COMPUTED RADIOGRAPHY (CR) - chavatdaat.co.il CR.pdf · Computed radiography. CR 30 -X -Workflow 1...
Transcript of COMPUTED RADIOGRAPHY (CR) - chavatdaat.co.il CR.pdf · Computed radiography. CR 30 -X -Workflow 1...
COMPUTED RADIOGRAPHY (CR)COMPUTED RADIOGRAPHY (CR)Moving with the timeMoving with the time
Avi Avner BVSc BSc CVR DVDI MRCVSAvi Avner BVSc BSc CVR DVDI MRCVS
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CRCR--BasicsBasicsA five step process:
1. X-ray image received on phosphor plate
2. Image extracted from phosphor plate by
Laser (Raw image)
3. Raw image processed for quality
improvement
4. Final image in DICOM format
5. DICOM image can be either printed,
burned on CD, or sent to PACS
CR 30CR 30--X X -- WorkflowWorkflow
1NX Receives DMW (*)
from RIS
5CR 30-X Scans
image
4Identify image (Direct ID)
3Insert cassette in digitizer
6Control image quality
8Cassette ready for next
image
2Take Image
(*) DMW = DICOM Modality worklist
7DICOM Print or Archive
PACS system
Hardcopy printer
CR 30-X Digitizer and NX Modality Workstation
RIS system
Firewire connection
IMAGE PLATEIMAGE PLATE
�� Photosensitive phosphor Photosensitive phosphor
layer (e.g. europium layer (e.g. europium
activated barium activated barium
fluorohalidefluorohalide
�� Thin and flexibleThin and flexible
�� Placed in a conventional Placed in a conventional
cassettecassette
�� Stores the latent image Stores the latent image
after xafter x--ray exposureray exposure
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CONDUCTANCE BAND (LOW ENERGY LEVEL)
VALENCE BAND (HIGH ENERGY LEVEL)
X-Ray
Photon
PHOSPHOR PLATE
PhotoElectron
Trap
UV Photon
Laser
light
PM
Image: Capture, Reading, DetectionExposure,
Exposure
stage
Reading
stage
CR - Physics
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Scanning Procedure
3. Plate is erased with
light (not laser) and
returned to the cassette
2. Blue light (diffused)
is emitted from the
plate and detected by
the photomultiplier
QUALITY CONTROL QUALITY CONTROL WORKSTATIONWORKSTATION
��Digital data transferred Digital data transferred
��Raw data adjusted by Raw data adjusted by
softwaresoftware
��Processing Processing
algorithmalgorithm
��Define contrast, Define contrast,
latitude and edge latitude and edge
enhancementenhancement
Limitations of Limitations of conventional radiologyconventional radiology
�� Films cannot tolerate a wide range in Films cannot tolerate a wide range in
radiation exposure (D logE curve)radiation exposure (D logE curve)
�� One has to chose between good One has to chose between good
contrast and good latitudecontrast and good latitude
�� Image cannot be adjusted once takenImage cannot be adjusted once taken
�� Require space for dark room and film/ Require space for dark room and film/
chemicals storage.chemicals storage.
Limitations of screenLimitations of screen--film film systemssystems
�� Price of films and chemicals is Price of films and chemicals is
constantly going up (4constantly going up (4--10% per year)10% per year)
�� Need several exposures to show Need several exposures to show
different tissues (bone vs soft tissue)different tissues (bone vs soft tissue)
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Advantages of CRAdvantages of CR
�� Image quality comparable with to Image quality comparable with to
conventional screenconventional screen--film systemsfilm systems
�� Wide dynamic rangeWide dynamic range-- ability to image ability to image
structures of different attenuation structures of different attenuation
values (thorax and abd)values (thorax and abd)
�� Reduction of repeat exposuresReduction of repeat exposures
Advantages of CRAdvantages of CR
�� CR is compatible with most CR is compatible with most
conventional xconventional x--ray systemsray systems
�� Increased savings: no film, chemicals, Increased savings: no film, chemicals,
dark room and storage room requireddark room and storage room required
�� Computer processing of raw image: Computer processing of raw image:
brightness, contrast, sharpness brightness, contrast, sharpness
enhancement, zooming, enhancement, zooming,
measurementsmeasurements……
Advantages of CRAdvantages of CR
� CR is more tolerant of under / over exposure (wide latitude)
� Ability to extract information not possible on conventional radiographs (e.g edge enhancement, masking, cropping)
�� Faster image acquisitionFaster image acquisition
Advantages of CRAdvantages of CR
�� DICOMDICOM--Digital imaging Digital imaging
communications in medicinecommunications in medicine
�� PACSPACS-- Images retrieved from Images retrieved from
computer archivecomputer archive
�� TeleradiologyTeleradiology
Disadvantages of CRDisadvantages of CR
�� Initial cost Initial cost
�� Additional costAdditional cost
�� Transition to a new systemTransition to a new system
�� Wider latitude Wider latitude –– Tend to overexposeTend to overexpose--
degrade contrast.degrade contrast.
Disadvantages of CRDisadvantages of CR
�� IP sensitive to fogging: use grid, need IP sensitive to fogging: use grid, need
to be erased dailyto be erased daily
Optimization of imagesOptimization of images
�� Erase plate not used for 24hrsErase plate not used for 24hrs
�� Scatter controlScatter control-- GridGrid
�� Scatter controlScatter control-- avoid overexposureavoid overexposure
�� Centering / collimationCentering / collimation-- histogram histogram
should represent anatomyshould represent anatomy
�� CollimationCollimation-- reduce scatter and reduce scatter and
improves contrastimproves contrast
Optimization of imagesOptimization of images
�� Multiple fields per IPMultiple fields per IP-- not not
recommended.recommended.
�� If multiple fields: uniform distributionIf multiple fields: uniform distribution--
symmetry, strict collimationsymmetry, strict collimation-- no no
overlap.overlap.
Practical tipsPractical tips
�� Systems breakSystems break-- reliable servicereliable service
�� Computer will eventually crash (3Computer will eventually crash (3--
5yrs)5yrs)
�� Vendor reliability (going out of Vendor reliability (going out of
business)business)-- Safety net.Safety net.
�� BackBack--up your system outside the main up your system outside the main
serverserver
Practical tipsPractical tips
�� Purchase price may only be just the Purchase price may only be just the
beginningbeginning-- make sure you know what make sure you know what
you are getting (you may not be you are getting (you may not be
getting the system that was shown to getting the system that was shown to
you)you)
�� Know who is providing your serviceKnow who is providing your service
�� Service: contract, software upgrade, Service: contract, software upgrade,
computer crashes, replacing computercomputer crashes, replacing computer
Practical tips: focus onPractical tips: focus on
�� Image quality Image quality –– Image processing has Image processing has
greatest effect greatest effect
�� MultiMulti--scale Image Contrast scale Image Contrast
Amplification (MUSICAAmplification (MUSICA--Agfa)Agfa)
��MUSICA (Agfa)MUSICA (Agfa) תוכנת עיבוד התמונה תוכנת עיבוד התמונה
מאפשרת קבלת תמונה דיאגנוסטית באיכות מאפשרת קבלת תמונה דיאגנוסטית באיכות
CRCRהגבוהה ביותר הקיימת כיום במערכות הגבוהה ביותר הקיימת כיום במערכות