RNI Flashcards
What are radionuclides, and how do they differ from radioisotopes?
- Radionuclides are radioactive elements with unstable nuclei that release radiation through nuclear decay.
- the correct term in nuclear medicine is radionuclides because:
- Radionuclides encompass all radioactive atoms, whether they are isotopes of the same element or not.
What are the key characteristics of radionuclides?
- Unstable Nucleus: An imbalance of protons and neutrons causes instability.
-Radioactive Decay: Emit alpha (α), beta (β), or gamma (γ) radiation to become stable.
-Energy Emission: The emitted radiation can be detected and used for imaging or therapy.
How are radionuclides named and identified using standard notation?
Element Name: Specifies the chemical element (e.g., Technetium, Iodine).
Mass Number: The sum of protons and neutrons in the nucleus.
For example, Technetium-99m (99mTc) is a radionuclide where 99 is the mass number, and “m” indicates a metastable state.
What is radioactive decay, and how does it work?
Radioactive Decay: A natural process where an unstable nucleus releases energy to become stable.
How it works:
1 -The unstable nucleus has an imbalance of protons and neutrons.
2- It emits particles (alpha or beta) or energy (gamma rays) to achieve stability.
3- This transformation may result in a new element or isotope (daughter nuclide).
Explain the differences between alpha, beta and gamma decay?
Alpha decay:
- Emits an alpha particle (2 protons + 2 neutrons, like a helium nucleus).
- Results in a decrease in the atomic number by 2 and the mass number by 4.
Beta decay:
-A neutron transforms into a proton and emits a beta particle (electron or positron).
-Increases or decreases the atomic number by 1 but keeps the mass number unchanged.
Gamma decay:
Releases gamma rays (high-energy electromagnetic radiation) without changing atomic or mass numbers.
What are the parent nuclide and daughter nuclide in radioactive decay?
Parent nuclide: The original unstable nucleus before decay.
Daughter nuclide: The resulting nucleus after decay, which may or may not be stable.
Radionuclides are produced through three primary methods, what are they?
1- Cyclotron:
Accelerates charged particles (e.g., protons, deuterons) to bombard stable materials.
Produces radionuclides like 18F and 11C for PET imaging.
2- Nuclear Reactor:
Uses fission reactions or neutron activation to produce radionuclides.
Produces commonly used radionuclides like 99Mo and 131I.
3- Radionuclide Generator:
Contains a long-lived parent radionuclide that decays into a short-lived daughter radionuclide.
Example: 99Mo/99mTc generator for SPECT imaging.
What factors influence the choice of radionuclides for diagnostic and therapeutic applications?
1 -Type of Application:
Diagnostic: Requires radionuclides with short half-lives to minimize radiation exposure while providing clear images (e.g., 99mTc, 18F).
Therapeutic: Uses radionuclides with longer half-lives for sustained radiation targeting specific tissues (e.g., 131I for thyroid cancer).
2- Imaging Modality:
- Gamma emitters for SPECT (e.g., 99mTc).
- Positron emitters for PET (e.g., 18F).
3- Half-Life Matching:
The radionuclide’s half-life should align with:
- The biological process being imaged.
- The duration of therapeutic efficacy.
4 - Energy Level:
Gamma rays must have energies suitable for clear imaging without excessive radiation dose.
How does half-life affect the suitability of a radionuclide for imaging or therapy?
- Short Half-Life:
Suitable for rapid imaging of biological processes.
Example: 15O (2 minutes) for brain perfusion. - Intermediate Half-Life:
Ideal for diagnostic imaging, balancing imaging time and radiation exposure.
Example: 99mTc (6 hours). - Long Half-Life:
Suitable for therapeutic applications, providing sustained radiation to target tissues.
Example: 131I (8 days).
How are radionuclides attached to biological molecules for imaging and therapy?
1- Labelling Process:
- The radionuclide is chemically bonded to a biologically active molecule (e.g., peptides, antibodies).
- This molecule targets specific tissues or processes in the body (e.g., glucose metabolism, cancer cells).
2- Controlled Conditions:
- Solvents, temperature, and purification methods are carefully managed to ensure the radiopharmaceutical is safe and effective.
Examples:
18F is attached to glucose molecules (FDG) for PET scans to track metabolism.
What is a radiopharmaceutical, and how is it administered?
Radiopharmaceutical: A compound consisting of a radionuclide bonded to a biologically active molecule, used for diagnostic imaging or therapy.
Common Administration Methods:
1- Intravenous (IV): Most common, ensuring rapid delivery to target tissues.
2 -Oral: Example: Iodine-131 capsules for thyroid therapy.
3 - Inhalation: Example: 99mTc aerosols for lung ventilation studies.
What are the differences between diagnostic and therapeutic radiopharmaceuticals?
Diagnostic Radiopharmaceuticals:
- Use radionuclides with short half-lives.
- Emit gamma or positron radiation for imaging (e.g., 99mTc, 18F).
Therapeutic Radiopharmaceuticals:
- Use radionuclides with longer half-lives.
- Emit alpha or beta particles to deliver localized radiation to diseased tissues.
How are radiopharmaceuticals purified?
Purification:
- Removes unwanted by-products and impurities from the chemical reaction.
- Ensures only the desired radiopharmaceutical is present.
How are radiopharmaceuticals sterilized after production?
1- Micromembrane Filtration: Removes microorganisms using a 0.22 µm filter before transferring the product into a sterile vial.
2- Autoclaving: Uses steam under pressure to eliminate bacteria and ensure sterility.
Why is automation important in the synthesis of radiopharmaceuticals?
1- Safety: Reduces radiation exposure to staff.
2- Consistency: Produces high-quality radiopharmaceuticals with fewer errors.
3- Efficiency: Allows for faster production, essential for short-lived radionuclides.
Synthesis Modules:
Automated systems that mix, label, and purify radiopharmaceuticals under sterile conditions.
