moly generator radiopharm

where does Moly come from?

nuclear reactors

what are two types of nuclear reactors

fission and neutron capture

characteristics of fission in nuclear reactors

self sustaining in controlled chain reaction, carrier-free, high specific activity, neutron rich, generally beta negative emitters

characteristics of neutron capture for nuclear reactors

most common is n,gamma, target is stable and product is radioactive, only a fraction of the target atoms will undergo neutron activation

fuel cells

contain uranium

moderators

slow down fission neutrons so that theyre more likely to create a chain reaction, D2O, berylium and graphite

control rods

expose or shield fuel cells to control the reaction, absorbs neutrons but does not undergo nuclear fission, boron, cadmium, silver, indium, or halfnium

coolant

usually water

nuclear reactor components

moderator, control rods, coolant, shielding, pressure vessel, fuel cells

Moly generator principles

radioactive parent and radioactive daughter, long parent t1/2, short daughter t1/2, chemically different, parent remains in generator

elution

process of daughter removal

eluant

solvent used to collect daughter

eluate

collected solution containing the daughter

what is used for shielding

lead, depleted u238, tungsten

transient equilibrium generator

parent t1/2 10-100x the daughter, Mo99/Tc99m

secular equilibrium generator

parent t1/2 1000x the daughter, Ge68/Ga68, Sr82/Ru82

most common type of moly generator

negative pressure dry column

chromatographic generator

most commonly used, alumina column generator, moly attached to aluminum

parts of a moly column

needle, column support, rubber stopper, glass wool, silicar, aluminum oxide, glass filter

wet column disadvantages

radiolysis of water, crack in cold weather, air bubbles

dry column disadvantages

one more step, extra vial and larger elution vial

wet column advantages

easy, reliable, consistent yield

dry column advantages

only one extra step, reliable, consistent yield

radiolysis

dissociation of molecules by radiation, cleavage of one or several chem bonds resulting from high energy flux, produces free radicals

free radicals

unstable and react quickly with other compounds trying to capture needed electron to gain stability, chain rxn

free radicals are…

oxidizing agents

antioxidants

donate an electron stopping damage from free radicals, stabilizers

missing Tc99m activity only

elute again, due to self radiolysis, channeling, column leakage

missing activity and volume

elute again with close attention, reverse elute, could be due to air bubbles, air leaks, tubing and mechanical problems

channeling

column material bed disrupted, liquid passes thru column without permeating column material, to fix drop it or max volume elute

quality control types

radionuclidic breakthrough, chemical testing, radiochemical testing

radionuclidic testing

moly breakthrough, detected by mo99 energy in dose calibrator at energy levels of 740 and 780 keV

NRC limit for moly breakthrough

0.15 uCi Mo99/ 1 mCi Tc99m at time of administration

chemical testing

aluminum breakthrough, contamination from generator, detected by colorimetric method

NRC limit for aluminum breakthrough

10 ug Al/ 1 ml Tc99m

causes of moly breakthrough

exceeding the ion exchange capacity of alumina, pH of eluate greater than 7, channeling, excessive elution