NOW AVAILABLE WITH PET: A new imaging scanner that combines the functional analysis of PET with the positioning power of MRI will soon help clinicians better detect tumors, among a number of other possible uses.
© ISTOCKPHOTO/BERNHARD LELLE

Researchers this week announced a new, faster way of imaging inside the body that could detect tumors more quickly and lead to earlier treatment. Scientists from the University of Tübingen in Germany report in this week's Nature Medicine that they were able to locate and monitor tumor growth in mice with a scanner they developed that combines positron emission tomography (PET) and magnetic resonance imaging (MRI)—and said they were optimistic it could be ready to use in humans within three years.

PET technology determines how well organs and other tissue are functioning based on blood flow and the amount of nutrients, such as oxygen or glucose, that they are using. PET images help to identify an illness or injury—and the extent of a disease such as cancer. Patients are given radioactive tracers (via an IV or inhaled as a gas) that send out signals, which are picked up and deciphered by the PET scanner. MRI uses a powerful magnetic field, low intensity radio-frequency pulses, and data-processing software to create detailed images of soft tissue, muscles, nerves, fat and bones.

"Combining PET and MRI shows anatomical changes by MRI and the functional information by PET," says study co-author Bernd Pichler, a radiologist at Tübingen. In the case of tumors, for instance, an MRI can find one hidden in tissue, and the PET scanner can determine whether it is malignant and growing.

Researchers found that images of colon tumors in mice captured on the new scanner were as clear as those captured separately on traditional MRI and PET scans. The new machine allows physicians to view tissue in detail and gauge its health simultaneously. It is being touted as a replacement for many traditional x-rays, offering both greater precision and less radiation exposure. Pichler says that in some cases, however, computed tomography (CT) scans, which differentiate between muscle and bone, will still have to be used.

He says the team is now trying to adapt the technology for use on humans, which should be ready for routine applications within three years. "We have a prototype human PET–MRI in Tübingen," Pichler says, "but this is not as mature as the animal system yet."

A team of researchers at the University of California, Davis, announced its own version of the combo scanner earlier this month in Proceedings of the National Academy of Sciences USA.

"After many years, two groups have managed to make it happen," says Simon Cherry, a biomedical engineering professor at U.C. Davis, who calls the race to develop the machine a tie. "The emphasis now shifts from 'Can it be done?' to 'What are we going to do with a combined instrument that you can't do with the separate technologies?'"

Cherry says the scanner will help diagnose and treat diseases as well as determine whether certain drugs are working by watching how they travel in the body. In addition, he says, it will enable researchers to observe stem cells as they mature into different body tissues, providing new clues about their therapeutic potential.