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Cr & dr
This document provides an overview of computed radiography (CR), a type of digital radiography. CR uses reusable imaging plates coated with photostimulable phosphor instead of film. When exposed to x-rays, the plate stores a latent image. A scanner then reads the plate with a laser, causing the phosphor to release visible light photons. A photomultiplier tube converts the light into electrical signals representing the image. CR offers benefits over film such as wider exposure latitude, immediate digital images, and reusability of plates. The document also discusses pixel size, gray scale, spatial resolution, contrast resolution, and file size as key performance parameters of digital images.
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Cr & dr
- 1. Dr. Muhammad binzulfiqar PGR-1 SIMS/ SHL.
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- 5. Byte The basic unitof binary coded information Kilobyte—210 – 1024 bites Megabyte—1024 times1024bites 5
- 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. Performance Parameters(contd..) Spatial Resolution:finer details, 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.
- 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 Ba FX:Eu +2 BASE 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. The principle ofPSP PMT ADC CB Trap Excitation Storage Add module code number and lesson title Emission 30
- 33. - X-Ray Photon Higher E nergy Electron State P hoton pumps electronto higher energy state - - - Lower E nergy - - Electron - State - - - -
- 36. PSP digitizer (Images courtesyof AFGA) Add module code number and lesson title Casette and PSP Workstation 36
- 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 Electron State Lower Energy Elect ron St at e - - - - - - - - - - - - - - - -
- 38. Reading Imaging Plate Readerscans plate with laser light using rotating mirror Film pulled through scanner by rollers Light given off by plate measured by PM tube & recorded by computer
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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. LASER 633 nm PHOTOSTIMULABLELUMINESCENCE 390-400 nm PLATE & F-CENTERS
- 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 OFFILM LATITTUDE OF CR
- 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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