Extremity Scanners and ‘Moving’ MRI MRI scanners rely on superconducting magnets to produce images of the body. However, cooling these magnets to the necessary temperatures involves immersing them in liquid helium baths, a solution both expensive (because, well, it’s helium) and somewhat ungainly. Now, the Center’s Jerry Ackerman and colleagues are fine-tuning an approach that enables portable MRI by sidestepping this need. Instead of cooling the magnet by submerging it in liquid helium, the new technology, initially developed by the company Superconducting Systems, works by replacing the liquid helium bath with a cryogenic (ultralow temperature) refrigerator. Conventional scanners already use a similar technology, called cryocooling, but only to meet a relatively small part of the scanners’ cooling needs. “The advance with the Superconducting Systems technology,” Ackerman says, “was coming up with a practical way to provide all of the cooling with a cryocooler.” So rather than relying on a rare and therefore expensive element—helium—cooling of the magnet is powered almost
entirely by readily available and comparatively cheap electricity. As a demonstration of the clinical potential of the technology, Ackerman and colleagues built an “extremity scanner” designed for imaging of patients’ arms and legs. This compact scanner is roughly four feet wide and maybe two feet deep and includes a central bore for the actual imaging and two “dummy” bores added for ergonomic reasons—so the patient can comfortably put both legs in bores rather than inserting only one leg, leaving the other to sit awkwardly outside the scanner. The extremity scanner is by no means the only potential application of the technology, though. With its compactness, its relatively low purchase cost, its small footprint, and the relatively low expense of cooling the magnet, the Superconducting Systems technology recommends itself for a host of different uses. Ackerman continues: “The technology doesn’t necessarily allow you to do things you’ve never done before. What it does do is enable you to perform the same tasks you could in a conventional scanner but less expensively and more efficiently. By extension, you may be able to provide imaging services, including high-quality head scans, in places where this previously hasn’t been possible—for example, in resource-limited areas of the developing world. “Even in places where MRI is already available, the technology provides a less expensive alternative. And because most of your body remains outside the scanner, it’s less intimidating for people with claustrophobia or others who simply don’t like going into a scanner.”
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