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Digital radiography (2013)
Digital radiography provides several advantages over film radiography including improved archiving and distribution of images, higher patient throughput, and potential reduction of patient radiation dose. There are two main types of digital radiography - computed radiography which uses imaging plates and direct radiography which involves intrinsic readout processes without cassettes. Direct radiography can be via direct or indirect conversion and uses flat panel detectors incorporating thin film transistors. Digital images allow various processing techniques and can be stored and shared electronically in picture archiving systems.
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Digital radiography (2013)
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- 2. Why Digital? • Archivingand distribution. • Higher patient throughput. • Increased dose efficiency. • Possible reduction of pt dose.
- 3. Computed Radiography (CR( •1980 • 1st step towards DR
- 4. The Cassette • Photostimulabephosphor detector (PSP). • Storage Phosphors Or Imaging plates. • Barium Flurohalide (BaFBr, BaFI). • 85% BaFBr and 15 % BaFI • Activation by Europium …. Doping …..Defect.
- 6. Exposure and LatentImage X -ray Eu +2 ---------- Eu +3 Free Exited Electron Trapped in F- Center in high energy state
- 7. The Read Out Trappedin F- Center in high energy state HighEnergyLaser Beam Mobile Electron Deexcited Blue Green Light
- 8. Imaging Plate Laser M PMT RedLaser Blue Green Light
- 11. The Read Out •Not all the electrons are released. • Very bright light source.
- 13. Advantages • It’s Digital •Easy implementation (Cassette based). • Portable. • Larger dynamic range .
- 15. Direct Radiography (DR( •No Cassettes. • Intrinsic Read Out process • Two Types: • A) Direct Conversion (X-ray into Electrical charges) • B) Indirect Conversion (Light as intermediate)
- 16. • TFT =Thin Film Transistor. • CCD = Charge Coupled Device. • FPD = Flat Panel Detector. DR ( Direct Radiography( Indirect Conversion Direct Conversion - Scintillator TFT - Scintillator CCD - Image Intensifier - Photoconductor FPD - Selenium Drum
- 17. Direct Conversion • UsePhotoconductor (X-ray Photons to electrical charges by freeing electrons) • Amorphous Selenium, lead iodide, lead oxide.
- 18. Figure 4a. Acquisitionmethods of DR systems: cross section of a direct flat-panel system (a), cross section of an indirect flat-panel system (b), a lens-coupled CCD system (c), a fiberoptic-coupled CCD system (d), and a fiberoptic-coupled scanning array (e). Samei E et al. Radiographics 2004;24:313-334 ©2004by Radiological Society of North America
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- 20. Charge Coupled Device(CCD( • Light sensitive sensor, Consists of: • Array of linked or coupled capacitors. • Scintillator such as Tl- doped cesium iodide • Limited by size
- 21. • Types ofCCD: • Lens Coupled:- • Lower number of photons. • Low signal to noise. • Slot Scan:- • Digital Mammography • Dental Radiography.
- 22. Figure 4c. Acquisitionmethods of DR systems: cross section of a direct flat-panel system (a), cross section of an indirect flat-panel system (b), a lens-coupled CCD system (c), a fiberoptic-coupled CCD system (d), and a fiberoptic-coupled scanning array (e). Samei E et al. Radiographics 2004;24:313-334 ©2004by Radiological Society of North America
- 23. Figure 1. Digitalchest imaging with a slot-scan technique. Kroft L J M et al. Radiology 2004;231:156-163 ©2004by Radiological Society of North America
- 24. Figure 4e. Acquisitionmethods of DR systems: cross section of a direct flat-panel system (a), cross section of an indirect flat-panel system (b), a lens-coupled CCD system (c), a fiberoptic-coupled CCD system (d), and a fiberoptic-coupled scanning array (e). Samei E et al. Radiographics 2004;24:313-334 ©2004by Radiological Society of North America
- 25. Flat Panel Detectors(FPD( • “sandwich” constructions consisting of • a scintillator layer, an amorphous silicon photodiode circuit layer, and a TFT array. • CsI or gadolinuim oxysulfid Crystals.
- 27.
- 28. Patient Dose Consideration •Detective Quantum Efficiency (DQE) • Flat panel detectors (DR) are the best. • 2x – 3x dose reduction compared to CR. • No direct feedback for over exposure !!!!
- 29. DR vs. CR •Time of processing • Spatial resolution • Radiation dose • Flexibility • Setup Costs DR CR CR DR DR
- 30. Hard copy Vs.Soft copy
- 31. Matrix Size • SPECTor PET (128 X 128 )….. 16 KB • MRI ( 256 X 256). • CT (512 X 512)…… 0.5 MB • DSA (1024 X 1024). • Digital Chest X-ray (CR or DR) …???? 3500 X 4300 pixel 32 MB
- 32. Our Monitors • TypicalPC monitor ( 1000 X 1000) can display: • 64 Full resolution SPECT images. • 16 Full resolution MRI images. • 4 Full resolution CT images. • 1/15 Full resolution digital Chest X-ray
- 33.
- 35. Digital Image Correction •Dead Pixels • Dark Images • Gain Correction.
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- 41. Global Image Processing •Altering the relation between digital numbers in the image and displayed brightness. • Noise Reduction. • Smoothing • Sharpen
- 43. Image Processing Basedon Convolution
- 44. Image Processing Basedon Convolution
- 45. Image Processing Basedon Convolution 0 0 0 0 1 0 0 0 0 + + + + = + + + +
- 46. Smoothing and Noisereduction Correction Sharpen
- 47. Adaptive Histogram Equalization •Different window level/ settings. • Different parts of the image. • Smooth transition.
- 48. Figure 3a. CTscans in a 61-year-old man with adenocarcinoma of the lung. Fayad L M et al. Radiology 2002;223:845-852 ©2002by Radiological Society of North America
- 49. Figure 3b. CTscans in a 61-year-old man with adenocarcinoma of the lung. Fayad L M et al. Radiology 2002;223:845-852 ©2002by Radiological Society of North America
- 50. Figure 3c. CTscans in a 61-year-old man with adenocarcinoma of the lung. Fayad L M et al. Radiology 2002;223:845-852 ©2002by Radiological Society of North America
- 51. Picture Archiving and CommunicationSystem PACS
- 52. Uses • Hard copyreplacement • Remote Access • Integration • Workflow management • Back Up
- 54. Digital Imaging and ComunicationIn Medicine
- 55. DICOM • Universal • ImageQuality • Different Data Types
- 56. Laser Processing • LaserCamera • Typically Wet Processing • Use digital images as a source • Silver Cubic Grains • Laser Intensity …. Density
- 57. Dry processing • Usedigital modalities • No chemicals • Adherographic vs. Thermographic
- 58. Diagrams of thewet (left) and dry (right) laser imagers. Gahleitner A et al. Radiology 1999;210:871-875 ©1999 by Radiological Society of North America
Editor's Notes
- #19 Figure 4a. Acquisition methods of DR systems: cross section of a direct flat-panel system (a), cross section of an indirect flat-panel system (b), a lens-coupled CCD system (c), a fiberoptic-coupled CCD system (d), and a fiberoptic-coupled scanning array (e).
- #23 Figure 4c. Acquisition methods of DR systems: cross section of a direct flat-panel system (a), cross section of an indirect flat-panel system (b), a lens-coupled CCD system (c), a fiberoptic-coupled CCD system (d), and a fiberoptic-coupled scanning array (e).
- #24 Figure 1. Digital chest imaging with a slot-scan technique. X rays are collimated into a narrow fan-shaped beam that moves across the chest simultaneously with the detector. The exposure settings are measured in the downward movement of the detector. The detector’s upward movement represents the acquisition scanning process. The image is gradually built up during scanning. The camera incorporates CCD and time-delay integration technology.
- #25 Figure 4e. Acquisition methods of DR systems: cross section of a direct flat-panel system (a), cross section of an indirect flat-panel system (b), a lens-coupled CCD system (c), a fiberoptic-coupled CCD system (d), and a fiberoptic-coupled scanning array (e).
- #49 Figure 3a. CT scans in a 61-year-old man with adenocarcinoma of the lung. (a) Original transverse CT image displayed with conventional window settings specific for lung tissue demonstrates two large nodules (N1, N2) in the right upper lobe, adjacent bullae (B), and right posterior pleural thickening (PL).(b) Original transverse CT image displayed with conventional window settings specific for mediastinal tissue demonstrates several small precarinal (LN1) and aortopulmonary (LN2) lymph nodes. (c) Transverse CT image displayed with CLAHE enhancement. (d) Transverse CT image displayed with MAHE enhancement.
- #50 Figure 3b. CT scans in a 61-year-old man with adenocarcinoma of the lung. (a) Original transverse CT image displayed with conventional window settings specific for lung tissue demonstrates two large nodules (N1, N2) in the right upper lobe, adjacent bullae (B), and right posterior pleural thickening (PL).(b) Original transverse CT image displayed with conventional window settings specific for mediastinal tissue demonstrates several small precarinal (LN1) and aortopulmonary (LN2) lymph nodes. (c) Transverse CT image displayed with CLAHE enhancement. (d) Transverse CT image displayed with MAHE enhancement.
- #51 Figure 3c. CT scans in a 61-year-old man with adenocarcinoma of the lung. (a) Original transverse CT image displayed with conventional window settings specific for lung tissue demonstrates two large nodules (N1, N2) in the right upper lobe, adjacent bullae (B), and right posterior pleural thickening (PL).(b) Original transverse CT image displayed with conventional window settings specific for mediastinal tissue demonstrates several small precarinal (LN1) and aortopulmonary (LN2) lymph nodes. (c) Transverse CT image displayed with CLAHE enhancement. (d) Transverse CT image displayed with MAHE enhancement.
- #59 Diagrams of the wet (left) and dry (right) laser imagers. In the wet laser imager, the film is taken out of the supply cartridge (A) and exposed with a laser beam in a z pattern (B). After exposure, the film goes through a conventional development, fixation, and washing procedure (C) before being delivered at the receive tray (D). In the dry laser imager, a similar procedure is used to expose the dry laser film, except that the film is exposed in two directions instead of in only one to achieve the higher level of exposure required for this type of film (B). In the next step (C), the dry laser film is then exposed to controlled heat of about 140°C for a few seconds, which is sufficient to transform the latent image into a permanent image.