NTA Level 4 Semester One

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Mains Voltage Compensation

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Mains Voltage Compensation CRT04104 · Radiology and Imaging Equipment START READING NOTES Study Mains Voltage Compensation using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. Contents of This Topic MAIN VOLTAGE COMPANSATION Manually adjusted mains voltage compensator Mains Voltage Compensation Automatic adjusted mains voltage compensator LINE DROP COMPENSATOR. MAIN VOLTAGE COMPANSATION Objectives Describe main voltage compensation Explain the factors that lead to main voltage fluctuation Name the components used in main voltage compensation Explain the methods through which main voltage compensation is achieved MAIN VOLTAGE COMPANSATION…… Describe: The manually adjusted mains voltage compensator Automatic mains voltage compensator. Describe the main voltage compensation under the headings: Manual mains voltage compensation Automatic mains voltage compensation MAIN VOLTAGE COMPANSATION…… Describe the effects on the radiograph following the change in compensation devices under the following headings: Tube kilo voltage Tube current The supply of the filament transformer Other components of the x ray set timer, monitors, and relays. MAIN VOLTAGE COMPANSATION The changes that occur in the mains voltage are caused by: Slow changes over a period of time due to differences in demand on the supply at various periods in a day. Rapid changes because some equipment on the line draws a heavy current for short interval. The fall in the main voltage caused by x ray set itself drawing current for radiographic exposure. MAIN VOLTAGE COMPANSATION … The main voltage compensator can not prevent the main voltage changes (above) from taking place. What it can do is to maintain voltage output from the autotransformer of the x ray unit. MAIN VOLTAGE COMPANSATION … This may be manually or automatically adjusted. It acts to maintain a constant volts per turn ration on the autotransformer of the x ray set so that the voltage out put of the autotransformer is not changed by alteration in the input voltage. It compensates for slow voltage changes occurring outside the x ray exposure Manually adjusted mains voltage compensator Consist of tappings on the autotransformer at one end of the winding. The tappings can be on either primary side or on the secondary side. There is also a line voltage compensator meter which is connected across a fixed number of tappings of the autotransformer. It is main function is to indicate any change in the main voltage supply. Mains Voltage Compensation For any change in main voltage supply, the main voltage compensator is manually adjusted by the radiographer whether to increase or decrease the number of turns. ( towards A or towards C) Automatic adjusted mains voltage compensator This type of compensator has an adjustor with special contactor called a sledge which is driven by an electric motor to obtain a constantly balanced output voltage from the autotransformer. LINE DROP COMPENSATOR. This is a special transformer in series with the autotransformer. It functions to provide a voltage to superimpose on the line voltage in such a way that the extra voltage is matched to the fall in the line voltage which occurs when the load current flows against mains resistance. This compensator compensates only for the mains drop caused by the x ray set itself ← 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

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Radiology Equipment: Operating Principles

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Radiology Equipment: Operating Principles CRT04104 · Radiology and Imaging Equipment START READING NOTES Study Radiology Equipment: Operating Principles using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. Contents of This Topic OBJECTIVES Determine care of different radiology and imaging equipment. Understand operation of fluoroscopic machine to examine patient. INTRODUCTION X RAY IMAGING Radiology Equipment: Operating Principles Origin of X-ray Source remains same for all x-ray imaging devices Bone APPLICATION OF X RAY Advantage of x ray imaging ULTRASOUND IMAGING IMAGE FORMATION IN ULTRASOUND APPLICATION OF ULTRASOUND Advantage of ultrasound 2. Non-invasive Approach 3. PAINLESS 4. NO RECOVERY TIME 5. COST SOFT TISSUE DETAILS DIFFERENCE BETWEEN X RAY AND ULTRASOUND FLUOROSCOPY X RAY MACHINE Fluoroscopy Mammography A) Dental (Intra-oral x-ray examination) CT SCAN Bone Mineral Densitometry Equipment RADIOLOGY AND IMAGING EQUIPMENT OBJECTIVES Expected learning outcomes: At the end of the course/module students will be able to: Identify different radiology and imaging modalities. Component of convectional x ray and their functions Describe component and functions of dental equipment Determine care of different radiology and imaging equipment. Identify accessories for radiological investigations To understand operation of x ray machine to examine patients To understand operation of dental x ray machine to examine patient. Understand operation of fluoroscopic machine to examine patient. Understand conducting quality control procedures for x ray machine. Understand conducting of basic quality control procedures for dental x ray machine. To maintain record events of all equipment for maintenance and servicing. INTRODUCTION Medical imaging plays a crucial role in diagnosing and monitoring a wide range of medical conditions. Among the most common imaging techniques are X-ray, ultrasound, CT scan MRI, and radionuclide scan X ray modality can be classified into Dental x ray Mammography Fluoroscopy x ray machine X RAY IMAGING X-ray imaging, uses ionizing radiation to produce detailed images of the body's interior. X-ray Machine: A machine emits a controlled amount of X-ray radiation through the body. Absorption: Dense structures, like bones and tumors, absorb more X-rays, resulting in white areas on the X-ray image. Image Capture: X-rays that pass through the body are captured on a detector, creating an image. Radiology Equipment: Operating Principles Medical imaging of the human body requires some form of energy (radiation). In imaging techniques used in radiology, the energy used to produce the image must be capable of penetrating tissues. In diagnostic X-ray imaging, images are formed by the interaction of the X-ray beam with the patient. As the X-ray beam passes through the patient, the photons interact with the body tissues and are absorbed/scattered by the patient. The degree of absorption is related to the density of the material that is in the beam’s path. Dense objects (such as bone and metal) have a high degree of photon absorption, while less dense objects (such as fat and water) absorbs less photons. The differential absorption of photons by different materials in the photons' path results in the beam exiting the patient with different intensities. This is known as transmitted beam. A detector is used to measure the intensity variation, thus providing information on the different densities in the beam’s path. Origin of X-ray Source remains same for all x-ray imaging devices i.e X-ray tube Evacuated glass tube Target Filament Radiology Equipment: Operating Principles Radiography X-ray equipment has an x-ray tube on one side and an x-ray detector on the other side of the patient. A short duration pulse of x-rays is emitted by the x-ray tube, a large fraction of the x- rays interacts in the patient, some of the x-rays pass through the patient (transmitted x-rays) and reach the detector. These transmitted x-rays form the radiographic image on the film/detector. In radiography, the image is formed with screen-film system, CR cassette or with digital detectors. In screen-film radiography, areas of high intensity (thus low material absorption) within transmitted beam result in more blackening of the film, while areas of low intensity (thus high material absorption) will result in less blackening of the film. The film will remain white in areas with no photons. Human body is made up of tissues with varying densities, in the film black corresponds to tissues with little attenuation (such as air) and white corresponds to tissue with a high degree of attenuation (such as bone). Bone Air Soft tissue X Primary collimation Film, fluorescent screen or image intensifier Beam intensity at detector level « Latent » radiological Image formed Antiscatter Grid Scattered radiation X-ray Image Formation APPLICATION OF X RAY Orthopedics: X-rays are commonly used to detect fractures, bone diseases, and joint problems. Dental: Dental X-rays are essential for diagnosing oral health issues. Chest Imaging: It helps diagnose lung conditions like pneumonia and lung cancer. Mammography: X-ray mammography is used for breast cancer screening. Advantage of x ray imaging noninvasively and painlessly help to diagnose disease and monitor therapy; support medical and surgical treatment planning; and Guide medical personnel as they insert catheters, stents, or other devices inside the body, treat tumors, or remove blood clots or other blockages ULTRASOUND IMAGING Ultrasound imaging, also known as sonography, relies on sound waves to create real-time images of the body's internal structures. IMAGE FORMATION IN ULTRASOUND Sound Waves: A small handheld device called a transducer emits high-frequency sound waves into the body. Reflection: When these sound waves encounter different tissues and organs, they bounce back (reflect) at varying speeds depending on the density of the tissues. Image Formation: The transducer collects the reflected waves and sends them to a computer, which processes the data to create dynamic images on a screen APPLICATION OF ULTRASOUND Obstetrics: Ultrasound is commonly used during pregnancy to monitor fetal development. Abdominal Imaging: It helps diagnose conditions in the liver, gallbladder, pancreas, and other abdominal organs. Cardiac Imaging: Echocardiograms use ultrasound to assess heart function. Musculoskeletal Imaging: It aids in diagnosing soft tissue injuries and joint conditions. Small parts imaging: it helps diagnose conditions of the breast, scrotum, neck and

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Rectification 2Nd Module

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Rectification 2Nd Module CRT04104 · Radiology and Imaging Equipment START READING NOTES Study Rectification 2Nd Module using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. Contents of This Topic Voltage Rectification RECTIFICATION Self Rectified Circuit Self-rectification Disadvantages Halfwave Rectifier Circuit Halfwave Rectified Circuit Fullwave Rectifier Full-Wave Rectification Pulsed Radiation Three-Phase Generators Ripple Ripple Example Ripple Typical Values Wave Forms of Different Generator Types Filament Transformer Step-up Transformer Autotransformer RECTIFICATION OF HIGH TENSION Voltage Rectification Transformers operate with alternating current. X-ray tubes operate on direct voltage ( electron moving in one direction). To convert AC to DC we use rectifiers. RECTIFICATION changing alternating current into direct current. The device used is called a rectifier. A symbol for rectifier RECTIFICATION … Methods of rectification Self rectification Half wave rectification Full wave rectification Three phase full wave rectification Self Rectified Circuit Secondary of High Voltage Transformer mA waveform The x ray tube is direct connected to secondary winding of the high tension transformer. X-Ray tube acts as rectifier Current only flows from cathode to anode cathode is source of free electrons Rarely seen Voltage applied to tube Self-rectification Disadvantages hot anode can emit electrons accelerate & can destroy filament half of electrical cycle wasted Voltage applied to x-ray tube mA waveform Used Wasted X-Rays Produced Halfwave Rectifier Circuit + X-ray tube connected to secondary of high voltage transformer through diode rectifiers Alternating voltage applied to secondary of high voltage transformer Voltage applied to tube Halfwave Rectifier Circuit + X Second Half Cycle: Diodes open No voltage applied to tube No tube current (mA) + First Half Cycle: Diodes closed Voltage applied to tube Tube current (mA) results – Halfwave Rectified Circuit Secondary of High Voltage Transformer 60 pulses per second only positive half cycle of high tension transformer used inefficient negative half cycle wasted Blocked (not used) Applied to x-ray tube Output of High Tension Transformer Applied to X-ray Tube Fullwave Rectifier Four diodes 120 pulses/second exposure times half of halfwave circuit Secondary of High Voltage Transformer Voltage applied to tube (also mA waveform) Fullwave Rectifier + X First Half Cycle Second Half Cycle Voltage applied to tube (also mA waveform) X + Full-Wave Rectification Rectifiers Four diode “bridge” configuration used with single phase both + & – half cycle of high tension transformer used efficient circuit reverses negative half cycle & applies to x-ray tube Applied to X-ray Tube Output of High Tension Transformer Tube Pulsed Radiation single phase input power results in pulsed radiation Disadvantages inefficiency of radiation production due to the pulsating waveform not providing enough voltage to produce x-rays for a portion of the time. the inability to select short exposure times. Applied to X-ray Tube Radiation Waveform Three-Phase Generators Commercial power generally delivered as 3 phase phases 120o apart Single Phase Power Three Phase Power Three-Phase Generators Rectifier circuit Inverts negative voltage sends highest of 3 phases to x-ray tube To X-Ray Tube Input 3 Phase Voltage Rectified Three-Phase Generators much higher tube ratings than single phase more efficient than single phase shorter exposures lower exposure Three Phase Output Single Phase Power Ripple variation of kilovoltage from maximum usually expressed as percentage of maximum kV Ripple Ripple Example Ripple = 80 – 72 = 8 kVp OR 8 / 80 = .1 = 10% 80 kVp 72 kVp Ripple Typical Values single phase always 100 % (kV ranges from zero to maximum) three phase 4-13% constant potential 0 % Medium / high frequency very low; approx 0. Three Phase Output Single Phase Output Constant Potential or High Frequency Output Wave Forms of Different Generator Types As the ripple effect decreases, the efficiency increases. There is one more type of generator. It uses is called stored energy. The X-ray Circuit Filament Transformer Intended to lower voltage and increase current Allows for thermionic emission to occur at the filament Ultimately, provides the electrons necessary for x-ray production. Tube current measured in mA. Step-up Transformer This transformer is responsible for producing the high voltages necessary for x-ray production. Turns ratio of 500:1 or 1000:1 Autotransformer The autotransformer works on the principle of self-induction. It has a single core and is responsible for varying the voltage. Because of its ability to adjust voltage, the autotransformer can be either a step-up or step-down transformer. ← 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

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Rectifiers

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Rectifiers CRT04104 · Radiology and Imaging Equipment START READING NOTES Study Rectifiers using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. Contents of This Topic RECTIFERS SOLID-STATE RECTIFIER OR SEMI-CONDUCTORS HOW P-Type Silicon is created N Type Semiconductors Junction Barrier FORWARD BIAS. The positive and negative terminals of the bias battery are connected to P-type and N-type respectively Neutralizing ions on both sides of the barrier, decreases its width. REVERSE BIAS Rectifiers a) The collector is connected to high negative voltage with respect to base i.e. Vbc is very high. So the holes in emitter layer are attracted by negative terminal of Vbe and thus, they cannot cross the junction. NPN JUNCTIONS Note the following important points:- Emitter layer is heavily doped. It has largest number of charges (electrons). Forward Biasing Hence, we conclude that collector current (Ic) is the function of base current ADVANTAGE OF SOLD STATE HIGH TENSION RECTIFIERS OVER THERMIONIC DIODE VALVES RECTIFERS Thermionic diode valves Earlier rectifiers used Consists two electrodes and a glass envelope enclosing a vacuum Passes current through a vacuum in one direction and blocks any reverse flow Sold state rectifiers (semi conductors) Are modern rectifiers to thermionic diode valves Passes electrons through sold material as opposite to vacuum. SOLID-STATE RECTIFIER OR SEMI-CONDUCTORS SOLID- STATE RECTIFIER: Is a solid – state device that serves as an electronic rectifying element. It is made of a combination of P-Type layer and N-Type layer. HOW P-Type Silicon is created To make P-Type silicon, trivalent impurities such as Boron, Indium, Aluminum and Gallium are added or mixed with Silicon (Si). Covalent bond occurs between Silicon and the trivalent atoms. In process of bonding, a vacant hole is created within the covalent bond between one trivalent atom and a neighboring Silicon (Si) atom. The holes are considered to be positive charge carriers. Graphic Representation of P-Type silicon mixed with Boron. N Type Semiconductors If Pentavalent impurities such as phosphorus, arsenic, antimony, and bismuth is added to Silicon (Si) Valence electrons of phosphorus are locked up in covalent bond with valence electrons of four neighboring Silicon (Si) atoms The 5th valence electron of phosphorus atom does not find a binding electron and thus remains free to float. Junction Barrier When p-type and N-type are joined together, the electrons in the N material diffuse across the junction into the P material and fill some of the holes. At the same time, the holes in the P material diffuse across the junction into the N material and are filled by N material electrons. The loss of an electron from the N-type material created a positive ion in the N material, while the loss of a hole from the P material created a negative ion in that material. FORWARD BIAS. If an external voltage applied to a PN junction is call BIAS. A battery is used to supply bias to a PN junction and is connected so that its voltage opposes the junction field, it will reduce the junction barrier and, therefore, aid current flow through the junction. This type of bias is known as forward bias, and it causes the junction to offer only minimum resistance to the flow of current The positive and negative terminals of the bias battery are connected to P-type and N-type respectively The positive potential repels holes toward the junction where they neutralize some of the negative ions The negative potential repels electrons toward the junction where they neutralize some of the positive ions. Neutralizing ions on both sides of the barrier, decreases its width. This allows flow of electrons across the junction. REVERSE BIAS The negative battery terminal is connected to the P-type material. The positive battery terminal to the N-type material The negative potential attracts the holes away from the edge of the junction barrier on the P side. The positive potential attracts the electrons away from the edge of the barrier on the N side. Rectifiers This action increases the barrier width because there are more negative ions on the P side of the junction, and more positive ions on the N side of the junction. This increase in the number of ions prevents current flow across the junction PNP JUNCTIONS FORWARD BIAS a) The collector is connected to high negative voltage with respect to base i.e. Vbc is very high. So c-b junction is reverse biased. The base is connected to low negative voltage with respect to emitter i.e. Veb is low. Also Vbc is always greater than Veb. When Veb is greater than or equal to potential barrier voltage of e-b junction, the transistor is forward biased. Rectifiers Now large number of holes in emitter layer is repelled by positive terminal of Veb and they flow towards e-b junction. They cross the junction and enter into small base layer. Here some electrons combine with holes, some of them are attracted by negative terminal of Veb and remaining large number of holes flow into collector layer, crossing b-c junction. The resident holes of collector are repelled by these (guest) holes and thus, all the holes are attracted by negative terminal of Vbc Rectifiers Thus, all these holes complete their journey back into emitter layer and thus, produce currents in the transistor as shown in the above circuit. Reverse bias a)The collector is connected to high negative voltage with respect to base i.e. Vbc is very high. So b-c junction is reverse biased. The base is connected to low positive voltage with respect to emitter i.e. Vbe is low. Also Vbc is always greater than (–Veb)*. Since battery Vbe is connected in opposite direction, the emitter-base junction is now reverse biased. So the holes in emitter layer are attracted by negative terminal of Vbe and thus, they cannot cross the junction. So there are no holes that can produce base current. Ib = 0. So collector current Ic = 0 and emitter current Ie = 0. Rectifiers

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

The high tension source

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE The high tension source CRT04104 · Radiology and Imaging Equipment START READING NOTES Study The high tension source using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. Contents of This Topic COMPONENTS AND CONTROL IN X RAY CIRCUIT The x-ray tube circuit comprises the following components and controls:- The high tension source: CONTRUCTION OF A TRANSFORMER For an ideal transformer the induced voltage in each turn is the same. On combining the two equations we get:- WINDINGS Step-down transformer AUTO TRANSFORMER There is only one winding Filament Circuit The components in the filament circuit The Autotransformer; Contains an iron core and a single winding or wire, supplies power to the filament transformer. Filament Transformer mA selector The voltage stabilizer: Absorbs or cancels out any voltage fluctuation which may occur in the filament circuit. Control COMPONENTS AND CONTROL IN X RAY CIRCUIT 15-Nov-17 The x-ray tube circuit comprises the following components and controls:- The high tension source The kilo voltage control Filament circuit and milliamperage control Timer The mains supply, and The x-ray tube as shown in the diagram below The high tension source: The source of high voltage which is used to drive electrons fast across an x-ray tube is a high tension transformer. The high tension transformer transforms the voltage of the main supply up to the range of voltage from about 20,000 to 100,000 volts (20kV to 100kV). The function of high tension transformer is to transform the voltage from the main supply up to thousands of volts required to operate the x-ray tube. (step up transformer) The high tension source: Grounded metal box filled with oil electrical insulator Also contains rectifier circuit changes alternating current into direct current CONTRUCTION OF A TRANSFORMER Materials used are soft ion and copper wires. The soft ion core is wound with copper wire on it as indicated on the diagrams below:- The high tension source The step-up transformer has many numbers of turns in the secondary winding compared to the primary winding, while the step-down transformer has less number of turns on the secondary winding. For an ideal transformer the induced voltage in each turn is the same. Therefore the total primary voltage is the voltage in each turn multiplied by the number of turns. Thus: Vp = V x Np or Vp/Np = V Similarly for the secondary: Vs = V x Ns or Vs/Ns = V On combining the two equations we get:- Vp /Np = Vs/Ns By cross multiplication we get: Vs/Vp = Ns/Np WINDINGS The primary winding receives electricity from the mains supply. It has few number of turn compared to the secondary winding. It is shorter and thicker because carries very high current (it may be 200 Amps). The secondary winding supplies kilovoltage and mill amperes for the x-ray tube. Supplies power in form of low current at very high voltage. This is the reason to why it is made of thin wire. It is long compared to the primary winding. Step-down transformer This is a type of transformer steps down high volts to low volts e.g. the filament transformer. It steps down the mains voltage which used by the filament. This type of transformer has few number of turn on the secondary winding. AUTO TRANSFORMER Is the type of transformer which has one winding wound around a soft iron core. There is only one winding The primary and secondary circuits are in metallic connection with each other. This fact makes an auto transformer unsuitable for transforming high voltages from one value to another or for stepping up voltages to high values. Filament Circuit The circuit which supplies power to the filament of the x-ray tube X RAY TUBE FILAMENT CIRCUIT The components in the filament circuit An autotransformer mA Selector Filament transformer Voltage stabilizer Frequency compositor The Autotransformer; Contains an iron core and a single winding or wire, supplies power to the filament transformer. The step-down transformer; Decreases voltage from primary to the secondary coil and increases current in the same proportion. Has more turns in the primary than in the secondary coil. Used in the filament portion to increase current flow to the cathode. Filament Transformer Intended to lower voltage and increase current Allows for thermionic emission to occur at the filament Ultimately, provides the electrons necessary for x-ray production. Tube current measured in mA. The high tension source The mA selector: Used for selecting the amount of current flowing in the filament circuit by varying resistors. The amount of filament current determines how hot the filament wire gets.(More current more heat more electrons boiled off the filament wire Higher mA). mA selector Allows for adjusting of the filament current Precision resistors The voltage stabilizer: Absorbs or cancels out any voltage fluctuation which may occur in the filament circuit. It receives voltage from the autotransformer and supplies to the mill ampere selector. The space charge compensator: Compensates any selected low kilo voltage which will be less able to attract electrons out of the space charge The mA meter: Indicates the tube current Control Factor Electrical Device and Location in Circuit kVp Selection kVp Level Autotransformer (between incoming line and exposure switch) mA Selection Filament Current Variable resistor (in filament circuit between incoming line and step-down transformer) Time Selection Length of exposure Timer circuit (between exposure switch and step-up transformer) Rotor Switch Speed of rotating anode Stator (separate circuit from stator of anode motor) Exposure Switch Moment of exposure Switch (between autotransformer and timer circuit) Filament Circuit ← 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

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

What are the component of Conventional x ray machine

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE What are the component of Conventional x ray machine CRT04104 · Radiology and Imaging Equipment START READING NOTES Study What are the component of Conventional x ray machine using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. Here are the key components of a conventional X-ray machine and their functions: X-ray Tube: Function: This is the heart of the machine. It generates X-rays by accelerating electrons from the cathode to the anode. High Voltage Generator: Function: Provides the extremely high voltage (typically tens to hundreds of kilovolts) needed to accelerate the electrons within the X-ray tube. Control Panel: Function: Allows the radiographer to adjust settings like: Kilovoltage Peak (kVp): Controls the energy and penetrating power of the X-rays. Milliamperage (mA): Controls the number of electrons flowing from the cathode, influencing the X-ray beam's intensity. Exposure Time: Determines how long the X-ray beam is produced. Collimator: Function: Restricts the size and shape of the X-ray beam, minimizing the area of the patient exposed to radiation. This reduces scatter radiation and improves image quality. Patient Table: Function: Supports the patient during the examination. It can be adjusted to various positions (e.g., upright, tilted) to obtain the desired image. Image Receptor: Function: Captures the X-ray image. This could be: Traditional X-ray film: (older technology) Digital detectors: (more modern, allowing for faster image acquisition and processing) Cooling System: Function: The X-ray tube generates a significant amount of heat during operation. The cooling system (often involving oil circulation) helps to dissipate this heat and prevent damage to the tube. Let me know if you'd like a more detailed explanation of any of these components! ← 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

CRT04104 Radiology and Imaging Equipment, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

X-ray Tube Stand

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE X-ray Tube Stand CRT04104 · Radiology and Imaging Equipment START READING NOTES Study X-ray Tube Stand using the sections below. Use the topic navigation to continue through Radiology and Imaging Equipment. X-RAY TUBE STAND It is part of the x ray set which support the x ray tube so that it can be applied for radiological examinations TYPES OF TUBE STAND Floor x ray tube stand Floor to wall x ray tube stand Ceiling x ray tube stand Ceiling rails REQUEREMENTS OF X RAY TUBE STAND The x ray tube support should be adequately rigid so that vibration of x ray tube is avoided. All movements of the support and x ray tube about it should be smooth, unrestricted and easy to perform. It must be possible to make certain precise angulations of the x ray tube It must be possible to direct the x ray tube parallel to the floor as well as in a perpendicular direction The controls providing for the tube movements should be easily readily accessible. X-RAY TUBE STAND The x ray tube stand consists of a column of heavy gauge steel which is amounted on a carriage for movements between tracks on the floor and ceiling On the vertical column a cross- arm supports the x ray tube. The cross- arm can be moved up and down the column, at right angle to the column, and in the rotational motion about the vertical axis of the column. X-RAY TUBE STAND The x ray tube can be rotated up on the cross-arm and can be tilted about an axis parallel to itself. These movements made for the following excursion of x ray tube Longitudinal travel ( parallel to the x ray tube) Horizontal travel at right angle Vertical travel and down the column Rotation travel about the vertical column Rotation on an axis parallel to the cross- arm of 180 degree to 180 degree Rotation round the tube’s own long axis. ← PREVIOUS TOPICVIEW 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

CRT04105 Radiographic Imaging Sciences, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Chapter 1 Intro to Imaging Sciences

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Chapter 1 Intro to Imaging Sciences CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Chapter 1 Intro to Imaging Sciences using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Chapter 1 Intro to Imaging Sciences RADIOGRAPHIC IMAGING SCIENCES Introduction to Radiographic and Imaging Sciences What is an image? An image is a recognizable pattern carrying useful information. An images can be; Real images; those having a real, physical existence e.g. photographic and radiographic images (x-ray images). Mental image; those generated as mental pictures. Production of an x-ray image Production of a radiograph (x-ray image on a film) involves three stages; The formation of an invisible x-ray image (latent image) The conversion of the invisible x-ray image into a visible light image. ‒ This is done through chemical processing of the film. The viewing, perception and interpretation of the visible image. ‒ This is done by the aid of a lightbox. How is an image recorded on a film? The traditional way in which x-rays images are recorded is by using photographic effect of X-radiation on sensitive emulsion.What is photographic effect? Photographic effect refers to the structural changes of some chemical compounds when they are exposed to electromagnetic radiation. The electromagnetic radiation can be visible light, ultraviolet light or x-rays. These chemical changes are usually invisible but they are made visible through chemical processing. NB; Photographic development; is the chemical processing necessary to make the invisible changes visible on a photosensitive material.What is a photosensitive material? Photosensitive material refers to any material which undergoes chemical changes when exposed to electromagnetic radiation. The photosensitive materials used in radiography are known as silver halides. Silver Halides The silver halides are a group of chemical compounds consisting of atoms of the element silver combined with atoms of the halogen elements; bromine, iodine and chlorine. The compounds thus formed are silver bromide, silver iodide and silver chloride respectively. These compounds are used because they are sensitive to light and x-rays. When they are exposed to radiations they undergo changes which enable them to form a photographic or radiographic image. Physical properties of silver halides They are white or pale yellow crystalline salts similar in appearance to common salt. The links between silver and halogen atoms are ionic bonds. NB; Ionic bonds occur when positive (+) and negative (-) ions are locked together by electric forces. In silver halides, the silver ions are positively charged (+) and the halide ions are negatively charged (-).The electric forces fix the positions of silver and halide ions in a regular three dimensional crystal structure or lattice.Chemical properties of silver halides Pure silver halide crystals are chemically stable and do not easily suffer chemical breakdown. Under certain conditions, it is possible to neutralize all the positively charged silver ions in a crystal and convert them to atoms of metallic silver. This conversion is achieved by donating –vely charged electrons to the silver ions. A chemical which provide a supply electrons for this purpose is called a reducing agent. NB; A reducing agent; is a chemical which provides a supply of electrons in order to reduce silver halide to metallic silver. The chemical reduction of a silver halide sample which has been exposed to radiation takes place much more rapidly (because of weakened bonds) than the reduction of an unexposed sample.NB; In photographic development, what actually takes place is chemical reduction of silver halide to metallic silver. ⸫ Photographic development is primarily a process of chemical reduction. What happens when a silver halide is irradiated? Invisible structural changes occur in silver halide crystals when exposed to radiation. The following image shows a regular arrangement of silver and bromine ions in a crystal. What is a sensitivity speck? A sensitivity speck refers to a low energy electron trap in a silver halide crystal. It is where electrons collect after exposing the halide crystal to radiation. NB; Sensitivity specks are formed by deliberate introduction of ‘impurities’ into the crystal during its manufacture. What is a latent image? A latent image is an invisible image formed on a film after exposure to radiation. A latent image is later made visible through photographic development. In a latent image, very few exposed silver halide crystals have been completely reduced to metallic silver. To complete the process, photographic development is required. Only after completing this process can the image become visible. Differences between silver halides and metallic silver NB; the conversion from silver halide to metallic silver in exposed part is important because the two substances have different properties; Silver halides are sensitive to light while metallic silver is not. Metallic silver is opaque to light and is seen as a darkened area. The blackened parts of a radiographic image are due to metallic silver. Silver halides can be converted into soluble compounds by the action of chemicals known as fixing agents. NB; an image which contains silver halide can undergo changes whenever exposed hence it cannot be a permanent image. An image formed only by metallic silver cannot undergo any changes even when exposed again hence it is a permanent image. Light sensitive and X-ray sensitive films Light sensitive films are films in which production of an image is through exposure to visible light. X-ray sensitive films are films in which production of an image is through exposure to x-rays. NEXT 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

CRT04105 Radiographic Imaging Sciences, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Chapter 2 Film construction

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Chapter 2 Film construction CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Chapter 2 Film construction using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Chapter 2 Film construction RADIOGRAPHIC IMAGING SCIENCES FILM CONSTRUCTION A film; is a special sheet used to display a radiographic image. There are two main groups of films Direct exposure films (x-ray films) Light only films Direct exposure films; these are films exposed to x-rays alone or to a combination of both x-rays and light. e.g. intra-oral films dental films and radiation monitoring film Light only films; these are films which are sensitive to light only. A film is a made up of several layers as shown below. (i)Film base; made up of cellulose triacetate or polyester. Polyester being the most common. Functions of film base Provides support and stability to emulsion layer Transmits light so that the image can be viewed. Desirable characteristics of film base Transparent and free of any defect Strong but flexible. Uniform in thickness Dimensionally stable throughout processing. Non-flammable. Chemically inactive. Uniform in colour. What is the thickness of film base? Thickness of film base depends on type of film and its use. Medical x-ray film needs a film base of 0.18mm.(ii)Subbing/adhesive layer; it is situated between the base and emulsion layer. Functions It ensures that the emulsion layer adheres to the base material. To prevent any separation of the emulsion from the base during processing. (iii)The emulsion layer; it is the layer in which a radiographic image is formed. It consists of photosensitive materials suspended in gelatin. Types of films according to film construction Duplitized films; these are films with an emulsion layer on both sides of the base. Single sided film; these are films with one emulsion layer only on one surface of the base.(iv)The supercoat; this is a thin layer of clear gelatin. Functions To protect the sensitive emulsion. To provide suitable surface characteristics. (iv)Non-curl backing; this is a layer which prevents curling in single-sided emulsion films. Since emulsion layer usually swells during processing, it gives single-sided emulsion films a tendency to curl.→ Duplitized films have no tendency to curl due to presence of emulsion layer on each side of the film base hence they have no non-curl backing layer. (iii)Anti-halation layer; it is the layer which prevents reflection of light from the film base back to the emulsion. When light is reflected from the film base back to the emulsion it causes halation. Halation refers to production of diffuse image or ‘halo’ around a proper image.Manufacturers use the following methods of preventing halation. Adding a dye to the non-curl backing. Adding a dye to the base. NB; → Crossover effect; is the type of halation which occurs when a film is used with intensifying screen. Irradiation; is the sideways scattering of light within the emulsion itself. Just like halation, irradiation is another source of image unsharpness.Light-sensitive and X-ray sensitive emulsions There are two fundamentally different conditions of exposure for the films used in an x-ray department. They may be exposed to visible light emitted by fluorescent intensifying screen. They may be exposed solely to radiation. Light-sensitive film Light sensitive films are films in which production of an image is through exposure to visible light.NB; All films are light sensitive but this group of films refers to those films whose image has been formed after exposure to light. The emulsion layer of the film must absorb the energy of the visible light photons incident on it in order to form an image. Silver halide grains in the emulsion layer do absorb visible light photons particularly light in the blue-violet part of the spectrum. But for a photon to be absorbed, there must be a silver halide grain in its path. Therefore, to ensure efficient absorption, the emulsion must contain high concentration of silver halide. The following are ways to increase concentration of silver halide in order to ensure efficient absorption of light photons. Close parking of the silver halide grains Increasing the size of the silver halide grains Increasing the thickness of the emulsion layer Modifying the shape of the halide grains However, emulsion thickness must be limited to optimum thickness for several reasons; Image resolution tends to reduce as emulsion thickness increases. Thick emulsion layers require longer processing times. Most absorption of light occurs in the upper layers of the emulsion. Duplitized films Duplitizing of film is a method of gaining the benefits of increased emulsion thickness with few of the drawbacks. Duplitized film is designed to be used with two intensifying screens. It is the most commonly used type of x-ray film in a radiology department. After processing, a duplitized film has two identical images, one on each side of the film base. When a radiograph is viewed, the two images are superimposed and observed as one. Only on a very close observation it is possible to detect the dual imaged due to parallax effect.Advantages of duplitized films Increased sensitivity; adequate image density can be achieved from a smaller radiation exposure. Increased image contrast; contrast is the ability to distinguish between two different densities on the image. Disadvantages of duplitized films Loss of image quality; due to incidences like crossover effect. Economic reasons; they require a high coating weight of silver than single emulsion films. Silver is an expensive resource. ← 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

CRT04105 Radiographic Imaging Sciences, Diagnostic Radiography NTA Level 4, Diagnostic Radiology Notes, NTA Level 4 Semester One

Chapter 3 Intensifying screen

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Chapter 3 Intensifying screen CRT04105 · Radiographic Imaging Sciences START READING NOTES Study Chapter 3 Intensifying screen using the sections below. Use the topic navigation to continue through Radiographic Imaging Sciences. Chapter 3 Intensifying screen RADIOGRAPHIC IMAGING SCIENCES INTENSIFYING SCREENS An intensifying screen; is a special sheet used to convert xrays into light. When x-rays alone are used to create radiographic images, most pass straight through the films without causing any film blackening (radiographic density). This is because x-rays are so penetrative. Only 1% of x-rays are absorbed by emulsion layers. In order to create adequate film blackening (radiographic density), comparatively large exposures have to be made. This is overcome by the use of an intensifying screen which works to convert small x-ray radiation into large amount of light for image formation. About 30% of the x-rays striking the screen interact with the screen to produce a large number of visible light photons. The use of intensifying screen result in considerable lower radiation dose to the patient but has the disadvantage of causing a slight blurring of the image. Important terminologies Luminescence; refers to the emission of light from a substance bombarded by radiation. Luminescence includes two effects; fluorescence and phosphorescence Fluorescence; refers to the emission of light from a substance bombarded by radiation lasting as soon as radiation exposure is terminated. intensifying screens undergo this phenomena. Phosphorescence; refers to the emission of light from a substance bombarded by radiation which continues for some time (afterglow) even after radiation exposure is terminated. NB; Phosphorescence is an undesirable phenomenon in radiography due to afterglow. Intrinsic/photographic unsharpness; refers to radiographic unsharpness which arises as a consequence of using film and screen material. There are three causes of intrinsic/photographic unsharpness. Divergence of light Poor screen/film contact Cross-over effect Divergence of light; this refers to outward spread of light in all directions from its source. Any point of light arising from the intensifying screen, will no longer be a point by the time it reaches the film emulsion. Poor film/screen contact; loss of close and uniform contact between the screen and film. Cross-over effect; it is the exposure of the emulsion by the light from the opposite intensifying screen. Screen Construction A magnified cross section through an intensifying screen is shown below. (i)Base; is made from paper, cardboard, or more usually a clear plastic such as polyester. Its function is to provide a strong, smooth but flexible support for the fluorescent layer. Thickness of the base is about 0.18mm.Desirable characteristics of base Strong but flexible. Chemically inert/inactive Uniformly radiolucent Moisture resistant Not discolour with age or on exposure to x-rays (ii) Substratum layer; this is the bonding layer between the base and the phosphor layer. It may be reflective, absorptive or simply transparent in nature depending on manufacturer’s intended characteristics for the screen. Reflective substratum layer; it maximizes the effect of the screen by reflecting the light which would be lost through the film, back towards the film emulsion. Absorptive substratum layer; this layer absorbs any light travelling backwards towards the screen base. (iii) Phosphor layer (fluorescent layer); this is the active layer of the screen where fluorescence occurs. It consists of fluorescent crystals (phosphor crystals) which emit light when struck with x-radiation. Phosphor crystals are suspended in a transparent binder such as polyurethane. The binder may also contain carbon granules or acutance dye (coloured pigments) whose function is to absorb any laterally scattered light within the fluorescent layer. →The use of carbon granules minimizes photographic unsharpness but reduces speed of the screen. NB; Coating weight; refers to the quantity of phosphor grains incorporated in a phosphor layer. Factors affecting coating weight; Grain size; it is inversely proportional to coating weight. Coating thickness; it is directly proportional to coating weight. (iv)Supercoat; this is a protective layer and is made up from acetate. It helps to assist surface abrasion. Types of Phosphor Phosphors; are materials which emit visible light when exposed to radiation. Out of many phosphors available, only a few qualify to be used in radiography. The two common qualities of phosphors used in radiography; They are very efficient at x-ray absorption They fluoresce strongly, with little afterglow. There are two main types of phosphors. Conventional phosphors; were common in old screens; e.g. calcium tungstate, barium fluorochloride and barium strontium sulphate. Rare earth phosphors; are common in modern day screens; e.g. gadolinium, lanthanum and yttrium.Advantages of rare earth phosphors over conventional phosphors; They are more efficient at absorbing x-ray photons (absorption efficiency or quantum detection efficiency) They are more efficient at converting x-ray photons to light (conversion efficiency) Quantum Detection Efficiency (QDE) QDE; refers to the ability to absorb incident radiation. Rare earth screens are more efficient in this factor compared to conventional screens of calcium tungstate. Conversion Efficiency This refers to the ability to convert x-ray photon into light. Rare earths are more efficient in this factor as well, e.g. 15- 20% light conversion efficiency compared to calcium tungstate 3-5% Activators Activators; these are small quantities of some foreign materials added to phosphor during manufacture. The phosphor-activator combination determines the intensity of luminescence and colour of light emitted from the screen. Matching film to intensifying screen This involves matching films to the colour of intensifying screen emission. This helps to obtain optimum speed for the film-screen system i.e. maximum film blackening for the least radiographic exposure.e.g. →a screen phosphor emitting light towards the green end of the spectrum is best matched with an orthochromatic film also calcium tungstate (blue emitter) and a monochromatic film. In case of mismatch, the light emission from the screen would have a much diminished effect on the film. Types of screen and their application Screen manufacturers are able to produce a variety of screen speeds by the choice of phosphor and size of the phosphor grain, the addition/exclusion of absorptive/ reflective layers and by varying the amount of reflective/absorptive material used in screen construction. High resolution screen; are

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