Technology - Positron Emission Tomography (PET) Imaging
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Molecules accumulating at a specific target site may be labeled with a positron emitting radionuclide. The emitted positron traverses a short distance until it collides with an electron, annihilating into two gamma rays of 511 KeV. The coincident detection of the two gamma rays that are emitted ˜180 degrees apart from each other can be recorded and used to reconstruct an image showing the location and amount of positron radionuclides in the body of a living subject. PET imaging relies upon clearance of PET probe from non-target site and accumulation of probe at target sites over time.
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PET reporter genes and PET reporter probes enable imaging non-invasively all living mammals regardless of size
- Transgene expression (Gene therapy monitoring)
- Endogenous gene expression
- Cell kinetics (Cell therapy, regenerative medicine and cancer therapy)
- Protein-protein interactions
- Signal transduction
- Pharmacodynamics, or molecular effects of external factors such as administered therapeutic agents
PET Reporter Genes & PET Reporter Probes
- Enzyme based: PET reporter probe accumulates in cells expressing its PET reporter gene due to entrapment caused by enzyme encoded by PET reporter gene
- Receptor based: PET reporter probe accumulates on the membrane or inside cells by binding to a protein receptor encoded by the PET reporter gene
- Transporter based: PET reporter probe accumulates in cells through a transporter protein encoded by the PET reporter gene
Advantages of PET
- Relatively high sensitivity (highest sensitivity for imaging large animals and humans)
- Trace dose of imaging probe, unlikely to have pharmacological or toxic effects
- Quantitative molecular imaging modality makes it suitable for kinetic modeling applications and tracking pharmacokinetics of therapeutic agents
- PET/CT allows accurate determination of anatomical location of probe activity
- Very low tissue attenuation (which can be corrected) hence no depth limitation
- Higher spatial resolution than optical imaging
- Ability to image metabolism, apoptosis, proliferation, cellular transporters, cell receptors, oxygen availability, gene expression and cell kinetics, non-invasively in living subjects at multiple time points