PET/MRI Raises Eyebrows and Expectations

Greg Freiherr


May 06, 2011

In This Article

More Imaging Detail and Less Radiation

PET/MR is medicine's latest confection, combining PET with MR in much the same way in which PET has been paired with CT. However, this latest twist on hybrid imaging promises to do better in some cancer applications than PET/CT -- and with much less radiation to the patient. PET/MRI may even capitalize on imaging opportunities in cardiology where PET/CT has fallen short.

In the functional assessment of cancer, PET's proven value is complemented by MRI's acumen for soft-tissue imaging. The combination produces striking images of the brain, breast, and prostate, as shown at the 2010 annual meeting of the Radiological Society of North America (RSNA) in Chicago, Illinois (Figure 1). This hybrid may be even more sensitive than PET/CT at detecting liver metastases, according to published research.[1]

Figure 1. Philips Healthcare Ingenuity TF PET/MRI (Andover, Massachusetts) scanner visualizes breast cancer in this fused PET/MR image shown at the annual meeting of the Radiological Society of North America (RSNA) in 2010. Image courtesy of University of Geneva, Geneva, Switzerland

Where PET/MRI will land in the clinical mainstream is difficult to say, according to Zahi A. Fayad, PhD, a pioneer in the use of PET/MRI. Well-established technology, such as the decade-old PET/CT, is hard to displace.

"I think PET/MRI will initially take over for certain indications where there is a need to improve," said Dr. Fayad, Director of the Translational and Molecular Imaging Institute at Mount Sinai Medical Center in New York City. Among these "low-hanging fruits" are head and neck, brain, and prostate cancer applications, he said, as well as cardiovascular uses, such as the characterization of plaque, an area Dr. Fayad has been exploring.[2]

"Cardiovascular imaging has not been done so much with PET/CT, so here we would not be replacing it so much as just penetrating this area," Dr. Fayad said.

A big advantage of PET/MRI is its greatly reduced radiation burden. By eliminating the radiation coming from CT, the overall patient exposure to ionizing radiation is half the radiation dose of PET/CT, say experts. This advantage should appeal especially to pediatric oncologists.

"Decreased radiation dose is a major benefit," said A. Gregory Sorensen, MD, Professor of Radiology at Harvard Medical School, Boston, Massachusetts, and one of the first to use a prototype PET/MRI brain scanner developed by Siemens. "There are populations, such as children, in whom this advantage may outweigh every other advantage."


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