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