Magnetic Resonance Imaging

The development of magnetic resonance imaging (MRI) has been one of the great medical advances in the twentieth century, enabLing the creation of 3D images of the human body with excellent soft tissue contrast and spatial resolution. MRI is noninvasive and does not rely on harmful ionizing radiation. From its early appLications in the diagnosis of brain pathology such as stroke, today it is used widely to diagnose and monitor disease processes throughout the body, giving new insights into cancer, heart disease, bowel disorders, and the musculoskeletal system. Advances in scanner hardware, with increasing magnet strength, novel pulse sequences, and improved imaging coils, have greatly enhanced image quaLity and intrinsic structural contrast. Furthermore, new areas of research into MRI contrast agents and molecular imaging have emerged, which enable pathology to be seen with even greater clarity. In this article, we first explore the history and basic principles of MRI - how the MR signal originates biologically and may be exploited for imaging. We then go on to discuss MR contrast agents, examining the role of the paramagnetic contrast agents in common cLinical use. We then move to introduce advanced molecular MRI techniques such as advances in targeted and genetic reporter contrast agents. Finally, we look at MRI's role in complementing histopathology, discussing MRI for noninvasive imaging of deLicate and postmortem samples and the use of MR to image at a microscopic scale.