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Quantitative evaluation of metal artifact reduction techniques in MRI Kolind, Shannon Heather


Several techniques for metal artifact reduction in MRI were studied in order to determine their effectiveness. The noise and blur introduced by the techniques were also investigated. To this end, non-metallic replicas of two metal implants (stainless steel and titanium/chromium-cobalt femoral prostheses) were fabricated from wax, and MR images were obtained of each component immersed in water. The difference between the images of each metal prosthesis and its wax replica was measured in terms of energy. The difference energy attributed to noise and blur were isolated, resulting in a measure of the metal artifact. This new "gold standard" method was successfully demonstrated to provide a quantitative means of measuring metal artifact. Several pulse sequences were evaluated in terms of metal artifact reduction capability, as well as signal-to-noise ratio and blur. The analysis revealed that increasing the image bandwidth from ±16 kHz to ±64 kHz reduced metal artifact by an average of 60%, while employing View Angle Tilting (VAT) was only slightly more efficient, reducing metal artifact by an average of 63%. The metal artifact reduction sequence (MARS), which combines the increased image bandwidth with VAT as well as an increased slice-select bandwidth, resulted in the least amount of image distortion, reducing the artifact by an average of 79%. The signal-to-noise ratio was lower for MARS, but blurring was found to be significantly improved.

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