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W O'Dell

Publications and source records attributed to W O'Dell.

4 recordsLinked to original sources
PubMed2000

Left ventricular motion reconstruction from planar tagged MR images: a comparison.

Through recent development of MR techniques, it is now possible to assess regional myocardial wall function in a non-invasive way. Using MR tagging, space is marked with planes which deform with the tissue, providing markers for tracking the local motion of the myocardium. Numerous methods to reconstruct the three-dimensional displacement field have been developed. The aim of this article is to provide a framework to quantitatively compare the performance of four methods the authors have developed. Five sets of experiments are described, and their results are reported. Instructions are also provided to perform similar tests on any method using the same data. The experiments show that some characteristic properties of the methods, such as sensitivity to noise or spatial resolution, can be quantitatively classified. Cross-comparison of performances show what range values for these properties can be considered acceptable.

Animals↗
PubMed1991

Unique strain history during ejection in canine left ventricle.

Understanding the relationship between structure and function in the heart requires a knowledge of the connection between the local behavior of the myocardium (e.g., shortening) and the pumping action of the left ventricle. We asked the question, how do changes in preload and afterload affect the relationship between local myocardial deformation and ventricular volume? To study this, a set of small radiopaque beads was implanted in approximately 1 cm3 of the isolated canine heart left ventricular free wall. Using biplane cineradiography, we tracked the motion of these markers through various cardiac cycles (controlling pre- and afterload) using the relative motion of six markers to quantify the local three dimensional Lagrangian strain. Two different reference states (used to define the strains) were considered. First, we used the configuration of the heart at end diastole for that particular cardiac cycle to define the individual strains (which gave the local "shortening fraction") and the ejection fraction. Second, we used a single reference state for all cardiac cycles i.e., the end-diastolic state at maximum volume, to define absolute strains (which gave local fractional length) and the volume fraction. The individual strain versus ejection fraction trajectories were dependent on preload and afterload. For any one heart, however, each component of absolute strain was more tightly correlated to volume fraction. Around each linear regression, the individual measurements of absolute strain scattered with standard errors that averaged less than 7% of their range. Thus the canine hearts examined had a preferred kinematic (shape) history during ejection, different from the kinematics of filling and independent or pre-or afterload and of stroke volume.

Animals↗
PubMed1990

Echo planar imaging of isolated perfused rat hearts at 4.7 T: a comparison of Langendorff and working heart preparations.

The implementation of echo planar imaging at 4.7 T is demonstrated using a homebuilt gradient and radiofrequency assembly. The application of such a technique to the study of the isolated perfused rat heart is demonstrated. Langendorff and working heart perfusion preparations are compared and changes in the left ventricular volume shown are to be much larger in the working heart preparation. Such a methodology is expected to provide a useful model for the study of cardiac function and dynamics in the normal and diseased states under controlled perfusion conditions.

Animals↗