AbstractID: 8465 Title: PET Imaging Physics and Instrumentation
Positron emission tomography (PET) images represent the distribution of a tracer which is
labelled with a positron emitting isotope. Since many biologically active chemicals can be labelled
with short lived isotopes like 11-C, 18-F and 15-O, PET is considered an $functional# imaging
technique, rather than an $anatomical# imaging technique (like X-Ray computed Tomography).
PET scanners detect, in coincidence, the two gamma rays which are formed when a positron
annihilates with an electron very close to the point where the radioactive atom decayed. Most
modern PET scanners have a large number, (<5000) of detecting crystals which are grouped into
individual blocks of 16-64 crystals each. The number of counts recorded on all possible lines
passing through the patient joining any two crystals is recorded for times ranging from a few
seconds to a few minutes. The counts recorded on all of the millions of lines of response, are then
reconstructed into a series of parallel slices. The reconstruction must compensate for the
attenuation and scatter of gamma rays, the effects of detector dead time, and of random
coincidences (when two gamma rays from independent annihilations are detected simultaneously)
This talk will discuss the various tradeoffs in detector design and data processing
configurations which make PET scanners suitable for human $whole body# scanning, or for
specific organ imaging (eg. brain or breast), or small animal imaging. These tradeoffs are based
on spatial resolution, count-rate capabilities, quantitative accuracy, and of course COST!