IP Uses of gamma © Oxford University Press 2011 Uses of gamma

IP Uses of gamma © Oxford University Press 2011  Gamma sources are ideal for use in radiotherapy.  Normally ionising radiation is considered to be harmful to healthy cells and can cause cancer.  However, this ionising property can also be used in a positive way to kill cancerous cells.

IP Uses of gamma © Oxford University Press 2011  The Gamma knife is used in hospitals to focus gamma rays onto cancerous cells.  The key thing about the gamma knife is that it can accurately rotate around the patient in order to give a full dose to a specific point in the body while giving low dosages to the rest of the healthy tissues surrounding it.

IP Uses of gamma © Oxford University Press 2011  Gamma sources are also used to sterilise medical equipment.  They are sealed in plastic and enter a machine where they are irradiated by gamma rays.  This kills all the bacteria and living things on them making them sterile for use with patients.  Gamma sources are used because they are highly penetrating (i.e. they will pass through all the equipment without being stopped) therefore killing all the bacteria wherever they are.  Using gamma rays also means that the items themselves do not become radioactive.

IP Uses of gamma © Oxford University Press 2011  Gamma sources are also used as medical tracers.  Weak gamma sources with short half lives are drunk as a fluid or injected.  A special camera is then used to ‘film’ the movement of the fluid in the body. It is routinely used to find leaks in heart valves or blockages in organs.

IP Uses of gamma © Oxford University Press 2011  If the half life was too long the source would continue to emit gamma radiation long after the medical procedure was completed.  A short half life allows the camera to detect the fluid during the procedure but the activity of the source to drop quickly. Explain why a source with a short half life is used in medical tracers.

IP Uses of gamma © Oxford University Press 2011  It would be far too dangerous to use alpha and beta sources because once drunk they would ionise healthy tissue inside the body and cause damage.  They also wouldn’t be able to exit the body in order to be detected because they would be absorbed by the tissue inside the body. Explain why alpha or beta sources are not used as medical tracers.