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 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)

CR PLATE

FRONT PANEL MADE OF LOW ATTENUATION CASETTE CONSTRUCTION LIGHTWEIGHT ALUMINUM PLASTIC STEEL FRAME FRONT PANEL MADE OF LOW ATTENUATION CARBON FIBER

CR CASSETTES ARE NOT LIGHT-TIGHT IMAGE 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

REMOTE OPERATOR PANEL

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

PROTECTS PHOSPHOR LAYER 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 THE LATENT IMAGE WILL REMAIN STORED FOR 24 HOURS. IT WILL FADE THROUGH PHOSPHORESCENCE

FADING 25% OF STORED ENERGY WITHIN 8 HOURS

CR AFTER EXPOSURE IS INSERTED INTO CR SCANNER

CR PLATE CR SCANNER/READER

THE SCANNER SCANS THE IMAGE PLATE WITH LASER LIGHT AND READS THE LATENT IMAGE FROM THE PHOSPHOR READOUT

LASER LIGHT HELIUM-NEON (633 nm) LASER BEAM SWEEPS THE PLATE IN RASTER FASHION

RASTER

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

PHOTOSTIMULABLE LUMINESCENCE LASER 633 nm PHOTOSTIMULABLE LUMINESCENCE 390-400 nm PLATE & F-CENTERS

LASER LASER SPOT SIZE - 100 MICROMETERS PIXEL 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 SIGNAL PLATE EXPOSED TO HIGH INTENSITY SODIUM VAPOR OR FLUORESCENT LIGHT

Typical image plate can be reused thousands of times

IMAGE DISPLAY

IMAGE CHECK-INDEX???

IMAGE MANIPULATION-WINDOWING

PICTURE DESTINATION -PACS

PACS

CR CHARACTERISTIC CURVE VERY WIDE LATITUDE

CR SYSTEMS LESS RADIOGRAPH REPEATS

CHARACTERISTIC CURVE LATITTUDE OF FILM LATITTUDE OF CR

IMAGE CAN BE SALVAGED WITH CR 500% OVEREXPOSURE 80% UNDEREXPOSURE USE ADEQUATE KVP

HARD COPY GENERATED IN LASER PRINTER

CR SYSTEM EFFICIENCY CHARACTERISTIC QDE- QUANTUM DETECTION EFFICIENCY NO NEED FOR SCREENS

QDE: THE MEASURE OF THE EFFICIENCY OF CR SYSTEM TO CONVERT REMNANT X-RAYS TO USEFUL IMAGE SIGNAL

QDE PATIENT DOSE

DIGITAL RADIOGRAPHY

ELECTRONIC DETECTORS INDIRECT TECHNIQUE CLASS DIRECT TECHNIQUE CLASS

INDIRECT TECHNIQUE INDIRECT CONVERSION FLAT PANEL DETECTORS INDIRECT CONVERSION CHARGED COUPLE DEVICE DETECTORS

INDIRECT CONVERSION FLAT PANEL DETECTORS USE THIN LAYERS OF SILICON COMBINED WITH THE ARRAYS OF PHOTODIODES. P.D. IS COATED WITH CESIUM IODIDE OR RARE EARTH MATERIAL- WHEN STRUCK BY REMNANT X-RAYS THEY EMIT LIGHT. ADVANTAGE: HIGH QDE DISADVANTAGE: LIGHT DIVERGENCE

PHOTODIODE

INDIRECT CONVERSION CHARGE COUPLED DEVICE DETECTORS USE CCD ARRAYS TO RECORD THE VISIBLE LIGHT EMITTED BY A SCINTILLATION CRYSTAL THAT HAS ABSORBED THE ENERGY. AN OPTICAL COUPLING SYSTEM DEMAGNIFIES THIS LIGHT AND SENDS IT TO THE CCD ARRAY.

OPTICAL COUPLING

CCD

DIRECT TECHNIQUE DIRECT CONVERSION FLAT PANEL DETECTORS

DIRECT CONVERSION FLAT PANEL DETECTORS USE AN AMORPHOUS SELENIUM COATED THIN FILM TRANSISTOR ARRAY THAT DIRECTLY CONVERTS X-RAY ENERGY INTO ELECTRICAL SIGNAL. REMNANT X-RAYS ARE ABSORBED IN THE SELENIUM WHERE THEY FORM ELECTRON-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 COMPARISON DR SYSTEM IMMEDIATE REDOUT CASSETTE FREE OPERATION ADVANTAGE DISADVANTAGE IMMEDIATE REDOUT CASSETTE FREE OPERATION GOOD FOR HIGH VOLUME RADIOGRAPHY CAN BE USED FOR MAMMOGRAPHY DETECTORS CAN BE RE-EXPOSED IMMEDIATELY MORE EXPENSIVE CAN NOT BE USED IN PORTABLE RADIOGRAPHY?????? NOT COMPATIBLE WITH EXISTING TABLES

PORTABLE????

PORTABLE CT???!!

4K MONITORS USED IN MAMMOGRAPHY MONITORS IN DR 1K 2K 4K 1,000 X 1,000 PIXELS 2,000 X 2,000 PIXELS 4,000 X 4,000 PIXELS 4K MONITORS USED IN MAMMOGRAPHY AND CHEST RADIOGRAPHY

DR TERMS TO KNOW PIXEL VOXEL SPATIAL RESOLUTION DYNAMIC RANGE CONTRAST RESOLUTION IMAGE NOISE

PIXEL

.                                                                                                                    VOXEL The formation