NM 3 Flashcards
what does an isotopes half life allow us to determine
- how long a sample of a useful isotope will be available
- how long a sample of undesirable/ dangerous isotope must be stored before it decays to low enough radiation level (safe)
what is physical half life
period of time required to reduce radioactivity level of source to exactly half of its original value solely to radioactive decay
what is biological half life
period of time required to reduce amount of a drug in an organ/ body to half of it’s value due to biological elimination
what is effective half life
period of time required to reduce radioactivity level of internal organ due to biological elimination
what is effective half life
period of time required to reduce radioactivity level of internal organ/ whole body to half of its original value due to elimination AND decay
what is the decay law
describes decay of a quantity over time
- exponential
what are radionuclides
radioactive isotopes/ isomers of an element
what are radiopharmaceuticals a combination of
- radioactive molecule that permits external detection
- biological active molecule/ drug that acts as a carrier and determines localisation
nuclear reactors
- where radionuclides are produced
- produced using target materials with neutrons
- ## neutrons cause nuclear reactions in target material
what is the proces by which nuclides are made in nuclear reactors
nuclear fission
advantages of nuclear reactors
- produce useful and important radionuclides
- produce nuclides with long enough half lives to be transported
disadvantages of nuclear reactors
- expensive to build and maintain
- production of radioactive waste
- expensive to run
- few and far
how do cyclotrons work
- produce a beam of charged alpha particles which are used to bombard target material
- resulting nuclide will have excess charge so will decay by emission of positively charged particle
what are the radionuclides produced from cyclotrons used in
- PET
- production of fluorine (F18)
advantages of cyclotrons
- cleaner production than reactors
- wide range of nuclides producible
- wide range of possible techniques
disadvantages of cyclotrons
- expensive to install and maintain
- very large
- radionuclides have to be ordered in advance
- radioactive waste
- not energy efficient
what are generators
- used to produce steady supply of isotopes by allowing precursor to decay over time
- separates parent and daughter nuclides as some cases; daughter nuclides have shorter half life
elution
separating parent and daughter nuclide
how is the generator eluted
- using saline
- atm will force saline out of generator
- pouring saline through column of immobilized 99Mo elutes the soluble 99mTc
- resulting saline solution contains 99mTc
- salien is them extracted and placed directly in a sterile evacuated vial
radionuclides for RNI ideal properties
- physical half life short enough to reduce patient dose but long enough for scanning
- short biological half life
- emits gamma rays that are energetic enough to leave body
- not toxic
- cheap
what does product labelling include
- statement that productive is radioactive
- name of pharmaceutical preparation
- if prep is for diagnostic or therapeutic use
- route of administration
- expiry date
- batch number ]
- total radioactivity present
common PET pharmaceutical
FDG - F18
- goes anywhere that is metabolising glucose
- used for oncology, cardiac and brain imaging
common pharmaceutical of GAMMA/SPECT bone scans
pertechnetate - 99m TC
- easily to produce
common pharmaceutical of PET prostate imaging
PSMA - 68Ga
- newer PET tracer for prostate imaging
common pharmaceutical of GAMMA/SPECT for cardiac stress scans
sestamibi - 99mTc
taken up by heart muscle
