Instrumentation_CT

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Author:
Radiology2
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59094
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Instrumentation_CT
Updated:
2011-01-11 01:27:54
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CT
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Week #1
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  1. 3 categories of software are:
    • 1: System software (Windows)
    • 2: Applications software (Microsoft Works)
    • 3: Software development Tools (BASIC)
  2. Hardware components include:
    • 1: Input device (keyboard, mouse)
    • 2: CPU (brain)
    • 3: Internal Memory (part of CPU)
    • 4: Output device (printer, cd)
    • 5: External Memory or Storage (PAC's)
  3. What is a microprocessor?
    digital integrated circuit that processes data and controls the general workings of the computer
  4. Analog computers operate how?
    on continuous physical quantities that are not digital
  5. Digital computers operate how?
    on digital data through math and logical operations
  6. Does digital or analog use the binary system?
    Digital
  7. Elements of digital signal processor
    • Info is put into computer in analog form
    • ADC converts the input to digital for processing
    • Data is processed in digital form
    • DAC converts the output to analog for viewing
  8. What does PACS stand for?
    • Picture
    • Archiving &
    • Communication
    • Systems
  9. Dow does Tomography work?
    Film and Tube move simultaneously in opposite directions to produce an image based on a focal plane and thickness chosen by the technologist
  10. How early did Tomography start?
    1921
  11. What is Pluridirectional Tomography?
    • Tube and film moved in "figure 8" (opposite directions)
    • Used to compensate for the traditional tomographies downfalls (elongating kidneys and having superimposition on planes close to focal plane)
  12. What is tomosynthesis?
    • uses digital flat-panel technology
    • combines digital processing techniques & conventional tomographic acquisitions
  13. What can the tomosynthesis possibly be used for?
    Potential to be used as a low dose imaging alternative to CT
  14. What was Godfrey Newbold Hounsfield working on in 1951?
    EMI Limited-beginning to work on radar systems and computer technology
  15. What was Godfrey Hounsfield doing in 1967?
    He was investigating pattern recognition and reconstruction techniques using the computer
  16. Who is Godfrey Hounsfield?
    Discoverer of CT
  17. The original lathe bed scanner took how long to scan an object?
    9 days
  18. What type of radiation did the Lathe Bed scanner use?
    americium gamma radiation
  19. Who is Allan MacLeod Cormack?
    He developed solutions to the mathematical problems in CT
  20. Who is Dr. Robert Ledley?
    He developed the 1st whole body CT scanner
  21. 1st Generation Scanners produced in which year?
    1971
  22. 1st Gen CT-used what type of beam?
    Pencil Beam
  23. 1st Gen CT-had how many detectors?
    1 (single detector)
  24. How long was the total scan time per image on 1st Gen CT?
    5min per image (would result in patient motion-of course)
  25. How did 1st Gen CT work?
    Would rotate 1* to the next angular position to acquire the next set of images
  26. What type of beam is used in 2nd Gen CT?
    Fan beam geometry
  27. What year did the 2nd Gen CT come out?
    1975
  28. How many detectors are used in the 2nd Gen CT?
    30 detectors
  29. How long did the 2nd Gen take to acquire an image?
    20 seconds
  30. 2nd Gen CT uses multiple detectors, how?
    in a Straight line
  31. How does the 2nd Gen CT work?
    the tube/detector assembly moves across the patient and then rotates by 5* (unlike the 1st Gen-1*)
  32. 3rd Gen CT was introduced in which year?
    1975
  33. 3rd Gen CT uses what type of beam?
    Fan Beam
  34. How are the detectors place in 3rd Gen CT?
    in an arc (opposed to 2nd Gen where they were a straightline)
  35. Total scan time of a 3rd Gen CT?
    less than 1sec per image
  36. 3rd Gen CT started using new technology known as?
    Slip Rings
  37. 3rd Gen CT was AKA?
    Rotate-rotate scanners
  38. 4th Gen CT uses what type of beam?
    Fan beam
  39. 4th Gen CT how do the detectors work?
    The detectors encircle the patient but do not rotate
  40. What does rotate in 4th Gen CT?
    the tube rotates around the patient (not the detectors)
  41. What was a disadvantage to 4th Gen CT?
    more scatter radiation-a single slice requires 4800 detectors
  42. 5th Gen CT built when?
    1980-1984
  43. What was the 5th Gen CT mainly used for?
    Cardiac applications (able to "freeze" a beating heart)
  44. 6th Gen CT is a what?
    Dual source scanner
  45. How does a 6th Gen CT work?
    2 xray tubes, & 2 sets of detectors that are offset by 90*.
  46. What is 6th Gen CT mainly used for?
    Cardiac imaging & some CTA's
  47. 7th Gen CT uses what?
    Flat-panel digital detectors similar to the ones used in DR
  48. Is 7th Gen CT used today?
    No, it is still a prototype
  49. What are the detectors made of in 7th Gen CT?
    Cesium Iodide Scintillator which is coupled to an amorphous silicon thin-film transistor array
  50. What is Slip Ring Technology?
    • Electromechanical device consisting of circular electrical conductive rings and brushes that transmit electrical energy across a rotating interface
    • It allows the tube to continuously rotate & provides electrical power to operate the x-ray tube.
  51. Where are the generators located?
    Within gantry (instead of in control room)
  52. Low voltage slip ring uses how much AC (alternating current)
    480 AC
  53. How does a Low voltage Slip ring work?
    Xray controls are trasmitted to slip ring by means of low voltage brushes that glide in contact grooves on the stationary slip ring then power is provided to the high-voltage transformer which transmits high voltage to the tube.
  54. How does a High-Voltage Slip Ring work?
    • AC delivers power to the high-voltage generator, which then provides power to the slip ring.
    • This is then transferred to the Xray Tube
  55. What are the advantages to Slip Rings?
    • Faster scan times and minimal interscan delays
    • Capacity for continuous acquisition protocols
    • Eliminates the start-stop process with Conventional CT scanners
    • Removal of cable wrap around the process
  56. How Does CT work?
    Photons of x-ray beam (that have passed through the patient) are measured. A series of these measurements is then used to create raw data. A construction process (interpolation) is then used to convert this data into cross-sectional images we look at. In the resulting images each tissue displays it's own characteristics or hounsfield units.
  57. CT flow?
    Console to Host Computer to Scan Controller to DAC or High Voltage Generator to Gantry Control to Gantry to Amplifier to S&H to ADC to Array Processor to Host Computer to Storage Device
  58. What happens within the Console?
    • Instructional commands
    • usually consists of: keyboard, touch panel, window controls, image display
  59. Host Computer?
    • Primary link between Technologist & other components of Imaging system
    • Translates each of Technologists commands entered at console into the "computer language" and passes it on to the scan controller or storage device
    • Stores calculated image
  60. Storage Device?
    • Stores images in digital form to preserve the wide dynamic range of images
    • sores them in 2D pixel arrays
    • Types: Magnetic Tape, Digital Videotape, Optical Disk, Optical Tape, CD
  61. Scan Controller?
    • Responsible for timing & operation of patient table, gantry & high voltage generator
    • Allows operator to communicate with system to enable scanning
  62. High Voltage Generator?
    • (Can be housed in Gantry)
    • Produces the high voltage potential that exists between the cathode & anode of CT x-ray tube
    • Has 30-60 kilowatts
  63. DAC?
    • Digital to Analog Converter
    • used to convert electronic signals sent from the scan controller to the gantry control into the analog(continuous) waveform that the computer can understand.
  64. Gantry?
    Houses the x-ray tube, detectors & data acquisition system.
  65. Aperture of Gantry?
    Usually 70cm (available scan area=50cm)
  66. Gantry tilting range=
    12-30 degrees in either direction
  67. Patient Coordinating System-Assume the Patient is lying how?
    On table in Supine-head first position
  68. in Patient Coordinating System what is Z-axis?
    Extends along the patient table-head to toe
  69. in Patient Coordinating System what is X-axis?
    Extends from patients right to left
  70. in Patient Coordinating System what is Y-axis?
    Extends anterior to posterior
  71. Amplifier?
    • X-rays have passed through the patients body & are measured by detectors
    • The attenuation info is then converted into tiny electrical signals
    • These tiny signals pass through the amplifier to do just that, greatly increase their strength
  72. S&H?
    • Sample & Hold Component
    • The Analog amplified electrical signals are sampled
  73. ADC?
    • Analog to Digital Converter
    • Amplified electrical signals are digitized (so we can view them)
  74. Array Processor?
    • Stores the raw data file
    • Calculates the image that is seen on console
    • Final image is constructed & made available for viewing at the console

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