1. Digital Radiography
Understanding Digital
Radiography Principles
Dr. Hussein Ahmed Hassan
Original
Inverted
Embossed

2. Purpose: Basic Answers
What is digital radiography?
What components are required?
What types of digital radiography work best in
practice?
 How do we choose the right solution for our
program?
 What are the computer and networking
requirements to support our digital solution?
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3. What is Digital Radiography?
 Sensors or phosphor plates
take the place of traditional
film.
 Radiographic images are
acquired almost instantly
and stored electronically.
 They can be manipulated,
viewed, and transferred with
a software program.

4. What Components are required for
Digital Radiography?
 Sensors or phosphor plates to replace x-ray film.
 Imaging software that allows image storage and
management.
 Computer system to run imaging software.
 Optional: Practice management software –for
completely paperless patient records
management.

5. Digital Radiography
 Is a form of x-ray imaging, where digital
X-ray sensors are used instead of traditional
photographic film.
 Advantages include;
1. Time efficiency through bypassing chemical
processing
2.The ability to digitally transfer and enhance
images.
3.Less radiation can be used to produce an
image of similar contrast to conventional

6. Digital Imaging Technology
Digital methods for processing and displaying x-ray images
were first introduced with the advent of computed tomography
(CT) in 1972.
Continuing advances in computer technology have promoted the
general development of image acquisition in digital form (CCD
cameras), most commonly from image intensifiers (digital
fluoroscopy) or from storage phosphor plates (computed
radiography).
Other detector systems such as ‘flat-panel’ technology for indirect
or direct digital radiography are now available for general purpose
equipment.

7. Capture technologies used today:
• Screen/film
(S/F) combination system
• Image intensifiers
• Computed radiography (CR) with storage phosphors
• Direct Digital radiography (DDR)

8. Image Acquisition
Conventional X-ray
Drying
X-ray
fixer
water developer water

9. Image Acquisition in Digital Imaging
 There are a number of technologies used
for digital imaging in planar radiography
these are;
1. Computed radiography (CR), CR in first
appearance, similar to the used of
film/screen system. The CR plate is in a
cassette, which will fit the table and vertical
Backy trays and can be used with mobile
equipment. The plate is then scanned in a
reading system, this make the change to
computed radiography (CR) easier.

10. Image Acquisition
CR
X-ray Tube
Latent image
Photomultiplier
Readout
Erasure
ADC
IP Ready
Fluorescent Lamp
Workstation

11. 2.Direct Digital
 Means, instead of using x-ray film, a
sensor connects directly to your
computer - the x-ray image displays
almost immediately after taking it.
 Sensors use either a Charge
Coupled Device (CCD), or a
Complementary Metal Oxide
Semiconductor (CMOS) or thin-film
transistor (TFT) to convert light into
electrons. These are collected &
turned into pixels that show
brightness and contrast - that’s what
makes a digital x-ray image.
 You still use your regular x-ray
machine to take the exposure.
 Both CCD sensors, CMOS sensors
and TFTwork extremely well.

12. Direct Digital Radiography --cot---Direct Digital Radiography (DDR), DDR
system needs more changes in x-ray couch
and vertical backy design and often
changes to x-ray tube assembly, DR
detector is fully integrated into exposure
equipment. The patient is radiographed and
the image appears on workstation in few
seconds. Here image optimized and then
sent for reporting or repeated if necessary.

13. Image Acquisition DR
1.X-ray scintillator bonded to readout ray, thin-film transistor (TFT)
X-ray Tube
Workstation
Detectors (TFT)

14. Why do we need a new technology, what is wrong with
film/screen?
• Absolutely nothing !!!!
• Still the “gold standard” to which all new projection radiography
systems are measured against
• On many accounts (e.g.: mammography) , S/F is still superior than
some new technologies (e.g.: CR)
• The choice of technology depends on clinical, technical, operational
and economic factors

15. Uses Digital Radiography
 CR is used in all areas where film/screen
systems are currently used, including
mammography.
 Direct Digital Radiography (DDR) can be
used in general radiography and mobile
radiography.
 DDR is very popular in small-field
mammography and being introduced into
full-field mammography.
 DDR detectors are now being used instead
of image intensifiers in fluoroscopy.

16. Computed Radiography
What is it?
 Computed Radiography, commonly known as CR, is a
digital radiography process that is designed to replace
industrial radiographic film
 The CR process is very similar to the process associated
with film … mainly because of the film-like digital detector
that is used to capture the radiographic image
 The CR film-like digital detector is a flexible phosphor
screen that looks and feels a lot like film

17. CR Cassettes
Storage phosphor (SP) screens are similar in structure to
conventional intensifying screens

18. Computed Radiography
Storage Phosphor
Digital X-ray Imaging Systems

19. Computed Radiography
How does it work?
Step 1: The phosphor screen is inserted into a
soft or hard cassette (with or without lead)
Step 2: A radiation pattern is exposed on the phosphor screen
creating a latent image
Step 3: The phosphor screen is then inserted
into a phosphor scanner to be read
Step 4: The phosphor screen is scanned and the digital
image is displayed on the workstation
monitor for review and evaluation
Step 5: The phosphor screen is then erased and ready to
be reused

20. Computed Radiography System Process
Differences between Phosphor & Film
Step 1: The phosphor screen is inserted into a soft or hard
cassette (with or without lead screens)
Do not need a light-tight darkroom for phosphor imaging
Step 2: A radiation pattern is exposed on the phosphor screen
creating a latent image
Phosphor is faster and much more forgiving (wide latitude)
Step 3: The phosphor screen is then inserted into a phosphor
scanner to be read No chemical.
Film processor (8 minutes) vs. Phosphor (1 to 2 minutes)
Step 4: The phosphor screen is scanned and the digital image is
displayed on the workstation monitor for review
Digital image can be enhanced increasing OD
Step 5: The phosphor screen is then erased and ready to be reused
The phosphor screens are reusable

21. Computed Radiography System Process
Similarities between Phosphor & Film
Step 1: The phosphor screen is inserted into a soft or hard
cassette (with or without lead screens)
Just like film
Step 2: A radiation pattern is exposed on the phosphor screen
creating a latent image
Shot set-up and technique are basically the same
Step 3: The phosphor screen is then inserted into a phosphor
scanner to be read
Very similar to film being put into a film processor
Step 4: The phosphor screen is scanned and the digital image
is displayed on the workstation monitor for review
Film is put on a lightbox to view
Step 5: The phosphor screen is then erased and ready to be
reused

22. Computed Radiography System
Components Overview

23. Computed Radiography System
consists of the following components:
WORKSTATION
& SOFTWARE
PHOSPHOR
SCANNER
& ERASER
PHOSPHOR
SCREENS

24. Computed Radiography System
Workstation and Software

25. Computed Radiography System
Workstation and Software
 Operates the Phosphor Scanner
 Manages your images and
associated data: drawings, word
documents, digital photos, procedures,
reference images, techniques, etc.
 Image enhancement capabilities:
zoom, gray-scale manipulation, pan & scroll,
density & measurements tools (histograms, point profiles, line
profiles, line and area measurements), image processing,
annotation, etc.
 Ability to save and archive your digital images and
associated data

26. Computed Radiography System
Phosphor Scanners
Two different types of Phosphor Scanners

27. Computed Radiography Systems
Table-top
CR100
CR Tower

28. Computed Radiography System
(Table-top Unit)
consists of the following components:
WORKSTATION
& SOFTWARE
PHOSPHOR
SCANNER
Phosphor Screen is placed
directly into the scanner
PHOSPHOR
SCREENS

29. Computed Radiography System
(CR Tower Free-Standing Unit)
consists of the following components:
WORKSTATION
& SOFTWARE
PHOSPHOR
SCANNER
Hard-cassette
based system
PHOSPHOR
SCREENS

30. Phosphor Scanners
How is the phosphor
screen scanned?
He-Ne laser
rotating mirror
light-guide
PMT
storage phosphor plate

31. Overall mechanism

32. Computed Radiography System
Phosphor Imaging Screens
and customized Cassettes

33. Computed Radiography
Phosphor Screens
Manufactured in similar sizes as film
Utilizes the same cassettes as film
Utilizes the same x-ray sources as film
Set-up in the field is the same as film
Typically faster exposures than film
Very wide latitude which makes it much
more forgiving than film / less reshots
 No chemicals required for processing
 Image quality good match for aircraft
applications
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34. PSP- PhotoStimulated Phosphor
 Reusable plastic plate  Laser scanning - the
coated with phosphor
trapped electrons are
released  It stores the energy of
photostimulated
the remnant x-ray - xluminescence
ray photons excites the
 The emitted light is
electrons in the
phosphor.
detected by
photomultiplier tube,
and is digitized to form
an image

35. Computed Radiography
How is the phosphor screen
manufactured (very similar to film)?
phosphor
layer
phosphor
grains
protective
layer
substrate

36. Computed Radiography Technology
The active phosphor layer of a CR plate usually comprises a
layer of europium-doped barium fluorobromide, which is coated
on to a semi-rigid or flexible polyester base.
phosphor
layer
phosphor
grains
protective
layer
substrate
X-ray photons are absorbed by the phosphor layer, the phosphor
electron become excited and raised to high energy level, where they
can stay trapped in semi-stable high energy state.
The trapped electron represent a latent image in the phosphor plate in
form of stored energy.
The stored energy is released by adding energy to the trapped electron
This done by stimulation with laser beam, the trap electrons then escap
from the traps to fall back to their equilibrium state.

37. Computed Radiography Technology---cot----
As the electrons fall back, the electrons release energy in
form of light.
This phenomenon is known as photostimulable
luminescence (PSL).
The emitted light intensity is proportional to original x-ray
intensity.
The light energy detected and signal is digitized and
processed digitally to produce a visible diagnostic radiograph
 on a monitor.
The phosphor plate is then erased with a bright white light t
remove any remaining trapped electrons, and the plate is
then ready for the next examination.

38. Directed Digital Radiography
(DDR)
Directed digital radiography, a
term used to describe total
electronic imaging capturing.
Eliminates the need for an
image plate altogether.

39. Amorphous Selenium detector technology for
DR Direct Radiography

41. IMAGE CAPTURE
CR
– PSP – photostimulable phosphor plate
– REPLACES FILM IN THE CASSETTE
DR – NO CASSETTE – PHOTONS
– CAPTURED DIRECTLY
– ONTO A TRANSISTOR
– SENT DIRECTLY TO A MONITOR

42. Densities of the IMAGE
 The light is proportional to
amount of light received
 digital values are then equivalent
(not exactly the same) to a value
of optical density (OD) from a
film, at that location of the image

44. CR VS DR
– CR -Indirect capture where the image
is first captured on plate and stored =
then converted to digital signal
– DDR -Direct capture where the image is
acquired immediately as a matrix of
pixels – sent to a monitor

45. DIRECT RADIOGRAPHY
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uses a transistor receiver (like bucky)
that captures and converts x-ray energy
directly into digital signal
seen immediately on monitor
then sent to PACS/ printer/ other
workstations FOR VIEWING

46. CR vs DR
CR
 imaging plate
 processed in a Digital
Reader
DR
 transistor receiver (like
bucky)
 directly into digital
signal
 Signal sent to computer
 Viewed on a monitor
 seen immediately on
monitor –

47. ADVANTAGE OF CR/DR
 Can optimize image quality
 by manipulating digital data
 to improve visualization of anatomy
and pathology
 AFTER EXPOSURE TO PATIENT

48. ADVANTAGE OF CR/DR
 CHANGES MADE TO IMAGE
 AFTER THE EXPOSURE
 CAN ELIMINATE THE NEED TO
REPEAT THE EXPOSURE

49. ADVANTAGE OF CR/DR vs FS
Rapid storage
retrieval of images NO LOST FILMS!
PAC (storage management)
Teleradiology - long distance transmission
of image information
 Economic advantage - at least in the long
run?
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50. CR/DR VS FILM/SCREEN
 FILM these can not be modified
once processed
 If copied – lose quality
 DR/CR – print from file – no loss
of quality

51. “no fault” TECHNIQUES
F/S: RT must choose technical factors
(mAs & kvp) to optimally visualize anatomic detail
CR: the selection of processing algorithms and
anatomical regions controls how the acquired
latent image is presented for display
 HOW THE IMAGE LOOKS CAN BE ALTERED BY
THE COMPUTER – EVEN WHEN “BAD”
TECHNIQUES ARE SET

52. DR
Initial expense high
very low dose to pt –
image quality of 100s using a 400s
technique
 Therfore ¼ the dose needed to make the
image
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53. Storage /Archiving
FILM/SCREEN
 films: bulky
 deteriorates over time
 requires large storage
& expense
 environmental
concerns
 CR & DR
 8000 images stored
on CD-R
 Jukebox CD storage
 no deterioration of
images
 easy access

54. Computed Radiography System
Compatibility & Growth Opportunities
Most of the CR Workstations also have the ability to
operate a wide variety of:
- printers
- document scanners
- archiving hardware
- film digitizers
- flat panel arrays
- and other digital
detectors

55. Transmission of Images
 PACS - Picture Archiving &
Communications
System
 DICOM - Digital Images & Communication
in Medicine
 TELERADIOGRAPHY -Remote
Transmission of Images

57. Digital imaging technology (cont)
The technique of digital subtraction
angiography (DSA), based on digital
image processing, allows enhanced
visualization of blood vessels by
electronically subtracting unwanted
parts of the image.

58. Digital subtraction angiography.
(a) Mask ,immediately prior to contrast injection a preliminary digitized image
known as the “mask” is performed. Note pelvic bone, bowel gas and arterial catheter.
(b) Contrast image. Contrast is injected through the catheter producing opacification
of arteries.
(c) Subtracted image. The computer subtract the mask from the contrast image leaving
an image of contrast fill blood vessels unobscured by overlying bone and bowel.
Note a tight localized stenosis of the right common illiac artery (arrow)

59. Digital imaging technology
At this time, there is no consensus on the best
technology for balancing dose and image quality. Digital
imaging potentially can provide lower doses than the
film-intensifying screen method.
However, through post-exposure manipulation of the data,
satisfactory diagnostic images can be produced even
when unnecessarily high patient radiation doses are
used. Proper quality assurance procedures are
essential.

60. Main Characteristics of an Image Receptor
The selection of an imaging system should
involve a thorough evaluation and analysis of its
complete characteristics together with
consideration of the technical and human
environment in which the system will be used.
The main characteristics to be considered when selecting
an image receptor are:spatial resolution; contrast resolution; dose efficiency;
Modulation Transfer Function; detector size;
possibilities of image storage and transfer; and
qualities such as weight, robustness, fast image
access, etc).

61. CR - ? Which shows
“better detail” Why/how?
8 x 10 cassette
14 x 17 cassette

62. To Produce Quality Images
For Conventional Projection
or CR Radiography:
The same rules, theories, and laws still
apply and can not be overlooked
FFD/OFD (SID/SOD)
Inverse Square Law
Beam Alignment Tube-Part-Film Alignment
Collimation
Grids
Exposure Factors: KVP, MaS
Patient Positioning

63. 90 KVP
GE DR

64. BURNING

65. 0˚ Angle
30˚ Angle
50˚ Angle

66.  towel that was used
to help in
positioning a child
 CR is MORE
sensitive to
 ARTIFACTS
NEW IMAGE

67. CR image – NEW IMAGE
 Line caused
from dirt
collected in a
CR Reader

68. Double
exposure
Child

69. 120 KVP
Fuji CR

70. ?
Hands over upper
abdomen

71. High resolution with digital
imaging

72. Vertical patterns of hyperintense signal

usually represent foreign materials
that are stuck to the light path
assembly that acquires the
photostimulated luminescence
signal from the CR imaging plate as
it is being scanned by a laser beam.
As the light is blocked at the same
spot as the plate translated through
the optical stage, the artifact occurs
perpendicular to the laser beam
readout, in the plate translation
(slow-scan) direction. The stripe
appears bright, since the image
undergoes a reverse grayscale
transformation to make the image
appear similar to a screen-film
image with processing.

73. A lateral chest image with an unusual
superimposed pattern on the anatomy.
 This is an example of a CR
image obtained with
cassette reversed, where
the tube side of cassette is
pointed away from the x-ray
tube source and toward the
patient. Cassette plastic
structural patterns are
projected onto the imaging
plate (particularly
noticeable in the arms and
anterior part of the patient.

74. ‫المأذن حرابنا والقباب خوزاتنا مساجدنا ثكناتنا والمصلون جنودنا وهذا الجيش المقدس يحمي ديننا‬
‫محمد عاكف شاعر تركى‬

75. THANK YOU!!
Question?