SAIP - POSITRON EMISSION TOMOGRAPHY IMAGING

Positron emission tomography (PET) utilizes a pharmaceutical tagged with a positron emitting nuclide for imaging physiological processes.  The positron emitted by the nucleus travels a few millimeters where it interacts with an electron, called mutual annihilation.  When the positron undergoes mutual annihilation with the electron, their rest masses are converted into a pair of annihilation photons; both photons have 511 keV and are emitted in nearly 180-degree opposing directions.  Detection of the annihilation photons allows the PET scanner to localize the annihilation origin along a line between the two detectors.  Due to the non-colinearity of the annihilation photons and photon scatter, the spatial image resolution is inferior to MRI and CT, while the sensitivity (ability to image very low probe/contrast concentrations in the picomole range) is the highest of most imaging modalities.

The initial radiopharmaceuticals that will be available from IBA Molecular, North America (Sterling, VA) for PET imaging are:
- [18F]Fluoro-2-deoxy-2-D-glucose ([18F]FDG); (metabolism)
- [18F] 3’-Deoxy-3’-[18F]flrorothymidine ([18F]FLT); (cell proliferation)
- Na-[18F]; (Bone imaging agent).

The Siemens Inveon MicroPET scanner (Siemens Medical System, Knoxville, TN); pictured below, will be docked to a microCT (installation scheduled for fall’07) to provide anatomical and photon attenuation for improved image quantitation.  Presently, two 57Co point sources will measure photon attenuation which is used to quantify the radiopharmaceutical concentration within the sites of interest.

 
Siemens Inveon PET scanner