This document provides information about dental X-ray machines and the production of X-rays. It discusses the key components of a dental X-ray machine including the control panel, extension arm, and tube head. It describes the cathode, anode, and focal spot within the X-ray tube. Factors that control the X-ray beam such as tube voltage, current, exposure time, and filtration are also covered. The document explains how X-rays are produced via bremsstrahlung radiation and characteristic radiation when electrons interact with the metal target in the X-ray tube.
The x-ray beam is also at an angle to both
the teeth and film. As a result, distortion occurs. In the
radiograph of the mandibular first molar below, the
buccal root appears elongated and narrower than the
palatal root due to the angulation of the x-ray beam.
This document discusses collimation and filtration in dental x-rays. It explains that collimators are used to restrict the size of the x-ray beam in order to minimize radiation exposure and scattered radiation. There are different types of collimators including diaphragm, round, rectangular, and slit collimators. Filtration is also discussed, which involves removing low-energy photons from the beam to reduce unnecessary radiation exposure while maintaining diagnostic image quality. Common filtration materials mentioned are aluminum, copper, tin, and lead. The effects of proper collimation and filtration are to harden the beam and reduce radiation dose to patients.
This document discusses various topics in radiation physics including:
- Atomic structure and the Bohr model of the atom.
- Composition and interactions of x-ray radiation.
- Components and function of x-ray machines including the cathode, anode, and power supply.
- Factors that control the x-ray beam such as milliamperage, kilovoltage, filtration, and collimation.
- Three main interactions of x-rays with matter: photoelectric absorption, Compton scattering, and coherent scattering.
- Key radiation physics concepts including exposure, absorbed dose, equivalent dose, and radioactivity.
This document provides information on the processing of dental radiographs, including definitions of key terms, the formation of latent images, film processing solutions and procedures, darkroom requirements, and various processing methods. It describes how exposure to radiation results in chemical changes in the film's silver halide crystals to form a latent image, which is then made visible through development and fixing solutions. The roles of developer solutions, fixing solutions, and processing equipment are summarized.
The document provides an overview of X-rays and their use in dentistry. It begins with an introduction to the discovery of X-rays by Wilhelm Roentgen in 1895. It then discusses the basic components and function of an X-ray tube, including the cathode, filament, focusing cup and anode. The document also covers the properties of X-rays, how they are produced, their interactions with matter, and their various uses including in diagnosis and treatment in dentistry and medicine.
Sialography is an x-ray examination of the salivary glands that involves injecting contrast media into the ducts to evaluate any abnormalities. It can detect issues like stones, lesions, or masses that may be obstructing the ducts and causing pain or inflammation. There are three major pairs of salivary glands - parotid, submandibular, and sublingual - which produce saliva. Sialography can be used to evaluate masses, stones, pain, functional disorders, and suspected obstructions or strictures of the salivary glands. The procedure involves injecting contrast media under fluoroscopy and taking x-ray images to view the flow of saliva and identify any ob
The x-ray beam is also at an angle to both
the teeth and film. As a result, distortion occurs. In the
radiograph of the mandibular first molar below, the
buccal root appears elongated and narrower than the
palatal root due to the angulation of the x-ray beam.
This document discusses collimation and filtration in dental x-rays. It explains that collimators are used to restrict the size of the x-ray beam in order to minimize radiation exposure and scattered radiation. There are different types of collimators including diaphragm, round, rectangular, and slit collimators. Filtration is also discussed, which involves removing low-energy photons from the beam to reduce unnecessary radiation exposure while maintaining diagnostic image quality. Common filtration materials mentioned are aluminum, copper, tin, and lead. The effects of proper collimation and filtration are to harden the beam and reduce radiation dose to patients.
This document discusses various topics in radiation physics including:
- Atomic structure and the Bohr model of the atom.
- Composition and interactions of x-ray radiation.
- Components and function of x-ray machines including the cathode, anode, and power supply.
- Factors that control the x-ray beam such as milliamperage, kilovoltage, filtration, and collimation.
- Three main interactions of x-rays with matter: photoelectric absorption, Compton scattering, and coherent scattering.
- Key radiation physics concepts including exposure, absorbed dose, equivalent dose, and radioactivity.
This document provides information on the processing of dental radiographs, including definitions of key terms, the formation of latent images, film processing solutions and procedures, darkroom requirements, and various processing methods. It describes how exposure to radiation results in chemical changes in the film's silver halide crystals to form a latent image, which is then made visible through development and fixing solutions. The roles of developer solutions, fixing solutions, and processing equipment are summarized.
The document provides an overview of X-rays and their use in dentistry. It begins with an introduction to the discovery of X-rays by Wilhelm Roentgen in 1895. It then discusses the basic components and function of an X-ray tube, including the cathode, filament, focusing cup and anode. The document also covers the properties of X-rays, how they are produced, their interactions with matter, and their various uses including in diagnosis and treatment in dentistry and medicine.
Sialography is an x-ray examination of the salivary glands that involves injecting contrast media into the ducts to evaluate any abnormalities. It can detect issues like stones, lesions, or masses that may be obstructing the ducts and causing pain or inflammation. There are three major pairs of salivary glands - parotid, submandibular, and sublingual - which produce saliva. Sialography can be used to evaluate masses, stones, pain, functional disorders, and suspected obstructions or strictures of the salivary glands. The procedure involves injecting contrast media under fluoroscopy and taking x-ray images to view the flow of saliva and identify any ob
The xeroradiographic plate consists of the following layers:
1. An aluminum substrate that provides a smooth surface for the photoconductor layer.
2. An interface layer of aluminum oxide between the selenium photoconductor and aluminum substrate to prevent charge exchange.
3. A selenium photoconductor layer that becomes electrically conductive upon exposure to x-rays, forming a latent electrostatic image.
4. A protective coating over the selenium layer to prevent degradation and improve shelf life.
The document discusses filtration and collimation in x-ray beams. Filtration removes low-energy photons that do not contribute to the image but increase patient exposure. Filters are typically made of aluminum and selectively allow high-energy photons to pass. Collimation uses a lead plate with a central hole to restrict the beam to only the area being imaged, reducing patient exposure and preventing scatter that degrades image quality. Both filtration and collimation aim to improve image quality while lowering radiation dose.
Radiation safety and protection for dental radiographyNitin Sharma
1) Licensed dentists must maintain radiation exposures as low as reasonably achievable and understand the health risks of radiation.
2) Dental radiographic equipment must be registered and follow safety protocols to protect patients and staff, such as using protective gear and collimation.
3) Dentists are responsible for quality assurance programs to ensure proper functioning and calibration of dental X-ray machines and processing of films. Guidelines help prescribe radiographs appropriately.
The line focus principle helps resolve the issue of needing a small focal spot for good image quality while also needing a large focal spot to protect the tungsten target from heat accumulation. It works by mounting the target at an angled position, so that the apparent or effective focal spot size seen from the position of the film is smaller than the actual focal spot size. The effective focal spot size can be calculated as the actual focal spot size multiplied by the sine of the anode angle. This allows heat to dissipate over a larger area while maintaining a small focal spot for image sharpness. A limitation is the anode heel effect caused by non-uniform radiation from different parts of the angled anode surface. The target angle
brief description about CONTENTS Introduction Principles of panoramic imaging Image layer Panoramic machines Panoramic film Patient positioning Interpreting the panoramic imaging INDICATION Advantages Disadvantages Conclusion References
3. INTRODUCTION • Panoramic imaging also called pantomography is a technique for producing a single tomographic image of facial structures that includes both the maxillary and mandibular dental arches and their supporting structures . • This is a curvilinear variant of conventional tomography.
4. PRINCIPLES OF PANORAMIC IMAGE FORMATION • Patero and Numata - describe the principles of panoramic radiography • based on the principle of reciprocal movement of x-ray source and an image receptor around a central point or plane called the image layer, in which the OBJECT of image is located. • OBJECT in front or behind this image are not clearly captured because of their movement relative to the centre of rotation of the receptor and the x-ray source.
5. The film and x-ray tubehead move around the patient in opposite directions in panoramic radiography
6. ROTATION CENTER The pivotal point or axis around which the cassette carrier and tube head rotate is termed rotation center Three basic rotation center used in panoramic radiography Double centre rotation Triple centre rotation moving centre rotation The location and number of rotational centers INFLUENCE size and shape of focal trough
7. IMAGE LAYER • Also known as focal trough • It is a three dimensional curved zone where the structures lying within this layer are reasonably well defined on final panoramic image. • The structures seen on a panoramic image are primarily those located within image layer. • OBJECTSoutside the image layer are blurred magnified are reduced in size. Even distorted to the extent of not being recognizable. • This shape of image layer varies with the brand of equipment used.
8. FOCAL TROUGH
9. FACTORS AFFECTING SIZE OF IMAGE LAYER: Arc path Velocity of receptor and X-ray tube head Alignment of x-ray beam Collimator width The location of image layer change with extensive machine used so recalibration may be necessary if consistently suboptimal images are produced. As a position of object is moved within the image layer size and shape of image layer change.
10. PANORAMIC UNIT
11. A, Orthophos XG Plus extraoral x-ray machine. B, Orthoralix 8500 extraoral x-ray machine. C, Example of a digital panoramic system
12. PARTS OF PANORAMIC UNITS a. x-ray tube head b. head positioner: chin rest notched bite block forehead rest lateral head support c. exposure controls
13. X-RAY TUBE HEAD: • Similar to intraoral x-ray tube head • Each has a filament to produce electrons and a target to produce x-rays • Collimator is a lead plate with narrow vertical slit • Narrow x-ray beam emerges from collimator minimize patient exposure to radiation
1
This document discusses the key factors that control an x-ray beam, including exposure time, tube current, tube voltage, filtration, collimation, source-to-film distance, and target material. It explains how each factor affects the quantity and quality of the x-ray beam by influencing the number of photons generated, their mean energy and maximum energy. The document provides details on how varying these technical parameters can optimize radiographic image quality while maintaining patient safety.
This document describes the procedures for sialography and dacrocystography. Sialography involves cannulating the ducts of the parotid and submandibular salivary glands and injecting contrast medium to visualize the glands and ducts under fluoroscopy. Dacrocystography involves cannulating the lacrimal puncta and injecting contrast into the nasolacrimal duct system to identify any obstructions. Both procedures provide anatomical imaging of the relevant duct systems to evaluate conditions like stones, strictures, masses or trauma. The document outlines the anatomy, indications, contraindications, technique and expected imaging findings for each procedure.
Xeroradiography is a method of medical imaging that uses the xerographic copying process to produce images from diagnostic x-rays. It involves charging a photoconductive plate, typically made of selenium, then exposing it to x-rays to create a latent electrostatic image. This image is developed using charged toner powder and transferred to paper, producing a visible x-ray image. Key advantages are eliminating accidental film exposure, providing high resolution and the ability to simultaneously evaluate multiple tissues. However, it also has disadvantages like being unable to image very thick body parts and having fragile selenium coatings.
This document provides information on various types of image receptors used in dental radiography. It discusses the history of x-ray film and describes the components of intraoral and extraoral films. It also covers intensifying screens, digital receptors like CCD, CMOS, and flat panel detectors, and photo stimulable phosphor plates. The document details the composition of films and screens and factors affecting film speed, contrast, and detail. It compares the advantages and disadvantages of screen-film systems and digital receptors.
The document discusses various radiation protection measures for patients, operators, and the environment during dental radiography. It outlines techniques to minimize radiation exposure before, during, and after x-ray procedures for patients such as proper prescribing, use of protective equipment like aprons and collars, and fast film. Operator protection includes guidelines on distance, positioning, shielding, and monitoring. The environment is protected by shielding walls, doors, and limiting the primary beam. Regulations establish safe exposure limits.
X-ray film consists of an emulsion layer containing light-sensitive silver halide crystals suspended in a gelatin matrix coated on a polyester base. The crystals capture a latent image when exposed to radiation that is then developed using chemical solutions. Dental x-ray films are available in different sizes for various views and come packaged with a lead foil backing to shield the film and reduce scatter radiation. Intraoral films use small silver halide crystals to capture high-resolution images, while extraoral films employ intensifying screens to emit light and increase film sensitivity. Proper exposure, development, and fixing are required to produce radiographs with optimal density and contrast for diagnosis.
IDEAL IMAGE CHARACTERISTICS
FACTORS RELATED TO THE RADIATION BEAM
FACTORS RELATED TO THE OBJECT
FACTORS RELATED TO THE TECHNIQUE
FACTORS RELATED TO RECORDING OF THE ROENTGEN IMAGE OF THE OBJECT
DARK/ LIGHT IMAGE IDEAL IMAGE
IDEAL QUALITY CRIETRIA
This document discusses dental radiography and x-rays. It defines key terms like radiograph and radiology. It describes the components of a dental x-ray unit and different types of radiographs like bitewings and panoramic x-rays. It discusses techniques like paralleling, bisecting angle technique and SLOB technique. It also covers topics like indications for radiographs, radiation safety, and advantages and disadvantages of digital radiography compared to conventional film.
This document discusses common radiographic errors and artifacts that can occur during dental x-ray procedures. It identifies three main categories of errors: technique and projection errors, exposure errors, and processing errors. Technique errors include issues with patient preparation, film placement, and projection angles. Exposure errors result in over or underexposed images. Processing errors stem from chemical or film handling issues during development and fixing of the x-ray film. The document provides examples and explanations of specific errors like double images, cut-off areas, density problems, and chemical or physical marks that can affect image quality and interpretation.
The document discusses different types of radiography technologies, including computed radiography (CR), direct digital radiography (DR), and the components and layers of imaging plates (IPs) used in CR. It also covers image processing techniques for CR/DR such as histogram generation, exposure compensation, and potential artifacts that can occur during acquisition, post-acquisition or display.
This document provides information on dental x-ray film processing, including the various steps and methods. It discusses manual processing which involves development, rinsing, fixing, washing and drying. Development uses a chemical developer to convert the latent image into visible metallic silver. The document also describes automatic processing, daylight processing, and self-developing films. It explains the various solutions used like developer and fixer, as well as the chemicals that make up each solution and their purposes.
A dental x-ray machine consists of a tubehead, support arms, and control panel. The tubehead contains an x-ray tube with a cathode and anode, as well as transformers that convert electrical current. The control panel regulates voltage and current to the x-ray tube. Dental x-rays are collimated and filtered to shape and soften the beam, reducing radiation exposure for patients.
Characteristic x-rays are produced when an inner shell electron is ejected from an atom during bombardment and an outer shell electron fills the vacancy, while bremsstrahlung x-rays result from the deceleration of electrons when their trajectory is altered by the electric field of atomic nuclei. In diagnostic medical imaging, most x-rays produced are bremsstrahlung due to the voltages used, though some characteristic x-rays are also produced at higher voltages. The efficiency of x-ray production increases with higher kilovolt peak (kVp) voltages.
The document describes the composition and uses of intraoral and extraoral films and intensifying screens used in dental radiography. It discusses the components of intraoral and extraoral films, including the plastic base, double emulsion containing silver halide crystals, and protective layers. It also describes the composition and function of intensifying screens containing rare earth phosphor crystals that emit light when exposed to x-rays. The document provides details on different film types, speeds, sizes and storage as well as cassette, barrier packets and processing.
Factors affecting Quality and Quantity of X-ray beamVinay Desai
The document discusses the components and functioning of an X-ray tube. It describes how X-ray tubes generate X-rays by accelerating electrons using high voltage and directing them at a metal target. It explains how factors like voltage, current, target material, filtration and waveform affect the quality and quantity of the X-ray beam produced. It also discusses X-ray tube ratings and charts that determine safe operational limits for exposures based on combinations of voltage, current and time to prevent overheating.
This document provides an overview of x-ray production for dental applications. It discusses the components of an x-ray machine including the high and low voltage circuits and transformers. The document describes how x-rays are produced in the x-ray tube via thermionic emission when electrons are accelerated toward the tungsten anode. This results in both characteristic and braking radiation. It also discusses the line focus principle and types of dental x-rays produced. The objective is to understand x-ray production and different types of dental x-rays.
1. An x-ray tube converts electrical energy into x-radiation and heat through a process where electrons from the cathode target the anode, releasing photons.
2. The principal components of an x-ray tube are the cathode, which emits electrons, and the anode, which acts as the target. In rotating anode tubes, the anode rotates to dissipate heat during exposures.
3. Tungsten is commonly used for the filament and target due to its high melting point and ability to efficiently produce x-rays. The filament is heated through thermionic emission to release electrons, while the target converts their impact into x-radiation.
The xeroradiographic plate consists of the following layers:
1. An aluminum substrate that provides a smooth surface for the photoconductor layer.
2. An interface layer of aluminum oxide between the selenium photoconductor and aluminum substrate to prevent charge exchange.
3. A selenium photoconductor layer that becomes electrically conductive upon exposure to x-rays, forming a latent electrostatic image.
4. A protective coating over the selenium layer to prevent degradation and improve shelf life.
The document discusses filtration and collimation in x-ray beams. Filtration removes low-energy photons that do not contribute to the image but increase patient exposure. Filters are typically made of aluminum and selectively allow high-energy photons to pass. Collimation uses a lead plate with a central hole to restrict the beam to only the area being imaged, reducing patient exposure and preventing scatter that degrades image quality. Both filtration and collimation aim to improve image quality while lowering radiation dose.
Radiation safety and protection for dental radiographyNitin Sharma
1) Licensed dentists must maintain radiation exposures as low as reasonably achievable and understand the health risks of radiation.
2) Dental radiographic equipment must be registered and follow safety protocols to protect patients and staff, such as using protective gear and collimation.
3) Dentists are responsible for quality assurance programs to ensure proper functioning and calibration of dental X-ray machines and processing of films. Guidelines help prescribe radiographs appropriately.
The line focus principle helps resolve the issue of needing a small focal spot for good image quality while also needing a large focal spot to protect the tungsten target from heat accumulation. It works by mounting the target at an angled position, so that the apparent or effective focal spot size seen from the position of the film is smaller than the actual focal spot size. The effective focal spot size can be calculated as the actual focal spot size multiplied by the sine of the anode angle. This allows heat to dissipate over a larger area while maintaining a small focal spot for image sharpness. A limitation is the anode heel effect caused by non-uniform radiation from different parts of the angled anode surface. The target angle
brief description about CONTENTS Introduction Principles of panoramic imaging Image layer Panoramic machines Panoramic film Patient positioning Interpreting the panoramic imaging INDICATION Advantages Disadvantages Conclusion References
3. INTRODUCTION • Panoramic imaging also called pantomography is a technique for producing a single tomographic image of facial structures that includes both the maxillary and mandibular dental arches and their supporting structures . • This is a curvilinear variant of conventional tomography.
4. PRINCIPLES OF PANORAMIC IMAGE FORMATION • Patero and Numata - describe the principles of panoramic radiography • based on the principle of reciprocal movement of x-ray source and an image receptor around a central point or plane called the image layer, in which the OBJECT of image is located. • OBJECT in front or behind this image are not clearly captured because of their movement relative to the centre of rotation of the receptor and the x-ray source.
5. The film and x-ray tubehead move around the patient in opposite directions in panoramic radiography
6. ROTATION CENTER The pivotal point or axis around which the cassette carrier and tube head rotate is termed rotation center Three basic rotation center used in panoramic radiography Double centre rotation Triple centre rotation moving centre rotation The location and number of rotational centers INFLUENCE size and shape of focal trough
7. IMAGE LAYER • Also known as focal trough • It is a three dimensional curved zone where the structures lying within this layer are reasonably well defined on final panoramic image. • The structures seen on a panoramic image are primarily those located within image layer. • OBJECTSoutside the image layer are blurred magnified are reduced in size. Even distorted to the extent of not being recognizable. • This shape of image layer varies with the brand of equipment used.
8. FOCAL TROUGH
9. FACTORS AFFECTING SIZE OF IMAGE LAYER: Arc path Velocity of receptor and X-ray tube head Alignment of x-ray beam Collimator width The location of image layer change with extensive machine used so recalibration may be necessary if consistently suboptimal images are produced. As a position of object is moved within the image layer size and shape of image layer change.
10. PANORAMIC UNIT
11. A, Orthophos XG Plus extraoral x-ray machine. B, Orthoralix 8500 extraoral x-ray machine. C, Example of a digital panoramic system
12. PARTS OF PANORAMIC UNITS a. x-ray tube head b. head positioner: chin rest notched bite block forehead rest lateral head support c. exposure controls
13. X-RAY TUBE HEAD: • Similar to intraoral x-ray tube head • Each has a filament to produce electrons and a target to produce x-rays • Collimator is a lead plate with narrow vertical slit • Narrow x-ray beam emerges from collimator minimize patient exposure to radiation
1
This document discusses the key factors that control an x-ray beam, including exposure time, tube current, tube voltage, filtration, collimation, source-to-film distance, and target material. It explains how each factor affects the quantity and quality of the x-ray beam by influencing the number of photons generated, their mean energy and maximum energy. The document provides details on how varying these technical parameters can optimize radiographic image quality while maintaining patient safety.
This document describes the procedures for sialography and dacrocystography. Sialography involves cannulating the ducts of the parotid and submandibular salivary glands and injecting contrast medium to visualize the glands and ducts under fluoroscopy. Dacrocystography involves cannulating the lacrimal puncta and injecting contrast into the nasolacrimal duct system to identify any obstructions. Both procedures provide anatomical imaging of the relevant duct systems to evaluate conditions like stones, strictures, masses or trauma. The document outlines the anatomy, indications, contraindications, technique and expected imaging findings for each procedure.
Xeroradiography is a method of medical imaging that uses the xerographic copying process to produce images from diagnostic x-rays. It involves charging a photoconductive plate, typically made of selenium, then exposing it to x-rays to create a latent electrostatic image. This image is developed using charged toner powder and transferred to paper, producing a visible x-ray image. Key advantages are eliminating accidental film exposure, providing high resolution and the ability to simultaneously evaluate multiple tissues. However, it also has disadvantages like being unable to image very thick body parts and having fragile selenium coatings.
This document provides information on various types of image receptors used in dental radiography. It discusses the history of x-ray film and describes the components of intraoral and extraoral films. It also covers intensifying screens, digital receptors like CCD, CMOS, and flat panel detectors, and photo stimulable phosphor plates. The document details the composition of films and screens and factors affecting film speed, contrast, and detail. It compares the advantages and disadvantages of screen-film systems and digital receptors.
The document discusses various radiation protection measures for patients, operators, and the environment during dental radiography. It outlines techniques to minimize radiation exposure before, during, and after x-ray procedures for patients such as proper prescribing, use of protective equipment like aprons and collars, and fast film. Operator protection includes guidelines on distance, positioning, shielding, and monitoring. The environment is protected by shielding walls, doors, and limiting the primary beam. Regulations establish safe exposure limits.
X-ray film consists of an emulsion layer containing light-sensitive silver halide crystals suspended in a gelatin matrix coated on a polyester base. The crystals capture a latent image when exposed to radiation that is then developed using chemical solutions. Dental x-ray films are available in different sizes for various views and come packaged with a lead foil backing to shield the film and reduce scatter radiation. Intraoral films use small silver halide crystals to capture high-resolution images, while extraoral films employ intensifying screens to emit light and increase film sensitivity. Proper exposure, development, and fixing are required to produce radiographs with optimal density and contrast for diagnosis.
IDEAL IMAGE CHARACTERISTICS
FACTORS RELATED TO THE RADIATION BEAM
FACTORS RELATED TO THE OBJECT
FACTORS RELATED TO THE TECHNIQUE
FACTORS RELATED TO RECORDING OF THE ROENTGEN IMAGE OF THE OBJECT
DARK/ LIGHT IMAGE IDEAL IMAGE
IDEAL QUALITY CRIETRIA
This document discusses dental radiography and x-rays. It defines key terms like radiograph and radiology. It describes the components of a dental x-ray unit and different types of radiographs like bitewings and panoramic x-rays. It discusses techniques like paralleling, bisecting angle technique and SLOB technique. It also covers topics like indications for radiographs, radiation safety, and advantages and disadvantages of digital radiography compared to conventional film.
This document discusses common radiographic errors and artifacts that can occur during dental x-ray procedures. It identifies three main categories of errors: technique and projection errors, exposure errors, and processing errors. Technique errors include issues with patient preparation, film placement, and projection angles. Exposure errors result in over or underexposed images. Processing errors stem from chemical or film handling issues during development and fixing of the x-ray film. The document provides examples and explanations of specific errors like double images, cut-off areas, density problems, and chemical or physical marks that can affect image quality and interpretation.
The document discusses different types of radiography technologies, including computed radiography (CR), direct digital radiography (DR), and the components and layers of imaging plates (IPs) used in CR. It also covers image processing techniques for CR/DR such as histogram generation, exposure compensation, and potential artifacts that can occur during acquisition, post-acquisition or display.
This document provides information on dental x-ray film processing, including the various steps and methods. It discusses manual processing which involves development, rinsing, fixing, washing and drying. Development uses a chemical developer to convert the latent image into visible metallic silver. The document also describes automatic processing, daylight processing, and self-developing films. It explains the various solutions used like developer and fixer, as well as the chemicals that make up each solution and their purposes.
A dental x-ray machine consists of a tubehead, support arms, and control panel. The tubehead contains an x-ray tube with a cathode and anode, as well as transformers that convert electrical current. The control panel regulates voltage and current to the x-ray tube. Dental x-rays are collimated and filtered to shape and soften the beam, reducing radiation exposure for patients.
Characteristic x-rays are produced when an inner shell electron is ejected from an atom during bombardment and an outer shell electron fills the vacancy, while bremsstrahlung x-rays result from the deceleration of electrons when their trajectory is altered by the electric field of atomic nuclei. In diagnostic medical imaging, most x-rays produced are bremsstrahlung due to the voltages used, though some characteristic x-rays are also produced at higher voltages. The efficiency of x-ray production increases with higher kilovolt peak (kVp) voltages.
The document describes the composition and uses of intraoral and extraoral films and intensifying screens used in dental radiography. It discusses the components of intraoral and extraoral films, including the plastic base, double emulsion containing silver halide crystals, and protective layers. It also describes the composition and function of intensifying screens containing rare earth phosphor crystals that emit light when exposed to x-rays. The document provides details on different film types, speeds, sizes and storage as well as cassette, barrier packets and processing.
Factors affecting Quality and Quantity of X-ray beamVinay Desai
The document discusses the components and functioning of an X-ray tube. It describes how X-ray tubes generate X-rays by accelerating electrons using high voltage and directing them at a metal target. It explains how factors like voltage, current, target material, filtration and waveform affect the quality and quantity of the X-ray beam produced. It also discusses X-ray tube ratings and charts that determine safe operational limits for exposures based on combinations of voltage, current and time to prevent overheating.
This document provides an overview of x-ray production for dental applications. It discusses the components of an x-ray machine including the high and low voltage circuits and transformers. The document describes how x-rays are produced in the x-ray tube via thermionic emission when electrons are accelerated toward the tungsten anode. This results in both characteristic and braking radiation. It also discusses the line focus principle and types of dental x-rays produced. The objective is to understand x-ray production and different types of dental x-rays.
1. An x-ray tube converts electrical energy into x-radiation and heat through a process where electrons from the cathode target the anode, releasing photons.
2. The principal components of an x-ray tube are the cathode, which emits electrons, and the anode, which acts as the target. In rotating anode tubes, the anode rotates to dissipate heat during exposures.
3. Tungsten is commonly used for the filament and target due to its high melting point and ability to efficiently produce x-rays. The filament is heated through thermionic emission to release electrons, while the target converts their impact into x-radiation.
This document provides an overview of x-rays and x-ray tubes. It discusses the history of x-rays starting with their discovery by Wilhelm Roentgen in 1895. It then covers basic x-ray physics and the electromagnetic spectrum. The document focuses on the components and functioning of x-ray tubes, including the cathode, filament, focusing cup, anode, rotating target, and control console. It explains how varying the kVp and mAs settings on the control console controls the x-ray beam properties.
The document discusses the components and functioning of an X-ray tube. The key components are the glass envelope, cathode, and anode. Electrons are emitted from the cathode filament and accelerated toward the anode, where their impact produces X-rays. The rotating anode allows for greater heat dissipation to enable higher exposures. Factors like focal spot size and the anode heel effect determine the quality and characteristics of the emitted X-rays. Proper cooling and protective housing are also important for safe tube operation.
The document discusses the history and components of X-ray machines. It begins with a brief history of the discovery of X-rays by Wilhelm Roentgen in 1895 and important developments in dental radiology. It then describes the ideal requirements and main components of an X-ray tubehead, including the X-ray tube, position indicating device, and collimator. The document explains the circuitry and components within the X-ray tube, such as the cathode, anode, and line focus principle. It concludes with a discussion of advances in X-ray machines.
The document discusses the components and functioning of an X-ray tube. It describes the evolution from early gas tubes to modern Coolidge tubes. Key components include a cathode that emits electrons via thermionic emission, a target anode where X-rays are produced, and a rotating anode design that allows for higher power outputs by spreading heat load. Modern tubes operate similarly to Coolidge tubes but with refinements like line focal spots and rotating anodes to improve performance.
Production of x rays
Components of X-ray
Cathode
kVp , mA , mAs .
Line focus principle
Heel effect
anode
Stationary anode x ray tube
Rotating anode x-ray tube
Grid controlled x-ray tube
Saturation voltage
Metal ceramic x – ray tube
Processes of x- ray generation
intensity of the x-ray beams
Effect of kVp on x- ray beam
Effect of tube current on x- ray beam
learn with Me...........MK
if you notice any mistake comment please ......
The document summarizes the major components and functioning of an x-ray tube. It describes the cathode, which emits electrons via thermionic emission from a tungsten filament. The electrons are accelerated toward the positively charged anode target, where their deceleration produces x-rays. Key factors that influence x-ray production and quality include the rotating anode design, line focus principle, and cooling mechanisms to manage heat load on the target. The document also outlines charts and guidelines used to safely operate x-ray tubes within their thermal limits.
The document summarizes the major components and functioning of an x-ray tube. It describes the cathode, which emits electrons via thermionic emission from a tungsten filament. The electrons are accelerated toward the positively charged anode target, where their deceleration produces x-rays. Key factors that influence x-ray production and quality include the rotating anode design, line focus principle, and cooling mechanisms to manage heat load on the target. The document also outlines charts and guidelines used to safely operate x-ray tubes within their thermal limits.
basic of angiography physics and equipement.pdfnaima SENHOU
Angiography uses iodinated contrast medium and x-rays to visualize blood vessels. The document discusses the basic components of angiography equipment, including the x-ray tube, generator, patient table, beam filtration, collimation, anti-scatter grid, and image receptor. It describes the functions of image intensifiers and flat panel detectors in converting x-ray energy into a visible light image for angiography. The learning objectives cover differentiating angiography from other exams, components of the angiography system, image modes, and factors controlling dose and image quality.
PRODUCTION AND PROPERTIES OF X.pptx BY MANOJ MANDAL(1).pptxManojMandal65
This document provides information about x-rays and the components responsible for their production. It discusses the history of x-ray discovery by Wilhelm Röntgen in 1895. It then describes the key components of an x-ray tube, including the cathode which emits electrons, and the anode which converts the electron energy into x-rays. The document explains how tungsten is commonly used for the filament and target due to its high melting point and ability to efficiently produce x-rays. It also discusses factors like focal spot size and line focus principle which allow controlling the size and shape of the x-ray beam.
X-rays are produced when fast moving electrons are decelerated upon impact with a metal target in an X-ray tube. The tube contains a cathode that emits electrons and a rotating anode that absorbs the electrons. Upon electron deceleration, both characteristic X-rays specific to the target material and continuous spectrum bremsstrahlung X-rays are produced. The intensity of the X-ray beam depends on factors like target atomic number, applied voltage, and tube current. Rotating the anode helps dissipate heat and provides a consistent focal spot.
1. X-rays are produced when fast moving electrons are decelerated upon striking a metal target in an x-ray tube.
2. Modern x-ray tubes use a tungsten target and operate under vacuum to allow for control of the electron beam and prevent degradation of the tube.
3. X-ray output is determined by tube voltage (kVp), current (mAs), and filtration - with higher kVp and mAs producing higher quality and quantity respectively.
X- Ray physics- X-Ray Tube, Transformer, Generator and Rectifiers by kajalsra...DrKajalLimbad
X-Ray physics including x-ray tube, transformer, generator, and rectifiers. physics made an easy
Note: this ppt has many animations that may not be appreciated over here. Request original ppt at kajalsradiology@gmail.com
X-rays are produced when fast moving electrons are decelerated upon impact with the target anode of an x-ray tube. The x-ray tube contains a cathode that emits electrons and a stationary or rotating anode target. When electrons collide with the anode, x-rays are produced via two processes: characteristic radiation from electron shell interactions and continuous bremsstrahlung radiation from deflected electrons. Additional components such as filters and housing manage heat dissipation and focus the x-ray beam for medical imaging applications.
The document summarizes the key components and functioning of an X-ray machine. It describes the tube head, X-ray tube, and power supply components including transformers. It explains how electrons are emitted from the cathode and accelerated towards the anode target to produce X-rays. The document also discusses factors like vacuum, focal spot size, and angle of target placement that influence image quality and heat dissipation.
1. A current is passed through the tungsten filament to heat it up via thermionic emission and release electrons.
2. The electrons are accelerated towards the positively charged anode by the tube voltage and interact with the anode material, primarily releasing x-ray photons via Bremsstrahlung and characteristic interactions.
3. The resulting x-ray beam exits the tube and passes through the patient to form an x-ray image.
This document discusses UV-Visible spectroscopy instrumentation. It describes the key components of a UV-Visible spectrophotometer including light sources like hydrogen discharge lamps, wavelength selectors like monochromators and filters, sample holders, detectors like photomultiplier tubes, and how these components work together in single-beam and double-beam instrument designs to measure absorbance spectra. The learning objectives are to understand the principles and components of UV-Visible spectroscopy instrumentation.
Cobalt-60 is commonly used as a gamma ray source for teletherapy due to its suitable properties. A Co-60 unit contains a sealed radioactive Co-60 source that emits two gamma rays during decay. The source is moved between shielded and treatment positions using various mechanisms. Beam size and shape are controlled through collimation and additional devices can modify the beam. Precise patient and beam positioning is enabled through computer control and motorized components while shielding protects staff from radiation.
This document provides information on various medical imaging modalities used in veterinary medicine, including how they work, their uses, risks, and safety procedures. It describes computed tomography (CT), magnetic resonance imaging (MRI), digital fluoroscopy, digital/computed radiography, ultrasound, nuclear scintigraphy, endoscopy, electrocardiography, and general radiography. For each modality, it explains the basic principles, anatomical areas examined, and important considerations like patient preparation, potential complications, and radiation safety.
The document discusses various types of artifacts that may occur in radiographs including technique artifacts from errors in patient preparation, film placement, overlapping, and shape distortion. It provides examples for each type of artifact with descriptions of their appearance, causes, and corrections to avoid them. Proper patient positioning, central beam alignment, vertical and horizontal angulation are emphasized to obtain diagnostic images and avoid needing to retake radiographs and exposing patients to unnecessary radiation.
An ideal radiograph has the desired density and contrast to show details clearly without distortion. Several factors influence radiographic quality, including density, contrast, speed, latitude, noise, and blurring. Density depends on exposure, subject thickness, and composition. Contrast is affected by subject contrast, film contrast, and scattered radiation. Film speed indicates the exposure needed to achieve a standard density. Latitude refers to the range of densities a film can record. Noise and blurring degrade image quality. Overall image quality results from the combination of these technical characteristics.
The document discusses dental film and film processing. It provides details on:
- The types of dental film including intraoral, extraoral, and duplicating film.
- Film components such as the film base, emulsion, and intensifying screens.
- Film characteristics including speed, size, and packet contents.
- The five steps of film processing: development, rinsing, fixation, washing, and drying.
- Darkroom requirements including light-tight conditions and types of lighting.
This document provides an overview of corticosteroids, including their history, biosynthesis, classification, mechanisms of action, therapeutic uses, and adverse effects. Corticosteroids are steroid hormones produced in the adrenal cortex from cholesterol. They have important roles in carbohydrate, protein, and fat metabolism, electrolyte balance, and anti-inflammatory responses. Common therapeutic uses include replacement therapy for adrenal insufficiency, and treatment of conditions like arthritis, asthma, skin diseases, and organ transplantation. Adverse effects can include fluid retention, altered electrolyte levels, infections, delayed wound healing, and osteoporosis. Inhaled corticosteroids are commonly used as first-line therapy for chronic asthma.
Nuclear medicine is a medical specialty that uses small amounts of radioactive substances to diagnose and treat diseases. These radioactive substances, known as radiopharmaceuticals, are detected by specialized imaging equipment that utilizes the radiation emitted. Common nuclear medicine procedures include PET scans, SPECT scans, and bone scans which provide functional information about organs and tissues. Radiopharmaceuticals are administered to patients and their distribution throughout the body is tracked using gamma cameras or PET scanners. Nuclear medicine plays an important role in diagnosing and monitoring many diseases.
This document provides a classification and overview of various tongue disorders and conditions. It discusses inherited, congenital, developmental anomalies as well as disorders affecting the lingual mucosa, body of the tongue, and tumors of the tongue. Specific conditions covered include geographic tongue, hairy tongue, median rhomboid glossitis, macroglossia, fissured tongue, ankyloglossia and more. For each condition, the document provides details on etiology, clinical features, management and related syndromes.
This document discusses the development of the pharyngeal arches. It begins by introducing the pharyngeal arches and their components, which include ectoderm, endoderm, mesoderm and neural crest cells. It then describes the formation and derivatives of each of the first, second, third, fourth and sixth pharyngeal arches. This includes the muscles, bones, cartilages and other structures derived from each arch. It also discusses the fate of the pharyngeal pouches and clefts. Finally, it mentions some clinical correlations involving abnormalities in pharyngeal arch development.
TEST BANK FOR Health Assessment in Nursing 7th Edition by Weber Chapters 1 - ...rightmanforbloodline
TEST BANK FOR Health Assessment in Nursing 7th Edition by Weber Chapters 1 - 34.
TEST BANK FOR Health Assessment in Nursing 7th Edition by Weber Chapters 1 - 34.
TEST BANK FOR Health Assessment in Nursing 7th Edition by Weber Chapters 1 - 34.
CHAPTER 1 SEMESTER V COMMUNICATION TECHNIQUES FOR CHILDREN.pdfSachin Sharma
Here are some key objectives of communication with children:
Build Trust and Security:
Establish a safe and supportive environment where children feel comfortable expressing themselves.
Encourage Expression:
Enable children to articulate their thoughts, feelings, and experiences.
Promote Emotional Understanding:
Help children identify and understand their own emotions and the emotions of others.
Enhance Listening Skills:
Develop children’s ability to listen attentively and respond appropriately.
Foster Positive Relationships:
Strengthen the bond between children and caregivers, peers, and other adults.
Support Learning and Development:
Aid cognitive and language development through engaging and meaningful conversations.
Teach Social Skills:
Encourage polite, respectful, and empathetic interactions with others.
Resolve Conflicts:
Provide tools and guidance for children to handle disagreements constructively.
Encourage Independence:
Support children in making decisions and solving problems on their own.
Provide Reassurance and Comfort:
Offer comfort and understanding during times of distress or uncertainty.
Reinforce Positive Behavior:
Acknowledge and encourage positive actions and behaviors.
Guide and Educate:
Offer clear instructions and explanations to help children understand expectations and learn new concepts.
By focusing on these objectives, communication with children can be both effective and nurturing, supporting their overall growth and well-being.
Digital Health in India_Health Informatics Trained Manpower _DrDevTaneja_15.0...DrDevTaneja1
Digital India will need a big trained army of Health Informatics educated & trained manpower in India.
Presently, generalist IT manpower does most of the work in the healthcare industry in India. Academic Health Informatics education is not readily available at school & health university level or IT education institutions in India.
We look into the evolution of health informatics and its applications in the healthcare industry.
HIMMS TIGER resources are available to assist Health Informatics education.
Indian Health universities, IT Education institutions, and the healthcare industry must proactively collaborate to start health informatics courses on a big scale. An advocacy push from various stakeholders is also needed for this goal.
Health informatics has huge employment potential and provides a big business opportunity for the healthcare industry. A big pool of trained health informatics manpower can lead to product & service innovations on a global scale in India.
Michigan HealthTech Market Map 2024. Includes 7 categories: Policy Makers, Academic Innovation Centers, Digital Health Providers, Healthcare Providers, Payers / Insurance, Device Companies, Life Science Companies, Innovation Accelerators. Developed by the Michigan-Israel Business Accelerator
The Importance of Black Women Understanding the Chemicals in Their Personal C...bkling
Certain chemicals, such as phthalates and parabens, can disrupt the body's hormones and have significant effects on health. According to data, hormone-related health issues such as uterine fibroids, infertility, early puberty and more aggressive forms of breast and endometrial cancers disproportionately affect Black women. Our guest speaker, Jasmine A. McDonald, PhD, an Assistant Professor in the Department of Epidemiology at Columbia University in New York City, discusses the scientific reasons why Black women should pay attention to specific chemicals in their personal care products, like hair care, and ways to minimize their exposure.
NURSING MANAGEMENT OF PATIENT WITH EMPHYSEMA .PPTblessyjannu21
Prepared by Prof. BLESSY THOMAS, VICE PRINCIPAL, FNCON, SPN.
Emphysema is a disease condition of respiratory system.
Emphysema is an abnormal permanent enlargement of the air spaces distal to terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis.
Emphysema of lung is defined as hyper inflation of the lung ais spaces due to obstruction of non respiratory bronchioles as due to loss of elasticity of alveoli.
It is a type of chronic obstructive
pulmonary disease.
It is a progressive disease of lungs.
Sectional dentures for microstomia patients.pptxSatvikaPrasad
Microstomia, characterized by an abnormally small oral aperture, presents significant challenges in prosthodontic treatment, including limited access for examination, difficulties in impression making, and challenges with prosthesis insertion and removal. To manage these issues, customized impression techniques using sectional trays and elastomeric materials are employed. Prostheses may be designed in segments or with flexible materials to facilitate handling. Minimally invasive procedures and the use of digital technologies can enhance patient comfort. Education and training for patients on prosthesis care and maintenance are crucial for compliance. Regular follow-up and a multidisciplinary approach, involving collaboration with other specialists, ensure comprehensive care and improved quality of life for microstomia patients.
This particular slides consist of- what is hypotension,what are it's causes and it's effect on body, risk factors, symptoms,complications, diagnosis and role of physiotherapy in it.
This slide is very helpful for physiotherapy students and also for other medical and healthcare students.
Here is the summary of hypotension:
Hypotension, or low blood pressure, is when the pressure of blood circulating in the body is lower than normal or expected. It's only a problem if it negatively impacts the body and causes symptoms. Normal blood pressure is usually between 90/60 mmHg and 120/80 mmHg, but pressures below 90/60 are generally considered hypotensive.
2. CONTENTS
X-ray machine
Production of X-rays
Factors controlling the X-ray beam
Tube current
Tube voltage
Exposure time
Filtration
Collimation
Inverse square law
Interaction of X-rays with matter
Coherent scattering
Photoelectric effect
Compton effect
References
3. QUESTIONS
X-ray machine (Manipal 2011 )
Draw the labeled diagram of x-ray tube & expalin the
functions of each component (DA 2014)
Filtration & collimation of diagnostic x-ray machine ( Amrita
2014 )
Production of x-rays. (PAHER 2016 ,Manipal 2010 )
Factors controlling the X-ray beam (DA 2016 )
4. X-rays are produced by the sudden deceleration or stoppage of
a rapidly moving stream of electrons at a metal target in a high
vaccum tube.
X-ray tube is an important part of any X-ray machine.
Dental X-ray machine is made up of three parts or components:
i. Control panel
ii. Extension arm
iii. Tube head
5. CONTROL PANEL
Control panel of the dental X-ray
machine contains-
a. An on and off switch & an
indicator light.
b. An exposure button .
c. Control device( time, kvp, mA
selectors) to regulate the X-ray
beam.
6. EXTENSION ARM
It contains electrical wires that extend
from control panel to the tube head.
It also allows the movement and
positioning of the tube head .
7. TUBE HEAD
It is a tightly sealed, heavy metal housing that contains:
-Metal body that surrounds the x-ray tube
-Insulating oil
-Tube head seal
-X-ray tube
-Aluminium disks
-Lead collimator
-Position indicating
device
8. Metal Housing: This is the metal body of the tube head that
surrounds the X-ray tube and transformer and is filled with oil, it
protects the X-ray tube and ground the high voltage component.
o Insulating Oil: It is that which surrounds the X-ray tube and
transformer inside the tube head, it prevents over heating by
absorbing the heat created by the production of X-rays
9. Tube Head Seal: Aluminum or leaded glass of the tube
head that permits the exit of X-rays from the tube head, it
seals the oil in the tube head and acts as a filter to the X-
ray beam
X-ray Tube : It is the main X-ray generating system.
10. Aluminum disks – the sheet of 0.5mm thick aluminum is
placed in the path of the X-ray beam.
It filters the non-penetrating, longer wavelength X-rays which
results in a higher energy & more penetrating useful beam,
which is less harmful to patients.
2 types of filtration
- inherent filtration
- added filtration
11. INHERENT FILTRATION
It takes place when the primary beam passes through the
glass window of the x-ray tube, the insulating oil and
the tube head seal.
It is approximately 0.5 to 1mm thickness of aluminum.
12. ADDED FILTRATION
Placement of aluminum disks in the path of the x-ray beam
between the collimator and the tube head seal.
Aluminum disks may be added in 0.5 mm increments.
Total filtration (inherent + added filtration) is regulated by
the state and federal law (in USA).
13. Dental machines operating:
At or below 70 kvp require a minimum total filtration of
1.5 mm of aluminum thickness.
Above 70 kvp require a minimum total filtration of 2.5
mm of aluminum thickness.
14. LEAD COLLIMATOR
It is a lead plate with a central hole that fits directly over
the opening of the metal housing where the x-ray exits.
Used to restrict the size and shape of the x-ray beam and
thus reduce exposure to the patients.
Collimator is of two types:
Fixed
Adjustable
15. In the dental X-ray machine usually the fixed
collimators are used, they may either have a round or
rectangular opening.
A rectangular collimator restricts the size of the X-ray
beam to an area slightly larger than a size of 2 intraoral
(normal adult intraoral periapical films) and thus
significantly reduces the patient exposure.
16. A circular collimator produces a cone shaped beam that
is 2.75 inches in diameter and is considerably larger than
the size of two intraoral periapical films, and thus leads
to an increased skin dose to the patient.
17. POSITION INDICATING DEVICE
Open end lead cylinder
Extend from the opening of metal housing of the tube head also
called as “ cone”.
It appears as an extension of the tube head; it aims and shapes
the X-ray beam.
There are three types of PIDs-
i. Conical
ii. Rectangular
iii. round
18. Both rectangular and round PIDs are available in two
lengths:
i. Short(8 inches)
ii. Long(16 inches)
19. X-RAY TUBE
Design introduced by W.Coolidge in 1913
An x-ray tube is composed of a cathode and an anode situated
within an evacuated glass envelope or tube Electrons stream
from a filament in the cathode to a target in the anode, where
they produce x rays.
20. For the x-ray tube to function, a power supply is
necessary to
(1) Heat the cathode filament to generate electrons
(2) Establish a high-voltage potential between the anode
and cathode to accelerate the electrons toward the
anode.
21. CATHODE
It is principally composed of two parts:
a. Filament
b. Focussing cup
It is the source of electrons in the tube, made up of a tungsten
wire
Diameter – 0.2cm
Width – 1-2 cm
Thickness- 0.1-0.2 mm
Length – 7- 15 mm
22. It is mounted on two stiff wires that support it and carry the
electric current.
These two mounting wires lead through the glass envelope and
connect to both the high- and low-voltage electrical sources.
The filament is heated to incandescence by the flow of current
from the low-voltage source and emits electrons at a rate
proportional to the temperature of the filament
23. FOCUSING CUP
It is a negatively charged concave reflector cup of molybdenum
or nickel and houses the filament.
The focal spot - The focusing cup parabolic shape
electrostatically focuses the electrons emitted by the filament
into a narrow beam, directed at a small rectangular area in the
anode.
24. The electrons move in this direction because they are both
repelled by the negatively charged cathode and attracted to the
positively charged anode.
The x-ray tube is evacuated to prevent collision of the fast-
moving electrons with gas molecules, which would significantly
reduce their speed.
The vacuum also prevents oxidation, “ burnout, ” of the filament.
25. ANODE
It consist of a wafer thin tungsten plate embedded in a solid
copper stem.
Target:
• Function is to convert the kinetic energy of electrons into x-ray
photons
• Inefficient process & more than 99% of energy is converted
into heat.
Copper – Good thermal conductor, dissipates heat from tungsten ,
reduces risk of target melting
26. Why is Tungsten used?
oHigh atomic number (74)
oHigh melting point (3422 ̊ C) – can be raised to high
temperature without detriment
High thermal conductivity(173 W ) thus readily dissipating its
heat into the copper stem.
Low vapor pressure - low vapor pressure of tungsten at high
temperatures helps maintain the vacuum in the tube at high
operating temperatures.
28. STATIONARY ANODE
Small plate of tungsten embedded in a large mass of Copper
Helps in heat dissipation from small focal spot.
29. ROTATING ANODE
A large disc of tungsten/alloys of tungsten, which theoretically
rotates at speed of about 3000 rpm
Used in tomographic or cephalometric units
Used in medical x-ray machines requiring high radiation
outputs
30. FOCAL SPOT
Focal spot is the area on target to which the focusing cup
directs the electrons from the filament
It is the region where X-rays & the heat are produced
Heat generated per unit target area becomes greater as the focal
spot decreases in size.
To take advantage of small focal spot along with proper heat
dissipation, target is placed at an angle with respect to electron
beam in the tube.
31. LINE FOCUS PRINCIPLE
o The Benson line focus principle developed in 1918 is a method
of reducing the effective focal spot size.
o Target is inclined about 17°-20° to central ray of x-ray beam
o Use of an anode with the target angulated such that the effective
focal spot is smaller than the actual focal spot size.
32. oProjection of focal spot perpendicular to electron beam is
effective focal spot
oActual focal spot is projected perpendicular from target
oActual focal spot = 1x 3 mm, Effective focal spot = 1x 1 mm
33. HEEL EFFECT:
• Intensity of the beam is not
uniform across the exposure
field
• Cathode side of the beam is
more intense than the anode
side because of self-absorption
of some of photons in the target
itself.
34. Effect arises because x-rays are generated at a small
depth inside the target and target surface gets rough with
use, therefore attenuation.
35. ELECTRICAL CIRCUIT OF THE X-RAY UNIT
Electrical Current: Refers to the flow of electrons through the
conductor
Direct Current: When the electrons flow in one direction
through the conductor
Alternating Current: Electrical current in which electrons flow
in two, opposing directions
36. Rectification is the process of converting AC to DC
A rectifier essentially eliminates the –ve phase of the AC,
leaving the +ve phase to behave as DC
37. Most dental x-rays, the amount of heat produced at the
anode does not give rise to excessive electrons, when the
current changes its direction, there are no electrons at the
anode to travel back to the cathode, this half of the cycle
is called inverse voltage, hence the dental x-ray tube is
called self or half wave rectifying.
38. Amperage- is the measurement of the number of
electrons moving through a conductor.
Current- is measured in amperage or milli amperage.
If the mA increases, the number of electrons passing
through the cathode filament increases.
Voltage: Measurement of electrical force that causes
electrons to move from negative cathode to positive
anode.
39. After entering the x-ray machine housing, the electrical current
is directed into 2 transformers.
One of these transformers, step-up, increases the incoming
voltage into the range of thousands of volts or KV range (high-
voltage circuit)
Other transformer, step-down, decreases the incoming voltage
to 10V (low voltage circuit or filament circuit)
40. Filament circuit, using 10V, regulates the flow of electrical
current to the filament of the x-ray tube, & is controlled by the
mA settings
Filament current regulates the tube current which consists of
electrons flowing from negative cathode to positive anode
High voltage circuit then provides the high voltage required to
accelerate the electrons & to generate the x-rays & is regulated
by the kilovoltage settings
41. POWER SUPPLY
Primary functions are to :
Provide low-voltage current to heat filament by use of step-
down transformer
Generate high potential difference between anode and cathode
by use of high-voltage transformers
42. TRANSFORMERS
• Is a device that is used to either increase or decrease the
voltage in an electrical circuit
• 3 transformers are used to adjust the electrical circuit
-step-down transformer
-step-up transformer
-autotransformer
43. Step-down Transformer:
Used by the filament circuit.
It is used to decrease the voltage
from the incoming 110-220 line
voltage to 3-4V as required for the
filament circuit. (This transformer
has more coils in the primary coil
than in the secondary coil).
44. Step-up Transformer::
It is used to increase the voltage from the incoming 110-220 line
voltage to 65,000- 1,00,000 volts as required by the high voltage
circuit.
45. Autotransformer :
Converts primary voltage from the input source into secondary
voltage
Secondary voltage is regulated by kvp selector dial, selects
voltage from different levels on autotransformer and applies it
across primary winding of high-voltage transformer
Accelerates electrons from cathode to anode and generate x-
rays
46. A timing control device to control x-ray exposure time is
included in the primary circuit of the high voltage supply
47. TUBE RATING AND DUTY CYCLE
X- ray tubes produces heat at the target while in operation.
Heat buildup at the anode is measured in heat units(HU),
HU=kVp × mA × second
Heat storage capacity for anodes of dental dignostic tubes
is approx. 20 kHU.
Heat is removed by copper anode and then to the
surrounding oil and housing tube and by convection to the
atmosphere.
48. PRODUCTION OF X-RAYS
The kinetic energy of electrons is the tube current is converted
into x-ray photons at the focal spot of an X-ray tube by two
mechanisms :
1. Bremsstrahlung radiation
2. Characteristic radiation
49. BREMSSTRAHLUNG RADIATION
Bremstrahlung radiation, the primary source of X-ray photons
from an X-ray tube, is produced by
1.Direct hit of electron on nucleus in target – during this type of
collision all the kinetic energy of high speed electron will be
converted into single X-ray photon with maximum energy.
50. The energy of the resultant photons in units of kilo
electron volts is numerically equal to the energy of the
electron that is in turn equal to the kilovoltage applied
across the x-ray tube at the time of its passage.
51. 2. By passage of electron near nucleus, which results in electron
being deflected and decelerated. This deceleration causes it to
lose some of its kinetic energy. This energy is given off in the
form of a photon of electromagnetic radiation, which has an
energy equal to that lost by the deflected electron i.e. photon
of lower energy.
52. CHARACTERISTIC RADIATION :
Characteristic radiation occurs when
a bombarding electron of the tube
current displaces an electron from a
shell of a target atom, thereby
ionizing the atom.
Incident electron ejects photoelectron
from inner orbit, creating vacancy.
Inner vacancy is filled with electron
from outer orbit.
53. Photon is emitted with energy equal
to difference in energy levels of two
orbits.
Electrons from various orbits may be
involved, giving rise to other
photons.
Energies of photons thus created are
characteristic of target atomic
composition (i.e. energy levels of
various electron orbital levels).
54. Factors Controlling the X-ray Beam
Exposure Time (Timer)
Tube current (mA)
Tube Voltage Peak (kVp)
Filtration
Collimation
Inverse square law
55. EXPOSURE TIME
Exposure time(Timer) :
As exposure time increases, so does the total number of
photons, but the mean energy and maximal energy of the
beams the uncharged.
56. Tube current
Tube current (MA) : Quantity of radiation produced by an
x-ray tube (i.e. number of photons that reach the patient and
film) is directly proportional to tube current and time the
tube is operated.
57. Tube voltage
Tube Voltage (kvp) : As kvp is increased (with mA held
constant), a corresponding increase occurs in mean energy of
the beam, the total number of photons emitted, and maximal
energy of photons
Quantity of X-ray radiation is directly proportional to tube
current and exposure time
Quality of X-ray radiation is directly proportional to tube
voltage
58. Filtration :
The purpose of conventional filtration is to remove low
energy X-ray photons selectively from x-ray beam. This
results in decreased patient exposure with no loss of
radiologic information.
59. TOTAL FILTRATION:
Is sum of the inherent filtration plus any added external
filtration.
Governmental regulations require the total filtration in
path of a dental x-ray beam to be equal to equivalent of
1.5 mm of aluminium to 70 KVp 2.5 mm of aluminium
for all higher voltages
60. INHERENT FILTRATION :
Consists of materials that X-ray photons encounter as
they travel from the focal spot on the target to form the
usable beam outside the tube enclosure.
Inherent filtration of most X-ray machine ranges from
equivalent of 0.5 to 2 mm of aluminium.
61. Examples of inherent filtration are :
Glass wall of the X-ray tube.
Insulating oil that surrounds many dental tubes.
Barriers material that prevents oil from escaping
through the x-ray port.
62. EXTERNAL FILTRATION :
Aluminium disks placed over the port in the head of the
x-ray machine.
Aluminium wedge filter is a part of cephalostat.
63. COLLIMATION :
A collimator is a metallic barrier with an aperture in the
middle used to reduce the size of the x-ray beam and
therefore the volume of irradiated tissue within the
patient lese of collimation also improves image quality.
Dental x-ray beams are usually collimated to a circle 2¾
inches (7cm) in diameter.
64. TYPES OF COLLIMATORS :
Round Collimator : is a thick
plate of radiopaque material with
a circular opening centered over
the port in the x- ray head
.Round collimator are built into
open – ended aiming cylinders.
65. Rectangular Collimator : limits
the size of the beam to just
larger than the x- ray film,
thereby reducing patients
exposure
66. Intensity of a x-ray beam is
inversely proportional to the
square of distance between the
source and the point of measure
The relationship is follows
I1/I2 = (D2)2/(D1)
Where I is Intensity and D is
distance
Inverse Square Law :
67. INTERACTION OF X-RAYS WITH MATTER
Intensity of an X-ray beam is reduced by interaction with
the matter it encounters. X-ray photons are attenuated by
absorption and scattering of X-ray photons out of the
absorber as a result of interactions with the orbital
electrons of component atoms.
There are three mechanisms –
1. Coherent scattering
2. Photoelectric effect
3. Compton effect
68. COHERENT SCATTERING (THOMPSON EFFECT OR
CLASSIC SCATTERING)
Coherent scattering (also known as
classical, elastic , or Thompson
scattering) may occur when a low-
energy incident photon (less than 10
keV) passes near an outer electron
of an atom.
The incident photon interacts with
the electron by causing it to become
momentarily excited at the same
frequency as the incoming photon .
69. o The incident photon ceases to exist.
o The excited electron then returns to
the ground state and generates another
x-ray photon with the same frequency
(energy) as in the incident beam.
o Usually the secondary photon is
emitted at an angle to the path of the
incident photon.
oThe net effect is that the direction of
the incident x-ray photon is altered.
70. Coherent scattering accounts for only about 7% of the total
numberof interactions in a dental exposure Coherent scattering
contributes little to fi lm fog because the number of scattered
photons is small and their energy is too low for many of them
to reach the film or sensor.
71. COMPTON SCATTERING:
Or inelastic scattering is an
interaction of photons with
free or loosely bound outer
shell electron.
The photon gives some of its
energy to the electron and it,
itself continues in a new
direction, but with reduced
energy and hence with
increased wavelength.
72. The ejected outer shell electron
is called compton or recoil
electron.
If scattered through a small
angle, very small amount of
energy is lost to the outer
electron.
73. The recoil electrons further
ionizing interactions with the
tissues, and gradually lose
energy along their tracts by
causing secondary radiations and
consequent biological damage.
Due to their energy, rays can
emit photoelectrons from metals,
when allowed to fall on them.
74. PHOTOELECTRIC EFFECT:
It is a process of interaction of the incident photon and the
bound electron leading to emission of characteristic radiation.
It occurs when an incident photon collides with a bound
electron in the atom of the absorbing medium.
The incident photon ceases to exit and its energy helps to
eject a bound electron from its shell to become a recoil
electron or a photo electron.
75. The kinetic energy imparted to the recoil electron is equal to the
energy of the incident photon minus that required to overcome
the electron binding energy.
The orbital vacancy caused by the electron reshuffle and the
neutrality is obtained by attracting an electron from outside.
During this rearrangement characteristic radiation is emitted.
76. References
Text book of oral radiology -white & Pharoah 6thedition
Text book of oral radiology -Freny Karjodkar 1st edition
Text book of diagnostic radiology – cristensen’s 4th edition
Text book of oral radiology -Ghom