· Running the Numbers
· MRA Accurately Detects Blocked Arteries?But Is It Feasible?

Running the Numbers

Researchers at the Mount Sinai Medical Center, New York City, injected mice with a synthetic material that tracks down and attaches to macrophages embedded in the arterial walls; 24 hours after injection, MRI tests showed that measuring and assessing macrophages in the arterial walls yielded a 79% increase in detection, compared with the initial baseline images taken the day before. This tool could help clinicians identify patients at risk for heart attack and stroke. “Our study results clearly show that detecting and measuring macrophage levels using MRI could be an effective and noninvasive screening tool for what’s becoming one of the leading public health threats worldwide,” explained Zahi A. Fayad, PhD, director of the Eva and Morris Feld Cardiovascular Imaging Research Laboratory and a professor of radiology and medicine at Mount Sinai. Fayad was lead author of the study, published in Proceedings of the National Academy of Sciences.1 The next step is to test the approach in larger animals before moving to human clinical trials. Fayad believes the technique could become a standard clinical practice in the next few years.


  1. Amirbekain V, Lipinski MJ, Briley-Saebo KC, et al. Detecting and assessing macrophages in vivo to evaluate atherosclerosis noninvasively using molecular MRI. Proc Natl Acad Sci USA. 2007;104:961?966.

MRA Accurately Detects Blocked Arteries?But Is It Feasible?

Researchers at the David Geffen School of Medicine at University of California, Los Angeles (UCLA), have shown that MR angiography (MRA) is highly accurate at identifying blockages in the arteries that carry blood to the brain, according to a study in the February issue of Radiology.1 The team looked at 80 patients—44 men and 36 women—with suspected arterial occlusive disease, and compared the performance of contrast-enhanced MRA with the more widely accepted methods of multidetector CT angiography and digital subtraction angiography.

Kambiz Nael, MD

“We’re doing whole-body MR angiography at 3T,” explains Kambiz Nael, MD, research fellow and radiology resident at UCLA, adding that the study focused primarily on peripheral vascular disease (PVD). “Since PVD or atherosclerotic disease is a systemic disorder, it usually affects all other parts of the body as well. So, these patients may have a carotid problem, they may have a renal or vascular disease, and, therefore, many clinicians regard evaluation of the whole body as desirable.”

Nael notes that the system specs of the MR used by the researchers were crucial to the achieved results. “Whole-body at 1.5T is becoming very common,” he says. “A couple of centers in Germany and a couple of centers in the United States, including UCLA, are doing that. We have a multireceiver-channel, whole-body 3T MRI scanner equipped with multicoil technology, so we can distribute almost 100 coil elements over the body. The main advantage of 3T is basically the higher signal-to-noise ratio, which can be used to improve spatial resolution, reduce the acquisition time, and also reduce the amount of contrast we’re using.”

This MR angiography was obtained in 1 minute and 30 seconds using Total imaging matrix technology from Siemens Medical Solutions, Malvern, Pa.

The researchers’ findings are encouraging. “In this study, we showed that we could improve spatial resolution up to 30% with whole-body 3T, and acquisition time is definitely shorter,” Nael says. “Also, the contrast is probably 30% less compared to 1.5T.”

Nael doesn’t expect 3T whole-body MRA to become the norm overnight—liability and coverage will be major obstacles, he predicts. “It has to be done in centers where the radiologist is pretty comfortable reading whole-body MRA; otherwise, they could miss some findings,” he says. “Liability is a big deal. There are a lot of images to read with whole-body MRA—thousands of images. The other thing is the cost-effectiveness of the examination. I’m sure that at some point, the insurance companies are going to say that if we need to evaluate only PVD, they’re not going to reimburse for the whole body. It’s going to be a challenge coordinating radiologists, referring physicians, and the insurance companies.”

But with 20% to 25% of patients with PVD showing significant associated arterial disease in other regions, Nael hopes to see the procedure accepted more widely. Currently, his team is gathering more clinical data to substantiate the necessity of whole-body MRA in some cases. “In 6 months, we hope to have 200 cases and to do a more comprehensive study,” he says. “We’re getting new features on our scanner. We’re getting a moving table so that we can do real-time MRA. We’re also hoping to improve the coil quality and the number of coil elements so that we can use a higher acceleration factor. By using this multireceiver-channel, whole-body 3T MRA with multicoil technology, we’re able to acquire better spatial resolution throughout the whole vasculature.”

—C. Vasko


  1. Nael K, Villablanca JP, Pope WB, McNamara TO, Laub G, Finn JP. Supraaortic arteries: contrast-enhanced MR angiography at 3.0 T—highly accelerated parallel acquisition for improved spatial resolution over an extended field of view. Radiology. 2007;242:600?609. Available at: radiology.rsnajnls.org/cgi/content/abstract/242/2/600. Accessed March 28, 2007.