A so-called "trimodality" system, combining PET, CT and MRI, could help further research in the clinical uses of PET-MR.

Currently being installed at a Hong Kong hospital, a pair of scanners could let radiologists compare PET-CT and sequential PET-MR reads to determine the best uses for the new modality.

"That's really the key piece: to establish where one is better than the other," Vivek Bhatt, general manager of PET with GE Healthcare, which makes the devices, tells DOTmed News.

Considered by many to be the first new modality in a decade, PET-MR has plenty of potential: swapping out the CT with MR could allow attenuation correction for PET without exposing patients to the ionizing radiation generated by the CT scanner. Plus, MRI's ability to image soft tissue could make it superior in detecting certain cancers. But Bhatt says work still has to be done: "We're trying to answer to give a very clear clinical assessment of where it'll be used in the long-term."

GE Healthcare, headquartered in Waukesha, Wis., has not released a standalone PET-MR system of its own, but two of its rivals have.

Siemens Healthcare was the first to bat in the U.S., with its Biograph mMR device, an integrated PET-MR system capable of simultaneous imaging, getting Food and Drug Administration clearance in June. (It also picked up a design award this year.) Philips Healthcare also has one in the works, the Ingenuity TF PET-MR, featuring two separate units attached by a rotating patients' table. It's received European marketing approval, but is not available in the U.S. yet.

As for clinical evidence, there have been some promising early studies. A report from University of Munich researchers at Society of Nuclear Medicine's annual meeting in June, using the Siemens system, found PET-MR scans do about as well as PET-CT scans for attenuation correction and detecting lung, liver, spleen and bone lesions.

But many doctors think more research is needed to better understand the new technology -- and this is where the new installation could provide some help.

Headed for Hong Kong

Receiving the device trio is Hong Kong Sanatorium & Hospital, a private, 400-odd-bed, 89-year-old hospital located in Happy Valley, Hong Kong.

The system involves a GE Optima MR450w wide-bore 1.5-Tesla and the Discovery PET-CT 600. They're kept in separate rooms; in addition to the research, the hospital plans on using the PET-CT scanner and the MRI scanner independently for the normal clinical work that pays the bills. But when both are used together, the patient lies on a table that can interface with both products, without changing the patient's position, Bhatt says.

The main aim of the project is to compare PET-CT exams, with a PET and MR co-registration, Bhatt says. With the PET-CT baseline, they can start to figure out what the PET-MR images add. They can also try to answer specific questions: do you need simultaneous imaging to get the real advantage? Is the main benefit dose savings? What studies does it perform best at?

"Where is PET-MR better than PET-CT?" asks Bhatt. "Is it about dose, pediatrics, a specific organ?"

Although the Hong Kong installation isn't finished, researchers already know what to expect. Actually, this isn't the first such project. Last fall, a similar PET-CT-MR combo was delivered to the University Hospital Zurich in Switzerland. Already, 400 patients have gone through that system, Bhatt says. "We got a lot of great clinical feedback," he observes.

The results of the early work were also presented at SNM's June meeting, and more findings will be shared this fall, at the 2011 annual congress of the European Association of Nuclear Medicine in Birmingham, UK.

For instance, in a study led by D.W. Crook that will be presented Oct. 17 at the meeting, the researchers found PET-MR tended to outperform PET-CT in characterizing lesions in the liver, according to the abstract posted online. "While requiring confirmation, these results nonetheless suggest the potential utility of integrated PET-MR over PET-CT in the abdomen," the researchers wrote.

As the Zurich team continues their studies, Bhatt says GE is working with other sites planning similar installations. But he can't reveal their names until the projects are further along.

"There are a lot of clinical questions that need answering," he says.