Topic 3: Radionuclides and Radionuclide Generator Systems. Generator for Producing 99mTc. Single Photon and Positron Emitters. Radiopharmaceuticals for Diagnostics and Therapy.
A radionuclide is an unstable atom that undergoes radioactive decay by emitting radiation to become stable.
They emit:
- Gamma rays
- Beta particles
- Positrons
- Alpha particles
depending on the isotope.
Characteristics of an Ideal Diagnostic Radionuclide
An ideal radionuclide should have:
- Pure gamma emission
- Short half-life
- Appropriate photon energy (100–200 keV)
- Low radiation dose
- High image quality
- Easy availability
- Chemically stable
- Easy labeling with pharmaceuticals
The best example is: 99mTc (Technetium-99m)
Radionuclide Generator
A radionuclide generator is a device that continuously produces a short-lived radionuclide from the decay of a long-lived parent radionuclide.
Think of it like a "radioactive factory."
Instead of transporting a short-lived isotope from another city every day, hospitals receive the parent isotope and generate the daughter isotope whenever needed.
Why are generators needed?
Many radionuclides have very short half-lives.
Example:
Tc-99m
↓
Half-life = 6 hours
It would decay before reaching many hospitals.
So hospitals receive a generator instead.
Technetium-99m Generator (Very Important)
Also called Molybdenum-Technetium Generator Or 99Mo/99mTc Generator
Parent Nuclide
Molybdenum-99 (99Mo)
Half-life ≈66 hours
Daughter Nuclide
Technetium-99m (99mTc)
Half-life- 6 hours