Measuring signal amplitude : lizard brain atlas

Abstract

There are many types of NMR experiment where it is necessary to extract the amplitude of a spectral peak relative to its amplitude from a previous iteration of the sequence. Pulsed Gradient Spin Echo (PGSE) and Pulsed Gradient Stimulated Echo (PGSTE) diffusion measurements fall into this category since the attenuation of the peak gives us the diffusion coefficient. Similarly, T1 and T2 measurements rely on the measurement of relative spectral peak heights. Typically, peak intensity is measured by either integrating under the absorption Lorentzian peak or taking its amplitude. In a recent and ongoing project using simulated noisy spectra, these methods were compared with each other and with a method that involves fitting a Lorentzian curve directly to the spectrum or a decaying complex exponential to the FID using Levenberg-Marquardt non-linear least squares fitting. The results indicate that the best method of extracting signal intensity is to use a matched filter and then to measure the amplitude of the peak of interest. The second part of the presentation will focus on the recent publication of a 3D MRI-based atlas of a lizard brain using data from a long running project with Daniel Hoops from ANU (at the time of the project) and now at McGill University and initiated through the National Imaging Facility (NIF) [1-3]. The 3D-MRI model of a tawny dragon brain is available for viewing online and can be downloaded from the Wiley Biolucida Server at wiley.biolucida.net