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DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiation Sciences 4.2.1 CRT04106 · Radiation Sciences START READING NOTES Study Radiation Sciences 4.2.1 using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Objectives X-RAY TUBE Additional components The function of the X-ray tube is to: Radiation Sciences 4.2.1 TUBE HOUSING Electrical Insulation: Prevents high-voltage electrical leakage. SHIELDING CATHODE Functions: ANODE Materials in Anode: Why Tungsten for Target? TUBE COOLING GENERATION OF X-RAYS Below is a step-by-step explanation of how X-rays are generated: 2. Acceleration of Electrons 3. Electron-Anode Interaction b) Characteristic Radiation 4. X-ray Beam Formation 5. Energy Distribution FACTORS AFFECTING THE QUALITY OF X-RAY GENERATED 1. Tube Voltage (kVp – Kilovoltage Peak) 2. Tube Current (mA – Milliamperage) 3. Exposure Time (s) 4. Filament Temperature 5. Focal Spot Size 6. Target Material (Anode Composition) 7. Anode Angle 8. Anode Rotation Speed (for Rotating Anodes) 9. Filtration 10. Tube Cooling System 11. Beam Collimation and Alignment 12. Vacuum Quality in the Tube PATIENT CONDITION IN DECIDING EXPOSURE TYPE AND DOSE 1. Patient Size and Body Composition Exposure Type: Use low-dose settings to minimize radiation exposure. b) Obese Patients 2. Pathological Conditions COPD (decreased lung density): b) Bone Imaging (e.g., Osteoporosis, Fractures) 3. Age and Sensitivity b) Pregnant Patients 4. Imaging Region and Type of Examination b) Abdominal X-ray c) Extremity X-ray (e.g., hands, feet) 5. Use of Contrast Media RADIATION SCIENCES Objectives At the end of this session students must be able to; Describe X-ray tube, tube housing, shielding, anode, cathode and tube cooling. Describe generation of X-rays and factors affecting its quality. Demonstrate patient condition in deciding exposure type and dose. X-RAY TUBE The X-ray tube is the core component of the X-ray system, where X-rays are generated. It is a vacuum-sealed device that accelerates electrons from the cathode to the anode, producing X-rays through the interaction of electrons with the anode material. X-RAY TUBE The x-ray tube contains two principal elements: Filament (Cathode): boils off electrons Target (Anode): electrons strike to produce x-rays Additional components Expansion bellows (provide space for oil to expand) Tube envelope (evacuated) Tube housing Cooling dielectric oil Rotor Induction stator Tube window: usually made from beryllium, not glass The function of the X-ray tube is to: Provide a beam of X-rays from as near a point source as possible (focus). Dissipate the heat produced effectively to prevent damage to the X-ray tube (approximately 99 per cent of the energy conversions produce heat). Provide a consistent quality (kVp) and quantity (mAs) of radiation Radiation Sciences 4.2.1 Allow X-rays to emerge only from the window (port) of the housing of the tube and exclude emissions from elsewhere in the housing, which is lined with lead sheet. Provide an electrically safe environment for the practitioner. The tube is securely supported, but capable of easy movement into any position and then being maintained in that position. TUBE HOUSING TUBE HOUSING Is the portion of an x-ray system which contains the x-ray tube and/or secondary target. TUBE HOUSING The tube housing encloses the X-ray tube and serves several key functions: Radiation Shielding: Made of lead-lined material to prevent stray X-rays from escaping. Mechanical Protection: Protects the fragile X-ray tube from external damage. Electrical Insulation: Prevents high-voltage electrical leakage. Heat Dissipation: Contains cooling systems to manage heat generated during operation. SHIELDING External Shielding: Lead lining in the tube housing minimizes exposure to stray radiation. Internal Shielding: Filters may be placed to remove low-energy, non-useful X-rays, reducing patient exposure. Collimators: Further limit the beam to the desired area, enhancing safety and image quality. CATHODE The cathode emits electrons through thermionic emission when heated. It consists of: Filament: A coiled wire (usually tungsten) that produces electrons when heated. Focusing Cup: Negatively charged to direct and focus the electron beam toward the anode. Functions: Provides a source of electrons needed for X-ray production. Shapes and focuses the electron stream for efficient X-ray generation. ANODE The anode is the target where high-speed electrons collide, producing X-rays. It can be: Stationary Anode: Used in low-power X-ray systems (e.g., dental X-rays). Rotating Anode: Used in high-power systems for improved heat dissipation. STATIONARY AND ROTATING ANODE Materials in Anode: Tungsten: High atomic number and melting point, making it ideal for X-ray production. Molybdenum or Copper: Sometimes used as a base for the rotating anode. Why Tungsten for Target? Atomic number -Tungsten’s high atomic number, 74, results in high-efficiency x-ray production and in high-energy x-rays. Thermal conductivity -Tungsten has a thermal conductivity nearly equal to that of copper. It is therefore an efficient metal for dissipating the heat produced. High melting point, Any material, if heated sufficiently, will melt and become liquid. Tungsten has a high melting point (3400°C compared with 1100°C for copper) and therefore can stand up under high tube current without pitting or bubbling. Functions: Converts kinetic energy of electrons into X-rays (about 1% efficiency). Dissipates heat generated during the process. TUBE COOLING Cooling is essential due to the immense heat generated during X-ray production. Methods include: Oil Cooling: Oil surrounds the tube to absorb and transfer heat away from the X-ray tube. Air Cooling: Fans circulate air around the housing to dissipate heat. Rotating Anode: Distributes heat over a larger surface area, increasing thermal efficiency. Water Cooling: Used in high-end systems for superior heat removal. GENERATION OF X-RAYS X-rays are produced when high-speed electrons collide with a metal target (anode) in an X-ray tube. The process involves the conversion of kinetic energy of electrons into electromagnetic radiation. Below is a step-by-step explanation of how X-rays are generated: Electron Production (Thermionic Emission) Cathode: The cathode contains a filament (usually tungsten) that is heated by an electrical current. Electron Emission: When heated, the filament releases electrons through thermionic emission, where the thermal energy overcomes the binding energy of electrons. 2. Acceleration of Electrons High Voltage (kVp): A high voltage is applied between the cathode (negative) and anode (positive), creating a strong electric field. Electron Acceleration: The electrons

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiation Propagation In Tissues CRT04106 · Radiation Sciences START READING NOTES Study Radiation Propagation In Tissues using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic RADIATION PROPAGATION IN TISSUES INTRODUCTION Overview of ProcesSES: Fundamentals of Radiation-Tissue Interaction Characteristics of Body Tissues Affecting Radiation Interaction: Composition The interaction of radiation with different tissue types is the basis for creating contrast in medical images. Radiation Absorption Mechanisms of Absorption: Pair Production (High Energy) Factors Influencing Absorption Radiation absorption forms the basis for contrast in X-ray images Radiation Transmission Significance in Imaging: Factors Influencing Transmission Composition of Tissue: Transmission plays a key role in creating contrast in radiographic images. Radiation Scattering Key Types of Scattering: Compton Scattering: Coherent (Rayleigh) Scattering Impact on Medical Imaging: Impact of scattering on Radiation Safety Minimizing Scattering in Imaging: Radiation Reflection Reflection is more significant for non-ionizing radiation, such as ultrasound, where sound waves reflect at tissue interfaces. Mechanism of Reflection: Applications of reflection in Medical Imaging: Reflection in Ionizing Radiation Minimizing Reflection Artifacts: Comparison of Processes Factors Influencing Radiation Propagation Factor RADIATION PROPAGATION IN TISSUES RADIATION SCIENCES INTRODUCTION Radiation propagation in body tissues refers to how radiation interacts with and travels through the body's biological structures. This process is central to understanding how medical imaging and therapeutic techniques work. Overview of ProcesSES: Absorption -Radiation energy is absorbed by tissue, contributing to image contrast in modalities like X-rays and CT. Transmission Radiation passes through tissue without interaction, creating dark areas in images, such as air-filled spaces. Scattering -Radiation is deflected within tissues, which can degrade image quality and increase radiation dose to healthcare workers. Reflection Radiation is redirected at tissue interfaces, more relevant in ultrasound and non-ionizing radiation applications. Fundamentals of Radiation-Tissue Interaction Nature of Ionizing Radiation: -Ionizing radiation includes high-energy particles or waves like X-rays and gamma rays. -These forms of radiation have enough energy to ionize atoms by removing electrons. Characteristics of Body Tissues Affecting Radiation Interaction: Density -Denser tissues, such as bone, absorb more radiation compared to softer tissues like muscle or fat. Atomic Number (Z) -Higher atomic number tissues (e.g., bone with calcium) have a higher likelihood of absorbing radiation via the photoelectric effect. Composition -The chemical and physical makeup of tissues determines how they interact with radiation (e.g., fat vs. water content). The interaction of radiation with different tissue types is the basis for creating contrast in medical images. For instance: Bones (high Z) absorb more radiation, appearing bright on X-rays. Lungs (air-filled) allow more transmission, appearing dark on X-rays Radiation Absorption Radiation absorption refers to the transfer of energy from ionizing radiation (e.g., X-rays, gamma rays) to the atoms or molecules in tissue. This process results in ionization or excitation of atoms, leading to energy deposition in tissue. Mechanisms of Absorption: Photoelectric Effect: -Dominates at lower photon energies and in tissues with higher atomic numbers (e.g., bone). =The photon is completely absorbed, and an electron is ejected from the inner shell of an atom. -This creates image contrast in X-ray and CT imaging. Pair Production (High Energy) -Occurs at very high photon energies (above 1.02 MeV). -Photon energy converts into an electron-positron pair (not common in diagnostic imaging). Factors Influencing Absorption Energy of Radiation: Lower-energy photons are more likely to be absorbed (e.g., photoelectric effect). ii. Tissue Atomic Number (Z): Tissues with higher Z (e.g., calcium in bone) absorb more radiation. iv. Tissue Thickness and Density: Thicker and denser tissues result in greater absorption. The way radiation is absorbed, transmitted, scattered, or reflected depends on tissue characteristics and radiation energy. Radiation absorption forms the basis for contrast in X-ray images -High Absorption Areas (Bright): Bone and calcifications. Low Absorption Areas (Dark): Air-filled structures like lungs. Radiation Transmission Radiation transmission occurs when radiation passes through tissue without interacting with its atoms or molecules. This process allows the radiation to continue its path, reaching the detector or image receptor. Significance in Imaging: -Areas where radiation transmits freely appear darker on imaging modalities like X-rays or CT scans. -Examples: Air-filled structures such as lungs or bowel. Low-density tissues like fat. Factors Influencing Transmission Energy of Radiation: High-energy photons are more likely to transmit through tissues without interaction. Tissue Thickness and Density: Thinner or less dense tissues allow greater transmission. Dense tissues (e.g., bone) block transmission, contributing to image contrast. Composition of Tissue: Tissues with low atomic numbers (e.g., soft tissue) transmit more radiation compared to those with high atomic numbers. Transmission plays a key role in creating contrast in radiographic images. The balance between transmitted and absorbed radiation defines the light and dark regions on the image. Radiation Propagation In Tissues In diagnostic imaging, proper calibration of radiation energy is essential to optimize transmission, ensuring sufficient detail in images while minimizing patient exposure. Excessive transmission through dense tissues can reduce diagnostic value, necessitating adjustments in imaging parameters. Radiation Scattering Radiation scattering occurs when a photon interacts with tissue and is deflected from its original path.This process changes the direction of the radiation without complete absorption. Key Types of Scattering: Compton Scattering Coherent (Rayleigh) Scattering Compton Scattering: Dominates in soft tissues and at medium to high photon energies. A photon interacts with an outer-shell electron, resulting in: Ejection of the electron. Scattered photon with reduced energy. Responsible for image degradation and scatter radiation exposure Coherent (Rayleigh) Scattering -Occurs at low photon energies. -Photon changes direction without energy loss. -Minimal impact on diagnostic imaging Impact on Medical Imaging: Image Quality: Scattered radiation contributes to background "noise," reducing image contrast and detail. Artifacts: Increased scattering can lead to imaging artifacts, especially in thick or dense body regions. Impact of scattering on Radiation Safety Scattered Radiation Exposure: Scattered photons can escape the patient’s body, posing a risk to healthcare workers. This is a major concern in interventional radiology and fluoroscopy Minimizing Scattering in Imaging: Use of Grids: -Grids in X-ray machines filter out scattered photons before they reach the detector. Collimation:

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Quantities Of Dosimetry CRT04106 · Radiation Sciences START READING NOTES Study Quantities Of Dosimetry using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic USE OF RADIATION EFFECT IN BODY TISSUES SKILLS IN DETERMINING EXPOSURES DOSE TO PATIENT (QUANTITIES RELATED TO DOSIMETRY) Quantities Related to Dosimetry E- Mean energy imparted to matter of mass m Apart from Gy, there is another unit of absorbed dose called rad. Imparted energy Equivalent Dose When it comes to the effects of radiation, one can not use absorbed dose as the relevant quantity. Equivalent dose is the product of absorbed dose received by tissue (T) from radiation (R) and radiation weighting factor HT.R s the equivalent dose due to radiation type R, Quantities Of Dosimetry The equivalent doses due to γ-rays and neutrons are given by EFFECTIVE DOSE The tissue weighting factor for stomach is WT = 0.12 as given in Table KERMA USE OF RADIATION EFFECT IN BODY TISSUES SKILLS IN DETERMINING EXPOSURES DOSE TO PATIENT (QUANTITIES RELATED TO DOSIMETRY) RADIATION SCIENCES Quantities Related to Dosimetry Radiation Exposure and Dose Roentgen (R) Absorbed Dose Equivalent Dose Effective Dose Flux or Fluence Rate Integrated Flux or Fluence Kerma, Cema, and Terma ABSORBED DOSE E- Mean energy imparted to matter of mass m Unit: SI unit= Gray 100 rads=1 Gy Old unit=Rads 1 Gy= 1J/kg Apart from Gy, there is another unit of absorbed dose called rad. Even though rad has mostly been replaced by Gy it is still found in some modern literature. Rad was introduced in 1953 to replace Roentgen, which was the unit of exposure due to x-rays or γ-rays only. It is defined as the dose equivalent to the absorption of 0.01 joule of energy per kilogram of tissue Imparted energy It is the total amount of energy deposited in matter It is the product of dose & mass over which the energy is imparted Unit: J Equivalent Dose Absorbed dose is not capable of characterizing the biological effect of radiation Absorbed dose is not capable of characterizing damage to any medium All it tells us is how much energy has been absorbed by the medium and not what this deposited energy has done to the medium For this case of absorbed dose, there is no difference between a photon and an α-particle if they deposit the same amount of energy. When it comes to the effects of radiation, one can not use absorbed dose as the relevant quantity. Since dosimetry is primarily concerned with the safety of personnel, therefore a quantity called equivalent dose has been defined that characterizes the damaging effect of radiation on tissue Equivalent dose is the product of absorbed dose received by tissue (T) from radiation (R) and radiation weighting factor It is denoted by HT.R HT.R= DTR X WR WR= Radiation weighting factor Formely called quality factor basically defines the quality of the radiation that is interacting with the matter Quality of a radiation depends upon two parameters LET & RBE HT.R s the equivalent dose due to radiation type R, DTR is the mean absorbed dose delivered by radiation R, and WR is the radiation weighting factor. The radiation weighting factor is given by WR = QR · NR where QR and NR are the quality and modified factors for the radiation type R respectively Quantities Of Dosimetry In case of mixed field, the total equivalent dose can be obtained by simply summing the contribution due to individual types of radiation, that is HT = R wR · DTR. Quantities Of Dosimetry Example: In a mixed radiation environment, a person receives 20 mGy of γ-ray dose and 2 mGy of slow neutron dose. Calculate the total equivalent dose received by the person. Solution As the source is external, we can take NR = 1 and the weighting factors for the two radiation types as given as wγ = 1 and wn = 5. The equivalent doses due to γ-rays and neutrons are given by HT,γ = wγ · DT,γ = (1)(20) = 20 mSv HT,n = wn · DT,n = (5)(2) = 10 mSv The total dose received by the person is then sum of these individual doses, that is HT = HT,γ + HT,n = 20 + 10 = 30 mSv EFFECTIVE DOSE The equivalent dose as described above can be used for one tissue type only as it does not address the sensitiveness of tissue types to the same type of radiation. The question is, how we can determine the whole body equivalent dose to estimate the risk associated with a certain type of radiation environment?. Or how one can estimate the whole body dose if the dose received by a particular organ is known. This is done by using the quantity effective dose Effective dose Can be defined as the product of equivalent dose and tissue weighting factor Since all tissues doesn’t have the same sensitivity towards radiation, so each tissue is given a factor based on the response to radiation This factor is called tissue weighting factor It is denoted by E E=Sum(HTR X WT) WT= Tissue weighting factor Unit= SI unit= Sievert (Sv) Quantities Of Dosimetry Example: During a CT scan of the stomach, that had to be repeated several times, a patient receives a total absorbed dose of 0.3 Gy. Compute the total effective dose received by the patient. Solution Since CT scan is performed with x-rays therefore the radiation weighting factor WR = 1. The equivalent dose received by the patient’s stomach is HT,R = WR · DT,R = (1)(0.3) = 0.3 Sv The tissue weighting factor for stomach is WT = 0.12 as given in Table The effective dose is then give by E = WT · HT,R = (0.12)(0.3) = 0.036 Sv = 36 mSv. The usual effective dose received during a typical CT scan of abdomen is around 10 mSv, which means that this patient received more

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Factors Affecting Radiation Effect To Cell CRT04106 · Radiation Sciences START READING NOTES Study Factors Affecting Radiation Effect To Cell using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic RADIATION CELL DAMAGE OBJECTIVES INTRODUCTION FACTORS WHICH MODIFY CELL DAMAGE BY RADIATION PHYSICAL FACTORS ii. Relative Biologic Effectiveness Factors Affecting Radiation Effect To Cell iii. Protraction and Fractionation BIOLOGIC FACTORS THAT AFFECT RADIOSENSITIVITY AND CELL DAMAGE Oxygen Effect ii. Age iii. Recovery If a tissue or organ receives a sufficient radiation dose, it responds by shrinking. CHEMICAL FACTORS Radiosensitizers ii. Radioprotectors. iii. Other molecules/water molecules RADIATION CELL DAMAGE RADIATION SCIENCE OBJECTIVES Understand definition of ionzing radiation Identify types radiation Highlight examples of ionizing radiation Explain direct and indirect mechanism of cell damage Understand how physical, chemical and biological factors contribute to cell damage by radiation INTRODUCTION What is ionizing radiation? Types of radiation Examples of ionizing radiation Explain direct and indirect mechanism of cell damage by radiation FACTORS WHICH MODIFY CELL DAMAGE BY RADIATION Physical factors Biological factors Chemical factors PHYSICAL FACTORS Linear energy transfer Relative biological effectiveness Protraction and fractionation PHYSICAL FACTORS LINEAR ENERGY RANSFER -Linear energy transfer (LET) is a measure of the rate at which energy is transferred from ionizing radiation to soft tissue -LET is expressed in units of kiloelectron volt of energy transferred per micrometer of track length in soft tissue (keV/µm). -The ability of ionizing radiation to produce a biologic response increases as the LET of radiation increases. When LET is high, ionizations occur frequently, increasing the probability of interaction with the target molecule The LET of diagnostic x-rays is approximately 3 keV/µm ii. Relative Biologic Effectiveness As the LET of radiation increases, the ability to produce biologic damage also increases. This effect is quantitatively described by the relative biologic effectiveness (RBE) Factors Affecting Radiation Effect To Cell Diagnostic x-rays have an RBE of 1. Whereas radiations with lower LET than diagnostic x-rays have an RBE less than 1, radiations with higher LET have a higher RBE. iii. Protraction and Fractionation -If a dose of radiation is delivered over a long period of time rather than quickly, the effect of that dose is less. -Stated differently, if the time of irradiation is lengthened, a higher dose is required to produce the same effect. This lengthening of time can be accomplished in two ways. If the dose is delivered continuously but at a lower dose rate, it is said to be protracted. Six gray (600 rad) delivered in 3 -minutes at a dose of 2 Gyt/min is lethal for a mouse. However, when 6 Gyt is delivered at the rate of 10 mGyt/hr for a total time of 600 hours, the mouse will survive. Factors Affecting Radiation Effect To Cell If the 6-Gyt dose is delivered at the same dose rate, but in 12 equal fractions of 500 mGyt, all separated by 24 hours, the mouse will survive. In this situation, the dose is said to be fractionated. Radiation dose fractionation reduces effect because cells undergo repair and recovery between doses. Dose fractionation is used routinely in radiation oncology. BIOLOGIC FACTORS THAT AFFECT RADIOSENSITIVITY AND CELL DAMAGE Oxygen effect Age Recovery Oxygen Effect -Tissue is more sensitive to radiation when irradiated in the oxygenated, or aerobic, state than when irradiated under anoxic (without oxygen) or hypoxic (low-oxygen) conditions. -This characteristic of tissue radiation response is called the oxygen effect and is described numerically by the oxygen enhancement ratio (OER). ii. Age -The age of a biologic structure affects its radiosensitivity. -The response of humans is characteristic of this age-related radiosensitivity -Humans are most sensitive before birth. -After birth, sensitivity decreases until maturity, at which time humans are most resistant to radiation effects. In old age, humans again become somewhat more radiosensitive. iii. Recovery -Human cells can recover from radiation damage. -If the radiation dose is not sufficient to kill the cell before its next division (interphase death), then given sufficient time, the cell will recover from the sublethal radiation damage it has sustained. -Some types of cells have greater capacity than others for repair of sublethal damage. -At the whole-body level, this recovery from radiation damage is assisted through repopulation by surviving cells If a tissue or organ receives a sufficient radiation dose, it responds by shrinking. This is called atrophy, and it occurs because some cells die and disintegrate and are carried away as waste products. If a sufficient number of cells sustain only sublethal damage and survive, they may proliferate and repopulate the irradiated tissue or organ CHEMICAL FACTORS Radiosensitizers Radioprotectors Free radicals/other molecules (water molecules) Radiosensitizers -Agents that enhance the effect of radiation are called sensitizing agents. Examples include halogenated pyrimidines, methotrexate, actinomycin D, hydroxyurea, and vitamin K. -The halogenated pyrimidines become incorporated into the DNA of the cell and amplify the effects of radiation on that molecule. All radiosensitizers have an effectiveness ratio of approximately 2, that is, if 90% of a cell culture is killed by 2 Gyt (200 rad), then in the presence of a sensitizing agent, only 1 Gyt (100 rad) is required for the same percentage of lethality ii. Radioprotectors. Radioprotective compounds include molecules that contain a sulfhydryl group (sulfur and hydrogen bound together), such as cysteine and cysteamine. Hundreds of others have been tested and found effective by a factor of approximately 2. For example, if 6 Gyt (600 rad) is a lethal dose to a mouse, then in the presence of a radioprotective agent, 12 Gyt (1200 rad) would be required to produce lethality iii. Other molecules/water molecules -Water molecules act as a medium for radiation-induced free radical generation, amplying damage through indirect mechanism ← 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 Electromagnetic Radiation CRT04106 · Radiation Sciences START READING NOTES Study Electromagnetic Radiation using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Introduction Electromagnetic Waves Sine Wave Electromagnetic Spectrum Visible Radiation Wave-Particle Duality Types of EMR Uses of EMR Visible Light Electromagnetic Radiation Introduction Is the flow of energy at the universal speed of light through free space or through a material medium in the form of the electric and magnetic fields. Visible light is one type of electromagnetic radiation, other familiar forms are invisible electromagnetic radiations such as X-rays and radio waves. EMR consists of electromagnetic waves. Electromagnetic radiation is a type of energy that is all around us and takes many forms, such as radio waves, microwaves, X-rays and gamma-rays. Introduction Electromagnetic Waves Electromagnetic waves are waves oscillations of electric and magnetic fields that propagate at the speed of light. The oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation. The electric and magnetic fields in EMR waves are always in phase and at 90 degrees to each other. Electromagnetic Waves Electromagnetic Waves The electromagnetic radiation are distinguished by frequency and wave length of their electromagnetic wave. Frequency is the number of complete cycles formed by a wave at a period of a second. The SI unit of frequency is Hertz (Hz) but also can be expressed as per second. It is represented Electromagnetic Waves Wave length is the distance cover by a single complete cycle (frequency) of a wave. Wave length is the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings The unit of wave length is Meter (M). Wavelength is represented by lambda. Sine Wave Is a mathematical curve that describes a smooth repetitive oscillation. The sine wave is important in physics because it retains its wave shape when added to another sine wave of the same frequency and arbitrary phase and magnitude. It is the only periodic waveform that has this property. Electromagnetic waves are also a sine wave. Sine Wave Electromagnetic Spectrum Is the range separation of Electromagnetic radiation according to their frequency and wave length. The electromagnetic radiation classified as; radio waves, microwave, infrared rays, visible light, ultraviolet rays, X-rays and gamma rays. Although all electromagnetic waves travel at the speed of light in a vacuum, they do so at a wide range of frequencies, wavelengths, and photon energies. Electromagnetic Spectrum Visible Radiation Light is the most familiar form of electromagnetic radiation and makes up that portion of the spectrum to which the eye is sensitive. The corresponding wavelengths extend from 7 × 10-5 centimeter (red) to 4 × 10-5 centimeter (violet). Why visible radiation is important to our life?. Wave-Particle Duality Wave particle duality is the behavior of electromagnetic radiation that it exhibit both wave like nature and particle like nature. Electromagnetic radiation is usually thought of as being a wave. How is it known that it behaves like a wave? If visible light is considered, it can be demonstrated that visible light can undergo reflection, réfraction, diffraction, interference, etc., all of which are properties of waves. Wave-Particle Duality Particle – like properties Some phenomena associated with electromagnetic radiation, such as the photoelectric effect and Compton scattering, cannot be explained by the wave theory. To explain these phenomena, electromagnetic radiation must be considered to behave as particles or packets of energy rather than as waves. Wave-Particle Duality Wave-Particle Duality Electromagnetic radiation is considered as particle since has mass and carries energy in quanta. Since electromagnetic radiation has mass thus has momentum which can cause ejection of electron in an atom as in photoelectric effect or Compton effect. From quantum physics E = h f……..1 Wave-Particle Duality From Einstein equation of relativity E= mc2…………2 By equating equations 1 and 2 mc2 =hf m=hf/c2 where h is plank’s constant = 6.6×10-34j.s c is speed of light in space =3×108m/s In a unit of kilogram Types of EMR There are two main electromagnetic radiation according to their energy. Ionizing radiation Non- ionizing radiation Ionizing radiation are those radiation with ability to cause ionization of an atom such as X-rays, Gamma rays and Ultra violate radiation. Non-ionizing radiation are those which have no ability to cause ionization of an atom such as radio waves and micro waves. Types of EMR Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atom or molecules. That is, to completely remove an electron from an atom or molecule. Instead this electromagnetic radiation has sufficient energy only for excitation of electrons (the movement of an electron to a higher energy state.) Uses of EMR Some form of electromagnetic radiation are used in medical purpose such us in diagnosis of diseases on human body and also can be used as therapeutically as in radiotherapy. Such electromagnetic radiation include X-rays, visible light and gamma rays. This electromagnetic radiation have low wave length, high frequency and high energy which allows them to pass through human tissues. The tendency of these wave to pass through human tissue, it help us to diagnose different pathological issues in our body. Visible Light This electromagnetic waves have longer wave length, thus does not penetrate through human tissue But it is useful in diagnosis and treatment procedures since it can be used to guide where the x-rays and gamma rays should be exposed during the diagnostic and therapeutic procedures. Uses of EMR ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Dosimetry Principle CRT04106 · Radiation Sciences START READING NOTES Study Dosimetry Principle using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic DOSIMETRY PRINCIPLES IN CALCULATING PATIENT DOSES LEARNING OBJECTIVES Dosimetry DOSIMETER Dosimterer Properties of dosimeters Accuracy and Precision Uncertainty shows the range within which the true value is likely to be, considering errors in the measurement process Characteristics of Dosimeters Ideally, the dosimeter reading M should be linearly proportional to the dosimetric quantity Q. In Fig: Curve A first exhibits linearity with dose, then a supralinear behavior, and finally saturation. Dosimetry Principle Energy response/dependency DIRECTIONAL DEPENDENCE SPATIAL RESOLUTION COMMON DOSIMETERS IONIZATION CHAMBER Types of ionization chamber PARALLEL PLATE CHAMBER (ELECTRON DOSIMETRY) Plane-Parallel Ion Chamber Uses of parallel-plate chamber Extrapolation Chambers How ionization chamber work The movement of these charged particles creates a small electric current that is proportional to the amount of ionizing radiation Function of ionization chamber FILM DOSIMETRY How film dosimeter works Advantages of film dosimeter LUMINESCENCE DOSIMETRY If the exciting agent is light, the phenomena is called OPTICALLY STIMULATED LUMINESCENCE DOSIMETRY (OSD) SEMICONDUCTOR DOSIMETRY HOW SEMICONDUCTOR DIODE WORK TYPES OF SEMICONDUCTOR DOSIMETERS DOSIMETRY PRINCIPLES IN CALCULATING PATIENT DOSES RADIATION SCIENCES LEARNING OBJECTIVES At the end of the session, students should be able to explain: Dosimetry and dosimeter Properties of dosimeters Ionization chamber dosimetry systems Film dosimetry Luminescence dosimetry Semiconductor dosimetry Function of dosimeters Dosimetry Dosimetry is the measurement, calculation and assessment of the ionizing radiation absorbed by an object, usually the human body DOSIMETRY Deals with the measurement of the absorbed dose or dose rate resulting from the interaction of ionizing radiation with matter. -It also refers to the determination of radiologically relevant quantities such as: Exposure Kerma – kinetic energy released in matter Fluence etc DOSIMETER Dosimeter can be defined generally as any device that is capable of providing a reading ‘r’ that is a measure of the absorbed dose ‘D’, deposited in its sensitive volume V by ionizing radiation Dosimterer Dosimeter is a device that measures directly or indirectly Exposure Kerma Absorbed dose Equivalent dose Or other related quantities. The dosimeter along with its reader is referred to as a Dosimetry System. Properties of dosimeters A useful dosimeter exhibits the following properties: High accuracy and precision Linearity of signal with dose over a wide range Dose and dose rate dependence Energy response Small directional dependence High spatial resolution Large dynamic range Accuracy and Precision Accuracy specifies the proximity of the mean value of a measurement to the true value (How a close measurement is to the correct value). Precision specifies the degree of reproducibility of a measurement. The accuracy and precision associated with a measurement is often expressed in terms of its uncertainty. Uncertainty shows the range within which the true value is likely to be, considering errors in the measurement process The standard deviation of the mean value is used to express the uncertainty for the best estimate: Characteristics of Dosimeters Linearity The dosimeter reading should be linearly proportional to the dosimetric quantity. Beyond a certain range, usually there is non linearity. This effect depends on the type of dosimeter. Ideally, the dosimeter reading M should be linearly proportional to the dosimetric quantity Q. However, beyond a certain dose range a non-linearity sets in. The linearity range and the non-linearity behavior depend on the type of dosimeter and its physical characteristics In Fig: Curve A first exhibits linearity with dose, then a supralinear behavior, and finally saturation. Curve B first exhibits linearity and then saturation at high doses In general, a non-linear behavior should be corrected for. A dosimeter and its reader may both exhibit non-linear characteristics, but their combined effect could produce linearity over a wider range Or dose dependence Dosimetry Principle Ideally, the response of a dosimetry system M/Q at two different dose rates ((dQ/dt)1 and (dQ/dt)2) should remain constant. In reality, the dose rate may influence the dosimeter readings and appropriate corrections are necessary, for example: recombination corrections for ionization chambers in pulsed beams Energy response/dependency The response of a dosimetry system M/Q is generally a function of radiation beam quality (energy). Since the dosimetry systems are calibrated at a specified radiation beam quality (or qualities) and used over a much wider energy range, the variation of the response of a dosimetry system with radiation quality (called energy dependence) requires correction. DIRECTIONAL DEPENDENCE The variation in response of a dosimeter with the angle of incidence of radiation is known as the directional, or angular, dependence of the dosimeter. Dosimeters usually exhibit directional dependence, due to their constructional details, physical size and the energy of the incident radiation. Dosimetry Principle Directional dependence is important in certain applications, for example in in vivo dosimetry while using semiconductor dosimeters. Therapy dosimeters are generally used in the same geometry as that in which they are calibrated. SPATIAL RESOLUTION The quantity absorbed dose is a point of quantity Ideal measurement requires a point-like detector Measurement result can be attributed to a point within the volume referred to as the effective point of measurement COMMON DOSIMETERS Ionization chamber Film dosimeter Luminescence dosimeter Semiconductor IONIZATION CHAMBER Are-gas filled spaces between two electrodes, typically parallel plates or a hollow cylinder and a thin wire They operate at a saturation voltage, and the current passing through them can be recorded by a voltmeter Types of ionization chamber Free air ionization chamber Thimble ionization chamber Plane-parallel ionization chamber Well-type chamber Pocket ionization chamber Extrapolation ionization chamber Geiger-Muller counter Proportional counter Ionization Chamber Cylindrical (thimble) ionization chamber Most popular design Independent of radial beam direction Typical volume between 0.05 -1.00 cm3 Typical radius ~2-7 mm Length~ 4-25 mm Thin walls: ~0.1 g/cm2 Used for: electron, photon, proton, or ion beams. Thimble Chamber PARALLEL PLATE CHAMBER (ELECTRON DOSIMETRY) Consist of two plane walls, one serving as an entry window and polarizing electrode and the other as the black wall and collecting electrode, as well as

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Determinants Of Biological Effects CRT04106 · Radiation Sciences START READING NOTES Study Determinants Of Biological Effects using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic DETERMINANTS OF BIOLOGICAL EFFECTS OBJECTIVES Introduction Rate of Absorption -Type of Radiation: Tissue Type: Biological effect Area Exposed When radiation affects the entire body, the consequences are more widespread. Effects of Exposure Area on Biological Effects Variation in Species ii. DNA Repair Mechanisms: iii. Metabolic Rate: iv. Size and Physiology Individual Sensitivity Factors affecting Individual Sensitivity: ii. Age: iii. Sex iv. Pre-existing Health Conditions: v. Lifestyle and Environmental Factors Variation in Cell Sensitivity Key Factors affecting Cell Sensitivity ii. Cell Cycle Phase iii. Cell Differentiation: iv. Oxygen Effect (Oxygen Enhancement Ratio) v. Radiosensitivity: DETERMINANTS OF BIOLOGICAL EFFECTS RADIATION SCIENCE OBJECTIVES Explain determinants of biological effects following radiation exposure Introduction Determinants of Biological Effects refer to the factors that influence the magnitude and nature of the biological changes caused by exposure to physical, chemical, or biological agents. -these determinants describe the variables that affect how living tissues respond to ionizing radiation, ultimately shaping the extent of cellular damage, tissue reactions, and overall health outcomes key determinants that affect biological responses to radiation exposure, Rate of Absorption Area Exposed Variation in Species Individual Sensitivity Variation in Cell Sensitivity Rate of Absorption The rate of absorption refers to the speed at which radiation energy is absorbed by the tissue during exposure. This factor directly influences the intensity and extent of the biological effects. Factors affecting Absorption Rate: Energy of Radiation: Higher energy radiation (e.g., gamma rays, X-rays) tends to penetrate deeper into the body and is absorbed over a larger area. Low-energy radiation (e.g., alpha particles) is absorbed quickly but at shallow depths. -Type of Radiation: Different types of radiation interact with tissues differently. For instance: Alpha particles are heavy and highly charged, thus are absorbed by the outer layers of tissue, causing localized damage. Beta particles can penetrate deeper than alpha particles but are still limited in their range. Gamma rays and X-rays are high-energy and have the ability to penetrate deeper, affecting internal organs and tissues Tissue Type: Tissues have varying degrees of radiation absorption based on their composition: Bone absorbs radiation more efficiently than muscle or fat due to its denser composition. Soft tissues, such as those in organs, absorb radiation more readily than fat, making them more susceptible to damage. Biological effect Faster absorption can lead to more concentrated energy delivery to cells and tissues, increasing the likelihood of damage. Tissues exposed to high-energy radiation may experience deeper and more widespread effects compared to shallow absorption. For example, exposure to high-energy X-rays may cause internal organ damage while alpha radiation exposure results in localized skin burns or lung damage. Area Exposed The area exposed refers to the extent of the body or tissue that is irradiated. This factor significantly influences the biological outcomes of radiation exposure. When radiation affects a specific, smaller area, the biological effects tend to be more concentrated. This may cause localized damage to tissues such as skin, bone, or organs. For instance, localized radiation treatment for cancer aims to target specific tumors, minimizing damage to surrounding tissues When radiation affects the entire body, the consequences are more widespread. Full-body exposure can result in systemic damage, affecting multiple organ systems, which increases the likelihood of severe outcomes like radiation sickness, immune suppression, or even death. Determinants Of Biological Effects In situations where part of the body is exposed (e.g., during medical imaging or radiation therapy), the area of exposure determines the severity of damage to those tissues. For example, a localized exposure to the skin may cause skin burns, while exposure to vital organs (like the lungs or liver) could lead to more severe effects. Effects of Exposure Area on Biological Effects A smaller area of exposure might result in less overall damage but could still cause significant harm in highly sensitive tissues or organs. The larger the exposed area, the greater the potential for widespread cellular damage, especially if vital organs are affected. Variation in Species Different species exhibit varying degrees of sensitivity to radiation due to genetic, physiological, and biochemical differences. Understanding these variations is important for both radiation protection and therapeutic applications. Variation in Species Factors Contributing to Species Variation Genetic Differences: -Species have different genetic makeups, which affect how they respond to radiation at the cellular level. For instance, some species may have more efficient DNA repair mechanisms, which allow them to recover from radiation exposure more effectively than others. ii. DNA Repair Mechanisms: -Species with more efficient DNA repair systems, such as humans, may be able to repair radiation-induced damage more effectively. In contrast, species with less efficient repair systems are more susceptible to long-term effects, such as cancer or genetic mutations. iii. Metabolic Rate: -Organisms with faster metabolic rates tend to process radiation more quickly, which may affect how radiation interacts with their tissues. -For example, rodents have faster metabolism compared to humans, potentially leading to quicker absorption and biological effects. iv. Size and Physiology -Larger organisms, such as humans, may be less sensitive to radiation compared to smaller organisms (e.g., rodents, insects) because the larger body mass can dilute the effects of radiation exposure. -Additionally, different species have varying tissue types and organ sensitivities, influencing radiation effects. Individual Sensitivity Individual sensitivity refers to the variation in how different people respond to radiation exposure. While some individuals may experience minimal effects, others may be more vulnerable to radiation-induced damage due to genetic, biological, or environmental factors. Factors affecting Individual Sensitivity: Genetic Factors: -Individuals with genetic mutations that impair DNA repair mechanisms are more likely to suffer from severe biological effects, including cancer or genetic mutations. -Conditions like Ataxia Telangiectasia or Li-Fraumeni Syndrome make individuals more sensitive to radiation, as these conditions affect the body's ability to repair radiation-induced DNA dam ii. Age: Children and the elderly are

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Control Of Scatter Radiation CRT04106 · Radiation Sciences START READING NOTES Study Control Of Scatter Radiation using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic CONTROL OF SCATTER RADIATION EFFECTS OF SCATTER RADIATION ON IMAGE CONTRAST FACTORS AFFECTING SCATTER RADIATION REDUCTION OF SCATTER RADIATION HOW TO REDUCE OF SCATTER RADIATION FORMED CONTROL (REDUCTION) OF SCATTER REACHING FILM SECONDARY GRID SECONDARY GRID MOVEMENTS Potter Bucky Grid BUCKY ASSEMBLY A BUCKY DIAPHRAGM IS FOUND IN THE FOLLOWING CLASSES OF X-RAY EQUIPMENT TYPES OF GRID MOVEMENT IN GENERAL ARE:- FACTORS AFFECTING GRID SELECTION CONTROL OF SCATTER RADIATION CONTROL OF SCATTER RADIATION Scatter radiation is primarily a product of Compton interaction. X-rays that travel in a different direction after exiting the patient body Number of scattered x-ray quanta striking the detector is often large than number of primary (unscattered) quanta Detector (screen) sensitivity to x-ray scatter has an impact on the image Scatter radiation produces fog on the x-ray film which tends to dull the image. It increases density but reduces contrast on the radiograph. EFFECTS OF SCATTER RADIATION ON IMAGE CONTRAST Contrast is the degree of difference in brightness between areas of an image If you could only capture transmitted, unscattered x-rays, the image would be very sharp The corresponding bone-soft tissue interface, would be very abrupt, and therefore the image contrast would be high FACTORS AFFECTING SCATTER RADIATION KILOVOLTAGE – Wavelength of the primary beam (increased kVp) As x-ray energy increases, the relative number of photons that undergo Compton interaction also increases. Thus increasing Kilovoltage, increases the production of scatter radiation. However, the use of low kV technique would require an increase in mAs, thus increasing patient dose. FIELD SIZE – As field size increases, the production of scatter also increases Area of object irradiation (increased x-ray field size As field size increases, intensity of scatter radiation also increases rapidly. Especially during fluoroscopy FACTORS AFFECTING SCATTER RADIATION PATIENT THICKNESS: – The thicker the part to be examined the higher the production of scatter radiation COMPRESSION BAND:- Since the greater the volume of the tissue irradiated the greater the amount of the scattered radiation produced. The volume of the patient can be reduced by the use of compression band Compression band is a wide cloth band about 20-35cm wide. This reduces the volume irradiated and therefore scatter formed Compression devices therefore; improves spatial resolution by reducing patient thickness and bringing the object closer to the recorder medium . Compression also reduces patient dose and increase contrast resolution FACTORS AFFECTING SCATTER RADIATION OBJECT’S DENSITY AND ATOMIC NUMBER:- The higher the atomic number and density the higher the scatter radiation REDUCTION OF SCATTER RADIATION REDUCTION OF SCATTER RADIATION FALLS INTO TWO GROUPS Reduction of scatter radiation formed Control (reduction) of scatter radiation reaching film HOW TO REDUCE OF SCATTER RADIATION FORMED Use of displacement band to reduce thickness of the part under investigation Lowest possible kVp consistent with adequate penetration of the part in question Use of beam restricting devices:- This limits the field size to smaller area thus the production of scatter radiation also decreases. Smallest possible field size e.g., Beam collimation CONTROL (REDUCTION) OF SCATTER RADIATION REACHING FILM USE OF GRIDS:- Grids absorbs scatter radiation before it reaches the film USE OF AIR-GAP TECHNIQUE:- Gap between the patient and the film decreases the amount of scatter radiation that will reach the film HOW TO REDUCE OF SCATTER RADIATION FORMED LIMITING OF THE PRIMARY BEAM Beam restrictors are devices that limits the field size to a small area of interest. The smaller the area of the patient exposed to radiation the smaller the volume of the tissue irradiated and the smaller the amount of scatter produced TYPES OF BEAM-RESTRICTING DEVICES Aperture Diaphragm Cones or Cylinders :- Cones and diaphragm are metal devices which restrict the size of the x-ray beam Variable aperture collimator HOW TO REDUCE OF SCATTER RADIATION FORMED LIMITING OF THE PRIMARY BEAM APERTURE DIAPHRAGM:- The simplest type of beam restrictor, and is made up of lead or lead-lined metal sheet attached to the x-ray tube head. One diaphragm is used for each articular size of film HOW TO REDUCE OF SCATTER RADIATION FORMED LIMITING OF THE PRIMARY BEAM RADIOGRAPHIC CONES AND CYLINDERS:-These are modifications of the aperture diaphragm. It has an extended metal structure which produces a circular image. Are tapered metal structures which may be fitted to the x-ray tube at the beam’s exit port They are usually manufactured either of the brass or steel and are open at both ends; the end nearest the tube is the apex of the cone while the wide part is directed towards the film Radiographic cones comes in a variety of the sizes which result in different areas of radiation field HOW TO REDUCE OF SCATTER RADIATION FORMED 3). RADIOGRAPHIC DIAPHRAGMS:- Simple tablet of heavy metal has central rectangular aperture of the x-ray beam and can be slotted into a fitting on the tube port TWO TYPES: PLATE DIAPHRAGM LIGHT BEAM DIAPHRAGM PLATE DIAPHRAGM:- Simple metal plate with a hole in it The diameter of the hole determine the field covered at a particular focal film distance HOW TO REDUCE OF SCATTER RADIATION FORMED LIGHT BEAM DIAPHRAGM:- Utilizes lead leaves usually multiplane to collimate the beam of radiation This consists of two pairs of movable leaves of metal usually situated in the x-ray beam Each set of pairs can be moved independently of each other, making it to produce a rectangular of any dimensions within the maximum limits of the housing Movement of leaves is controlled by leaves and knobs The field covered is indicated by light from a high intensity lamp which is focused on to radiolucent mirror ( silvered plastic or aluminium equivalent 0.5mm) which is positioned at an angle of 45 degree to the central ray Because lamp has a short life it operated by a press button, self cancelling switch which

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Body Habitus CRT04106 · Radiation Sciences START READING NOTES Study Body Habitus using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic Body Habitus Body habitus is classified into four general body styles Impact of Radiographic Positioning BODY HABITUS Body Habitus Body Habitus Body habitus is generally defined as the build, physique, and general shape of the human body. The size, dimensions, and shape of the patient’s body impacts positioning of specific regions of the body such as the respiratory, gastrointestinal, and biliary systems. Body habitus is classified into four general body styles Sthenic: Approximately 50% of the population falls into this category. For the purpose of radiographic positioning, sthenic body styles are considered average in shape and internal organ location. Hyposthenic: A thin body style, which is more slender than the sthenic body habitus. Approximately 35% of the population is classified as hyposthenic. Body Habitus Hypersthenic: A massive body style, which has a large and broad frame as compared to the sthenic body habitus. Approximately 5% of the population is classified as hypersthenic ) Asthenic: Approximately 10% of the population is very thin or slender with a long and narrow body build. More slight in stature than even the hyposthenic patient Impact of Radiographic Positioning The technologist must consider the patient’s body habitus and alter centering and image receptor placement accordingly. This is especially a concern during adult chest radiography For the hyposthenic and asthenic patient, the image receptor is placed in portrait (lengthwise) alignment because the lungs are longer than those of the hypersthenic patient. Body Habitus For the hypersthenic patient, the image receptor is placed in landscape (crosswise) alignment because the lungs are shorter in length but broader in width than those of the hyposthenic or asthenic patient. The Image Receptor placement for the sthenic adult patient may be placed portrait or landscape depending on age, height, and even pathology. Other anatomical regions are affected as well by 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 Basic Interactions Between X-Rays And Matter CRT04106 · Radiation Sciences START READING NOTES Study Basic Interactions Between X-Rays And Matter using the sections below. Use the topic navigation to continue through Radiation Sciences. Contents of This Topic BASIC INTERACTIONS BETWEEN X-RAYS AND MATTER INTERACTIONS OF X RAYS WITH MATTER. COHERENT SCATTERING PHOTOELECTRIC EFFECT The amount of energy is characteristic of each element Application of photoelectron to Diagnostic Radiology COMPTON SCATTERING PAIR PRODUCTION AND PHOTODISINTEGRATION PHOTODISINTEGRATION BASIC INTERACTIONS BETWEEN X-RAYS AND MATTER BASIC INTERACTIONS BETWEEN X-RAYS AND MATTER Based on the work of Rutherford and Bohr a simple mode of an atom may be visualized as a massive positively charged nucleus surrounded by electrons in orbits of specific diameter Atoms are bonded to the molecules by electrons in the outermost shell. X-ray photons may interact with either orbital electrons or with the nucleus of atoms but in the diagnostic energy range, the interactions are always with orbital electrons. Only two interactions are important in diagnostic radiology ; the Photoelectric Effect and Compton scattering INTERACTIONS OF X RAYS WITH MATTER. There are five basic ways that an X-ray photon can interact with matter,these are Coherent scattering. Photoelectric effect. Compton scattering. Pair production. Photodisintegration. COHERENT SCATTERING The name coherent scattering is given to that interaction in which radiation undergoes a change in direction without a change in wavelength. The type of interaction between X-rays and matter that does not cause ionization No energy is transferred and no ionization occurs with coherent scattering the only effect is to change the direction of the incident radiation. Only 5% of the radiation that undergoes coherent scattering compared to other basic interactions It produces scattered radiation contributing to film fog but the total quantity is too small to be important in Diagnostic Radiology. figure PHOTOELECTRIC EFFECT The photoelectric effect occurs when an incident photon with little more energy than the binding energy of a k-shell electron encounters one of these electrons and ejects it from its orbit. The photon disappears giving up all its energy to the electrons (Most of the photon’s energy is needed to overcome the binding energy of the electron and the excess gives the electron kinetic energy). The electron which is now free of its energy debt, flies off into space as a photoelectron As an electron drops into the k-shell it gives up energy in the form of an X-ray photon The amount of energy is characteristic of each element The photoelectric effect always yields three end products Negative ion (Photoelectron) characteristic radiation 3 . A positive ion (an atom deficient in one electron) The probability of occurrence 1 . The incident photon must have sufficient energy to overcome the electron’s binding energy. A photoelectric reaction is most likely to occur when the photon energy and electron binding energy are nearly the same. The tighter an electron is bound in its orbit the more likely it is to be involved in a photo-electronic reaction Application of photoelectron to Diagnostic Radiology Positive effect . it produces radiographic images of excellent quality. The quality is good for two reasons the photoelectric effect does not produce scatter radiation -it enhances natural tissue contrast(x-ray image contrast depends on the tissue absorbing more x-rays than other tissue, contrast is greatest when the difference in absorption between adjacent tissues is large) Negative effect From the point of view of patient exposure, the patient receives more radiation from photoelectric reactions than from any other type of interaction. All the energy of the incident photon is absorbed by the patient in the photoelectric reaction (The importance of the photoelectric effect can be minimized by using high energy KVp technique). COMPTON SCATTERING Almost all the scatter radiation that we encounter in diagnostic radiology comes from Compton scattering. An incident photon with relatively high energy strikes a free outer shell electron, ejecting it from its orbit. The photon is deflected by the electron so that it travels In a new direction as scatter radiation The reaction produces an ion pair, a positive atom, and a negative electron which is called a coil electron The probability of a Compton reaction depends on the total number of electrons in an absorber which in turn depends on its density and the number of electron per gram. PAIR PRODUCTION AND PHOTODISINTEGRATION The last two basic interactions, pair production and photodisintegration do not occur in the diagnostic energy range. They have no importance in diagnostic radiology. In Pair production a high-energy photon interacts with the nucleus of an atom, the photon disappears and its energy is converted into matter in the form of two particles ordinary electron A positron with the same mass as an electron but with a positive charge PHOTODISINTEGRATION In the photodisintegration part of the nucleus of an atom is ejected by high-energy photon The ejected portion may be a neutron, a proton, and an alpha particle or cluster of particles. The photon must have sufficient energy to overcome nuclear binding energies of the order of 7-15 MeV. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES