Radiopharmacy Flashcards
What are the
Radiation Measurement Units?
Measure of radiation energy in tissue
- Sievert (Sv)
- Use 1/1000 (milli Sievert – mSv)
- Or 1/1000 000 (micro Sievert - Sv)
o Sievert = Gray x quality factor (QF)
o For and emitters, QF = 1
What is lung perfusion performed by?
Lung perfusion imaging performed by IV injection of 99mTc MAA (macroaggregates of albumin typically 30-50mm)
- Lung ventilation carried out in conjunction with perfusion
- Radioactive gases such as 81mKr may be used
- More readily available is 99mTc Technegas (this is a machine)
What is the Most common indication for bone scan?
- is to assess bone metastases usually 2o (secondary) to Ca (carcinoma) breast and prostate
- Medronate or oxidronate (bisphosphonates) is injected and the patient scanned 3 hours later to look at skeleton
What is used for diagnosis and management of Coronary artery disease?
Nice guidelines 2003 state that MPI (Myocardial Perfusion) scintigraphy using SPECT
• Patients undergo MPI in 2 parts
- Heart stressed by exercise or pharmacologically using adenosine or dobutamine (to see if there is an increase of blood flow. Only do a rest scan if this scan is abnormal)
- Heart imaged at rest (for comparison)
What is the radiopharmaceutical used for Cerebral blood flow imaging?
HMPAO Ceretec
What is used to differentiate essential tremor from Parkinsonian syndrome in patients where diagnosis uncertain and DLB (form of dementia – course of disease is quicker) from Alzheimer’s disease?
123Ioflupane DaTSCAN
What can Salivary activity and secretion can be monitored by?
pertechnetate
What is used to study gastric emptying?
Tc-colloid mixed with food or drink
Oesophageal transit (for swallowing problems) measured using Tccolloid in tomato soup
What is used to assess GI bleeding?
• using Tc labelled RBC (in vitro test).
What is becqurel?
– rate of disintegration (1 d.p.s) – how many molecules are given off (1 disintegration per second is 1 becquerel)
What is a Gray unit?
Gray (Gy) - S.I. unit of absorbed dose.
What are the types of radioactive decay?
a - particles
B - particles
B + particles
Gamma rays
Describe alpha particles
- He nucleus - charge + 2
- comparatively large – collide with tissue, give up their energy, cause ion pairs (5000 cm-1)
Range - few mm
• can easily be shielded
• NO role in diagnostic agents, but have potential for therapeutic use
Describe Beta particles
• can have negative or positive charge
o smaller than alpha particles – less interaction with tissue (50 ion pairs cm-1 )
o less damage and greater range in tissue – not that good level of treatment
o range can be up to several cm. – depends on energy Emax and Emean
o valuable for THERAPY, but not diagnosis
What are B+ particles?
- known as positrons – antimatter
- immediately after B i particles emission from nucleus, they interact with - particle
- Annihilation reaction – matter is converted into energy B+ + b- -> 2gamma
- energy of each = 511keV, emitted at 180o to each other
- valuable in DIAGNOSTIC procedures
What are gamma rays?
- electromagnetic radiation – not particles
- so therefore less interaction with tissue, cause less damage, have greater range in tissue
- energy of emitted gamma ray(s) constant for a given radionuclide
- valuable for DIAGNOSTIC use, especially when radiation can be detected externally
What are the Ideal Properties of Diagnostic Radionuclides ?
- Gamma ray emission only
- high abundance
- reduce radiation dose to patient - For imaging studies, gamma energy 100 - 250 kev
- high detection efficiency
- no significant body attenuation
- easy to shield
3.Physical half-life approx. 1.5 times duration of test
- Simple cheap and rapid production
- lack of radionuclidic impurities
- high specific activity
- rapid prodyction reduces operator dose - Versatile chemistry
- chemical quantity – no pharmacological effect
- Radiochemically pure – biodistribution profile
- Chemically stable – doesn’t break down in vivo
- Predictable biodistribution
What is Technitium -99m?
Sourced from Molybdenum (Mo99)
Technitium 99m produces a gamma photon to form technetium 99 and then another gamma photon to Ruthenium 99.
m = metastable state (one of electron is at a higher level – it drops to a lower state).
Ruthenium 99 is stable
Molybdenum and technetium have different chemical properties and can be separated.
How is Technitum generated?
- Essential feature is a shielded glass column containing alumina
- Mo-99, as molybdate is strongly adsorbed on to column
- Column is sealed, sterilised, packed into generator
- Dispatched to hospital radio-pharmacy department
- On column Mo-99 decays to Tc-99m, which is separated
- Separation achieved by passing saline through the column. Mo-99 doesn’t dissolve in saline.
What Happens On a Molybdenum Column?
Mo decays to Tc-99 and leaves Mo behind.
What is the Radionucleic Purity / Identity?
o ‘The radionucleic, expressed as a percentage, of the radioactivity of the Radionuclide concerned to the total radioactivity of the source’
What imaging is
Sodium (99m Tc) pertechnetate mostly used for?
• Most common indication is thyroid imaging
• Why is pertechnetate taken up by thyroid?
TcO4 has similar shape and size to iodide
TcO4 tetrahedral vol 4.0x10-23cm3
Iodide spherical vol 4.2x10-23cm3
What happens inside a Technetium radiopharmaceuticals kit?
Tc99 eluted in most stable oxidation state (+7) - all 7 electrons shared with 4 oxygens
What are the Precautions of a Technetium radiopharmaceuticals kit?
- NEVER inject air into any Technetium radiopharmaceutical vial
- The oxygen in 0.1ml air can oxidise the stannous ion used in many commercial kits as a reducing agent
