Radioactivity Flashcards
Define Radioactivity
Spontaneous emission of radiation, either directly from unstable atomic nuclei or because of a nuclear reaction
What is the annual millisievert exposure?
20 millisieverts
How can you use radionuclides in diagnostic nuclear medicine
Function and anatomy
Nervous system
Circulatory system
Skeletal system
Urinary system
What happens when there are too many neutrons in the nucleus?
Radioactive decay
What happens when there is too many protons in the nucleus?
Positron emission
What is an Isobar?
different Z, same A
What is an Isotope?
same Z, different A
What is an Isomer?
same Z and A
What does Isomeric mean?
From metastable (radioactive) to ground state (stable)
How can a nucleus be unstable?
Too many protons or neutrons
Or incorrect arrangement
What does a becquerel represent?
SI unit
1 nuclear disintegration per second
Rate of decay
(Bq)
Repulsive forces
Exist between protons
Attractive forces
Exist between neutrons over short ranges
What are the two types of Beta particle decay
Negatron B- emission
Positron B+ emission
Explain Negatron B- emission
When a nucleus has too many neutrons, the N:P ratio is too high
A B- particle results from the transformation of a neutron in the nucleus to a proton
The B- particle may carry a part of the energy released, and shares part of the energy with an antineutrino which is ejected at the same time.
The number of neutrons decreases, the number of protons increases (decreasing neutron: proton ratio)
Explain Positron B+ emission
The emission of a positive Beta particle is associated with the breakdown of nuclides which have too many protons, the N:P ratio is too low
Proton turns into neutron within nucleus
A proton is emitted with a positron (positron emission)
As a result, the number of neutrons in the nucleus is increased by 1 and the number of protons is reduced by 1
Electron capture
When a nuclide has too many protons, the nucleus captures one of the K shell electrons and combines it with a proton to form a neutron
This results in orbital vacancy which produces a cascade effect in the electron shells to fill the vacancy
This releases energy in the form of characteristic radiation
Physical vs biological half-life
Physical- the time taken for the element to decay by half
Biological- influences that change the radioactive dose to the patient (hydration, location)
Why is a shorter half-life beneficial?
Cheaper
Patients/staff receive less radiation
Residual activity is low
What to do when a radioactive spill occurs
Inform
Confine/contain
Decontaminate
