Treatment – Revision Pack (P4)
Using Radiation:
Radiation emitted from the nucleus of an unstable atom can be alpha (α), beta (β)
or gamma (µ).
Alpha radiation is absorbed by the skin, so is NOT useful for diagnosis or treatment.
Beta radiation passes through the skin but not bone. Its medical uses are limited
because of this; they are for example used to treat the eyes.
Gamma radiation is very penetrating and is widely used in medicine. Cobalt-60 is a
gamma-emitting radioactive material that is widely used to treat cancers.
When nuclear radiation passes through a material it causes ionisation. Ionising
radiation damages living cells, increasing the risk of cancer. Alpha radiation is the
most ionising and gamma radiation is the least ionising.
Cancer cells can be killed using radiation. The affected area is exposed to large
amounts of radiation in a process called radiotherapy.
NOTE – materials can be made radioactive in a nuclear reactor whereby their nuclei
absorb extra neutrons.
X-rays and Gamma rays:
When X-rays pass through the body, the tissues absorb some of the ionising radiation.
The amount absorbed is dependent on the density of the absorbing material.
Gamma and X-rays have similar (short) wavelengths, but are made in different ways.
X-rays are made in the following way:
STEP 1 – high-speed electrons are fired (from
the cathode) at a metal target (located at the
anode)
STEP 2 – most of the kinetic energy is lost as
heat, but some is transferred to x-rays
STEP 3 – the x-rays then exit via a glass window
Through using an x-ray machine, you can
control the production and energy of the xrays. With gamma rays you CANNOT control or
change the gamma radiation emitted from a
particular source.
When the nucleus of an atom of a radioactive substance decays, it emits an alpha
or beta particle and loses any surplus energy by emitting gamma rays.
Treatment – Revision Pack (P4)
T racers:
Some radioactive tracers are used to investigate inside a patient’s body without the
use of surgery.
For example technetium-99m is used as a medical tracer. It only emits gamma
radiation.
Iodine-123 is also used as a medical tracer.
It emits gamma rays and is used to
investigate the thyroid gland (see left).
The radioactive tracer is mixed with food
or drink and consumed or injected into the
body.
Its progress through the body can be
monitored by using a detector such as a
gamma camera connected to a
computer.
This avoids using surgery to investigate.
Treating Cancer:
Source of
radiation
Source of
radiation
A radioisotope is used to destroy a tumour in the
body.
STEP 1 – three sources of radiation, each
providing a 3rd of the required dose, are
arranged around the patient with the tumour at
the centre.
Source of
radiation
STEP 2 – the healthy tissue only receives a third of
the dose so the damage to healthy tissue is
limited.
OR - each radiation source slowly rotates around the patient. The tumour will receive
constant radiation BUT healthy tissue receives only small inconsistent doses of radiation,
limiting damage to healthy tissue.
Treatment – Revision Pack (P4)
Past Papers:
PPQ(1):
Treatment – Revision Pack (P4)
PPQ(2):
Treatment – Revision Pack (P4)
Mark Schemes:
PPQ(1):
PPQ(2):