DIGITAL PROJECTION DIGITAL PROJECTION RADIOGRAPHYRADIOGRAPHY
COMPUTED RADIOGRAPHYCOMPUTED RADIOGRAPHY
DIGITAL PROJECTION DIGITAL PROJECTION RADIOGRAPHYRADIOGRAPHY DEPENDS ON DEPENDS ON COMPUTER TECHNOLOGY TO COMPUTER TECHNOLOGY TO
PRODUCE DIGITAL PRODUCE DIGITAL RADIOGRAPHIC IMAGERADIOGRAPHIC IMAGE
DIGITAL PROJECTION RADIOGRAPHY
COMPUTED RADIOGRAPHY (CR) DIGITAL RADIOGRAPHY (DR)
DIGITAL RADIOGRAPHY DIGITAL RADIOGRAPHY
vsvs
COMPUTED RADIOGRAPHYCOMPUTED RADIOGRAPHY
DETECTORS
11011101
DR
ADC
X-RAYS
CR PLATE
11011101
CR
ADC
X-RAYS
SCANNER
COMPUTED RADIOGRAPHY COMPUTED RADIOGRAPHY (CR):(CR):
USES PHOTOSTIMULABLE PLATE (IMAGE USES PHOTOSTIMULABLE PLATE (IMAGE PLATE) PLATE)
INSTEAD OF FILM, AS THE IMAGE INSTEAD OF FILM, AS THE IMAGE RECEPTOR.RECEPTOR.
CRCR USES CASSETTE THAT LOOKS VERY USES CASSETTE THAT LOOKS VERY SIMILAR TO CONVENTIONAL SIMILAR TO CONVENTIONAL RADIOGRAPHIC CASSETTE. RADIOGRAPHIC CASSETTE.
CR PLATE !!!!!CR PLATE !!!!!
DOES NOT USE SCREENS OR DOES NOT USE SCREENS OR FILM ( CONVENTIONAL FILM)FILM ( CONVENTIONAL FILM)
CR PLATECR PLATE
CASETTE CONSTRUCTIONCASETTE CONSTRUCTION
►LIGHTWEIGHT ALUMINUMLIGHTWEIGHT ALUMINUM►PLASTICPLASTIC►STEEL FRAMESTEEL FRAME
FRONT PANEL MADE OF LOW ATTENUATION CARBON FIBER
CR CASSETTES ARE NOT CR CASSETTES ARE NOT LIGHT-TIGHTLIGHT-TIGHT
IMAGE PLATE IS NOT IMAGE PLATE IS NOT SENSITIVE TO LIGHTSENSITIVE TO LIGHT
CR CASSETTE IS CR CASSETTE IS PROTECTING IMAGE PLATE PROTECTING IMAGE PLATE
FROM DAMAGEFROM DAMAGE++
IS THE STABLE VEHICLE FOR IS THE STABLE VEHICLE FOR TRANSPORT AND TRANSPORT AND
PLACEMENT OF THE PLACEMENT OF THE CASSETTE UNDER THE CASSETTE UNDER THE
PATIENTPATIENT
BACK PANEL CONTAINS LEAD BACK PANEL CONTAINS LEAD FOIL TO PROTECT THE PLATE FOIL TO PROTECT THE PLATE
FROM FROM BACKSCATTER BACKSCATTER
BACK PANEL ALSO CONTAINS BACK PANEL ALSO CONTAINS CHIP TO RECORD PATIENT CHIP TO RECORD PATIENT
DEMOGRAPHIC INFORMATIONDEMOGRAPHIC INFORMATION
REMOTE OPERATOR PANELREMOTE OPERATOR PANEL
IMAGE PLATEIMAGE PLATE
APPROX. 1MM
CROSS-SECTION OF CR CROSS-SECTION OF CR PLATEPLATE
PROTECTIVE LAYER
PHOSPHOR LAYER
ANTI-HALO & REFLECTIVE LAYER
BASE
BACKING LAYER
BASEBASE
►PET- POLYETHYLENE TERAPHTALATEPET- POLYETHYLENE TERAPHTALATE
PHOSPHOR LAYERPHOSPHOR LAYER
►Ba FX: Eu Ba FX: Eu +2+2
PROTECTIVE LAYERPROTECTIVE LAYER
►FLUORINATED POLYMER MATERIALFLUORINATED POLYMER MATERIAL
PROTECTS PHOSPHOR LAYER
ANTI-HALO LAYER + REFLECTIVE ANTI-HALO LAYER + REFLECTIVE LAYERLAYER
►PREVENTS LASER FROM PASSING PREVENTS LASER FROM PASSING THROUGH.THROUGH.
►REFLECTED LIGHT FROM PHOSPHOR IS REFLECTED LIGHT FROM PHOSPHOR IS ALLOWED TO PASS.ALLOWED TO PASS.
BACKING LAYERBACKING LAYER
►PROTECTS THE BASE FROM DAMAGE.PROTECTS THE BASE FROM DAMAGE.
LEAD COATINGLEAD COATING
SCATTER
The simplest explanation for The simplest explanation for luminescence is that impurities in the luminescence is that impurities in the
crystal lattice are responsible for crystal lattice are responsible for luminescence. As the concentration of luminescence. As the concentration of impurity ions increase the greater the impurity ions increase the greater the
intensity of the luminescence. CR intensity of the luminescence. CR screens use barium fluorohalides doped screens use barium fluorohalides doped with europium (europium is the impurity with europium (europium is the impurity
in the crystal).in the crystal).
When phosphors are stimulated with x-When phosphors are stimulated with x-ray photon energy electron pair holes ray photon energy electron pair holes
are created. In effect, europium is raised are created. In effect, europium is raised to an excited state and upon to an excited state and upon
luminescence it is returned to its ground luminescence it is returned to its ground Eu2+ state. This mechanism holds for Eu2+ state. This mechanism holds for both spontaneous luminescence and both spontaneous luminescence and
photostimulated luminescencephotostimulated luminescence
The shifting of europium from its excited The shifting of europium from its excited state back to its ground state for both state back to its ground state for both
spontaneous and photostimulated spontaneous and photostimulated luminescence is about 0.6 - 0.8 luminescence is about 0.6 - 0.8
microseconds. With screen-film imaging microseconds. With screen-film imaging these crystals spontaneously these crystals spontaneously
luminescence to expose a film, but with luminescence to expose a film, but with CR imaging the luminescence occurs, CR imaging the luminescence occurs, then there is also photoluminescence then there is also photoluminescence
that occurs when the screen is that occurs when the screen is stimulated by a narrow beam of infrared stimulated by a narrow beam of infrared
light.light.
The holes or vacancies in the lattice are The holes or vacancies in the lattice are portions of the lattice normally occupied portions of the lattice normally occupied
by halogens (fluoride, bromide, or by halogens (fluoride, bromide, or iodine). These vacancies will trap free iodine). These vacancies will trap free
electrons when irradiated and are called electrons when irradiated and are called FarbzentrenFarbzentren centers or centers or F-centersF-centers..
When the photostimulable plate is When the photostimulable plate is exposed to high frequency light, usually exposed to high frequency light, usually
from a helium laser, the electrons in from a helium laser, the electrons in these F-centers are liberated and cause these F-centers are liberated and cause
luminescence at readout.luminescence at readout.
THE LATENT IMAGE WILL THE LATENT IMAGE WILL REMAIN STORED FOR 24 REMAIN STORED FOR 24
HOURS.HOURS.
IT WILL FADE THROUGH IT WILL FADE THROUGH PHOSPHORESCENCEPHOSPHORESCENCE
FADINGFADING
► 25% OF STORED 25% OF STORED ENERGYENERGY
► WITHIN 8 HOURSWITHIN 8 HOURS
CR AFTER EXPOSURE IS CR AFTER EXPOSURE IS INSERTED INTO INSERTED INTO CR SCANNERCR SCANNER
CR PLATE
CR SCANNER/READER
THE SCANNER SCANS THE THE SCANNER SCANS THE IMAGE PLATE WITH LASER IMAGE PLATE WITH LASER
LIGHT AND READS THE LIGHT AND READS THE LATENT IMAGE FROM THE LATENT IMAGE FROM THE
PHOSPHORPHOSPHOR
READOUTREADOUT
LASER LIGHTLASER LIGHT
HELIUM-NEON (633 nm) HELIUM-NEON (633 nm) LASER BEAM SWEEPS THE LASER BEAM SWEEPS THE PLATE IN RASTER FASHIONPLATE IN RASTER FASHION
RASTER RASTER
PM TUBE
AMPLIFIER ADC
LASER
LIGHTGATE
SWEEPING OF THE LASER SWEEPING OF THE LASER ACROSS THE PLATEACROSS THE PLATE
►FAST SCAN DIRECTIONFAST SCAN DIRECTION►SCAN DIRECTIONSCAN DIRECTION►LASER SCAN DIRECTIONLASER SCAN DIRECTION
PLATE MOVEMENT IN THE PLATE MOVEMENT IN THE SCANNERSCANNER
►SLOW SCAN DIRECTIONSLOW SCAN DIRECTION►SUB-SCAN DIRECTIONSUB-SCAN DIRECTION►PLATE SCAN DIRECTIONPLATE SCAN DIRECTION
THE SPEED OF THE THE SPEED OF THE SCANNING LASER BEAM IS SCANNING LASER BEAM IS
ADJUSTED TO THE ADJUSTED TO THE LUMINESCENT SIGNALLUMINESCENT SIGNAL
PLATE & F-CENTERS
LASER 633 nm
PHOTOSTIMULABLE LUMINESCENCE
390-400 nm
LASER LASER SPOT SIZE - LASER LASER SPOT SIZE - 100 MICROMETERS100 MICROMETERS
PIXEL SIZE - 100 PIXEL SIZE - 100 MICROMETERSMICROMETERS
P.M. TUBE DETECTION P.M. TUBE DETECTION SENSITIVITY MATCHED TO SENSITIVITY MATCHED TO
BLUE-PURPLE BLUE-PURPLE PSLPSL (390-400 (390-400 nm)nm)
AFTER SCANNING THE CR AFTER SCANNING THE CR PLATE NEED TO BE CLEARED PLATE NEED TO BE CLEARED
FROM RESIDUAL SIGNALFROM RESIDUAL SIGNAL
PLATE EXPOSED TO HIGH PLATE EXPOSED TO HIGH INTENSITY SODIUM VAPOR INTENSITY SODIUM VAPOR
OR OR FLUORESCENT LIGHT FLUORESCENT LIGHT
Typical image plate can be Typical image plate can be reused reused thousands of timesthousands of times
IMAGE DISPLAYIMAGE DISPLAY
IMAGE CHECK-INDEX???IMAGE CHECK-INDEX???
IMAGE MANIPULATION-IMAGE MANIPULATION-WINDOWINGWINDOWING
PICTURE DESTINATION -PACSPICTURE DESTINATION -PACS
PACSPACS
CR CHARACTERISTIC CURVECR CHARACTERISTIC CURVE
►VERY WIDE LATITUDEVERY WIDE LATITUDE
CR SYSTEMSCR SYSTEMS
►LESS RADIOGRAPH REPEATSLESS RADIOGRAPH REPEATS
CHARACTERISTIC CURVECHARACTERISTIC CURVE
LATITTUDE OF CR
LATITTUDE OF FILM
IMAGE CAN BE SALVAGED WITH IMAGE CAN BE SALVAGED WITH CRCR
►500% OVEREXPOSURE500% OVEREXPOSURE
►80% UNDEREXPOSURE80% UNDEREXPOSURE
USE ADEQUATE KVP
HARD COPY GENERATED IN HARD COPY GENERATED IN LASER PRINTERLASER PRINTER
CR SYSTEM EFFICIENCY CR SYSTEM EFFICIENCY CHARACTERISTICCHARACTERISTIC
►QDE- QUANTUM DETECTION QDE- QUANTUM DETECTION EFFICIENCYEFFICIENCY
NO NEED FOR SCREENS
QDE:QDE:
THE MEASURE OF THE EFFICIENCY OF THE MEASURE OF THE EFFICIENCY OF CR SYSTEM TO CONVERT REMNANT X-CR SYSTEM TO CONVERT REMNANT X-
RAYS TO USEFUL IMAGE SIGNALRAYS TO USEFUL IMAGE SIGNAL
QDEQDE
PATIENT DOSE PATIENT DOSE
DIGITAL RADIOGRAPHYDIGITAL RADIOGRAPHY
ELECTRONIC DETECTORSELECTRONIC DETECTORS
► INDIRECT TECHNIQUE CLASSINDIRECT TECHNIQUE CLASS►DIRECT TECHNIQUE CLASSDIRECT TECHNIQUE CLASS
INDIRECT TECHNIQUEINDIRECT TECHNIQUE
► INDIRECT CONVERSION FLAT PANEL INDIRECT CONVERSION FLAT PANEL DETECTORSDETECTORS
► INDIRECT CONVERSION CHARGED INDIRECT CONVERSION CHARGED COUPLE DEVICE DETECTORSCOUPLE DEVICE DETECTORS
INDIRECT CONVERSION FLAT INDIRECT CONVERSION FLAT PANEL DETECTORSPANEL DETECTORS
►USE THIN LAYERS OF SILICON USE THIN LAYERS OF SILICON COMBINED WITH THE ARRAYS OF COMBINED WITH THE ARRAYS OF PHOTODIODES. P.D. IS COATED PHOTODIODES. P.D. IS COATED WITH CESIUM IODIDE OR RARE WITH CESIUM IODIDE OR RARE EARTH MATERIAL- WHEN STRUCK BY EARTH MATERIAL- WHEN STRUCK BY REMNANT X-RAYS THEY EMIT LIGHT. REMNANT X-RAYS THEY EMIT LIGHT.
ADVANTAGE: HIGH QDEDISADVANTAGE: LIGHT DIVERGENCE
PHOTODIODEPHOTODIODE
INDIRECT CONVERSION INDIRECT CONVERSION CHARGE COUPLED DEVICE CHARGE COUPLED DEVICE
DETECTORSDETECTORS►USE CCD ARRAYS TO RECORD THE USE CCD ARRAYS TO RECORD THE
VISIBLE LIGHT EMITTED BY A VISIBLE LIGHT EMITTED BY A SCINTILLATION CRYSTAL THAT HAS SCINTILLATION CRYSTAL THAT HAS ABSORBED THE ENERGY. AN OPTICAL ABSORBED THE ENERGY. AN OPTICAL COUPLING SYSTEM DEMAGNIFIES THIS COUPLING SYSTEM DEMAGNIFIES THIS LIGHT AND SENDS IT TO THE CCD LIGHT AND SENDS IT TO THE CCD ARRAY.ARRAY.
OPTICAL COUPLINGOPTICAL COUPLING
CCDCCD
DIRECT TECHNIQUEDIRECT TECHNIQUE
►DIRECT CONVERSION FLAT PANEL DIRECT CONVERSION FLAT PANEL DETECTORSDETECTORS
DIRECT CONVERSION FLAT DIRECT CONVERSION FLAT PANEL DETECTORSPANEL DETECTORS
► USE AN AMORPHOUS SELENIUM COATED THIN USE AN AMORPHOUS SELENIUM COATED THIN FILM TRANSISTOR ARRAY THAT DIRECTLY FILM TRANSISTOR ARRAY THAT DIRECTLY CONVERTS X-RAY ENERGY INTO ELECTRICAL CONVERTS X-RAY ENERGY INTO ELECTRICAL SIGNAL. REMNANT X-RAYS ARE ABSORBED IN SIGNAL. REMNANT X-RAYS ARE ABSORBED IN THE SELENIUM WHERE THEY FORM ELECTRON-THE SELENIUM WHERE THEY FORM ELECTRON-
HOLES. CAPACITORS COLLECT THE CHARGE.HOLES. CAPACITORS COLLECT THE CHARGE.
ADVANTAGE: NO LIGHT DIVERGENCE
READY - The 17"x17" amorphous selenium-based sensor is electrically sensitized and readied for exposure.
EXPOSE - Incident X-ray photons are converted into electron-hole pairs. A transverse electric field separates the electrons and holes and creates a charge image precisely corresponding to the X-ray image.
READOUT - The microplasma line scanner sweeps across the sensor in less than 2 seconds causing readout of the charge image and sensor reset.
DR vs CR COMPARISONDR vs CR COMPARISON
► IMMEDIATE REDOUTIMMEDIATE REDOUT► CASSETTE FREE CASSETTE FREE
OPERATIONOPERATION► GOOD FOR HIGH GOOD FOR HIGH
VOLUME VOLUME RADIOGRAPHYRADIOGRAPHY
► CAN BE USED FOR CAN BE USED FOR MAMMOGRAPHYMAMMOGRAPHY
► DETECTORS CAN BE DETECTORS CAN BE RE-EXPOSED RE-EXPOSED IMMEDIATELYIMMEDIATELY
► MORE EXPENSIVEMORE EXPENSIVE► CAN NOT BE USED IN CAN NOT BE USED IN
PORTABLE PORTABLE RADIOGRAPHY??????RADIOGRAPHY??????
► NOT COMPATIBLE WITH NOT COMPATIBLE WITH EXISTING TABLESEXISTING TABLES
ADVANTAGE DISADVANTAGE
DR SYSTEM
PORTABLE????PORTABLE????
PORTABLE CT???!!PORTABLE CT???!!
MONITORS IN DRMONITORS IN DR
► 1K1K
► 2K2K
► 4K4K
► 1,000 X 1,000 PIXELS1,000 X 1,000 PIXELS
► 2,000 X 2,000 PIXELS2,000 X 2,000 PIXELS
► 4,000 X 4,000 PIXELS4,000 X 4,000 PIXELS
4K MONITORS USED IN MAMMOGRAPHY AND CHEST RADIOGRAPHY
DR TERMS TO KNOWDR TERMS TO KNOW
► PIXEL PIXEL ► VOXELVOXEL► SPATIAL RESOLUTIONSPATIAL RESOLUTION► DYNAMIC RANGEDYNAMIC RANGE► CONTRAST RESOLUTIONCONTRAST RESOLUTION► IMAGE NOISEIMAGE NOISE
PIXELPIXEL
VOXELVOXEL.
The formation
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