Jochen Zeltner

Deformable Mosaicing for Whole-Body MRI

Whole-body magnetic resonance imaging is an emerging application gaining vast clinical interest during the last years. Although recent technological advances shortened the longish acquisition time, this is still the limiting factor avoiding its wide-spread clinical usage. The acquisition of images with large field-of-view helps to relieve this drawback, but leads to significantly distorted images. Therefore, we propose a deformable mosaicing approach, based on the simultaneous registration to linear weighted averages, to correct for distortions in the overlapping area. This method produces good results on in-vivo data and has the advantage that a seamless integration into the clinical workflow is possible.

Sphere Extraction in MR Images with Application to Whole-Body MRI

Recent technological advances in magnetic resonance imaging (MRI) lead to shorter acquisition times and consequently make it an interesting whole-body imaging modality. The acquisition time can further be reduced by acquiring images with a large field-of-view (FOV), making less scan stations necessary. Images with a large FOV are however disrupted by severe geometric distortion artifacts, which become more pronounced closer to the boundaries. Also the current trend in MRI, towards shorter and wider bore magnets, makes the images more prone to geometric distortion. In a previous work,4 we proposed a method to correct for those artifacts using simultaneous deformable registration. In the future, we would like to integrate previous knowledge about the distortion field into the process. For this purpose we scan a specifically designed phantom consisting of small spheres arranged in a cube. In this article, we focus on the automatic extraction of the centers of the spheres, wherein we are particularly interested, for the calculation of the distortion field. The extraction is not trivial because of the significant intensity inhomogeneity within the images. We propose to use the local phase for the extraction purposes. The phase has the advantage that it provides structural information invariant to intensity. We use the monogenic signal to calculate the phase. Subsequently, we once apply a Hough transform and once a direct maxima search, to detect the centers. Moreover, we use a gradient and variance based approach for the radius estimation. We performed our extraction on several phantom scans and obtained good results.

MRI Composing for Whole Body Imaging

Whole-body magnetic resonance imaging is an emerging application gaining vast clinical interest during the last years. Although recent technological advances shortened the longish acquisition time, this is still the limiting factor avoiding its wide-spread clinical usage. The acquisition of images with large field-of-view helps to relieve this drawback, but leads to significantly distorted images. In this paper, a novel scheme for MRI composing is presented. The approach is based on simultaneous registration of two MRI volumes to their linear weighted average. The method successfully compensates for the distortions and allows to generate high-resolution whole body images. Results on several in-vivo data sets are presented.