Optically Stimulated Luminescence (OSL) dosimeter is the most common type of personnel dosimeter used in the monitoring of occupational radiation exposure in today's diagnostic radiology. The most commonly used solid state detectors are thermoluminescent dosimeters (TLD) and semiconductor junction detectors. Both have an atomic composition that differs from water and tissue and have a density that is greater than that of water, causing energy dependence compared to the dose absorbed in water and disturbing the flow of particles in a water ghost. Thermoluminescent dosimeters are convenient due to their small volume, lack of associated voltage, and availability.
However, they need individual calibration, are read long after irradiation and need careful conditioning. They are also energy dependent, dose dependent, and temperature dependent, and can be damaged after a cumulative dose of approximately 100 Gy. Film badges are another type of personal radiation monitoring device. They consist of a piece of film that is sensitive to radiation enclosed in a wrapper that is impenetrable to light.
When developed, the film reveals the radiation exposure of the person wearing the badge. Direct-read dosimeters (DRD) and TLD films or plates are often used together. The reading of the film or TLD is usually considered the recording dose, but if a TLD film or board is exposed when not in use, it may be appropriate to use a DRD reading. Insignia dosimeters measure the radiation dose received by the person using it.
OSL dosimeters are not affected by varying external temperatures, making them more reliable than TLD dosimeters for reporting small doses of one thousandth of rem, known as millirem doses (mrem). TLD dosimeter badges are essential for professionals operating x-ray systems, x-ray fluorescence equipment, and x-ray diffraction equipment. They help keep the effective dose of radiation to a minimum while also notifying the person when to leave a radiation site. Pocket dosimeters consist of a quartz fiber, a scale, a lens for observing the movement of the fiber through the scale, and an ionization chamber.
Transmission dosimeters use plastic or glass scintillators as well as a semiconductor or Geiger-Müller tube (G-M tube) that uses a gaseous mixture to detect radiation. If a person's pocket camera is found to be out of scale or if their electronic personal dosimeter reads more than 2 millisieverts (200 millirems), and the possibility of radiation exposure as a cause cannot be ruled out, their personal dosimeter should be sent for processing and evaluation within 24 hours. TLD dosimeter wristbands are commonly used in mail processing industry, medical environments, and industrial facilities. Licensees may not allow any person to act as a radiographer or assistant radiographer unless they carry direct-reading dosimeters, operational alarm frequency meters, and personnel dosimeters on their trunk at all times during radiographic operations.
Pocket dosimeters should range from zero to 2 millisieverts (200 millirems) and must be recharged at the start of each shift due to their higher sensitivity compared to TLD dosimeters.
