Nuclear Medicine Flashcards
What are patients injected with when performing nuclear imaging scans?
Radioactive isotopes
What is the difference between X-ray/CT/MRI with a contrast agent and nuclear medicine?
Contrast dye binds to certain structures and increases the attenuation of that structure. However, nuclear medicine releases certain types of radiation when it binds to molecules and these are detected on a scan
Which sort of radiation do radio-isotope dyes emit?
Gamma rays and positrons
What is the key difference between what nuclear medicine scans and other modalities can detect?
Nuclear medicine is a molecular imaging technique, whereas others are structural imaging technique
What are Poisson distribution statistics?
Nuclear events always occur with a degree of randomness and Poisson distribution statistics show the probability of certain events occurring
What is the practical purpose of Poisson Statistics?
It helps to ‘cancel out’ the noise from random nuclear events and isolate the events which are from the desired radio-isotopes
In a gamma camera, what is a collimator?
A simple component which ensure only radiation from a specific direction hits the detector.
What are some characteristics of an image using collimators?
Collimators with long and narrow holes increase the resolution but decrease the sensitivity. The inverse is true for short and wide holes.
How does a collimator decrease sensitivity?
It blocks >99% of radiation and therefore decreases sensitivity
What sort of collimation does PET use?
Electonic collimation; leads to higher signal to noise ratio
How does electronic collimation work?
A positron, like those in the radioisotope, release two gamm rays in opposite directions. The detector will ‘ignore’ gamma rays when there are not two rays detected coming from opposite directions
Which radioisotope is used to study glucose metabolism?
18 F-FDG
What is an example of a pure gamma-emitting radioisotope?
99m Tc
What can glucose metabolism PET differentiate between and how does it do this?
Glucose uptake is very high in tumours but very low in scar tissues
What are 3 drawbacks of using PET?
1) Very expensive
2) Isotopes have a short half-life (minutes)
3) An onsite chemistry lab must produce the isotopes
