26 - High field magnetic resonance imaging

Abstract

On July 3, 1977, magnetic resonance imaging (MRI) was first used to acquire images of a living human. Since then, MRI has consistently provided noninvasive images of the human body and helped clinicians and scientists diagnose various pathologies and study their physiology. Contrary to the early expectations of the medical community, however, MRI did not quickly evolve into a tool for independent diagnosis of diseases and disorders. One culprit was the inherently low sensitivity caused by the low magnetic field strength of these scanners which stood at 1.5T (Tesla) for two decades. With the debut of a scanner operating at 8T in 1998, high field (HF) MRI became a reality. Today, most hospitals have 3T clinical scanners and the standard of HF research has become 7T scanners. HF scanners, which range anywhere from 7 to 11.7T, have shown potentials to examine the functional anatomy of the brain; for example, to determine parts of the brain that do functions such as thought, speech, movement, and sensation; to study the consequences of trauma, stroke, or degenerative disease on brain function; to monitor the growth of brain tumors; and to help plan radiation therapy, surgery, or other invasive treatments on the brain. To expand these capabilities, the science, engineering, and safety of these new scanners are critical issues which must be developed in parallel. In particular the role of radio frequency coils, magnetic susceptibility, and pulse sequences is prominent in this regard. In addition, HF MRI has potentials to go beyond imaging of brain and develop sensitivity for direct physiological processes, and ultimately a tool for cellular and molecular imaging. In this context, HF MRI could provide new insight into the etiology and pathophysiology of many diseases and also help expand our understanding of basic biology.