## 1. What is Radiation Dosimetry?

Definition: Radiation dosimetry is the science of measuring and calculating the amount of radiation exposure that a person or object has received. This field plays a vital role in a wide range of industries, including nuclear power, medical imaging, and radiation therapy. In this article, we will explore the basics of radiation dosimetry, including the units used to measure radiation exposure, the types of radiation and their properties, and the methods used to measure radiation.

Radiation dosimetry is the branch of science that deals with the measurement and calculation of the amount of radiation exposure received by an object or person. Additionally, radiation exposure can occur naturally. For example, in the case of cosmic radiation from outer space or from radioactive elements in the soil. It can also be artificial, as in the case of medical imaging or nuclear power generation.

Moreover, radiation can have harmful effects on human health. Some of these harmful effects are cancer or genetic mutations, depending on the dose and type of radiation. Therefore, it is essential to measure and monitor the amount of radiation exposure. This is to ensure the safety of individuals and the environment.

## 3. Units Used in Radiation Dosimetry

Radiation is measured in different units, depending on the type of radiation and the purpose of the measurement. The most common units used in radiation dosimetry are:

• Gray (Gy): This is the unit of absorbed dose, which measures the amount of energy absorbed by an object per unit of mass. It is used to measure the amount of radiation absorbed by living tissue.
• Sievert (Sv): This is the unit of equivalent dose, which measures the biological damage caused by radiation. It takes into account the type of radiation and the sensitivity of the tissue exposed. We calculate the equivalent dose by multiplying the absorbed dose by a quality factor, which reflects the type of radiation.
• Becquerel (Bq): This is the unit of activity, which measures the number of radioactive decay per second. We use it to measure the amount of radioactive material present.

## 4. Types of Radiation and Their Properties

Radiation can be classified into two main types: ionizing and non-ionizing. Ionizing radiation has enough energy to ionize atoms and molecules, creating charged particles that can interact with living tissue. Non-ionizing radiation has less energy and cannot ionize atoms or molecules.

The most common types of ionizing radiation are:

• X-rays: Electromagnetic radiation with a high frequency and energy, used in medical imaging and radiation therapy.
• Gamma rays: Electromagnetic radiation emitted by radioactive nuclei, with high energy and penetrating power.
• Alpha particles: High-energy particles consisting of two protons and two neutrons, emitted by some radioactive nuclei.
• Beta particles: High-energy electrons or positrons, emitted by some radioactive nuclei.

The properties of radiation, such as its energy and penetration power, determine its biological effects and the methods used to measure it.

## 5. Methods Used in Radiation Dosimetry

We can measure radiation by using various methods, depending on the type of radiation and the purpose of the measurement. Some common methods used in radiation dosimetry include:

• Film badges: These are small dosimeters that contain photographic film. They are worn by individuals exposed to radiation. It also measures the dose of radiation by recording the darkening of the film.
• Thermoluminescent dosimeters (TLDs): These are small devices that contain a crystal that emits light when heated. We also use them to measure the dose of radiation by heating the crystal and measuring the amount of light emitted.
• Ionization chambers: These are devices that measure the ionization of gas by radiation. Furthermore, we use them to measure the dose of radiation in medical imaging and radiation therapy.
• Geiger counters: These are devices that detect
• Scintillation detectors: These are devices that detect the light emitted by radiation when it interacts with a scintillating material. We also use them to measure the energy and type of radiation.

## 6. How to Carry out Radiation Dosimetry

Radiation dosimetry is performed using various methods and techniques to measure and calculate the amount of radiation absorbed by an object or person. These methods depend on the type of radiation, the object or person being measured, and the purpose of the measurement.

One commonly used method of radiation dosimetry is film dosimetry. This technique involves exposing a photographic film to the radiation, which causes changes in the film’s density. The film is then developed, and the degree of blackening is used to calculate the absorbed radiation dose.

Another method is thermoluminescent dosimetry (TLD). This technique uses crystals that emit light when exposed to radiation. The crystals are then heated, and the amount of light emitted is measured, which provides information on the amount of radiation absorbed.

In medical settings, radiation dosimetry is often performed using detectors such as ionization chambers, which measure the ionization produced by the radiation. These detectors are commonly used in external beam radiotherapy to measure the radiation dose delivered to the patient.

In nuclear medicine therapy, radiation dosimetry is performed using imaging techniques such as PET or SPECT scans. These scans provide information on the distribution of the radiopharmaceutical in the body, allowing for the calculation of the absorbed radiation dose in various organs and tissues.

Computer simulations are also used in radiation dosimetry. These simulations use mathematical models to calculate the radiation dose based on factors such as the type of radiation, the source of radiation, and the properties of the materials being irradiated.

## 7. Radiation Dosimetry in Nuclear Medicine Therapy

In nuclear medicine therapy, it is important because the goal of the treatment is to deliver a precise amount of radiation to the tumour while minimizing the radiation exposure to healthy tissues.

Nuclear medicine therapy involves the use of radioactive substances, called radiopharmaceuticals, to treat various conditions such as cancer, thyroid disorders, and bone pain. These substances emit ionizing radiation, which can damage cells and cause radiation sickness if the dose is too high. Therefore, it is essential to measure and control the amount of radiation delivered to the patient.

Radiation dosimetry is used to calculate the amount of radiation delivered to the tumor and healthy tissues during the treatment. This information helps in planning the treatment and adjusting the dose to ensure that the tumour receives enough radiation to be destroyed while minimizing the radiation exposure to healthy tissues.

The measurement of radiation dose is expressed in units such as Gray (Gy) or Sievert (Sv). One gray of radiation dose is equal to the absorption of one joule of energy per kilogram of matter, while one sievert is a measure of the radiation dose that takes into account the type of radiation and the sensitivity of the tissue exposed.

Proper radiation dosimetry helps ensure the safety and effectiveness of nuclear medicine therapy. It helps to prevent underdosing, which can lead to ineffective treatment, or overdosing, which can cause harm to healthy tissues. Additionally, it helps to minimize the risk of long-term effects such as radiation-induced cancers or genetic mutations.

## 8. Applications of Radiation Dosimetry

Radiation dosimetry plays a critical role in various industries and applications, including:

• Nuclear power: We also apply radiation dosimetry in monitoring the radiation exposure of workers in nuclear power plants and ensuring their safety.
• Medical imaging: We also use it to measure the dose of radiation received by patients during medical imaging procedures such as X-rays, CT scans, and PET scans.
• Radiation therapy: Another application of radiation dosimetry is in planning and monitoring the radiation dose delivered to cancer patients during radiation therapy.
• Environmental monitoring: We can use radiation dosimetry to monitor the levels of radiation in the environment and ensure compliance with safety regulations.

## 9. Radiopharmaceutical Therapy: A Leap Towards Targeted Treatment

Radiopharmaceutical Therapy, a beacon of hope in the realm of cancer treatment, capitalizes on the unique properties of radionuclides to precisely target and eradicate malignant cells. The journey from dosimetry studies to personalized treatment unfolds with the collaboration of medical physicists, physicians, and nuclear medicine technologists.

a. Dosimetry Study in Nuclear Medicine Therapy: The significance of dosimetry studies before treatment cannot be overstated. It is the bedrock upon which personalized treatment plans are constructed, ensuring the optimal balance between therapeutic efficacy and minimal side effects.

b. Biodistribution and Clearance Patterns: Understanding the biodistribution and clearance patterns of radiopharmaceuticals is crucial. This knowledge, coupled with dosimetry data, enables precise adjustments in treatment, enhancing its effectiveness.

c. Collaboration Among Experts: A synergy between medical physicists, physicians, and nuclear medicine technologists is paramount. This collaboration ensures a holistic approach, considering both the technical and medical aspects, in delivering targeted radiopharmaceutical therapy.

## 10. Occupational Exposure and Dosimeter Dynamics

In the broader spectrum of radiation applications, occupational exposure demands meticulous attention. Dosimeters, the guardians of safety, play a pivotal role in monitoring and regulating exposure levels.

a. Dosimeter Types and Application: The dosimeter landscape includes whole-body and ring dosimeters, each tailored to specific occupational settings. The dosimeter application process, wear periods, and exchange protocols further contribute to a comprehensive safety framework.

b. Policies and Procedures: The ALARA (As Low As Reasonably Achievable) philosophy governs policies and procedures related to dosimetry. Monthly reviews of exposure reports, investigation of exposures exceeding permissible doses, and guidelines for wearing personal dosimetry collectively ensure a proactive and preventive approach.

c. Dosimeter Individuality and Storage: Recognizing the individuality of dosimeters and implementing proper storage practices are integral. Lost or damaged dosimeters, a potential threat, are addressed through stringent policies to maintain the integrity of exposure data.

d. Dosimeter Wearing Locations and Personal Medical Procedures: Understanding the significance of dosimeter wearing locations, especially in high-risk areas, contributes to accurate exposure assessment. Special considerations, such as pregnancy and fetal dosimeters, add an extra layer of protection.

## 11. Conclusion

Radiation dosimetry is a crucial field that helps measure and monitor radiation exposure and ensure the safety of individuals and the environment. Understanding the units used to measure radiation, the types of radiation, and the methods used to measure it is essential for anyone working with or around radiation. By using proper radiation dosimetry techniques, we can reduce the risks associated with radiation exposure and ensure safe and effective use of radiation in various applications.

## 12. FAQs

1. What is the difference between the absorbed dose and the equivalent dose?
• Absorbed dose measures the amount of energy absorbed by an object per unit of mass, while equivalent dose takes into account the type of radiation and the sensitivity of the tissue exposed.
1. What is the unit of absorbed dose?
• Gray (Gy) is the unit of absorbed dose.
1. What is the unit of equivalent dose?
• Sievert (Sv) is the unit of equivalent dose.
1. What is the purpose of radiation dosimetry?
• Radiation dosimetry is used to measure and monitor the amount of radiation exposure to ensure the safety of individuals and the environment.
1. What are some common methods used in radiation dosimetry?
• Some common methods used in radiation dosimetry include film badges, thermoluminescent dosimeters (TLDs), ionization chambers, Geiger counters, and scintillation detectors.

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