CT COMPONENTS

It's all about components of computed tomography....

1. Computed Tomography Components

2. Three Major Systems Imaging System Computer System Image Display/Recording/Storage System Each system in a separate room

3. Major Components Scanner room Imaging system gantry assembly patient table Computer/Electronics Room Power Computer Generator Operator’s Area Display / recording / storage Computer

4. Imaging System Propose: To Produce x-ray Shapes & filters (hardens) beam Detect (measure) radiation passing through patient Convert transmitted photons – Provides digital intensity data to computer

5. Imaging System Components: X-ray Beam slice thickness, restricts beam Protect Patient, Uniform beam-Detector X-ray tube Generator Collimator Filter Detector capture photon, convert to elect.signal Detector electronics (DAS) convert to digital

6. Gantry Assembly All previous components in Gantry Assembly Moving Frame, Tilt, Gantry aperture Rotational components including slip ring , positioning laser lights,

7. Gantry: Components X-ray tube high heat capacity modern tubes very large & heavy external cooling (oil heat exchanger) high speed rotation of the anode Heat units: heat capacity of 3.5 to 5 million heat units (MHU) focal spot size of an x-ray tube is determined by the size of the filament and cathode which is determined by the manufacturer

8. Gantry: Components Generator, inside gantry supplies power to x-ray tube filament high voltage Different power 30-60Kilowatts Allowing range of exposure techniques: 80,100,120,130,and 140kV and 30,50,65,100,125,150,175, and 200,mA

9. Gantry: Components Collimators Tube/Source collimators: restricts beam to slice of interest Pre-patient collimators: maintain the width of the beam as it travels toward the patient Post-patient/Pre-detector collimators: below patient and above detector proper beam width at detector and reduce no. of scattered photons at detector

10. Gantry: Components Filter protects patient from low-energy photons provides a beam closer to mono-energetic provides a more uniform beam (hardening) Mathematical filtration: bone/tissue algorithms (recons. Process) Inherent tube filtration Filters made of aluminum or Teflon; to shape beam-low energy photons and scatter

11. Gantry Components Detector = image receptor beam travels through patient and attenuates by the anatomical structures it passes through Job: collect attenuated photon energy and convert it to electrical signal, which will then be converted to a digital signal for computer reconstruction

12. Detectors Crystal or ionizing gas When struck by x-ray photon , produces light or electrical energy Two types : scintillation or solid state and xenon gas detectors Scintillation detectors- uses a crystal that fluoresces when struck by x-ray photon which produces light energy A photodiode, attached to scintillation portion, transforms light energy into electrical or analog energy Strength of the detector signal is proportional to number of attenuated photons that are successfully converted to light energy and then to an electrical signal

13. A Note on Detectors Detector: single element of detector array, produces electrical/light signal as a response to x-rays Detector array : total number of detectors that a CT system utilizes for collecting attenuated information A Ray : path that an x-ray beam travels from tube to a single detector Detector reads each ray and measures resultant beam attenuation

14. Cont. Ray Sum: attenuation measurement of each ray Projection (view) : a complete set of ray sums – It takes many projections to create a computed tomography image

15. Gantry Components Detector electronics, data acquisition system (DAS) Receives weak signal form detector includes A-D converter Amplification provides digital information to reconstruction computer

16. Gantry Requirements Patient size size of room Patient aperture from 50-85cm Tilt range +/-30°

17. Patient Couch Strong, safe, and hygienic, made of radiolucent material Couch top: carbon fiber composite, low absorption Pedestal: mechanical and electrical components

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

19. Patient Couch Requirements Radiolucent Easy to clean Weight limits: 450lb Total travel: 180cm Accuracy: +/- 0.25mm Speed: 25mm/sec

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

21. Computer System Components Input / output devices Detectors Printer Central processing units (CPU’s) Array Processor Reconstruction Hardware Interfaces to other computers Remote service RIS Archive Web browser Communications hardware Software enables above hardware operation image manipulation scanning control

22. Computer System Processing architecture Hardware Software

23. Processing Architecture Capable of Multi-processing – Scanning, reconstructing, archiving Three Types: Pipeline processing architecture various reconstruction steps may be performed by separate processors Very fast image reconstruction, after scanning image can be viewed Overlapping moving data into pipe

24. Processing Architecture (cont.) Parallel processing architecture 3 multi-task computers coupled More than one CPU to execute program Coordination, dividing program instructions separate scan, display, & file processors Distributed processing architecture many independent processors each controls specific function each runs a different activity

25. CT Software Functions Operator console Allows operator to communicate with computer & scanner keyboard touch screen mouse / trackball Control of scanner Gantry tilt scout / axial field of view x-ray technique slices how many thickness overlap

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

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

28. Image Display Display CRT or flat panel images in gray shade non-image data in color or often hi-resolution Can display 4-on-1 or zoomed image at full resolution Display processor provides display functions image manipulation

29. Image Storage Storage: 512x512x2 bytes (16bits) deep Requires 0.5MB storage 1 Examination= 50 images, 25MB 50/day = 1.25GB

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

31. High Capacity Image Storage Magnetic disk Magnetic tape Digital videotape Optical disks Optical Tape Capacity Access Speed Rewritable? Size / space $$ Types Considerations

32. CT Hard Copy on Laser Printer Requirements for hard copy broad gray-scale contrast resolution high spatial resolution Two types : Solid state and gas lasers

33. Laser Printing Unexposed film will move to exposure region, film exposed by scanning line by line with laser Producing a latent image

34. CT Console Keyboard Alphanumeric, special function keys, trackball, windowing controls Display CRT Flat panel Touch panel

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

36. Control Functions Archiving Voice instruction to patient Visual instructions to patient Filming protocols Window / level (for contrast) Format (12 on 1 for example)

37. Options and Accessories Hardware: Archival systems Independent workstations Physicians 3D Printing Laser Multi-format

38. CT Options Software: 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

39. Accessories Support – immobilization Pads, wedges, head rests, straps, mattress, knee support pad

40. CT Room Layout Scanning Room: Gantry, Patient Couch Room for Resuscitation team Emergency equipment Stretchers Medical Gasses Shielding

41. CT Room Layout Equipment room/Computer – Host computer and computing equipment Control room – Control console, film recording equipment

42. Purchasing Specifications List of Items Major components Optional equipment Major technical features should be measurable

43. CT Specifications Who’s Involved? Radiologist Technologist Physicist Biomedical Engineer IT Engineering Management (new)

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

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

46. 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

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

48. CT Specifications Interfaces PACS hooks & DICOM ( digital imaging and communication in medicine ) compatibility Worklist management Pulling patient demographics from RIS ( radiology information system ) Image storage Transfer of images to archive / PACS

49. Computer Software CT Specifications image reconstruction options FOV filters display options A nnotation ( syntactic metadata) analysis options regions of interest

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

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

52. Room Requirements Scanner Room Console Area Computer Room Design

53. CT Specifications Training For whom? Technologists How many? Where? Vendor site On-site Local What’s included Registration Books Travel expenses