basics of radiography testing and image processing
TRANSCRIPT
-
7/29/2019 Basics of Radiography Testing and Image Processing
1/30
Basics of Radiography Testing
and Image Processing
B.Venkatraman*, Uwe Ewert**, M.Menaka* and
**
*Indira Gandhi Centre for Atomic Research India
** BAM Berlin German
Preconference Workshop 18 WCNDT, Durban, April 14, 2012
-
7/29/2019 Basics of Radiography Testing and Image Processing
2/30
Structure of the Talk
Basic Principle of Radiographic Testing
factors affecting radiographic image
ee or mage process ng Ima e arameters and terminolo ies
Image Processing Methods
Applications on radiographic images
-
7/29/2019 Basics of Radiography Testing and Image Processing
3/30
Rad iog raphyRad iog raphy
116 yrs old Technique is identical.Improvements in sources and detectors.
Object placed between
source and detector (film).
Differential absorption ofradiation. I = I e-x
The film darkness
the amount of radiation
reachin the film
X-ray film
= less ex osure
through the test object.
= more exposureTop view of developed film
-
7/29/2019 Basics of Radiography Testing and Image Processing
4/30
Sources Detectors
,
Microfocus
....
Image intensifiersImage intensifiers
Linac XX--ray sensitiveray sensitive vidiconsvidicons
Fluorescent screens +Fluorescent screens +
etatron Synchrotron
CCDCCD
Isotopic Sources
Ir192, Co60, Tm170, Digital Flat PanelsDigital Flat Panels
Yb169, Cs137, Se75 near o e rraynear o e rray
-
7/29/2019 Basics of Radiography Testing and Image Processing
5/30
PARAMETERS AFFECTING RADIOGRAPHIC IMAGING
MEASURED THROUGH SENSITIVITY
SUBJECT FILM CONTRAST* DEFINITION
ENERGY IMAGE QUALITY
INTENSITY SIGNAL TO NOISE RATIO
FOCAL SPOT SIZE BASIC SPATIAL RESOLUTION
DETECTOR CHARACTERISTICS
TRADITIONAL APPROACHES - COMPENSATION PRINCIPLES
-
7/29/2019 Basics of Radiography Testing and Image Processing
6/30
CONFIGUARATION OF IMAGE PROCESSING SYSTEM
X-RAYS TRANSMITTED THR. OBJECTS
FILMS REAL TIME SYSTEMS DIGITAL
DIGITISER(SCANNER, A/D
A/D CONVERTOR,(LUT)
DIGITALINTERFACE
CONVERTOR, LUT)
COMPUTER + GRAPHICS CARDS + MEMORIES + DISPLAY DEVICES
-
7/29/2019 Basics of Radiography Testing and Image Processing
7/30
DIGITAL IMAGE REPRESENTATION
Images - 2-D intensity function f(x,y), x and y : spatial coordinates and f:proportional to the intensity / brightness (gray level) of the image.
rows and columns and quantized levels.
DIGITAL IMAGE:
Image
(x,y) Digital
Image
n f(x,y)
columns and finite
gray levels
It is a matrix with M rows and N columns. Each matrix element has atypical gray level value ranging from 0-255 (8 bit).
( , )r x y
( , ) ( , )
( , )
f x y g x y
b x y
-
7/29/2019 Basics of Radiography Testing and Image Processing
8/30
IMAGE FORMATS AND TYPES
Converting the acquired image into computer acceptabledigitized from.
.
Stored formats
TIFF (Tagged Image File Format)
JPEG (Joint Photographic Expert Group)
XWD (X Windows Dump)PNG (Portable Network Graphics)
Image types
Intensity image (data matrix with intensities scaled to represent grayscale)
nary mage og ca array o s an s on y ac an w e
RGB image( three separate matrices (Red, Green and Blue)
-
7/29/2019 Basics of Radiography Testing and Image Processing
9/30
-
7/29/2019 Basics of Radiography Testing and Image Processing
10/30
-
7/29/2019 Basics of Radiography Testing and Image Processing
11/30
-
7/29/2019 Basics of Radiography Testing and Image Processing
12/30
IMAGE PROCESSING
Image processing refers to a set of
existing image f into new image g.
.
-
7/29/2019 Basics of Radiography Testing and Image Processing
13/30
-
7/29/2019 Basics of Radiography Testing and Image Processing
14/30
DIGITAL IMAGE PROCESSING
Processes whose inputs and outputs are images in which werender detail more clearly and extract attributes from images up
Image Compression (for effective Morphological Image Processingstorage & transmission) (image component extraction)
Color Image Processing
ProcessingImage Segmentation
Knowledge baseDescription
(Quantitative
Image Restoration
Recover ima e
opera ons n co or oma n
Image Enhancement (High-
light Region of Interest)
Object Recognition
(assign label to
Image Acquisition objects)
-
7/29/2019 Basics of Radiography Testing and Image Processing
15/30
Image Processing Operations typical in RT
Image Processing
Nei hbourhood
- Point Operations
-
/Matrix operations- Smoothing and
- Contrast
- LUT
arpness
- statistical filters
- Gamma value,
- Histogram
, ,
- directional filters- radient filter
- edge detection
-
7/29/2019 Basics of Radiography Testing and Image Processing
16/30
Point Operations
rocess n pa a oma n s eno e y e express onG (x,y) = T [ F(x,y) ]
F(x,y) is Input Image, G (x,y) is Processed Image
, .
Gray Level Transformation:
= r
The effect is to produce an image of higher contrast than the original by
.
This results in Contrast Stretching.s
mDark Light
Dark r
-
7/29/2019 Basics of Radiography Testing and Image Processing
17/30
Contrast and Brightness Enhancement
Raw Image
Raw Image After Brightness and Contrast Adjustment
-
7/29/2019 Basics of Radiography Testing and Image Processing
18/30
Histogram Equalisationk
Sk = T(rk) = k = 0,1, 2 ..L 1, rk is the kth gray levelnkis the number of pixels in the image having gray level rk
jj nn
0/
The idea of histogram equalization is that the pixels should be
distributed evenly over the whole intensity range, i.e. the aim is to
3x 10
5
transform the image so that the output image has a flathistogram.
1
1.5
2
2.5
0 50 100 150 200 250 3000
0.5
Original radiograph
2
2.5
3x 10
5
0 50 100 150 200 250 3000
0.5
1
1.5
Histogram enhanced
-
7/29/2019 Basics of Radiography Testing and Image Processing
19/30
Neighbourhood / Matrix Operations
Z1 Z2 Z3 Response R of a pixel is
Z4 Z5 Z6W4 W5 W6
R=
wizi i=1, 2, ., mn
Window is moved in such a way
Z7 Z8 Z9W7 W8 W9
that W5 is placed on the pixel of
interest.
Ima e divided into nei hborhoods.
(m=n=3) Filter or window
(m=n=3)
Sub images called filter or mask or kernel or template or window is appliedon the neighborhood of the images.
-
7/29/2019 Basics of Radiography Testing and Image Processing
20/30
-
7/29/2019 Basics of Radiography Testing and Image Processing
21/30
Smoothing
Original Image
P(i,j) = average [P(i,j), P(i-1,j-1), P(i+1,j+1),P(i+1,j-1), P(i-1,j+1)]
Smooth : Blurs the active
image or selection. This filterrep aces eac p xe w t t eaverage of its 33neighborhood.
Smoothened Image
-
7/29/2019 Basics of Radiography Testing and Image Processing
22/30
Averaging Filters
Averaging filters Replace the gray level of the candidate
cropped image
pixel by the average gray level of theneighborhood pixels.
Eliminate impulse noise andegra a ons appear ng as n s r pes.
Blur the image to get a grossrepresentation of objects of interest as
Fig. a Original Radiograph
the background while objects of interestare easy to detect.
Enhanced radiograph using average filter
1 1 1
1 1 11/9
1 2 1
2 4 21/16
1 1 1
Averaging Mask
1 2 1
Weighted AveragingMask
.
-
7/29/2019 Basics of Radiography Testing and Image Processing
23/30
Sharpening Filters - Spatial Domain
To highlight fine detail in an image or to enhance detail that hasbeen blurred either in error or during image acquisition
Fine details result in discontinuities in an image such as points,
edges and lines
Operator used must result in zero values at flat segments and.
First order derivative (Gradient operators)
Mathematical equation : f/ x=f(x+1,y)-f(x,y), f/ y=f(x,y+1)-f(x,y)
Filter masks : Roberts, Sobel and Prewitt
Mathematical e uation : 2f/ x2=f x+1 +f x-1 -2f x2f/ y2=f(x,y+1)+f(x,y-1)-2f(x,y)
Filter mask : Laplacian
-
7/29/2019 Basics of Radiography Testing and Image Processing
24/30
Filtering Noise Removal
-
-
7/29/2019 Basics of Radiography Testing and Image Processing
25/30
Edge EnhancementConvolve filter Variance filter Band Pass Filter Unsharp mask
High Pass Filter
D t il f th O ti P f d th
-
7/29/2019 Basics of Radiography Testing and Image Processing
26/30
Details of the Operations Performed on the
Ima es Media Filter: Reduces noise in the active image by replacing each pixel with the median of
the neighboring pixel values
.
Mean Filter: Smooths the current image by replacing each pixel with the neighborhoodmean.
Minimum Filter: Filter does ra scale erosion b re lacin each ixel in the ima e with thesmallest pixel value in that pixels neighborhood.
Maximum Fitler: Filter does grayscale dilation by replacing each pixel in the image with thelar est ixel value in that ixels nei hborhood.
Gaussian Blur: Filter uses convolution with a Gaussian function for smoothing
onvo ve: oes spa a convo u on us ng a erne en ere
Unsharp Mask: Sharpens and enhances edges by subtracting a blurred version of the
image (the unsharp mask) from the original.
Variance Filter: Highlights edges in the image by replacing each pixel with theneighborhood variance.
Bandpass Filter: Removes high spatial frequencies (blurring the image) and low spatial
frequencies (similar to subtracting a blurred image). It can also suppress horizontal orvertical stripes that were created by scanning an image line by line.
C St dC St d 11
-
7/29/2019 Basics of Radiography Testing and Image Processing
27/30
Case StudyCase Study --11
InIn--service Ins ectionservice Ins ection Power Plant Life ExtensionPower Plant Life Extension
Sodium blockage in a hot argon communication
line of Fast Breeder Test Reactor at Kalpakkam.
Reactor shut down. Detection became critical.
Low densit material. Gamma source Ir 192.
Challenge Limited access, large area, low Z
. .
Approach - Advanced Image processing :
, ,
Sharpening - Edge Enhancement
-
7/29/2019 Basics of Radiography Testing and Image Processing
28/30
Case Study 2 Enhancement of Tenon Rivet Head-
Pow er Station in I ndia shutdown (as part of bi-annual maintenance and Turbine Generator w asopened for in-service inspect ion. During in- servicevisual inspect ion, the thickness of r ivet head of
t enon of blade 17 of HP rot or st age-2 w as found t obe less than other blade t enons and almost flushw it h shroud. Regulators w anted proof.
Low Cont rast radiograph by Gamm a Radiography
Approach Denoising+ Deblurring +
bandpass filter +contrast enhancement
Filtered and contrast enhanced image. Note that theedges of the rivet head can be seen as sharp points overthe shroud portion.
Contrast &Flow chart
-
7/29/2019 Basics of Radiography Testing and Image Processing
29/30
Contrast &
brightnessHistogram
Flow chartdevelopedfor Image
Equilisationprocessing
Edge Enhancement through Spatial filtering
Case Study 3 : Qualit y Assurance of
ASTM Standard + Image Enhancement =used in nuclear reactors
n ance n erpre a on an uan a veEvaluation forweld quality, sheath spacing, uniformity of
Materials Evaluation, May 2007
COMBINING ADVANCED CONCEPTS WITH
STANDARD PRACTICES FOR ROBUSTQUALITY ASSURANCE
-
7/29/2019 Basics of Radiography Testing and Image Processing
30/30