Ask the individuals who perform molecular imaging for a definition, and no two will be alike. For this reason, the Society of Nuclear Medicine has developed a broad definition for molecular imaging, often called the next frontier in diagnostic imaging. Type the phrase molecular imaging into Google, and you’ll get 18.8 million results. Ask the individuals who perform molecular imaging for a definition, and no two will be alike. For this reason, SNM – the world’s largest society for molecular imaging and nuclear medicine professionals – has developed a broad definition for molecular imaging, often called the next frontier in diagnostic imaging. The society debuted its definition during its 54th Annual Meeting in Washington, D.C.

“We are on the brink of a revolutionary change in medicine. The catalyst for this change is molecular imaging, which provides a way to see, define and track how molecules in the body function and change – particularly in relation to disease – and use that information to improve patient care,” said SNM 2006-07 President Martin P. Sandler. “Molecular imaging provides the key to the future of personalized medicine, which involves diagnosing, treating and monitoring patients based on their individual makeup,” added the associate vice chancellor for hospital affairs for Vanderbilt University Medical Center in Nashville, Tenn.

“SNM’s definition is intended to capture and explain the essence of an evolving and multidisciplinary field, and it’s quite an achievement to reach a consensus,” said Sandler, indicating that the field relies on the complementary skills of scientists and professionals, including nuclear medicine physicians, radiologists, biologists, chemists, technologists, engineers and physicists. It is this interrelationship that allows for the continuation of rapid advances and integration across medical specialties, he noted. “Our members – representing many areas such as molecular and functional imaging, nuclear medicine, radiology and engineering – spent months developing this definition,” he added.

“The Webster dictionary says that a definition is a concise explanation of the meaning of a word or phrase – a statement expressing the essential nature of something,” said Martin Pomper, president of the society’s Molecular Imaging Center of Excellence. “Members of MICOE’s Definitions Task Force attempted to provide just that – an explanation of the essential nature of a complex term – for this evolving field. They developed standard definitions and terms that will serve as a framework for all the society’s molecular imaging activities,” noted the associate professor of radiology at Johns Hopkins Medical Institutions in Baltimore, Md.

SNM’s definition – approved by board members from both SNM and MICOE – states: “Molecular imaging is the visualization, characterization and measurement of biological processes at the molecular and cellular levels in humans and other living systems.” The definition further elaborates: “Molecular Imaging typically includes two- or three-dimensional imaging as well as quantification over time. The techniques used include radiotracer imaging/nuclear medicine, MRI, MRS, optical imaging, ultrasound and others.” Other definitions developed include the following.

• Molecular imaging agents are “probes used to visualize, characterize and measure biological processes in living systems. Both endogenous molecules and exogenous probes can be molecular imaging agents.”
  
  
• Molecular imaging instrumentation “comprises tools that enable visualization and quantification in space and over time of signals from molecular imaging agents.”
  
  
• Molecular imaging quantification “is the determination of regional concentrations of molecular imaging agents and biological parameters. Further, molecular imaging quantification provides measurements of processes at molecular and cellular levels. This quantification is a key element of molecular imaging data and image analysis, especially for inter- and intra-subject comparisons.”

“Our challenge was to take a broad perspective on molecular imaging while providing concrete information on an emerging scientific and clinical specialty,” said David A. Mankoff, chair of SNM’s MICOE Standard Definitions Task Force. “Input from task force members – with a broad range of backgrounds and expertise, including individuals outside of nuclear medicine – was key in generating the molecular imaging definitions,” he added.