Overview of CR and DR

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Overview of CR and DR

• Gyeongsang National University Hospital
• Department of Diagnostic Radiology
• Radiation Technologist You Dai In

2
Direct Radiography (DR)

• Overview of DR systems
• CCD based systems
• TFT Phosphor
• TFT Photoconductor

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Detector technologyCCD based systems
A. Lens Coupling
B. Fiber optic coupling
C. multiple detectors
A phosphor screen converts X-rays into visual
light that is projected onto a CCD or onto a
CCD-array
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CCD based systems

• Mature technology
• Mostly dedicated applications mammography,
  chest
• FDA approved except for mammography

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Detector technologyTFT Phosphor
Phosphor screen converts X-ray photons into
visual photons.
Phosphor
Photodiode converts visual photons into electrons
Electrons are stored on capacity of switching
element
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TFT Phosphor

• GOS systems available on the market
• CsI systems limited availability
• FDA approved

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Detector technologyTFT Photoconductor
Charge transport in photoconductor
Electrons migrate to surface electrode
Electrons are stored on capacity of switching
element
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TFT Photoconductor
Experimental except Hologics
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Weaknesses of TFT systems

• Low yield of TFT array fabrication
• Ghost images
• Charge trapping in amorphous semiconductors
• Clustering of Tl dopant in CsI needles
• Limited dynamic range (a- Se) due to high dark
  current
• Image deformation beyond wgtNyquist due to
  aliassing (a-Se)
• Electronic noise in low dose applications
• Detector damage at high dose (capacitor overload)

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Principle of CR
Galvanometer
Photomultiplier
Electrical Signal
Laser
Light guide
A/D
Storage phosphor plate
Digitisation
Rollers
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Computed Radiography

• Mature and robust technology
• FDA approved and clinically accepted for all
  applications except mammography

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CR and DR Economics

• Flat Panel
• Investment 250-300K forone room
• 100K to replace damaged detectorDR 20 higher
  productivity
• 6 pat./h x 2exp./pat. x 10h/day x 200 days/yr
  24 000 exp/yr
• 1 room 24 000 exp./yr
• Amortisation 5 yrs 120 000 exp.
• 350 000 / 120 000 exp. 2.90/exp.

• CR
• Investment 150K for 3 to 4 rooms
• 1K to replace damaged detectorCR productivity
  conventional
• 5 pat./h x 2exp./pat. x 10h/day x 200 days/yr
  20 000 exp/yr
• 3 rooms 60 000 exp./yr
• Amortisation 5 yrs 300 000 exp.
• 150 000 / 300 000 exp. 0.50/exp.

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CR/DR world market evolution 1996-2005
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Assumptions

• Penetration of digital acquisition in the x ray
  rooms will evolve from 2.5 in 1999 to 11 in
  2005
• Within this digital segment, DR will substitute
  CR differently according to the application
• Mobile 100 retention of CR by 2005
• Chest 0 retention of CR
• General Rad high end 70 retention of CR
• General Rad low end 85 retention of CR

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CR and DR
New flat panel digital detectors are compact,
offer fast image acquisition and promise
excellent image quality
CR
DR Flat panel
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Evolution of Digital Radiography Detector
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Innovation in Plate technology

• more absorption
• higher sharpness
• higher image quality

state of the art CR
Powder Phosphor BaFBr
Needle Phosphor CsBr
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New CsBrEu PhosphorHigher image quality

• Cubic crystal facilitates needle growth
• Equivalent specific X-ray absorption (? 4.44
  vs. 5.1 g/cm3)
• Efficient stimulation with diode laser
  (stimulation 685 nm)
• Efficient detection with PMT or CCD (emission 450
  nm)
• Excellent storage phosphor
• Conversion efficiency gt BaFBrEu
• (more light / absorbed X-ray)
• Lower stimulation energy
• ? Read-out requires 3 times less laser power

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DQE, 2,5 µGy (SC 400) 70 kV, 0.5mm Cu-Filter
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Scanhead line scannerHigher throughput

• Fast acquisition (5s scan, 20s cycle)
• QE CCD gt QE PMT ? Higher gain

Flying Spot Scanhead ? Scan pixel
per pixel ? Scan line per line ? Detector
Photomultiplier ? Detector CCD
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Scanhead - Scanning Principles
CCD Sensor
Laser Diode Array
CCD Sensor
Optics
Optics
Image Plate
Image Plate
Laser Diode Array
Front-Stimulation ADC Stratus
Back-Stimulation CR Panel
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Scanhead - 17 Front stimulation
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Scanhead - 17 Prototype(Back-Stimulation)
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Scanhead, the unifying technology
(DR)

Scanhead

• simple
• mature
• robust
• economic
• multi-application

Phosphor Image Plate

• fast
• compact
• integrated
• higher image quality

AGFA - Patent
25
Ideal DR System
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DR Detector Technologies
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CR and DR DQE
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DQE
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Conclusions

• The different technologies will coexist
• Best choice will depend on application
• CR potential is promising
• The difference between CR and DR technology will
  become less relevant