Abstract:
Reconstruction is the abstract rebuilding of something that has been torn apart. In the
medical imaging context, it is often necessary to acquire data from methods that
essentially tear data apart in order to be able to view what is inside. Also, a big part of
reconstruction is then being able to view, or visualise, all the data once it is been put
back together again. In MRI, the imaging device acquires data of a cross-sectional
plane of the tissue being studied. The process of reconstruction then involves
rebuilding of the cross-sectional view of that plane from the acquired data. Usually,
the imaging device acquires data from a number of cross-sectional planes of the tissue
being examined. Then, in reconstruction, all these planes are stacked back together to
obtain a complete picture of the tissue.
Image reconstruction in MRI is usually performed by dedicated hardware. A typical
system usually consists of multiprocessors, application specific integrated circuits
(ASIC) and uses parallel processing techniques. These systems are capable of high speed
image reconstruction, both 2D and 3D, high resolution image display and
manipulation. Obviously, these systems are fairly expensive.
In this project a general purpose PC operating on Microsoft® Windows" 98 operating
system was used to reconstruct a 2D image of a slice through the human head, using
head scan data available from a MRI scanner. The FID signals from the scanner were
available as projection data, which have been collected by suitably rotating the
magnetic gradients. The filtered back-projection algorithm with nearest neighbour
interpolation scheme was used in the reconstruction program, which was written in
Matlab ®. The resulting image from this system is acceptable. With the ever-increasing
processor power of PC's and cost of PC's coming down, PC-based image
reconstruction would find its way in a cost effective MRI system
