This document provides an introduction to digital radiography and picture archiving and communication systems (PACS). It defines key terms and describes the processes of conventional radiography, computed radiography, and direct and indirect digital radiography. The historical development of digital imaging from early CT and MRI to modern digital radiology systems is summarized. Computed radiography uses storage phosphor plates while direct and indirect digital radiography use flat panel detectors or charge-coupled devices connected to computers.

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Radiological technologist
Ph; 9567829285
1
Introduction to Digital RadiographyIntroduction to Digital Radiography
and PACSand PACS

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ObjectivesObjectives
 Define the termDefine the term digital imagingdigital imaging..
 Explain latent image formation for conventionalExplain latent image formation for conventional
radiography.radiography.
 Describe the latent image formation process forDescribe the latent image formation process for
computed radiography.computed radiography.

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 Compare and contrast the latent image formationCompare and contrast the latent image formation
process for indirect capture digital radiography andprocess for indirect capture digital radiography and
direct capture digital radiography.direct capture digital radiography.
 Explain what a PACS (picture archiving andExplain what a PACS (picture archiving and
communication system) is and how it is used.communication system) is and how it is used.
 Define digital imaging and communications inDefine digital imaging and communications in
medicine.medicine.
ObjectivesObjectives

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Key TermsKey Terms
 Computed radiographyComputed radiography
 DICOM (digital imaging and communications inDICOM (digital imaging and communications in
medicine)medicine)
 Digital imagingDigital imaging
 Digital radiographyDigital radiography
 Direct capture DRDirect capture DR
 Indirect capture DRIndirect capture DR
 PACSPACS
 TeleradiologyTeleradiology

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Conventional RadiographyConventional Radiography
 Method is film-based.Method is film-based.
 Method uses intensifying screens.Method uses intensifying screens.
 Film is placed between two screens.Film is placed between two screens.
 Screens emit light when x-rays strike them.Screens emit light when x-rays strike them.
 Film is processed chemically.Film is processed chemically.
 Processed film is viewed on lightbox.Processed film is viewed on lightbox.

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Digital ImagingDigital Imaging
 Digital imagingDigital imaging is a broad term.is a broad term.
 Term was first used medically in 1970s in computedTerm was first used medically in 1970s in computed
tomography (CT).tomography (CT).
 Digital imaging is defined as any image acquisitionDigital imaging is defined as any image acquisition
process that produces an electronic image that canprocess that produces an electronic image that can
be viewed and manipulated on a computer.be viewed and manipulated on a computer.
 In radiology, images can be sent via computerIn radiology, images can be sent via computer
networks to a variety of locations.networks to a variety of locations.

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Historical DevelopmentHistorical Development
of Digital Imagingof Digital Imaging
 CT coupled imaging devices and the computer.CT coupled imaging devices and the computer.
 Early CT scanners required hours to produce a singleEarly CT scanners required hours to produce a single
slice.slice.
 Reconstruction images took several days to produce.Reconstruction images took several days to produce.
 First CT scanners imaged the head only.First CT scanners imaged the head only.
 First scanner was developed by Siemens.First scanner was developed by Siemens.

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 Magnetic resonance imaging (MRI) became availableMagnetic resonance imaging (MRI) became available
in the early 1980s.in the early 1980s.
 Lauterbur paper in 1973 sparked companies toLauterbur paper in 1973 sparked companies to
research MRI.research MRI.
 Many scientists and researchers were involved.Many scientists and researchers were involved.
 Advancements in fluoroscopy occurred in the 1970sAdvancements in fluoroscopy occurred in the 1970s
as well.as well.
 Analog-to-digital converters allowed real-time imagesAnalog-to-digital converters allowed real-time images
to be viewed on TV monitors.to be viewed on TV monitors.
Historical DevelopmentHistorical Development
of Digital Imagingof Digital Imaging

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 Fluoroscopic images could also be stored on aFluoroscopic images could also be stored on a
computer.computer.
 Ultrasound and nuclear medicine used screenUltrasound and nuclear medicine used screen
capture to grab the image and convert it digitally.capture to grab the image and convert it digitally.
 Eventually, mammography converted to digitalEventually, mammography converted to digital
format.format.
Historical DevelopmentHistorical Development
of Digital Imagingof Digital Imaging

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Digital Radiography DevelopmentDigital Radiography Development
 Concept began with Albert Jutras in Canada in theConcept began with Albert Jutras in Canada in the
1950s.1950s.
 EarlyEarly PACSPACS systems were developed by the militarysystems were developed by the military
to send images between Veterans Administrationto send images between Veterans Administration
hospitals in the 1980s.hospitals in the 1980s.
 Development was encouraged and supported by theDevelopment was encouraged and supported by the
U.S. government.U.S. government.

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Digital Radiography DevelopmentDigital Radiography Development
 Early process involved scanning radiographs into theEarly process involved scanning radiographs into the
computer and sending them from computer tocomputer and sending them from computer to
computer.computer.
 Images were then stored in PACS.Images were then stored in PACS.
 Computed andComputed and digital radiographydigital radiography followed.followed.

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Computed RadiographyComputed Radiography
 Uses storage phosphor platesUses storage phosphor plates
 Uses existing equipmentUses existing equipment
 Requires special cassettesRequires special cassettes
 Requires a special cassetteRequires a special cassette
readerreader
 Uses a computer workstationUses a computer workstation
and viewing station and a printerand viewing station and a printer

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Computed RadiographyComputed Radiography
 Storage phosphor plates are similar to intensifyingStorage phosphor plates are similar to intensifying
screens.screens.
 Imaging plate stores x-ray energy for an extended time.Imaging plate stores x-ray energy for an extended time.
 Process was first introduced in the United States by FujiProcess was first introduced in the United States by Fuji
Medical Systems of Japan in 1983.Medical Systems of Japan in 1983.
 First system used a phosphor storage plate, a reader,First system used a phosphor storage plate, a reader,
and a laser printer.and a laser printer.

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Computed RadiographyComputed Radiography
 Method was slow to be accepted by radiologists.Method was slow to be accepted by radiologists.
 Installation increased in the early 1990s.Installation increased in the early 1990s.
 More and more hospitals are replacing film/screenMore and more hospitals are replacing film/screen
technology with digital systems.technology with digital systems.

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Digital RadiographyDigital Radiography
 Cassetteless systemCassetteless system
 Uses a flat panel detector or charge-coupled deviceUses a flat panel detector or charge-coupled device
(CCD) hard-wired to computer(CCD) hard-wired to computer
 Requires new installation of room or retrofitRequires new installation of room or retrofit

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 Two types of digital radiographyTwo types of digital radiography
 Indirect capture DRIndirect capture DR
• Machine absorbs x-rays and converts them to light.Machine absorbs x-rays and converts them to light.
• CCD or thin-film transistor (TFT) converts light to electricCCD or thin-film transistor (TFT) converts light to electric
signals.signals.
• Computer processes electric signals.Computer processes electric signals.
• Images are viewed on computer monitor.Images are viewed on computer monitor.
Digital RadiographyDigital Radiography

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 Direct capture DRDirect capture DR
• Photoconductor absorbs x-rays.Photoconductor absorbs x-rays.
• TFT collects signal.TFT collects signal.
• Electrical signal is sent to computer for processing.Electrical signal is sent to computer for processing.
• Image is viewed on computer screen.Image is viewed on computer screen.
Digital RadiographyDigital Radiography

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 First clinical application was in 1970s in digitalFirst clinical application was in 1970s in digital
subtraction.subtraction.
 University of Arizona scientists applied the technique.University of Arizona scientists applied the technique.
 Several companies began developing large fieldSeveral companies began developing large field
detectors.detectors.
Digital RadiographyDigital Radiography

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 DR used CCD technology developed by the militaryDR used CCD technology developed by the military
and then used TFT arrays shortly after.and then used TFT arrays shortly after.
 CCD and TFT technology developed and continuesCCD and TFT technology developed and continues
to develop in parallel.to develop in parallel.
 No one technology has proved to be better than theNo one technology has proved to be better than the
other.other.
Digital RadiographyDigital Radiography

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Comparison of Film to CR and DRComparison of Film to CR and DR
 For conventional x-ray film andFor conventional x-ray film and computedcomputed
radiographyradiography (CR), a traditional x-ray room with a(CR), a traditional x-ray room with a
table and wall Bucky is required.table and wall Bucky is required.
 For DR, a detector replaces the Bucky apparatus inFor DR, a detector replaces the Bucky apparatus in
the table and wall stand.the table and wall stand.
 Conventional and CR efficiency ratings are about theConventional and CR efficiency ratings are about the
same.same.
 DR is much more efficient, and image is availableDR is much more efficient, and image is available
immediately.immediately.

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 Latent image formation is different in CR and DR.Latent image formation is different in CR and DR.
 Conventional film/screenConventional film/screen
• Film is placed inside of a cassette that contains an intensifyingFilm is placed inside of a cassette that contains an intensifying
screen.screen.
• X-rays strike the intensifying screen, and light is produced.X-rays strike the intensifying screen, and light is produced.
• The light and x-ray photons interact with the silver halide grainsThe light and x-ray photons interact with the silver halide grains
in the film emulsion.in the film emulsion.
Comparison of Film to CR and DRComparison of Film to CR and DR

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Comparison of Film to CR and DRComparison of Film to CR and DR
• An electron is ejected from the halide.An electron is ejected from the halide.
• Ejected electron is attracted to the sensitivity speck.Ejected electron is attracted to the sensitivity speck.
• Speck now has a negative charge, and silver ions will beSpeck now has a negative charge, and silver ions will be
attracted to equal out the charge.attracted to equal out the charge.
• Process happens many times within the emulsion to formProcess happens many times within the emulsion to form
the latent image.the latent image.
• After chemical processing, the sensitivity specks will beAfter chemical processing, the sensitivity specks will be
processed into black metallic silver and the manifest imageprocessed into black metallic silver and the manifest image
is formed.is formed.

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Comparison of Film to CR and DRComparison of Film to CR and DR
 CRCR
• A storage phosphor plate isA storage phosphor plate is
placed inside of CR cassette.placed inside of CR cassette.
• Most storage phosphor plates areMost storage phosphor plates are
made of a barium fluorohalide.made of a barium fluorohalide.
• When x-rays strike theWhen x-rays strike the
photosensitive phosphor, somephotosensitive phosphor, some
light is given off.light is given off.
• Some of the photon energy isSome of the photon energy is
deposited within the phosphordeposited within the phosphor
particles to create the latentparticles to create the latent
image.image.
• The phosphor plate is then fedThe phosphor plate is then fed
through the CR reader.through the CR reader.

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Comparison of Film to CR and DRComparison of Film to CR and DR
 CR, continuedCR, continued
• Focused laser light is scanned over the plate, causing theFocused laser light is scanned over the plate, causing the
electrons to return to their original state, emitting light in theelectrons to return to their original state, emitting light in the
process.process.
• This light is picked up by a photomultiplier tube andThis light is picked up by a photomultiplier tube and
converted into an electrical signal.converted into an electrical signal.
• The electrical signal is then sent through an analog-to-digitalThe electrical signal is then sent through an analog-to-digital
converter to produce a digital image that can then be sent toconverter to produce a digital image that can then be sent to
the technologist review station.the technologist review station.

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Comparison of Film to CR and DRComparison of Film to CR and DR
 DRDR
• No cassettes are required.No cassettes are required.
• The image acquisition device is built into the table and/orThe image acquisition device is built into the table and/or
wall stand or is enclosed in a portable device.wall stand or is enclosed in a portable device.
• Two distinct image acquisition methods are indirect captureTwo distinct image acquisition methods are indirect capture
and direct capture.and direct capture.

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Comparison of Film to CR and DRComparison of Film to CR and DR
 DR, continuedDR, continued
• Indirect capture is similar to CR in that the x-ray energyIndirect capture is similar to CR in that the x-ray energy
stimulates a scintillator, which gives off light that is detectedstimulates a scintillator, which gives off light that is detected
and turned into an electrical signal.and turned into an electrical signal.
• With direct capture, the x-ray energy is detected by aWith direct capture, the x-ray energy is detected by a
photoconductor that converts it directly to a digital electricalphotoconductor that converts it directly to a digital electrical
signal.signal.

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Image ProcessingImage Processing
 Conventional radiographyConventional radiography
• Image is determined by the film itself and the chemicals.Image is determined by the film itself and the chemicals.
 CR and DRCR and DR
• Image processing takes place in a computer.Image processing takes place in a computer.
• For CR, the computer is located near the readers.For CR, the computer is located near the readers.
• For DR, the computer is located next to x-ray console, or itFor DR, the computer is located next to x-ray console, or it
may be integrated within the console, and the image ismay be integrated within the console, and the image is
processed before moving on to the next exposure.processed before moving on to the next exposure.

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Exposure LatitudeExposure Latitude
or Dynamic Rangeor Dynamic Range
 Conventional radiographyConventional radiography
• Based on the characteristic response of the film, which isBased on the characteristic response of the film, which is
nonlinear.nonlinear.
• Radiographic contrast is primarily controlled by kilovoltageRadiographic contrast is primarily controlled by kilovoltage
peak.peak.
• Optical density on film is primarily controlled by milliampere-Optical density on film is primarily controlled by milliampere-
second setting.second setting.

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Exposure LatitudeExposure Latitude
or Dynamic Rangeor Dynamic Range
 CR and DRCR and DR
• Contain a detector that can respond in a linear manner.Contain a detector that can respond in a linear manner.
• Exposure latitude is wide, allowing the single detector to beExposure latitude is wide, allowing the single detector to be
sensitive to a wide range of exposures.sensitive to a wide range of exposures.
• Kilovoltage peak still influences subject contrast, butKilovoltage peak still influences subject contrast, but
radiographic contrast is primarily controlled by an imageradiographic contrast is primarily controlled by an image
processing look-up table.processing look-up table.
• Milliampere-second setting has more control over image noise,Milliampere-second setting has more control over image noise,
whereas density is controlled by image-processing algorithms.whereas density is controlled by image-processing algorithms.

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Scatter SensitivityScatter Sensitivity
 It is important to minimize scattered radiation with allIt is important to minimize scattered radiation with all
three acquisition systems.three acquisition systems.
 CR and DR can be more sensitive to scatter thanCR and DR can be more sensitive to scatter than
screen/film.screen/film.
 Materials used in the many CR and DR imageMaterials used in the many CR and DR image
acquisition devices are more sensitive to low-energyacquisition devices are more sensitive to low-energy
photons.photons.

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Picture Archival andPicture Archival and
Communication SystemsCommunication Systems
 Networked group of computers,Networked group of computers,
servers, and archives to storeservers, and archives to store
digital imagesdigital images
 Can accept any image that is inCan accept any image that is in
DICOMDICOM formatformat
 Serves as the file room, readingServes as the file room, reading
room, duplicator, and courierroom, duplicator, and courier
 Provides image access to multipleProvides image access to multiple
users at the same time, on-users at the same time, on-
demand images, electronicdemand images, electronic
annotations of images, andannotations of images, and
specialty image processingspecialty image processing

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 Custom designed for each facilityCustom designed for each facility
 Components/features can vary based on the following:Components/features can vary based on the following:
• Volume of patientsVolume of patients
• Number of interpretation areasNumber of interpretation areas
• Viewing locationsViewing locations
• FundingFunding
Picture Archival andPicture Archival and
Communication SystemsCommunication Systems

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 Early systems did not have standardized imageEarly systems did not have standardized image
formats.formats.
 Matching up systems was difficult.Matching up systems was difficult.
 Vendors kept systems proprietary and did not shareVendors kept systems proprietary and did not share
information.information.
 DICOM standards helped change this by allowingDICOM standards helped change this by allowing
communication between vendors’ products.communication between vendors’ products.
Picture Archival andPicture Archival and
Communication SystemsCommunication Systems

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 First full-scale PACSFirst full-scale PACS
• Veterans Administration Medical Center in Baltimore usedVeterans Administration Medical Center in Baltimore used
PACS in 1993.PACS in 1993.
• PACS covered all modalities except mammography.PACS covered all modalities except mammography.
• Shortly after, PACS was interfaced with radiologyShortly after, PACS was interfaced with radiology
information systems, hospital information systems, andinformation systems, hospital information systems, and
electronic medical records.electronic medical records.
Picture Archival andPicture Archival and
Communication SystemsCommunication Systems

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PACS UsesPACS Uses
 Made up of different componentsMade up of different components
• Reading stationsReading stations
• Physician review stationsPhysician review stations
• Web accessWeb access
• Technologist quality control stationsTechnologist quality control stations
• Administrative stationsAdministrative stations
• Archive systemsArchive systems
• Multiple interfaces to other hospital and radiology systemsMultiple interfaces to other hospital and radiology systems

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 Early PACS seen only in radiology and some cardiologyEarly PACS seen only in radiology and some cardiology
departments.departments.
 PACS now can be used in multiple departments.PACS now can be used in multiple departments.
 Archive space can be shared among departments.Archive space can be shared among departments.
 PACS reading stations may also have image processingPACS reading stations may also have image processing
capabilities.capabilities.
 PACS allows radiologists to reconstruct and stitchPACS allows radiologists to reconstruct and stitch
images in their offices.images in their offices.
PACS UsesPACS Uses

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 Orthopedic workstations are available for theOrthopedic workstations are available for the
following:following:
• Surgeons can plan joint replacement surgery.Surgeons can plan joint replacement surgery.
• Specialized software allows matching of best replacementSpecialized software allows matching of best replacement
for patient with patient anatomy.for patient with patient anatomy.
• System saves time and provides better fit.System saves time and provides better fit.
PACS UsesPACS Uses

38. THANK YOU………….THANK YOU………….
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