Acquisition of the Karhunen-Loeve expansion to reduce MR imaging times

Examines the advantages and disadvantages of using a Karhunen-Loeve (K-L) expansion of a training set of images to reduce the number of encodes required for a magnetic resonance (MR) image of a new object. One form of this technique has been proposed (Yue Cao and Levin, 1993) and another implemented (Zientara et al., 1994). The present authors evaluate: a) the error likely to be achieved as a function of the number of encodes and b) two technical problems: reduced SNR in the images and smoothing of the K-L functions in practice. They propose the use of localized trigonometric bases developed by Coifman and Wickerhauser (1992) as an alternative to the K-L basis. The localized trigonometric bases approach the error achieved by the K-L basis, but they are easier to use and can be used with existing methods for fast acquisition