Siemens unveils plans for MR/PET hybrid

Later today Siemens Medical Solutions will describe at the International Society for Magnetic Resonance in Medicine meeting its efforts to develop and market a hybrid MR/PET scanner. The company is refining a clinical prototype scheduled for installation at Massachusetts General Hospital by the end of this year.

Other alpha systems will be deployed at clinical sites as yet undetermined before the company goes into production with a commercial system by the end of 2007.

The first product, modeled on the MGH prototype, will be a head-only scanner, with a PET insert built for placement into the gantry of a 3T scanner. About 18 months after the release of this product, Siemens plans to introduce a whole-body PET scanner that will fit into a wide-bore MR system, likely the 1.5T Espree.

The advantages will include the elimination of registration and postprocessing issues encountered when data from separately done MR and PET studies are fused, according to Jeffrey M. Bundy, Ph.D., Siemens' director of MR R&D. MR will also be used for PET attenuation correction, much like CT is used for this purpose in the current breed of PET hybrids.

Early studies done at MGH will probably focus on Alzheimer's disease, according to Bundy. This will be an increasingly important issue as the U.S. population ages.

The new type of hybrid may provide benefits from the combination of PET specificity and MR resolution, particularly in soft tissue. The clinical advantages may not be entirely clear, however, for several years, he said.

Siemens is pursuing MR/PET with guidance from its advisory groups. The technology will evolve along with the development of new biomarkers and tracers in research at Siemens and its luminaries, Bundy said.

"This is part of a trend in healthcare that calls for the bringing together of different modalities and technologies," he said.

The price of doing so will be high. Just the PET insert for head scanning could run $1.8 million, according to Bundy, who noted that Siemens is planning to use its most advanced detector technology. The whole-body PET insert will cost end users much more. Still to be factored in for a head or body hybrid is the MR scanner and the cost of interfacing MR and PET.

For the time being, near-term engineering challenges are dominating discussions at Siemens. One is building the PET component of the dedicated head prototype as a removable insert that will contain the PET detector, and another is making a high-performance gradient coil optimized for neuro studies.

"The objective is to get to where the insert can be wheeled in and placed in the MR scanner or taken out in a reasonable time frame," said Nancy Gillen, vice president of MR.

Siemens engineers are shooting for 30 minutes. This will allow clinical sites to use the MR scanner for routine studies, as well as for MR/PET research, she said.

MR may ultimately provide vascular landmarks for interpreting PET-identified hot spots. The combined data sets would serve not only to differentiate benign from malignant lesions but might allow exact presurgical planning, Bundy said. MR/PET systems using radiotracers designed to allow plaque imaging might also be helpful in assessing peripheral vascular disease.