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E. Fatemizadeh, Sharif University of Technology, 20111
Medical Image Analysis and Processing
Introduction to Image Processing
1
• Our General Definition of image:– A physical property(ies) of an object.
• Not necessarily visible.
• Main Physical Property:– Electromagnetic Radiation:
• From Radio Waves to Cosmic rays
• A categorization:– Single Channel– Multi Channels
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E. Fatemizadeh, Sharif University of Technology, 20112
Medical Image Analysis and Processing
Introduction to Image Processing
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The Electromagnetic SpectrumThe Electromagnetic Spectrum
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E. Fatemizadeh, Sharif University of Technology, 20113
Medical Image Analysis and Processing
Introduction to Image Processing
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• Digital Image, Mathematical Definition:– I = f(x,y)– I: intensity (or color)– (x,y): Position or Coordination– When (x,y) and I are finite and discrete quantities -→ digital image
– pixels, picture elements, image elements
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E. Fatemizadeh, Sharif University of Technology, 20114
Medical Image Analysis and Processing
Introduction to Image Processing
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• Image Representation:
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E. Fatemizadeh, Sharif University of Technology, 20115
Medical Image Analysis and Processing
Introduction to Image Processing
5
Bone ScanPET
Cygnus Loop Gamma Radiation from reactor valve
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E. Fatemizadeh, Sharif University of Technology, 20116
Medical Image Analysis and Processing
Introduction to Image Processing
6
Chest X-Ray
Angiography
CT
Circuit Board
Cygnus Loop
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E. Fatemizadeh, Sharif University of Technology, 20117
Medical Image Analysis and Processing
Introduction to Image Processing
7
UV imaging
Normal Corn Smut Corn
Cygnus Loop
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E. Fatemizadeh, Sharif University of Technology, 20118
Medical Image Analysis and Processing
Introduction to Image Processing
8
Taxon (Anti cancer)
CholesterolMicroprocessor
Nickel Oxide Thin Film
CD SurfaceSuperconductor
Light Microscopy
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E. Fatemizadeh, Sharif University of Technology, 20119
Medical Image Analysis and Processing
Introduction to Image Processing
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• CT
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E. Fatemizadeh, Sharif University of Technology, 201110
Medical Image Analysis and Processing
Introduction to Image Processing
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• MRI
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E. Fatemizadeh, Sharif University of Technology, 201111
Medical Image Analysis and Processing
Introduction to Image Processing
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• MRI
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E. Fatemizadeh, Sharif University of Technology, 201112
Medical Image Analysis and Processing
Introduction to Image Processing
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• US
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E. Fatemizadeh, Sharif University of Technology, 201113
Medical Image Analysis and Processing
Introduction to Image Processing
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• US
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E. Fatemizadeh, Sharif University of Technology, 201114
Medical Image Analysis and Processing
Introduction to Image Processing
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• SPECT
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E. Fatemizadeh, Sharif University of Technology, 201115
Medical Image Analysis and Processing
Introduction to Image Processing
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• PET
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E. Fatemizadeh, Sharif University of Technology, 201116
Medical Image Analysis and Processing
Introduction to Image Processing
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• PET
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E. Fatemizadeh, Sharif University of Technology, 201117
Medical Image Analysis and Processing
Introduction to Image Processing
17
• PET-CT
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E. Fatemizadeh, Sharif University of Technology, 201118
Medical Image Analysis and Processing
Introduction to Image Processing
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• MRA
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E. Fatemizadeh, Sharif University of Technology, 201119
Medical Image Analysis and Processing
Introduction to Image Processing
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• A Sample of Multi Channels imaging:– Satellite imaging
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E. Fatemizadeh, Sharif University of Technology, 201120
Medical Image Analysis and Processing
Introduction to Image Processing
20
• MRI as a Multi Channels imaging modalities:
PD T1 T2
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E. Fatemizadeh, Sharif University of Technology, 201121
Medical Image Analysis and Processing
Introduction to Image Processing
21
• MRI as a Multi Channels imaging modalities:
PD weightedPD weighted T2 weightedT2 weighted
ee.sharif.edu/~maip
E. Fatemizadeh, Sharif University of Technology, 201122
Medical Image Analysis and Processing
Introduction to Image Processing
22
• DIP applications:– Image Quality Enrichment – Data Redundancy Reduction– Automatic Detection– Machine Vision– Machine Recognition/Verification
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E. Fatemizadeh, Sharif University of Technology, 201123
Medical Image Analysis and Processing
Introduction to Image Processing
23
• DIP applications:– Image Enhancement, Denoising, Reconstruction.– Authentication (Biometrics):
• Face, Signature, Fingerprint, Palm, Gesture, Retina Iris.
– Robotic Production Line (Vision)– OCR (Optical Character Recognition)– Automatic Diagnosis (Medical, Industry, and etc.)– Image Compression (jpg, tiff, jp2, and etc.)
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E. Fatemizadeh, Sharif University of Technology, 201124
Medical Image Analysis and Processing
Introduction to Image Processing
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Medical Ultrasound imaging
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E. Fatemizadeh, Sharif University of Technology, 201125
Medical Image Analysis and Processing
Introduction to Image Processing
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• An Example of Image Processing Results
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E. Fatemizadeh, Sharif University of Technology, 201126
Medical Image Analysis and Processing
Introduction to Image Processing
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• Image Sampling– How to determine the sampling rate?– Nyquist sampling theorem
• If input is a band-limited signal with maximum frequency ΩN
• The input can be uniquely determined if sampling rate ΩS > 2ΩN
– Nyquist frequency : ΩN
– Nyquist rate : ΩS
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E. Fatemizadeh, Sharif University of Technology, 201127
Medical Image Analysis and Processing
Introduction to Image Processing
27
• Image Quantization– L- level digital image of size MxN– Means: A digital image having:
• A spatial resolution MxN pixels• A gray-level resolution of L levels (0-L-1)
– Spatial resolution in real-world space
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E. Fatemizadeh, Sharif University of Technology, 201128
Medical Image Analysis and Processing
Introduction to Image Processing
28
• Image in Matrix Form:
f(0,0) f(0,1) … f(0,N-1)f(1,0) f(0,1) … f(1,N-1)
……
f(M-1,0) f(M-1,1) … f(M-1,N-1)MxN
bits to store the image = M x N x kgray level = L = 2k
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E. Fatemizadeh, Sharif University of Technology, 201129
Medical Image Analysis and Processing
Introduction to Image Processing
29
• L = 2k gray levels, gray scales [0,…,L-1]• The dynamic range of an image
– [min(image) max(image)]– If the dynamic range of an image spans a
significant portion of the gray scale → highcontrast
– Otherwise, low dynamic range results in a washed out gray look
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E. Fatemizadeh, Sharif University of Technology, 201130
Medical Image Analysis and Processing
Introduction to Image Processing
30
• Gray Levels in CT:– Gray levels in CT image represent attenuation
coefficient in each pixel.– Gray levels expressed in Hounsfield units (HU)
• Water: 0 HU • Air: -1000 HU • Bone: 400 - 3000 HU
– Maximum CT number is 2000-4000
Water
Water air
μ-μCT= ×1000 HUμ -μ
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E. Fatemizadeh, Sharif University of Technology, 201131
Medical Image Analysis and Processing
Introduction to Image Processing
31
• CT images displayed with suitable brightness and contrast.• Two important value:Window Level (WL) and Window Width
(WW) • WL is CT number of mid-grey • WW is number of HU from black to white
• Choice of WW and WL dictated by clinical need– -1000 HU– 0 HU– 4000+ HU
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E. Fatemizadeh, Sharif University of Technology, 201132
Medical Image Analysis and Processing
Introduction to Image Processing
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• WL and WW effect:
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E. Fatemizadeh, Sharif University of Technology, 201133
Medical Image Analysis and Processing
Introduction to Image Processing
33
• Paradigm of image processing:– Low-level processing
• Inputs and outputs are images• Primitive operations: de-noise, enhancement,
sharpening, …– Mid-level processing
• Inputs are images, outputs are attributes extracted from images
• Segmentation, classification,…– High-level processing
• “Make sense” of an ensemble of recognized objects by machines
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E. Fatemizadeh, Sharif University of Technology, 201134
Medical Image Analysis and Processing
Introduction to Image Processing
34
• Matlab Image Processing Read/Write:– imformats– imfinfo, imread, imwrite– dicominfo, dicomread, dicomwrite– analyze75info, analyze75read (Mayo Clinic)– interfileinfo, interfileread
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E. Fatemizadeh, Sharif University of Technology, 201135
Medical Image Analysis and Processing
Introduction to Image Processing
35
• Matlab Image Processing Display:• image, imagesc, imshow, imtool, subimage• colorbar, montage
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E. Fatemizadeh, Sharif University of Technology, 201136
Medical Image Analysis and Processing
Introduction to Image Processing
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• Matlab Image Processing Type Conversion:• double, ind2gray, im2double• uint16, uint8, gray2ind
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