Dimensional accuracy of magnetic resonance in studies of the heart.

Magnetic resonance (MR) can provide high-resolution tomographic images of the heart at any part of the cardiac cycle. Tests on static and dynamic phantoms showed that the technique can give accurate measurements of ventricular wall thickness, cavity volume, and stroke volume. In 20 patients with angina pectoris, electrocardiographically gated MR images of the left ventricle were compared with X-ray contrast ventriculograms. There was good correlation with the anteroposterior ventriculogram, but poorer correlation in the lateral projection because of difficulty in locating the aortic valve precisely on the ventriculogram. In 20 normal subjects, left and right ventricular volumes at end-diastole and end-systole were measured by summing the areas of the cavities in multiple contiguous sections. Stroke volumes and ejection fractions were thus calculated, and the ratio of left to right ventricular stroke volume was very close to the theoretical value of 1, in all cases. In any individual volume measurement, the error was approximately 2%. MR therefore provides an accurate non-invasive method of studying cardiac dimensions and function.