The Need For Speed
Technological advances shorten MR testing times...
With CT and other studies that involve ionizing radiation, the Holy Grail is to reduce dose while still producing quality images. With MRI, it's shorter scans that are tolerant of patient motion. The good news is MR researchers and manufacturers have been moving swiftly in that direction and with much success.
Thanks to advances in technology and computing power, researchers and clinicians have found ways to speed scan times, including by making patients more comfortable and sampling less. In some cases, they have been able to reduce scans that previously took up to an hour to less than 10 minutes. The less time an adult or child has to spend in the MR scanner, the better.
"What's been revealed is that patients can only tolerate so much," says Chip Truwit, MD, FACR, chief of radiology for Hennepin Healthcare in Minneapolis and chief innovation officer for Upstream Health Innovations, Hennepin's innovation hub.
When MRI first became widely available in the 1980s, a patient undergoing a study would have to lie inside the scanner bore for at least 45 minutes and often longer than an hour. It was hard for patients to lie still for that long. When patients move, it can cause image artifacts and make a repeat exam necessary, Truwit says.
The shorter the scan time, the more comfortable the patients. And the more comfortable patients are, the less likely they will move, says Lawrence Tanenbaum, MD, FACR, vice president, medical director east region, and director of CT, MR, and advanced imaging for RadNet Inc. According to a study published in the Journal of the American College of Radiology in 2015, one in five MR exams has to be repeated because of patient movement. The study also found that rescans due to motion artifacts cost institutions an average of $592 per hour—as much as $115,000 per scanner, per year.
The motivation to reduce MRI scan times for children is even greater, says Shreyas Vasanawala, MD, PhD, who specializes in MRI at Stanford University. Children often have to be sedated if they are to lie still inside the tube. "If you can shorten scan time, you may be able to avoid anesthesia altogether, and, even if you can't, it's a shorter time they have to be under anesthesia, so it's better for them," Vasanawala says.
Faster MR exams also have financial benefits, which are especially important in today's "economically challenging times," Tanenbaum says. With its Philips Ingenia Elition MR Scanner, RadNet has been able to reduce its scheduling time for MRs to about 30 minutes per patient, down from 45 to 60 minutes. Tanenbaum sees further reductions as the technology and techniques continue to advance.
"Compressed sensing has reduced our already-concise routine imaging scan times from 30% to 50% across the board," Tanenbaum says. "This may allow scan slots of 20 minutes and an even more comfortable experience for patients." Shorter scan slots bring the opportunity to scan one-third more patients each day, he says.
Multiple Approaches Researchers and manufacturers have developed a number of different ways to achieve faster scans without sacrificing image quality. Some involve getting the patient to relax more. Others include improvements in the planning, scanning, and processing of exams, and some involve machine learning and neural networks to reduce the number of sequences required to create quality images of the organ or region of interest.
One way to help patients relax is to use music and videos that distract them from the overall unpleasant exam experience. This is not a new idea. "Music systems that allow the patient to listen to their choice of music have been around for a while," Tanenbaum says, but the early systems were cumbersome and "mostly collected dust in the corner" because technologists were too busy dealing with other aspects of the scan, and they neglected to offer them to patients. Improving the ambient technology and making it more user friendly has greatly increased its use, he says.