Nuclear magnetic resonance spectroscopy. A stereospecific ^3J_(CF) coupling in the low-temperature ^(13)C nmr spectrum of 1,1-difluorocyclohexane

The proton-decoupled ^(13)C nmr spectrum of 1,1-difluorocyclohexane has been examined at room temperature and at -90 degrees C. There are only minor changes in the one-bond and two-bond carbon-fluorine scalar coupling constants at the lower temperature; however, the triplet observed for C-3 (^3J_(CF) = 4.7 Hz) collapses to a doublet (3JCF = 9.5 Hz) at -90 °C. It is proposed that only the equatorial fluorine is coupled with the C-3 carbon as the result of operation of a back-lobe orbital interaction

Analysis of myocardial motion using generalized spline models and tagged magnetic resonance images

Heart wall motion abnormalities are the very sensitive indicators of common heart diseases, such as myocardial infarction and ischemia. Regional strain analysis is especially important in diagnosing local abnormalities and mechanical changes in the myocardium. In this work, we present a complete method for the analysis of cardiac motion and the evaluation of regional strain in the left ventricular wall. The method is based on the generalized spline models and tagged magnetic resonance images (MRI) of the left ventricle. The whole method combines dynamical tracking of tag deformation, simulating cardiac movement and accurately computing the regional strain distribution. More specifically, the analysis of cardiac motion is performed in three stages. Firstly, material points within the myocardium are tracked over time using a semi-automated snake-based tag tracking algorithm developed for this purpose. This procedure is repeated in three orthogonal axes so as to generate a set of one-dimensional sample measurements of the displacement field. The 3D-displacement field is then reconstructed from this sample set by using a generalized vector spline model. The spline reconstruction of the displacement field is explicitly expressed as a linear combination of a spline kernel function associated with each sample point and a polynomial term. Finally, the strain tensor (linear or nonlinear) with three direct components and three shear components is calculated by applying a differential operator directly to the displacement function. The proposed method is computationally effective and easy to perform on tagged MR images. The preliminary study has shown potential advantages of using this method for the analysis of myocardial motion and the quantification of regional strain

Imaging and localized spectroscopy of 13C by polarization transfer

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27907/1/0000328.pd

Measuring cardiac strain using Laplacian smoothing splines

A scheme for obtaining strain maps from a set of MRI scans of the heart is presented. Using a technique known as the Spatial Modulation of Magnetization a set of MRI scans are generated with tag-lines distributed over the walls of the heart. As the heart moves, these tag-lines will move accordingly. Active contours or snakes are then used to extract the tag-lines from each MRI image, and the motion of the tag-lines determined. Laplacian smoothing splines are then used to estimate the displacement of points between the tag-lines. The strain experienced through out the heart is then a simple function of the associated displacement. Regional strain analysis is of vital importance in diagnosing different forms of heart disease, such as myocardial infarction or ``heart attack''. The method presented in this paper makes the analysis of cardiac strain feasible