Radiation Protection Today - Spring 2022 - Page 13

or the source may be attached to a cable which can be ' wound out ', allowing it to be positioned inside an item to be imaged .

Typical Calibration Source
In the past , heavily shielded high activity sources , typically of Cobalt-60 , were also used in hospitals for the treatment of cancer , but this is now less common with the advent of linear accelerator treatment facilities .
Design of an encapsulated sealed source and a typical example
sources or ' seeds ' of Iodine-125 ( up to tens of MBq ) into the body to treat prostate and other cancers . High Activity Sealed Sources ( HASS ) with typical activities up to hundreds of GBq in the form of ' seeds ' of Iridium-192 or Cobalt-60 are used for higher dose brachytherapy . These sources are shielded within the therapy machine when not in use , and are ' wound out ' and into the patient to irradiate the tumour for up to 10-15 minutes during a treatment via a delivery catheter / applicator .
HASS with typical activites in the TBq range are widely used in industrial radiography for the imaging of metal castings or welds to detect defects . These sources are generally portable , and consist of a sealed source ( usually Cobalt-60 or Iridium-192 ) inside a heavily shielded container . The container either has a ' window ' which can be opened to expose the source and emit a beam of radiation , A typical industrial radiography source
Radiation Protection Today Summer 2022
Examples of iodine brachytherapy seeds ( left ) and radiation teletherapy using a sealed source ( right )
Encapsulated sealed sources may be contained in radiation devices or nuclear guages which are used for various purposes throughout industry , including thickness , density , moisture and level measurement . In these cases , the degree of absorption of gamma or beta radiation provides information on the properties of the material being monitored . Similar types of sealed sources with higher activities are also used for food irradiation , calibration and sterilisation . The radiation device in all these cases usually incorporates shielding to reduce the exposure of nearby personnel .
Level or Flow Measurement Gauges
Thickness gauges typically using Krypton-85 13