Computed radiography and digital radiography are two methods for obtaining digital x-rays. Computed radiography uses an imaging plate inside a cassette that captures x-rays, which are then digitized in a CR reader. Digital radiography uses a flat panel detector with either direct or indirect conversion of x-rays to electrical signals. Both methods provide advantages over conventional film such as faster workflow, ability to adjust images after exposure, and reduced radiation dose for patients.
This document discusses Computed Radiography (CR) and Digital Radiography (DR), which are two methods for obtaining digital x-rays. CR uses existing x-ray machines and captures images digitally using imaging plates, which store x-ray data that is later extracted digitally. DR uses direct or indirect flat panel detectors in digital x-ray machines to directly or indirectly convert x-rays into electronic signals. Both methods allow for digital image processing and eliminate the need for darkroom film processing.
This document discusses Computed Radiography (CR) and Digital Radiography (DR), which are two methods for obtaining digital x-rays. CR uses conventional x-ray machines along with imaging plates that store x-ray data digitally. DR uses digital x-ray machines with flat panel detectors that directly convert x-rays to electrical signals. Both methods provide advantages over conventional film such as improved image quality, reduced radiation dose and faster workflow.
Digital radiography uses either computed radiography (CR) or digital radiography (DR) to capture x-ray images digitally. CR uses an imaging plate inside a cassette that stores x-ray data, which is then processed digitally to produce high quality images. DR uses a flat panel detector that directly converts x-rays to electrical signals. Both techniques eliminate the need for film and allow for digital image manipulation, reduced radiation dose, improved workflow and easier storage compared to conventional film radiography.
The document discusses digital radiography, including computed radiography (CR) and direct radiography using flat panel detectors. It summarizes the limitations of conventional film-based radiography and then describes the key components and workings of CR and direct digital radiography systems. Some advantages include improved image quality, ability to manipulate images digitally, faster processing, and reduced need for retakes compared to conventional methods.
Computed radiography and digital radiography are two methods for obtaining digital x-rays. Computed radiography uses conventional x-ray machines and captures data using imaging plates, which are processed digitally to produce high quality images. Digital radiography uses flat panel detectors that directly or indirectly convert x-rays into electronic signals for digital images. Both techniques provide advantages over conventional film including improved image quality and workflow efficiencies.
Computed radiography and digital radiography are two methods for obtaining digital x-rays. Computed radiography uses an imaging plate inside a cassette that captures x-rays, which are then digitized in a CR reader. Digital radiography uses a flat panel detector with either direct or indirect conversion of x-rays to electrical signals. Both methods provide advantages over conventional film such as faster workflow, ability to adjust images after exposure, and reduced radiation dose for patients.
This document discusses Computed Radiography (CR) and Digital Radiography (DR), which are two methods for obtaining digital x-rays. CR uses existing x-ray machines and captures images digitally using imaging plates, which store x-ray data that is later extracted digitally. DR uses direct or indirect flat panel detectors in digital x-ray machines to directly or indirectly convert x-rays into electronic signals. Both methods allow for digital image processing and eliminate the need for darkroom film processing.
This document discusses Computed Radiography (CR) and Digital Radiography (DR), which are two methods for obtaining digital x-rays. CR uses conventional x-ray machines along with imaging plates that store x-ray data digitally. DR uses digital x-ray machines with flat panel detectors that directly convert x-rays to electrical signals. Both methods provide advantages over conventional film such as improved image quality, reduced radiation dose and faster workflow.
Digital radiography uses either computed radiography (CR) or digital radiography (DR) to capture x-ray images digitally. CR uses an imaging plate inside a cassette that stores x-ray data, which is then processed digitally to produce high quality images. DR uses a flat panel detector that directly converts x-rays to electrical signals. Both techniques eliminate the need for film and allow for digital image manipulation, reduced radiation dose, improved workflow and easier storage compared to conventional film radiography.
The document discusses digital radiography, including computed radiography (CR) and direct radiography using flat panel detectors. It summarizes the limitations of conventional film-based radiography and then describes the key components and workings of CR and direct digital radiography systems. Some advantages include improved image quality, ability to manipulate images digitally, faster processing, and reduced need for retakes compared to conventional methods.
Computed radiography and digital radiography are two methods for obtaining digital x-rays. Computed radiography uses conventional x-ray machines and captures data using imaging plates, which are processed digitally to produce high quality images. Digital radiography uses flat panel detectors that directly or indirectly convert x-rays into electronic signals for digital images. Both techniques provide advantages over conventional film including improved image quality and workflow efficiencies.
Digital imaging involves capturing radiographic images digitally using various methods like computed radiography (CR), direct radiography (DR), or scan projection radiography (SPR). CR uses photostimulable phosphor plates while DR uses flat panel detectors, eliminating processing. Digital imaging provides advantages like improved image manipulation, reduced radiation exposure, and improved storage and sharing of images. Key types of digital radiography discussed are CR, DR, SPR, digital fluoroscopy, and digital subtraction angiography (DSA).
Different types of imaging devices and principles.pptxAayushiPaul1
Digital radiography uses digital image receptors instead of film. Large digital radiographic images require significant storage space, network bandwidth, and high-resolution monitors. Picture archiving and communication systems (PACS) provide economical storage and access to medical images across systems using DICOM standards. Common digital x-ray technologies include computed radiography, direct radiography using CCDs or flat panel detectors, and direct detection flat panel systems which directly convert x-rays to electron-hole pairs.
Wilhelm Roentgen discovered X-rays in 1895 while experimenting with cathode ray tubes. He observed that a screen coated with barium salt would fluoresce when placed near the tube, even though the tube was covered. This led him to conclude that a new type of penetrating radiation was being emitted. The first medical X-ray image ever taken was of Roentgen's wife's hand.
X-rays are a type of electromagnetic radiation that is able to pass through and penetrate materials like human tissue. They are used widely in medical imaging procedures. Digital radiography systems like computed radiography and digital radiography have largely replaced traditional film-based X-ray systems, allowing for the digital capture, processing,
DIGITAL RADIOGRAPHY FOR bachelor of science in medical imaging technologyDilshanDillu1
Digital radiography (DR) produces digital radiographic images instantly on a computer using x-ray sensitive plates that capture data during examinations. DR systems use detectors that convert x-ray signals into electronic signals, which are then converted into digital signals. There are two main types of DR - computed radiography which uses photo-stimulable phosphor plates, and direct radiography which uses detectors like amorphous selenium for direct conversion of x-rays to digital signals. Recent advances in DR include dual energy imaging, computer-aided detection, and mobile DR systems.
This document provides an overview of digital radiography and compares computed radiography (CR) and direct digital radiography (DR) systems. It discusses the limitations of traditional film screen radiography including limited dynamic range and inability to manipulate images. For CR, it describes the use of storage phosphor plates which capture x-ray information for later readout and digitization. For DR, it explains direct and indirect conversion panels used to directly convert x-rays to electrical signals. Key advantages of digital systems include immediate image viewing, manipulation, and storage without chemical processing.
This document provides an overview of x-ray machines and their components and uses. It discusses the history of x-rays and their discovery in 1895. The main components of an x-ray machine are described, including the high voltage generator, control panel, x-ray tube, collimator, grid, and film or digital sensor. Different types of x-ray machines are examined, such as conventional, computed radiography, and digital radiography systems. Factors that affect image quality like kilovoltage, milliamperes, and distance are outlined. The document also reviews exposure dose limits and protective procedures for radiation workers.
- Digital radiography involves capturing a radiographic image using an intraoral sensor, converting it to electronic data, and storing/viewing it on a computer.
- There are three main methods of digital imaging: direct digital imaging using an intraoral sensor, indirect using digitization of films, and storage phosphor imaging using reusable plates.
- DICOM is the international standard for transferring digital medical images and communication between devices. It allows images captured on one device to be viewed on another regardless of manufacturer.
- Digital images have advantages over film such as modification capabilities, electronic storage/transfer, and reduced radiation exposure.
Digital radiography has evolved significantly since the 1970s. Computed radiography (CR) was developed in the 1980s using storage phosphor plates to capture latent images, which are then read by a scanner. Direct radiography (DR) systems developed later, directly producing digital images without needing to remove plates from cassettes. DR uses indirect conversion with scintillator layers or direct conversion using photoconductive materials. Both produce digital images but DR allows more rapid viewing and higher throughput.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
Computed radiography (CR) uses reusable imaging plates and associated hardware and software to acquire and display digital x-ray images as an alternative to traditional film-based radiography. The document provides an overview of the key components of a CR system, including the imaging plate, reader/digitizer, and workstation. It describes how a latent image is captured and stored in the phosphor plate from x-ray exposure, then stimulated and converted to a digital image by the reader using a laser. The advantages of CR over conventional radiography are also summarized, such as reusability of plates and improved image manipulation, storage and sharing capabilities.
Computed radiography and digital radiography- CR/DRAshim Budhathoki
This document provides an overview of computed radiography (CR). It discusses the history and components of CR, including imaging plates, digitizers, and printers. The working mechanism is explained, from image acquisition using an imaging plate exposed to X-rays, to laser scanning to release photons detected by a photomultiplier tube and digitized to form the image. Advantages include comparable image quality to film and ability to process images digitally. The document also compares CR to conventional X-ray and digital radiography.
The document discusses the history and evolution of radiography technology from analog film-based systems to current digital systems. It provides details on the key steps in computed radiography (CR) where imaging plates capture x-ray data which is then digitally processed to create images. CR involves separate image capture and readout processes. The document also describes direct digital radiography (DR) systems which integrate image capture and readout using flat panel detectors, thereby providing a cassette-less workflow. Overall, the document provides an overview of modern digital radiography techniques and their advantages over conventional film-based systems.
The document summarizes the process of computed radiography (CR), which uses an imaging plate rather than film. When exposed to X-rays, the phosphor layer in the imaging plate absorbs the radiation and excites electrons. These trapped electrons remain until stimulated by a laser during readout. The plate is scanned by a laser, causing the electrons to release light detected by a photomultiplier tube. This signal is converted to a digital image. After scanning, the plate is erased using light to remove any remaining electrons for future exposures. CR provides benefits over film such as dose reduction and improved image quality.
Computed radiography uses image plates containing photostimulable phosphor to digitally capture x-ray images. The image plate is exposed in the cassette, retaining a latent image. This image is released and converted to light when scanned by a laser, and detected to generate a digital image file. Key advantages include reduced failed exposures, cassette-based mobility, and reusable image plates. Disadvantages include potentially lower resolution than film and longer image read-out times.
Digital imaging systems like photostimulable storage phosphor (PSP) plates, flat panel detectors with thin film transistors (FPD-TFT), and charged couple devices (CCD) have created misconceptions due to their various acronyms and designs. PSP plates capture and store x-ray exposure electrons, which are released as light during reading and converted to digital images. FPD-TFT systems directly capture electrons using amorphous selenium or silicon and thin film transistors. CCD systems use scintillators to convert x-rays to light, which is focused onto CCDs and converted to electrons and digital images. Regardless of appearance or how images are captured, all digital systems have a
This document provides an overview of digital radiography, including its history and key components. Digital radiography converts analog X-ray images to digital files using various detection methods. These include computed radiography using photostimulable phosphor plates, as well as direct digital radiography techniques like CCD and flat panel detectors that directly capture X-ray data without image plates. The digital files then undergo processing to enhance image quality and enable analysis.
This document discusses radiography testing principles and techniques. It describes how radiography uses X-rays to detect internal defects by passing X-rays through a material and capturing the transmitted image on film. It discusses different film and filmless techniques like computed radiography and computed tomography. It also covers topics like image quality indicators and the wide applications of radiography testing in inspecting various materials and components.
Computed Radiography and digital radiographyDurga Singh
This document provides an overview of a seminar on Computed Radiography (CR) and Digital Radiography (DR). CR involves capturing x-ray data digitally using an imaging plate, which stores radiation exposure information that is later read out by a laser and processed into an image. DR directly converts x-rays to a digital signal using a detector connected to a computer. The seminar discusses the components, principles, workings, advantages and disadvantages of each technology. It describes how CR imaging plates use photostimulated luminescence and how digital images are produced during plate reading.
The document discusses various digital x-ray imaging technologies including computed radiography (CR), charge-coupled device (CCD) detectors, flat panel detectors using thin-film transistor (TFT) arrays, and scintillator-based indirect detection systems. CR uses photostimulable phosphor plates that store x-ray energy, which is later read out using laser stimulation to produce a digital image. Flat panel detectors directly convert x-rays to electrical signals or use indirect conversion with scintillators. Technique factors like voltage, current and exposure time affect image quality and patient dose in digital radiography.
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Wilhelm Roentgen discovered X-rays in 1895 while experimenting with cathode ray tubes. He observed that a screen coated with barium salt would fluoresce when placed near the tube, even though the tube was covered. This led him to conclude that a new type of penetrating radiation was being emitted. The first medical X-ray image ever taken was of Roentgen's wife's hand.
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This document provides an overview of digital radiography and compares computed radiography (CR) and direct digital radiography (DR) systems. It discusses the limitations of traditional film screen radiography including limited dynamic range and inability to manipulate images. For CR, it describes the use of storage phosphor plates which capture x-ray information for later readout and digitization. For DR, it explains direct and indirect conversion panels used to directly convert x-rays to electrical signals. Key advantages of digital systems include immediate image viewing, manipulation, and storage without chemical processing.
This document provides an overview of x-ray machines and their components and uses. It discusses the history of x-rays and their discovery in 1895. The main components of an x-ray machine are described, including the high voltage generator, control panel, x-ray tube, collimator, grid, and film or digital sensor. Different types of x-ray machines are examined, such as conventional, computed radiography, and digital radiography systems. Factors that affect image quality like kilovoltage, milliamperes, and distance are outlined. The document also reviews exposure dose limits and protective procedures for radiation workers.
- Digital radiography involves capturing a radiographic image using an intraoral sensor, converting it to electronic data, and storing/viewing it on a computer.
- There are three main methods of digital imaging: direct digital imaging using an intraoral sensor, indirect using digitization of films, and storage phosphor imaging using reusable plates.
- DICOM is the international standard for transferring digital medical images and communication between devices. It allows images captured on one device to be viewed on another regardless of manufacturer.
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Digital radiography has evolved significantly since the 1970s. Computed radiography (CR) was developed in the 1980s using storage phosphor plates to capture latent images, which are then read by a scanner. Direct radiography (DR) systems developed later, directly producing digital images without needing to remove plates from cassettes. DR uses indirect conversion with scintillator layers or direct conversion using photoconductive materials. Both produce digital images but DR allows more rapid viewing and higher throughput.
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Computed radiography (CR) uses reusable imaging plates and associated hardware and software to acquire and display digital x-ray images as an alternative to traditional film-based radiography. The document provides an overview of the key components of a CR system, including the imaging plate, reader/digitizer, and workstation. It describes how a latent image is captured and stored in the phosphor plate from x-ray exposure, then stimulated and converted to a digital image by the reader using a laser. The advantages of CR over conventional radiography are also summarized, such as reusability of plates and improved image manipulation, storage and sharing capabilities.
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This document provides an overview of computed radiography (CR). It discusses the history and components of CR, including imaging plates, digitizers, and printers. The working mechanism is explained, from image acquisition using an imaging plate exposed to X-rays, to laser scanning to release photons detected by a photomultiplier tube and digitized to form the image. Advantages include comparable image quality to film and ability to process images digitally. The document also compares CR to conventional X-ray and digital radiography.
The document discusses the history and evolution of radiography technology from analog film-based systems to current digital systems. It provides details on the key steps in computed radiography (CR) where imaging plates capture x-ray data which is then digitally processed to create images. CR involves separate image capture and readout processes. The document also describes direct digital radiography (DR) systems which integrate image capture and readout using flat panel detectors, thereby providing a cassette-less workflow. Overall, the document provides an overview of modern digital radiography techniques and their advantages over conventional film-based systems.
The document summarizes the process of computed radiography (CR), which uses an imaging plate rather than film. When exposed to X-rays, the phosphor layer in the imaging plate absorbs the radiation and excites electrons. These trapped electrons remain until stimulated by a laser during readout. The plate is scanned by a laser, causing the electrons to release light detected by a photomultiplier tube. This signal is converted to a digital image. After scanning, the plate is erased using light to remove any remaining electrons for future exposures. CR provides benefits over film such as dose reduction and improved image quality.
Computed radiography uses image plates containing photostimulable phosphor to digitally capture x-ray images. The image plate is exposed in the cassette, retaining a latent image. This image is released and converted to light when scanned by a laser, and detected to generate a digital image file. Key advantages include reduced failed exposures, cassette-based mobility, and reusable image plates. Disadvantages include potentially lower resolution than film and longer image read-out times.
Digital imaging systems like photostimulable storage phosphor (PSP) plates, flat panel detectors with thin film transistors (FPD-TFT), and charged couple devices (CCD) have created misconceptions due to their various acronyms and designs. PSP plates capture and store x-ray exposure electrons, which are released as light during reading and converted to digital images. FPD-TFT systems directly capture electrons using amorphous selenium or silicon and thin film transistors. CCD systems use scintillators to convert x-rays to light, which is focused onto CCDs and converted to electrons and digital images. Regardless of appearance or how images are captured, all digital systems have a
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2. Presentation Layout
• Introduction & History of Digital Radiography
• Terminologies related to DR
• Principle & Types of DR
• Computed Radiography
• Scanned Projection Radiography
• Direct Digital Radiography
• Direct & Indirect DDR
• Advancements in CR & DR
• Detectors used in TUTH
3. Conventional Radiography
• Uses film and IS in its image formation process.
• X-rays pass through the patient and expose the film,
creating latent image.
• Involves chemical processing to reveal the image on X-
ray film.
• It had limited manipulation options after film
processing.
4. Introduction to Digital Radiography
• Filmless imaging system
• Digital X-ray sensors are used instead of
traditional photographic films.
• Concept given by Albert Jutras [
1950,Canada] during his experimentation
with teleradiology.
• First DR application is the invention of CT
in 1967 by Godfrey Hounsfield
5. History of Digital Radiography
YEAR TECHNIQUE
1977 Introduction of DSA
1978 DSA first put into clinical use
1980 Use of storage phosphor image plates
1987 Amorphous selenium based image plates
1990 Charged couple device slot-scan DR was introduced
1994 Selenium drum DR
1995 Amorphous silicon CSI flat panel detector
1997 Gd based FPD
2001 Gd based portable FPD
2001 Dynamic FPD fluoroscopy DSA
2007 Portable CR system
6. Terminologies related to DR
1. Pixel: short for “picture element”. Small, discrete units of digital information that
together constitute an image.
2. Resolution: level of clarity or detail in an image.
3. Gray Scale: refers to total no. of shades of gray visible in an image
4. Voxel: Volume element. A 3-Dimensional element that includes depth. A pixel is
essentially the end of the voxel.
7. Components of Digital Imaging
1. Capture element: Component in which the X- ray is captured. In CR, it is PSP
& in DR it may be CsI, Gd-OS or a-Se.
2. Coupling element: It transfers x-ray generated signal to the collection
element. It may be a lens or fiber optic assembly, a contact layer or a-Se.
3. Collection element: may be a photodiode, CCD or TFT. The photodiode &
CCD are light-sensitive whereas TFT is charge sensitive.
8. PRINCIPLE Of DR
• The digital detector is exposed to X-rays generated by a standard tube.
• The energy absorbed by the detector is transformed into electrical charges,
which are then recorded, digitized and quantified into a gray scale.
• After sampling, post-processing software is required for organizing the raw data
into a clinically meaningful image.
9. Types of Digital Radiography
FIG:- An organizational scheme for digital radiography
10. Computed Radiography (CR)
• Records radiographic images on
photostimulable phosphor plates instead
of film/screen image receptors and the
image is acquired in digital Form.
• Based on the principle of Photo-
stimulable Luminescence.
• The commonly used phosphor is barium
fluorohalides: BaFBr (85%) and BaFI
(15%):with Eu (europium).
11. CONTD..
• The PSP plates are placed inside a special cassette for exposure.
• During exposure , x-ray energy is absorbed temporarily in the PSP crystal by bringing
electrons to higher energy levels.
• Cassette is placed in a reader(Digitizer) to capture and analyze the image data.
• Uses a computer workstation and viewing station and a printer.
• CONSISTS OF :-
1. CASSETTE
2. IMAGING PLATE
3. READER
12. CR: Cassette
• Looks like conventional radiography cassette.
• Consists of durable, lightweight plastic material.
• Consists of 150µ lead for backscatter protection.
• Instead of IS, there is antistatic material that protects against static electricity
build up, dust collection and mechanical damage to plate.
14. CR: Imaging Plate (IP)
• First introduced by Fuji, Japan, in 1983 and is
similar to that of a screen-film cassette.
• Responsible for capturing the X-ray image.
• They are made up of Photostimulable
phosphor(PSP).
• PSPs, barium flurohalide, is fashioned
similarly to a radiographic IS.
• Since latent image occurs in form of
metastable electrons, such screens are called
Storage phosphor screen (SPSs).
IP
15. Layers of IP
PROTECTIVE LAYER :
• a very thin, tough, clear plastic that protects the phosphor layer.
PHOSPHOR LAYER:
• consists of photostimulable phosphor that traps electrons during exposure. Usually made up of BARIUM
FLUROHALIDE family.
LIGHT REFLECTIVE LAYER:
• It sends light in a forward direction when released in the cassette reader. Maybe black to reduce the
spread of stimulating light and escape of emitted light.
CONDUCTIVE LAYER:
• This layer grounds the plate to reduce static electricity problems and to absorb light to increase
sharpness.
16. SUPPORT LAYER :
• Semirigid layer that provides strength.
LIGHT SHEILDING LAYER
BACKING LAYER
• Soft polymer that protects back of cassette.
BAR CODE LABEL :
• Used in matching and identification
FIG:- A showing the Imaging plate, B showing it’s construction
17. What happens in the IP?
• When x ray is exposed, x-ray energy is absorbed by BaFBr phosphor.
• Absorbed energy causes the divalent Europium atoms to be oxidized and changed into
trivalent state.
• The exited e-s becomes mobile & interact with F-center
• The F-center traps these e-s in a higher energy meta-stable state in the form of latent
image.
• During this process , about 50% of the e-s returns to the ground state immediately
• However , the remaining meta-stable e-s also returns to the ground state over time.
This causes the latent image to fade and the IP must be read soon after exposure.
18. CR: Reader
The CR reader represent the
mechanical, optical and
computer modules.
19. CR: Reader (Mechanical features)
• When the CR cassette is inserted into the CR reader , the
IP is removed & is fitted to a precision drive mechanism.
• The drive mechanism moves the IP slowly along the long
axis of the IP, known as slow scan mode.
• A deflection device deflects the laser beam back & forth
across the IP which is called fast scan mode.
20. CR: Reader (Optical features)
• It precisely interrogate each meta-stable e-s of the latent image in the precise
fashion.
• Its components include the laser, beam-shaping optics, light-collecting optics,
optical filters & a photodetector.
• The He-Ne gas laser is the source of stimulating light which is monochromatic.
• The gas laser has been largely replaced by the solid state laser which produces
the light of longer wavelength which are less likely to interfere with emitted light.
21. • The light beam is focused into the reflector by a lens
system that keeps the beam diameter small (less than
100micrometer).
• Smaller the laser beam size , higher the spatial resolution
of the image.
• Emitted light is focused by fiber optic collection assembly
& is directed at the photodetector, PMT, or CCD.
• Before photo-detection , the light is filtered so that none
of the long-wavelength stimulation light reaches the
photo-detector. Filtering improves SNR.
22. CR: Reader (Computer control)
• The output of the photodetector is a time varying analog signal that is transmitted to a
computer system.
• This shapes the signal before the final image is formed.
• Then, the analog signal is digitized with the help ADC
• The computer of the CR reader is in control of the slow scan & the fast scan.
23. CR: Reader
WORKING:-
The IP is mechanically removed from the cassette when it moved into the reader.
The IP is translated across the readout stage in the vertical direction (y-direction) & the
scanning laser beam interrogates the plate horizontally (x-direction).
As the red laser light strikes the IP at the location (x , y) , the trapped energy is released
from it in the form of light which is of different colors than stimulating laser light.
A fraction of emitted light travels through the fiber-optic light guide & reaches the PMT
24. CR: Reader
WORKING:-
The electronic signal that is produced by PMT is
digitized & stored in the memory.
Therefore for every location (x , y) , a corresponding
gray scale value is determined & thus digital image
is produced.
The plate is then exposed to bright white light to
erase any residual trapped energy and returned to
the cassette for reuse.
This whole process takes typically about 30-90
seconds in most of the systems.
25. Advantages of CR
• Faster image receptor , so lower patient dose is possible.
• High image quality compared to conventional film screen system
• Post- processing , manipulation & storage of images.
• Repeat examinations are reduced due to wide exposure latitude.
• IP is reusable , no need to reload the cassette.
• Compatible with most conventional x ray unit and therefore be introduced without the need
to replace existing equipment
26. Disadvantages of CR
• High equipment cost.
• Long time to view image.
• Spatial resolution is usually lower than that with conventional screen film
radiography.
27. Scanned Projection Radiography
• Developed by CT vendors to facilitate patient
positioning after the introduction of 3rd gen CT
scanners.
• Basically, dedicated for chest DR.
WORKING :-
• The method consists of placing the x-ray tube and
detector assembly in such a position that the
patient may be moved linearly through the x-ray
beam
• As it is moved, data are collected by the
computer from the detector array, and the image
of the patient is thus stored in computer memory
for subsequent manipulation and display.
Fig:- A scanned projection radiograph obtained in
computed tomography by maintain the energized
X-ray tube- detector array fixed while the patient is
translated through the gantry
28. • This system is based on the well collimated
narrow fan beam
corresponds to the detector array.
• SPR uses the CT- gantry & computer to produce
an image that
looks like conventional radiography.
ADVANTAGES
- High image contrast
- Wide dynamic range
- Post processing
DISADVANTAGES
-Exposure time is long
-Poor spatial resolution
-Radiation dose is more
Fig:- A scanned projection radiograph of the
Entire trunk of the body obtained in computed
tomography
29. Direct Digital Radiography
• Direct digital radiography, a term used to describe total electronic image capturing.
• Eliminates the need for an image plate altogether.
• It’s of two types:-
1. DIRECT CONVERSION TYPE:- Photoconductors like amorphous selenium directly convert
X-rays into electrical charges. Flat panel based
2. INDIRECT CONVERSION TYPE:- It involves two steps-
-X-ray to visible light conversion by scintillator
- Visible light to charges by photo detectors
- CCD/CMOS based, Flat panel
30. CONTD..
Scintillator :- material that exhibits scintillation , the property of luminescence,
when excited by ionizing radiation.
• Types :-
1. Unstructured scintillator: With use of unstructured scintillator, the visible light
emitted by the material can spread to adjacent pixels, thereby reducing spatial
resolution.
2. Structured scintillators: To reduce the problem of scatter, some manufacturers
now use a structured scintillator that consists of cesium iodide crystals that are
grown on the detector
31. CONTD..
• Thallium-doped cesium iodide (CsI) is the most commonly used phosphor
material.
• Another material that is used is gadolinium oxysulphide or Gadox (Gd2 O2S).
• CsI - based detectors are more efficient in X-ray absorption than gadox detectors
and have better DQE
33. Photomultiplier Tube
• Type of photo- detectors and are highly light - sensitive device especially whose
wavelength lies in range of UV, Visible & IR region of Electromagnetic Spectrum.
• These detectors amplify the current produced by incident photon by as much as 100
million times , through series of dynodes when the incident flux of light is very low.
• Their operation depends on two processes:-
- Photoelectric effect
- Secondary Emission
34. PMT
• A photomultiplier consists of five main parts:
1. A cathode which is coated with a material of
low work function
2. An anode to collect electrons
3. A series of dynodes between the cathode and
the anode
4. An external power supply which produces an
electric field between the cathode and first
dynode, between the dynodes, and between
the last dynode and the anode.
5. An external current meter to measure the
number of electrons collected at the anode,
and a recorder to collect the information.
36. Photodiode
• Semiconductor light sensors for photodetection
• Generates current/voltage when P-N junction is illuminated
• Used in radiography to convert visible light from scintillators
into electrical signals
• There are various types of photodiode
- PIN photodiode
- P-N photodiode
- Avalanche photodiode
Fig:- PIN Photodiode
37. Charged Coupled Device
• Uses photosensitive silicon chips
• Converts light into digital signals
• Integrated circuit made of amorphous silicon
• Illuminated silicon layer generates electrical charge
• Charge accumulates in pixel cells
• Readout occurs in pixel by pixel manner A tiled CCD designed for digital radiographic
imaging
38. Working of CCD
• CCD consists of array of light- sensitive pixels.
• Pixels are organized in rows and columns
• Each pixel converts photons to electrical charge via the photoelectric effect.
• The number of electrons released depends on the intensity of light. These
electrons are build up in the pixel.
• The electrons are kept in the pixel by electronic barriers on each side of the pixel
• Once the CCD chip has been exposed, the electronic charge that resides in each
pixel is read out.
39. • Charge is readout in “bucket brigade” fashion ,i.e.; The
electronic charge is shifted pixel by pixel by
appropriate control of voltage level at the boundaries
of each pixel.
• Thus ,the charge pocket in one column moves in
unison & finally reaches the pixel in the bottom row.
• The bottom row is read out pixel by pixel & the charge
is shifted to the read out electronics, which produces
an electronic signal.
• This signal is digitized by a ADC and the digital signal is
used to construct image matrix.
• This process is repeated until all the pixels in the
detector are read out completely.
CONTD..
Fig:- Movement of charge pockets
column by column through bottom row
40. Advantages of CCD
• The main advantage of the CCD is the extremely fast
discharge time which is useful in cardiac catheterization
where high-speed imaging is critical to visualizing blood flow.
• Sensitivity-ability to detect & respond to very low levels
of visible light. Hence reduces the patient dose.
• Dynamic range- ability to respond wide range of light
intensity. Radiation response of CCD is linear.
• Size- its size is very small that makes it highly adaptable
to DR in its various forms. It measures 1 to 2 cm.
Fig:- Radiation response of CCD
Compared with that of a 400- speed
Screen-film IR
41. Disadvantages of CCD
• The principal disadvantage of CCDs is that they are physically small and
consequently can image only a small region.
• When large FOV is needed to image, it is impossible to image the light into the
surface of CCD chip without losing the light photons.
• The assembly of multiple CCD(mosaic CCD) is used to overcome this problem.
42. CMOS
• Recent Advancement is focusing on Complimentary-Metal-Oxide
Semiconductors(CMOS) technology and are being used instead of CCD
• These are newer design of Transistors.
• CMOS is a type of MOSFET(Metal-Oxide-Semiconductor Field- Effect Transistor)
and utilizes it as individual pixel elements.
• CMOS sensors consists of array of pixels that converts X-rays into electrical
signals.
43. Advantages of CMOS over CCD
• Cheaper compared to that of CCD (i.e. the CMOS chip incorporates amplifiers and
A/D-converters, which lowers the cost since it contains all the logics needed to
produce an image)
• Consumes little power (CCD uses 100 times more power than CMOS)
• CMOS Detectors are more flexible, more stable, more sensitive, and faster than
TFT-based flat panel detectors while producing higher resolution images.
• Faster readout speed
• Clinical benefits in medical applications include lower radiation dose to the
patient without compromising image quality.
44. Disadvantages of CMOS
• Lower light sensitivity compared to that of CCD
• More susceptible to noise
45. FLAT PANEL DETECTORS
• Comprises numerous detector elements storing charge in response
to x-ray exposure.
• Charge buildup in each element held by capacitors during exposure.
• Post-exposure, electronics read out the charge in each detector
element.
• Each detector element has a transistor, utilizing thin-film deposition
tech.
• Referred to as thin- film transistor (TFT) image receptors due to
transistor use.
• It may be of Direct or Indirect in nature which categorize the DR into
Direct DR and Indirect DR.
Fig:- A flat panel detector array
comprises of large no. of detector
element. Each contains both a light
sensitive area and a region that
holds electronic components
47. CESIUM IODIDE/ AMORPHOUS SILICON
• Earlier, CsI was used to capture x-ray as well as
transmission of resulting scintillation light to collection
element.
• Previously silicon as semiconductor was grown as
crystal.
• Later, amorphous silicon was identified and can be
painted on supporting surface.
• So, collection element is silicon sandwiched as a TFT.
• Is an indirect DR process.
Fig:- CsI phosphor in digital radiography
IR is available in form of filaments to
Improve x-ray absorption and reduce light
dispersion
48. CESIUM IODIDE/ AMORPHOUS SILICON
• IR is fabricated into individual pixels.
• Each pixel has a light sensitive face of a-Si with a
capacitor and a TFT embedded.
• Geometry of pixel is imp. As portion of pixel face is
occupied by conductors, capacitors and TFT, it is not
totally sensitive to incident image forming x-rays.
49. FILL FACTOR
• Percentage of the pixel that is sensitive to x-rays is Fill
factor.
• Spatial resolution in DR is pixel limited.
• As pixel size is reduced, spatial resolution improves but at
the expense of pt. radiation dose.
• With smaller pixel size, fill factor is reduced and x-ray
intensity must be increased to maintain adequate signal
strength.
• Nowadays, nanotechnology promises increased fill factor
and improved spatial resolution at even lower pt. dose.
50. GdOS/ a-Si
• Widely used as capture element of most rare earth Intensifying Screens.
• Same as CsI/a-Si image receptor.
• Thickness of GdOS determines speed of IR.
• Increasing the thickness of GdOS in DR IR increases the speed of the
system with no compromise in spatial resolution.
51. AMORPHOUS SELENIUM
• No scintillation phosphor is required.
• A-Se is both capture element and coupling element.
• Image forming x-rays beam interacts directly with a-Se,
producing charge pair.
• Approx. 200 micrometer thick and sandwiched between
charged electrodes.
• A-Se create electron hole pairs through direct ionization of
selenium.
• Created charge is collected by storage capacitor and remains
there until the signal is read by switching action of TFT.
Fig: Use of a- selenium as an IR
capture element eliminated the need
for a scintillation phosphor
52. INDIRECT CONVERSION
Indirect conversion with CCD
• X-ray energy is converted into light by a scintillator such
as Tl doped cesium iodide. The amount of light emitted
is then recorded by the CCD, and the light is converted
into electrical charges.
• It is an array consisting of several CCD chips which
forms a detector area similar to that of a flat-panel
detector.
• CCDs can be used for radiography as part of either a
lens-coupled CCD system or a slot-scan CCD system.
• CCD-based systems were comparable to flat-panel
detectors in terms of image quality and allowed slightly
superior low-contrast visualization.
CCD can be tiled to receive the light from an
area x-ray beam as it interacts with a scintillation
phosphor such as CsI
53. INDIRECT CONVERSION
Indirect Conversion with a Flat-Panel Detector
• Indirect conversion DR systems are “sandwich” constructions
consisting of a scintillator layer , an amorphous silicon photodiode
circuitry layer, and a TFT array.
• X-ray photons reach the scintillator, visible light proportional to
the incident energy is emitted.
• It is recorded by an array of photodiodes and converted to
electrical charges.
• These charges are then read out by a TFT array.
• Scintillators usually consist of CsI or GdOS .The advantage of CsI-
based scintillators is that the crystals can be shaped in thin
needles, which can be arranged perpendicular to the surface of
the detector.
54. DIRECT CONVERSION
• Direct conversion requires a photoconductor that converts x-
ray photons into electrical charges by setting electrons free .
• Typical photoconductor materials include amorphous
selenium, lead iodide, lead oxide, thallium bromide, and
gadolinium compounds. The most commonly used element
is selenium.
• Selenium-based direct conversion DR systems are equipped
with either a selenium drum or a flat-panel detector.
• A-Se is both capture & coupling element.
• Selenium is a photoconductor that when exposed to
radiation alters its electrical conductivity proportional to the
intensity of radiation Fig:- Use of a-selenium as an IR capture
element eliminated the need for a
scintillation phosphor
59. Advantages of DR
• Digital image capture
• Environmental friendly: Elimination of costly film processing steps
• Superior gray-scale resolution: uses 256 colors of gray compared to 16-30
shades on film.
• Lower radiation dose:50-80% less radiation with no loss of image quality
• Can be stored electronically; easier to retrieve patient’s records
• Image enhancement/manipulation for better interpretation:
Contrast, colorization, magnification, sharpness, and image orientation
• Computer- Aided Diagnosis (CAD)
• Potential for teleradiology
60. Disadvantages of DR
• High cost depending on manufacturer and features
• Technology changes: System may become obsolete and no longer has support
• Artifacts: occurs during digital image acquisition and /or retrieval process.
• The spatial resolution of DR image recording systems is lower than that of F/S
image recording systems however ;The impact of such a lower spatial resolution
system on clinical performance is not significant.
• Dose-creep: since , exposure latitude is wide , high exposure technique may be
used which increases the patient dose which is called dose-creep. This can be
reduced by exposure indicator or exposure index which gives the user feedback
about the actual dose.
61. Advancements in CR
1. Automated CR systems:
• It reduces the readout time and by removing the step of cassette handling.
• The readout time of PSP plate is reduced to less than 10 sec by line scan lasers
and photodiode detectors in automated CR systems
2.Newer structured phosphor for PSP plates:
• Newer phosphors like cesium bromide having a structured needle-shaped
configuration of crystals have been recently introduced which reduce light
diffusion.
• They are also more efficient with an increased DQE
62. 3.Mobile CR systems:
• To save labor, time and improve workflow of critically ill
patients requiring bedside X-rays, portable, compact CR
systems have been introduced in 2007.
• Mobile x-ray unit with integrated CR reader eliminates
cassette transport.
• Image available in less than 25 seconds.
63. Advancements in DR
1. Tomosynthesis:
• In this technique multiple low dose exposures are given from various angles
while the X-ray tube moves in an arc and the detector remains stationary.
• The images can be viewed singly or in a wire loop
2. Dual energy imaging:
• Dual energy radiography methods are used to generate separate images of bone
and soft tissue structures from two exposures made using different radiographic
techniques
64. 3. Computer aided diagnosis (CAD):
• They are important in early detection of cancer of the
lung and breast. The suspicious areas are marked by
the software for review by the radiologist. The main
advantage of CAD is that it alerts the radiologist to
avoid overlooking diagnostically significant findings
4. Automatic image stitching:
• This feature is useful when precise measurements in
lengthy anatomical regions like the spine or lower limb
are required.
5. Mobile DR:
• It consists of a 14 × 17 inch flat panel detector
connected by a cable to a mobile X-ray system having a
monitor.
FIG:- Mobile DR
65. 6.Wireless FPDs:
• A wireless portable DR system can transfer image data wirelessly to the DR
system. It does not have any cables and does not interfere with surrounding
machines
7. Fluoroscopy and radiography:
• Real time digital imaging facilitates high quality radiography and fluoroscopy with
up to 30 images/sec
66. TUTH Department Detectors
1. Musica Technology
DR 14e
Agfa
@Room no . C2
2. iRay Technology DR panel
MARS 1417V
@Room no. C3
3. Konika Minolta
AeroDR NS 1417(P-41)
@Room no. C4
67. Musica Technology Agfa DR panel specifications
Rated Voltage 100 – 240 V
Detector Type Amorphous Silicon with TFT
Pixel Pitch 150 μm
Active Pixel Matrix 2336 x 2836 pixels
Conversion screen Csl (Cesium Iodide) and GOS (Gadolinium oxysulphide)
Active Area Size 430 mm x 350 mm
Effective Pixel Matrix 2336 x 2836 pxl
Grayscale 16 Bit
Spatial Resolution Min. 3.36 lp/mm
Energy Range Standard 40 – 150 kVp
68. iRay Technology DR panel specifications
Brand iRay Technology
Model MARS 1417V
Detector Technology Amorphous Silicon
Scintillator Csl
Active Area (inch) 14x17
Pixel Matrix 2304x2800
Pixel Pitch (μm) 150
Limiting Resolution (lp/mm) 3.4
AD Conversion (bit) 16
Battery Autonomy (h) 8
WIFI 2.4G and 5G
IEEE802. 11 a/b/g/n/ac
Trigger Mode ADE (optional) / Software
69. Konica Minolta DR panel specification
Product name (model name) AeroDR NS 1417(P-41)
Detection Method Indirect conversion Method
Scintillator Csl ( Cesium Iodide)
External Dimension 384x460x15xmm (15.1x18.1x0.6 inch)
Weight (including Battery) 3.6 kg (7.9lb)
Pixel Size 150 μm
Image area size 345.6x420.0mm (13.6x16.5 inch)
AD conversion 16 bit (65,536 gradients)
Usable grid frequency 40lp/cm
Durability Print load : 100kg@Φ 40mm
Face load : 150kg @effective image area
overall
Image storage 200 image
Battery Lithium Ion
70. Canon CXDI-701G Wireless DR panel
specification
Method Scintillator & Amorphous Silicon (a-Si)
Sensor LANMIT (Large Area New-MIS sensor and TFT)
Scintillator Terbium-doped Gadolinium oxysulphide
(Gd2O2S:Tb)
Grid Recommended: 52 lp/cm
Pixel Pitch 125 x 125 μm
Total Pixel Count 2,800 x 3,408 pixels (Approx. 9.5 Million)
Exposure Range Automatic Range Detection (Max. 35 x 42.6 cm)
Grayscale 65,536 Steps (16-bit)
Voltage AC 100V (50/60 Hz)
On board image storage 99 Images
Load Tolerance 100 kg @ φ 40 mm, 150 kg @ Entire Area
Power Consumption 90 VA Max. (Wireless) / 41 VA Max. (Wired)
71. Summary
• Digital radiography is film-less imaging system; digital sensors are used instead of
traditional photographic films.
• The earliest DR was a spin-off from CT & involved a collimated fan x-ray beam.
• Currently, four methods are used to produce a digital projection radiograph.
• CR is based on the principle of Photo- stimulable Luminescence; PSP plates instead
of film/screen image receptors and the image is acquired in digital Form.
• CsI scintillation phosphor can be used as capture element for image forming x-rays
whose signal is channeled to a CCD through fiber optic channels.
• CsI scintillator allows greater detection of x-rays, as there is no light spread, & much
greater resolution.
• Amorphous selenium is used as a capture element for x-rays in an alternate DR
method.
72. Reference
• Radiologic Science For Technologists -Stewart Carlyle Bushong
• The Essential Physics for Medical Imaging -Bushberg
• Various Slides and official websites.
photoelectric effect, in which incoming photon strikes the photocathode, and releases an electron from the surface
Secondary emission from dynode D1 when struck by the primary electron. As the electron cascade progresses from dynode to dynode, the number of electrons increases exponentially through a process called electron multiplication. The multiplied electrons reach the anode, where they are collected & converted into an electrical signal proportional to the intensity of the incident light.
is sandwiched between two electrodes to which high voltage is applied. When this layer is exposed to X-rays, electrons and holes are produced, proportional to the amount of X-rays absorbed. The applied voltage separates the electrons and holes, so that the signal does not spread. The electronic charge is stored in capacitors and is read out sequentially. Thus, the X-rays are directly converted to electrical signal