Lecture 15: Nuclear Medicine Flashcards
Define structural imaging
Taking measurements of the internal structure of the body (e.g. x-ray CT).
Define functional imaging
Taking measurements of organ function, describing what organs do.
Describe the basic method of functional imaging in nuclear medicine
1) Inject a patient with a radioisotope (a gamma or beta emitter).
2) Determine the time course of its distribution through the body.
3) Radioisotopes are incorporated into biologically important molecules e.g. glucose.
4) Measure rates of uptake by, and elimination from organs.
What is a radioisotope?
A nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy and making it unstable.
Define activity
The number of disintegrations per second of a radioactive material, measured in Becquerels (Bq).
What is the equation for activity?
A = activity
N = number of decays
t = time
λ = decay constant
Define physical half-life
The time at which half the parent nuclei have decayed, denoted by the following symbol:
What are the equations for physical half-life?
N = number of nuclei
t = time
λ = decay constant
τ = half life
Define biological half-life
The time taken for half of a foreign substance to be eliminated from a biological system. This occurs because foreign substances are eliminated in an (approximately) exponential manner.
What is the equation for effective half-life?
What is the most common radioisotope in nuclear medicine?
Metastable Technetium: Tc-99m
What is Tc-99m used to treat?
- Heart disease
- Brain disorders
- Cancer
How is Tc-99m produced?
It is produced from the radioactive decay of Mo-99 (Molybdenum).
What is the half-life of molybdenum?
67 hours
How is Mo-99 generated?
It is generated from neutron bombardment of U-235, which undergoes fission.
