Internal dosimetry relies on a variety of monitoring, bioassay or radiological imaging techniques, while external dosimetry is based on measurements taken with a dosimeter or derived from measurements of other radiation protection instruments. The personal dosimeter for ionizing radiation is fundamental in the disciplines of radiation dosimetry and radiation health physics and is mainly used to estimate the radiation dose deposited on a wearer of the device. Internal dosimetry is used to assess the committed dose due to the ingestion of radionuclides in the human body. For the protection of persons working with ionizing radiation, the regulation sets dose limits in the workplace (WAC 246-221-010). The limit for X-ray operators is 5 rem/year (or 5000 millirem/year). The limit is expressed in Total Effective Dose Equivalent (TEDE), which is a scientific method for determining how doses for one part of the body affect the person as a whole. Limits are also set for certain organs: 15 rem/year for the eyes and 50 rem/year for the extremities, including fingers, feet or skin. The best way to determine the degree of exposure a person receives over a long period of time is to use personal dosimetry. Four types of workers are required to use personal dosimetry.
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and evaluation of the dose of ionizing radiation absorbed by an object, usually the human body. This applies both indoors, through ingestion or inhalation of radioactive substances, and outdoors through irradiation from radiation sources. Medical dosimetry is the calculation of the absorbed dose and the optimization of dose administration in radiotherapy. It is often performed by an occupational health physicist with specialized training in the field. In order to plan the implementation of radiation therapy, radiation produced by sources is usually characterized by deep percentage dose curves and dose profiles measured by a medical physicist. In radiation therapy, three-dimensional dose distributions are often evaluated using a technique known as monetary osimetry. [2] In order to account for stochastic health risk, calculations are made to convert the absorbed physical dose into equivalent and effective doses, the details of which depend on the type of radiation and the biological context. For radiation protection and dosimetry evaluation applications, the ICRP and the International Commission on Radiation Units and Measurements (ICRU) have published recommendations and data that are used to calculate them. In some circumstances, a dose may be derived from readings taken with stationary instruments in an area where the person has worked. This would generally only be used if no personal dosimetry has been issued or if a personal dosimeter has been damaged or lost.
Such calculations would give a pessimistic view of the probable dose received. More precisely, radiation dosimetry is the calculation of the absorbed dose to tissues resulting from exposure to ionizing radiation. The dose is expressed in units of gray (Gy) for mass and the equivalent dose in units of sievert (Sv) for biological tissue, where 1 Gy or 1 Sv equals 1 joule per kilogram. Traditional units are also still predominant, where dose is often expressed in wheels and equivalent dose in REMS. By definition 1 Gy = 100 rad and 1 Sv = 100 rems. Workers who may be exposed to radiation wear personal dosimeters. These dosimeters measure the dose according to various measurement systems. The average background dose for a human being is about 350 milli-rem per year, which results mainly from cosmic rays and natural isotopes in the Earth. Other important areas are medical dosimetry, which monitors the required absorbed therapeutic dose and each secondary absorbed dose, and environmental dosimetry, such as radon monitoring in buildings.
The International Committee on Radiological Protection (ICRP) guidelines state that if a personal dosimeter is worn at a location on the body representative of its exposure, assuming whole-body exposure, the personal equivalent dose value Hp(10) is sufficient to estimate an effective dose value suitable for radiation protection. [1] These devices are called “legal dosimeters” if they are approved to record personal dose for regulatory purposes. In the case of uneven irradiation, these personal dosimeters may not be representative of certain areas of the body where additional dosimeters are used in the area in question. Dental facilities are generally not required to provide dosimeters to personnel because exposures are very low and beam sizes are very small. Many doctors` offices and chiropractors also do not need to perform dosimetry, usually because the X-ray operator must stand in a lead-shielded booth. Although not mandatory, it may be a good idea to use a film or TLD identification service as a reference for permanent documentation. The service can be used for short periods (6 to 12 months) to check and record the working environment at low (or zero). However, you must keep the records indefinitely (WAC 246-221-090). Records of legal dosimetry results are usually kept for some time, depending on the legal requirements of the country in which they are used. The damage caused to the human body by ionizing radiation is cumulative and refers to the total dose received, for which the SI unit is the sievert. Radiographers, nuclear power plant workers, physicians using radiation therapy, dangerous goods workers and others handling radionuclides are often required to wear dosimeters in order to record occupational exposure.
These devices are called “legal dosimeters” if they are approved to record personal dose for regulatory purposes. There are several ways to measure absorbed doses of ionizing radiation. People who come into professional contact with radioactive substances or who may be exposed to radiation regularly carry personal dosimeters with them. These are specially designed to record and display the dose received. Traditionally, these were medallions attached to the outer clothing of the person being watched and containing photographic film known as film badge dosimeters. These have been largely replaced by other devices such as the TLD badge, which uses thermoluminescent dosimetry or optically stimulated luminescence (OSL) badges. The NPL uses a graphite calorimeter for absolute photon dosimetry. Graphite is used instead of water because its specific heat capacity is one-sixth that of water, and therefore the temperature rise of graphite is 6 times higher than the equivalent in water and measurements are more accurate. There are significant problems in isolating graphite from the environment to measure minute changes in temperature. A lethal dose of radiation to a human is about 10-20 Gy. It is 10-20 joules per kilogram.
A piece of graphite of 1 cm3 weighing 2 grams would therefore absorb about 20-40 mJ. With a specific heat capacity of approximately 700 J·kg−1· K−1, this corresponds to a temperature increase of only 20 mK. The absorbed dose determines the extent to which tumours and normal tissues are affected by radiation. The higher the dose absorbed for tumors, the more cells are killed by radiation and the greater the likelihood of recovery. However, the higher the dose absorbed for normal tissue, the more likely and serious the adverse toxic side effects of radiation therapy can be. An important advantage of radiopharmaceutical therapy is its ability to irradiate tumors throughout the body and treat them effectively; At the same time, some irradiation of normal organs is inevitable. Therefore, the role of radiation dosimetry in targeted radionuclide therapy is to determine, specifically for each patient, the amount of radiopharmaceutical administered that most effectively treats the patient`s disease while avoiding absorbed doses that damage normal tissue. Individualized radiation dosimetry is essential for planning the most effective and safe targeted radionuclide treatment for each patient. There are three types of personal dosimeters: film badges, the new Luxel technology and TLDs (thermoluminescence dosimeters). Each can be useful for different needs. These are used and analyzed monthly or quarterly (quarterly tends to be cheaper). If you are using a quarterly monitoring period, we recommend that you use TLDs or Luxel type TLDs and not movies from the service provider you are using.
Issues related to the choice of dosimetry for radiation monitoring include: Environmental dosimetry is used when it is likely that the environment will produce a significant dose of radiation. Radon monitoring is one example.