RatCAP (Rat Conscious Animal PET)
A team of scientists is developing mobile imaging technology to view animal brain function without the use of anesthesia. When developed and refined for humans, such techniques may allow the subject to move during a PET or MRI scan. These advances are expected to have a major impact on neuroscience and medicine.
Project
- Title: Imaging the Awake Animal
- Principal Investigator: David Schlyer, Brookhaven National Laboratory
- Collaborators: Ronald Huesman, Lawrence Berkeley National Laboratory, and Ira Rampil, State University of New York, Stony Brook
- Project Term: October 1, 2004–September 30, 2007
MRI of Moving Objects
Imaging data from PET and MRI scans increasingly are being used to study the biology of normal and bioengineered animals; evaluate abnormalities in animal models of human disease; and evaluate efficacy and toxicity of experimental drugs and the effect of illicit drugs. PET and MRI play an important role in understanding the functions of proteins encoded in genes.
This team is developing MRI and PET techniques that will help explain the brain changes that result in the behavior of awake bioengineered mice and rats under natural physiological conditions. Achieving this goal will involve developing a miniature mobile PET camera to be worn by an active animal, appropriate motion-tracking methods, restraint devices that cause minimal stress, and post-processing computer algorithms. Tools also are being developed to determine the animal’s head position and to correct the imaging data for motion.
MRI of moving objects, such as awake animals, is a formidable challenge. The magnets used for MRI, as well as the time-varying magnetic-field gradients used for spatial encoding, define three principal axes that are usually static. Translations and special rotations with respect to this static reference frame affect image quality. To resolve this problem, the team will track head motion in real time and then dynamically adjust the principal gradient axes so they remain fixed with the target-organ frame of reference.
A similar approach will be used to dynamically adjust the main MRI magnetic field orientation. Superconducting magnetic technology developed at BNL’s Relativistic Heavy Ion Collider facility will be used to create dipole magnets with the same cylindrical shape as MRI magnets. A potential design includes two of these dipole magnets with perpendicular field axes to generate fields that can effectively rotate the main field by up to 5 or 10°.
Motion tracking is another problem faced by the research team. One solution being considered is to apply algorithms for motion tracking with images captured by high-resolution digital cameras using multiple reference marks (fiducials).
In addition, researchers will determine which restraining techniques, such as slings or confinement in a tube, are best suited to minimize animal stress and the effects of these restraining techniques on brain metabolism. Eventually, the new MRI and PET technologies will be used to evaluate the differences in physiological and biochemical brain functions between awake and anesthetized animals.
Potential Impact
Since current imaging studies are performed almost exclusively in anesthetized animals, the new technologies will have a major impact on neuroscience and, eventually, on medicine. These developments will allow more detailed studies of gene function to construct animal models of human diseases and explore drug effects and behavior.
Most of the new techniques also can be extended to reduce the effects of motion for human studies, for example, to perform advanced imaging studies in patients or children who have difficulty keeping still.
Related Website
Awake Animal Imaging at Brookhaven National Laboratory
