of 10% system MTF.
A stationary digital breast tomosynthesis (DBT) system using a carbon nanotube based multi-beam field emission x-ray
(MBFEX) source has been designed. The purpose is to investigate the feasibility of reducing the total imaging time,
simplifying the system design, and potentially improving the image quality comparing to the conventional DBT
scanners. The MBFEX source consists of 25 individually programmable x-ray pixels which are evenly angular spaced
covering a 48° field of view. The device acquires the projection images by electronically switching on and off the
individual x-ray pixels without mechanical motion of either the x-ray source or the detector. The designs of the x-ray
source and the imaging system are presented. Some preliminary results are discussed.
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