MRI imaging method and apparatus

Abstract

A method of magnetic resonance imaging for enhanced imaging, especially of small features or interfering tissue structures, and applicable to collateral vessels, such as neovascularization in a tumor or collateralization of the cardiac wall, as well as to tissue with impaired perfusion. The method creates a spatial hybrid image by arranging two or more magnetization conditions that evolve differently in various tissues of the region, and coordinating the gradient preparation/signal collection with a signal evolution in particular tissues. Transformation of the collected magnetic response data then forms a single image, and the hybrid contrast mechanisms suppress interfering effects or provide enhanced image data for particular structures in the field of view. A preferred practice of the method applied to a beating heart establishes a magnetization state of circulating blood and applies a pulse sequence to image the heart with T.sub.2 * contrast followed by T.sub.1 contrast. Higher spatial frequencies are collected before the lower spatial frequencies, and the combined set of collected data are transformed to yield an MRI image showing heart wall tissue with enhanced T.sub.2 * contrast and the ventricle with T.sub.1 contrast. This process eliminates the dominant T.sub.2 image blackout when the ventricle fills with a susceptibility agent, and also introduces a geometry-dependent flare to enhance the signal from the collaterals despite the small volumes involved. The technique effectively distinguishes a number of interfering or confounding effects to effectively display evolving collateralization as well as better developed systems wherein the extent of collateralization has effectively replaced the circulation of an occluded vessel.

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