Cr & dr

Dr. Muhammad bin zulfiqarPGR-1 SIMS/ SHL.

Basics of Digital Language

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ByteThe basic unit of binary coded information

Kilobyte—210 – 1024 bites

Megabyte—1024 times1024bites

Performance parametersPixel: Smallest complete sample of an image. Has

a varied set of tones in shades of white/ black/grey. Expressed in binary codes (bits).

Size of the pixel : Smaller the size , better resolution.

CR- 50 to 200 microns, DR- 100 to 200 microns, DM- 50 to 100 microns.

Gray Scale: Shades of Gray in between pure black and pure white.

Bit Depth: No of shades to define each pixel ,measured as no of bits. Larger the depth, incr gray scale and large file size.

Spatial Resolution: finer details, diff objects in an image. Depends on sampling frequency and no of pixels.

expressed in lp/mm.Contrast Resolution: Color or gray scale

differentiation. Indicate the no of shades of grey that a detector can capture.

File Size.

Performance Parameters(contd..)

DIGITAL PROJECTION RADIOGRAPHY

COMPUTED RADIOGRAPHY (CR) DIGITAL RADIOGRAPHY (DR)

11011101

CRX-RAYS

CR PLATE

SCANNER

DETECTORS

11011101

DRX-RAYS

Computed Radiography (CR)Been around since 1980-81Uses same radiographic equipment

No change in X-ray machineUses an imaging plate

Contains a photostimulator phosphorNeed a cassette readerImages can be sent to a PACS

Computed Radiography (CR)

Re-usable metal imaging plates replace film & cassette

Uses conventional bucky & x-ray equipment

CR SYSTEM COMPONENTS

CASSETTES (phosphor plates)ID STATIONIMAGE PREVIEW STATIONDIGITIZERVIEWING STATION

CR PLATE

CASETTE CONSTRUCTIONLIGHTWEIGHT ALUMINUMPLASTICSTEEL FRAME

FRONT PANEL MADE OF LOW ATTENUATION CARBON FIBER

PROTECTIVE LAYER

PHOSPHOR LAYER

ANTI-HALO & REFLECTIVE LAYER

BASE

BACKING LAYER

PHOSPHOR LAYER BASEBa FX: Eu +2 PET- POLYETHYLENE

TERAPHTALATE

PROTECTIVE LAYERFLUORINATED POLYMER MATERIAL

PROTECTS PHOSPHOR LAYER

ANTI-HALO LAYER + REFLECTIVE LAYERPREVENTS LASER FROM PASSING THROUGH.REFLECTED LIGHT FROM PHOSPHOR IS

ALLOWED TO PASS.

BACKING LAYERPROTECTS THE BASE FROM DAMAGE.

SCATTER

REMOTE OPERATOR PANEL

CR Operation

Add module code number and lesson title 29


The principle of PSP

Excitation Storage Emission

CB

Trap

ADCPMT

Higher EnergyElectronState

Lower EnergyElectronState

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X-RayPhoton

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Photon pumpselectron tohigher energy state


(Images courtesy of AFGA)

PSP digitizer Casette and PSP

Workstation

Reading Imaging Plate

Reader scans plate with laser

Laser releaseselectrons trapped inhigh energystates

Electrons fall to lowenergy states

Electrons give upenergy as visible light

Laser Beam

Higher EnergyElectronState

Lower EnergyElectronState

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Lower Energy Electron State

Reader scans plate with laser light using rotating mirror

Film pulled through scanner by rollers

Light given off by plate measured byPM tube &recorded by computer

Reading Imaging Plate

Conventional CR Scanning

25% OF STORED ENERGY

WITHIN 8 HOURS

CR PLATE

CR SCANNER/READER

CR AFTER EXPOSURE IS INSERTED INTO CR SCANNER

CR Exposure & Readout

PM TUBE

AMPLIFIER ADC

LASER

LIGHTGATE

PLATE & F-CENTERS

LASER 633 nm

PHOTOSTIMULABLE LUMINESCENCE

390-400 nm

After read-out, plate erased using a bright light

Plate can be erased virtually without limit

Plate life defined not by erasure cycles but by physical wear

IMAGE DISPLAY

Typical image plate can be reused thousands of

times

CR ResolutionSmall cassettes have better spatial

resolutionSmaller pixelsMore pixels / mm

IMAGE CHECK-INDEX

IMAGE MANIPULATION-WINDOWING

PICTURE DESTINATION -PACS

CR CHARACTERISTIC CURVEVERY WIDE LATITUDE

CR SYSTEMSLESS RADIOGRAPH REPEATS

Much greater latitude than screen/film

Plate responds to many decades of input exposureunder / overexposures

unlikely

Computer scale inputs exposure to viewable densitiesUnlike film, receptor separate

from viewer

CHARACTERISTIC CURVE

LATITTUDE OF CR

LATITTUDE OF FILM

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

Receptor provides direct digital outputNo processor / reader required

Images available in < 15 secondsMuch less work for technologist

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PACS and DICOM THE ROLE OF PACS : A Picture Archiving and Communication System (PACS) aims to

replace conventional analogue film and paper clinical request forms and reports with a completely computerized electronic network whereby digital images are viewed on monitors in conjunction with the clinical details of the patient and the associated radiological report displayed in electronic format.

The ROLE OF DICOM: Digital Imaging and Communications in Medicine (DICOM) is a

standard for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol.

DICOM enables the integration of scanners, servers, workstations, printers, and network hardware from multiple manufacturers into a picture archiving and communication system (PACS). The different devices come with DICOM conformance statements which clearly state the DICOM classes they support. DICOM has been widely adopted by hospitals .

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Education

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