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Heat is a formidable enemy in MR and CT chiller design

por John W. Mitchell, Senior Correspondent | September 09, 2015
Bernie Loeffler,
executive director of
facilities for the
University of New Mexico
Health Sciences Center
stands on a cooling tower
From the September 2015 issue of HealthCare Business News magazine

For Bernie Loeffler, executive director of facilities for the University of New Mexico Health Sciences Center, imaging cooling comes down to a basic value proposition. “Think of what happens when you have your laptop in your lap for too long — it gets hot,” he said. “The same thing happens with a CT or MRI. All those moving parts and pieces work hard to create an image. That creates heat. It’s my job to get rid of that heat.” With an older facility — some of the original UNM buildings date back to the 1950s — and summer temperatures that routinely hit over 100 degrees, Loeffler preaches the gospel of redundancy — building in a backup cooling loop if the primary loop fails. All of the medical center’s four MRIs and three CT scanners are on double loop-chilled water systems backed up with emergency power as well as the hospital’s stand-alone emergency diesel generators. The medical center relies on a wide array of manufacturers to meet their CT and MRI needs, including Siemens, Phillips and GE.

“You can’t just think about getting water to these units, you also have to get power to the units to run the chiller pumps in any kind of situation. We have power outages quite a bit,” said Loeffler, who speaks about system engineering with all the gusto of Scotty, the engineer from the TV series “Star Trek.” He said that in the eight years he has been at UNM they have doubled the chiller water capacity, which is just as vital for the IT functions that run the imaging computers and software as it is for the equipment itself.

In this time of rapidly advancing technology, MRI and CT have improved the lives of millions of patients. But as Loeffler notes, the laws of physics are also hard at work: nearly every milestone in imaging capability creates a corresponding increase in residual heat. Heat can cause these highly sophisticated machines to produce poor image quality and even fail with a patient on the table. A big job for imaging manufacturers and engineers is to dissipate growing heat loads to ensure outcomes and safety.

Turner Hansel, vice president at Filtrine Manufacturing Company, which makes medical chillers, can put a number on that heat. “An MRI on stand-by generates 28,000 BTUs of heat. As soon as a scan starts, that heat load goes up to over 200,000 BTUs, nearly tenfold,” he said. Hansel said it’s their job to engineer a chiller so a doctor, patient or technician never has to think or hear about imaging chillers undergoing downtime. But that doesn’t mean hospital leaders should not be thinking about chillers.

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