Radiology Equipmen

1. RADIOLOGICAL EQUIPMENT
Lecture3: Computed Radiography & Digital
Radiography
Dr. Emad Taleb

2. Digital X-ray Technology
There are two ways to obtain Digital X-rays:
• Computed Radiography
• Digital Radiography
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3. Computed Radiography (CR)
• A Digital way of doing general radiography with
Conventional X-ray machines
• 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
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4. 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
• Computed Radiography is a digital image acquisition
process that produces images that have much better contrast
than a Conventional X-ray (film-screen system)
• CR uses the existing X-ray equipment
• One CR system can support multiple x-ray rooms
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5. Basic Modules of CR
MA
TRIX
LR3300
Digitizer
Preview & ID Station
Processing Server
ID Tablet
Laser Camera
Cassette with
Imaging Plate
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6. Imaging Plate (IP)
• The Imaging Plate looks like the intensifying screens found
in Conventional film-screen cassettes
• They are made of photostimulable phosphor
• 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
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7. 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
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8. Storage Phosphor Principle
laser stimulation
Emission
Absorption
x-rays
electron
trap
electron
trap
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9. 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
• 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
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10. CR Readout
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11. 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
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12. 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.
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13. 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
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14. Erased Storage Phosphor Plate
• 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.
• 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.
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15. Workstation
• The digitized image
data is processed on a
processing server and
is displayed on its
monitor
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16. • 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.
• 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.
CR Workflow
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17. CR Workflow
Rx
Network
Digitizer
Printing
MA
TRIX
LR3300
Identification
Processing server
Exposure
Cassette with Imaging Plate
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18. • 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.
CR Workflow
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19. Digital Radiography
• This technique is performed by digital X-ray
machines with flat panel detectors.
• Digital Radiography uses two types of
detectors:
– Direct
– Indirect
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20. * TFT = THIN-FILM TRANSISTOR ARRAY
Digital Radiography…
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21. Indirect Detectors
• Uses a two step process that first converts X-rays into light, then
converts that light energy into electronic signals
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22. 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
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23. 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.
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24. 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.
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25. 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.
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26. • Radiography consists of following functions:
-Image data acquisition
-Image processing
-Reproduction of image
-Storage
Digital X-ray vs Conventional Radiography …
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27. • 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
Digital X-ray vs Conventional Radiography …
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28. Digital X-ray vs Conventional Radiography …
 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 Flat panel detectors
array in DR
• Processing server is used for image processing and
storage
• Workstation monitor is used for image reproduction
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