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DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Basic Interactions Between X-Rays And Matter CRT04106 · Radiation Sciences START READING NOTES Study Basic Interactions Between X-Rays And Matter using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic BASIC INTERACTIONS BETWEEN X-RAYS AND MATTER INTERACTIONS OF X RAYS WITH MATTER. COHERENT SCATTERING PHOTOELECTRIC EFFECT The amount of energy is characteristic of each element Application of photoelectron to Diagnostic Radiology COMPTON SCATTERING PAIR PRODUCTION AND PHOTODISINTEGRATION PHOTODISINTEGRATION BASIC INTERACTIONS BETWEEN X-RAYS AND MATTER BASIC INTERACTIONS BETWEEN X-RAYS AND MATTER Based on the work of Rutherford and Bohr a simple mode of an atom may be visualized as a massive positively charged nucleus surrounded by electrons in orbits of specific diameter Atoms are bonded to the molecules by electrons in the outermost shell. X-ray photons may interact with either orbital electrons or with the nucleus of atoms but in the diagnostic energy range, the interactions are always with orbital electrons. Only two interactions are important in diagnostic radiology ; the Photoelectric Effect and Compton scattering INTERACTIONS OF X RAYS WITH MATTER. There are five basic ways that an X-ray photon can interact with matter,these are Coherent scattering. Photoelectric effect. Compton scattering. Pair production. Photodisintegration. COHERENT SCATTERING The name coherent scattering is given to that interaction in which radiation undergoes a change in direction without a change in wavelength. The type of interaction between X-rays and matter that does not cause ionization No energy is transferred and no ionization occurs with coherent scattering the only effect is to change the direction of the incident radiation. Only 5% of the radiation that undergoes coherent scattering compared to other basic interactions It produces scattered radiation contributing to film fog but the total quantity is too small to be important in Diagnostic Radiology. figure PHOTOELECTRIC EFFECT The photoelectric effect occurs when an incident photon with little more energy than the binding energy of a k-shell electron encounters one of these electrons and ejects it from its orbit. The photon disappears giving up all its energy to the electrons (Most of the photon’s energy is needed to overcome the binding energy of the electron and the excess gives the electron kinetic energy). The electron which is now free of its energy debt, flies off into space as a photoelectron As an electron drops into the k-shell it gives up energy in the form of an X-ray photon The amount of energy is characteristic of each element The photoelectric effect always yields three end products Negative ion (Photoelectron) characteristic radiation 3 . A positive ion (an atom deficient in one electron) The probability of occurrence 1 . The incident photon must have sufficient energy to overcome the electron’s binding energy. A photoelectric reaction is most likely to occur when the photon energy and electron binding energy are nearly the same. The tighter an electron is bound in its orbit the more likely it is to be involved in a photo-electronic reaction Application of photoelectron to Diagnostic Radiology Positive effect . it produces radiographic images of excellent quality. The quality is good for two reasons the photoelectric effect does not produce scatter radiation -it enhances natural tissue contrast(x-ray image contrast depends on the tissue absorbing more x-rays than other tissue, contrast is greatest when the difference in absorption between adjacent tissues is large) Negative effect From the point of view of patient exposure, the patient receives more radiation from photoelectric reactions than from any other type of interaction. All the energy of the incident photon is absorbed by the patient in the photoelectric reaction (The importance of the photoelectric effect can be minimized by using high energy KVp technique). COMPTON SCATTERING Almost all the scatter radiation that we encounter in diagnostic radiology comes from Compton scattering. An incident photon with relatively high energy strikes a free outer shell electron, ejecting it from its orbit. The photon is deflected by the electron so that it travels In a new direction as scatter radiation The reaction produces an ion pair, a positive atom, and a negative electron which is called a coil electron The probability of a Compton reaction depends on the total number of electrons in an absorber which in turn depends on its density and the number of electron per gram. PAIR PRODUCTION AND PHOTODISINTEGRATION The last two basic interactions, pair production and photodisintegration do not occur in the diagnostic energy range. They have no importance in diagnostic radiology. In Pair production a high-energy photon interacts with the nucleus of an atom, the photon disappears and its energy is converted into matter in the form of two particles ordinary electron A positron with the same mass as an electron but with a positive charge PHOTODISINTEGRATION In the photodisintegration part of the nucleus of an atom is ejected by high-energy photon The ejected portion may be a neutron, a proton, and an alpha particle or cluster of particles. The photon must have sufficient energy to overcome nuclear binding energies of the order of 7-15 MeV. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Atomic Structure CRT04106 · Radiation Sciences START READING NOTES Study Atomic Structure using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic RELATED TASK ATOMIC STRUCTURE. NUCLEUS. Shell Types of Electrons Key points Atom Isotopes Periodic table Electronic configuration Bohr’s atomic theory Introduction RELATED TASK Describe atomic structure, quantities and units of electro-magnetic radiations, x-ray and gamma rays, primary and secondary radiation. ATOMIC STRUCTURE. Atom is the smallest unit of matter that define the chemical element. Atom made up of two main parts, that are, Nucleus: contains positive protons (p) and neutral neutrons (n) Shells: Contain electrons (e) that circles the nucleus in their energy level. NUCLEUS. Nucleus is the central part of an atom where almost the mass of an atom is present. Nucleus is composed of two main particles. Proton Neutron Protons are positively charged particle present in nucleus. Proton have a mass of 1.6726×10−27 kg. That is, they weigh 1,836 times the mass of electrons. Nucleus Neutrons are charge less particle present in a nucleus of an atom. Neutron have a mass of 1.6929×10−27 kg. that is, they weigh 1,839 times mass of electrons Both protons and neutrons in a nucleus of an atom are called Nucleons. Nucleus The number of protons present in nucleus of an atom is called Atomic number. And is denoted by a letter ‘Z’. The total number of protons and neutron in a nucleus of an atom is called Mass number. And is denoted by a letter ‘A’. Shell Shell is an orbit that consist of an electron(s) which evolves around the nuclear of an atom. Shell are also known as Energy level. Electron is negatively charged particle that revolves on its orbit around the nucleus. Electron has a mass of 9.11×10−31 kg. Each shell (orbit) has its maximum carrying capacity of electron. Shell The capacity of shell to carry the electrons is determined by the formula. 2n2 where n is the number (position) of shell from nuclear. The number of shells are numbered from the inner most shell to outer ward from the nuclear. The inner most shell are numbered as one (n=1) and others are continuously numbered in a sequence. Shells are also named as K, L, M, N Shell Types of Electrons Electrons are either bound or free. Bound electrons: These are the electrons that are held in orbit around the nucleus in the electron shells by the attractive force of the positive nucleus. The binding energy is the positive energy required to overcome the pull of the nucleus and release the electron from the shell. Types of Electrons Free electrons: These are the electrons that are not bound in an electron shell around a nucleus. They have a kinetic energy of: Kinetic energy = ½mv2 where: m = mass, v = velocity The actual binding energy of electrons is expressed in electron volts (eV) or keV (1keV = 1000 eV) 1 eV = 1.6022 x 10 -19 joules Free electron Key points Increase in the atomic number = increase in the binding energy of the electrons (there are more protons and, therefore, more energy is needed to release the electrons from the greater positive pull) Increase in the distance between the nucleus and the electron = decrease in the binding energy of the electron (decrease in the positive pull of the protons in the nucleus) Atom The number of the proton and electron in an atom is equal, thus, this make the atom to be electrically neutral. If either number of proton or electron exceed in an atom, it become electrically charged and is called an Ion. If proton exceed electron it become positively charged. And the atom is named Cation. And if electron exceed it become negatively charged. And the atom is named Anion. Atom Atom The number of proton in an atom determine it’s chemical element properties since each element has it’s own number of proton. For example hydrogen atom has only one proton in its nucleus, while Sodium atom has eleven protons in its nucleus. If the number of proton changed in the nucleus of an atom that atom changes its chemical element properties. Atom Atom of an element become charged by either losing or gaining electron on its outer most shells. Atom if gain extra electron it become negatively charged. And if loses the electron it become positively charged. The process of either gaining or losing of electron in an atom is called Ionization. Ionization Atom The atom of the same chemical element is said to have the same number of neutrons in its nucleus. But there are occasion where the number of neutrons in atom of the same chemical element differs. If the number of neutrons in atoms of the same chemical element differs these atoms are called Isotopes Isotopes Isotope are atoms of the same chemical element but different number of neutrons in its nucleus. Isotope Atomic Structure Isotones are atoms (nuclides) having the same number of neutrons but differ proton number. Example boron-12 and carbon 13 both contain 7 neutrons. Isobars are atoms (nuclides) of different chemical elements having the same atomic mass (number of nucleons). Example 40Ar, 40K and 40Ca. Isobars Isotones Periodic table The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic number, electron configurations, and recurring chemical properties. Elements are presented in order of increasing atomic number, which is typically listed with the chemical symbol in each box. Periodic table The standard form of the table consists of a grid of elements laid out in 18 columns and 7 rows, with a double row of elements below that. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that. Periods: Are rows of the table Groups: Are the columns of the table Periodic

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE X-ray Radiation CRT04106 · Radiation Sciences START READING NOTES Study X-ray Radiation using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Describe x-ray tube housing, shielding, anode, cathode and tube cooling Radiation Propagation in Body Tissue Absorption Transmission Scattering Reflection 1. Tube Housing 2. Shielding 3. Anode 4. Cathode 5. Tube Cooling Radiographic grid Advantages of Grids Disadvantages of Grids X-RAY RADIATION Describe x-ray tube housing, shielding, anode, cathode and tube cooling Describe radiation propagation in body tissue (absorption transmission, scattering reflected) Describe grid its advantages and disadvantages in image quality Explain factors affecting image quality Radiation Propagation in Body Tissue Radiation interacts with human tissues primarily through four key processes: absorption, transmission, scattering, and reflection. These interactions influence the attenuation of the radiation beam and its impact on imaging quality and patient safety. Absorption The process where radiation energy is completely transferred to the atoms or molecules of the tissue. Predominantly occurs through the photoelectric effect, where an X-ray photon ejects an inner-shell electron, transferring all its energy to the atom. This process is crucial for creating image contrast, particularly between tissues of different densities or atomic numbers (e.g., soft tissue vs. bone). Higher atomic number tissues absorb more radiation. Clinical Significance: Increased absorption in denser tissues enhances contrast but also contributes to the patient’s radiation dose. Transmission Radiation passes through tissue without interaction. Occurs when X-ray photons are not absorbed or scattered. Transmission contributes to forming the primary image on the detector. Areas with high transmission appear darker on radiographs. Clinical Significance: Essential for visualizing hollow or low-density structures, such as air-filled lungs. Scattering Radiation photons are deflected from their original path after interacting with tissue. Compton Scatter: Involves interaction with loosely bound outer electrons, resulting in energy transfer and photon deflection. Elastic Scatter: Low-energy photons interact without significant energy loss. Scatter degrades image quality by introducing noise and reducing contrast. Clinical Significance: Minimizing scatter is critical, often achieved using grids or collimators. Reflection Refers to the redirection of radiation photons back towards the source after interaction with tissue. A rare phenomenon in diagnostic imaging, typically occurring at interfaces with substantial density differences. Reflection is minimal in diagnostic radiology and has negligible effects on image formation. Clinical Significance: More relevant in other fields, such as ultrasound imaging, than in X-ray diagnostics. X-Ray Tube Components 1. Tube Housing Function: Provides structural support and safety for the X-ray tube. Shields radiation leakage, ensuring that X-rays emerge only from the designated window or port. Houses cooling oil to dissipate heat generated during operation. Materials: Made of steel lined with lead, except at the port, which is often beryllium or plastic for its low X-ray absorption properties. 2. Shielding Purpose: Minimizes unnecessary radiation exposure to patients and staff by confining radiation to the intended path. Lead is commonly used for shielding because of its high atomic number and effective absorption of scatter radiation. 3. Anode Components: Tungsten-rhenium alloy focal track with a graphite or molybdenum backing. Anode disc (rotating in most diagnostic X-ray tubes) to increase heat capacity. Connected to a molybdenum stem to reduce heat conduction to the rotor assembly. Function: Converts kinetic energy of electrons into X-rays through Bremsstrahlung and characteristic radiation interactions. Rotates to distribute heat generated during exposure. Heat Dissipation: Uses a beveled edge to form the focal track and optimize heat distribution. 4. Cathode Components: Filament (usually tungsten): Produces electrons via thermionic emission when heated. Focusing Cup: A negatively charged nickel or stainless steel housing that narrows the electron beam to ensure it strikes the anode precisely. Function: Provides the electron source required for X-ray production. Controls the number of electrons based on filament current (mA), directly influencing the number of X-rays produced. 5. Tube Cooling Purpose: Prevents overheating of the anode and other components during operation. Methods: Oil Cooling: Mineral oil between the housing and the tube insert acts as a thermal conductor. Rotating Anode: Reduces heat concentration by spreading it across a larger surface area. Forced Air Cooling: Fans and other devices may be employed in high-performance systems Radiographic grid A grid is a device used in radiography to improve image quality by absorbing scattered radiation. The main types of grids include: Stationary grids: Consist of closely spaced thin lead strips separated by radiolucent material (usually plastic or aluminum). They can be parallel or focused (angled towards the center). Moving grids: The grid moves sideways during exposure to blur out grid shadows, reducing artifacts. Digital grids: Use software algorithms to analyze and correct images instead of physical components. Advantages of Grids Improved image quality: Reduce scatter radiation, enhancing contrast and sharpness. Especially beneficial for thicker body parts Contrast enhancement: Higher Z materials produce more contrast due to stronger photoelectric interactions. Reduced artifacts: Minimize haze and structured artifacts caused by scattered radiation. Flexibility: Different grid ratios can be selected based on patient size and energy level. Cost-effective: Traditional physical grids are relatively inexpensive compared to digital alternatives. Disadvantages of Grids Increased radiation dose: Require higher doses to compensate for absorbed primary radiation. Artifacts: Stationary grids leave visible lines on the film/image. Moving grids may introduce distracting patterns. Alignment requirements: Proper alignment is crucial for optimal performance, especially with high-ratio grids. Limited effectiveness: Less effective at very low energies. May not significantly improve image quality for thin body parts Potential obsolescence: Digital alternatives like scatter correction software and AI algorithms are emerging. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Dosimetry Principles CRT04106 · Radiation Sciences START READING NOTES Study Dosimetry Principles using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Objectives Dosimetry Principles Active dosimeters Passive dosimeters Properties of radiation dosimeters: a) Accuracy and Precision c) Dose and Dose Rate Dependence e) Directional Dependence Ionization chambers Clinical Applications Semiconductor Dosimeter Other dosimeters Thermoluminescent Dosimeter (TLD) Optically Stimulated Luminescence Dosimeter (OSL) DOSIMETRY PRINCIPLES Objectives Describe dosimetry and dosimeter. Describe properties of dosimetry. Describe dosimeters and their functions. Dosimetry Principles Dosimetry is the science of measuring and monitoring the dose of ionizing radiation absorbed by matter, particularly human tissue, to ensure safety and accuracy in diagnostic radiology. Dosimetry is essential for: Radiation safety of patients and personnel. Quality control in imaging systems. Compliance with regulatory standards. Dosimetry Principles A dosimeter can be defined as any device that is capable of providing a reading that is a measure of the absorbed dose deposited in a sensitive volume by ionizing radiation. In diagnostic radiology, dosimetric instruments can be classified as either ; Active dosimeters Active dosimeters display the dose value directly. These include ionization chambers and/or semiconductor detectors (sometimes loosely referred to as solid state detectors) used to measure absorbed dose in the primary beam condition Applicable in measurement of patients exit dose and CT phantom dose that use ionization chambers Passive dosimeters Passive dosimeters cannot display the dose value directly, but record a dose signal when exposed to radiation, which must be subsequently retrieved and converted to dose by a reading device. These include solid state devices such as thermoluminescent dosimeters (TLDs), optically stimulated luminescent (OSL) dosimeters and dosimeters (including radiochromic film) that may be placed on a patient’s skin or inside cavities to measure the skin or organ doses. Properties of radiation dosimeters: Dosimeters are used for various types of X ray unit and exposure conditions, the choice of the appropriate instrument is important, in order for the radiation measurement to be sufficiently accurate. Properties of radiation dosimeters; Accuracy and precision Linearity Dose and Dose Rate Dependence Energy response Directional dependence Spatial resolution a) Accuracy and Precision Accuracy: The closeness of the dosimeter reading to the true radiation dose. Precision: Consistency of repeated measurements under the same condition Linearity The dosimeter's response should be proportional to the radiation dose across its operational range. Ensures reliable readings at varying exposure levels. c) Dose and Dose Rate Dependence Dosimeters must function accurately across a range of doses and dose rates, from low (e.g., fluoroscopy) to high (e.g., CT scans). Energy Response Dosimeters should respond consistently across different X-ray energies. Energy correction factors may be applied to ensure accuracy. e) Directional Dependence The response of some dosimeters (e.g., ionization chambers) may vary with the angle of incident radiation. Proper positioning minimizes errors. Spatial Resolution The ability to measure radiation dose in small, localized areas, important for precise patient dosimetry. Ionization chambers Ionization chambers consist of a gas-filled cavity between two electrodes with an applied electric field. When ionizing radiation passes through the chamber, it ionizes the gas molecules, creating positive ions and free electrons. The electric field directs the ions to the electrodes, producing a current proportional to the radiation dose. This current is measured and converted to display the radiation dose in terms of air kerma. Clinical Applications Radiography: Used to measure radiation dose during routine X-ray procedures to ensure proper exposure. Fluoroscopy: Monitors dose rates during real-time imaging to prevent excessive exposure. Mammography: Measures low doses accurately, ensuring optimal image quality with minimal radiation. Computed Tomography (CT): Used in pencil-type ionization chambers to measure dose-length products (DLP) for CT dose assessments. Quality Assurance: Employed in equipment calibration and routine quality control to verify radiation output consistency and compliance with safety standards. Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). Semiconductor Dosimeter Semiconductor dosimeters are made of materials like silicon or gallium arsenide. When exposed to ionizing radiation, electron-hole pairs are generated within the semiconductor material. The resulting electrical current or voltage change is proportional to the absorbed radiation dose. Unlike ionization chambers, semiconductor dosimeters do not require high voltage and provide a highly sensitive and immediate response. They are compact, rugged, and capable of real-time dose measurement. Clinical Applications Interventional Radiology: Real-time dose monitoring during procedures to ensure patient and staff safety, especially in high-dose scenarios. Dose Measurement in Complex Procedures: Useful for precise dose assessment in procedures requiring rapid dose adjustments (e.g., fluoroscopy). Quality Control: Employed in the calibration of imaging equipment and verification of dose settings. Skin Dose Measurement: Ideal for measuring localized radiation doses on the skin during interventional or therapeutic procedures. Radiation Safety Monitoring: Used for occupational exposure monitoring, providing accurate and sensitive measurements of accumulated doses. Other dosimeters Film Dosimeter Records radiation exposure through changes in the optical density of radiation-sensitive film. The degree of darkening correlates with the radiation dose. Clinical Application: Commonly used for personal radiation monitoring (film badges). Suitable for cumulative dose assessment over time. Thermoluminescent Dosimeter (TLD) Stores radiation energy in crystal form, which is released as light upon heating. The emitted light intensity is proportional to the absorbed radiation dose. Clinical Application: Used for patient and personnel dosimetry. Particularly useful in measuring skin and organ doses in phantoms and direct patient applications. Optically Stimulated Luminescence Dosimeter (OSL) Emits light when exposed to a specific wavelength after radiation exposure. The emitted light intensity corresponds to the radiation dose received. Clinical Application: Used for both patient and occupational dosimetry. Ideal for long-term dose monitoring due to high sensitivity and reusability. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiation Protection CRT04106 · Radiation Sciences START READING NOTES Study Radiation Protection using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Objectives Outline Concepts and aims of radiation protection Biological effects of ionizing radiation: aims of radiation protection Protection from what? Justification of practices Justification of a practice Optimization of protection As Low As Reasonably Achievable Limitation of doses Other factors to consider in patient dosimetry Collimation Shielding Dose Reference Levels Personal protective equipment Protective clothing: Thyroid shield CURTAIN Radiation Protection Measures Time Consequence Distance Factors influencing patient exposure in conventional radiography Grids Radiation Protection Objectives Describe dosimetry principle in calculating patients’ dose (Justification, optimization, collimation, shielding and dose reference levels) Describe radiation protective measures ( Protective gargets) Describe time, distance and shielding as protective measures Describe factors influencing patient exposure in conventional radiography Outline System of radiation protection Personal protective equipment Radiation Protection Measures Factors influencing patient exposure in conventional radiography Concepts and aims of radiation protection Radiation Protection is a tool for the management of measures to protect health against the risks (for people and environment) generated by the use of ionizing radiation Always consider BENEFITS Vs RISKS Biological effects of ionizing radiation: aims of radiation protection Deterministic effects RP aims at PREVENTING them. Stochastic effects RP aims at REDUCING them. Protection from what? Unnecessary examination or treatment (justification) Unnecessary exposure (optimization) Inadequate examinations, which can lead to incorrect or incomplete diagnosis (optimization) Justification of practices Limitation of doses Optimization of protection System of radiation protection Justification of a practice Justification means that any exposure produces sufficient benefit to offset the radiation harm that it might cause. Thus, if the exposure has not any benefit it is not justified. Optimization of protection Optimization includes the criterion: doses should be “as low as reasonably achievable”, economic and social factors being taken into account” Optimization means that minimum risk and maximum benefits should be achieved, economic and social factors being taken into account. BENEFIT RISK As Low As Reasonably Achievable refers to the continual application of the optimization principle in the day-to-day practice. DOSE Limitation of doses The normal exposure of individuals shall be restricted so that neither the total effective dose nor the total equivalent dose to relevant organs or tissues, caused by the possible combination of exposures from authorized practices, exceeds any relevant dose limit, except in special circumstances Dose limits shall not apply to medical exposures from authorized practices. Other factors to consider in patient dosimetry Dosimetry is the act of measuring or estimating radiation doses and assigning those doses to individuals Collimation Shielding Dose Reference Levels (DRLs) Collimation Collimation refers to limiting the radiation field to only the necessary area for imaging. Reducing the size of the X-ray beam to match the patient area being imaged Minimizes exposure to unnecessary body parts Improves image quality by reducing scatter radiation Can reduce dose by up to 80% compared to full-field exposures Shielding Shielding involves using physical barriers to block or absorb radiations. Using lead aprons, thyroid shields, gloves, and caps for staff protection Placing concrete walls around radiology rooms to absorb scattered radiation Using lead glass for windows in control areas Properly positioning patients and staff to avoid direct beam exposure Dose Reference Levels Dose reference levels provide benchmarks for acceptable doses in different imaging procedures. Establish diagnostic reference levels for common exams. Measure actual patient doses and compare to reference levels. Use data to optimize protocols and reduce unnecessary exposure. Personal protective equipment Workers are provided with suitable and adequate personal protective equipment which meets any relevant regulations or standards. Protective equipment includes lead aprons, thyroid protectors, protective eye-wear and gloves. The need for these protective devices should be established by the Radiation Protection Officer. Protective clothing: Gowns, aprons and thyroid protectors made of a material (such as vinyl) which contains lead Aprons should be equivalent to at least 0.25 mm Pb if the X Ray equipment operates up to 100 kV and 0.35 mm Pb if it operates above 100 kV Aprons may be of the style which is open, or contains less lead, at the back, due to the extra weight of lead required – this assumes, however, that the wearer is always facing the radiation source Gauntlets are heavy gloves. They have limited value because they are difficult to use and should therefore only be used where appropriate Thyroid shield Lead apron CURTAIN SCREEN AND GOGGLES Protective devices Radiation Protection Measures Time Distance Shielding Time Dose is proportional to the time exposed Dose = Dose-rate x Time Consequence Limiting exposure duration reduces overall dose The longer you're exposed, the more radiation you absorb Minimizing time near radiation sources is crucial For medical procedures, reducing exam time lowers dose Distance dose-rate Dose-rate  1/(distance)2 Inverse square law (ISL): Consequence Increasing distance from the radiation source reduces exposure Radiation intensity decreases rapidly with distance The inverse square law applies – doubling distance reduces dose to 1/4 Moving farther away provides significant dose reduction For medical imaging, positioning patients farther from detectors reduces dose Shielding incident radiation transmitted radiation Barrier thickness Consequence Using barriers to block or absorb radiation Effective shielding depends on the type of radiation Common shielding materials include lead, concrete Examples: Lead aprons, thyroid shields, concrete walls Shielding effectiveness increases with thickness/material density Factors influencing patient exposure in conventional radiography Beam energy Depending on peak kV and filtration Regulations require minimum total filtration to absorb lower energy photons Added filtration reduces dose Goal should be use of highest kV resulting in acceptable image contrast Collimation Area exposed should be limited to area of CLINICAL interest to lower dose Additional benefit is less scatter, netter contrast Grids Reduce the amount of scatter reaching image receptor But at the cost of increased patient dose Patient size Thickness, volume irradiated and dose increases with patient size Except for breast (compression): no control Technique charts with suggested exposure factor

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Mechanisms of Radiation Damage CRT04106 · Radiation Sciences START READING NOTES Study Mechanisms of Radiation Damage using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Objective Outline Introduction Direct Direct Action Indirect Action LINEAR ENERGY TRANSFER (LET) Types of Radiation according to LET LOW LET radiation HIGH LET radiation Time scale of effects of radiation Factors Modifying Radiation Damage or Effect Factors 1. Physical Factors Physical Factors Chemical Factors 3. Biological Factors Biological Factors Summary Radiation Damage Mechanism Objective At the end of this presentation, you are expected to describe radiation cell damage mechanism (Direct and indirect ) and factors modifying radiation damage Outline Basic Interaction of radiation with cell Linear energy transfer (LET) Relative Biological effect (RBE) Factors Modifying Radiation Damage or Effect Introduction The biological effects of radiation result mainly from damage to the DNA, which is the most critical target within the cell; however, there are also other sites in the cell that, when damaged, may lead to cell death. When ionizing radiation is absorbed in biological material, the damage to the cell may occur in 2 ways: Direct Indirect Direct IR  Chemical changes  Biologic effects Indirect IR fast electron (e) + H2O  free radicals  chemical changes  biological effects Direct and indirect actions of radiation on DNA Direct Action Radiation is directly deposited in the critical target, resulting in excitation or ionisation of the target More likely after HIGH LET radiation Produces damage by direct ionisation of a biological macromolecule Indirect Action In indirect action the radiation interacts with other molecules and atoms (mainly water, since about 80% of a cell is composed of water) within the cell to produce free radicals (hydroxyl), which can damage the critical target) within the cell. About 2/3 of the biological damage by low LET radiations e.g. X rays or electrons is due to indirect action. LINEAR ENERGY TRANSFER (LET) Linear energy transfer (LET): is the mean amount of energy that a given ionizing radiation imparts to absorbing medium (such as tissue) per unit path length. Used in radiobiology and radiation protection to specify the quality of an ionizing radiation beam Types of Radiation according to LET There are two types of radiation in respect of linear energy transfer (LET) Low linear energy transfer radiation ( LOW LET radiation) High linear energy transfer radiation ( HIGH LET radiation) LOW LET radiation Are radiation that cause a sparsely ionization to the medium track Examples include X-ray radiation Gamma ray radiation Electron radiation HIGH LET radiation Are radiation that cause a densely ionization to the medium track Examples include Neutron radiation Proton radiation Alpha radiation Other heavy particle radiation Time scale of effects of radiation Physical Chemical Biological Factors Modifying Radiation Damage or Effect Many factors influence or modify radiation damage and may alter radiation effectiveness or lead to unwanted side effects. Factors The following factors may influence Radiation Damage Physical Chemical Biological 1. Physical Factors Include; Type of radiation used Dose Temperature Physical Factors Type of Radiation: High LET (Linear Energy Transfer) radiation such as neutrons or α-particles will usually have a greater biological effect. This is due to increased cell killing as radiation induced damage is more closely spaced. As LET increases over 100 keV/μm, cell killing decreases as the energy delivered exceeds that needed to kill the cell. Physical Factors Dose Total dose is perhaps the most important physical factor. Very low doses are unlikely to lead to any visible response, whereas very high doses (single dose over 20 Gy) have the potential to kill most human cells. Dose Rate at which dose is delivered will also impact on cell survival, as low dose rates allow for DNA repair to occur during radiation delivery. Very low dose rates may also allow reoxygenation or redistribution to occur. Physical Factors Temperature: Increased temperature leads to an increase in cell killing. This is due to deficiency in DNA double strand break repair that occurs at higher temperatures. Chemical Factors The oxygen effect refers to the increased cell killing in oxic conditions. Anoxic cells are between 2 – 3 times more resistant to low LET radiation than oxic cells. Therefore, the addition or reduction in oxygen will have effects on the radiation reaction. Chemical Factors Radiosensitisers, such as cisplatin or 5-fluorouracil, function by increasing the cellular damage caused by radiation. The presence of these chemicals leads to an increase in the observed radiation effect. Radioprotectors, such as amifostine, reduce the effect ionising radiation has on cells. This is often by increasing the availability of anti-oxidants which prevent ‘fixing’ of radiation damage 3. Biological Factors Biological factors are due to the cell being irradiated or the organism. Include; Type of cells example Haemopoietic differentiated cells typically respond to low doses of radiation, whereas well skin cells do not suffer ill consequences except at very high doses Cell cycle stage; Cells in S-phase are typically resistant, whereas those undergoing M-phase are generally much more radiosensitive. Haemopoietic cells- immature cells that can develop into all types of blood cells including white blood cells red blood cells and platelets Biological Factors Age; Children are much more likely to suffer from secondary malignancies due to radiation exposure. Children also have developing tissues (such as cartilage) which can be permanently damaged by low doses of radiation (10 – 20 Gy). Haemopoietic cells- immature cells that can develop into all types of blood cells including white blood cells red blood cells and platelets Summary Various group of factors influence radiation damage. It is vital to aware of such factors as they may alter radiation effectiveness or lead to deleterious side effects. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiation Monitoring CRT04106 · Radiation Sciences START READING NOTES Study Radiation Monitoring using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Objective outline Introduction A record of exposure should be part of the employment record of all radiation workers. RADIATION PROTECTION Protection against radiation Framework of Radiation Protection(System of Radiation Protection) How do we protect? Radiation monitoring The results of external exposure monitoring is used: Personnel Monitoring is the monitoring of individuals who are exposed to radiation during the course of their work. Personnel monitoring Personal monitoring device provides: Ideal monitoring device Optically stimulated luminescence[OSL] Film badge Film budge Thermoluminescence dosimeter Types of TLD badges Guideline for using TLD badge Practical consideration : Thermo- luminescent dosimeter [TLD] OSL POCKET DOSIMETER Advantages of pocket dosimeter : RADIATION SURVEY INSTRUMENTS FOR AREA MONITORING Requirements Ionization Chamber-Type Survey Meter Useful in measuring radiation output from both radiographic and fluoroscopic x-ray equipment. Advantages Proportional Counter. The Geiger-Muller (GM) Disadvantages. Definitions: Why have dose limits? Individual dose limit of radiation exposure[2017 ICRP recommendation] Categorization of people likely to be exposed to radiation Summary Dose limits are a fundamental component of radiation protection so as to: References Radiation protection organizations Personal dosimeter Types of personal dosimeters Control badge Optical stimulated luminescence Pocket Ionization Chamber Types of Pocket Ionization Chamber Special Charging Unit Advantages of Pocket Ionization Chamber Disadvantages of Pocket Ionization Chamber Thermo Luminescence Dosimeter (TLD) Ionizing radiation causes the LiF crystals in the TLD to undergo changes in some of their physical properties. TLD Radiation Meter for Area Survey There are two main kind of dosimeter used to measure radiation exposure in area. Geiger Muller Counter Geiger Muller tube read out Geiger Muller Counter read out G-M counter limitation Ionization chamber RADIATION MONITORING Objective At the end of this lecture you should understand the concept of Personnel and community radiation monitoring , monitoring devices and permissible dose limits. outline Introduction Principle of radiation protection Personnel and Radiation area monitoring devices Permissible dose limits Classified person and Non-designated person Summary References Introduction Ionizing radiation can’t be seen, felt or sensed by human body in any way but excessive exposure to them may have adverse health effect To avoid the excessive exposure, appropriate and efficient radiation monitoring is needed. Radiation exposure must be monitored for both personal safety and regulatory purpose A record of exposure should be part of the employment record of all radiation workers. The radiation dosimetry report will provide average annual effective dose[EfD] to the whole body. Principle of radiation protection RADIATION PROTECTION When to protect ? Why to protect ? Whom to protect ? How to protect ? Protection against radiation The purpose of the radiation protection standard settings define by the International Commission on Radiological Protection (ICRP) are. 1.Prevent the occurrence of deterministic effects of Radiation. 2.Limit the radiation to acceptable level that the occurrence of stochastic effect can be prevented Framework of Radiation Protection(System of Radiation Protection) System of Radiation Protection” is the name given by the ICRP to the application of the 3 basic principles of Radiation Protection (no part should be taken in isolation): Justification of practice Optimization of protection Application of individual Dose Limits Minimum risk, maximum benefit How do we protect? Patient Protection Cardinal principles Technique and exposure parameter selection Filtration Collimation Shielding Immobilization Equipment of low tube current Public protection Information boards Restricted entry inside radiation area Regular radiation survey X-ray room design Radiation warning lamps and signs Professional Protection Patient protection Cardinalprinciples Use protective apparels Minimum fluoroscopy time Unnecessary holding of patients Personnel monitoring ALARA Radiation monitoring The aim of external exposure monitoring is the measurement of: Radiation levels in and around work areas (needs an area monitor) Levels around radiation therapy equipment or source containers (needs an area monitor) Dose equivalents received by individuals working with radiation (needs a personal monitor). The results of external exposure monitoring is used: To assess workplace conditions and individual exposures; To ensure acceptably safe and satisfactory radiological conditions in the workplace; To keep records of monitoring over a long period of time, for the purposes of regulation or as good practice. Personnel monitoring Personnel Monitoring is the monitoring of individuals who are exposed to radiation during the course of their work. Radiologists, radiology technologists, medical physicists, radiographers,nurses and other frequent users of x-ray systems such as endoscopists,anaesthetists, cardiologists, surgeons etc as well as ancillary workers who frequently work in controlled areas should also be monitored. Personnel monitoring Personal dosimeters are used for individual monitoring Records equivalents/effective radiation doses received by individuals working with radiation. All instruments/dosimeters must be calibrated in terms of appropriate quantities used in radiation protection Personal monitoring device provides: Occupational absorbed dose and cumulative life time dose Assurance that dose is within permissible limit Individual monitoring is also used to verify the effectiveness of radiation control practices in the workplace It is useful for detecting changes in radiation levels in the workplace and provide information in case of accidental exposures Ideal monitoring device Characteristics Small, light weight, inexpensive and easy to use Made of materials durable enough to tolerate normal daily use. Able to detect and record both small and large exposures in a consistent and reliable manner. Unaffected by environmental condition(heat, humidity pressure) Unaffected by non ionizing radiation Optically stimulated luminescence[OSL] Film badges Thermoluminescent dosimeter[TLDs] Pocket dosimeter Extremity dosimeter[TLD ring badges] are used for monitoring of the hands only Types of personnel monitoring devices TLD- thermo-luminescent dosimeter, Film badge Disassembled film badge, demonstrating badge components: plastic holder, metal filters, and film packet. Film budge Advantage It gives permanent records Type of radiation and energy can be evaluated Least expensive Small, light, easy to handle Disadvantages Cant give instantaneous reading Its film fades at high temperature and humidity High sensitivity to light, pressure and chemicals Limited shelf life[one month]. Cant measure exposure less than 10mR (100μGy). Thermoluminescence dosimeter (TLD) badge It is based on phenomenon of thermo

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Image Characteristics CRT04106 · Radiation Sciences START READING NOTES Study Image Characteristics using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Tissue Properties XRAY IMAGE CHARACTERISTICS Image Quality Radiographic Density Factors affecting density Contrast Image Characteristics Noise Spatial resolution Patient Age and Gender in Radiation Effects Elderly Gender Considerations Fetal Irradiation Read on…. IMAGE CHARACTERISTICS Tissue Properties Density and Atomic Number: Tissues in the body, such as bone, muscle, and fat, vary in density and atomic composition. Bones, with higher atomic numbers (mainly calcium), are denser and absorb more radiation compared to softer tissues like muscle or fat. This differential absorption creates contrast in imaging. Thickness: Thicker tissues absorb more radiation, impacting the degree of penetration and attenuation, which can affect image brightness and detail. Differentiation and Composition: Different tissues (e.g., soft tissue vs. bone) exhibit distinct interaction patterns with x-rays, depending on their composition (e.g., water, fat, mineral content). Higher-density tissues like bone absorb more x-rays, appearing white or light on x-ray images, while lower-density tissues allow more x-rays to pass through and appear darker. XRAY IMAGE CHARACTERISTICS A Radiograph appears a black and white image or picture with varying shades of gray Radiolucent ; Materials that are less dense and allow x-rays to pass through them. For example, muscle and skin are radiolucent and appear black or dark gray on an x-ray. Radiopaque; Materials that are dense enough to resist x-rays and appear white or light gray on an x-ray. For example, bones are radiopaque and appear white or light gray on an x-ray. Image Quality Quality of a radiographic image is its ability to produce a visible patten of varying transmissions of x-rays through the subject being radiographed. Image characteristics include; Radiographic Density Contrast Noise Resolution Radiographic Density Density is the amount of the overall blackness produced on the image after processing A radiograph that is too light has insufficient density to visualize anatomic structures while if its too dark, has excessive density and anatomic parts can not be visualized. Factors affecting density X-ray Absorption: Dense structures like bones absorb more X-rays, resulting in brighter areas on the image. In contrast, softer tissues absorb fewer X-rays and appear darker. Exposure Settings: The amount of radiation exposure (controlled by mAs – milliampere-seconds) directly affects image density. Higher mAs produces darker images, while lower mAs produces lighter images. Contrast Contrast is the degree of difference between adjacent densities. It is the photographic density difference between two adjacent areas on a film/image The ability to distinguish between densities enables differences in anatomical tissues to be visualized. Contrast can be evaluated best when the radiographic density is adequate to visualize density differences Image Characteristics The radiographer is required to understand the anatomic structure to be radiographed for him/her to determine the factors required to achieve desired level of radiographic contrast. Factors affecting contrast; Kilovoltage Grids Collimation Object to Image receptor distance Anatomic part Contrast media Processing Noise Noise is random variation in image brightness that can obscure details, often appearing as graininess: Quantum Noise: Caused by the limited number of X-ray photons reaching the detector, it is more noticeable in low-dose imaging. Electronic Noise: Arises from the electronic components of the imaging system, particularly in digital detectors. Scatter: Scattered radiation (from Compton scattering) contributes to noise, which can be managed using techniques like grids that absorb scattered photons before they reach the detector. Reducing noise while maintaining diagnostic quality often involves balancing the dose and exposure settings. Spatial resolution Resolution is the ability to image two separate objects and visually distinguish one from the other. Spatial resolution is the ability to image small structures that have high subject contrast such as bone-soft tissue interface. When all of the factors are correct conventional radiography has excellent spatial resolution Patient Age and Gender in Radiation Effects Patient age and gender play crucial roles in assessing radiation effects due to differences in tissue sensitivity and life expectancy. Age Considerations Children: Children’s tissues are more radiosensitive, especially growing organs and cells, making them more vulnerable to radiation damage and potential long-term effects, including cancer. They also have a longer life expectancy, increasing the time for radiation effects to manifest. Elderly Older adults have reduced cell repair capacity but may have less concern for long-term effects due to shorter life expectancy. Age-related factors such as bone density and metabolic rates also influence radiation absorption and tissue response. Gender Considerations Female Sensitivity: Studies indicate women generally have a slightly higher risk for certain radiation-induced cancers (e.g., breast cancer) due to glandular tissue sensitivity. Pregnancy: Pregnant patients require special consideration due to potential effects on the fetus, which is particularly sensitive to radiation in early development stages. Fetal Irradiation Between conception and birth the fetus passes through (3) basic stages of development: Implantation (day 1 to 10) Organogenesis (day 11 to 42) Growth stage (day 43 to birth) Fetal Irradiation Radiation is a known teratogen. The effects of radiation on the fetus depend on two factors: the dose and the stage of development at the time of exposure. The principal effects of radiation on a fetus are fetal or neonatal death, malformations, growth retardation, congenital defects and cancer induction. An abortion to avoid radiation induced congenital abnormalities should be considered only when the foetal dose exceeds 10 cGy. Read on…. Body habitus ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE X-ray Production, Spectrum and Radiation Protection CRT04106 · Radiation Sciences START READING NOTES Study X-ray Production, Spectrum and Radiation Protection using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic X-ray Production, Spectrum and Radiation Protection ✓ X-Ray Production Anode Heat ✓ Radiation Quantity A. Radiation Protection ✓ Personnel Monitoring Personal Dosimeters Special Dosimeters X-ray Production, Spectrum and Radiation Protection RADIATION SCIENCE CHAPTER 4 X ray production X-ray spectrum Radiation quantity, quality and intensity Control of scatter Radiation protection and personnel monitoring ✓ X-Ray Production X-rays are produced in an X-ray tube when high-speed electrons (kinetic energy) interact with a metal target (usually tungsten). ➢ Electrons traveling from cathode to anode constitute the x-ray tube current and are sometimes called projectile electrons. When these projectile electrons hit the heavy metal atoms of the x-ray tube target, they transfer their kinetic energy to the target atoms. The projectile electron interacts with the orbital electrons to produce characteristic x-rays or the nuclear field to produce Bremsstrahlung x-rays of target atoms. These interactions result in the conversion of electron kinetic energy into thermal energy (heat) and x-rays. Anode Heat Most of the kinetic energy of projectile electrons is converted into heat. Approximately 99% of the kinetic energy of projectile electrons is converted to heat. Only approximately 1% of projectile electron kinetic energy is used for the production of x-radiation.Two major mechanisms create X-rays: Bremsstrahlung Radiation (Braking Radiation) Bremsstrahlung x-rays are produced when a projectile electron is slowed by the nuclear field of a target atom nucleus. Bremsstrahlung is a German word that means “sloweddown radiation.” ➢ Bremsstrahlung x-rays can be considered radiation that results from the braking of projectile electrons by the nucleus. Produces a continuous spectrum of photon energies. Is the major source of diagnostic X-rays. Characteristic Radiation Characteristic x-rays are emitted when an outer-shell electron fills an inner-shell void. An outer electron fills the vacancy and releases energy as an X-ray photon. Produces discrete (monochromatic) peaks at specific energies characteristic to tungsten (e.g., 59 and 67 keV).✓ X-Ray Spectrum The word spectrum refers to the range of values of any quantity such as x-rays. The X-ray spectrum displays the distribution of photon energies produced by the tube.Components a)Continuous spectrum A continuous spectrum contains all possible values. Bremsstrahlung radiation; ranges from 0 keV to a maximum equal to the kVp.b)Characteristic/discrete spectrum A discrete spectrum contains only specific values. Sharp spikes at the energies unique to tungsten. Factors influencing the spectrum 1.kVp (peak kilovoltage) Increases maximum photon energy. Shifts the entire spectrum to the right (higher energies). Increases beam quality and quantity.2.mA or mAs (tube current ) Linearly increases the number (quantity) of photons. Does not change maximum energy or beam quality. 3.Filtration Removes low-energy photons. Decreases quantity but increases average energy. 4.Target material Higher atomic number → higher energy photons and more efficient production. 5.Generator type (single-phase, three-phase, high-frequency) More consistent voltage increases beam quantity and average energy. ✓ Radiation Quantity Also known as beam output or radiation intensity. Refers to number of photons produced. Depends primarily on mAs. Higher mAs = more electrons = more X-rays produced. Quantity is directly proportional to mAs.✓ Radiation Quality Quality describes the penetrating ability of the X-ray beam. It is determined mainly by kVp and filtration. Higher kVp → higher energy photons → more penetrating beam. More filtration increases average beam energy (hardens the beam). Quality is often measured using half-value layer (HVL) — the thickness of a material needed to reduce intensity by half.✓ Radiation Intensity Intensity refers to the rate of energy fluence at a given distance. Depends on mAs, kVp², filtration, target material, distance. Follows the inverse square law: “Radiation intensity decreases proportionally to the square of the distance from its point source.”✓ Control of Scatter Radiation Scatter radiation mainly results from Compton interactions in the patient.Methods to reduce or control scatter Collimation Reduces field size → less tissue irradiated → less scatter. Most effective method. Grids Absorb scatter before reaching the detector. Used for body parts > 10 cm thickness. Improve image contrast but increase patient dose. Air Gap Technique Increasing distance between patient and detector reduces scatter reaching the detector. Beam Filtration Removes low-energy photons, slightly reducing scatter production. Optimal kVp Selection Lower kVp produces less Compton scatter, but must balance with adequate penetration. Compression Reduces tissue thickness → less scatter.Radiation Protection and Personnel Monitoring These are key components of radiation safety, especially in medical, industrial, and research environments where ionizing radiation is used. A. Radiation Protection Radiation protection aims to protect people and the environment from the harmful effects of ionizing radiation while allowing its beneficial uses. Objectives Prevent deterministic effects (e.g., skin burns, radiation sickness) Reduce the probability of stochastic effects (e.g., cancer, genetic effects) Fundamental Principles (ICRP) 1.Justification – Any activity involving radiation must provide more benefit than harm. 2.Optimization (ALARA) – Radiation exposure should be kept As Low As Reasonably Achievable. 3.Dose Limitation – Individual doses must not exceed recommended limits. NB; ICRP ~ International Commission on Radiological Protection Methods of Radiation Protection a)Time: Minimize time spent near radiation sources. b)Distance: Increase distance from the source (inverse square law). c)Shielding: Use appropriate materials (lead, concrete, water). d)Containment: Sealed sources and controlled areas. e)Administrative controls: Work procedures, training, signage. Personal protective equipment (PPE): Lead aprons, gloves, thyroid shields. Dose Limits (Typical ICRP Recommendations) Occupational workers: o 20 mSv/year (averaged over 5 years) o Maximum 50 mSv in any single year Public: 1 mSv/year Lens of the eye: 20 mSv/year (occupational) Skin & extremities: 500 mSv/year ✓ Personnel Monitoring Personnel monitoring is the measurement and assessment of radiation doses received by workers. Purpose Ensure compliance with dose limits Detect abnormal or accidental exposures Maintain dose records Improve radiation protection practicesPersonnel Monitoring Devices Personal Dosimeters Personal dosimeters are devices worn by radiation workers to measure and record the dose of ionizing radiation received over a specific period. Purpose of Personal Dosimeters i

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Characteristics Of Ionizing Radiation In Tissue CRT04106 · Radiation Sciences START READING NOTES Study Characteristics Of Ionizing Radiation In Tissue using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Learning objectives DNA…. ….. Cellular response to ionizing radiation Quantities of ionizing radiation BIOLOGICAL EFFECTS OF IONIZING RADIATION Deterministic (non stochastic) effect Acute effects of higher radiation exposure EFFECTS TO FOETUS Stochastic (health) effect TLD Advantages of TLDs Disadvantages of TLDs CHARACTERISTICS OF IONIZING RADIATION IN TISSUE Learning objectives At the end of this session the student should be able to: Apply knowledge of molecular biology in relation to radiation sciences Describe the properties of x-rays in living tissues and cellular response to ionizing radiation Understand the quantities and units of radiation Describe the biological effects of ionizing radiation Describe the mechanism of functioning of radiation Thermoluminescent dosimeter (TLD) OVERVIEW OF STRUCTURE OF DNA DNA…. DNA…. DNA, or deoxyribonucleic acid, is a complex molecule that carries genetic information in living organisms. Double helix: The twisted ladder-like shape of DNA, which is composed of two strands of nucleotides wound around each other. Nucleotide: The basic building block of DNA, consisting of a sugar molecule, a phosphate group, and a nitrogenous base. Nucleoside: Consists of sugar and nitrogenous base Sugar-phosphate backbone: The alternating sugar and phosphate molecules that make up the outer edges of the DNA double helix. DNA… Nitrogenous base: The chemical component of the nucleotide that provides the genetic code for the DNA molecule. Adenine (A): A nitrogenous base that pairs with thymine (T) in the DNA molecule. ….. Thymine (T): A nitrogenous base that pairs with adenine (A) in the DNA molecule. Guanine (G): A nitrogenous base that pairs with cytosine (C) in the DNA molecule. Cytosine (C): A nitrogenous base that pairs with guanine (G) in the DNA molecule. Hydrogen bond: The weak bond that holds together the nitrogenous base pairs in the DNA molecule. Base pair: The complementary pairing of nitrogenous bases in the DNA molecule (A-T and C-G). 5′ and 3′ ends: The two ends of the DNA molecule that are defined by the position of the sugar molecule. CELL CYCLE Cellular response to ionizing radiation Ionizing radiation such as x-rays can affect the atoms in living things, so it poses a health risk by damaging tissue and DNA in genes. Ionizing radiations like x-rays and gamma rays have sufficient energy to affect the atoms in living cells and thereby damage their genetic material (DNA). Fortunately, the cells in our bodies are extremely efficient at repairing this damage. …. Radiation can kill the cells by inhibiting their ability to divide, its effects in human beings occur primarily in tissues with high cell turnover or renewal rates characterized by a large amount of proliferative activity. However, if the damage is not repaired correctly, a cell may die or eventually become cancerous. …… Radiation can kill cells by two distinct mechanisms. The first is apoptosis (=falling off), also called programmed cell death or interphase death (facilitated by apoptotic genes) .It is an active process that involve DNA fragmentation and cell shrinkage and fragmentation. Cells undergoing apoptosis as an immediate consequence of radiation damage usually die in interphase within a few hours of irradiation.e.g low doses of radiation can induce apoptosis in lymphocytes, spermatogonia (stem cells) and oocytes. … Second mechanism is called necrosis (Greek word Nekrosis= death) that involves loss of cell membrane integrity, leakage of cell contents, enzymatic digestion of cells with multiple death (autolysis) ….. Quantities of ionizing radiation i)Radioactivity /Radiation intensity (directly measurable): Represents rate of radioactive decay and is measured in Becquerel (Bq) as per SI unit. i.e. 1 Bq= 1 decay per second. Other unit used is Curie (Ci) where 1Ci=3.7×10^10 Bq (for Radium) and 1Bq= 2.7×10^ -11 Ci Quantities of ionizing radiation……… Radiation dose quantities: ii) Absorbed dose/Exposure dose (directly measurable): Is the amount of energy deposited per unit mass (C/kg) in a person. It is measured in gray (Gy) as per SI unit. Other unit used is rad where 1Gy=100 rad …… iii) Equivalent dose (protection quantity): This indicates effects on individual human organs and tissues. It is measured in sievert (Sv) as per SI unit. iv) Effective dose (protection quantity): This indicates effects on the whole body by combining effects on individual organs and tissues. It is measured in sievert (Sv) as per SI unit. BIOLOGICAL EFFECTS OF IONIZING RADIATION There are two general types of biological effects from ionizing radiation namely: Deterministic effects and Stochastic effects Deterministic (non stochastic) effect Deterministic effects are those effects whose severity in the exposed individual is dependent on dose; these effects are commonly regarded as having a threshold. Deterministic effects (tissue reactions) are symptoms caused by deaths or degeneration of a number of cells constituting organs and tissues. Since in most organs and tissues there is a continuous process of loss and replacement of cells, a slight increase in the rate of loss due to cell killing can be compensated for by an increase in the replacement rate. If the radiation exposure is higher, there may be some reduction in function of that particular tissue. Acute effects of higher radiation exposure Acute radiation syndrome(radiation sickness ):Refers to health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time -Bone marrow syndrome (drop in the number of blood cells (pancytopenia) . -Gastrointestinal syndrome (nausea and vomiting, rectal bleeding, diarrhoea. -Neurovascular syndrome (headache, fever, dizziness, confusion (disorientation). Skin reddening and tenderness Hair loss (alopecia) Infertility Congenital malformations Skin reddening EFFECTS TO FOETUS 0.1 Gy at an early stage of pregnancy (preimplantation period) may lead to miscarriage. Congenital malformations and brain maldevelopments in the fetus. Stochastic (health) effect Health effect whose probability of occurrence depends on the dose received. Occurrence is usually many years after the exposure, and there is believed to be no threshold level of dose below which