wk3 radiopharmacy basics

Practice vocabulary flashcards covering atomic structure, radionuclide production, generator systems, and radiopharmaceutical principles based on the MRSC1350 Radiopharmacy lecture.

Atom

A sphere made up of a small nucleus (protons and neutrons) surrounded by a region of space populated by electrons; it cannot be broken down without changing its chemical nature.

Isotopes

Nuclides with the same number of protons but a different number of neutrons, belonging to the same element.

Nuclide

An atom characterized by its mass number ($A$), which is the total number of protons and neutrons.

Radionuclide

A nucleus that is in an unstable state and seeks stability by ejecting portions of its nucleus or emitting energy in the form of photons ($\gamma$ rays).

Radioactive Decay

The process by which atoms with an unstable combination of protons and neutrons regain stability by shedding radioactive energy in the form of alpha, beta, or gamma rays.

Physical Half-Life ($T_p$)

The time required for a radionuclide to be reduced by half of its existing radioactivity; it is unique to every radionuclide and independent of conditions.

Biological Half-Life ($T_b$)

The time it takes for an organism to eliminate half of an administered radiopharmaceutical.

Effective Half-Life ($T_e$)

The time taken for a radionuclide to decrease to half its initial value due to the combination of biological elimination and radioactive decay, calculated as T_e = (T_pxT_b)/(T_p+T_b)

Theranostics

A field of 'precision medicine' that combines specific targeted therapy based on specific diagnostic tests.

Becquerel (Bq)

The SI unit for radioactivity measurement, defined as one radioactive decay per second ($1\,Bq = 1\text{ decay/s}$).

Nuclear Fission

The process of splitting a nucleus into two smaller nuclides, such as adding a neutron to $^{235}\text{U}$ to form very unstable $^{236}\text{U}$, which then splits and releases energy and free neutrons.

Moderator

A material, such as heavy water or graphite, used in a nuclear reactor to slow down (thermalise) fission neutrons to make them more efficient at initiating additional fission events.

Control Rods

Strong neutron absorbers used in a nuclear reactor to control the chain reaction and prevent a reactor meltdown.

OPAL

The Open Pool Australian Lightwater research reactor, a $20\text{ Megawatt}$ reactor opened in 2007 that uses low enriched uranium (LEU) fuel containing approximately $20\%\,^{235}\text{U}$.

Cyclotron

An accelerator device that uses magnetic fields ('D’s') and an electric field to increase the energy of charged particles in spiral paths to enable a nuclear reaction on impact with a target.

Elution

The process of regular separation and extraction of a daughter radionuclide from a parent radionuclide within a generator system.

Transient Equilibrium

A parent-daughter relationship where the half-life ($T_{1/2}$) of the parent is $10-100 \times$ greater than that of the daughter.

Secular Equilibrium

A parent-daughter relationship where the half-life ($T_{1/2}$) of the parent is $100-1000 \times$ greater than that of the daughter.

Radionuclide Purity

The proportion of the total radioactivity present as the stated radionuclide; in a $^{99}\text{Mo} - ^{99\text{m}}\text{Tc}$ generator, this is determined by a $^{99}\text{Mo}$ breakthrough test.

Chemical Purity

A measure of chemical contaminants in the eluate, such as aluminum ions in a $^{99\text{m}}\text{Tc}$ generator eluate, which must be < 10\,\mu\text{g/mL}. house

Metastable (m)

An intermediate excited state of an isotope (e.g., $^{99\text{m}}\text{Tc}$) where the daughter nucleus remains in an excited state for a considerable time (>1\,\mu\text{s}) before undergoing isomeric transition.

Radiopharmaceutical

A compound used for human use that consists of a radionuclide and a pharmaceutical; it must be sterile, pyrogen-free, and ideally exhibit a high target to non-target activity ratio.

Radiochemical Purity

The ratio of radionuclide present in its bound form (as the radiopharmaceutical) to the radionuclide present in its unbound or 'free' form.

Biodistribution

The distribution of compounds within a biological system or organism, which varies over time and can be affected by blood supply, extraction, and excretion.

Adverse Reaction

An unanticipated patient response (typically allergic) to the nonradioactive component of a radiopharmaceutical, occurring at a rate of approximately $1:100,000$.