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Uploaded byDr. Muhammad Bin Zulfiqar
Cr & dr
Computed radiography (CR) uses phosphor plates instead of film to capture x-rays, producing a digital image. The plate is scanned with a laser, releasing electrons trapped during exposure. The electrons emit light detected by a photomultiplier tube and converted to a digital image. CR offers advantages over film like a wide exposure latitude, reusable plates, and faster digital images. The digital files can be stored and shared using PACS and DICOM standards.
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Cr & dr
- 1. Dr. Muhammad binzulfiqar PGR-1 SIMS/ SHL.
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- 5. 5 Byte The basic unitof binary coded information Kilobyte—210 – 1024 bites Megabyte—1024 times1024bites
- 6. Performance parameters Pixel: Smallestcomplete sample of an image. Has a varied set of tones in shades of white/ black/grey. Expressed in binary codes (bits). Size of the pixel : Smaller the size , better resolution. CR- 50 to 200 microns, DR- 100 to 200 microns, DM- 50 to 100 microns. Gray Scale: Shades of Gray in between pure black and pure white. Bit Depth: No of shades to define each pixel ,measured as no of bits. Larger the depth, incr gray scale and large file size.
- 7. Spatial Resolution: finerdetails, diff objects in an image. Depends on sampling frequency and no of pixels. expressed in lp/mm. Contrast Resolution: Color or gray scale differentiation. Indicate the no of shades of grey that a detector can capture. File Size. Performance Parameters(contd..)
- 9. DIGITAL PROJECTION RADIOGRAPHY COMPUTEDRADIOGRAPHY (CR) DIGITAL RADIOGRAPHY (DR)
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- 12. Computed Radiography (CR) Beenaround since 1980-81 Uses same radiographic equipment No change in X-ray machine Uses an imaging plate Contains a photostimulator phosphor Need a cassette reader Images can be sent to a PACS
- 14. Computed Radiography (CR) Re-usablemetal imaging plates replace film & cassette Uses conventional bucky & x-ray equipment
- 15. CR SYSTEM COMPONENTS CASSETTES(phosphor plates) ID STATION IMAGE PREVIEW STATION DIGITIZER VIEWING STATION
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- 18. CASETTE CONSTRUCTION LIGHTWEIGHT ALUMINUM PLASTIC STEELFRAME FRONT PANEL MADE OF LOW ATTENUATION CARBON FIBER
- 19. PROTECTIVE LAYER PHOSPHOR LAYER ANTI-HALO& REFLECTIVE LAYER BASE BACKING LAYER
- 20. PHOSPHOR LAYER BASE BaFX: Eu +2 PET- POLYETHYLENE TERAPHTALATE PROTECTIVE LAYER FLUORINATED POLYMER MATERIAL PROTECTS PHOSPHOR LAYER
- 21. ANTI-HALO LAYER +REFLECTIVE LAYER PREVENTS LASER FROM PASSING THROUGH. REFLECTED LIGHT FROM PHOSPHOR IS ALLOWED TO PASS. BACKING LAYER PROTECTS THE BASE FROM DAMAGE.
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- 29. Add module codenumber and lesson title 29
- 30. Add module codenumber and lesson title 30 The principle of PSP Excitation Storage Emission CB Trap ADC PMT
- 33. Higher Energy Electron State Lower Energy Electron State - - - - - - - - - - - - - - - - - - - - - - - - - - - X-Ray Photon - Photonpumps electron to higher energy state
- 36. Add module codenumber and lesson title 36 (Images courtesy of AFGA) PSP digitizer Casette and PSP Workstation
- 37. Reading Imaging Plate Readerscans plate with laser Laser releases electrons trapped in high energy states Electrons fall to low energy states Electrons give up energy as visible light Laser Beam Higher Energy Elect ron St at e Lower Energy Elect ron St at e - - - - - - - - - - - - - - - - - - - - - - - - - - - - Lower Energy Electron State
- 38. Reader scans plate withlaser light using rotating mirror Film pulled through scanner by rollers Light given off by plate measured by PM tube & recorded by computer Reading Imaging Plate
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- 41. CR PLATE CR SCANNER/READER CRAFTER EXPOSURE IS INSERTED INTO CR SCANNER
- 43. CR Exposure &Readout
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- 47. PLATE & F-CENTERS LASER633 nm PHOTOSTIMULABLE LUMINESCENCE 390-400 nm
- 52. After read-out, plateerased using a bright light Plate can be erased virtually without limit Plate life defined not by erasure cycles but by physical wear
- 53. IMAGE DISPLAY Typical imageplate can be reused thousands of times
- 54. CR Resolution Small cassetteshave better spatial resolution Smaller pixels More pixels / mm
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- 59. CR CHARACTERISTIC CURVE VERYWIDE LATITUDE CR SYSTEMS LESS RADIOGRAPH REPEATS
- 60. Much greater latitude thanscreen/film Plate responds to many decades of input exposure under / overexposures unlikely Computer scale inputs exposure to viewable densities Unlike film, receptor separate from viewer
- 61. CHARACTERISTIC CURVE LATITTUDE OFCR LATITTUDE OF FILM
- 62. IMAGE CAN BESALVAGED WITH CR 500% OVEREXPOSURE 80% UNDEREXPOSURE USE ADEQUATE KVP
- 63. HARD COPY GENERATEDIN LASER PRINTER
- 64. CR SYSTEM EFFICIENCYCHARACTERISTIC QDE- QUANTUM DETECTION EFFICIENCY NO NEED FOR SCREENS QDE: THE MEASURE OF THE EFFICIENCY OF CR SYSTEM TO CONVERT REMNANT X-RAYS TO USEFUL IMAGE SIGNAL QDE PATIENT DOSE
- 66. Receptor provides directdigital output No processor / reader required Images available in < 15 seconds Much less work for technologist
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- 77. PACS and DICOM THE ROLE OF PACS : A Picture Archiving and Communication System (PACS) aims to replace conventional analogue film and paper clinical request forms and reports with a completely computerized electronic network whereby digital images are viewed on monitors in conjunction with the clinical details of the patient and the associated radiological report displayed in electronic format. The ROLE OF DICOM: Digital Imaging and Communications in Medicine (DICOM) is a standard for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol. DICOM enables the integration of scanners, servers, workstations, printers, and network hardware from multiple manufacturers into a picture archiving and communication system (PACS). The different devices come with DICOM conformance statements which clearly state the DICOM classes they support. DICOM has been widely adopted by hospitals .
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