Dosimetry and Medical Radiation Physics Section

From the IAEA Division of Human Health

What is medical physics?

It is the discipline that applies physics to the needs of clinical medicine, overseeing clinical applications of radiation and developing the innovative medical technologies of tomorrow. Medical physicists working in the clinical environment play a key role in ensuring that the radiation delivered to the patient for diagnosis or treatment purposes is carried out accurately and in a way that makes it effective, while maximising the patient’s safety.

What is dosimetry?

Whether weighing out apples at the supermarket or medication at the drug store, the decisions we make, and the consequences thereof, depend on the amount we buy - or rather the measured weight - of the product. But, what if the thing we are measuring is completely invisible? Dosimetry is the measuring procedure applied to ionizing radiation which is used, for example, to treat cancer by destroying harmful cells; ionizing radiation is invisible and undetectable to the human senses, yet it has to be precisely measured in order to be effectively delivered.

Why is dosimetry so important?

Measurements are part of our everyday life, but while an error of a few percent may not be of concern when weighing fruits, when it comes to medical treatment it is necessary to be very precise. Ionizing radiation, which can be used to treat cancer, requires the utmost care in ensuring it is accurately measured, since too little or too much radiation can be harmful to the patient. The work of the Dosimetry and Radiation Physics (DMRP) Section aims at achieving good quality and effectiveness of diagnostic and therapeutic procedures involving ionizing radiation, ensuring that patients are only receiving the needed radiation and are protected as much as possible from the radiation’s side effects. The harmonization and standardization of best practices ensure that patients receive the best care possible worldwide.

What is the role of the IAEA in medical physics?

Imaging and treatment modalities require accurate dosimetry and complex quality assurance (QA) procedures. In view of the increasing complexity of the technology and combined imaging and treatment modalities, the need for QA is expected to increase to ensure appropriate clinical outcomes and to reduce the likelihood of errors, accidents and misdiagnoses. The IAEA develops internationally harmonized dosimetry and QA protocols and provides guidance to Member States for their implementation.

What is the role of the IAEA in dosimetry?

The Dosimetry Laboratory plays a key role in establishing and disseminating best practices in the safe and effective use of radiation for the diagnosis and treatment of cancer through its quality assurance services related to medical physics and dosimetry, for which demand is steadily increasing. The IAEA supports Member States by:

  1. Setting up national dosimetry and calibration laboratories, linked to the international system of measurements, through the IAEA/WHO Network of Secondary Standards Dosimetry Laboratories;
  2. Providing essential dosimetry services to countries that have no national dosimetry infrastructure;
  3. Supporting education and training of specialists working in dosimetry laboratories and medical physicists working in hospitals to ensure consistency of the dosimetry chain at national level.

Calibration of ionisation chamber for use in radiotherapy. (Photo: E. Izewski, IAEA)

IAEA publications, guidelines for dosimetry procedures

Set-up for a thermoluminescent dosimeter (TLD) dose measurement. (Photo from IAEA TLD irradiation video tutorial, E. Izewski, IAEA)

Solid water phantom used for dosimetry audit. (Photo: E. Izewski, IAEA)

Calibration of detector used in diagnostic radiology