By Adityarup “Rup” Chakravorty
How long can you stay absolutely still? Thirty seconds? A couple of minutes?
How about ten minutes?
Individuals undergoing a magnetic resonance imaging (MRI) scan often need to minimize movements for up to 10 minutes at a time to maximize scan quality. That can be challenging for many people.
In fact, between 10 to 15% of all MRI scans need to be redone because of excessive movement during the scan. Too much movement can cause artifacts – artificial observations introduced during the scanning process. The percentage of MRI scans that need to be redone may be even higher for young children and individuals with disabilities.
Researchers at the University of Wisconsin-Madison have developed a motion-correction strategy that can effectively minimize artifacts in brain images caused by excess motion during MRI scans.
“I believe this strategy will greatly enhance the ability to do neuroimaging studies in young children and individuals with intellectual and developmental disabilities,” says Andrew Alexander, senior author of a recent study about the strategy published in Radiology.
MRI is used in both clinical and research contexts. Investigators at the Waisman Center, and other institutions, use MRI to image the brain and other organs for various research projects, including ones focused on human development, autism, and Alzheimer’s disease, among others.
In both clinical and research settings, MRI is popular because it is non-invasive and does not use X-rays or radioactive material. However, if individuals being scanned are unable to stay still and confine their movements to less than a millimeter – the images can contain artifacts that render them unusable.
Currently, individuals who may have difficulties staying still during medical MRI scans are often sedated. But “sedation comes with its own set of risks and adverse effects,” says Alexander, who is a professor of medical physics at UW-Madison and a Waisman Center researcher. Side effects of sedation can include nausea and disorientation. Recent research has also shown some long-term negative effects on developing brains.
In addition, “sedation is not allowed for research studies involving MRI scans,” says Steven Kesckemeti, lead author of the new study and an assistant scientist at the Waisman Center.
So Kesckemeti, Alexander and their colleagues developed a technique called MPnRAGE, which can compensate for movements made during MRI scans and maintain the usability of the resulting images.
In the study, MRI scans processed using the MPnRAGE system were consistently ranked as having higher quality compared to unprocessed scans. Several scans that were considered ‘unusable’ before MPnRAGE processing were subsequently categorized as ‘good’ by reviewers.
“A key advantage of MPnRAGE is that it works for scans that contain motion artifacts as well for scans that don’t,” says Kesckemeti. That’s important because some other correction strategies work only on scans with motion artifacts and can actually reduce the quality of images that don’t need corrections.
The cornerstone of MPnRAGE is imaging that incorporates both low and high frequency information. “The low frequency information is what helps us correct for motion artifacts, while having the high frequency information allows us to generate high-resolution, high-quality images even after correcting for motion,” says Kesckemeti.
Researchers from other institutions have started reaching out to Alexander and Kesckemeti about incorporating MPnRAGE into their research workflow. “Right now this strategy is streamlined for General Electric MRI machines, [which is what the Waisman Center uses],” says Alexander, “but there’s no reason why the system wouldn’t work with other MRI machines.”
Funding for the study was provided by the National Institutes of Health Clinical Center (P50 MH100031, R01 MH097464, R21 EB018483, R21 HD078119, R21 NS091733, U01 AG051216) and the Waisman Center from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (U54 HD090256).