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Proceedings Paper

Quantification and correction of intensity nonuniformities in low-field MRI
Author(s): Juan M. Parra Robles; Evelio R Gonzalez; Ilse Berdellans; William Dominquez
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Paper Abstract

In MRI, the intensity distortion usually does not greatly affect the clinical relevance of the images, but its correction is an essential step for image segmentation and intensity measurements. In our MR scanner, the main sources of nonuniformity are the RF transmitting system, the receiver coil and the analogue receiver filter. The filter response was isolated and measured from images with no signal. The Homomorphic Unsharp Masking (HUM) was used to correct the RF related distortion. The HUM method is used to remove the image low-frequency components. In addition to its relatively long processing time (large windows are needed), the HUM method has some other disadvantages: it can affect the image contrast and generate artifacts at sharp edges. In order to overcome the limitations of the standard HUM approach, in this work, the correction maps were obtained from minimal contrast images (intermediate-echo images from a multiecho sequence). The correction maps obtained from these images were used to correct the corresponding high contrast images obtained from this sequence. This way, optimal results were obtained using small windows (9 X 9 - 13 X 13). The computation time was reduced and the image contrast was not affected. The background pixels were easier to handled and no artifacts were generated.

Paper Details

Date Published: 25 April 2000
PDF: 9 pages
Proc. SPIE 3977, Medical Imaging 2000: Physics of Medical Imaging, (25 April 2000); doi: 10.1117/12.384549
Show Author Affiliations
Juan M. Parra Robles, Univ. de Oriente (Cuba)
Evelio R Gonzalez, Univ. de Oriente (Cuba)
Ilse Berdellans, Univ. de Oriente (Cuba)
William Dominquez, Univ. de Oriente (Cuba)

Published in SPIE Proceedings Vol. 3977:
Medical Imaging 2000: Physics of Medical Imaging
James T. Dobbins; John M. Boone, Editor(s)

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