Techniques of fast MR imaging for studying the cardiovascular system

Abstract

The use of Magnetic Resonance Imaging (MRI) in cardiovascular applications has developed with the introduction of new techniques for the control of artifacts caused by movement and flow. Indeed, until the last decade, the acquisition of cardiac MR images was suboptimal because of problems of compensation in respiratory movement; nowadays, instead, excellent images can be acquired by simply having the patient hold its breath. Alternatively, excellent cardiac images can be acquired even with free breathing by relying on the so-called navigator technique. There are a number of techniques available, the choice spanning from Gradient Echo (GRE) synchronized with ECG, or the more sophisticated segmented breath-hold and navigator techniques that produce excellent quality images in a short time (seconds) and practically void of artifacts if the patient is collaborative. The advanced MRI machines in use today also reflect great developments in hardware: very quick gradient activation and disactivation times (slewrates), high sensitivity radiofrequency coils, and very high gradient amplitude allow numerous clinical evaluations in the cardiovascular setting. An MR exam today makes it possible to evaluate the morphology of the heart, perfusion, myocardial viability, flows and coronary anatomy. This chapter will briefly illustrate the basic concepts of fast MR image formation [1, 2], which are those that can be applied to the acquisition of cardiovascular images.