This document provides an overview of computed radiography (CR). It discusses the history and components of CR, including imaging plates, digitizers, and printers. The working mechanism is explained, from image acquisition using an imaging plate exposed to X-rays, to laser scanning to release photons detected by a photomultiplier tube and digitized to form the image. Advantages include comparable image quality to film and ability to process images digitally. The document also compares CR to conventional X-ray and digital radiography.

1. BY-PARBAT

2. COPUTED
RADIOGRAPHY

3. INTRODUCTION
➢ The term computed radiography (CR) refers to the process of
creating a diagnostic digital image from data acquired with an
imaging plate (IP) and reader.
➢ The CR process includes image acquisition, processing, and
display.
➢ Was the first digital technique available commercially.
➢ The most common technique for producing digital image. Primary
reason for being the most common technique is that it is cheapest.
➢ Commercial CR has been widely used in human medicine during
the past decade.
➢ Equine practitioners led the way, taking advantage of mobile and
portable systems with the ability to acquire and view diagnostic
radiographic images in the field.

4. CR UNIT
PORTABLE
MACHINE

5. H ISTORY
➢ Present day computed radiography (CR) is based on the use of
photostimulable phosphors, which are also known as storage phosphors
(Sonoda et al 1983).
➢ They are commercially the most successful detectors for digital
radiography.
➢ The phosphors used are most often in the barium fluorohalide family
(Barnes 1993) in powder form and deposited onto a substrate to form an
imaging plate or screen.
➢ In CR, an imaging plate (IP) containing the storage phosphor is positioned
in a light-tight enclosure, exposed to the x-ray image and then read out by
raster scanning with a laser to release the PSL.
➢ The blue PSL light is collected with a light guide and detected with a
photomultiplier tube (PMT).
➢ The PMT signal is digitized to form the image on a point-by-point basis
(Fujita et al 1989).

6. COMPONENTS
➢ For acquisition, processing, and displaying the digital
image CR system needs different components :
1. Normal x-ray unit
2. CR plate
3. Digitizer/ scanner
4. Printer-for hard copy output.
5. PMT and AD converter.

7. COMPONENTS OF COMPUTED
Psp plate
X-ray unit
Printer
Digitizer

8. Psp plate
➢ Refers to photo stimuable phosphor plate.
➢ Also known as CR plate.
➢ A CR plate is based on a fluorescent screen and
housed in a conventional ‘cassette’.
➢ Most CR systems use a Barium Fluoro-bromide
phosphor, This is then “doped” with Europium.
➢ The Europium changes the chemical structure
of the phosphor to “trap” electrons on x-ray exposure.
➢ During and after exposure, about 50% of the electrons remain trapped, the
rest fall back almost immediately
➢ Over time, due to thermal energy, trapped electrons fall back spontaneously
over many hours
➢ The time limitation for a x-ray image receptor keep without reading in
digitizer is about 8 hours.

9. WORKING MECHANISM
PMT
PSP PLATE
e-
AD
converter
computer
CR image

10. WORKING MECHANISM
PSL (photo stimuable luminance)
➢ When the PSP plate is irradiated the electron of the
phosphor material within PSP plate are excited which
are equally distributed on the PSP plate and get trapped
at higher energy level.
➢ If we introduce laser beam to the plate then such trapped
electron tends to fall back to their original state from
higher energy level, during this process the light Is
immited which is equivalent to band energy of trapped
electron.
➢ This phenomenon is called PSL .

11. WORKING MECHANISM
➢Such immited light is detected by PMTs(photo
multiplier tube) which converts the light photons
into electrons.
➢Those electron combine to form analog signal
which computer can’t detect.
➢So, these analog signals are converted to digital
signal by AD converter which next pass to the
computer for further processing.

12. WORKING MECHANISM
➢Then computer process the digital signal and
creates the digital image and displays in the
monitor.
➢Those image can be further processed
manipulated and can be transported to other
digital devices for clinical evaluation by using
PACS and DICOMS.
PACS-picture archiving communication system.
DICOM-digital imaging and communication
system.

13. WORKING MECHANISM
➢Again such image can be printed as a hard copy
if required.
➢Finally the PSP plate is exposed to white beam
of light which activates and erase the previous
data .
➢So that, this plate can be again used for the
next patient.

15. ADVANTAGE OF CR
➢ Image quality comparable with to conventional screen -film systems
➢ Wide dynamic range - ability to image structures of different attenuation
values (thorax and abd)
➢ Reduction of repeat exposures
➢ CR is compatible/upgrade with most conventional x -ray systems
➢ Increased savings: no film, chemicals, dark room and storage room required
➢ Computer processing of raw image: brightness, contrast, sharpness
enhancement, zooming, measurements …
➢ CR is more tolerant of under / over exposure (wide latitude )
➢ Ability to extract information not possible on conventional radiographs (e.g
edge enhancement, masking, cropping)
➢ Faster image acquisition
➢ DICOM -Digital imaging communications in medicine
➢ PACS - Images retrieved from computer archive
➢ Teleradiology:- the transmission of radiological patient images, from one
location to another for the purposes of sharing studies with other radiologists
and physicians.

16. COMPARISION BETWEEN COVENTIONAL X-RAY
AND CR
CONVENTIONAL X-RAY COMPUTED RADIOGRAPHY
➢ Older technology. ➢ Advanced technology
➢ Cheaper technology. ➢ Expensive technology.
➢ Post processing by using various
chemicals.
➢ Post processing by using signals.
➢ Intensifying screen is used. ➢ Intensifying screen is not used.
➢ Manipulation of image is not
possible once it is formed.
➢ Manipulation of image is possible
once it is formed.
➢ Trained manpower can also
function it.
➢ Skilled manpower is required.
➢ Film is used as IR. ➢ PSP plate is used as IR.
➢Formed image cant be erased. ➢Formed image can be erased and
reused for next patient.

17. DIGITAL

18. INTRODUCTION
➢ DR refers to Direct Digital Radiography .
➢ Digital radiography is a form of X-ray imaging, where digital X-ray
sensors are used instead of traditional photographic film.
➢ DR uses detector panel as image receptor.
➢ Advantages include time efficiency through bypassing chemical
processing and the ability to digitally transfer and enhance images.
➢ Also, less radiation can be used to produce an image of similar
contrast to conventional radiography.
➢ High image quality comparison to CR and conventional x-ray film.

19. Components of DR
➢The components of DR includes:
1. Detector
2. Charge coupling device(CCD)
3. Photo cell
4. PMT
5. AD converter

20. DETECTAR
➢There are two types of detectors:-
1. Gas filled detector.
2. Solid state detector.

21. Construction of gas filled detector
➢ Cylindrical in shape.
➢ Filled with gas ie.xenon gas in known amount and internally coated with
Graphite.
➢ Centrally an electrode is placed which connects the galvanometer and
cylindrical tube.
➢ It consists of battery with certain potential where negative terminal of battery
is connected to cylindrical shape and positive terminal of battery is
connected to electrode.

22. WORKING MECHANISM OF
GFD
➢When the x-ray interacts with gas within the
detector the x-ray ionize the gas through which it
travels.
➢As the electrode is positively charged , it attracts
the negatively charge and the electron flow
through the electrode.
➢This movement of electron causes the
movement of meter within ammeter which
indicates the radiation dose.

23. SOLID STATE DETECTAR
• CONSTRUC-TION
PMT
AD
CONVERT
ER
CC
P
Cesium
iodide
e- e- e- e- e-
e-
Digital
signal
Analog
signal
X-
rays

24. WORKING MECHANISM OF
SSD
➢ As soon as the x-ray interacts with phosphor material the
light get emitted
➢ The produced light photons are directed towards PMT.
➢ Coupling device is used to avoid the missing of light
photons.
➢ These light photons are converted into the electrons by
the multiplication by PMT , those electrons combine to
form analog signal.

25. WORKING MECHANISM OF
SSD
➢ These analog signals are converted to digital signal by AD converter
which next passed to computer for further processing to create DR
Image.
➢ The image can be further processed manipulated and can be
transferred to other digital device for clinical evaluation by using
PACS and DICOMS.
➢ Such image also can be printed as hard copy whenever required.

26. COMPARISION BETWEEN CR
AND DR
COMPUTED RADIOGRAPHY DIGITAL RADIOGRAPHY
➢Filmless technology. ➢Casstteless technology.
➢Works slower. ➢Works faster.
➢Lesser image quality. ➢Higher image quality.
➢High radiation dose ➢Less radiation dose
➢Lesser life span. ➢higher life span.
➢Simple to used. ➢Hectic mortality
➢Less costly. ➢Costly.
➢Less qualified personal can also
function
it.
➢Well qualified personal is required.