RDT 102_MIDTERMS EXAM

• Edge Enhancement


  • Occurs when fewer pixels in the neighborhood are included in signal average
  • The smaller the neighborhood, the greater the enhancement
  • High pass filter is used when known frequencies can be amplified and others can be suppressed
  • Suppressing frequencies is aka as masking
• High Signal to Noise Ratio 


  The signal is clear and easy to detect or interpret, while low means that the signal is corrupted or obscured by noise and may be difficult to distinguish or recover
• Stable signal processing


  The output is bounded for bounded input
• Unstable signal processing


  For a bounded input, the output is unbounded in the system
• BIBO[means finite in amplitude]


  Bounded input for Bounded Output
• Local Area Network

  • A small area networked with a series of cables and wireless access point that allows computer to share information and devices on the same network
  • It is least expensive to install and faster than WAN due to their smaller size
  • It has the fastest communication technology because less equipment and fewer resources are needed to complete the network
  • Larger networks are composed of several LANs interconnected to create WAN
• Wide Area Network

  • Network that spans a larger area, city, nation, continent or the world
  • It is used to connect computer that are not physically attached through conventional cables but connected through other means such as telephone line, satellite links and other type of communication cable
  • Most of the operating cost is caused by long data link communication that is often owned by other companies
  • Due to the distance covered, High speed equipment is expensive
• Peer to Peer Networks


  • Computer on the network is considered equal
  • Each computer controls its own information and operation and can function as a client or a server
  • Most popular to small offices and home network configuration
  • Max number of peer is 10- bottleneck and collisions on the network
• Server Based Network


  • There is a centralized computer (the server) that controls the operation, files and sometimes the program of computer (the clients) attached to the network
  • It also provides location for centralized storage and retrieval on the network
  • This type of network requires server to be of high quality and high capacity and the client computer is less expensive
• Client Based Network


  • Instead of sending the entire file to the client for processing, the server processes the resources as requested by the client and returns only the result back to the client
  • It minimizes the load on the network and allows more room for request
• Types of Components of a Network

  • Computer
  • Server
  • Thin Client
  • Thick Client
• Server


  • A computer that manages resources for other computers, servers and networked devices
  • May contain applications, storage for files or manage other various networked task
  • Most often dedicated to one task for the network and is usually the most robust computer in the network
• Thin Client


  • Devices found on a network that request services and resources from servers
  • May be another computer, printer or other networkable device
  • Almost any personal computer is a client as long as it is attached to a network
• Thick Client


  • Can work independently and process and manage its own files
  • Networked: to share resources and for additional security
  • It is generally a high-end computer that can initiate high level processing
  • It is mostly used in specialty application computer/workstations
• Network Connectivity

  • Coaxial cable
  • Twisted Pair Wires
  • Fiberoptic Cable
  • Wireless Connection
  • Network Interface Card
  • Network Hub
  • Network Switch
  • Network Bridge
  • Network Router
• Coaxial Cable


  • Similar wiring used for the cable television that is run into a house
  • It consists of a center conducting wire surrounded by insulation and grounded shield of braided wire
  • The shield minimizes electrical and radiofrequency interference
• Twisted Pair Wires


  • Similar to telephone wires
  • Consist of 4 twisted pair of copper that are insulated and bundled together with RJ-45 termination
  • Comes in various quality and capacity
  • Minimum standard is Cat 5
  • Most commonly used communication in LAN
• Fiberoptic Cable


  • Uses glass threads to transmit data on the network
  • Consist of fiberoptic core that is surrounded by a plastic covering
  • Much faster but expensive and fragile
  • It is easily damaged by kinking or twisting of the cable
• Wireless Connection


  • Connection is made from either infrared or radiofrequency as it means of communication
  • No physical cabling needed but must contain wireless transmitter/ receiver
  • Mobility and convenience
  • Limited range
  • Thickness of the wall and distance from the source must be taken into account
• Network Hubs


  • Simplest device that can be used to connect several pieces of equipment together for network communication purposes
  • Several wiring ports available on it to receive and transmit data to the various pieces of equipment
  • Hubs are commonly used in small office and home application
• Network Switch


  • Similar to hub but it sends data only to those devices to which data is directed
  • Read the destination address from the data and select a direct path to the intended target
  • Reduces network traffic
  • Speeds up the overall network connection
  • Makes the network more efficient
• Network Bridges


  • Created to segment larger network or broken up into smaller networks to reduce traffic within the network
  • Segments can be connected through a bridge
  • The bridges is a physical (wired) connection from one network segment to another
  • It can be recognize in which segment a particular destination address resides and segment to another
• Network Router


  • More sophisticated device
  • It can read portions of messages and direct them to their intended target, even if the device is on a separate network and uses a different protocol

  
• Network Topology

  • Bus
  • Ring
  • Star
  • Mesh
• Bus Topology


  • It is a network in which all devices are physically attached to and listen for communication in a single wire
  • Single point of failure: Wire
  • This type of topology does not need any switches or hubs because computers simply broadcast all the information down the single wire and all computers connected to that piece of wire will receive the information
• Ring Network


  • A network in which the devices are connected in a circle
  • Each device passes its received messages to the next node on the ring and the data transmission move around the circle until they reach the correct receiver
  • If there is a break at some point. It will halt
  • One type of ring topology is ring token
• Star Topology


  • It is a network that has the devices connected to a central hub or switch
  • It can be thought of as a bus topology with the bus collapsed into a central box
  • Transmission of data maybe through a hub or switch to the adjacent network or directly to the device
  • This is the most commonly used network topology
• Mesh Network


  • It is a network topology that has multiple pathways interconnecting devices and networks
  • This type of network has its redundancy built in with the multiple connections
  • The Internet is based on this topology
• Medical Image Processing


  Deals with the development of problem specific approaches to enhance the raw medical data for the purpose of selective visualization as well as further analysis
• Medical Image Analysis


  Concentrates on the development of techniques to supplement the usually qualitative and frequently subjective assessment of medical image by human experts
• Pre-Medical Image Processing


  • Image pre-processing technique that not only removes unwanted artifacts from the medical image but also enhances the required portion
  • Preprocessing takes place in computer where the image histogram is determined
• Post Medical Image Processing


  • Advanced post-processing describes the manipulation of radiographic images to derive additional qualitative or quantitative data
  • Postprocessing is done by the technologist through various user function
• Nyquist Theorem


  The sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original signal will be nearly perfect
• Aliasing


  • Spatial frequency is greater than the Nyquist frequency
  • Sampling occurs less than twice per cycle
  • Information is lost
  • Fluctuating signal is produced
  • Wrap around image is produced
  • Image appears as two superimposed images slightly out of alignment
  • Aliasing results in a moiré effect
  • Aliasing can be problematic because of the same effect occurring with grid errors
• Automatic Rescaling


  • Exposure is greater than or less than what is needed to produce an image
  • Automatic rescaling occurs to display the pixels for the area of interest
  • Images are produced that have uniform density and contrast regardless of the amount of exposure
  • When too little exposure is used, resulting in quantum mottle
  • When too much exposure is used, resulting in loss of contrast and loss of distinct edges because of increased scatter production
  • Rescaling is no substitute for appropriate technical factors
  • Danger exists of using higher than necessary milliampere-second values to avoid quantum mottle
• Look-Up Table (LUT)


  • LUT is used as a cross-reference to transform the raw information
  • LUT is used to correct values. LUT has a mapping function: All pixels are changed to a new gray value
  • Image will have appropriate appearance in brightness and contrast
  • LUT is provided for every anatomic part
  • Each anatomic area has a LUT Used to adjust contrast and density
  • Other terms that may be used for this from various vendors: Contrast rescaling, Contrast processing, Gradation processing, Tone scaling

  
• Window Level


  Controls how bright or dark the image is
• Window Width


  Controls the ratio of black to white or contrast
• Smoothing


  • Aka as low-pass filter
  • Averaging each pixel's frequency with surrounding pixel value to remove high frequency noise
  • Reduction of noise and contrast
  • Useful for viewing small structures such as fine bone tissue
• Background Removal or Shuttering

  • Unexposed borders around the collimation edges allow excess light photons to enter the eyes that is known as veil glare
  • In film screen radiography, black board glare masks or special automatic collimation view boxes was made to reduce veiling glare
  • Automatic shuttering was made to blacken out the white collimation border
  • Removing the white unexposed border reduces the number of pixels that reduces the amount of information being stored