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50 Cards in this Set

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What is a positron?

Positively charged Beta radiation

What is the positron's antiparticle?

The electron (same mass but charge of -1 not +1)

What happens when a positron and electron collide?

They are obliterated in annihilation

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

How penetrating is neutron radiation?

More than alpha and beta and sometimes more than gamma

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

What things can make a nucleus unstable?

Too many neutrons


Too few neutrons


Too many protons and neutrons


Too much energy

How is the stability curve plotted?

Number of neutrons plotted against number of protons for stable atoms to give curve of stability

If an atom was not on the line of stability what would it be?

Unstable

If an atom is above the curve why is it not stable? Below?

Too many neutrons


Below too many protons

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

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

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

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

What are protons and neutrons made up of?

Quarks

What are the charges and masses of up and down quarks?

Up +2/3 and 1/3


Down -1/3 and 1/3

What are the quark configurations of protons and neutrons?

Proton uud


Neutron udd

What happens when quarks change?

They produce electrons or positrons

How would a neutron change to a proton in an unstable atom?

By changing a quark


Down quark changes to up quark


udd -> uud

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

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

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

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

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

What does PET stand for?

Positron emission tomography

What are PET scans used for?

To show soft tissue or organ function and can be used to diagnose medical conditions

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

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



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


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

What isotopes are often used as tracers in PET scans?

Carbon 11, Nitrogen 13 Oxygen 15 and Fluorine 18

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

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

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

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

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



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



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

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

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

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

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

Why are different radiation treatments often used?

For different parts of the body

When would it be OK to expose a patient to radiation?

When the benefits outweigh the risks

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

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

What is cancer treatment called which doesn't completely cure the patient but reduces suffering near to death?

Palliative care

Why do we not know the long term effects of some medical techniques?

Because they are fairly new

What stages of testing do new techniques go through?

Tested on lab grown cells, animals then people

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