Medical Uses of Radiation
Medical Tracers
- A tracer is a radioactive isotope that can be used to track the movement of substances, like blood, around the body
- Gamma emitters are usually used for this purpose
- Gamma rays are highly penetrating and so will be able to pass through the body and be detected outside the body
- This allows an internal image of the body to be created
Iodine-131 is an example of a radioactive tracer
- Since gamma rays are less ionising than some other forms of radiation, the harm caused to the patient is also minimised
- As well as choosing a gamma emitter:
- The amount of isotope used is kept to a minimum to reduce people’s exposure to radiation
- Isotopes are chosen that have short half-lives of around a few hours: Long enough to carry out the procedure, but not so long that they cause long term harm
Radiotherapy
- Radiotherapy is the name given to the treatment of cancer using radiation
- Although radiation can cause cancer, it is also highly effective at treating it
- Radiation can kill living cells
- Some cells, such as bacteria and cancer cells, are more susceptible to radiation than others
- During external radiotherapy, beams of gamma rays are directed at the cancerous tumour
- The machine rotates to target the tumour from different angles
- This minimises the exposure of healthy tissue to the gamma rays and minimises damage to healthy cells
During radiotherapy, the beams are moved around to minimise harm to healthy tissue whilst still being aimed at the tumour
- During internal radiotherapy, small pellets of radioactive materials can also be inserted into a tumour exposing it directly to radiation
Sterilising Medical Equipment
- Gamma radiation is widely used to sterilise medical equipment
- Gamma is most suited to this because:
- It is the most penetrating out of all the types of radiation
- It is penetrating enough to irradiate all sides of the instruments
- Instruments can be sterilised without removing the packaging
Worked example
A new medical tracer is required for investigating the absorption of a particular substance found in blood around the body.Which of the different isotopes in the table would be most suitable?
ANSWER: C
- A suitable medical tracer must:
- Be able to penetrate out of the body
- Have a long enough half-life to move around the body before it decays away
- Have a short enough half-life that it won’t remain in the body at dangerous levels for too long
- The answer is not A because alpha radiation cannot penetrate out of the body
- The answer is not B because the half-life is too short
- The answer is not D because the half-life is too long
- A suitable medical tracer must: