Within this Ph.D. project, three-dimensional reconstruction methods for
moving objects (with a focus on the human heart) from cone-beam X-ray
projections using iterative reconstruction algorithms were developed and
evaluated. This project was carried in collaboration with the Digital
Imaging Group of Philips Research Europe – Hamburg.
In cardiac cone-beam computed tomography (CT) a large effort is
continuously dedicated to increase scanning speed in order to minimize
patient or organ motion during acquisition. In particular, motion
causes severe artifacts such as blurring and streaks in tomographic
images. While for a large class of applications the current scanning
speed is sufficient, in cardiac CT image reconstruction improvements are
still required. Whereas it is currently feasible to achieve stable
image quality in the resting phases of the cardiac cycle, in the phase
of fast motion data acquisition is too slow. A variety of algorithms to
reduce or compensate for motion artifacts have been proposed in
literature. Most of the correction methods address the calculation of
consistent projection data belonging to the same motion state (gated CT
reconstruction). Even if gated CT leads to better results, not only with
respect to the processing time but also regarding the image quality, it
is also limited in its temporal and spatial resolution due to the
mechanical movement of the gantry. This can lead to motion blurring,
especially in the phases of fast cardiac motion during the RR interval. A
motion-compensated reconstruction method for CT can be used to improve
the resolution of the reconstructed image and to suppress motion
blurring. Iterative techniques are a promising approach to solve this
problem, since no direct inversion methods are known for arbitrarily
moving objects.
In this work, we therefore introduced motion compensation into image
reconstruction. In order to determine the unknown cardiac motion, 3
different cardiac-motion estimation methodologies were implemented.
Visual and quantitative assessment of the method in a number of
applications, including: phantoms; cardiac CT reconstructions; Region of
Interest (ROI) CT reconstructions of left and right coronaries of
several clinical patients, confirmed its potential.http://repub.eur.nl/res/pub/19823/100618_Isola%2C%20Alfonso%20Agatino.pdf
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