Radiology: MRI can monitor evolution of carotid vessel wall volume

MRI can help monitor vessel wall volume changes over time and identify factors that contribute to changes, according to a study in this month’s issue of Radiology. In addition, researchers found that patients not receiving statin therapy had a faster increase in vessel wall volume changes.

In a multicenter analysis, Loïc Boussel, MD, PhD, from the department of radiology at the University of California, San Francisco, and colleagues sought to estimate the annualized rate of progression of vessel wall volume in the carotid arteries by using MRI and also to establish the percentage of these exams that have acceptable image quality.

The study included 160 patients with greater than 50 percent narrowing of the diameter of the carotid artery who were recruited at six centers for prospective imaging of the carotid arteries at baseline and one year later by using high-spatial resolution 1.5T MRI. The researchers excluded studies with unacceptable image quality.

They measured the quantitative changes in atheroma volume on unenhanced T1-weighted images. A multiple linear regression analysis was used to correlate progression with several clinical factors, including statin therapy.

According to the authors, all 160 patients completed both baseline and follow-up studies. Of these studies, 67.5 percent were deemed to have image quality that was acceptable for quantitative analysis. The causes of rejection were motion (46 percent), deep location of the carotid artery (22 percent), low bifurcation of the carotid artery (13 percent) and “other” (19 percent).

Boussel and colleagues reported that the mean annual change in vessel wall volume was 2.31 percent (standard deviation). At one-year follow-up, they found vessel wall volumes in patients not receiving statin therapy had increased faster compared with those in patients receiving statin therapy: 7.87 percent vs. 1.14 percent, respectively.

The authors noted that the interobserver error (11.5 percent) for measuring luminal volume was “relatively large, and change in luminal volume was not significantly different from zero.”

Based on their findings, the researchers concluded that the evaluation of results of a multicenter study indicates that quantitative evaluation of the progression of volume of extracranial carotid vessel walls is feasible with 1.5T MRI, despite limitations due to patient motion or habitus.

However, they said that three issues should be followed up in larger and longer multicenter studies:
  • The temporal evolution of plaque: Multiple measurements over a longer period are required to determine whether this is indeed slow and irregular and how strongly it is moderated by concurrent medical therapies.
  • Populations with stenosis of less than 50 percent: Little is known about the rate of change in disease for patients with stenosis of less than 50 percent.
  • Statin therapy: Future studies should carefully account for the dose and duration of statin therapies wherever possible.

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