Silent alternatives to conventional MRI scans are showing promising results, but reducing noise in MR angiograms (MRAs) is proving a more difficult task, a team of Stanford University scientists reported in the American Journal of Roentgenology this week.

While traditional imaging techniques like MRIs are important diagnostic tools, they’re often also sources of anxiety, lead author Samantha J. Holdsworth, PhD, and colleagues said.

“The process of obtaining an examination can be long, loud and uncomfortable for patients, who may struggle to remain still in an enclosed space during the examination,” the authors wrote. “The high noise levels associated with MRI further exacerbate the distress that children and patients with claustrophobia, tinnitus or sensitive hearing may feel.”

MRIs are associated with as much as 130 decibels of gradient noise, the paper stated, which has prompted the introduction of several noise-dampening techniques into the procedure room. Researchers have tried mechanical solutions like placing MRI gradient coils in a vacuum and sequence solutions like adjusting and optimizing gradient movements, but clinicians pay a price for that silence. While reducing sound in conventioning imaging devices is possible, scanning typically becomes less efficient and more blurry.

GE Healthcare’s Silent MRI Scan is one that has successfully reduced noise levels, since it acquires free induction decays rather than echoes, like a traditional MRI does. Critics have complained, though, that because of a longer readout time, the Silent device produces unclear images.

In an effort to test the efficacy of silent versus conventional imaging techniques, Holdsworth and her co-authors compared the results of Silent T1-weighted MRIs and unenhanced MRAs against conventional sequences of the same techniques in a population of 40 older patients.

All participants had suspected brain metastases, Holdsworth et al. wrote, and images were reviewed by a panel of three neuroradiologists, who reviewed the scans blindly and rated a handful of measures of image quality on a five-point Likert scale.

The researchers found Silent scans to generally be less insightful; when compared to T1-weighted MR images, ratings were slightly lower for Silent images in all cases except for when it came to diagnostic confidence. More lesions were detected on conventional images, they reported, but the differences weren’t statistically significant, and agreement was seen in 88 percent of cases.

In nearly half of all cases, T1-weighted scans were deemed equivalent to Silent scans, but reviewers still preferred conventional images.

Findings were less successful when it came to MRAs, the authors wrote. Conventional MRA images were ranked much more highly than Silent ones in all aspects of image quality metrics, and were strongly preferred to Silent scans. Reviewers preferred the conventional technique in 69 percent of cases, while images were rated equally in 27 percent of cases and Silent images were preferred in just 4 percent. There were even cases of reduced vessel caliber, vessel irregularities and absent vessels emerging as a result of the Silent technique, Holdsworth and her team said.

“Silent imaging could provide a reasonable alternative to conventional scans,” the researchers wrote. “We did not come to the same conclusion regarding the Silent MRA method, which had multiple suboptimal features that limited image interpretation, such that significant improvements are required before it can be recommended in a clinical population.”