TELEISOTOPE UNIT

Typical Number in Hospital: 1

Cost Bands: 6

References: 3

High-activity radionuclides such as caesium-137 and cobalt-60 can be used to provide high-energy gamma-ray beams for the treatment of tumours. A teleisotope unit delivers the beam from outside the body, passing through the skin to the site to be treated.

Cobalt-60 is the most commonly used gamma-ray source for this form of teletherapy since it is highly active, and has a long half-life (5.5 years) and produces radiation at 1.17 and 1.33 MeV. The cobalt source contains a number of cobalt-60 discs in a double stainless steel container with screwed and brazed lids. The source is contained within a treatment head which may weigh one ton. The head may include all of the shielding, and the mechanism for rotating the source or collimator to expose or hide the source itself.

The radiation is delivered to the patient via a set of collimators to contain the beam to the correct shape required for the treatment. The head itself may also be manipulated to deliver the beam from a number of different angles so that maximum irradiation occurs at the centre of this rotation, other parts of the body receiving proportionately less.

Such machines are found in the radiotherapy department.