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Seeram: Components of a CT Scanner

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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Seeram: Components of a CT Scanner

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  1. CT Seeram: Components of a CT Scanner

  2. Major Components • Scanner room • Imaging system • Generator (?) • Electronics Room • Power • Computer (?) • Generator (?) • Operator’s Area • Display / recording / storage • Computer (?)

  3. 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

  4. Gantry Provides Structural Framework for • collimators • filters • Detectors / electronics

  5. Gantry Size Must Accommodate • patients • size of room • Truck transport to hospital The gantry is pre-assembled at the factory

  6. Gantry Size Must Accommodate • Transport within hospital • hallways • doors • elevators • Typical weight: 3500 lb.

  7. Special Clinical Gantry Concerns • Patient aperture • Tilt range • Cooling of • electrical components • x-ray tube

  8. Patient Couch • Vertical travel • minimum height for stretcher transfer • Horizontal travel • reduces need for re-positioning patient • accuracy

  9. Patient Couch • Weight capacity • Strength • cantilevered • Rigidity

  10. Patient Couch Requirements • Safe for patients • Easy to clean • Radiolucency • Speed • Pretty? • Siemens offerscolors

  11. 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

  12. Imaging System Components • X-ray tube • Generator • supplies power to x-ray tube • filament • high voltage • Collimators • restricts beam to slice of interest

  13. 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

  14. 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

  15. Computer System • Receives digital data from DAS • Reconstructs cross-sectional image • Image display, manipulation, & processing • windowing • enhancement • zoom • quantitative measurements • multi-planar & 3D reconstruction

  16. Image Display, Record, Storage • Display output image • Provide permanent hard-copy for • radiologist interpretation • referring physician • archival • Facilitate storage / retrieval of digital data

  17. Computer & Image Processing • Hardware • Special processing architecture • Software

  18. 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

  19. Processing Architecture (cont.) • Distributed processing architecture • many independent processors • each controls specific function

  20. 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

  21. CT Software Functions • Control of imaging • selection of pre-stored image protocols • Selection of reconstruction algorithm • Operating System • often UNIX • multiuser • multitasking • controls hardware

  22. 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

  23. 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

  24. Image Size • 512 X 512 image = 262144 pixels • 262144 pixels X 2 bytes / pixel =524288 bytes per image ~ 512 KB ~ 0.5 MB

  25. 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

  26. 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? • $$$

  27. 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

  28. CT Hard Copy on Laser Printer • Requires special film • Film’s spectral sensitivity must match laser • Laser types • solid state • gas (He-Ne)

  29. Laser Printing • Film exposed by scanning line by line with laser

  30. 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

  31. CT Console • Keyboard • Mouse • Display • CRT • Flat panel • Touch panel

  32. CT Console Allows Operator to Control • Gantry tilt • scanning parameters • Slice thickness • Spacing • Technique • image manipulation • multiplanar reformatting • 3D • zoom / pan

  33. CT Available Automatic Control Functions • Archiving • Voice instruction to patient • Visual instructions to patient • Filming protocols • Window / level • Format (12 on 1 for example)

  34. Optional PurchasesCT Hardware • Archival systems • Independent workstations • Physicians • 3D • Printing • Laser • Multi-format

  35. 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

  36. CT Room Layout • Gantry • Couch • Room for • Resuscitation team • Emergency equipment • Stretchers • Medical Gasses • Shielding

  37. CT Room Layout • Equipment room • not always necessary as scanners become smaller • Control room • Film recording • may be combined with control room

  38. Purchasing CT;Specifications • List of Items • Major components • Optional equipment • Major technical features • should be measurable

  39. CT SpecificationsWho’s Involved? • Radiologist • Technologist • Physicist • Administrators

  40. Technical Specifications • X-ray generator parameters • operational parameters • maximum kVp • kW rating • Detector efficiency • Reconstruction time • Throughput • X-ray tube • heat capacity • cooling rates

  41. CT Specifications • Gantry • aperture size • tilt range • laser positioning aids • controls • Couch • strength / weight limits • movement characteristics • Speed • Limits

  42. 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

  43. CT Specifications • Physician’s console & other workstations • functions available • speed • Simultaneity • Computer • storage requirements • CPU • networking

  44. CT Specifications • Interfaces • PACS hooks & DICOM compatibility • Worklist management • Pulling patient demographics from RIS • Image storage • Transfer of images to archive / PACS

  45. Computer SoftwareCT Specifications • image reconstruction options • FOV • filters • display options • annotation • analysis options • regions of interest

  46. CT Specifications • Hardcopy devices & interface • laser printer • Quality control equipment • phantoms • software • Remote Diagnostics

  47. CT Specifications • Acceptance Testing • Who performs • What tests done • Technology Changes • “Latest model available at time of delivery” • Service • Warranty • Binding service contract prices

  48. 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

  49. 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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