|
This essay examines Positron Emission Tomography (PET), an imaging modality that is able to provide information regarding biochemical and physiological function, rather than simply anatomical structure. PET is also relatively unique in that, unlike other major imaging modalities, it relies on a radiation source internal to the patient (rather than an external source as used in x-rays and CT scans) to produce an image. The physics of PET will be examined, in addition to the processes of PET scanning and image development. Finally, the advantages of PET as well as its limitations will be considered. ...
PHYSICAL PRINCIPLES
PET scanning relies on the instability of radioisotopes with too few neutrons (too many protons) When these neutron-poor (proton-rich) radioisotopes decay they convert a proton to a neutron, emitting a b+ particle (as well as energy and a neutrino), which is known as a positron (Saha, 1993). ... Therefore, when a positron collides with an electron they are both annihilated. ... When a positron-emitting radioisotope is administered to a patient the point of annihilation occurs very close to the point of positron emission due to the high density of matter. It is these g-rays, not the positrons themselves, that are detected in PET.
The radioisotopes used in PET are produced in a cyclotron or linear accelerator (Victor & Ropper, 2001). ...
THE SCANNING PROCESS & IMAGE DEVELOPMENT
In PET, a solution containing a radioisotope-labelled molecule is injected into circulation (Squire, Bloom, McConnell, Roberts, Spitzer Zigmond, 2003). The concentration and distribution of this tracer is then able to be determined non-invasively by placing the patient in a PET system which contains a rotating ring of detectors. As previously described, when a positron collides with an electron they are both annihilated, emitting two g-rays which travel from the point of collision in nearly opposite directions.
Approximate Word count = 1434
Approximate Pages = 5.7
(250 words per page double spaced)
|
|
