Computer Basics PDF

142-B14-DW IMAGE FORMATION & MANAGEMENT SYSTEMS  Topic 1: Computer Basics  COMPTENCIES DEVELOPED IN TOPIC 1 Specific Learning Objectives LO M CAMRT 1- Understand the basic functions of a computer...

142-B14-DW IMAGE FORMATION & MANAGEMENT SYSTEMS  Topic 1: Computer Basics  COMPTENCIES DEVELOPED IN TOPIC 1 Specific Learning Objectives LO M CAMRT 1- Understand the basic functions of a computer LO#10 RTR.2.2, RTR.2.5 2- List and define the basic function of the hardware components in a LO#10 computer 3- Identify the primary computer tasks performed by the technologist LO#10 4- Distinguish between different types of image Storage systems LO#10 5- List the methods that computers use to communicate LO#10 01XT E3.1, 3.2 & 3.3 RTR.2.5 6- Compare the various types of network topologies LO#10 7- Describe the potential network risks, and the safeguards required in LO#10 medical imaging computer systems 8- State the data storage & transmission requirements of a PACS LO#10 9- State the applications and advantages of Telehealth and Telemedicine LO#10 10-Define and describe the components of Teleradiography LO#10  Information videos 1. Computer binary code: https://www.bing.com/videos/search?q=how+computers+work+tutorial&ru=%2fvideos%2fsearch%3fq%3d how%2bcomputers%2bwork%2btutorial%26FORM%3dHDRSC4&view=detail&mid=262BC819A65C45B5476 B262BC819A65C45B5476B&rvsmid=425E20CA81BAA7DB1BB0425E20CA81BAA7DB1BB0&FORM=VDRVRV 2. Computer Hardware and software: https://www.bing.com/videos/search?q=how+computers+work+tutorial&ru=%2fvideos%2fsearch%3fq%3d how%2bcomputers%2bwork%2btutorial%26FORM%3dHDRSC4&view=detail&mid=41CD00A5413EE5BF46E 341CD00A5413EE5BF46E3&rvsmid=425E20CA81BAA7DB1BB0425E20CA81BAA7DB1BB0&FORM=VDQVAP 3. Hard Disk Drive: https://www.youtube.com/watch?v=x533qY_Fhk0 4. RAIDS 0, 1 and 5: https://www.youtube.com/watch?v=GQO1llEFCs8 – view only the explanations on RAIDS 0 and 1 https://www.youtube.com/watch?v=LTq4pGZtzho – view only RAID 5 5. Networking: https://www.youtube.com/watch?v=HEEnLZV2wGI 6. DICOM: https://www.dicomstandard.org/current 7. What is a pixel: https://www.youtube.com/watch?v=uyLDA9QT8EY 8. ADC: https://www.youtube.com/watch?v=HlGJ6xxbz8s 9. Image matrix size and shades of gray – bit depth: https://www.youtube.com/watch?v=9G-mCRaPoRc 10. Radiologist Job Offer – work from home: https://jobs.car.ca/company/custom-teleradiology-services-0259 4 A computer  consists of input, output and data processing devices  It processes data into information under the control of a stored program o Data: unstructured facts o Processes: changes take place o Information: meaningful facts or processed data o Stored program: set of instructions 5 Important dates in the history of computers: The first electronic digital computer was designed and built in 1939 The first general-purpose electronic computer was developed in 1946 at a cost of $500,000. It contained more than 18,000 vacuum tubes that failed at an average rate of one every 7 minutes In 1948 the transistor was invented and replaced vacuum tubes A transistor is an electronic switch that alternately allows or does not allow electronic signals to pass “stored program” computers were built using transistors fast forwarding the advancement of computer science 6 7  The Transistor solid-state device that controls the movement of electrons, and consequently, electricity In computer technology it is used as an electronic switch to process units of data. Controls the flow of data (current) it can be turned on/off very rapidly by switching every 0.000000001 seconds It is made of semi-conducting material: silicon and germanium Up to one million transistors/cm2 can be fitted inside a computer processor (CPU) Intel company produces microprocessors with transistors measuring only 45 nanometers wide. A nanometer is one-billionth of a meter! 8  Computer applications in Radiology Nowadays, computers are used to control every electronic device or machine in radiology such as high-voltage x-ray generators and radiographic control panels, making digital radioscopy and digital radiography a routine. The first large-scale radiology application was computed tomography (CT) followed by Magnetic Resonance Imaging (MRI), Ultrasound (US), and Nuclear Medicine (NM) Telecommunication systems have provided for the development of teleradiology, which is the transfer of images and patient data to remote locations for interpretation and filing. 9  Operating Systems Operating systems basically manage all the resources of the computer. It acts as an interface between the software and the computer physical components (hardware) Examples: o DOS (text mode OS) o Microsoft: Windows 11 o Apple: Mac OS X o Unix and Linux (free and open source) o iOS (Apple mobile) o Android (mobile) Computer Hardware: the physical computer components - input and output devices Software: the programs operating the hardware Moodle & LEA are online learning platforms that provide a safe learning environment 10  Computer Language The Binary Code the foundation of computer programming and language is a machine language that uses one and zero values to process data collected from the computer’s input devices the binary code data processing is performed by a series of switches (transistors) that are either turned on or off o If the transistor circuit is closed & current passes thru’ then it is assigned a value of one o A value of zero is assigned when the circuit is open and no electrical signal passes thru’ o Each 1 and 0 represents a bit (single unit of data). A byte is made up of eight bits and is the amount of memory needed to store one alphanumeric character 11  The alphabet in binary code Letter Binary Letter Binary Letter Binary Code Code Code A 01000001 J 01001010 S 01010011 B 01000010 K 01001011 T 01010100 C 01000011 L 01001100 U 01010101 D 01000100 M 01001101 V 01010110 E 01000101 N 01001110 W 01010111 F 01000110 O 01001111 X 01011000 G 01000111 P 01010000 Y 01011001 H 01001000 Q 01010001 Z 01011010 I 01001001 R 01010010 12  Assemblers, interpreters & Compilers and Application Programs Computers understand only 0s and 1s. Assemblers, compilers, and interpreters are software programs used by humans to communicate between everyday language and the language of the operating system Assemblers: computer program that recognizes symbolic instructions such as “subtract (SUB),” “load (LD),” and “print (PT)” and translates them into the corresponding binary code Compilers and interpreters: Compilers and interpreters are computer programs that translate an application program from its high-level language, such as Java, BASIC, C++, or Pascal, into a form that is suitable for the assembler or into a form that is accepted directly by the computer binary code. Application programs: Such as Word, Excel, iTunes, and Spider Solitaire are application programs written in one of many high-level computer languages and translated through an interpreter or a compiler. Application programs allow users to perform tasks like printing, complete income tax forms, evaluate financial statements, or reconstruct images from x-ray transmission patterns. 13 ❑ The box or tower:  holds the components in a relatively cool, clean and safe environment  Keeps the radiofrequencies from spreading outside the box ❑ The motherboard:  printed circuit board that is the foundation of a computer  It allocates power to the CPU, RAM, and all other computer hardware components and allows them to communicate with one another  provides the electrical connections between components 14 ❑ The Processor or Central Processor Unit (CPU)  It handles all instructions sent by the hardware and software. (computer brain)  It consists of a series of arranged transistors to manipulate data  The Intel Core i5-11600K (6-core) can perform 346,350 millions of instructions per second (MIPS) at a speed rate of 4.92 GHz  Clock speed determines how quickly each task is executed by the processor and it is measured in gigahertz (GHz) 15 ❑ System Clock or Internal Clock  regulates the rate at which instructions are executed and it synchronizes all the computer components.  The clock frequency is simply the number of clock ticks/cycles per second.  The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction. The faster the clock, the more instructions the CPU can execute/sec. thus the faster the computer is.  A good processor speed is between 3.50 to 4.2 GHz (4.2 billion cycles/sec.) 16  “stored program” computers were built using transistors fast forwarding the advancement of computer science. T or F What is the solid-state device in a computer that controls the movement of electrons, and consequently, electricity? The materials used to build Transistors are silicon and germanium, which have semiconducting properties. T or F Which computer generation used vacuum tube devices? The first large-scale radiology application was magnetic resonance imaging. T or F Teleradiology? the transfer of images and patient data to remote locations for interpretation and filing Réseau Universitaire Intègre de la Sante et Services Sociaux input and output devices are hardware components in a computer In binary code language, a value of one is assigned when the transistor circuit is closed and current passes through. T or F In computer systems, what is the job of the assemblers? computer program that recognizes symbolic and translates them into the corresponding binary code Which computer component provides electrical connections between components? A good processor speed is between 3.50 to 4.2 MHz. T or F 17 BUS A common electrical pathway between devices. It is the computer’s information highway. Examples: o Data moves between the hard disk and the CPU o Data moves between the graphics card and the CPU o Data needs to move between the CDROM & CPU 18  http://static.howstuffworks.com/gif/motherboard-dimm.jpg RAM: short-term storage of data. Temporary storage. The stored data in RAM is deleted when system is turned off. More RAM improves speed of computer Graphics Card: creates the images that appear on the monitor. It can also be connected through an expansion slot Sound card: records and reproduces sound. It can also be connected through an expansion slot BIOS (Basic Input/output System): It contains a simple set of instructions from the computer o It assists in booting up the computer o Verifies the peripheral devices to make sure that they are working well o Once the computer is up and running, it serves as the intermediary between the operating system and the hardware 19  Port/Connectors A collection of connectors sticking out of the back of the PC that link adapter cards, drives, printers, scanners, keyboards, mice, and other peripherals  Complimentary Metal Oxide Semiconductors(CMOS) Memory chip with own battery that preserve’s hardware components information when computer is turned off. It also stores information such as the system time and date  Network Interface Card (NIC) Enables PC to connect to other computers in a network. Common component to break down in a radiology workstation  Power Supply: Supplies electricity to the PC and it cools off the system with an integrated fan 20  Hard Disk Drive (HDD): o Storage device used to store all programs and documents on a PC. It requires a constant power source o Electro-mechanical device with moving components o A device called RAID (Redundant Array of Independent Discs) which can store a great amount of data with redundancy is commonly used for image storage in a radiology system Solid State Drive (SSD) o storage device that allows reading, writing, and storing using a processor (controller) to read and write data RAID o data is stored in microchips, rather than discs making it faster A cloud drive o Web-based service that provides storage space on a remote server. Cloud drives, which are accessed over the Internet with client-side software, are useful for backing up files. Modern PACS systems are using this expensive technology 21  CD/DVD Disk Drives: an optical disc drive (ODD) that uses laser light or electromagnetic waves to read or write data from an optical disc. Most drives can read and write on to discs. o Optical discs – CD/DVD  Read Only Memory (ROM)  Write once – Read many (R)  Read and write many times (RW) 22  Computer peripherals What computer devices perform both output and input function? 23 24 COMPUTER NETWORKS 25  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK Computer network: telecommunication network that permits the transfer of information between computers Server: computer that provides service to other computers on the network ex. WEB server, mail server, archive server Thin client: has no HDD and needs constant communication with the server. A networkable device that needs a server to complete its tasks. Requests services and resources from a server. It is a computer that mainly serves to display the information ex. Printer Thick client: (fat client) a computer workstation that can work independently of the network by processing and managing its own files. Also capable of performing high level processing tasks such as 3D image reconstruction 26 In Radiology, thick client computer workstations create 3D reconstructed CT and MRI images 27  MEDICAL IMAGING COMPUTER WORKSTATIONS  A typical radiology workstation is equipped with: o 16g RAM o 2TB of storage capacity o CPU 3.2G Quad Core o Monitor is 3Mp 28  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK Network classification: o LAN – local area network connects computers within a department. Ethernet is the most common used LAN protocol (Dawson Network) o WAN – wide area network connects computers and LANs over the medium or large distance. Internet is the largest WAN Network protocols: o a set of rules governing exchange of information in an easy, reliable and securely o Standards for communication over the network. Both hardware and software must comply with established protocols Transmission Control Protocol / Internet Protocol (TCP/IP) o communication protocols used to interconnect network devices on the internet designed for internetworking o It is also used as a communications protocol in a private computer network (an intranet or extranet) Packets of Data: information is divided into packets when transmitted by sender and reassembled back by the destination computer according to the protocols 29  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK The Open System Interconnections (OSI) Model o Standardizes network architectures to a universal model o vendors sell network equipment according to these standards o It consists of 7 layers, where each layer follows a specific protocol and data flows two ways o The information is passed from layer to layer o Each layer adds or removes information packets  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK IP address: o Each computer is assigned a unique internet Protocol (IP) address o There are 4.3 billion (232) possible unique addresses o IP allows for routing of individual packets from one network to another MAC address: o Unique physical address to identify individual hardware components Gateway: o a network node that forms a passage between two networks operating with different transmission protocols. 31  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK DATA TRANSMISSION Carrier: The carrier is the mode or technology used for data transmission Types of carriers: o Phone lines (not recommended) o Twisted pair wires only good for less than 100m after that the signal degrades o Coaxial cables – (sturdiest) o Fiber optics – (glass threads) o Satellite Wireless - (infrared or radiofrequencies) 32  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK Twisted Pair Wires: o Currently the most widely used carrier in hospital’s Intranet network. o Bandwidth: 10 to 100 Mbps (depending on Cat cables used) Wireless: o Connection is either infrared or radiofrequencies - no physical cable o Router for Local Area Network (LAN). o Satellite for Wide Area Network (WAN). o Examples: Cell Phone, Bluetooth & Wi Fi devices Router Ethernet 33  DEFINITIONS AND BASIC PRINCIPLES OF A COMPUTER NETWORK Fibre optic carrier: o Transmits data as light impulses along a wire made of strands of glass/plastic fibres o Used as a long-distance carrier, e.g., MUHC inter-hospital cabling. o Advantages: Much faster than conventional copper wire. Not subjected to electromagnetic interference. Bandwidth: > 10 Gbps. 34  Computer Routers Computer network device responsible for receiving, analyzing, and forwarding data packets among the connected computers in the network. Router 35  Network Sizes Local Area Network (LAN): a small network generally concentrated in 1 physical location – Dawson College o An Intranet is a web-based LAN reserved for a specific organization. Login is done from an Internet browser and usually requires a specific username and password o Example: My Dawson Portal Wide Area Network (WAN): a very large network o a phone company o World Wide Web (or Internet) is the largest network 36  Hub and Switch Devices in a Network o Hub is a repeater that sends every packet to all connected devices in a network. o Switch filters and forwards packets only to specific destinations in the network its MAC address 37  Network Topology Network Topology: A network topology is the pattern in which computers/printers are connected to a local area network (LAN) or other network via links Star or Client Server is the most common topology used in modern forms of Ethernet including Radiology departments o Ethernet a system for connecting computer devices to form a LAN, with protocols to control the passing of information and avoid simultaneous transmission by two or more systems 38  STAR TOPOLOGY Client/Server based system Clients query the server for specific information such as x ray images. The information (images) is sent to the client station for viewing and/or processing. It does not allow direct traffic between devices or clients. A Picture and Archiving Computer Systems (PACS) is an example of a network system used in Radiology 39  STAR TOPOLOGY Advantages of a Star (Client/Server-Based) PACS System: o Studies are available from all client stations o Patient’s old studies are available at same time as new study o Only one user can process a study at a time o Many users can view at the same time o Remote access Disadvantages: o Server failure can halt storing of exams thus lost studies, slow/down time o All new acquired studies are back logged on modality computer o Network can be heavy at times because of the server bottle-neck o Remote access security 40  Other Network Topologies BUS Ring Topology 41  Web-Based System to access a network The client uses an internet connection to access the network web server remotely to access information such as radiographic images in a PACS. The client’s application software is run from a remote server. Advantages: o Client’s hardware does not need to be very powerful. All it needs is to be able to run a Web browser to connect to the network e.g., ▪ Dawson College Portal Website (https://www.dawsoncollege.qc.ca), ▪ MUHC PACS website (https://telerad.rad.mgh.mcgill.ca/InteleBrowser/app) o Images can be read from anywhere in the world Disadvantages: o Data download from the remote server is much slower o Limited functionality of software ▪ In a PACS system, the images are available only in JPEG format 42  Internet and Intranet Internet (open systems between groups): o An international network of networks using the TCP/IP protocol o Transmission Control Protocol/Internet Protocol (TCP/IP) is a suite of communication protocols used to interconnect network devices on the internet Intranet (closed systems between a single group): Local computer network that uses TCP/IP to share information within an organization 43  Telehealth & Telemedicine Telemedicine & Telehealth are telecommunication applications used to provide the community with medical information and services (Info-Sante 811) Telehealth is more generic and includes prevention Telemedicine is more for diagnosis and treatment Applications: diagnosis, education and research o Phone/video conferencing o Teleradiology o Telepathology o Telesurgery 44  Telehealth & Telemedicine Advantages: o Can serve rural and urban populations: ✓ Specialist consultation ✓ Continuous education videoconferencing ✓ Remote monitoring: wearable monitoring devices ✓ Treatment o Barriers: ✓ Availability of technology in homes and rural centres ✓ Limited human interaction with patients 45  Teleradiology The remote transmission of XR/CT/MRI/US/ANGIO studies from one location to another for the purposes of interpretation and/or consultation via Internet, WAN, LAN, satellite or phone line Users in different locations may simultaneously view images with greater access to secondary consultations and improved continuing education Many Rads provide consultation to other physicians from home (or from their favorite vacation location!) COVID has caused a significant increase in the use of teleradiology 46  “Réseau Universitaire Intègre de la Sante et Services Sociaux” RUISSS Each RUIS (network) has the responsibility to coordinate tertiary health care services to remote areas in the province through its associated teaching hospitals, and to support the training and development of healthcare professionals in their corresponding regions Definition of Tertiary Care: Specialized consultative care, usually on referral from primary or secondary medical care personnel 47  Network Security Potential Risks: o Viruses o Ethical Issues o Human errors o Confidentiality issues o Defective hardware/software o Potential data loss, file corruption or lack of integrity o Reliability & integrity of data transmission o Encryption: data should be translated into codes before transmission 48  NETWORK SECURITY Anti-Virus Programs: o MacAfee, Microsoft Defender, Total AV, Avast, Norton, ScanGuard, etc. Anti-Spyware/Spam/Worms/Fraud Protection Programs: o Prevent/block: ▪ installation of spy software ▪ unauthorized control of computer ▪ “phishing”: unauthorized collection of sensitive data ▪ unwanted “spam” i.e., e-mails ▪ “worms”: self replicating program which slows down the network 49  NETWORK SECURITY Firewall: o limits access and notifies the user when external intruders are detected Pop-up Blocker: o Unwanted advertisement windows Encryption: o A technique that encodes data before transmission 50 Storage & Transmission (sharing) of medical images 51 How many bytes are there in a kilobyte, megabyte, gigabyte and terabyte?  One byte = 8 bits  1024 bytes = 1 kilobyte  1 Terabyte = 1024 GB  one million bytes = 1 megabyte  1 Gigabyte = 1024 MB  one billion bytes = 1 gigabyte  1 Megabyte = 1024 KB  1 trillion bytes = 1 terabyte  1 Kilobyte = 1024 Bytes How many bits can be stored on a It is used to describe the size of the: 64-KBytes chip?  1024 Bytes in a kilobyte  Matrix Size  64kB x 1024 bytes = 65536 bytes  Image size  Chip capacity in bytes = 65536  Bit Depth-dynamic range  65536 bytes x 8 bits = 524288  Storage capacity  Chip capacity in bits = 524,288 52 The Size of the image File Matrix size x Bit Depth 53  The image matrix Matrix: Array of pixels arranged in two dimensions (rows - H and columns - V) o Matrix size is expressed in # pixels (rows - H) X # pixels (columns - V) Pixel: Discrete picture element forming the matrix 54 55 56  Image matrix sizes in Radiology Image matrix sizes per modality: o Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) have image matrix sizes of 256 × 256 to 1024 × 1024 o Radioscopy: 1024 × 1024 o Radiography: 2048 × 2048 o mammography: 4096 × 4096 57 Pixel Size = Image AREA size (mm) divided by matrix size (total # of pixels) 58  Dimensional Image Size (area) = 12 mm x 10 mm = 120 mm2 (area)  Matrix size = 8 pixels (horizontal) x 8 pixels (vertical) = 64 pixels  Pixel Size = 120 mm2 divided by 64 pixels = 1.875 mm2 59  Bit Depth: o # of shades of gray a pixel is able to store and display o Common bit depths in radiology: ▪ 28 = 256, 29 = 528 and 210 = 1024 60  Bit Depths: 1 bit (21) = 2 shades of gray 2 bits (22) = 4 shades of gray 3 bits (23) = 8 shades of gray 4 bits (24) = 16 shades of gray 8 bits (28) = 256 shades of gray 16 bits (216) = 65,536 shades of gray 24 bits (224) = shades of gray 61  Calculate the Image File Size & Storage capacity 1- Calculate the Image file size: Matrix size = 64x64, Bit Depth = 28 Image File Size = Matrix size x Bit Depth Image File Size = 64 x 64 pixels x 256 bits (28) Image File Size = 1,048,576 bits divided by 8 bits = 131,072 bytes = 1.31 kB 2- How many images of this size can be stored in a 700 MB CD? 131,072 BYTES = 0.131072 MB 700 MB/ 0.131072MB = 5,340 images 3- Now, How many images in 1 GB of storage? 1000MB/0.131072 MB = 7,629 images 62  Calculate the Image File Size & Storage capacity How much computer capacity is required to store an MRI examination that consists of 120 images, each with an image matrix size of 256 x 256 and 256 shades of grey (28 Bit depth )? SIZE OF MATRIX 256 PIXELS X 256 PIXELS 65536 PIXELS IMAGE FILE SIZE 65536 (MATRIX SIZE) X 256 (BIT DEPTH) 16,777,216 BITS CONVERSION OF BITS INTO BYTES 16,777,216 BITS / 8 2,097,152 BYTES # OF IMAGES TIMES NUMBER OF 120 X 2,097,152 BYTES 251,658,240 BYTES BYTES PER IMAGES CONVERSION OF BYTES INTO MB 251,658,240 bytes / 1,000,000 251.65824 MB 63  Raw Data & Image Data Raw Data: the unprocessed image data file acquired by the Digital Imaging UNIT before it is reconstructed into an image file Image data: It is a fraction of the raw data after adjustments….. a great deal of nonessential background data which is part of the raw data is discarded. Size of image file is lower than the raw data file raw data Processed data 64 65  Analog Signal Consists of continuous information Examples: o Watch with hands o X-ray image on a film o Video signal from TV camera o Electrical current Advantages: o Higher spatial resolution – more detail o Low storage space requirements o Fast transmission speed is possible Difference between Analog and Digital Signals | AddOhms #6 - YouTube 66  Digital Signal Consists of discrete units of information, i.e., limited values between two readings Examples: o Watch with number display – digital watch o data from any image acquisition systems such as CT, MRI, CR, DR, etc. o Xray signal is transformed into a digital signal by the ADC 67 68  Analog-to-Digital Converter (ADC) device Analog-to-Digital Converters (ADC) translate analog signals, real world signals like temperature, pressure, voltage, current, distance, or light intensity, into a digital representation of that signal. This digital representation can then be processed, manipulated, transmitted or stored. , ADCs are commonly used in medical imaging equipment 69  SAMPLING & QUANTIZATION OF THE SIGNAL BY THE ADC Sampling Specific points in time at which the conversion is to be performed Quantization/Digitization The analog level of the sample is approximated to the closest digital level; the ADC assigns a binary code to it 70 The conversion of the Analog signal to Digital signal causes a loss of information due to the sampling and quantisation because the values of the analog signal between the samples and between the digital levels are lost 71  the Bit Depth of the pixels on an image is determined by the ADC device  An 8-bit ADC converts the analog signal to values between 0 and 256 (28) o each pixel will have values of shades of gray between 0 and 256  The human eye can only discern 25 or 32 shades at one time  The radiological image contains at least 210 different values  Scale of contrast = number of shades of gray 72  The Digital Image Advantages of the Digital image compared to analog image (film): o image manipulation and re-processing are possible ✓ can improve contrast and sharpness on the image ✓ Reduces image noise ✓ Higher margin of error in exposure selection (exposure latitude EL) o Does not require much floor storage o Fast image retrieval and the ability to query and filter the image database o Multiple viewers can access same image from different locations at any time o Lower cost per image Disadvantages of Digital: o Lower spatial resolution (resolving power) Digital vs Analog. What's the Difference? Why Does it Matter? (youtube.com) 73