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RT 255 C Cross Sectional Anatomy

RT 255 C Cross Sectional Anatomy. Week 1 FINAL 4-13-09. Name the Sectional Planes. A. B. C. D. Oblique and Transverse. Used for imaging of heart. Commonly used in MR and sonography. Axial (Transverse) Planes. 1 2 3 4 5 6. Axial Scout. Axial (cross sectional). Sagittal Plane.

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RT 255 C Cross Sectional Anatomy

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  1. RT 255 CCross Sectional Anatomy Week 1 FINAL 4-13-09

  2. Name the Sectional Planes A B C D

  3. Oblique and Transverse Used for imaging of heart. Commonly used in MR and sonography

  4. Axial (Transverse) Planes • 1 • 2 • 3 • 4 • 5 • 6

  5. Axial Scout

  6. Axial (cross sectional)

  7. Sagittal Plane • 1 • 2 • 3

  8. Sagittal Scout

  9. Sagittal

  10. Coronal Plane • 1 • 2 • 3 • 4 • 5

  11. Coronal

  12. Coronal

  13. Name the Imaging Plane

  14. Both Radiation: Why CT vs. Radiography • Superimposition • Contrast Resolution • Less scatter • One exposure

  15. Similar to Radiography • Radiopaque are white • Bone • Prosthesis • Lower density images are gray • Fat • Muscles • Organs • Very low density are black • Air

  16. Hounsfield Units

  17. Fundamentals of CT • Primary data sent to computer • Calculated according • to algorithm • Data assembled into a matrix • Each sectional slice is displaced • on cathode ray tube Cross sectional Tube rotates around patient Detectors measures primary data

  18. Generations of Scanners • First generation • 1 • 2 • 3 • 4 • Second generation • 1 • 2 • 3 • 4

  19. Third Generation • Rotate/ rotate • More than 750 detectors • 1-10 seconds

  20. Fourth Generation • Rotate only • Fixed detectors • More detectors • Higher dose to PT

  21. Technical Aspects • Remnant radiation is collected • 1 • 2 • Electrical signal digitized • Each signal assigned a number • Signals combined to form digital image • Field of View (FOV) determines amount of data to be displayed on monitor

  22. Breakdown of the Digital Image • Array of numbers • 1 • Pixel • 1 • 2 • Voxel • 1 • 2 • 3

  23. System Components • Computer • Operators console • Gantry • Table

  24. Computer • Four basic functions • 1. • 2 • 3 • 4

  25. Data Acquisition • Tech chooses various parameters • 1 • 2 • 3 • 4

  26. Image Reconstruction • Digitizes raw data • Computer performs mathematical computations on a temporary storage system • Host computer has limited storage capacity • Reconstruction takes a few seconds

  27. Long term Storage • After reconstruction it is transferred to another storage medium • Those temporary images on the host computer are archived separately as an independent study that can be retrieved later

  28. Image display • Can be viewed on a video monitor • Tech and doctor can communicate with host computer to view images • Can manipulate images • 1 • 2 • Image resolution lost with reconstruction in other planes

  29. Gantry • Circular • Aperture is the hole PT goes in • Houses • Detector, slip ring, generator and x-ray tube • Tube similar to x-ray tube • Must withstand higher amounts of heat • Can be tilted 30 degrees forward and back

  30. Table • Automated device linked to gantry & computer • Moves in increments • According to protocol • Made of wood or low density carbon composite • Has a weight limit

  31. Control Console • Where the tech controls the scanner • Has a keyboard, display monitor & mouse • Allows tech to control • 1. • 2 • 3 • 4

  32. Image Manipulation • Windowing • 1. • Window width • 1 • 2 • 3 • Window level • 1 • 2

  33. Windowing Window width 400 Window level 35 Window width 2200 Window level 400

  34. Factors Affecting Image Quality • Spatial resolution • Contrast resolution • Noise • Artifacts • Patient factors • Scan times • Scan diameter

  35. Spatial Resolution • What happens to resolution with smaller phosphor crystals in standard film screen systems? • Is a function of pixel size • Smaller: better detail • Thinner slices: increased detail

  36. Ability to distinguish adjacent tissue In CT it is better than in conventional x-ray Less scatter Appears as graininess Low noise is smooth to the eye High noise is blotchy and spotty As noise increases contrast resolution decreases Contrast Resolution and Noise

  37. Artifacts • Streak artifacts • Metallic objects, pacemakers, and prosthesis • High concentration barium

  38. Patient Factors • Motion • Size of patient

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