Author name: contact@devinevisiontech.com

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

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Characteristics Of Ioning Radiation In Tissue CRT04106 · Radiation Sciences START READING NOTES Study Characteristics Of Ioning 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 Characteristics Of Ioning Radiation In Tissue Quantities of ionizing radiation BIOLOGICAL EFFECTS OF IONIZING RADIATION Deterministic (non stochastic) effect Early deterministic somatic effects occur within a short period of time after exposure to ionizing radiation. Acute radiation syndrome (ARS) EFFECTS TO FOETUS Stochastic (health) effect Thermoluminescent dosimeter Disadvantages of TLDs Advantages 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. Understand the quantities and units of radiation Cellular response to ionizing radiation Describe the biological effects of ionizing radiation Describe the mechanism of functioning of radiation dose measuring device 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. 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. Characteristics Of Ioning Radiation In Tissue 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) CELL CYCLE ….. 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. Early deterministic somatic effects occur within a short period of time after exposure to ionizing radiation. These effects include nausea, fatigue, erythema, epilation, and blood and intestinal disorders. Acute radiation syndrome (ARS) Acute radiation syndrome (ARS) refers to health effects that are caused by being exposed to high amounts of ionizing radiation in a short period of time. ARS can manifest as; Hematopoietic syndrome; Bone marrow syndrome, causes the number of red blood cells, white blood cells, and platelets to decrease. Gastrointestinal syndrome; (nausea and vomiting, rectal bleeding, diarrhea). Cerebrovascular syndrome; (headache, fever, dizziness, confusion (disorientation) Skin reddening and tenderness Hair loss (alopecia)

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiation Effects in Body Tissues CRT04106 · Radiation Sciences START READING NOTES Study Radiation Effects in Body Tissues using the sections below. Use the topic navigation to continue through Radiation Sciences. Radiation Effects in Body Tissues RADIATION SCIENCE CHAPTER 3 Cell chemical composition Cell differentiation Radiation damage at cellular level Patient age and gender in radiation effects Radiation in Tissue When ionizing radiation (X-rays, gamma rays, particles) interacts with tissue, its biological effects depend on; chemical composition of cells their level of differentiation mechanisms of damage at the cellular level Levels Of Structural Organization of a Human Body About cell A cell is the basic structural and functional unit of living organisms. So when you define cell properties you are in fact defining the properties of life. The activity of an organism depends on both the individual and the collective activities of its cells. Continuity of life has a cellular basis. ✓ Cell Chemical Composition Inorganic compounds o Are compounds which lack carbon and have a simple structure.o Includes; Water, salts, acids and bases. o Water is the most abundant and important inorganic compound in living material. It makes up 60–80% of the volume of most living cells. o Their molecules have only a few atoms and cannot be used by cells to perform complicated biological functions Organic compounds (~20–30%) o Are relatively large carbon-based molecules and have unique characteristics that allow them to carry out complex biological functions. o Includes; carbohydrates, lipids, proteins, nucleic acids, and adenosine triphosphate (ATP).✓ Cell Propagation Cells propagate (increase in number) through division.❖There are two types of human cells in the body; Germ cells ii. Somatic cells Germ cells These are special cells that are involved in sexual reproduction. These are; – Sperms in males Eggs (ova) in females Division of germ cells is called meiosis and involves two fissions of the nucleus giving rise to four sex cells, each possessing half the number of chromosomes of the original germ cell.Somatic cells These are all other cells in the body that are not involved in reproduction. Division of somatic cells is called mitosis and results in two genetically identical daughter cells. When a somatic cell divides, two cells are produced each carrying a chromosome complement identical to that of the original cell. New cells themselves may undergo further division and the process continues producing a large number of progenies. 𝐍𝐁; Mitosis results in identical cells. This alone is not going to result in different body cells with different functions. To achieve different cells performing different functions in the body, cells also undergo cell differentiation.✓ Cell Differentiation Definition Cell differentiation is the biological process unspecialized cell (like a stem cell) develops into a specialized cell type with distinct structures and functions (e.g., muscle cell, nerve cell, red blood cell). Somatic cells are classified as: Stem cells Are special human cells that are able to develop into many different cell types. ii. Transit cells Which are cells in movement to another population and have properties intermediate between stem and mature cells. iii. Mature cells, Which are fully differentiated and do not exhibit mitotic activity. Examples of Differentiated Cells Erythrocytes (RBCs): Specialized to transport oxygen (contain hemoglobin, lack nucleus). Neurons: Specialized for transmitting impulses (long axons, dendrites). Muscle cells: Specialized for contraction (contain actin and myosin). Epithelial cells: Specialized for protection, secretion, and absorption. Importance of Cell Differentiation Creates diversity of cell types in the body (over 200 in humans). Enables formation of tissues and organs. Crucial for growth, repair, and healing. Malfunction of differentiation can lead to cancers and developmental disorders.✓ Cell Cycle Cell cycle is a series of events that a cell passes through from the time it was produced to its death. It is the growth and division of a single cell into daughter cells and duplication (replication). In prokaryotic cells, the cell cycle occurs termed binary fission but in eukaryotic cells, cell cycle can be divided into two periods namely; a)Interphase b)Mitosis Interphase These is the first phase that prepare a cell for division. During this period a cell grows, accumulate nutrients needed for mitosis and duplicate its DNA. Interphase consists of three stages namely G1 (Pre -synthetic phase) S (DNA synthesis phase) G2 (Pre mitotic phase) Mitotic phase Mitotic phase involves division of cell to produce two daughter cells.❖Mitosis involves four stages Prophase Metaphase Anaphase Telophase Time between successive divisions (mitoses) is called cell cycle time. Cell cycle time for mammalian cells is of the order of 10 – 20 hours: S phase is usually in the range of 6 – 8 hours. M phase is less than 1 hour. G2 is in the range of 2 – 4 hours. G1 is in the range of 1 – 8 hours.❖Cell cycle time for stem cells in certain tissues is up to 10 days. In general, cells are most radio-sensitive in the M and G2 phases, and most radio-resistant in the late S phase. Cell cycle time of malignant cells is shorter than that of some normal tissue cells, but during regeneration after injury normal cells can proliferate faster.✓ Radiosensitivity Radiosensitivity refers to how sensitive a cell is to radiation damage o Cells are more radiosensitive if they are: 1.Actively dividing (high mitotic rate). 2.Undifferentiated (immature). 3.Have a long-life span (young age). • Highly Radiosensitive Cells o Stem cells, bone marrow cells, lymphocytes, spermatogonia, basal cells of skin, intestinal crypt cells. Moderately Radiosensitive Cells o Endothelial cells, fibroblasts, salivary gland cells, growing cartilage and bone cells. • Radioresistant Cells o Nerve cells, muscle cells, fully differentiated connective tissue.✓ Radiation Damage at Cellular Level Basic Concept When ionizing radiation (X-rays, γ-rays, particles) passes through a cell, it interacts with atoms and molecules, causing ionization and excitation. This leads to molecular changes, especially in water and DNA. The biological effects depend on the type of radiation, dose, dose rate, and radiosensitivity of the cell. Review of types of radiation Radiation is classified into two main

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE X-rays production CRT04106 · Radiation Sciences START READING NOTES Study X-rays production using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Learning objectives The concept of atomic orbitals, energy levels and electron shells X-rays production Production of (X) radiation …. Focal spot and Anode angle Anode angle increases the surface area of the focal spot which increases the ability of the anode to absorb heat Types of electron interactions and resulting radiations 1. Characteristic radiation 2. Bremsstrahlung radiation X-ray intensity Intensity (I) of X-rays…. X-Ray Quality Factors that affects the Quantity and quality of X-rays Characteristics of X-rays https://www.youtube.com/watch?v=KEASC8UVAmM X-rays production Learning objectives At the end of this session the student should be able to: Describe the process of x-rays production Explain the general characteristics of X-radiation Describe the types of x-rays Understand the X-ray spectrum X-ray production The concept of atomic orbitals, energy levels and electron shells For the better understanding of X-rays production, it is important to have good knowledge of the atomic structure. In previous session we saw how electrons revolve around the nucleus in their paths called orbits. Possible electron orbits are grouped into different shells. X-rays production Electrons within the same shell have the same quantity of binding energy and the energy decreases with increasing shell number/ energy levels Number of electrons within a shell vary according to the type of shell i.e 2n² Shell number (n) /Quantum number Shell symbol Number of electrons K L M N O P Q Production of (X) radiation Electric current is passed through the tungsten filament and heats it up. As it is heated up the increased energy enables electrons to be released from the filament through thermionic emission. The electrons are attracted towards the positively charged anode and hit the tungsten (W) target (atomic number Z=74) with a maximum energy determined by the tube potential (voltage). NB: The atomic number of target affects both quantity and effective energy (quality) of x-rays X-rays production As the electrons bombard the target they interact via Bremsstrahlung and characteristic interactions which result in the conversion of energy into heat (99%) and x-ray photons (1%). The x-ray photons are released in a beam with a range of energies (x-ray spectrum) out of the window of the tube and form the basis for x-ray image formation. …. Cathode (-) Filament Made of thin (0.2 mm) tungsten wire because tungsten: has a high atomic number (A =184, Z=74) is a good thermionic emitter (good at emitting electrons) can be manufactured into a thin wire has a very high melting temperature (3422°c) Filament is a conducting wire with a high melting point, forming part of a thermionic valve and heated by an electric current …. !The size of the filament relates to the size of the focal spot. Some cathodes have two filaments for broad and fine focusing. Focusing cup Made of molybdenum as: high melting point poor thermionic emitter so electrons aren’t released to interfere with electron beam from filament Negatively charged to focus the electrons towards the anode and stop spatial spreading Focusing cup concentrates the electron beam towards the focal spot of the anode ….. Filament current: The current (usually 10 A) heats up the filament to impart enough energy to the electrons to be released i.e. it affects the number of electrons released. Tube current: This is the flow of electrons to the anode and is usually 0.5 – 1000 mA !It affects the energy and number of electrons released. ….. Anode Target made of tungsten for same reasons as for filament Rhenium added to tungsten to prevent cracking of anode at high temperatures Positively charged to attract electrons Set at angle to direct x-ray photon beam down towards patient. Usual angle is 5° – 15° Rhenium is used in X-ray tubes to improve the strength, toughness, heat resistance, and precision of the target material Focal spot and Anode angle Anode angle increases the surface area of the focal spot which increases the ability of the anode to absorb heat Anode angle causes variation of the beam intensity across the x-ray field Anode angle increases the surface area of the focal spot which increases the ability of the anode to absorb heat Anode angle causes variation of the beam intensity across the x-ray field. Types of electron interactions and resulting radiations At the anode, electrons can interact with the atoms of the anode in several ways to produce x-ray photons. (a)Outer shell interaction: low energy EM released and quickly converted into heat energy (b)Inner shell interaction: This involves K or L shells produces characteristic radiation (useful x-rays) ( c)Nucleus field interaction: Produces Bremsstrahlung radiation 1. Characteristic radiation The characteristic radiation are x-rays produced by interaction of highly energetic incident electrons and the target electrons in the K or L shell. At a specific photoenergy there are peaks where more x-rays are released. These are at the characteristic radiation energies and are different for different materials. Only K-characteristic x-rays are useful for imaging Production of Characteristic x-radiation 2. Bremsstrahlung radiation Bremsstrahlung radiation(German word=slowed down). Generated when a high-speed electron is deflected by the nucleus of a target atom. This deceleration releases energy as X-rays. They represent wide part of the graph in which photons with a range of energies are produced. Bremsstrahlung accounts for the majority of x-ray photon production. The word Bremsstrahlung is retained from the German language to describe the radiation that is emitted when electrons are decelerated Bremsstrahlung radiation X-ray Spectrum Quantity and quality of x-radiation X-ray intensity X-ray intensity (I) refers to the x-ray photon energy passing through a unit area in a unit time. It represents the amount of x-rays coming off the target. The intensity of x-rays depends on the applied tube current (mA) Intensity (I) of X-rays…. Effect of mA and mAs (Tube Current and Time) The product of tube current in milliamperes and exposure time in

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radioactivity and X-ray Interaction with Matter CRT04106 · Radiation Sciences START READING NOTES Study Radioactivity and X-ray Interaction with Matter using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Radioactivity and X-ray Interaction with Matter ✓Compton Scattering • Charge: +2. • Charge: None. Basic Principle Factors Affecting Thermionic Emission • Image Contrast: • Clinical Imaging: Radioactivity and X-ray Interaction with Matter RADIATION SCIENCE CHAPTER 2 Radioactivity Thermionic Emission Photoelectric Effect ✓Compton Scattering Beam Attenuation Half Value Layer X-ray interaction with matter✓Radioactivity Radioactivity is the spontaneous disintegration of unstable atomic nuclei, releasing energy in the form of radiation. It was discovered in 1896 by Henri Becquerel and later studied by Marie and Pierre Curie. Atoms that undergo radioactive decay are called radioisotopes. Causes of Radioactivity Nuclei are radioactive if they are unstable due to: Unfavorable proton-to-neutron ratio. Excess energy within the nucleus.• To achieve stability, these nuclei disintegrate and emit radiation. Types of Radioactive Radiation (a) Alpha (α) Particles Composition: 2 protons + 2 neutrons (Helium nucleus). • Charge: +2. Mass: Heavy. Penetration: Very low (stopped by paper or skin). Effect: Highly ionizing, dangerous if ingested or inhaled.(b) Beta (β) Particles Two types: o β- (electron emission): Neutron → Proton + Electron + Antineutrino. o β+ (positron emission): Proton → Neutron + Positron + Neutrino. Charge: -1 (β-) or +1 (β+). Penetration: Moderate (stopped by aluminum sheet). Effect: Medium ionizing power. (c) Gamma (γ) Rays Composition: Electromagnetic radiation (photons). • Charge: None. Mass: None. Penetration: Very high (needs lead or thick concrete to stop). Effect: Low ionizing but very penetrating.Units of Radioactivity Becquerel (Bq): 1 disintegration per second. Curie (Ci): 3.7 × 10¹⁰ disintegrations per second. Gray (Gy): Unit of absorbed dose (1 Gy = 1 J/kg). Sievert (Sv): Biological effect of absorbed dose (dose equivalent). Detection of Radioactivity Geiger–Müller counter Scintillation counter Cloud chamber Film badges (for monitoring exposure in radiology/medicine) Applications of Radioactivity 1.Medicine o Cancer treatment (radiotherapy, e.g., Cobalt-60). o Diagnostic imaging (PET scan using positron emitters). 2.Industry o Tracers for leaks. o Thickness control in manufacturing. 3.Agricultureo Food preservation (irradiation). o Mutation breeding. 4.Archaeology & Geology o Carbon-14 dating. o Uranium-lead dating of rocks. 5.Energy o Nuclear power generation. Dangers of Radioactivity Causes cell damage, cancer, and mutations. Acute exposure → Radiation sickness (nausea, hair loss, death at high doses). Requires strict safety measures: shielding, monitoring, and controlled exposure✓Thermionic Emission Thermionic emission is the release (emission) of electrons from the surface of a metal when it is heated to a high temperature. At high temperatures, electrons gain sufficient kinetic energy to overcome the work function (the minimum energy required for an electron to escape the metal surface). Basic Principle Metals have free electrons in the conduction band that move randomly.• At ordinary temperatures, these electrons lack enough energy to escape. When heated strongly: o Electrons gain energy from thermal vibrations. o If energy > work function → electrons are emitted from the surface. Factors Affecting Thermionic Emission 1.Temperature – higher temperature increases emission. 2.Work function of material – metals with lower work function emit electrons more easily. 3.Surface condition – impurities or oxides can hinder electron escape. 4.Vacuum condition – prevents electrons from colliding with air molecules.Applications of Thermionic Emission 1.Cathode Ray Tubes (CRT) o Used in old television and oscilloscope screens. o Electrons emitted by heated filament are accelerated and focused to form images. 2.X-ray Tubes o Thermionically emitted electrons from a heated cathode are accelerated to strike a metal target → production of X-rays.3.Vacuum Tubes / Valves o Early amplifiers, rectifiers, and oscillators. 4.Electron Microscopes o Hot filament acts as electron source for imaging. 5.Radio Transmitters o Thermionic valves were used before semiconductor✓X-ray Interaction with Matter X-rays interact with matter in the following five ways: 1.Coherent scattering 2.Compton scattering 3.Photoelectric effect 4.Pair production 5.Photodisintegration. Only Compton scattering and photoelectric effect are important in making an x-ray image (diagnostic radiology). The probability and type of interaction to occur depends on; a)X-ray photon energy b)The atomic number (Z) c)Density of the material. d)Thickness of the material Mechanisms of X-ray Interaction with Matter 1.Coherent (Classical/Rayleigh) Scattering Process: Occurs when a low-energy X-ray photon (<10 keV) interacts with atoms. The photon changes direction but does not lose energy.❖There is no energy transfer and therefore no ionization. Result: Only contributes slightly to image noise, the general graying of an image that reduces image contrast. Significance: Coherent scattering is of little importance (negligible effect) to diagnostic radiology.❖This is because coherent scattering primarily involves low-energy x-rays, which contribute little to the medical image. 2.Compton Scattering Process: In Compton scattering, the incident x-ray photon interacts with an outer-shell electron and ejects it from the atom, thereby ionizing the atom. X-rays at the diagnostic range can undergo Compton scattering but mainly the moderate energy x-rays. Dependence: Probability depends mainly on electron density, not atomic number. Dominates at moderate photon energies (20–150 keV). Significance: Major source of scatter radiation in diagnostic imaging. Reduces image contrast. Primary contributor to radiation dose to staff. 3.Photoelectric Effect Process: An X-ray photon transfers all its energy to a tightly bound inner-shell electron. The electron is ejected (photoelectron). The incident photon is totally absorbed. The vacancy is filled by another electron, releasing characteristic radiation or Auger electron.Significance: Main contributor to image contrast in diagnostic radiology (especially bone vs. soft tissue). Also increases patient dose because energy is absorbed. Most important process in diagnostic radiology. 4.Pair Production Process: Occurs when photon energy > 1.022 MeV. Photon interacts with the nucleus’ electric field and converts into an electron-positron pair. Significance: Not relevant in diagnostic radiology (too high energy). Important in radiation therapy and PET imaging.5.Photodisintegration Process: Occurs at photon energies > 10 MeV. Photon is absorbed by nucleus, causing it to emit a nucleon (proton or neutron). Significance: Only relevant in high-energy radiation therapy.Factors Affecting X-ray Interaction 1.Photon Energy (kVp) Low kVp → More photoelectric effect (high contrast, high dose). High kVp → More