<title>Two-dimensional locally focused MRI: applications to dynamic and spectroscopic imaging</title>

Abstract

Conventional magnetic resonance images have uniform spatial resolution across the entire field of view. We recently described a method of creating MR images with user-specified spatial resolution along one dimension of the field of view. This paper presents the 2D generalization of this technique which allows the user to specify arbitrary spatial resolution in arbitrary 2D regions. These images are reconstructed from signals which sparsely sample the k-space representation of the image. Therefore, locally focused images can be acquired in less time than that required by Fourier imaging with uniformly high resolution. In this paper we show how to increase the temporal resolution of dynamic imaging (e.g. interventional imaging) by using high resolution in areas of expected change and lower resolution elsewhere. Alternatively, by matching the local spatial resolution to the expected edge content of the image, it is possible to avoid the localized truncation artifacts which mark Fourier images reconstructed from the same number of signals. For example, we show how proton spectroscopic images of the head may be improved by using high resolution in the neighborhood of scalp lipids which might otherwise cause truncation artifacts.