CR Presentation.ppt - Computed Radiography

Computed Radiography

1. COMPUTED RADIOGRAPHY SYSTEM

2. What is Computed Radiography
It’s a Digital Radiographic Imaging process
with three major steps
I.Capture latent images on a special
imaging plates with the help of Gamma
rays / X rays
II. Digitize the latent image with help of a
laser scanner
III.Digital image enhancement for better
viewing

3. CR- Image Capture:
•Computed Radiography employs Imaging plates
(Phosphor pates) , which when irradiated, stores
a latent radiographic image for an unspecified
period of time.
•This is much the same fashion as classical X-Ray
film.

4. CR Image Capture

5. CR Cassette
PSP

6. CR Phosphor Screen Structure
X-rays/Gamma rays penetrating the specimen
stimulate the phosphors. The stimulated phosphors
remain in an excited state.
X-Rays
Phosphor Layer
Protective Layer
SubstratePhosphor Grains
During exposure:

7. CR Image Extraction

8. Motor
A/D
Converter
Imaging
Plate
Optical
Scanner
Photo-multiplier Tube
110010010010110
Laser Beam
As a laser scans the imaging plate, light (Photo stimulable
Luminescence) is emitted where X- rays stimulated the
phosphor during exposure.
The light is then converted to a digital value.
CR Image Extraction

9. CR Digital Image Enhancement
Digital images are typically sent to a computer
workstation where specialized software allows
manipulation and enhancement.

10. Enhancing Tools
•Window / level
•Zooming
•Kernels
•Rotation
•Inversion
CR Digital Image Enhancement

11. Measurement Tools
•Line Profile
•Line Length
•Point Profile
CR Digital Image Enhancement

12. Window / Levelling
• Window and leveling is designed to manage the mapping of
a large number of greyscale levels (GSL) acquired which in
turn permits the human eye to work within its narrow
grey scale sensitivity range.
• For example, digitized images can have up to 4096 GSLs
per pixel and with monitors displaying up to 256 (8 bits)
GSLs.
• The human eye can only perceive about 128 (7 bits) of GSL.
• Window corresponds to range of greyscale levels.
• Level represents mid point of the displayed range.
CR Digital Image Enhancement

13. 1 bit - 2 levels of gray1 bit - 2 levels of gray
Bit depth (gray levels)Bit depth (gray levels)

14. 2 bit – 4 levels of gray2 bit – 4 levels of gray

15. 4 bit - 16 levels of gray4 bit - 16 levels of gray

16. 6 bit - 64 levels of gray6 bit - 64 levels of gray

17. Range of Range of
InterestInterest
4096 digital intensity values in the workstation4096 digital intensity values in the workstation
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18. Window / Levelling

19. Benefits of window / levelling
• Wide dynamic latitude
•less retakes
•less film usage
•less time
•one exposure approach

20. Zoom
•When radiographic images are initially scanned
and displayed, they are viewed at 1:1 unless
predetermined to another size.
•The zoom or magnify factor can be changed
from 0.1x to 40x and can be applied as an R.O.I.
or overall application.
Benefits of Zoom
•Renders previously difficult to view data readily
detected.

21. Zoom 2.0x
Zoom 1.0x
Zoom 0.5x

22. Kernels
•Kernels allow for enhanced filtering of the image by
means of a convolution between kernel and the image.
•The filters have two functions, sharpening & smoothing,
and are used for attenuating unwanted frequencies in
digital signals.
•Sharpening performs a high-pass filter operation that
lessens the low spatial frequencies, e.g. sharpens edges
but may make image grainy.
•Smoothing performs a low-pass filter operation that
lessens the high spatial frequencies, e.g. blurs any image
graininess.

23. standard
emboss
smooth
sharp

24. Rotation / Mirror / Flip
•Images can be rotated in increments of 90º
(0, 90, 180 &270).
•Additionally they can be mirrored or flipped
therefore allowing viewing in any orientation

25. Inversion
•The image greyscales can be inverted for
enhanced viewing.
normal
inverted

26. Line Profile
•Allows the user to draw a line on the image and
a graph will be displayed plotting digital pixel
value vs. data point.
Point Profile
•The user can invoke the point profile form
which will display a 3 x 3 pixel matrix of digital
pixel values.
•Similar to traditional density measurement.

27. Line Length
•The user can draw a line on the image and
the length will be calculated and displayed.

28. Other Tools
•Region of Interest (ROI)
•Annotation – predefined or typed text
•Arrows & Lines
•Musica:Contrast Amplification
•Edge Contrast
•Latitude Reduction
•Noise Reduction
•Technique Sheets

29. Preserve the Original Data
•Rad View offers many image processing functions
to enhance the radiographic images. However, it is
important that a digital system archives all image
files in their original state to preserve the integrity of
the raw data.
•All enhancements or layer management never alter
the original image.
Rad View Software

30. Export Modes
•Images can easily be exported in many standard
graphic file formats.
 This way, remote users can
receive information and view inspection results
with any standard viewing software.
Rad View Software

31. Benefits of Computed RT
•Less retakes because of a wide dynamic latitude
•Dose reduction due to shorter exposures
•Reduced time in result processing
•Longevity, reusable up to 20,000 times
•Image Enhancement permits easier viewing
•High Image Sharpness
•Image Exportation
•Annotations
•Environment

32. General Questions?
•Does RadView require special exposure
parameters?
Yes, use approximately one tenth of a D7
exposure i.e.100kV 10mAm → 100kV 1mAm
•Can RadView imaging plates be used anywhere?
Yes, PSP or CR Phosphor plates can bend to suit
a 3” pipe.

33. •How does resolution compare with that of existing
film systems?
CR is comparable with Agfa D4 and D7 depending
on material and PSP plate used.
•However, this is dependant on the human eye and
monitor pixel size i.e. human eye has a best
resolution of approx 75µm, film resolution is approx
2µm and digital radiography is approx. 50µm.

34. original
enhanced
The main point to
remember is that you can
zoom a digital image.
That allows you to see more!

35. Limitations
•Shooting limitations of RT