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Overview of CR and DR

Overview of CR and DR. Gyeongsang National University Hospital Department of Diagnostic Radiology Radiation Technologist: You Dai In. Direct Radiography (DR). Overview of DR systems CCD based systems TFT + Phosphor TFT + Photoconductor. Detector technology:CCD based systems.

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Overview of CR and DR

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  1. 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

  3. Detector technology:CCD 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

  4. CCD based systems • Mature technology • Mostly dedicated applications: mammography, chest • FDA approved except for mammography

  5. Detector technology:TFT + 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

  6. TFT + Phosphor • GOS systems: available on the market • CsI systems: limited availability • FDA approved

  7. Detector technology:TFT + Photoconductor Charge transport in photoconductor Electrons migrate to surface electrode Electrons are stored on capacity of switching element

  8. TFT + Photoconductor Experimental except Hologics

  9. 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 w>Nyquist due to aliassing (a-Se) • Electronic noise in low dose applications • Detector damage at high dose (capacitoroverload)

  10. I I 0 I I 00 I I 00 I 00 I 0 I 0 I I I Principle of CR Galvanometer Photomultiplier Electrical Signal Laser Light guide A/D Storage phosphor plate Digitisation Rollers

  11. Computed Radiography • Mature and robust technology • FDA approved and clinically accepted for all applications except mammography

  12. 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. CR and DR: Economics

  13. CR/DR world market evolution 1996-2005

  14. 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

  15. CR and DR New flat panel digital detectors are compact, offer fast image acquisition and promise excellent image quality CR DR Flat panel

  16. Evolution of Digital Radiography Detector

  17. Innovation in Plate technology • more absorption • higher sharpness • higher image quality “state of the art CR” Powder Phosphor BaFBr Needle Phosphor CsBr

  18. New CsBr:Eu 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 > BaFBr:Eu (more light / absorbed X-ray) • Lower stimulation energy  Read-out requires 3 times less laser power

  19. DQE, 2,5 µGy (SC 400) 70 kV, 0.5mm Cu-Filter

  20. Galvo Collimator Laser Light Beam Scan-Head SHT Phosphor Image Plate Fiber Optic Phosphor ImagePlate Photo Detector Scanhead line scanner:Higher throughput Flying Spot Scanhead  Scan: pixel per pixel  Scan: line per line  Detector: Photomultiplier  Detector: CCD Fast acquisition (5s scan, 20s cycle) QE CCD > QE PMT  Higher gain

  21. 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

  22. Scanhead - 17” Front stimulation

  23. Scanhead - 17” Prototype(Back-Stimulation)

  24. CR 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

  26. DR Detector Technologies

  27. CR and DR DQE

  28. DQE

  29. 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

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