Kerma

Kerma city

Beelden van Kerma

ReisnerKerma

Western Deffufa - Kerma

Model Kerma capital

Kerma is a term used in radiation protection and medical physics to describe the kinetic energy released per unit mass in a material by ionizing radiation. The term is an acronym for "Kinetic Energy Released in MAterial." Kerma is a crucial concept in the field of radiology and nuclear medicine, as it helps quantify the energy transferred from radiation to matter, excluding any rest mass energy from electron-positron annihilation. Understanding kerma is essential for assessing the potential biological effects of radiation and for ensuring the safety and efficacy of radiological procedures.

Definition

Kerma is defined as the initial kinetic energy transferred from photons to charged particles (such as electrons) per unit mass of a material. Mathematically, kerma (K) can be expressed as:

\[ K = \frac{dE_{tr}}{dm} \]

where \(dE_{tr}\) is the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing particles in a material of infinitesimal mass \(dm\).

Types of Kerma

There are two primary types of kerma: air kerma and absorbed dose.

• Air Kerma is the kerma calculated for air and is often used as a reference or calibration standard because it can be measured directly and accurately. It is crucial for the calibration of radiation dosimeters and in defining radiation exposure and protection guidelines.
• Absorbed Dose is related to kerma but takes into account the energy actually absorbed by the material, including any energy lost to radiation. While kerma is a measure of the initial kinetic energy transferred, absorbed dose is a measure of the energy deposited in the material.

Importance in Radiation Protection

Kerma plays a vital role in radiation protection and dosimetry. It provides a measure of the potential dose a material or tissue could receive from an ionizing radiation field, which is essential for assessing radiation exposure risks. In medical settings, accurate kerma measurements ensure that the benefits of radiological procedures outweigh the potential risks associated with radiation exposure.

Measurement

Kerma can be measured using a variety of dosimeters, including ionization chambers, which are commonly used due to their accuracy and reliability. These devices measure the ionization of air, which can be directly related to air kerma, and by extension, to the kerma in other materials using conversion factors.

Applications in Medical Physics

In medical physics, kerma is used to calibrate radiation sources and to ensure that the delivered dose in treatments such as radiotherapy is accurate and effective. It is also used in diagnostic radiology to optimize imaging techniques, minimizing the patient's exposure to radiation while obtaining high-quality images.

Conclusion

Kerma is a fundamental concept in the fields of radiation protection, medical physics, and radiology, providing a measure of the energy transferred from radiation to matter. Understanding and accurately measuring kerma is essential for ensuring the safety and efficacy of radiological procedures, as well as for protecting individuals from the potential risks associated with radiation exposure.