Question

Which of the following are true with regard to positron emission tomography (PET)? 

a. It detects single gamma rays produced following the collision of a positron with a negative beta particle 

b. The radio nuclides used in PET are normally produced in a cyclotron 

c. It results in lower noise levels than conventional gamma imaging 

d. It provides detailed anatomical information 

e. Scintillation detectors are usually made of NaI

Answer 1

a. False. Following the collision of a positron with an electron, two gamma photons (511 keV) are produced, which travel in opposite directions. The simultaneous detection of these photons along the line of response will lead to the registration of the event. 

b. True. The tracer used most commonly is glucose labelled with Fl-18 (18-FDG), which has a very short half-life. Generators can also be used to produce radio cnuclides, for example the Ge-68/Ga-68 generator.

c. True. 

d. False. PET images provide functional and physiological information and are therefore often fused with computed tomography (CT) or magnetic resonance imaging (MRI) to provide anatomical information. 

e. False. Scintillation detectors are most commonly made up of bismuth germanate or lutetium yttrium ortho silicate (LYSO), which have a high detection efficiency and are able to absorb and convert photons with 511 keV into light.