Instrumentation to improve the spatial resolution and sensitivity in small animal PET
Dr. Sara St. James
Harvard Medical Physics Residency Program
Harvard Medical School
Tuesday, January 17, 2012
HP 4351


The motivation for using positron emission tomography (PET) is twofold.  PET is a very sensitive imaging technique with reported sensitivity of 10-11 - 10-12 moles/liter.  Positron emitting radionuclides are atoms that may be attached to biologically relevant molecules, making the chemistry of PET flexible.  For clinical and pre-clinical molecular imaging, PET is capable of imaging the underlying biological processes.

There remain several challenges specific to small animal PET that need to be addressed. The spatial resolution in commercial small animal PET scanners is ~ 1 mm, leading to partial volume effects and problems in quantification for structures smaller than 2 mm. In addition, the duration of an imaging study using a small animal PET scanner is on the order of 10-30 minutes. This duration is, in part, due to the sensitivity of the scanner. With an increase in sensitivity, the duration of the scan may be reduced without sacrificing image quality. Additional benefits to increasing the sensitivity of the scanner include the improvement of dynamic studies of the tracer distribution in the subject and the potential to reduce the injected amount of radionuclide (decreasing the radiation dose to the subject).

Detector design to improve the spatial resolution and sensitivity of small animal PET is explored in this talk. To improve the spatial resolution, detectors with smaller elements were developed, progressing from detectors with individual crystal sizes of 0.7 mm X 0.7 mm X 20 mm to detectors with individual crystal sizes of 0.22 mm X 0.22 mm X 20 mm. These detector designs are complemented by Monte Carlo simulations that explore the sensitivity and spatial resolution achieved with such detectors. Novel tapered detector designs are explored as is a single-detector insert to locally improve the spatial resolution and sensitivity of an existing small animal PET scanner.