COMPUTED RADIOGRAPHY

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COMPUTED RADIOGRAPHY

• Dawn Guzman Charman, M.Ed., R.T.
• RAD TECH A

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RADIOLOGIC TECHNOLOGY
A HIGH TECH HIGH TOUCH PROFESSION
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filmless radiology departments

• Diagnostic radiographers
• have traded their film and chemistry
• for a computer mouse
• and monitor
• advance for Rad Sci Prof, 8/9/99

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What Is Digital Imaging?

• Digital imaging is the acquisition of images to a
  computer rather than directly to film.

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New Technology

• Has impacted
• practicing radiologic technologist
• educators
• Administrators
• students in the radiologic sciences.

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• Many local area hospitals
• and medical centers
• have this equipment NOW

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Computed Radiography
Fundamentals of Computerized Radiography

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Radiology 1895
Radiology 2001
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CR SYSTEM COMPONENTS

• CASSETTES (phosphor plates)
• ID STATION
• IMAGE PREVIEW (QC) STATION
• DIGITIZER
• VIEWING STATION

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COMPUTED RADIOGRAPHY Medical Imaging is changing
FILMLESS Radiology is the future And the
Future is here! El Camino College First
educational institution in California or
across the country to offer this new
technology on a college campus
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Equipment Costs
Don Visintainer successfully wrote grants, and
received funding from VTEA, P4E, and private
sources
Total 410,916.00
HIDDEN COSTS
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History of CR

• INDUSTRY
• Theory of filmless radiography first introduced
  in 1970
• 1981 Fugi introduced special cassettes with PSP
  plates (replaces film)
• Technology could not support system
• First clinical use in Japan - 1983

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Predictions

• 1980 Bell Labs believed that Unix would be the
  worlds dominant operating system
• 1982 Bill Gates thought 640K of main memory
  would suffice for workplace operating systems (
  This presentation is 80,000 kb)
• 1984 IBM predicted that personal computers
  would not amount to anything

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History of CR

• By 1998 over 5000 CR systems in use nationwide
• 1998 Local area hospitals begin to incorporate
  CR systems in their departments
• (Riverside Co. Hosp builds new hospital in Moreno
  Valley) completely CR system 1st generation
  equipment

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TERMINOLOGY

• F/S - Film/Screen (currently used method)
• CR - Computed Radiography
• DR - Digital Radiography
• DDR - Direct to Digital Radiography

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IMAGE CREATION

• SAME RADIOGRAPHY EQUIPMENT USED
• THE DIFFERENCE IS HOW IT IS CAPTURED
• STORED
• VIEWED
• And POST -PROCESSED

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CONVENTIAL vs DIGITAL IMAGING

• Currently, most x-ray imaging systems produce
  an analog image (radiographs, fluoroscopy).
  
• Using x-ray tube films in cassettes

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CONVENTIAL vs DIGITAL IMAGING

• Digital radiography systems require that the
  electronic signal be converted to a digital
  signal
• Using x-ray tube cassettes with phosphor plate
  OR
• DR systems - transistors

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COMPUTED RADIOGRAPHY DIRECT RADIOGRAPHY FILM
SCREENIMAGE CAPTURE

• FS - Film inside of cassette
• CR - PHOTOSTIMULABLE PHOSPHOR PLATE
• DR(DDR) - TFT (THIN FILM TRANSISTOR)

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Cassette w/ film CR w psp plate
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Directed Digital Radiography(DDR)

• Directed digital radiography, a
• term used to describe total
• electronic imaging capturing.
• Eliminates the need for an image plate
  altogether.

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Amorphous Selenium detector technology for DR
Direct Radiography
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IMAGE CAPTURE

• CR
• PSP photostimulable phosphor plate
• REPLACES FILM IN THE CASSETTE
• DR NO CASSETTE PHOTONS
• CAPTURED DIRECTLY
• ONTO A TRANSISTOR
• SENT DIRECTLY TO A MONITOR

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CR vs FS

• CR
• PSP in cassette
• Digital image
• Scanned read- CR reader
• COMPUTER
• Image stored on computer
• Viewed on a Monitor
• Hard copy (film) can be made with laser printer

• FILM
• Film in cassette
• loaded in a darkroom
• Processed in a processor
• FILM
• Hard copy image stores the image
• Viewboxes view the images

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CASSETTES with Intensifying
Screens

• The CASSETTE holds the film in a light tight
  container
• It consist of front and back intensifying screens

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CR BASICS

• Eliminates the need for film as a recording,
  storage viewing medium.
• PSP Plate receiver
• Archive Manager storage
• Monitor - Viewing

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General Overview CR

• PSP cassette exposed by
• conventional X-ray equipment.
• Latent image generated as a matrix of
  trapped electrons in the plate.

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CR PSP plate

• photostimulable phosphor (PSP) plate
• Captures photons
• Stored in traps on plate (latent image)
• PLATE scanned in CR READER

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CR Phosphor Plates
ABSORPTION
EMISSION
LASER STIMULATION
ELECTRON TRAP
ELECTRON TRAP
X-RAY
LIGHT
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CR PSP plate

• Stimulated by a RED LIGHT
• Energy is RELEASED in a form of BLUE light
• LIGHT captured by PMT
• changed to a digiial signal

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How CR works

• Released light is captured by a PMT (photo
  multiplier tube)
• This light is sent as a digital signal to the
  computer
• The intensity (brightness) of the light
  correlates to the density on the image

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CR PROCESSORS
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Densities of the IMAGE

• The light is proportional to amount of light
  received
• digital values are then equivalent (not exactly
  the same) to a value of optical density (OD) from
  a film, at that location of the image

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ERASING PLATE

• After image is recorded
• Plate is erased with high intensity white light
• and re-used

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CR VS DR

• CR -Indirect capture where the image is first
  captured on plate and stored then converted to
  digital signal
• DDR -Direct capture where the image is acquired
  immediately as a matrix of pixels sent to a
  monitor

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Digital Radiography
Direct Capture
Indirect Capture
Computed Radiography (CR) - PSL
Direct-to-Digital Radiography (DDR)-Selenium
Direct-to-Digital Radiography Silicon Scint.
Laser Scanning Digitizers
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DIRECT RADIOGRAPHY

• uses a transistor receiver (like bucky)
• that captures and converts x-ray energy
• directly into digital signal
• seen immediately on monitor
• then sent to PACS/ printer/ other workstations
  FOR VIEWING

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CR vs DR

• CR
• imaging plate
• processed in a Digital Reader
• Signal sent to computer
• Viewed on a monitor

• DR
• transistor receiver (like bucky)
• directly into digital signal
• seen immediately on monitor

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Image Resolution (how sharply is the image
seen)

• CR
• 4000 x 4000
• image only as good a monitor
• 525 vs 1000 line
• more pixels more memory needed to store

• CR 2 -5 lp/mm
• RAD 3-6 lp/mm
• DR ?
• IMAGE APPEARS SHARPER BECAUSE CONTRAST CAN BE
  ADJUSTED BY THE COMPUTER
• (DIFFERENCES IN DENSITY)

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ADVANTAGE OF CR/DR

• Can optimize image quality
• by manipulating digital data
• to improve visualization of anatomy and pathology
• AFTER EXPOSURE TO PATIENT

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ADVANTAGE OF CR/DR

• CHANGES MADE TO IMAGE
• AFTER THE EXPOSURE
• CAN ELIMINATE THE NEED TO REPEAT THE EXPOSURE

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ADVANTAGE OF CR/DR vs FS

• Rapid storage
• retrieval of images NO LOST FILMS!
• PAC (storage management)
• Teleradiology - long distance transmission of
  image information
• Economic advantage - at least in the long run?

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CR/DR VS FILM/SCREEN

• FILM these can not be modified once processed
• If copied lose quality
• DR/CR print from file no loss of quality

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no fault TECHNIQUES

• F/S RT must choose technical factors
• (mAs kvp) to optimally visualize anatomic
  detail
• CR the selection of processing algorithms and
  anatomical regions controls how the acquired
  latent image is presented for display
• HOW THE IMAGE LOOKS CAN BE ALTERED BY THE
  COMPUTER EVEN WHEN BAD TECHNIQUES ARE SET

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DR

• Initial expense high
• very low dose to pt
• image quality of 100s using a 400s technique
• Therfore ¼ the dose needed to make the image

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Storage /Archiving

• FILM/SCREEN
• films bulky
• deteriorates over time
• requires large storage expense
• environmental concerns

• CR DR
• 8000 images stored on CD-R
• Jukebox CD storage
• no deterioration of images
• easy access

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Transmission of Images

• PACS - Picture Archiving Communications
• System
• DICOM - Digital Images Communication
• in Medicine
• TELERADIOGRAPHY -Remote Transmission of Images

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Benefits of Computer (web)-based Viewing Systems

• Hardcopy studies are no longer misplaced or lost-
  eliminates films
• Multiple physicians may access same patient films
• Patients do not have to wait in Radiology for
  films once study is completed

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Film-less components

• CR or DR
• CD-ROM or similar output
• Email capability
• Digitizing capability or service

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PACS
Archive
Digital Images
Remote Facilities
Internet VPN
Database and Workflow Engine
Workstations
Remote Workstations
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Histogram Analysis

• A histogram is a plot of gray scale value
• vs. the frequency of occurrence
• ( pixels) of the gray value in the image

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• HISTOGRAM a bar graph depicting the density
  distribution (in numerical values) of the imaging
  plate
• ALGORITHM a set of mathematical values used to
  solve a problem or find an average

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Adapted from AAPM TG10
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Statistical plots of the frequency of occurrence
of each pixel's value
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Basics of Digital Images

• digital images are a (matrix) of pixel (picture
  element) values

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• The algorithm attempts to distinguish among the
  parts of the histogram which represent the range
  of densities from bone to soft tissue

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• Histograms set for specific exams (body parts)
• should produce digital images that are consistant
  (regardless of kVp or mAs used
• Correct Algorithm (body part) must be selected
  prior to processing imaging plate

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Methods to Digitize an Image

• 1. Film Digitizer - Teleradiography system (PACS,
  DICOM)
• 2. Video Camera (vidicon or plumbicon)
• 3. Computed Radiography
• 4. Direct Radiography

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FILM DIGITIZER
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Analog vs Digital

• Analog - one value blends into another
• (like a thermometer)
• Digital - distinct separation
• 98.6
• exact

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ANALOG TO DIGITAL IMAGE

• Conversion of conventional analog films
• to digital format for PACs and teleradiology
  applications
• with scanning laser digitizers

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CONTRAST DENSITY

• Most digital systems are capable of 1024 shades
  of gray - but the human eye can see only about 30
  shades of gray
• The Optical Density and Contrast can be adjusted
  after the exposure by the Radiographer.
• This is POST - PROCESSING

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High displayed contrast narrow window width
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Low displayed contrast (stretched) wide window
width
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Basics of Digital Images

• Pixel values can be any bit depth (values from 0
  to 1023)
• Image contrast can be manipulated to stretched
  or contracted to alter the displayed contrast.
• Typically use window width and window level
  to alter displayed contrast

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80 KVP
5
30
5
15
100
200
500
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• Then the COMPUTER corrects any exposure errors
• Therefore almost ANY technique can be used on the
  patient
• The computer will fix it

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DOSE IMPLICATIONS

• MORE EXPSOURE TO PATIENT
• TECHNIQUES ESTABLISHED
• HIGHER KVP LESS MAS
• LESS PATIENT DOSE

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80 kvp 200mas
10 mas 80 kvp Note Quantum Mottle
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Dose Implications

• Images nearly always look better at higher
  exposures.
• Huge dynamic range means nearly impossible
  to overexpose.

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POST PROCESSING
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TECHNIQUE CONISDERATIONS

• KVP Dependant
• Now COMPUTER controls CONTRAST
• Higher kVp to stimulate electron traps

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standard image
edge sharpening
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REPROCESSED
HAND ALGO
NO GRID
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QC Reader (replaces Darkroom Processor
Chemicals
Diagnostic Viewer (replaces film, storage
viewboxes)
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FILM SCREEN PROCESSOR
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• DEVELOPER
• FIXER
• WASH
• DRY
• WATER - SOLVENT

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PROCESSOR PROBLEM FIXER RETENTION
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scratch
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Crimping /cresent mark
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REPEAT IMAGES
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EMERGING PROBLEMS

• BETTER NOT NECESSARILY FASTER
• LEARNING CURVE FOR TECHNOLOGIST PHYSICIANS
• STUDENT APPLICATIONS ISSUES
• PITFALLS OF CR

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• POSITIONING PROPER COLLIMATION ARE CRITICAL TO
  GOOD IMAGING OUTCOMES
• Just like Phototiming, it can magnify your
  mistakes

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COLLIMATION CRITICAL

• AS THE COMPUTER READS THE DENSITY VALUE OF EACH
  PIXEL IT IS AVERAGED INTO THE TOTAL
• CLOSE COLLIMATION BETTER CONTRAST
• BAD COLLIMATION MORE GRAYS AND LESS DETAIL

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A B
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• Digital imaging is not the end all, cure all for
  imaging problems.
• It is still technologist dependent.

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To Produce Quality Images

• For Conventional Projection
• or CR Radiography
• The same rules, theories, and laws still apply
  and can not be overlooked FFD/OFD (SID/SOD)
  Inverse Square Law Beam Alignment
  Tube-Part-Film Alignment Collimation
  Grids
• Exposure Factors KVP, MaS
• Patient Positioning

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CONVENTIONAL RADIOGRAPHY VIEWING OF X-RAY FILM
IMAGES
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ECC CR 800
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KODAK AUTORAD
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TORRANCE, CALIFORNIA
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NEW IMAGE

• towel that was used to help in positioning a
  child
• CR is MORE sensitive to
• ARTIFACTS

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CR image NEW IMAGE

• Line caused from dirt collected in a CR Reader

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Double exposureChild
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?
Hands over upper abdomen
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High resolution with digital imaging
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Totalbody scan for trauma