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.

1. Dr. Muhammad bin zulfiqar
PGR-1
SIMS/ SHL.

3. Basics of Digital
Language

5. Byte
The basic unit of binary coded information
Kilobyte—210 – 1024 bites
Megabyte—1024 times1024bites
5

6. Performance parameters
Pixel: Smallest complete 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
COMPUTED RADIOGRAPHY (CR) DIGITAL RADIOGRAPHY (DR)

10. X-RAYS
CR
CR PLATE
SCANNER
11011101

11. X-RAYS
DR
DETECTORS
11011101

12. Computed Radiography (CR)
Been around 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-usable metal 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

17. CR PLATE

18. CASETTE CONSTRUCTION
LIGHTWEIGHT ALUMINUM
PLASTIC
STEEL FRAME
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.

22. SCATTER

25. REMOTE OPERATOR PANEL

28. CR Operation

29. Add module code number and lesson title
29

30. The principle of PSP
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
electron to
higher energy state
- - - Lower E
nergy - - Electron
- State
- - - -

36. PSP digitizer
(Images courtesy of AFGA)
Add module code number and lesson title
Casette and PSP
Workstation
36

37. Reading Imaging Plate
Reader scans 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
Reader scans 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

39. Conventional CR Scanning

40. 25% OF STORED
ENERGY
WITHIN 8 HOURS

41. CR PLATE
CR SCANNER/READER
CR AFTER
EXPOSURE IS
INSERTED INTO
CR SCANNER

43. CR Exposure & Readout

46. LASER
PM TUBE
LIGHT
GATE
AMPLIFIER
ADC

47. LASER 633 nm
PHOTOSTIMULABLE LUMINESCENCE
390-400 nm
PLATE & F-CENTERS

52. After read-out, plate erased 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 image plate can be
reused thousands of times

54. CR Resolution
Small cassettes have better spatial
resolution
Smaller pixels
More pixels / mm

55. IMAGE CHECK-INDEX

56. IMAGE MANIPULATION-WINDOWING

57. PICTURE DESTINATION -PACS

59. CR CHARACTERISTIC CURVE
VERY WIDE LATITUDE
CR SYSTEMS
LESS RADIOGRAPH REPEATS

60. Much greater latitude
than screen/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 OF FILM
LATITTUDE OF CR

62. IMAGE CAN BE SALVAGED WITH CR
500% OVEREXPOSURE
80% UNDEREXPOSURE
USE ADEQUATE KVP

63. HARD COPY GENERATED IN
LASER PRINTER

64. CR SYSTEM EFFICIENCY CHARACTERISTIC
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 direct digital output
No processor / reader required
Images available in < 15 seconds
Much less work for technologist

69. 69

72. 72

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 .

79. ?