Dosimetry can be a complex matter. In unraveling its complexities, it is essential to dig deeper into what dosimetry is and its use.
Dosimetry is the process of measuring absorbed dose accurately and systematically as a result of exposure from ionizing radiation.
Furthermore, personal dosimetry forms part of radiation dosimetry. Personal/Personnel dosimetry is the evaluation of doses to individuals who are exposed to radiation related to their work activities. The goal is to detect and measure radiation dose from an ionizing radiation source to determine exposure. Its techniques generally vary depending partly on the location of the source of radiation (external).
Some exposure can be internal (when ingested or taken into the body).
A personal dosimeter refers to a radiation monitoring device that is individually worn by the user. The device is used for determining personal dose equivalent accumulation in the human tissue. It records the dose through the device worn at the surface of the body.
Personal dosimeters come in different types, though the most common are film-containing dosimeters, optically stimulated luminescence (OSL) badge, and thermoluminescent dosimeter (TLD).
The most common types of personal dosimeters are electronic and TLD. Electronic dosimeters are equipped with more sophisticated features such as continual monitoring, threshold presetting, alarms and notifications, and a live readout of dose accumulated.
On the other hand, TLD measures the intensity of light emitted in the detector when heat is applied. Such intensity is dependent on the extent of radiation exposure. The main advantage of TLD is its ability to measure and record radiation dose passively until heat is applied.
Other types of personal dosimeters are film badges, quartz fiber, and Geiger tubes.
Exposure to ionizing radiation penetrates the living cell, thereby causing damages to the body. Accumulated radiation doses are cumulative, wherein the extent of exposure leads to greater damages. Wearing a personal dosimeter allows the individual to keep exposure at a safe level.
Please be reminded that personal dosimeters cannot be considered absolute instruments. Instead, these are referent instruments that should be calibrated periodically.
Personal dosimeters are usually worn outside the clothes. However, if using a whole-body dosimeter, it must be worn on the chest and torso. As such, one or more dosimeters can be worn simultaneously in various parts of the body. The placement of the dosimeter is crucial—it should be worn on body parts where the most exposure is expected.
The dosimeter must be facing the radiation dose source.
A personal dosimeter records dose exposure levels in the most accurate way compared with other dosimeters. This is more so if the dosimeter is worn where it is intended properly.
Some dosimeters are highly portable devices. This allows the user to know his or her exposure through registered readings while still in the facility where radiation exposure is relatively apparent.
One limitation of personal dosimeters is detecting, measuring, and recording accumulated exposures. And so, it can only measure external exposure, not internal exposure, which is a different thing. Some dosimeters have no real-time display nor an alarm to tell the wearer that he or she is entering a hot zone.
As such, this device cannot help the user avoid exposure prospectively. With this, personal dosimeters must be read regularly to determine exposure.
This leads us to the next question, whereby personal dosimeters must be read on a regular basis. It can be bi-monthly, monthly, or quarterly. However, readings should not exceed the 12-month period. Otherwise, readings may no longer be as accurate as when dosimeters are read every other month.
Anyone who is expected to get exposed to radiation doses may use personal dosimeters. These are the radiographers, X-ray operators or technicians, nuclear plant workers, dentists, etc. Even pregnant women working in these jobs are encouraged to wear personal dosimeters. They are generally referred to as radiation workers and the environment they work in is known as a radiation facility or hot zone.
In wearing the device, the facility may be able to know the radiation exposure of the people and how it can best address safety concerns at the facility level.
The cost of the personal dosimeter depends on its type and technology. A handheld or worn device costs starting from Php15,000 (or $150). A charger is sold separately for additional Php5,000 (or $50).
In the Philippines, the use of personal dosimeters in facilities where radiation exposure is inevitable is highly encouraged. Nonetheless, the businesses operating in these facilities are required by the law to ensure occupational health and safety. Personal dose monitoring is covered by these laws.