Five frames better than one: MRI technique improves artery wall images

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A newly developed multiframe MRI technique has been shown to increase the success rate of obtaining coronary artery wall images compared with conventional single-frame imaging, according to a study published in Radiology.

The technique, called time-resolved acquisition of phase-sensitive dual-inversion recovery (TRAPD), could be used to detect the early stages of coronary artery disease (CAD), according to authors Khaled Z. Abd-Elmoniem, PhD, of the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases, and colleagues.

“Obtaining a reliable and accurate image of these vessels is very important because thickening of the vessel wall is an early indicator of atherosclerosis,” Abd-Elmoniem said in a release. “We currently have no reliable way to noninvasively image [CAD] in its early stages, when the disease can be treated with lifestyle changes and medications to lower cholesterol.”

TRAPD involves the capture of three to five cine phases, which are reconstructed to produce an image free of blurring, explained the authors.

To compare the success rate of the TRAPD method with that of single-frame imaging for assessing vessel wall thickness, Abd-Elmoniem and colleagues imaged a total of 38 subjects, 26 patients with at least one CAD risk factor and 12 healthy controls matched to patients by body mass index. All subjects underwent both a single-frame MRI scan and a TRAPD scan on a 3T MRI.

The authors reported that the success rate for obtaining a usable image with the TRAPD method was 90 percent, an improvement over the 76 percent success rate for single-frame imaging. The method also demonstrated a greater ability to detect significant differences between wall thickness measurements of CAD patients and healthy controls. Intraobserver, interobserver, and interexamination agreement for wall thickness measurement were 98 percent, 97 percent, and 92 percent, respectively.

“The extra frames provided an additional opportunity to compensate successfully for single-frame section timing or mispositioning due to residual or unpredicted cardiac and chest wall motion,” wrote the authors.

Abd-Elmoniem and colleagues noted a few potential limitations of the TRAPD method. The minimum section thickness in the researchers’ protocol was 8 mm, which could lead to volume-averaging artifacts. There is also a limited 2D coverage per pass with the TRAPD sequence, but the authors explained this enables a short acquisition time, permitting data to be acquired at multiple sites.

Unlike blood tests to measure cholesterol, the thickness of coronary artery walls is a direct measure of early-stage CAD, and the results of the current study, if validated by additional research, suggest that MRI could be used as a screening tool for those at risk for the disease, according to Abd-Elmoniem.