39 - MRI of the Brain

Summary

In recent years, there have been tremendous advances in the field of radiology, specifically in radioimaging. The development of an accurate way to visualize structures in the body has improved the diagnosis of patients and has allowed for less invasive methods in their evaluation. MRI represents a breakthrough in medical diagnostics and research, and is becoming especially valuable in the evaluation of neurological and musculoskeletal pathology.

The field of MRI is still evolving and continually improving. Although its role as the modality of choice in the ED remains limited, MRI remains indispensable in the evaluation of brain tumors, strokes, and chronic demyelinating disorders, including multiple sclerosis.

In 1946, two scientists working independently on nuclear magnetic resonance (NMR) research laid the groundwork for the future development of MRI. Dr. Felix Bloch working at Stanford University, and Dr. Edward Purcell from Harvard University, simultaneously accomplished the first successful NMR experiment. In 1952, they were both awarded the Nobel Prize in Physics for their work in the study of the composition of chemical compounds.

PRINCIPLES OF MRI

The fundamental concept of MRI is based on resonance; specifically, nuclei of certain atoms, most commonly hydrogen atoms, resonate when placed in powerful magnetic fields. When radiofrequency energy, or radio waves, is projected toward the atoms, the nuclei absorb some of the energy, thus becoming “excited.” Subsequently, the nuclei “relax” and return to their previous energy level, thereby emitting their own radio signals.