Removal of Edge Artifact due to Partial Volume Effect in the Adaptive Template Filtering

Ahn, C B; Song, Y C

Abstract

Adaptive template filtering has been proposed recently for enhancement of signal-to-noise ratio without loss of resolution. In the adaptive template filtering, an optimal template among multiple templates is selected, then linear least square error filtering based on the template is applied in voxel by voxel basis. In some magnetic resonance imaging, where the distribution of gray level has relatively small dynamic range, e.g., T1 imaging, however, artificial stair-like artifact is observed at near edges. This is partially due to the edge enhancement effect in such voxels that contain multiple compounds at the boundaries of tissues. The gray levels of these voxels become similar gray levels of near dominant voxels that contain single compound by the adaptive filtering, which enlarges edge discontinuities. In this paper, we propose a technique to eliminate such artifact by identifying those voxels that contain multiple compounds and assigning the largest template for them. Filtered images with the proposed technique show substantial visual enhancement at the edges without degradation of peak signal-to-noise ratio compared to the original adaptive template filtering for both magnetic resonance images and phantom images.