A ONE-DIMENSIONAL VELOCITY TECHNIQUE FOR NMR MEASUREMENT OF AORTIC DISTENSIBILITY

A technique is presented for rapidly and noninvasively determining aor tic distensibility, by NMR measurement of wave velocity in the aorta. A two-dimensional NMR selective-excitation pulse is used to repeatedly excite a cylinder of magnetization in the aorta, with magnetization r ead out along the cylinder axis each time. A toggled bipolar flow-enco ding pulse is applied prior to readout, to produce a one-dimensional p hase-contrast flow image. Cardiac gating and data interleaving are emp loyed to improve the effective time resolution to 2 ms. Wave velocitie s are determined from the slope of the leading edge of flow measured o n the resulting M-mode velocity image. The technique is sensitive over a range df distensibilities from 10(-6) to 10(-3) m s(2)/kg. The aver age value in the descending thoracic aorta in seven normal subjects wa s found to be 4.8 x 10(-5) m s(2)/kg, with a significant inverse corre lation with age.