Radiopharmacy Flashcards
(18 cards)
What are radioactive drugs administrated to patients for?
Diagnostic purposes
Therapeutic purposes
Used for imaging or non-imaging
Uses ionising radiation - gamma, beta, alpha
Name the three types of nuclear decay
○ Alpha: Helium nuclei
○ Beta: Negatron from neutron decay
○ Gamma: Photon emission (no particles)
Describe gamma camera
Detects gamma radiation
Uses
- collimator - reduces scatter
- Sodium iodide crystal - converts gamma to light signal
Produces a light pulse
Name the two parts that radiopharmaceuticals are made up of
made up of 2 main parts:
1) Carrier/vector - directs the radioactive material to a specific organ or tissue
2) radionuclide - emits the detectable signal (usually gamma rays) picked up by the gamma camera
How are radio-pharmaceuticals prepared?
The vector is freeze-dried
Reconstituted with:
- a specific amount of radioactivity
- diluted saline
After a fixed incubation period, individual patient doses are drawn up
Name the most common radionuclides
○ Technetium-99m (Tc-99m) – most common (6 hr half-life, 140 keV gamma)
○ Others: Thallium-201, Indium-111, Iodine-123/131, Gallium-67
What are the advantages of Tc-99m?
Short half-life - half life - 6 hours -> ideal balance between enough time to perform scans, minimal long-term radiation exposure to the patient.
Retrievable for approximately 2 weeks, making it practical for regular use
Low energy gamma emitter - good for imaging - absorbed well by Nal crystals in gamma cameras. too high -> passes through detector, too low -> may be undetectable -> poor image
Easy to manufacture
Forms a wide variety of complexes - kit contains reducing agents like stannous chloride to lower Tc’s oxidation state and enable complexation. Can bind to SH, OH, NH2 -COOH groups. Some kits require heating to achieve further reduction
Decays to a stable isotope - after 5 half-lives >95% of activity decays -> can then be disposed of as standard waste
What are the key differences between aseptic services and radiopharmacy?
- Radiopharmacy includes:
○ No prescription needed
○ Aseptic handling
Legislation
○ Dose calculations (in MBq)
○ Quality Control (QC): e.g., chromatography
○ Operator and environmental safety (legislation applies)
Name the additional roles of the radiopharmacist
Clinical Pharmacy
E.g. Adjuvant drugs
Drug Information
E.g. Breast feeding
Teaching and training
Research and development
Clinical trials
Name some common radiopharmaceuticals
MAA
an Aerosol
Pertechnetate
Phosphate Complex
a Colloid
DMSA
for labelling cells
Porridge!
Describe radiopharmaceuticals and kidney scans
MAG 3
Investigate if kidney is functioning
Left kidney has very poor throughput of tracer
Help surgeons :
- pre surgery
- post kidney transplant
Describe the use of DMSA
Passes through glomerulus but reabsorbed in distal tubules
65% bound to renal tubules
Function & renal outline
Renal scarring
Used extensively in paediatric nephrology
Describe the use of RP in lung scans
- Ventilation: Inhaled krypton-81 gas. Compare image with perfusion
- Perfusion: MAA injection; mismatch suggests PE. Cold spots if no perfusion
Describe the use of RP in the thyroid
- Uses pertechnetate (TcO₄⁻) which mimics iodine
- Also used in Meckel’s diverticulum scans (stomach)
Describe the use of RP in the bone
- Organic phosphate complex targets bone turnover
Identifies bone metastases
Describe the use of RP in the liver and lymphatics
- Colloids (not commonly used now) for lymphoscintigraphy and sentinel node localization
Particle size denotes usage
Describe the use of RP in cell labelling
- WBCs: For infection/inflammation
- RBCs: GI blood loss, cardiac imaging
- Platelets: Clot detection
Describe the use of RP in GI
GI Transit:
* Defecating Proctoscintigraphy:
○ Radioactive porridge simulates stool
○ Measures colonic transit time and evacuation dynamics
