Designing feedbackbased contrast enhancement for

Authors: Susie Y Huang Jon K Furuyama YungYa Lin

Publish Date: 2006/12/15

Volume: 19, Issue: 6, Pages: 333-346

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Abstract

Objective Nonlinear feedback interactions induced by the spins themselves have recently been introduced as novel MRI contrast enhancement mechanisms sensitive to small differences in MR parameters Developing feedbackbased contrast enhancement into a useful tool for in vivo imaging requires improved techniques that are robust to inhomogeneity and sensitive to subtle anatomical/physiological variationsMaterials and methods Three different imaging methods combining the radiation damping feedback field with the distant dipolar field applied radiofrequency RF fields and local dipole fields respectively were designed and tested through numerical simulations on simple phantoms These methods were demonstrated experimentally on live guppy fish developing frog embryos and blood in in vitro tissue samples by microimaging at 141 TResults The developed feedbackbased methods yielded images that identified distinct morphological features with superior contrast compared with conventional MR images and those acquired under radiation damping only Positive contrast due to evolution under radiation damping and local dipole fields was also observed in SPIOs and bloodConclusion Approaches to enhancing feedbackbased contrast were successfully designed and demonstrated in vitro and in vivo The newly devised methods were less sensitive to field inhomogeneity and prolonged evolution under the feedback fields allowing for better visualization of contrast in vivo

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