Scientists from the U.S. Department of Energy's (DoE) Brookhaven National Laboratory, Stony Brook University in New York, and collaborators have demonstrated the efficacy of a "wearable," portable PET scanner they've developed for rats. The device could give neuroscientists a new tool for simultaneously studying brain function and behavior in fully awake, moving animals.
"PET is a powerful tool for studying the molecular processes that occur in the brain," said Paul Vaska, PhD, head of PET physics at Brookhaven with a joint appointment at Stony Brook, who led the development of the portable scanner together with Brookhaven colleagues.
Studying animals with PET has required general anesthesia or other methods to immobilize the animals, according to the researchers. "Immobilization and anesthesia make it impossible to simultaneously study neurochemistry and the animals' behavior - the actions resulting from what goes on in the brain," said Charles Schlyer, PhD, a laboratory chemist at Brookhaven. "Our approach was to eliminate the need for restraint by developing a PET scanner that would move with the animal, thus opening up the possibility of directly correlating the imaging data with behavioral data acquired at the same time."
After several years of development, the scientists have arrived at a design for a miniature, portable, donut-shaped PET scanner that can be "worn" like a collar on a rat's head for simultaneous studies of brain function and behavior. Weighing only 250 grams, the researchers said that the device, called Rat Conscious Animal PET (RatCAP), is counterbalanced by a system of springs and motion stabilizers to allow the animal significant freedom of movement. They reported that measurements of the rats' stress hormones indicated only moderate and temporary increases.
To validate the use of the RatCAP for simultaneous studies of brain function and behavior, the scientists conducted tests with 11C-raclopride, a PET radiotracer, which incorporates a radioactive, positron-emitting isotope of the element carbon. When the positrons interact with electrons in ordinary matter, they immediately annihilate one another, emitting back-to-back gamma rays. Detectors in the circular PET scanner pick up the signals from these back-to-back gamma rays to identify the location and concentration of the tracer in the body.
The researchers describe the tool and validation studies in the April issue of Nature Methods.