Digital radiography (2013)
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Basics of Digital radiography including CR, DR and digital image processing.
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Digital radiography (2013)
- 2. Why Digital? • Archiving and distribution. • Higher patient throughput. • Increased dose efficiency. • Possible reduction of pt dose.
- 3. Computed Radiography (CR( • 1980 • 1st step towards DR
- 4. The Cassette • Photostimulabe phosphor detector (PSP). • Storage Phosphors Or Imaging plates. • Barium Flurohalide (BaFBr, BaFI). • 85% BaFBr and 15 % BaFI • Activation by Europium …. Doping …..Defect.
- 6. Exposure and Latent Image X -ray Eu +2 ---------- Eu +3 Free Exited Electron Trapped in F- Center in high energy state
- 7. The Read Out Trapped in F- Center in high energy state HighEnergyLaser Beam Mobile Electron Deexcited Blue Green Light
- 8. Imaging Plate Laser M PMT Red Laser 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 • Use Photoconductor (X-ray Photons to electrical charges by freeing electrons) • Amorphous Selenium, lead iodide, lead oxide.
- 18. 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). Samei E et al. Radiographics 2004;24:313-334 ©2004by Radiological Society of North America
- 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 of CCD: • Lens Coupled:- • Lower number of photons. • Low signal to noise. • Slot Scan:- • Digital Mammography • Dental Radiography.
- 22. 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). Samei E et al. Radiographics 2004;24:313-334 ©2004by Radiological Society of North America
- 23. Figure 1. Digital chest 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. 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). 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. Wireless Era
- 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 • SPECT or 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 • Typical PC 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
- 35. Digital Image Correction • Dead Pixels • Dark Images • Gain Correction.
- 37. Dead Pixel
- 38. Dark Noise
- 40. Gain Correction
- 41. Global Image Processing • Altering the relation between digital numbers in the image and displayed brightness. • Noise Reduction. • Smoothing • Sharpen
- 43. Image Processing Based on Convolution
- 44. Image Processing Based on Convolution
- 45. Image Processing Based on Convolution 0 0 0 0 1 0 0 0 0 + + + + = + + + +
- 46. Smoothing and Noise reduction Correction Sharpen
- 47. Adaptive Histogram Equalization • Different window level/ settings. • Different parts of the image. • Smooth transition.
- 48. Figure 3a. CT scans 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. CT scans 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. CT scans 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 Communication System PACS
- 52. Uses • Hard copy replacement • Remote Access • Integration • Workflow management • Back Up
- 54. Digital Imaging and Comunication In Medicine
- 55. DICOM • Universal • Image Quality • Different Data Types
- 56. Laser Processing • Laser Camera • Typically Wet Processing • Use digital images as a source • Silver Cubic Grains • Laser Intensity …. Density
- 57. Dry processing • Use digital modalities • No chemicals • Adherographic vs. Thermographic
- 58. Diagrams of the wet (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
- 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).
- 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).
- 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.
- 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).
- 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.
- 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.
- 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.
- 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.