ABSTRACT
Motivated by work in the area of dynamic magnetic resonance imaging (MRI), we develop a new approach to the problem of reduced-order MRI acquisition. Efforts in this field have concentrated on the use of Fourier and singular value decomposition (SVD) methods to obtain low-order representations of an entire image plane. We augment this work to the case of imaging an arbitrarily-shaped region of interest (ROI) embedded within the full image. After developing a natural error metric for this problem, we show that determining the minimal order required to meet a prescribed error level is in general intractable, but can be solved under certain assumptions. We then develop an optimization approach to the related problem of minimizing the error for a given order. Finally, we demonstrate the utility of this approach and its advantages over existing Fourier and SVD methods on a number of MRI images.
ABSTRACT
To determine the effectiveness of an antiviral to prevent herpes labialis during a brief, high-risk circumstance, 147 persons with a history of sun-induced recurrences were treated prophylactically with oral acyclovir or matching placebo and were observed during their ski holidays. Five (7%) of 75 acyclovir-treated subjects developed lesions compared with 19 (26%) of 72 persons in the placebo group.