Department of Electrical and Electronic Engineering, Imperial College London
Doi
Abstract
This thesis proposes optimal measures for the inter-system comparison of signal properties when assessing the imaging performance of Magnetic Resonance Imaging (MRI) scanners. MRI has become a popular clinical imaging modality and there are many manufacturers producing systems of various quality. It is essential, therefore, that the performance of each MRI system can be measured and compared.
Five criteria have been identified as being of prime importance, namely, the signal-to-noise ratio (SNR), signal non-uniformity, resolution, system induced ghost artefacts and patient induced ghost artefacts. The research concentrated directly on the derivation of performance parameters from test object images. For each criterion a specific algorithm has been developed to obtain optimal parameters. For SNR, a method of evaluation has been derived that utilises the Wiener spectrum to distinguish between random and non-random noise in the MR image. The assessment of signal non-uniformity has been improved by applying statistical parameters. The Modulation Transfer Function has been used in the evaluation and comparison of resolution of MRI systems. Crosscorrelation techniques have enabled the complete automatic location and analysis of ghost artefacts in MR test object images. An autocorrelation technique has been created to compare the degree of respiratory motion artefact present in an MR image. All the techniques, wherever possible, have been optimised for speed and automated to eliminate operator dependency.
The strength of this thesis lies in the fact that the data used is not simulated, it is actual data gathered with the full support of each manufacturer in the country of origin. This enables truly applicable comparison parameters to be derived. This is a prominent deficiency for workers who mathematically create images or who work with only one system. The success of the five parameterisations is demonstrated by performing an inter-system comparison of ten commercially available scanners.Open Acces
