Topic 9: Radionuclide production Flashcards
Specific activity
Ratio of radionuclide activity to the total mass of the element present (MBq/g)| (Non-radioactive element is known as the ‘carrier’ – High specific activity is sometimes called ‘carrier-free’ or ‘without carrier’)
Nuclear medicine requires a (low/high) specific activity?
high
Label the parts
Top: Control rods
Outer: concrete shield
Nuclear Fuel
Graphite core
Reactor vessel
What does the graphite core do in the nuclear reactor
Graphite core (moderator) slows down fission neutrons because slower neutrons are more efficient at creating further fission events
What do the control rods do?
Create a controlled chain reaction: controlling the fission rate. They absorb many neutrons withouth themselves fissioning.
- ideally each fission event creates one further event
- not enough creates a runaway reaction / meltdown
- more rods would slow down or shut off the reactor.
What does the coolant do in the nuclear reactor?
Regulates the vast thermal energy that is emitted as a by product of the fission reactions.
Nuclear Fission?
A nucleus of an atom splits into smaller, lighter nuclei producing free neutrons and gamma photons and a large amount of energy.
How do you produce radionuclides using bombardment
Nuclear bombardment reactions are nuclear reaction in which a nucleus is bombarded or struck by another nucleus or nuclear particle. Here fission or fusion may occur.
What are two common modes of radionuclide product by bombardment
?
if we want the same element - Electron capture - neutron with a gamma ray coming out
Different element we can bombard with neutrons and protons coming
What are the produced radionuclides from bombardment like?
low specific activity because mixture of radioactive and stable material
Neutron rich
Often decay by beta
Generally have long half-lives
Cyclotron?
proton attracted by the dees which flip polarity constantly, gaining energy and making a circular direction of travel, and it will get a larger and larger radius, and you will use an extraction foil and fire it at a target.
two types of cyclotrons
positive ion
Inefficient
upto 30% of beam lost
Negative ion.
foil strips of electrons creating positive ion
magnetic beam on +ve ion directs beam to target
almost 100% efficient. non-activating (cold)
Cyclotron production evaluation?
produces neutron deficient isotropes
- decay by beta+ or e.c
most have different z number.
high specific activity
produces biologically important isotopes such as c-11, n-13, o-15.
Describe the process of the Mo99/Tc99m generator
We like technetium why?
Because it emits gamma rays only because it is at this metastable state after previous beta or alpha emission.
Mo99 -> Tc99m - > Tc99
Tc-99m gives two energy gamma photons?
140.5 keV (98.6%)
and 142.5 kev
5 types of producing radionuclides?
- Naturally occuring
- Fission
- Neutron bombardment
- Cyclotron
- Generator
Explain the emissions of all these types of producing methods of radionuclides
1) Naturally occuring
2) Fission
3) Neutron bombardment
4) Cyclotron
5) Generator
1) Naturally occuring
2) Fission
3) Neutron bombardment
4) Cyclotron
5) Generator
Explain the nuclear properties, specific activity, decay and emission of Fission?
Neutron rich,
very high activity,
beta decay
emits betas, high energy gamma
Mo 99 is the parent.. what is the daughter decay and granddaughter decay?
Te - 99m
and
Te 99
How much is the decay of the daughter? and what are the assumptions?
the daughter has a much shorter half life
all daughter and no parent is eluted from the generator
describe the graph
the amount of technetium is eluted and builds up again but you cant have more activity of the daughter than the parents
if we elute too early we will not recover the full activity available to us
answer the question
answer the question
What is the tracer principle?
Radioactive compounds participate in physiological processes the same as non-radioactive compounds
modern scanners allow:
we can measure molecular concentrations to be measured with tremendous sensitivity
Decay scheme for Iodine-123
produced in a cyclotron by proton irradiation of enriched Xenon
- several decay processes to get to I-123
- Decays by electron capture
- Predominant radiation 159 keV gamma photon
Iodine-131 ?
comes from a reactor
used for therapy but can image with it
used for imaging thyroid cancer because it tends to build up in the thyroid and it can also be used to treat the cancers.
Most used radionuclide for PET?
Fl-18
