Radiation Biology Exam April 2008

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Questions and Answers

State TWO units that are used in ionising radiation dosimetry.

Gray (Gy) and Sievert (Sv)

List FOUR types of ionizing radiation.

Alpha particles, beta particles, gamma rays, and neutrons.

List TWO types of interaction between radiation and tissue.

Photoelectric effect and Compton Scattering

Identify TWO types of ion that are produced in the absorption of radiation by a water molecule.

Positive (H+) and negative (OH-) ions. Signup and view all the answers

State FOUR categories of radiation effects on DNA.

Base damage, single-strand breaks, double-strand breaks, and cross-linking Signup and view all the answers

Define "cell differentiation".

Cell differentiation is the process by which a less specialized cell becomes more specialized, leading to the development of various cell types with specific functions in the body. Signup and view all the answers

List FOUR categories of cell population in terms of their radiation sensitivities.

Stem cells, differentiating cells, mature cells, and reproductive cells. Signup and view all the answers

Name TWO categories of normal tissue based on the turnover kinetics of the critical target cells in different tissue.

Rapidly proliferating tissues and slowly proliferating tissues. Signup and view all the answers

Explain in brief the following: ai) Stochastic Effect. b) Deterministic Effect.

Stochastic effect refers to an effect whose probability of occurrence increases with dose but the severity of the effect is independent of dose. While Deterministic effect refers to an effect whose severity increases with dose, affecting the cells directly by damaging their DNA. Signup and view all the answers

Define the following: ai) Necrosis. b) Cancer. c) Neoplasm.

Necrosis is the premature death of cells in a living organism due to injury or disease. While Cancer is a disease caused by uncontrolled cell growth and the ability of abnormal cells to invade or spread to other parts of the body. In addition, a neoplasm is any abnormal new growth of tissue in the body, especially one that is not cancerous. Signup and view all the answers

In relation to damage to DNA, explain mutation in humans.

A mutation is any permanent alteration in the nucleotide sequence of the genome of an organism, often resulting in altered protein function or gene expression. These changes in the DNA sequence are often associated with inherited or acquired diseases in humans. Signup and view all the answers

Discuss TWO radiation effects on cellular constituents other than DNA and chromosome.

Radiation can cause damage to cellular membranes, affecting cellular integrity and permeability. In addition, radiation can deplete cellular energy stores, interfering with essential cellular processes like metabolism and repair. Signup and view all the answers

Define the following terminologies: ai) A Controlled area. b) A Supervised area.

A controlled area is typically a defined location with controlled access, where radiation levels are monitored and precautions are in place to minimize radiation exposure. In contrast, a supervised area is a location where radiation exposure is possible but is not subject to the same level of control as in a controlled area. Signup and view all the answers

In relation to the Atomic Energy Licensing Act 1984 briefly define the following: ai) Annual dose. b) Medical exposure. c) Personnel monitoring.

An annual dose refers to the total radiation dose received by an individual during a year. Medical exposure is the intentional exposure to radiation for diagnostic or therapeutic purposes in healthcare settings. In addition, personnel monitoring involves using dosimeters to track the accumulated radiation dose received by individuals working in radiation-related fields. Signup and view all the answers

List FOUR shielding materials that can be used for protective barrier in an x-ray room.

Lead, concrete, steel, and barium sulphate. Signup and view all the answers

In relation to shielding of an x-ray room, define briefly the following: ai) Primary protective barrier. b) Secondary protective barrier. c) Workload.

A primary protective barrier is designed to attenuate the direct beam from the x-ray source, protecting individuals from high-intensity radiation. A secondary protective barrier is intended to attenuate scattered or leakage radiation, minimizing exposure from indirect radiation sources. Workload refers to the total amount of radiation generated by an x-ray unit during a specified period. It is typically expressed in milliampere-minutes per week and reflects the overall activity of the facility. Signup and view all the answers

In relation to cell and tissue responses to radiation, discuss the following: ai) Division delay b) Interphase death c) Reproductive failure.

Division delay is a temporary arrest of cell division following radiation exposure, allowing time for DNA repair or cell death if the damage is too severe. Interphase death refers to the death of a cell during interphase, the stage between cell divisions, while reproductive failure describes the inability of a cell to undergo successful division after irradiation, preventing the formation of new daughter cells. Signup and view all the answers

Describe in brief the shouldered survival curve.

The shouldered survival curve is a graphical representation of the relationship between radiation dose and the fraction of cells surviving after irradiation. It typically shows an initial shoulder region where cell survival remains relatively high before a steeper decline, reflecting a threshold effect where a certain amount of radiation is required before significant cell death occurs. Signup and view all the answers

Discuss in brief the law of Bergonie and Tribondeau.

The law of Bergonie and Tribondeau states that cells that are rapidly dividing, undifferentiated, and have a long future division potential are more radiosensitive, that is, they are more susceptible to radiation damage. Signup and view all the answers

In relation to tissue respond to radiation, discuss in brief mechanism of damage in normal cells.

Radiation can damage normal cells through direct and indirect effects. Direct effects involve direct interactions of radiation with cellular components like DNA, leading to breaks and mutations. Indirect effects involve the creation of reactive oxygen species (ROS) through the radiolysis of water, which can damage cellular macromolecules and cause oxidative stress. Signup and view all the answers

In relation to radiation effects on the embryo and fetus, discuss the following: ai) Lethality b) Congenital abnormalities c) Long term effect.

Lethality refers to the death of the embryo or fetus due to radiation exposure. Congenital abnormalities are structural defects or abnormalities present at birth that can be caused by radiation exposure during development. Long-term effects include an increased risk of developing cancer, infertility, and other health problems later in life. Signup and view all the answers

Explain in brief the main provisions of the following that are relevant to radiation protection: ai) Act 304 Atomic Energy Licensing Act 1984. b) Radiation Protection (Basic Safety Standard) Regulations 1986.

The Act 304 Atomic Energy Licensing Act 1984 established a regulatory framework for the licensing and control of activities involving nuclear technology and radioactive materials, including setting safety standards and ensuring the safe handling and disposal of radioactive materials. The Radiation Protection (Basic Safety Standard) Regulations 1986 introduced comprehensive regulations for radiation protection, specifying permissible dose limits for workers and the public and outlining requirements for radiation safety management, worker training, and the use of protective equipment. Signup and view all the answers

Describe a radiation protection procedure for minimizing dose to personnel in an x-ray imaging department.

Radiation protection procedures in an x-ray imaging department typically involve optimizing the exposure parameters (kVp, mAs) for each patient, using appropriate shielding for workers and the patient, ensuring proper equipment calibration and maintenance, and implementing strict protocols for the management of radioactive materials. Signup and view all the answers

Describe in brief the following: ai) Radiation protection principles b) Radiation protection actions.

Radiation protection principles are fundamental guidelines for minimizing radiation exposure, including justification of exposure, optimization of exposures, and limitation of individual doses. These principles encompass the ALARA (As Low As Reasonably Achievable) approach, prioritizing the reduction of radiation exposure whenever possible. Radiation protection actions are specific measures taken to limit radiation exposure, such as using shielding, distance, and time to reduce exposure, and establishing workplace controls to minimize hazards. Signup and view all the answers

Describe in brief THREE parameters that are used in the formulae to calculate shielding thickness of an x-ray installation.

The three parameters commonly used in shielding calculations are:1. The half-value layer (HVL) of the material, which represents the thickness required to reduce the radiation intensity by half.2. The workload of the x-ray unit, measuring the total radiation output over a specific time period, typically expressed in milliampere-minutes per week.3. The use factor, which accounts for the fraction of time that the x-ray beam is directed towards the barrier, reflecting the usage patterns of the x-ray unit. Signup and view all the answers

A fixed x-ray machine with maximum 100 kVp is going to be installed at about 4 meter from a primary barrier and one meter from the wall opposite of the primary barrier. Given the attenuation graph of x-ray beam 100 kvp, maximum mAs of 200 mAs (refer to Appendix 1), and the x-ray room dimensions of 5 m x 4m x 4 m (length x width x height). Calculate the thickness of the primary barriers made of lead required for proper design of the x-ray room. State clearly your assumptions in the calculation.

To calculate the lead thickness for the primary barrier, we need to consider the following factors:1. The maximum energy of the x-ray beam, which is 100 kVp.2. The distance from the x-ray source to the barrier, which is 4 meters.3. The workload of the x-ray machine, which is 200 mAs.4. The desired level of attenuation, which is the amount of radiation reduction required for safety.5. The half-value layer (HVL) of lead for 100 kVp, which can be obtained from the attenuation graph in Appendix 1.6. The use factor, which we assume to be 1 in this case, signifying the continuous use of the x-ray beam towards the barrier.Using these factors, we can calculate the required lead thickness by applying the appropriate shielding formulas, which are based on the principles of exponential attenuation of radiation. The calculations will involve considering the specific values from the attenuation graph and using the provided workload and HVL of lead. The lead thickness will be determined based on the desired level of attenuation and the geometric configuration of the x-ray room. This calculation should result in a specific lead thickness for the primary barrier, ensuring the safety of personnel and the environment. Signup and view all the answers

Flashcards

Ionizing Radiation Dosimetry Units

Units used to measure ionizing radiation exposure.

Types of Ionizing Radiation

Categories of radiation that can remove tightly bound electrons from atoms.