nucs physics Flashcards
band of stability
balance of protons and neutrons
alpha decay
-release of He (2n + 2p)
-high linear E transfer (heavy, lim range (1 cm/meV)
-not used in img, used in therapy
radioactive decay
releasing excess neutrons or protons to reach balance
b-decay: too many neutrons or protons? What’s formed?
-too many neutrons
-b-particle, positively charged nuc, anti-neutrino (massless, balance out E)
b-particle
negative charge ejected from nucleus during b-decay to form balanced nuc
isobaric transition-what is it, what does it occur with?
-no change in mass (because you lost neutron and gained positive charge but they weigh the same)
-occ with b-minus, b-positive (positron emission & electron capture)
how do you block b-emission in a syringe?
plastic shield (low Z). if you used high Z (ex: lead) –> bremmmstahlung xray
What sort of b-decay occ with too many protons and not enough neutrons?
1) b-positive
2) electron capture
b-positive decay: what does it require?
1.02 MeV
what’s formed with b-positive decay?
positron + neutrino (worthless POS for balancing E)
what occ with b-positive decay?
positron emitted, collides with electron –> two 511 keV photons emitted 180˚ apart from each other
electron capture
a nucleus with too many protons steals an electron from inner (K) shell to become neutral
is b-minus decay good for img?
No, electron emission can damage DNA (basis of radionuclide therapy)
is e-capture good for img?
yes, bc it’s linked to isomeric transition which results in emission of char gamma photon which can be imaged under gamma camera
isomeric transition
emission of E (ex: in form of gamma photon) after isobaric transition as a final step to create nuc stability
-mult gamma photons released=mult peaks, ex: Ga67, In-111
what does the m stand for in Tc99m
metastable
metastable
intermediate state after isobaric transition and before isomeric transition
3 types of tracer production
1) cyclotron (particle zips through vacuum and gains charge)
2) nuclear reactor
3) radionuclide generator
Cyclotron-produced radioisotopes
molybdenum-99
Fluorine-18
Gallium-67
Thallium-201
*mother fucking gargantuan technique
nuclear reactor generation: how does it work
fission of 235Uranium –> fission neutrons –> react with 235Ur to create a second fission event –> creates 236Ur –> high E neutron (collide with H2O which slows it down)
Reactor produced radioisotopes
-Molybdenum 98 (which is then put into cyclotron tomato moly 99)
-iodine 131
-xenon 133
-thal-201
generator produce radionuclides
-T99m
-Krypton 81m
radionuclide purity
-how much Mo in Tc
-tested in dose calibrator
-0.15 micro curies of Mo per 1 millicurie of Tc
chemical purity
-how much Al in Tc?
-tested with pH paper
-<10 micrograms Al per 1 mL Tc
radiochemical purity
-how much free Tc?
-tested with thin layer chromotography
-95% NaTcO4
-92% sulfur colloid
-91% all other Tc pharmaceuticals
transient equilibrium
half life of daughter a little shorter than parent
-classic ex: Moly-99 & Tc
secular equilibrium
half life of daughter way shorter than parent
physical half life
am of time required for radionuclide to be reduced to half of its existing ac
biologic half life
how long it takes body to get rid of half the tracer
effective half life
1/2 physical half life + 1/2 bio half life
effective half life
1/2 BHL + 1/2 PHL
how long do you have to keep radioactive material
10 half lives
activity
am of disintegration per second measure in Becquerel (Bq)=1 disintegration per secdon
specific activity
activity per unit mass (Bq/g)
*longer the half life, lower its specific act
