LEC #1 Medical Imaging: Analog vs Digital

Medical Imaging Types

• Medical imaging uses two types of images: analog and digital.
• They differ in acquisition via the image receptor (IR), processing, and display.
• Analog images use chemical processing and a light box for display.
• Digital images use direct computer processing and a computer monitor for display.

Conventional Radiographic Imaging (Analog)

• This method uses film, intensifying screens in a cassette, and chemically processed film.
• Film is placed between two screens in a cassette.
• The result is a hard copy image viewed on a lightbox but is non-reusable.
• Acquisition and display occur on the same medium (film).

Digital Radiographic Imaging

• Digital imaging is a broad term first used medically in the 1970s for computed tomography (CT).
• It's defined as any image acquisition that produces an electronic image storable, viewable, and manipulable on a computer.
• Acquisition and display are separate, using reusable image receptors processed by a computer.
• Computer monitors are used to display the image (soft copy viewing).

Digital Imaging Modalities

• Computer technology is essential to many modalities, including:
• Computed Tomography (CT)
• Magnetic Resonance Imaging (MRI)
• Nuclear Medicine, including Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET)
• Ultrasound (US)
• Computed Radiography (CR)
• Direct Digital Radiography (DDR)
• Other applications include Picture Archiving and Communication (PACS), controlling high-voltage x-ray generators, and radiographic control panels.

Computers Overview

• Computers perform mathematical computations, manipulate information, make decisions, and interact accurately and quickly.
• They are programmable electronic devices that store, retrieve, and process data.
• They convert data (not useful) into information (useful).

Computer Types and Examples

• Microcomputers typically have a single microprocessor.
• Microcomputers usually fit on a desktop as a PC or notebook, or as an operating console of an x-ray imaging system.
• Minicomputers contain many microprocessors that work together and occupy three or more cabinets.
• CT and MRI computers are examples of minicomputers.
• Mainframe computers and supercomputers contain hundreds/thousands of microprocessors, often requiring an entire floor of building space.
• Mainframe and super computers are used in telecommunications, military, government, airlines and weather forecasting.

Computer Architecture

• A computer system has two principal parts: hardware and software.

Hardware

• Hardware refers to the physical and visible components of a computer.
• Includes input devices, output devices, and internal processing hardware.

Software

• Consists of the programs that instruct the hardware, dictating its operations, data storage, and manipulation.
• Software dictates the instructions for hardware operations to solve problems.
• Softwares control the hardware.

Input Devices

• Hardware to provide data and control signals, including source data entry devices.
• Hardware converts data into a language the computer understands.
• Examples include keyboards, mice, microphones, bar code readers, touch screens, and image scanners.

Output Devices

• Any hardware that converts information into human-readable or perceivable forms like text, graphics, tactile, audio, and video.
• Examples include monitors (CRT, LCD, OLED, Plasma), speakers, printers, plotters, projectors, and earphones.

Internal Hardware Components

• These are the mechanical and processing parts inside a computer's case.
• Common components include:
  • Motherboard
  • CPU-Microprocessor
  • Hard Drive
  • Floppy Drive
  • System Cooling Fan
  • RAM Modules (memory chips)

Case or Cabinet

• Hardware components are housed in a heavy metal case.
• It holds enclosed components in a cool, clean, and safe environment.
• It shields them from external elements like dust, and prevents radio frequency interference.

Motherboard

• It is the main and largest circuit board in a computer.
• Contains important smaller components for correct computer function.
• It serves as a connection board for the most important components.

Computer Evolution

• Early computers used vacuum tubes.
• ENIAC-1st Generation Computer
• Later models used transistors.

Transistors

• The development of transistor technology enabled the development of stored program computers.
• A transistor is an electronic switch that either allows or doesn't allow electronic signals to pass.

Computer Processing

• Processing is carried out through transistors switching on/off millions of times per second.
• Silicon can be doped with other chemicals to acquire different conducting properties.
• Silicon is used to manufacture the most electronic equipment.

Generations of Computers

• First generation used vacuum tubes.
• Second generation used individual packaged transistors.
• Third generation used integrated circuits (IC's).
• Fourth generation uses large scale integration (LSI) and very large scale integration (VLSI).

Integrated Circuits

• An integrated circuit is a silicon chip fusing multiple transistors and other electronic elements.
• Miniaturization made integrated circuit possible.
• Transistors are the building blocks of all microprocessors or integrated circuits.

CPU or Processor

• The CPU is an integrated circuit on the motherboard; the computer's "brains".
• A single integrated circuit containing the CPU of a microcomputer is a microprocessor.
• The CPU interprets and executes instructions.
• CPU tasks: reading data from storage, manipulating data, and moving data back to storage.

CPU Subcomponents

• The CPU includes three subcomponents:
• Arithmetic Logic Unit (ALU).
• Control Unit (CU).
• Memory Unit/Primary Storage.

CPU Subcomponent Functions

• ALU: performs arithmetic (add, subtract, multiply, divide) and Boolean logical calculations (AND, OR, NOT, IF THEN).
• CU - Coordinates functions, controls data transfer between memory and I/O hardware, and directs data to the ALU or memory.
• Memory Unit - CPU contains two types of memory: Random Access Memory (RAM) and Read Only Memory (ROM).

Processing Power

• Processing power is the speed at which a computer executes instructions.
• CPU capacity dictates the internal clock speed.
• Clock speed is measured in Hertz (Hz), Megahertz (MHz), or Gigahertz (GHz), or Millions of Instructions per Second (MIPS).
• CPUs are often named after their manufacturers (e.g. Intel Core i5, AMD Phenom II).
• Higher clock speed equals faster processing and better performance.

BUS

• Movement program instructions and data between the CPU and other hardware components occurs through wired pathways.
• BUS (Creates pathways to allow for flow of data, power and signal).
• A bus interconnects the CPU, memory, and all input/output components.

Random Access Memory (RAM)

• RAM serves as the computer's main or active storage and enables fast access for arithmetic and logical components.
• Stores or holds information currently processed in the CPU.
• Random access means data can be stored or accessed at random regardless of location with equal time.
• RAM retains information only when powered on described as volatile or temporary memory.
• RAM capacity affects the processing speed and efficiency, and it is made using CMOS technology
• Types of RAM include DRAM and SRAM.

Read Only Memory: ROM

• ROM provides secondary storage for unchanging information from manufacturers (Firmware).
• Bootstrap boots the computer.
• BIOS runs initial diagnostics. Basic Input/Output System
• Contents are not lost even when the computer is switched off.
• ROM is non-volatile memory.

Secondary Memory

• Secondary memory used for archival purposes.
• Stores information/data until retrieval.
• It is an archival form of memory, often stored as files.

Types of Computer Files

• Program files: software instructions
• Image files: digital images
• Audio files: digitized sound
• Video files: digitized video files

Units of Storage Capacity

• Electronic data is composed of binary digits.
• Storage capacity measures bytes accommodated.
• Bit: Smallest data unit (0 or 1).
• Byte: 8 bits.
• 8 bytes is needed to store one alphanumeric character
• Word: 16 bits (2 bytes).
• Kilobyte (KB): 1,024 bytes.
• Megabyte (MB): approx. 1 million bytes.
• Gigabyte (GB): approx. 1 billion bytes.
• Terabyte (TB): approx. 1 trillion bytes.
• Hard drive capacity often measured in terabytes.

Secondary Memory - Storage Devices

• Examples:
  • Optical Storage: Compact Discs (CD), Digital Video Discs (DVD), Blu-ray Discs (all external).
  • Magnetic Storage: Hard disc drive (internal or external).
  • Flash Drive/Jump drive/USB drive (external): Small solid state device.
  • Solid State storage: Internal and allows for faster data access; external/internal.

Hard Disc Drive

• Can be internal or external, and runs on the mechanical parts consisting of disks and a magnetic head.
• Discs made of thin, rigid glass or metal platters coated with magnetizable recording material .
• Solid state drives (SSDs) now offer an alternative to hard drives with lower storage capacity.

Compact Discs (CD) and Digital Video Discs (DVD)

• Data is stored as indentations or pits on disc which can be read by a laser.
• Three types exist:
• CD-ROM/DVD-ROM: read-only.
• CD-R/DVD-R: write once, read many.
• CD-RW/DVD-RW: read and write many times.

Flash Drive/Jump Drive

• Small solid state memory portable storage devices with fast data transfers, connects through USB.
• Flash drives are one of the most durable forms of storage.

RAID

• Is a redundant array of inexpensive/independent discs.
• Employs at least two disc drives within a single cabinet that combine for storage.
• RAID systems provide increased reliability since one drive can take over if the other fails.

Jukebox

• CD-ROM drives that handle multiple discs.
• Jukebox can handle up to 2000 CD's, DVD,s and Blu-ray Discs.

Ports

• Data is carried between CPU and peripherals via multiwire lines, connecting via ports.
• Ports link adapter cards, drives, printers, scanners, keyboards, mice.
• Common types: serial, parallel, and USB.

Serial Ports

• Serial ports are universally used for connecting mice and keyboards.
• They send 1 bit of data at a time.

Parallel Ports

• Found on the back of modern PCs with a 25-pin connector.
• Commonly used for printers.
• The parallel port can send 8 bits of data at a time through the connection.

USB Ports

• Universally used to connect jump drives; are the most versatile port.

Computer Software Programs

• Software consists of the computer programs that tell the hardware what to do and how to store and manipulate data.
• Computer Program is the sequence of instructions developed by a software programmer.
• Two classifications exist: system software and application programs.

Systems Software

• Programs that make it easy to operate a computer (e.g., Windows, Linux).
• Systems software often runs/controls the computer's Operating System.

Application Programs

• Written in higher-level language designed to carry out specific user functions.
• Application programs run or control data.
• Most computer programs are application programs.

Operating System Examples

• Examples of operating systems include Windows, Linux, Unix, Mac OS, Android, and iOS.

Application Software Examples

• Application software examples include Word, Adobe Photoshop, graphics software, Excel, and PDF.

Algorithm

• The programmed set of step by step mathematical formulas or instructions that the computer follows to execute their function of solving a problem.
• In digital imaging algorithms are referred to as the computer adapted mathematical functions, equations or calculations that are applied to raw image data during digital image reconstruction.

Computer program

• A collection of many hundreds or even thousands of interrelated algorithms which allow the user to perform a general application such as calculating taxes, word processing, or organizing a data base or image processing.

High-Level Computer Languages

• FORTRAN: Formula translation
• Visual Basic
• Java
• COBOL: Common Business Oriented Language
• Pascal
• C
• C++

Binary Language and Encoding

• All data forms (0-9) must be translated into binary computer language so the computer can understand them.
• This is known as encoding.
• To encode is to change or translate from ordinary characters to binary digits or computer-compatible characters.
• Binary form of data is the only form that a computer can accept, store and manipulate.

Binary Code

• It is a computer language based on 0's and 1's.
• It correlates to the on and off switching action of transistors.

Transistor Action

• Computers only recognize, process, and store data in patterns of transistors switching on and off.
• Switching happens millions of times per second.
  • When transistor switches on: assigned 1.
  • When transistor switches off assigned 0.

Binary Number System

• Computer code is based on the Binary system.

Decimal System

• Uses ten digits: 0 to 9 to represent numbers.

Binary System

• Uses only two digits: 0 and 1.

Conversion to Base 2

• What is the number 20 in binary notation
• Solution = 10100
• Convert to 16 base 2
• Solution = 10000

Binary Digits

• What number is represented by 1011.
• Solution with 2⁰ = 11 Convert the binary digit 1110 to a decimal number. So it will be equal to 14 based on the 2⁰ number line.

Binary Codes

• Computer language based on 0's and 1's.
• Computers read and work in Binary code.
• All data forms must be translated into binary computer language so the computer can understand them.
• Every letter, number, color, etc is translated into a series of 1's and 0's

ASCII Coding System

• ASCII (American Standard Code for Information Interchange) is the most common character encoding format for text dat.
• Allows binary representation of alphanumeric characters.
• Any letter, punctuation, or symbol is encoded in binary.

Computer Operations in Radiography

• Five fundamental operations used in radiography:
• Input: Data entry via keyboard/mouse.
• Processing: CPU processes data into information for observers to solve problems, such as using an image for diagnosis.
• Storage: Permanently or temporally storing information (RAM & ROM).
• Output: display of computer-processed results.
• Communications: Data and output sharing (e.g., images).

Essential Operation

• Arithmetic-logic in processing unit
• Control Unit
• The ability to flow data.

Analog Image Signal Data

• Analog data can have any value without any limits.
• It's represented in continuous format and can assume any value with precise proportionality to the actual measured magnitude.
• Analog signal is recorded and used in its original form.

Digital Image Signal Data

• Digital is rounded to a finite value.
• Digital data representation is represented as discrete data by finite values or integers.
• Digitals signals are a rounded of approximation.

Digitization of Analog Signal

• X-ray intensities during exposure are analog until digitization
• Recorded intensities represents the image in an analog format and its a continuous density spectrum
• Digitizing involves rounding off continuous analog signal measurements into discrete values.
• Digital images is formed through multiple samplings.
• Sampling frequency: How often small parts of the analog signal is taken and reproduced in its discrete digitized form to compose the digital image

Processing

• Digitizing a signal involves assigning a numerical value to each signal point (electrical impulse or light photons) from specificlocations.

Analog to Digital Conversion

• Conversion of Analog Signals from image receptors to digital signals
• Analog signals leaving the receptor (light or electrical) are converted to digital before input.
• Converting with Use of Analog-to-digital converter (ADC).

Digital-to-Analog Conversion

• Conversion of receptor signal is necessary because computer processes only digital signals.
• Processed digital signals require Digital-to-Analog conversion before monitor display since humans perceive analog information.
• Monitor converts the digital signals.
• Digital-to-analog converter (DAC): transforms the digital signal representing the image shades of grey visible on a monitor as the image.