Anne M. Landau, April 2016
PET is a tool for in vivo imaging and can be performed in a longitudinal manner where the same subjects can be scanned at various points in time. This facilitates investigation of disease mechanisms and therapeutic approaches over time.
Autoradiography, on the other hand, can be used to visualise and quantify in vitro densities of specific target proteins without competition from endogenous ligands. Autoradiography is performed only at one time-point since it requires postmortem tissue processing. However, it has the advantage of avoiding confounding effects of tracer metabolism, blood flow, passage through the blood brain barrier and plasma protein binding which can complicate PET measurements. Parameters such as binding potential and dissociation constant can be quantified using autoradiography, which can be useful in the characterization of new potential PET ligands.
A wide range of radioligands of specific targets is available for autoradiography. We routinely use [3H], [125I], [11C] and [18F] radioligands in rodent, pig and human brain and peripheral organ fresh frozen tissue sections to quantify receptor and transporter binding and protein aggregation in different disease states. In rodent studies, experiments can also be performed ex vivo, after injection of a radiolabelled tracer into the animal, followed by brain or tissue removal and processing. Studies are currently performed using a BAS-5000 image reader with a resolution of 50 mm and Fujifilm imaging plates. In the near future, it is our intention to replace this system with a new beta imager as a safer, faster and more cost-efficient alternative.