BBI Contributing Writer

TORONTO – The 52nd annual meeting of the Society of Nuclear Medicine (SNM; Reston, Virginia) at the Metro Toronto Convention Center in mid-June reinforced the clinical relevance and global economic vitality of nuclear medicine generally and molecular imaging in particular. SNM is the largest scientific organization dedicated to molecular imaging/nuclear medicine, with more than 16,000 members who are physicians, technologists, physicists, chemists and radiopharmacists. This year’s meeting featured more than 1,600 scientific papers and posters and more than 170 exhibiting manufacturers of molecular/nuclear imaging equipment and consumables.

Regional nuclear medicine societies were represented – including those from Korea, India, Australia, New Zealand and Europe – as well as a number of imaging-related scientific societies based in the U.S.

When SNM was formed in 1954, nuclear medicine was all about the introduction of radionuclides (gamma-emitting substances) into the body for therapeutic and diagnostic purposes. Today the society enjoys a far greater scope of interests, most notably including activities only recently described as molecular imaging – that is, the imaging of metabolic, or functional, processes in vivo. There are at least five other professional societies covering the molecular imaging territory, but SNM probably has the greatest reach and influence on the involved communities. Extending that reach has expected clinical, research and political dimensions; one can imagine some consolidations being considered, and at least one such combination is rumored.

The scientific program of this year’s gathering consisted of several tracks, including cardiovascular, brain imaging, pediatrics, PET/CT, general nuclear medicine, thyroid, and oncology and therapy.

Without question, the most important clinical and commercial dynamic in the field of nuclear medicine – perhaps in all of medical imaging – is the fusion or hybridization of imaging modalities to visually blend metabolic and anatomical information. The baseline tomographic anatomical imaging modalities are computed tomography (CT) and magnetic resonance (MR). The principal metabolic modalities today are positron emission tomography (PET) and single-photon emission computed tomography (SPECT). Both these modalities produce 3-D computer-reconstructed images of an organ, tumor or other metabolically active site within the body, but those images lack precise anatomical dimensional definition. By fusing images or combining scans via PET/CT or SPECT/CT, exquisite 3-D images yielding both metabolic and anatomical indicators can result.

Several imaging equipment suppliers offer these hybrid scanners, and most PET scanners sold today are in fact PET/CT imagers. Interestingly, the first imaging system offering researchers PET, SPECT and CT modalities in a single instrument designed to image small animals was introduced at the SNM meeting by Gamma Medica (Northridge, California). With this new instrument, researchers and drug developers can choose to employ any one, any two or all three imaging modalities for a given study.

Next steps in molecular imaging

The society’s Henry Wagner Lectureship was delivered to a packed house by Sanjiv (Sam) Gambhir, MD, PhD, who directs the Molecular Imaging Program, comprising a staff of 90, at Stanford University (Palo Alto, California). He laid out a road map for the extension of classical nuclear medicine to embrace non-isotopic tags, thereby unofficially redefining nuclear medicine as the more general molecular imaging. Politics aside, these two fields are essentially redefining themselves as imaging targets, imaging tags and imaging technologies move forward to expand imaging applications in medicine.

While reminding the audience that isotopic methods remain important, especially for intracellular imaging, Gambhir highlighted the growing applicability of MR, optical methods and ultrasound – the latter via gas-filled bubbles – in the molecular imaging armamentarium. He also opined that multimodality imaging is a discipline of extraordinary promise. Newer methods in MR, optics and ultrasound are being explored first in preclinical (small animal) imaging for research and drug development, but he said he expects them all to find eventual applications in the clinic within about three years. Gambhir seemed most enamored of optical methods, corresponding to an expanding program dealing with those methods at Stanford.

He also noted the potential clinical relevance of molecular imaging to monitor the progress of emerging stem cell therapies. This can work by attaching reporter genes to biological targets, genes which then express proteins that can be imaged, most readily by red/infrared optical methods and perhaps by other modalities as well. This imaging application has been stimulated by California’s recent stem cell funding initiative. Nevertheless, progress in this arena is likely to be paced not by politics or the availability of molecular imaging tags but by the availability of biochemically defined targets.

Neurological applications

Perhaps the most exciting progress exhibited by molecular imaging recently has been evidenced in brain imaging to detect, diagnose and monitor emerging therapies for dementias and neurodegenerative disorders such as Alzheimer’s (AD) and Parkinson’s diseases. These medical conditions are of great importance. About 24% of the U.S. population of age 80 and above exhibit symptoms of dementia; about 65% of dementias are caused by AD, which is the third-most-expensive disease in the U.S., costing about $100 billion per annum. Conventionally, the confirmation of AD is a long process of elimination that averages between two and three years of diagnostic and cognitive testing.

Michael Devous, PhD, of the University of Texas Southwestern Medical Center (Dallas), delivered a special plenary lecture on the topic. He noted that the diagnosis of dementias and AD is inadequate and too late in disease progression today, and disease incidence is thought to be growing rapidly. There is a compelling need to detect disease earlier (pre-symptomatically) and more accurately, since emerging therapies might ultimately delay symptom onset by five to 10 years, which would be tantamount to a cure for many.

PET and SPECT brain imaging are becoming reasonably effective in diagnosis, with PET exhibiting somewhat better performance. Researchers at the University of Pittsburgh have recently demonstrated the ability to reliably image amyloid plaques in the brain, key indicators of AD. Quantification has become important in risk assessment and therapeutic monitoring. And the Center for Medicare & Medicaid Services (CMS; Baltimore) earlier in 2005 authorized reimbursement of PET procedures using the radionuclide/glucose tag FDG (fluorodeoxyglucose) for the diagnosis of AD, a recognition of the test’s effectiveness and a driver of much greater clinical use.

A consortium of researchers from University Mainz (Mainz, Germany) and other German institutions reported remarkable findings of their work on an expert system to enhance the diagnostic accuracy of AD using FDG-PET scans. “The knowledge of several experts in the field was utilized in the development of a computer program by defining several rules used by these experts for diagnosing and excluding AD,” according to one of the authors, Peter Bartenstein. The software system was then tested in 150 cases. The system performed as well as experts in identifying AD patients, even in the very early stages. The system is also able to identify other dementia disorders, such as frontal lobe dementia or Lewy body disease, that show different abnormalities in the image. Once commercialized, this prototype system could serve as an aid to experienced clinicians and a training tool for inexperienced ones.

Imaging applied to movement disorders, including especially Parkinson’s disease (PD), was addressed by David Brooks, MD, of Imperial College School of Medicine (Hammersmith, UK). He reviewed the state of the art, which is inadequate for definitive PD diagnosis but improving. MR can distinguish PD from atypical PD but is not sufficiently sensitive for definitive diagnosis. Work at the frontier is focused on dopamine imaging in the brain via SPECT and PET, the ultimate goal being to diagnose early and administer as yet undiscovered neuro-protective agents. The cause of PD remains unknown, and there is much remaining work to do.

Cancer prognosis

A team of researchers working at the Technische Universitaet Muenchen (Munich, Germany) reported on the successful use of sequential FDG-PET studies in predicting survival of ovarian cancer following chemotherapy. CT and MR typically are used to evaluate response to chemotherapy, with the decrease in tumor size being the most important criterion for success. But both modalities suffer from limitations when applied to tumor sites in the abdomen and pelvis. Early identification of response to therapy is important so that ineffective therapies can be discontinued and potential alternative therapies attempted.

FDG-PET has gained increasing acceptance for staging various cancers over the last decade, and the Munich workers found the method to be prognostic in ovarian cancer. They studied 33 patients with advanced ovarian cancer, administering quantitative FDG-PET scans prior to treatment and following the first and third rounds of chemotherapy and found that the imaging procedure predicted response to chemotherapy after its first round. This performance is significantly better than CT or MR in ovarian cancer prognosis, demonstrating that PET imaging can be used not only for diagnosis and staging of certain cancers but for prognosis as well.

Commercial highlights

The SNM exhibit hall was well attended at each of our visits. We noted an emphasis on scanners (especially hybrids), imaging agents of various kinds, and image presentation and management systems. We were struck by the apparent absence of optical scanner suppliers, presumably because this is a “nuclear” meeting. As one might expect, the leading nuclear medicine scanner suppliers had the highest-profile presence and the greatest attendee interest overall.

Philips Medical Systems (Andover, Massachusetts) exhibited in a trailer the claimed “world’s first open PET/CT,” an open-configuration scanner. The company also announced 2006 availability of 64-slice CT capability to its PET/CT and SPECT/CT scanners.

Siemens Medical Solutions (Malvern, Pennsylvania) had the most elaborate multi-booth presentation, with many products on the floor, simultaneous video viewing stations and apparently the greatest attendee interest level as measured by its booth traffic. This meeting was an opportunity for Siemens to exhibit the combined product families of Siemens Nuclear Medicine and CTI Molecular Imaging (Knoxville, Tennessee), its recent acquisition. The combined firm is to be known as Siemens Medical Solutions Molecular Imaging.

GE Healthcare (Waukesha, Wisconsin) provided a typically professional presentation and enjoyed substantial interest among attendees. The company launched a new 8/16-slice PET/CT scanner, Discovery STE, along with a new cyclotron, radiotracer lab and bone reconstruction software.

Other highlights from the SNM exhibit floor:

• Thinking Systems (St. Petersburg, Florida) highlighted its PACS solutions and workstations supporting nuclear medicine and PET, among many other modalities. The company distributes its products through GE Walker (Tampa, Florida).

• PMOD Technologies (Adliswil, Switzerland) exhibited its software tools for platform-independent quantitative processing of biomedical image data, including tools for image fusion, 3-D rendering, and discrimination of Alzheimer’s dementia.

• SA Instruments (Stony Brook, New York) featured its physiological monitoring and gating systems for research applications, i.e., small-animal imaging. Its monitoring systems are compatible with MR, CT, PET and SPECT modalities.

• SynterMed (Atlanta) exhibited its suite of nuclear cardiology software tools, including the latest release of its Emory Cardiac Toolbox. A version of that product for quantitative PET evaluation of cardiac perfusion is now being distributed by Hitachi Medical Systems America (Twinsburg, Ohio) for use with its PET/CT imaging system.

• MDS Nordion (Ottawa, Ontario), a supplier of reactor and cyclotron radioisotopes for nuclear medicine, disclosed the availability of copper-64 (Cu-64), a new long-lived PET imaging agent with apparent applications in drug development and therapies.

• Mallinckrodt (Saint Louis) highlighted its NeutroSpec scintigraphic imaging agent for definitive diagnosis of appendicitis, a frequently misdiagnosed condition resulting in high, unjustified healthcare expenditures.

• Shared PET Imaging (Canton, Ohio), a PET imaging services provider, announced the availability of its ClarityFusion fused hybrid imaging software as a product to healthcare providers.

• Eastern Isotopes/IBA (Sterling, Virginia) reported the completion of tests for a new, modular automatic synthesizer for the preparation of PET biomarkers, including FDG. The company said it intends to introduce its new synthesizer to the market in 2006.

• Codonics (Middleburg Heights, Ohio) highlighted its Horizon multimedia dry imager which, according to the company, can be used in lieu of three existing printers to record on film, on paper, and in color. The Horizon imager provides multi-format, multi-size and multi-media output.