What are the 2 types of radiation?
1. ionising - radiation removes electrons from atoms to form ions (carcinogenic)
2. non-ionising - radiation cannot create ions but has thermal or photochemical effects
Application of ionising radiation?
Radiology (X-rays and CT(computed tomography)
Applications of non-ionising radiation?
What is brachytherapy?
Using radioactive needles to direct radiation onto tumours
What is SPECT? How does it work?
Single photon emission computed tomography
Select a particle that will go to a specific area you want to look at. Add a low damaging radioactive label to it. You can now study the area. eg. flow rates in the kidney
What is PET/CT?
positron emission tomography and computed tomography
*high CT radiation dose
What is the unit describing radiation dose absorbed by an organ?
This is a very large unit - a human would die within 30 days with an exposure of 10 Gray
We give tumours 80-100 Gray
What is the unit of effective dose?
Whole body acute lethal dose = 5-7 Sv
Annual background in Sydney = 2.3mSv
CT chest/abdo/pelvis = 20mSv
Describe the process of radiation interaction with the body
1. energy absorption and ionisation (~instantly)
2. interaction of ions with molecules and formaiton of free radicals (~instantly)
3. free radicals interact with molecules, cell and DNA (seconds)
4. Cell death, changes in DNA (minutes to years)
List 5 radiation protection precautions
1. Time - longer exposure, higher dose
2. Shielding - high density, thickness and atomic number required. includes aprons, and walls (2mm lead radiography, 25mm lead PET, 2500mm concrete for radiotherapy)
3. Distance - decreases by 25% when you twice the distance
4.Personal monitoring - we use 20% of international annual limit doses (2x natural background radiation)
5. Radiation protection bodies sets regulations
What can go wrong with radiation?
Wrong patient, area, dose
Pregnancy - foetus risk is of development problems or later life cancer