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67 Cards in this Set
- Front
- Back
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Describe alpha |
a helium nucleus which is slow and heavy, strongly ionising and will be stopped by paper or skin |
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describe beta |
a electron, which is light and fast and moderately ionising - stopped by thin metal |
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Describe gamma |
A high energy wave of electromagnetic radiation, with no mass but is very fast and weakly ionising. Stopped by thick lead or concrete |
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Describe a postiron |
a antiparticle of an electron, so they are just like electrons (light, fast, moderately iosins and stopped by thin metal)- same relative mass but instead they are positively charged (+1) |
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What happens when positrons collide with electrons |
annihilation |
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What is another type of radiation? |
Neutron radiation |
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How is neutrons similar to other types of radiation such as beta, alpha and gamma? |
Unlike them it is not directly ionising. It can be absorbed by the nucleus of a medium they are passing through, causing the nucleus to be radioactive meaning it will emit ionsing radiation = Indirectly ionsing |
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When are neutrons absorbed the best? |
By light nuclei, such as hydrogen |
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What is included in neutron radiation shielding? |
Hydrogen rich materials such as water, polythene and concrete as neutrons are absorbed best by light nuclei. As neutron absorption tends to emit gamma thick lead is also added |
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4 ways a nucleus can be unstable |
too many neutrons, too few neutrons, too much energy , too many neutrons and protons |
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What will you get on a graph for stable isotopes comparing the number of neutrons to protons? |
A curve of stabability |
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When will a isotope be unstable? |
If it doesn't lie on the curve |
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An isotope which lies above the curve.. |
too many neutrons to be stable |
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an isotope which lies below the curve |
too few neutrons to be stable |
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Beta minus decay |
emission of an electron from the nucleus, happens in neutron rich isotopes. When a nucleus ejects beta radiation- one of the neutrons in the nucleus is changed into a proton |
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What happens to the atomic numer and (nucleon) mass number in beta minus |
atomic number increases by one but the mass number stays the same |
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Beta plus |
emission of a positron from the nucleus, happens when there are to few neutrons |
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what happens to the atomic number and mass number in beta plus? |
proton number decreases by 1 and the nucleon number remains the same |
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alpha decay |
happens in heavy nuclei, ones with more than 82 protons such as uranium and radium. Nuclei are too big to be stable |
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what happens to the atomic number and mass number in alpha decay |
Proton number decreases by 2 and the mass number decreases by 4 |
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When and why does Gamma radiation occur? |
after alpha or beta decay as the nucleus often has excess energy which it losses by emitting gamma rays. Gamma always goes with alpha and beta never get it on its own |
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What happens to the proton and neutron number of a nuclei when gamma is emitted? |
there will be no change in the proton and nucleon number |
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What are protons made by? |
Each by 3 even small particles called quarks |
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What happens when quarks combine to make protons and neutrons |
The charges of the quarks ass together to make the overall relative charges of the protons and neutrons |
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What quarks make up a proton? |
2 up quarks and 1 down quark |
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What quarks make uo a neutron? |
1 up quark and 2 down quark |
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What causes a nucleus to be unstable, how do they become more stable? |
The number of protons and neutrons in a nucleus can make it unstable. It can become more stable by a neutron being converted to a proton or a proton to a neutron |
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What is the rule of quarks changing? |
Overall charge before and after must be equal |
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when a neutron turns into a proton |
1 down quark turns into a up quark. nucleus has to produce a negatively chatged particle to, so the overall charge remains at 0. Particle produced is a electron = Beta minus |
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When a proton changes into a neutron |
Up quark into a down quark. Positive charge is needed to keep the overall charge at +1. Nucleus produces and throws out a positron = B+ decay |
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How do radioactive isotopes work as tracers? |
Tracer is injected or swallowed. External detector follows its progress as it moves round the body - computer uses these readings to create an image which shows where the stronges readings of radation are coming from |
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Example of radio isotopes used as a tracer |
iodine-131 which is absorbed by the thyroid gland. Gives out radiation which can be detected to tell you whether the thyroid gland is taking in iodine as it should |
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What isotopes should be used as tracer? |
Only ones which emit beta or gamma as they can pass out the body. They also have short half lives to reduce the amount of radioactivity inside the patient |
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Positron emission tomography |
PET Scanning, used to show tissue or organ function and can be used to diagnose medical conditions |
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What 3 things can PET scanning identify? |
Damaged tissue and active cancer tumours. As well as blood flow and activity in the brain which will help diagnose such illnesses as epilepsy |
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How do PET scans show areas of damaged tissue? What can this reveal? |
By detecting areas of decreases blood flow. Reveal coronary artery disease and damaged or dead heart muscle from heart attacks |
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How can PET scan identify active cancer tumours? |
By showing metabollic tissue. Cancer cells have a higher metabolism than healthy cells because they are growing like mad |
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How do PET scans work? |
Inject substance used by body containing positron emitting radioactive isotope= tracer. Annihilation= gamma rays. Radioactivity distribution matches metabollic activity. |
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Why does the distribution of radioactivity match metabollic activity? |
as more of the radioactive substance e.g. glucose in patient is used up by cells with a increased metabolism |
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How and why is it important for isotopes for PET scanning to be mad close to where they will be used? |
As the isotopes need short half lives. Some isotopes have their own cyclotrons to make isotopes on site. |
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What would be the problem if the isotopes were not made on site |
They may no longer be as useful as there activity may have dropped when being trasported over long distances |
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What can ionsiation do to cells? |
Compleley kill or damage them so they cannot divide |
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What can radiation do to cells? |
alter genetic material, causing mutations in a cell. It can make the cell divide uncontrollably - cancer |
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Why is it important to limit exposure to radiation? |
Radiation is dangerous it can alter genetic material and cause cancer |
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How much radation is used per PET scan? |
7 millisiverts (mSv) |
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How muchh radation radaiton is there in background radation per year just from living in the UK? |
2.2 millisiverts (mSv) |
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What are the rules for treatments and diagnostic methods involving radiation? |
Patients should be given the lowest possible doses of radation and they should also have a short exposure time. Wear lead shielding to protect areas not being treated |
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How do medical personnel limit there exposure to radiation? |
Stand far away from a source or remotely control equipment as radiation intensity decreases with distance. Stand behind lead screens or wear protective lead lined clothinG as intensity depends on the material it is passing through. Radiation dose closely monitored |
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what is internal radiation therapy? |
when a radiaoctive material is placed inside the body into or near a tumour. Done by injecting or implanting. |
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advantage of internal radiation therapy? |
High does of radiation to a small part of the body so damage to normal tissue surrounding the tissue is limited |
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How can tumours be treated externally? |
Using high energy x-rays or gamma rays aimed at tumours . Radiation is carefully aimed at the tumour but some damage is still done to the surrounding healthy cells |
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Comparing internal to external.. time |
Whole treatmet for internal is normally shoter than external sometimes by 6 weeks. Reducing the number of visits to hospital as well as the time they have to wait to undergo any further planned treatment. |
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Comparing internal and external; after results |
Internal may cause the patient to emit radiation after a source is inserted- so they may have to limit contact with people until it is removed (several days). External- each session last a few minutes and the patient doesnt emit radiation after |
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Comparing internal and external: side effects |
internal genrally no side effects however the implant may cause some discomfort. But external have short and long term effects |
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are external and internal treatments often used together/ |
Some uses overlap but normally used for different body parts |
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Radiation is both useful and dnagerous what do we have to consider when using it ? |
whether the benefit of using it for treatment outweigh the associated risk to the patient invilved |
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What leads to side effects? |
Using radation to kill off cancerous cells will always cause some damge to normal cells. |
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Examples of side effect |
raditotherapy can cause hair loss, sickness and skin irritation. These fairly minor sie effects generally only last as long as the treatment |
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What more seriuos side effects are there? |
Bowel damage and infertility which may appear months or years after radiotherapy treatment has ended and could effect someones life significantly |
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What are the arguements against using radation? |
If someones quality of life could be seriously reduced after treatment then it may not be worth undegoing it in the 1st place. Some may refuse treatment due to the risk of side effects. |
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What may happen in some rare cases? |
Patient may develop a second cancer caused by radiation used to treat the first cancer. |
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Arguement for radiation therapy? |
Without the first treatment the persons life expectance would be dramatically shorter |
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What is pallitative care |
treatmetn which reduces suffering without curing a illness |
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what is the disadvantage of radioactive mecical treatments? |
some are fairly new in the medical worl meaning we do not fully understand the long term benefits and side effects |
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How are new techniques normally tested? |
First on cells grown in the lab, then animals. If they are tested on animal and seem okay they will then be tested on people |
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Ethical arguements for testing on people |
New technique may have possible side effects which the patients should be aware of before agreeing to take part in the medical tests. But doctors don't know for sure what side effects could be |
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Further ethical arguements |
Lots of ill patients might want to be on a medical trial but places are limited. How long should it be before a technique which works should be offered to all? |
