Re: What is phosphoimaging, I know it is similar to autoradiography.

Basically, phosphoimaging is autoradiography but instead of using X-ray 
film and developing an image photographically, the radioactive pattern is 
transfered to a phosphoimaging plate which is read by scanning with a 
laser.
When the radioactive membrane is exposed to the phosphoimaging plate, 
(which contains fine crystals of BaFBr:Eu(2+)), the ionising radiation 
excites an electron of Eu(2+) into the conduction band, which results in 
the oxidation of Eu(2+) to Eu(3+) and the reduction of BaFBr to BaFBr-

BaFBr:Eu(2+) --> BaFBr-:Eu(3+) 

The BaFBr- complex has an absorbtion around 600 nm. Exposing the excited 
complex to a helium-neon laser, red light (633 nm), results in the 
release of an electron, reducing Eu(3+) to Eu(2+*). The Eu(2+*) (excited 
state) then releases a photon at 390 nm (blue light) as it returns to its 
ground state.

Phosphoimaging plates can be reused after a 10-minute exposure to visible 
light i.e. the stored radioactive image is scrubbed by exposure to 
visible light.
 http://www5.amershambiosciences.com/aptrix/upp01077.nsf/Content/gel_blot_s
torm_storage_phosphor http://analytical.chem.wisc.edu/524class/Folders/Bailey/524topic.html