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DIGITAL PROJECTION RADIOGRAPHY COMPUTED RADIOGRAPHY. DIGITAL PROJECTION RADIOGRAPHY DEPENDS ON COMPUTER TECHNOLOGY TO PRODUCE DIGITAL RADIOGRAPHIC IMAGE. DIGITAL PROJECTION RADIOGRAPHY. COMPUTED RADIOGRAPHY (CR). DIGITAL RADIOGRAPHY (DR). DIGITAL RADIOGRAPHY vs COMPUTED RADIOGRAPHY. DR.
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DIGITAL PROJECTION RADIOGRAPHY DEPENDS ON COMPUTER TECHNOLOGY TO PRODUCE DIGITAL RADIOGRAPHIC IMAGE
DIGITAL PROJECTION RADIOGRAPHY COMPUTED RADIOGRAPHY (CR) DIGITAL RADIOGRAPHY (DR)
DR X-RAYS DETECTORS ADC 11011101
CR X-RAYS CR PLATE SCANNER ADC 11011101
COMPUTED RADIOGRAPHY (CR):USES PHOTOSTIMULABLE PLATE (IMAGE PLATE) INSTEAD OF FILM, AS THE IMAGE RECEPTOR.CR USES CASSETTE THAT LOOKS VERY SIMILAR TO CONVENTIONAL RADIOGRAPHIC CASSETTE.
CR PLATE !!!!!DOES NOT USE SCREENS OR FILM ( CONVENTIONAL FILM)
CASETTE CONSTRUCTION • LIGHTWEIGHT ALUMINUM • PLASTIC • STEEL FRAME FRONT PANEL MADE OF LOW ATTENUATION CARBON FIBER
CR CASSETTES ARE NOT LIGHT-TIGHTIMAGE PLATE IS NOT SENSITIVE TO LIGHT
CR CASSETTE IS PROTECTING IMAGE PLATE FROM DAMAGE+IS THE STABLE VEHICLE FOR TRANSPORT AND PLACEMENT OF THE CASSETTE UNDER THE PATIENT
BACK PANEL CONTAINS LEAD FOIL TO PROTECT THE PLATE FROM BACKSCATTER
BACK PANEL ALSO CONTAINS CHIP TO RECORD PATIENT DEMOGRAPHIC INFORMATION
IMAGE PLATE APPROX. 1MM
CROSS-SECTION OF CR PLATE PROTECTIVE LAYER PHOSPHOR LAYER ANTI-HALO & REFLECTIVE LAYER BASE BACKING LAYER
BASE • PET- POLYETHYLENE TERAPHTALATE
PHOSPHOR LAYER • Ba FX: Eu +2
PROTECTIVE LAYER • FLUORINATED POLYMER MATERIAL PROTECTS PHOSPHOR LAYER
ANTI-HALO LAYER + REFLECTIVE LAYER • PREVENTS LASER FROM PASSING THROUGH. • REFLECTED LIGHT FROM PHOSPHOR IS ALLOWED TO PASS.
BACKING LAYER • PROTECTS THE BASE FROM DAMAGE.
LEAD COATING SCATTER
The simplest explanation for luminescence is that impurities in the crystal lattice are responsible for luminescence. As the concentration of impurity ions increase the greater the intensity of the luminescence. CR screens use barium fluorohalides doped with europium (europium is the impurity in the crystal).
When phosphors are stimulated with x-ray photon energy electron pair holes are created. In effect, europium is raised to an excited state and upon luminescence it is returned to its ground Eu2+ state. This mechanism holds for both spontaneous luminescence and photostimulated luminescence
The shifting of europium from its excited state back to its ground state for both spontaneous and photostimulated luminescence is about 0.6 - 0.8 microseconds. With screen-film imaging these crystals spontaneously luminescence to expose a film, but with CR imaging the luminescence occurs, then there is also photoluminescence that occurs when the screen is stimulated by a narrow beam of infrared light.
The holes or vacancies in the lattice are portions of the lattice normally occupied by halogens (fluoride, bromide, or iodine). These vacancies will trap free electrons when irradiated and are called Farbzentren centers or F-centers.
When the photostimulable plate is exposed to high frequency light, usually from a helium laser, the electrons in these F-centers are liberated and cause luminescence at readout.
THE LATENT IMAGE WILL REMAIN STORED FOR 24 HOURS.IT WILL FADE THROUGH PHOSPHORESCENCE
25% OF STORED ENERGY WITHIN 8 HOURS FADING
CR PLATE CR SCANNER/READER
THE SCANNER SCANS THE IMAGE PLATE WITH LASER LIGHT AND READS THE LATENT IMAGE FROM THE PHOSPHORREADOUT
LASER LIGHTHELIUM-NEON (633 nm) LASER BEAM SWEEPS THE PLATE IN RASTER FASHION
LASER PM TUBE LIGHT GATE AMPLIFIER ADC
SWEEPING OF THE LASER ACROSS THE PLATE • FAST SCAN DIRECTION • SCAN DIRECTION • LASER SCAN DIRECTION
PLATE MOVEMENT IN THE SCANNER • SLOW SCAN DIRECTION • SUB-SCAN DIRECTION • PLATE SCAN DIRECTION
THE SPEED OF THE SCANNING LASER BEAM IS ADJUSTED TO THE LUMINESCENT SIGNAL
LASER 633 nm PHOTOSTIMULABLE LUMINESCENCE 390-400 nm PLATE & F-CENTERS
LASER LASER SPOT SIZE - 100 MICROMETERSPIXEL SIZE - 100 MICROMETERS
P.M. TUBE DETECTION SENSITIVITY MATCHED TO BLUE-PURPLE PSL (390-400 nm)
AFTER SCANNING THE CR PLATE NEED TO BE CLEARED FROM RESIDUAL SIGNALPLATE EXPOSED TO HIGH INTENSITY SODIUM VAPOR OR FLUORESCENT LIGHT