CRT04106 Radiation Sciences

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

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiation Sciences: Fundamental Concepts CRT04106 · Radiation Sciences START READING NOTES Study Radiation Sciences: Fundamental Concepts using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic MEANING OF RADIATION SCIENCES Radiation Sciences: Fundamental Concepts Module Outline Learning objectives. Introduction Nucleus Shell Types of Electrons Atom Key Points MEANING OF RADIATION SCIENCES Medical radiation science is the study and application of radiant energy in the diagnosis, treatment and follow-up care of injuries and disease. The applied medical radiation sciences encompass a number of disciplines, each distinguished by a distinctive combination of the radiation used and the associated advanced technology required to deliver and interpret the effects of the radiation. Is a science that create, disseminate and apply scientific knowledge to improve human health. Radiation Sciences: Fundamental Concepts Some everyday examples are microwaves television, light, and x-rays used to cook food, radio waves for radios and used in medicine. Important factors in this subject are;Radiation,Radioactivity and Ionization. Radiation is the emission of energy traveling in the form of particles or waves in bundles of energy called photons . Module Outline Atomic structure Basic interactions between X-Rays and matter. Classical laws. Electromagnetic Radiations Radiation units and Radiation Protection. Radiation monitoring. Radiobiology. ATOMIC STRUCTURE Learning objectives. By the end of this session students should be able to; Define atom,nucleus and shell. Describe atomic structure and types of electrons. Introduction 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. Atom 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. This is of the same magnitude as the actual (negative) energy of the electron that is released if the electron is freed. 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 Radiation Sciences: Fundamental Concepts 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 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. Atom Isotopes are atoms