Radioactivity Flashcards
transmutation
atom changing to another atom type
disintegration
nucleus changes its structure = change in mass number or atomic number
are larger Z more unstable or stable
unstable, as they are larger
more stable =
more neutrons
isotopes
different number of protons same number of neutrons
what are the decay types
positron
k-electron capture
gamma
beta
alpha
how does a nucleus become stable
emitting a particle
energy in the form of a gamma ray
alpha
only ejected if the atomic mass is 150+
occurs when there’s too few neutrons
doesn’t travel far
doesn’t penetrate deep
highly ionising
beta negative
too many neutrons [negatrons: -ve electric charge]
neutron -> potron + e/beta + antineutrino
emission of the beta causes transmutation to a different atom
atomic number increases, mass number stays the same
beta positive
too many protons, an antimatter equivalent to an electron (positron: positive electric charge)
proton -> positron + neutron (remains in nucleus)
positron + electron = annihiliation
positron reacts with the electron releasing two gamma rays (0.51MeV) emitted 180 degrees
beta have a equal mass to an electron
gamma
emitted from the nucleus
wavelength of 10^-8m or less
electron captures
too many protons not enough neutrons, pull an electron in
proton captures an inner electron and converts into a neutron which breaks the unstable nucleus. Nucleus changes from a high to low energy state
excess energy is released as a gamma ray
unstable nucleus emits a beta particle
very penetrating
where do isometric transitions occur
emission of gamma ray = internal conversion
standard definition of activity
activity of preparation:
amount of disintegrations or nuclear transformations occurring in a substance
or number of decays per unit time
definition of activity
number of transformations per second from one gram of radium
half life effective =
physical half life + biological half life
conversions of mCi in Bq
1mCi = 37MBq
1Ci = 37GBq
1Ci = 37,000,000 Bq
what is the average life
amount of time it remains reactive in the nucleus
physical half life
time taken for an element to half its activity
biological half life
may vary dependent on if any abnormal pathology is present, or removal of any material by metabolic or excretory processes
effective half life
time taken for an element in the organ to decay to half its original activity by metabolic process. Depends on the half life of the radioactive decay and the time taken for the radiopharmaceutical to be excreted
what is a therapeutic dose
I-131
what dose do you image and not treat
I-123
short half life
cheap to manufacture
less dose to patients etc
low residual activity
long half life
essential for unsealed sources
iridium- 192
half life = 74 days
may be used in after loading equipment for brachytherapy
beta particle emitted
gamma ray energy = 296-613 KeV
high specific activity
stepping source on an inert wire, activated by neutron irradiation
is iridium - 192 permanent or temporary
temporary
iodine-125
60 day half life
electron capture
gamma energy = 35kev
produced by neutron activation
use: kinden immunoassay, prostatic cancer, delivering high doses with min SE
is I-125 permanent or temporary
permanent
caesium-137
artificially manufactured
30 year half life
effective for 20 years
beta particle emitted
gamma energy = 0.667 MeV
moderate specific activity
metal casing, stainless steel to absorb beta particle
is caesium-137 permanent or temporary
temporary
colbalt-60
half life is 5.27 years
beta particle emitted
gamma ray emitted = 1.17Mev + 1.33 MeV
high specific activity
in bead form in high dose after loading equipment
is Co-60 permanent or temporary
temporary
palladium - 103
17 day half life
electron capture
gamma energy = 21 Kev
produced by cyclotron
implanted into the prostate gland
covered onto two graphite pellets in between is a 1mm long lead marker to show up radiographic film
is palladium -103 permanent or temporary
-
gold- 198
2.7 day half life
implanted into tongue, prostate or lip
412 kev gamma energy
implanted in seed form
encapsulated by platinum
is gold-198 permanent or temporary
-
iodine-125 ophthalmic seed implants
uveal melanoma
in porous ceramic
gold marker
titanium capsule
