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Optimizing the Point Spread Function in

Summary: Optimizing the Point
Spread Function in
Phase-Encoded Magnetic
Resonance Microscopy
Department of Electrical and Computer Engineering, Beckman Institute for Advanced Science and Technology,
University of Illinois at Urbana-Champaign, 4221 Beckman Institute, 405 North Mathews, Urbana, IL 61801,
and Physikalisches Institut, EPV, University of Wu¨rzburg, Germany
ABSTRACT: Three-dimensional phase-encoded magnetic resonance microscopy is the
most promising method for obtaining images with isotropic spatial resolutions on the order
of a few micrometers. The attainable spatial resolution is limited by the available gradient
strength (Gmax) and the molecular self-diffusion coefficient (D) of the sample. In this study,
numerical simulations in the microscopic-size regime are presented in order to show that
for given values of Gmax and D, there exists an optimum number of phase-encoding steps
that maximize the spatial resolution in terms of minimizing the full-width at half-maximum
(FWHM) of the image point spread function (PSF). Unlike the case of "macroscopic" imaging,
in which diffusion plays an insignificant role in determining spatial resolution, acquiring
data beyond this optimal value actually degrades the image PSF. An alternative version of
phase encoding, using a variable phase-encoding time rather than a variable gradient
strength, is analyzed in terms of improvements in the image PSF and/or reductions in the


Source: Andrews, Anne M. - Huck Institutes of the Life Sciences, Pennsylvania State University


Collections: Biology and Medicine