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Seeram: Components of a CT Scanner

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CT. Seeram: Components of a CT Scanner. Major Components. Scanner room Imaging system Generator (?) Electronics Room Power Computer (?) Generator (?) Operator’s Area Display / recording / storage Computer (?). Gantry Provides Structural Framework for. x-ray tube

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slide1
CT

Seeram:

Components of a CT Scanner

major components
Major Components
  • Scanner room
    • Imaging system
    • Generator (?)
  • Electronics Room
    • Power
    • Computer (?)
    • Generator (?)
  • Operator’s Area
    • Display / recording / storage
    • Computer (?)
gantry provides structural framework for
Gantry Provides Structural Framework for
  • x-ray tube
    • modern tubes very large & heavy
    • external cooling (oil heat exchanger)
  • generator / transformer (slip ring technology)
  • Extreme mechanical stability requirements
    • Very tight tolerances for
      • vibration
      • Give / sag
gantry provides structural framework for4
Gantry Provides Structural Framework for
  • collimators
  • filters
  • Detectors / electronics
gantry size must accommodate
Gantry Size Must Accommodate
  • patients
  • size of room
  • Truck transport to hospital

The gantry is pre-assembled at the factory

gantry size must accommodate6
Gantry Size Must Accommodate
  • Transport within hospital
    • hallways
    • doors
    • elevators
      • Typical weight: 3500 lb.
special clinical gantry concerns
Special Clinical Gantry Concerns
  • Patient aperture
  • Tilt range
  • Cooling of
    • electrical components
    • x-ray tube
patient couch
Patient Couch
  • Vertical travel
    • minimum height for stretcher transfer
  • Horizontal travel
    • reduces need for re-positioning patient
    • accuracy
patient couch9
Patient Couch
  • Weight capacity
    • Strength
      • cantilevered
    • Rigidity
patient couch requirements
Patient Couch Requirements
  • Safe for patients
  • Easy to clean
  • Radiolucency
  • Speed
  • Pretty?
    • Siemens offerscolors
imaging system
Imaging System
  • Produces x-rays
  • Shapes & filters (hardens) beam
    • collimates
    • attenuates for uniformity
  • May detect (measure) pre-patient beam intensity
    • Provides digital intensity data to computer
imaging system components
Imaging System Components
  • X-ray tube
  • Generator
    • supplies power to x-ray tube
      • filament
      • high voltage
  • Collimators
    • restricts beam to slice of interest
imaging system components13
Imaging System Components
  • Filter
    • protects patient from low-energy photons
    • provides a beam closer to mono-energetic
    • provides a more uniform beam
  • Detector & electronics
    • also called data acquisition system (DAS)
    • includes A-D converter
      • provides digital information to reconstruction computer
computer system components
Computer System Components
  • Interfaces to other computers
    • Remote service
    • RIS
    • Archive
    • Web browser
  • Communications hardware
  • Software
    • enables above hardware operation
    • image manipulation
    • scanning control
  • Input / output devices
    • Detectors
    • Printer
  • Central processing units (CPU’s)
  • Array Processor
    • Reconstruction Hardware
computer system
Computer System
  • Receives digital data from DAS
  • Reconstructs cross-sectional image
  • Image display, manipulation, & processing
    • windowing
    • enhancement
    • zoom
    • quantitative measurements
    • multi-planar & 3D reconstruction
image display record storage
Image Display, Record, Storage
  • Display output image
  • Provide permanent hard-copy for
    • radiologist interpretation
    • referring physician
    • archival
  • Facilitate storage / retrieval of digital data
computer image processing
Computer & Image Processing
  • Hardware
    • Special processing architecture
  • Software
processing architecture
Processing Architecture
  • Multi-processing capability
    • scanning
    • reconstructing
    • archiving
  • Pipeline processing architecture
    • various reconstruction steps may be performed by separate processors
  • Parallel processing architecture
    • separate scan, display, & file processors
processing architecture cont
Processing Architecture (cont.)
  • Distributed processing architecture
    • many independent processors
    • each controls specific function
ct software functions
CT Software Functions
  • Control of scanner
    • Gantry tilt
    • scout / axial
    • field of view
    • x-ray technique
    • slices
      • how many
      • thickness
      • overlap
  • Operator console
    • Allows operator to communicate with computer & scanner
    • keyboard
    • touch screen
    • mouse / trackball
ct software functions21
CT Software Functions
  • Control of imaging
    • selection of pre-stored image protocols
    • Selection of reconstruction algorithm
  • Operating System
    • often UNIX
      • multiuser
      • multitasking
    • controls hardware
image display storage recording
Image Display, Storage, & Recording
  • Display
    • CRT or flat panel
      • images in gray shade
      • non-image data in color or B/W
    • often hi-resolution
      • Can display 4-on-1 or zoomed image at full resolution
  • Display processor provides
    • display functions
    • image manipulation
image storage
Image Storage
  • Typical CT image
    • 512 X 512 pixels
    • 8-12 bits deep
      • often stored as 2 bytes / pixel (16 bits / pixel)
  • Multiply image size by # images
image size
Image Size
  • 512 X 512 image = 262144 pixels
  • 262144 pixels X 2 bytes / pixel =524288 bytes per image ~ 512 KB ~ 0.5 MB
image storage cont
Image Storage (cont.)
  • Assume 0.5 Mbytes per image
  • If 100 images / patient
    • 50 Mbytes / patient
  • 25 patients / day X 50 MBytes / patient =1.25 GBytes per day
high capacity image storage
High Capacity Image Storage

Types

Considerations

  • Magnetic disk
  • Magnetic tape
  • Digital videotape
  • Optical disks
  • Optical Tape
  • Capacity
  • Access Speed
  • Rewritable?
  • Size / space
  • Longevity
  • On line?
  • $$$
ct hard copy on laser printer
CT Hard Copy on Laser Printer
  • Stringent quality requirements (images often used for interpretation)
    • broad gray-scale contrast resolution
    • high spatial resolution
  • No film processor required
ct hard copy on laser printer28
CT Hard Copy on Laser Printer
  • Requires special film
    • Film’s spectral sensitivity must match laser
  • Laser types
    • solid state
    • gas (He-Ne)
laser printing
Laser Printing
  • Film exposed by scanning line by line with laser
laser printer features
Laser Printer Features
  • Contains image buffer (computer memory)
  • Buffer stores images in memory until printed
  • Camera prints multiple images on one film
  • Camera can receive & buffer multiple image sources images simultaneously
ct console
CT Console
  • Keyboard
  • Mouse
  • Display
    • CRT
    • Flat panel
    • Touch panel
ct console allows operator to control
CT Console Allows Operator to Control
  • Gantry tilt
  • scanning parameters
    • Slice thickness
    • Spacing
    • Technique
  • image manipulation
    • multiplanar reformatting
    • 3D
    • zoom / pan
ct available automatic control functions
CT Available Automatic Control Functions
  • Archiving
  • Voice instruction to patient
  • Visual instructions to patient
  • Filming protocols
    • Window / level
    • Format (12 on 1 for example)
optional purchases ct hardware
Optional PurchasesCT Hardware
  • Archival systems
  • Independent workstations
    • Physicians
    • 3D
  • Printing
    • Laser
    • Multi-format
ct options
CT Options
  • Bone mineral analysis
  • Dynamic scan
    • rapid sequential scans of single slice
  • Multiplanar reformatting
  • 3D image reconstruction
  • Regional cerebral blood flow analysis
  • CT Angiography
  • Dental CT (surgery planning, implants)
  • Networking
ct room layout
CT Room Layout
  • Gantry
  • Couch
  • Room for
    • Resuscitation team
    • Emergency equipment
    • Stretchers
  • Medical Gasses
  • Shielding
ct room layout37
CT Room Layout
  • Equipment room
    • not always necessary as scanners become smaller
  • Control room
  • Film recording
    • may be combined with control room
purchasing ct specifications
Purchasing CT;Specifications
  • List of Items
    • Major components
    • Optional equipment
  • Major technical features
    • should be measurable
ct specifications who s involved
CT SpecificationsWho’s Involved?
  • Radiologist
  • Technologist
  • Physicist
  • Administrators
technical specifications
Technical Specifications
  • X-ray generator parameters
    • operational parameters
      • maximum kVp
      • kW rating
  • Detector efficiency
  • Reconstruction time
  • Throughput
  • X-ray tube
    • heat capacity
    • cooling rates
ct specifications
CT Specifications
  • Gantry
    • aperture size
    • tilt range
    • laser positioning aids
    • controls
  • Couch
    • strength / weight limits
    • movement characteristics
      • Speed
      • Limits
ct specifications operator s console
CT Specifications;Operator’s Console
  • Display, keyboard, mouse, touch panel characteristics
  • Software design
    • Choice box of available options vs. manual typing
  • Film recording & archival considerations
ct specifications43
CT Specifications
  • Physician’s console & other workstations
    • functions available
    • speed
    • Simultaneity
  • Computer
    • storage requirements
    • CPU
    • networking
ct specifications44
CT Specifications
  • Interfaces
  • PACS hooks & DICOM compatibility
    • Worklist management
      • Pulling patient demographics from RIS
    • Image storage
      • Transfer of images to archive / PACS
computer software ct specifications
Computer SoftwareCT Specifications
  • image reconstruction options
    • FOV
    • filters
  • display options
    • annotation
  • analysis options
    • regions of interest
ct specifications46
CT Specifications
  • Hardcopy devices & interface
    • laser printer
  • Quality control equipment
    • phantoms
    • software
  • Remote Diagnostics
ct specifications47
CT Specifications
  • Acceptance Testing
    • Who performs
    • What tests done
  • Technology Changes
    • “Latest model available at time of delivery”
  • Service
    • Warranty
    • Binding service contract prices
purchasing ct
Purchasing CT
  • Room planning
    • in consultation with equipment vendor
  • Property ownership. Who owns? And when does ownership transfer?
    • service manuals
    • diagnostic software
    • operating system
  • Property ownership dictates hidden software costs & service options
ct specifications training
CT Specifications:Training
  • For whom?
    • Technologists
    • How many?
  • Where?
    • Vendor site
    • On-site
    • Local
  • What’s included
    • Registration
    • Books
    • Travel expenses
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