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50 Cards in this Set
- Front
- Back
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What is a positron? |
Positively charged Beta radiation |
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What is the positron's antiparticle? |
The electron (same mass but charge of -1 not +1) |
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What happens when a positron and electron collide? |
They are obliterated in annihilation |
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Why are neutrons sometimes called "indirectly ionising"? |
They are not directly ionising however they can be absorbed by the nucleus of atoms in substances they pass through making them radioactive and so they emit radiation |
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How penetrating is neutron radiation? |
More than alpha and beta and sometimes more than gamma |
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What is neutron radiation shielding made from? |
Neutrons are absorbed best by light nuclei such as hydrogen so water, polythene, concrete and other hydrogen rich materials are used Neutron absorption also often makes nuclei emit gamma radiation so to protect against this thick lead is also added to neutron radiation shielding |
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What things can make a nucleus unstable? |
Too many neutrons Too few neutrons Too many protons and neutrons Too much energy |
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How is the stability curve plotted? |
Number of neutrons plotted against number of protons for stable atoms to give curve of stability |
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If an atom was not on the line of stability what would it be? |
Unstable |
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If an atom is above the curve why is it not stable? Below? |
Too many neutrons Below too many protons |
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When does Beta decay occur? What happens to the nucleus? |
When there is too many neutrons Neutron changes to proton and electron Atomic number increases by one Mass number stays the same |
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When does Beta plus decay occur? What happens to the nucleus? |
When there are too few few neutrons Proton gets changed to neutron and positron Atomic number decreases by one Mass number stays the same |
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When does alpha decay happen? What happens to the nucleus? |
Only in heavy atoms with high proton value (more than 82) when nuclei of the atom is too massive to be stable Atomic number decreases by two Mass number decreases by four |
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When does gamma radiation get emitted? What happens to the nucleus? |
When nucleus has too much energy often after alpha or beta decay Excess energy lost by emitting gamma rays Gamma never emitted on its own Proton and neutron numbers don't change |
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What are protons and neutrons made up of? |
Quarks |
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What are the charges and masses of up and down quarks? |
Up +2/3 and 1/3 Down -1/3 and 1/3 |
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What are the quark configurations of protons and neutrons? |
Proton uud Neutron udd |
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What happens when quarks change? |
They produce electrons or positrons |
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How would a neutron change to a proton in an unstable atom? |
By changing a quark Down quark changes to up quark udd -> uud |
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Why is a electron produced when a neutron changes to a proton? What is this called |
Because the overall charge must be the same before and after This is Beta minus decay |
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What is released when a proton changes to a neutron why? What is this? |
A positron To keep the overall charge the same This is beta plus decay |
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How is a tracer used in medicine? |
Tracer injected or swallowed and an external detector follows its progress as it moves round the body and a computer uses the reading to create an image of where the strongest reading of radiation is coming from |
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What isotope of iodine is used in some tracers and what is it used to do? |
Iodine 131 which is absorbed by the thyroid gland and gives out radiation which can be detected to see if the gland is working properly to take in iodine as it should |
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What kind of radioactive isotopes should be used as tracers in medicine? |
Beta or gamma emitting isotopes so the radiation can pass out of the body Short half life to limit the amount of radioactivity inside the patient |
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What does PET stand for? |
Positron emission tomography |
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What are PET scans used for? |
To show soft tissue or organ function and can be used to diagnose medical conditions |
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What can PET scans show in the heart, how and what can that diagnose? |
Areas of damaged tissue by detecting areas of decreased blood flow which can reveal coronary heart disease and damaged or dead tissues caused by heart attacks |
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What can PET scans measure in the brain and what can this diagnose? |
Measure blood flow and activity in the brain and diagnose conditions like epilepsy |
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How can PET scans identify an active cancer tumour? |
By showing metabolic activity in tissue as cancer cells have a much higher metabolic rate than healthy cells as they grow faster |
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What is the patient injected with in PET? What happens to this? |
Injected with a substance that the body uses such as glucose containing a positron emitting radioactive isotope with a short half life so it acts as a tracer Over an hour tracer moves through body to organs |
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What isotopes are often used as tracers in PET scans? |
Carbon 11, Nitrogen 13 Oxygen 15 and Fluorine 18 |
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How do the radioactive isotopes injected show up from PET scans? What pattern does it follow? |
Positrons emitted by radioactive isotopes meet with electrons and annihilate, emitting high energy gamma rays which are detected. Distribution of radioactivity matches metabolic activity as more of the radioactive glucose is used by cells with an increased metabolism doing more work |
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Where are isotopes used in PET scans made? Why? How can hospitals make them? |
Close to where they are to be used as they have a short half life so otherwise the activity would be too low by the time it arrived at the hospital so it would no longer be useful Some hospitals have their own cyclotron to make the isotopes on site |
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What are the risks of PET scans? |
The ionising radiation emitted by the radioactive isotopes can kill a cell or damage it so that it can't divide causing tissue damage Can also change the genetic material in a cell causing it to divide uncontrollably which is cancer |
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How much radiation does a PET scans expose you to? How much is the yearly average background radiation? |
7mSv per scan 2.2mSv of background radiation per year |
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How are the risks of PET scans managed for the patient? |
Risks are balanced... Patients not scanned often and not unless it's necessary as any exposure can increase risk of tissue damage or cancer When having treatment or diagnosis patient should have lowest possible dose and short exposure time to radiation May wear lead apron to protect areas not being treated |
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How do medical personnel limit their exposure to radiation? |
Stand away from source as intensity decreases with distance May work with remote controlled equipment from another room May stand behind a lead screen Their radiation dose is closely monitored |
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How is radiation used internally to treat tumours? |
Radioactive material placed inside the body or near a tumour by injecting or implanting a small amount of a radioactive substance. This gives a high dose to a small part of the body so damage to normal tissue around tumour is limited |
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How is radiation used externally to treat cancer? |
High energy X-rays or gamma rays aimed at the tumour and carefully focused. However there is still some damage to normal cells surrounding tumour |
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Is internal or external cancer treatment quicker? |
Internal- usually up to 6 weeks shorter so fewer hospital visits and patient doesn't have to wait as long to have further treatment such a chemotherapy |
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What is a disadvantage of internal treatment for cancer? |
It may cause a patient to emit radiation after source inserted so they may have to limit their contact with others until it's removed days after whereas with external each session only lasts a few minutes and the patient emits no radiation afterwards |
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Compare the effects of internal and external radiation treatment |
Internal has no effects apart from discomfort of implant External can have short and long term effects |
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Why are different radiation treatments often used? |
For different parts of the body |
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When would it be OK to expose a patient to radiation? |
When the benefits outweigh the risks |
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What can some effects of using radiation to kill cancer be? How long of they last? Why is treatment worth it? |
Skin irritation or hair loss- lasts as long as treatment Can be bowel damage or infertility- presents later Rarely treatment could develop another tumour But without treatment life expectancy is significantly shorter |
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Why may some people refuse radioactive cancer treatment? |
If they think that, due to the side effects, their quality of life will be reduced they may think it is not worth it |
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What is cancer treatment called which doesn't completely cure the patient but reduces suffering near to death? |
Palliative care |
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Why do we not know the long term effects of some medical techniques? |
Because they are fairly new |
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What stages of testing do new techniques go through? |
Tested on lab grown cells, animals then people |
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What are some ethical issues with trials of new medical techniques? |
New techniques may have harmful side effects patients should know before taking part in tests but until tested on humans the effects not known for sure Many patients may want to get onto a medical trial but places are often limited How long after a trial of a technique should the technique be offered to everyone |
