Introduction to Medical Imaging

May 2, 2023 1

Chapter 1: Introduction

Hossain Md ShakhawatDepartment of Information ProcessingTokyo Institute of Technology

Digital Image Processing -3rd Edition by Rafael C. Gonzalez, Richard E. Woods

One picture is worth more than ten thousand words

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Objectives of the chapter

Introduction to Digital image processing (DIP) Define the scope of DIP Historical background Introduce the application areas Introduce the principle approaches of DIP Components of image processing Provide directions to the book

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What is Image ? Mathematically, Image is a two dimensional function f(x,y)

where the x and y are spatial co-ordinates and the amplitude of function “ f ” at any pair of co-ordinates (x,y) is called the intensity of the image at that point.

Analog Image: when x, y and the amplitude values of f are continuous quantities

Digital Image: when x, y and the amplitude values of f are all finite and discrete quantities.

Digital image is composed of finite number of elements called pixels, each of which has a particular location and intensity

value.

Digital Image Processing DIP is the processing of digital image in a digital manner

meaning that is using a digital device like digital computer. Two major application areas:

1. Improvement of pictorial information for human interpretation.

2. Processing of image data for storage, transmission and representation for autonomous machine perception

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Digital Image Digital Computer

+ Digital Image Processing

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Level of Image Processing

Image to image transformation

Low Level

Image to attribute transformation

Mid Level

Attribute to image transformation

High Level

Information about

Attributes

Input Process Output

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Post Processing

Revealed Underplayed Information

Advantages of Digital Image

Processing

Applications of Digital Technology

Origin and Evolution of DIP

DIP technology evolved with the advancement in digital computers

1920 -> Bartline cable system reduced the time for transmission from week to hours

1921 -> pictures were produced from a coded tape by telegraph printers 1922 -> Improvements in the reproduction system increased visual quality 1929 -> Number of gray levels increased to 15 from 5 1940 -> Invention of modern digital computer 1940 to 1960 -> Development of transistors, IC, programming language,

operating system and microprocessor made the computer efficient enough for DIP.

1960 -> First use of computer to correct images of moon 1970 -> Early applications in medical imaging 1980 to till date -> Enabled the modality of image analysis and computer

vision

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Pictures were sent using submarine cable for news

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Application Fields Unlike the humans who are limited to visible band of

electromagnetic spectrum (EM), the imaging machines cover almost the entire EM spectrum from gamma to radio waves.

Thus DIP encompasses a wide and diverse fields of applications that human are not accustomed to.

One efficient way is to analyze the fields based on the sources of image:

Gamma ray imaging X-ray Imaging Ultraviolet imaging Imaging in visible and infrared bands Imaging in microwave band Imaging in radio band

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Based on gamma rays. Includes nuclear medicine(i.e. bone pathology, PET) and astronomical observations.

Nuclear Medicine: 1. Radioactive isotope is injected into

body2. Isotope emits gamma rays as it decays3. Images are produced from the

emissions, collected by gamma ray detector.

Examples: Bone scanning, Positron emission tomography (PET)

1. Bone Scan 2. PET ImageAstronomical observation:• A star in the constellation area of Cygnus

exploded thousands years ago. This generated the superheated gas cloud called Cygnus loop cloud, that glows in a spectacular array of colors.

• Unlike the above two (1 & 2) this image (3) was obtained using the natural radiation of the object.

3. Cygnus loop of gas cloud

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• Imaging with X-rays:1. An X-ray beam produced by X-ray tube passes

through the body. 2. On it’s way through the body, parts of the energy of

the X-ray beam are absorbed, called attenuation of the X-ray beam.

3. On the opposite side of body, detectors or a film capture the attenuated X-rays, resulting in a clinical 2D image.

4. In Computed Tomography, the tube and the detector are both rotating around the body so that multiple images can be acquired for 3D visualization.

• Examples: Medical (X-ray radiography, computed tomography (CT), mammography, angiography and fluoroscopy) and industrial imaging.

1. Radiography of chest

2. CT scan of head

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• The ultraviolet light is not visible but it offers a wide area of applications: lithography, industrial inspection, fluorescence microscopy, lasers, biological imaging and astronomical observations.

1. Smut Corn Detection Left: Normal Corn Right: Smut Corn

2. Mouse Brain Tissue Section[ Source: http://www.microscopyu.com/galleries/fluorescence/index.html ]

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• Infrared imaging has the unique capability to observe sources of faint sources of visible-near infrared emissions of the earth surface including cities, villages, gas flames and fires.

• Offers extreme level remote sensing and also in medical science

1. Satellite image of hurricane Katrina

2. photography

• Imaging in the visible band

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• Radar imaging provides its own illumination (microwave pulses) to illuminate the subject and capture the image.

• Instead of using lens it uses an antenna and digital computer to record or capture the image.

• Major application: radar imaging

• Radar imaging can collect data of any region without regarding the weather or ambient light conditions.

• It can penetrate clouds.

1. Radar image of Tibet mountain

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• Like the other end (gamma ray) of spectrum major applications of radio band are also medicine and astronomy. Ex: MRI (Magnetic resonance imaging ).

• MRI is Safer than CT

• MRI:1. Places the patient in a powerful magnet

and passes radio waves through the body in short pulses.

2. Each pulse causes a responding pulse of radio waves to be emitted by the body (H2).

3. Location and strength of these signals is captured to form the 3D image

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Others

1. TEM Image of Polio Virus2. Ultrasound image of

Unborn Baby3. SEM Image of Polen

Grains

1 2

3

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Components of DIP System

Image Displays Computer Mass

Storage

HardcopySpecial Image

Processing Hardware

Image Processing Software

Image Sensors

Network

Problem Domain

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Directions for the rest of the book