The OSL dosimetry (Optically Stimulated Luminescence) is a method that has established itself in the whole-body dosimetry. As can be deduced, this method is based on optically stimulated luminescence. The OSL dosimeter provides a very high degree of sensitivity by giving an accurate reading as low as 1 mrem for x-ray and gamma ray photons with energies ranging from 5 keV to greater than 40 MeV. OSL dosimeters are designed to provide X, gamma, beta and neutron radiation monitoring using OSL technology. OSL dosimeters are applicable to situations where real-time information is not needed, but precise accumulated dose monitoring records are desired for comparison to field measurements or for assessing the potential for long term health effects. In diagnostic imaging the increased sensitivity of the OSL dosimeter makes it ideal for monitoring employees working in low-radiation environments and for pregnant workers. OSL dosimeters offer advantages that include the ability to be re-read and a high sensitivity (low minimum measurable dose), and they have become popular because of these favourable properties.
OSL materials (e.g. beryllium oxide ceramic) contain defects in their crystal structure that trap electrons released by exposure to radiation. In TLDs, the trapped electrons are subsequently freed by stimulation with heat, while OSL uses stimulation with light. After stimulation by light, the detector releases the stored energy in the form of light, i.e., it is stimulated to emit light. The light output measured with photomultipliers is a measure unit for the dose. In comparison with TLDs, their major difference is that luminescence is produced by a light beam, rather than by heat.
The OSL dosimeter must be worn on a position of the body representative of its exposure, typically between the waist and the neck, on the front of the torso, facing the radioactive source. Dosimeters are usually worn on the outside of clothing, around the chest or torso to represent dose to the “whole body”. If a person uses a lead apron, the dosimeter must be worn under the lead apron. Specialized equipment (OSL Reader) is used for this readout, either by the user with field-portable or lab-based equipment, or by a dosimetry processing laboratory. A commercial dosimetry service can be contracted to supply dosimeters on a regular basis, read out returned dosimeters, and provide dose tracking and record keeping. TLDs and OSL dosimeters are offered in either a clip-on brooch format or identification card style.
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