MRI evaluation of myocardial perfusion without a contrast agent using magnetization transfer

We propose a new magnetic resonance imaging (MRI) technique that is sensitive to myocardial tissue perfusion that obviates the use of an extrinsic contrast agent. Significant advantages of such a technique are that it avoids accumulation of contrast agent when repeated studies are performed on the same subject and that it is completely noninvasive. The method makes use of a combination of magnetization transfer (MT) and T1sat (measured spin-lattice relaxation time in the presence of MT) weighting. In this Communication, we present observations from experiments with an isolated rat heart model that demonstrate increase of MT-weighted signal intensity and T1sat with flow. Also included are data showing that these effects can be made synergistic for enhancing the sensitivity to perfusion. We have observed about a 3% change in MT-weighted intensity and up to 10% change in MTT1sat-weighted intensity for a change of 1 ml/min in global flow rate.