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1. COMPUTED & DIGITAL
RADIOGRAPHY

2. Digital X-ray Technology
There are two ways to obtain Digital X-rays:
• Computed Radiography
• Digital Radiography

3. Computed Radiography (CR)
• A Digital way of doing general radiography
with Conventional X-ray machines

4. What is CR?
• Computed Radiography (CR) is a process of capturing
radiographic data from a conventional X-ray machine and
processing the data digitally to produce crisp and high quality
radiographic images

5. What is CR?…
• For exposure, an Imaging Plate (IP) is placed in a
cassette instead of a piece of film. The IP captures
and "stores" the X-rays
• The image is "developed" in a CR reader instead of
a film processor. The CR reader extracts the
information stored in the plate and produces a
digital image

6. What is CR?…
• Computed Radiography is a digital image
acquisition process that produces images that
have much better contrast than a
Conventional X-ray film-screen system

7. Basic Modules of CR
MA
TRIX
LR 3300
Digitizer
Preview & ID Station
Processing Server
ID Tablet
Laser Camera
Cassette with
Imaging Plate

8. Imaging Plate (IP)
• The Imaging Plate looks like the intensifying screens found
in Conventional film-screen cassettes
• They are made of photostimulable phosphor

9. Imaging Plate (IP)
• Instead of emitting light immediately when
exposed to X-rays, the photostimulable phosphor
has the special property of storing the X-ray
energy in a latent form and releasing the same
when stimulated by a laser energy in the CR
Reader / Digitizer

10. Imaging Plate (IP)…
• Storage phosphors are unique because they respond to a
very wide range of X-ray exposures
• This latitude gives the flexibility in selecting X-ray
technique and takes care of under or over exposure
• Regardless of the exposure, the image can be displayed
correctly
• As a consequence, retakes due to inappropriate exposures
are drastically reduced

11. Storage phosphor principle
laser stimulation
Emission
Absorption
x-rays
electron
trap
electron
trap

12. Storage phosphor principle…
• The imaging plate is coated with photostimulable phosphor,
also called storage phosphor
• The phosphor material is generally a kind of
Bariumfluorohalide
• The Imaging Plate contains not only the phosphor layer,
but also a protective coat, a conductive layer, support and
laminate layers

13. Storage phosphor principle…
• Incident X-rays excite electrons into a higher energy
level (electron traps)
• A latent image is created in the form of “stored
energy”
• Stimulation with a scanning laser beam releases
electrons
• Typical wavelength of the stimulating laser is 633 nm
• Falling back, electrons emit luminescent light
• Typical wavelength of the emitted light is 390 nm

14. CR Readout

15. Storage phosphor principle…
• The emitted light intensity is proportional to the original
incident X-ray intensity
• The emitted light is captured with an optical array and a
photomultiplier and is digitized
• The residual image is erased from the plate by an intense light
source, which returns all electrons to their original state. This
makes the plate ready to be reused for new exposures

16. • The storage phosphor plate fits inside a standard
size cassette and is exposed to X-rays exactly like
film
• The X-ray energy is stored on the plate in the
form of latent energy
How is a Storage Phosphor plate
exposed?

17. Patient ID Station
• Before exposing the cassette, the patient
demographic and exam data is stored on
the microchip attached on cassette
• This is done by inserting the cassette in a
slot of ID station and entering the data with
the help of keyboard
• When cassette is inserted in digitizer after
X-ray exposure, the digitizer reads both
patient data as well as X-ray exposure data
• The two data are combined to display
images along with patient data

18. Digitizer
• The plate is inserted into the digitizer
where it is scanned with a high power
laser
• The laser light causes the storage
phosphors to release the energy they have
captured in the form of blue light
• In the digitizer, this blue light energy is
converted to electrical signals which are
then digitized to produce digital images

19. What happens to a Storage Phosphor
Plate after it is scanned?
• After exposure and scanning, the phosphor plate is
"erased" by exposing to a bright light exposure within the
digitizer
• The previous image stored in the phosphors is removed
and the plate is ready to be exposed again

20. Workstation
• The digitized image data is
processed on a processing
server and is displayed on
its monitor

21. How many times can we use a Storage
Phosphor Plate?
• The life of a phosphor plate depends on how carefully it
is handled. Physical damage to the plate will limit its
useful life
• If properly cared for, a plate will produce thousands of
images
• Imaging Plates are known to last more than 50000
Exposure Cycles

22. Does CR require X-ray machine
replacement?
• No, CR uses the existing X-ray equipment
• One CR system can support multiple x-ray rooms

23. How is the workflow different with CR ?
• Instead of taking the film cassette to a dark room for
processing, the technologist takes the cassette with
imaging plate to the CR reader for digital processing of
the image
• Instead of manually taking the films to the reporting
radiologists , the softcopy images reach the workstation
almost immediately

24. How is the workflow different with CR
?…
• The time required to acquire a Digital image is much less
compared to conventional darkroom process
• The film is the first product in Conventional where as the
film is the last product in CR

25. CR WORKFLOW
Rx
Network
Digitizer
Printing
MA
TRIX
LR 3300
Identification
Processing server
Exposure
Cassette with Imaging Plate

26. Rx
Network
Digitizer
Printing
MA
TRIX
LR 3300
Identification
Processing server
Exposure
Cassette with Imaging Plate
The cassettes fit into X-ray table. After the exposure, the cassette is identified in the ID-station. Here patient
and exam related information is stored. Next the digitizer reads the identification data, handles the plates, reads
the image and sends out a raw dataset in DICOM-format. The automatic processing server processes the image
according to the type of exam. For each type of exam, an optimized image processing parameter set-up is used.
The processing server then pushes the processed image to the preview station for previewing. After approval
the image is routed to other destinations such as a printer, a review station and an archive server.

27. Digital Radiography
This technique is performed by digital X-ray machines with
flat panel detectors

28. Digital Radiography
Digital Radiography uses two types of
detectors:
• Direct
• Indirect

29. • TFT = THIN-FILM TRANSISTOR ARRAY

30. Indirect detectors
Uses a two
step process
that first
converts X-
rays into
light, then
converts
that light
energy into
electronic
signals

31. Direct detectors
• Direct detectors automatically convert
X-rays into electronic signals.
• X-rays interact with semiconductor
material
• Amorphous selenium
• X-rays converted directly into electrical
charge
• No intermediate steps

32. Direct detectors
• The flat panel detector consists of an amorphous
selenium semiconductor X-ray absorber coating over
a thin-film transistor array of amorphous silicon
• In this system,X-ray photons are immediately
converted into electronic signal
• This immediate conversion eliminates the need for
additional steps to capture and convert incident X-ray
energy
• Corrective image processing which can result in
increased image noise is reduced with the highly
efficient X-ray energy conversion of direct DR

33. Limitations of Conventional X-ray process
(X-ray film / Screen/Darkroom)
• Film has a limited exposure latitude i.e less detail contrast
• Time consuming & cumbersome
• Intolerant to exposure errors
• Repeat X-rays ( More radiation exposure )
• Film wastage

34. Limitations of Conventional X-ray process (X-
ray film / Screen/Darkroom)…
• Cannot be duplicated without loss of quality
• Film storage is a problem
• Scatter radiation reduces contrast and increases patient
dose
• Quality control is an issue

35. What are the advantages of
Digital X-rays?
• Post processing (soft tissue and bony details can be
viewed at same time )
• Reduction in hazardous X-ray dose to patients
• More info on one image
• Constant image quality
• Possibility of viewing X-ray images wherever
needed

36. What are the advantages of
Digital X-rays?…
• Digital images are of extremely high quality
• Digital images have a future scope of better image
management
• Facility of giving multiple images of investigative studies
on a single high definition laser film

37. How is Digital X-ray similar to Conventional
basic radiography process ?…
• Radiography consists of following functions:
-Image data acquisition
-Image processing
-Reproduction of image
-Storage

38. How is Digital X-ray similar to
Conventional basic radiography process
?…
• In Screen film system, all the processes are done on the X-
ray film itself which is used for:
-Image data acquisition
-Image reproduction
-Storage

39. How is Digital X-ray similar to Conventional
basic radiography process ?…
On the other hand, Digital X-ray distributes all the
processes into different stages:
• Imaging plate and digitizer are used for
image data acquisition in CR and Amorphous Selenium
detector array in DR
• Processing server is used for image processing and
storage
• Workstation monitor is used for image reproduction

40. What is the role of Digital X-ray
in PACS Environment?
• Digital X-ray is the only film less way to link the existing
general radiography set up into the digital environment of
PACS

41. Features of Digital X-ray
• Image enhancement
• Printing
• Annotation
• Black border
• Panoramic dental package
• Full leg / Full Spine

42. Under/over exposure

43. Soft tissue and bone windows

44. Digital image manipulation
• Image pre-processing
• Scale the data to appropriate range
• Contrast enhancement – Anatomy specific grayscale
manipulation
• Spatial frequency enhancement

45. Soft tissue and bone windows

46. Zoom

47. Collimation

48. Collimation
MISS.PADMINI 20YRS,F 14/08/2004 20:15:01
SKULL, MASTIODS 23
MISS.PADMINI 20YRS,F 14/08/2004 20:17:01
SKULL, MASTIODS 23
MISS.PADMINI 20YRS,F 14/08/2004 20:15:01
SKULL, MASTIODS 23
MISS.PADMINI 20YRS,F 14/08/2004 20:17:01
SKULL, MASTIODS 23

49. Magnifying glass

50. Invert image

51. Invert image
DIGITIZER, EMERGENCY 1O/07/2004 22:3O:28 DIGITIZER, EMERGENCY 1O/07/2004 22:3O:28

52. Annotation

53. Vertical flip
MR.RAVINDER 33YRS, M 19/08/2004 14:20:08
RIGHT LEG, AP&LAT 268
MR.RAVINDER 33YRS, M 19/08/2004 14:20:08
RIGHT LEG, AP&LAT 268

54. Multiple images on single film
MRS.SWAPNA 30YRS, F 29/06/2004 09:15:32

55. Multiple images on single film
MRS.FARIDA 30YRS ,F 12/8/2004 09:15:23
BARIUM MEAL FOLLOW THROUGH 286

56. CR vs DR
CR
• imaging plate
• Processing is done in a
Digital Reader
• Signal sent to computer
• Viewed on a monitor
DR
• transistor receiver (like
bucky)
• directly into digital
signal
• seen immediately on
monitor –