Use for radiographer's and interns

1. DIGITAL
RADIOGRAPHY

2. INTRODUCTION
Digital radiography (DR) is an advanced form of x-ray inspection which
produces a digital radiographic image instantly on a computer. This technique
uses x-ray sensitive plates to capture data during object examination, which is
immediately transferred to a computer without the use of an intermediate
cassette.

3. PRINCIPLE OF DR
• X-ray signal can be digitized by using detector.
• Firstly x-ray falls on detector which converts x-ray digital signal into
electronic signal.
• These electronic signal on TFT [Thin Film Transistor] or CCD[charge couple
device] where they are converted into digital signal.

4. Based on system geometry and radiation detector, radiography is divided into :-
• Computed radiography ( CR )
• Direct radiography ( DR )

5. COMPUTED
RADIOGRAPHY

6. • CR is also called PSP imaging.
• Photo- stimulable phosphor
plates replace the conventional
film - screen combination.
• Latent image formation Plate is
read out by scanning laser beam

7. THE PROCESS

9. • Cassette and image plate enter the reader
• Image plate is removed from cassette.
• Latent image is scanned by laser
• Image plate is erased with high intensity
light
• Image plate is returned to cassette and
ejected

10. ADVANTAGES OF CR
• Can be used with existing X- ray equipment.
• Multiple cassette sizes available
• Single CR system can convert multiple radiography to digital technology.
• Great positional flexibility
• Cost effective route to digital radiography
• Phosphor is reusable.
• Superior contrast resolution.

11. LIMITATIONS OF CR
• Technique is time and labor intensive like FSR
• Image reader takes time before the image can be displayed
• Lesser spatial resolution.
• Radiation dose required is same.

12. DETECTORS
• Detector capture Radiation beam from the patient.
• Detector that convert X-ray signal into Electronic Signal.
• TYPES OF DETECTOR.
• There are two types of Detector.
1) Indirect Digital Detector
2) Direct Digital Detector

13. INDIRECT DIGITAL DETECTOR
• It is consist of scintillation phosphor and Amorphous Silicon Photodiode.
• Scintillation crystal used = Thallium activated Cesium Iodide. [CSI]
• Terbium activated Gadolinium Oxy Sulphide
• SCINTILLATION.
• PHOTODIODE = made up Amorphous silicon [light sensitive material]

14. DIRECT DIGITAL DETECTOR
• Radiographic system which directly converts x-rays into digital signal in one
go.
• As Direct Digital Detector (Amorphous selenium –Photo-conducting
material)
• Basic aim is to convert transmitted x- rays into electrons which can be read
out by the detectors

15. WORKING (DIRECT AND INDIRECT
CONVERSION)

16. FOUR BASIC ELEMENTS
Capture element: Phosphors like CSI & GdOS, amorphous selenium
Coupling element: Lens, fiber-optic assembly
Collection element: amorphous silicon (Photodiode), CCD, amorphous selenium
(Photoconductor)
Read-out element (detectors): CCD, TFT (FPD).

17. DETECTORS – CCD &
FPD (TFT)

18. CHARGE COUPLED DEVICE (CCD)
• Light sensitive detector
• Consists of an integrated circuit
containing array of coupled
capacitors.
• Converts light into a electrical
charges.

19. FLAT PANEL DETECTOR(TFT)
• Complex system consisting of an array
of Thin Film Transistors (TFT).
• Consists of
• X-ray convertor
• TFT matrix
• Glass substrate.

20. SCANNED PROJECTION
RADIOGRAPHY(SPR)

21. • It is based on CT Technology and is possible after introduction of 3rd
generation of CT.
• This system is based on the well collimated narrow fan beam coressponds to
the detector array.
• SPR uses the CT Gantry and computer to produce an image that looks like
conventional Radiography

22. AREA BEAM(CONE BEAM) AND FAN BEAM

24. COMPONENTS OF SPR
• GANTRY – 1)X-RAY Tube
2) Detector (NaI/CsI)
3) Patient couch
• Display monitor

25. ADVANTAGES AND DISADVANTAGES OF SPR
ADVANTAGES
• High image contrast
• Wide dynamic range
• Post processing
DISADVANTAGES
• Long exposure time
• Poor spatial resolution
• More radiation dose

26. DIRECT DIGITAL
RADIOGRAPHY

28. DIRECT DIGITAL CONVERSION
• Selenium drum-based detector
• Selenium-based flat-panel detector
• Photon counting type DR

29. ATTRIBUTES OF DIRECT CONVERSION
• Detector : Amorphous selenium.
• Photoconductor converts x-ray photons into electrical charges by setting
electrons free.
• No spread of signal as the applied high voltage immediately attracts and
separates the electrons and holes produced by the absorbed x rays.
• High intrinsic spatial resolution.

30. SELENIUM DRUM-BASED DETECTOR
• Rotating selenium-dotted drum
• Has a Positive electrical surface
• Because of their mechanical
design, selenium drum detector
used in dedicated thorax stand
systems having no mobility.

31. SELENIUM-BASED FLAT-PANEL DETECTOR
• It can be mounted on
thorax stands and bucky
tables.
• Used for
mammography

32. PHOTON COUNTING TYPE DR
• Uses multislit detector made of
crystalline silicon.
• Absorbed x rays produce
electrons and holes.
• Currently used in mammography.

33. RECENT ADVANCES IN
DIGITAL IMAGING

34. Dual energy imaging
• By using high and low kV techniques , two data sets are created.
• Soft tissue and bones can be separately depicted by this method.
• Most effective when both images are acquired simultaneously.
• Useful in chest radiography , particularly in evaluation of partially calcified
nodules and pleural plaques.

35. Computer aided detection
• These are important in early detection of cancer of lung and breast.
• Soft ware detect suspicious lesions .
• Efficiency of soft ware depends on the sensitivity and specificity profile.
• Helpful as it permits a radiologists to avoid overlooking diagnostically
significant findings.

36. Mobile DR
• This is generally a 14 x 17 in flat panel detector connected by cable to a
mobile X- ray unit having a monitor.
• Fragile FPD and increased cost.

37. Wireless FPDs
• With introduction of model Pixium 3543 from Thales , wireless
portable DR is now a reality.
• This allows radiography of difficult regions of body like the axilla / TM
joint and radiography in unusually flexed parts of the body or limbs
with limited mobility due to contractures.

38. DIGITAL RADIOGRAPHY
Computed Radiography
• Direct Readout Digital Radiography
Memory storage
Display
monitor
Laser
printer
Reader (laser)
Photostimulable
phosphor
X-ray
photons
exiting pt.
Digital
data
Digital
data
X-ray
photons
exiting pt. Fixed imaging plate
Memory storage
Display
monitor
Laser printer

39. DEVELOPMENT IN DR
• 1980 : Digital subtraction angiography.
• 1980 : Computed radiography (CR), storage phosphors.
• 1987 : Amorphous selenium–based image plates.
• 1990 : Charge-coupled device (CCD) slot scan direct radiography (DR).
• 1994 : Selenium drum DR.

40. • 1995 : Amorphous silicon–cesium iodide(scintillator) flat-panel detector.
• 1995 : Selenium-based flat-panel detector.
• 1997 : Gadolinium-based (scintillator)
Flat-panel detector.
• 2001 : Gadolinium-based (scintillator)
Portable flat-panel detector.
• 2001 : Dynamic flat-panel detector fluoroscopy
Digital subtraction angiography.

41. ADVANTAGES OF DR
• IMMEDIATE READOUT
• CASSETTE FREE OPERATION
• GOOD FOR HIGH VOLUME RADIOGRAPHY
• CAN BE USED FOR MAMMOGRAPHY
• DETECTORS CAN BE RE-EXPOSED IMMEDIATELY

42. DISADVANTAGES OF DR
• MORE EXPENSIVE
• CAN NOT BE USED IN PORTABLE RADIOGRAPHY
• NOT COMPATIBLE WITH EXISTING TABLES