New specialty may rise to control molecular imaging

Industry pundits stay positive but speculative

Equipment vendors see enormous sales potential in molecular imaging. Executives at GE Medical Systems believe this emerging market could eventually account for billions of dollars in annual equipment sales. Visionaries at Siemens have even coined a new term to address these potentials: "theranostics," defined as molecular diagnostics integrated with pharmacogenomic therapy. But much remains to be determined.

While molecular medicine appears certain to transform healthcare, it has not yet been determined how early disease detection at the molecular and genetic level translates into better patient care. Nor is it clear which modality will take the lead position. Although MRI and nuclear medicine appear best positioned for that role, neither by itself may win out.

The uncertainties inherent in molecular imaging run deep. At the core are questions about which medical specialty will control its development. Radiology is only one candidate.

When scintigraphy emerged in the 1950s, radiologists were uninterested in the functional imaging technology, which helped to give rise to the medical subspecialty of nuclear medicine. One possible scenario for molecular imaging is the emergence of a new breed of professionals: "molecularists." Such a subspecialty would include some pioneering radiologists, but as in the early days of MRI, it would also involve other scientists, such as biochemists, physicists, immunologists, pharmacologists, and other physicians, most notably oncologists.

The multidisciplinary Society of Molecular Imaging will hold its first major meeting in Boston in August, and it launched a quarterly scholarly journal this month. Its president, Dr. Ralph Weissleder, is a radiologist and director of the Center for Molecular Imaging Research at Massachusetts General Hospital. Weissleder gave community radiologists their first close-up view of molecular imaging in his keynote speech more than a year ago at the 2000 RSNA meeting.

"We are moving very rapidly into the clinical arena," he said. "This technology moves in weeks and months as opposed to the years-and-decades pace we are accustomed to."

The possibility that specialties other than radiology will take control of this technology is heightened by the National Cancer Institute's efforts to incubate early molecular imaging research. An estimated $180 million in NCI grants has been earmarked for research projects through 2005. Some of these grants ultimately will be placed within the new National Institute of Biomedical Imaging and Bioengineering, which could shunt control back into radiology.

Speaking at a refresher course at the RSNA meeting, Dr. William Hendee noted that the NIBIB will eventually sweep up all imaging research sponsored by the NIH, including projects involving molecular imaging. Hendee is a former chair of radiology at the University of Colorado and on the NIBIB committee that is advising the NIH on short-term research strategies for biomedical imaging. Dr. Donna Dean, acting dean of the NIBIB, endorsed the need for advancing the science of molecular imaging.

They are thinking about a number of target areas of research, she noted, including molecular imaging technology, localized or image-guided sensors, and molecular probes.

It is debatable, however, whether the collection of all this research in one agency or within one specialty is a plus for the field of molecular imaging. Radiologists have given this area a lukewarm reception.

Only eight papers were presented at the RSNA meeting on topics involving genes and genetics. Just a single poster was prepared on molecular imaging involving proteomics. Among the most significant was a study done at Johns Hopkins University in which catheter-based vascular gene delivery and distribution were monitored by MRI in an animal model.

The hesitancy may be a practical matter. Unable to keep up with the present rate of growth in imaging procedures, radiologists fear they could be swamped by the early clinical arrival of molecular imaging. Radiologists make up about 3% of all physicians in the U.S., and their ranks are anything but swelling. Procedure volume, however, is growing at a steady clip, 5% to 6% per year.

Radiology's limited capacity may be only a contributing, rather than deciding, factor in the adoption of molecular imaging. Vendors are pushing forward with the technology and the infrastructure for its development. At a press briefing during the RSNA meeting, executives of GE Medical Systems described a major new business platform based on functional imaging, which includes molecular imaging. Dow Wilson, manager of GE's functional imaging group, singled out oncology applications and Alzheimer's disease as the most likely early targets for application of molecular imaging. The company's sales of PET equipment has doubled over the last 12 months, Wilson said, suggesting the depth of interest in procedures that track disease function and not just the anatomical distortion most commonly seen in conventional images.

"This opens up a world of personal and preventive medicine that hasn't previously been available," Wilson said.

Siemens Medical Solutions and Philips Medical Systems also have their sights set on molecular imaging. Dr. David Rollo, the chief medical officer at Philips, called PET "the ultimate" for this new breed of diagnostic medicine. For heart attack patients in whom function of cardiac tissue is in doubt, a contest is being waged between PET, which can image specific molecules that are dying, and MRI, which traditionally uses a washout technique to assess tissue viability.

"If you need to know whether a bypass needs to be done, PET gets you the answer a lot quicker," Rollo said.

Philips and other vendors are working closely with the NIH to organize and finance research with clinical sites, he added. Among research objectives in functional imaging are the development of systems with greater sensitivity to cancer and the fusion of CT and PET for more precise radiation treatment regimens. Siemens scientists believe that because MRI is relatively insensitive to disease detection at the molecular level, technical measures such as higher magnetic field strengths and stronger gradient fields are likely to be employed.

To boost the utility of imaging modalities, some equipment vendors are already working more collaboratively with pharmaceutical companies in developing new breeds of compounds designed to mark the earliest processes of disease. GE has announced agreements with both GlaxoSmithKline and Amersham Health.

Dr. James Thrall, head of radiology at Massachusetts General Hospital, sees threat and opportunity for those in his profession. Radiologists, he said, should be eager to collaborate with corporate partners in advancing molecular imaging under the control of radiology.

"We need to mobilize in this field like we did 20 years ago in MRI," Thrall said. "If we don't, we'll lose it (molecular imaging), to our great detriment."