Of the many applications of superconductivity that are found in this volume, there is only one with which the general population in developed countries has any major contact. I refer, of course, to magnetic resonance imaging, or as it has become generally known, MRI. By some estimates, this is a greater than $5B per year enterprise with companies in Europe, Asia and the US involved in marketing their MRI systems to the medical community. There are other biomedical applications of superconductivity that will be covered in this section, some that have been around for as long as (or even longer than) MRI has. However, for reasons that are mostly nontechnical, these other applications have had rather limited success in developing a significant market. In some instances, these markets may never develop because of continuing improvements in other technologies that are less expensive and/or that require less training of medical technicians. Yet there is one application, namely magnetocardiography, that surely will find widespread use as a diagnostic tool for routine screening of otherwise undetected heart ailments and for triage in hospital emergency rooms when patients appear with chest pain. The only caveat to this prediction is that the development of other non-cryogenic, less expensive and equally sensitive magnetometers could replace SQUID-based magnetocardiography. Nevertheless, it is the use of SQUID magnetometry that has opened the door to magnetocardiography and that has served to prove its effectiveness in numerous clinical studies
around the world. Furthermore, the introduction of closed-cycle refrigeration should make SQUIDbased magnetometry more user friendly. In the end, reliable operation and overall cost (including shielded enclosures for the non-cryogenic systems) will determine which form of magnetometry becomes universally adopted. There have been many previous attempts to preempt SQUID technology with non-cryogenic forms of magnetometry, but, thus far, SQUID systems have maintained a clear advantage for sensitivity and reliability.