Molecular imaging meeting spotlights opportunities in basic and clinical research

Molecular imaging is gaining ground. The fourth annual Society for Molecular Imaging (SMI) meeting held Sept. 7 to 10 in Cologne, Germany, drew nearly 1100 attendees, up from about 800 at last year's meeting in St. Louis. About 60% of attendees were from the U.S. The rest were from Europe and Asia, primarily Japan and South Korea.

The program was rich in new scientific discoveries from the imaging of genomic processes to new imaging instruments. Several reports cited future opportunities for applications development.

One of the first human studies of technetium-labeled Annexin 5A was reported by Dr. Leonard Hofstra, an associate professor of cardiology, and colleagues at the Maastricht University Hospital in the Netherlands. They studied 16 patients with confirmed severe carotid artery stenosis to determine if the agent's known ability to identify regions of high apoptotic activity could noninvasively identify unstable plaques. Test results indicated that this agent can be used to distinguish between stable and unstable carotid plaques.

Metastatic melanoma cells are enormously resilient, overcoming any single biochemical strategy designed to stop their migration through the body. By directly observing such cells with real-time 3D confocal fluorescent microscopy, Dr. Peter Friedl, a professor of dermatology at the University of Wuestburg in Germany, created a remarkable video demonstrating how evolution has equipped melanoma cells with potent genomic defenses.

Gallium 68 is the lost child of PET, overshadowed if not buried by F-18 FDG. A new generator for Ga-68 production discussed at the SMI meeting may focus more attention on this positron-emitting tracer. The generator can produce tracer inexpensively and efficiently, according to Dr. Frank Roesch of the University of Mainz in Germany. Generators can be based at facilities where the agent is used, as is the case with molybdenum-technetium generators. The 67-minute half-life of gallium compares well with fluorine 18, especially if it can be locally produced. Roesch anticipates that nuclear physicians will initially pair the tracer with octreotide for neuroendocrine cancer imaging. It could also be applied to myocardial perfusion measurement, cerebral applications, kidney function, and pulmonary ventilation.

Carbon 11 PK11195 can image microbial activation to characterize Alzheimer's disease. Microglial cells are activated only in response to neuronal injury and may themselves contribute to the cause of Alzheimer's disease, according to Dr. David J. Brooks of Imperial College, London. C-11 PK11195 PET detects a 1.5- to twofold increase in microglial activation associated with the deposition of amyloid plaques in cortical structures of Alzheimer's patients. It also has implications for the imaging of Parkinson's disease.

Dr. Rudolf Graf of the Max-Planck Institute and University of Cologne neurology department described the use of PET/CT for the diagnosis of malignant stroke, a condition accompanying ischemic stroke that involves inflammation and edema in 15% of cases. This condition usually results in death. Diagnosis with PET/CT leads to surgical resection of ischemic penumbra, potentially increasing the likelihood of survival.

Microcirculatory measurements possible with dynamic contrast-enhanced MRI are the key to reliably predicting therapy responses, according to Dr. Alexander De Vries, an imaging researcher in radiotherapy and radio-oncology at the Medical University of Innsbruck in Austria. De Vries examined the relative diagnostic power of functional MRI apparent diffusion coefficient mapping and perfusion indexing for two groups of patients with grade II rectal cancer. Both groups were prescribed chemoradiation preceding surgical resection. Morphology MRI had shown that the primary tumor had not invaded the perirectal tissue in any of the cases. No evidence of metastatic disease or secondary malignancies was found. Previous therapy had not altered microcirculation associated with the tumors.

Dr. Ralph Weissleder, chair of the Center for Molecular Imaging at Massachusetts General Hospital, is working with Siemens Medical Solutions to develop an Internet portal for molecular imaging research. The Web site will feature a large archive for the storage and display of imaging characteristics of various molecular modalities and disease states.