SPECT

10,983 views

Published on

Lecture notes on SPECT technology for nuclear medicine technologists

Published in: Business, Technology
1 Comment
10 Likes
Statistics
Notes
No Downloads
Views
Total views
10,983
On SlideShare
0
From Embeds
0
Number of Embeds
175
Actions
Shares
0
Downloads
627
Comments
1
Likes
10
Embeds 0
No embeds

No notes for slide

SPECT

  1. 1. SPECT Single Photon Emission Computed Tomography David S. Graff PhD
  2. 2. • Tomography • Filtered Back Projection • Iterative Reconstruction • Quality Control
  3. 3. Tomography τομοσ: a cut or a slice atom: cannot be cut anatomy: a cutting (of the patient)
  4. 4. A Gamma Camera measures the total activity along a line of sight* *Ignoring scatter, attenuation, noise, blurring
  5. 5. We want to know the activity at every point in space, but we measure the sum total attenuation along the line of sight All these systems will look the same
  6. 6. To get more information: measure sums along rays at different angles
  7. 7. To get full information, measure at all angles In order to see a sharp edge, we must have rays parallel to the edge
  8. 8. A sinogram shows all the angles in one slice 0º Head Angle 180º360º Position on detector
  9. 9. • Tomography requires lines of sight through 180º • Filtered Back Projection • Iterative Reconstruction • Quality Control
  10. 10. Collect projections (data) at wide range of angles
  11. 11. Backproject from all projections Edges are lost. Image is fuzzy
  12. 12. Enhance edges of projections (filter) Backproject filtered projections
  13. 13. Filter increases high spatial frequencies and decreases low frequencies
  14. 14. A ramp filter would increase noise too much The filter is modified to reduce high frequencies
  15. 15. Filters combine blurring and ramp to reduce noise a mp Hann R lp/mm
  16. 16. Filtered Back Projection
  17. 17. Object
  18. 18. Projections
  19. 19. Filtered
  20. 20. Backprojected
  21. 21. • Tomography requires lines of sight through 180º • Filtered Back Projection enhances edges and backprojects to reconstruct images • Iterative Reconstruction • Quality Control
  22. 22. Filtered Back Projection assumes • No noise • No attenuation • Perfect resolution • No scatter These assumptions are much worse for SPECT than for CT Iterative algorithms don’t make these assumptions
  23. 23. Collect projections (data) at wide range of angles
  24. 24. Collect projections (data) at wide range of angles
  25. 25. Assume a simple smooth model of patient
  26. 26. Collect projections (data) at wide range of angles Assume a simple smooth model of patient
  27. 27. Project model of patient Include attenuation, resolution, scatter in projection
  28. 28. Collect projections (data) at wide range of angles Assume a simple smooth model of patient Project model of patient (including physics)
  29. 29. Compare projections of model with actual projections Derive a correction for each projection ÷ =
  30. 30. Backproject corrections
  31. 31. Collect projections (data) at wide range of angles Assume a simple smooth model of patient Project model of patient (including physics)
  32. 32. Collect projections (data) at wide range of angles Assume a simple smooth model of patient Project model of patient (including physics) Compare model projections to measured projections Backproject correction to update model
  33. 33. • proper reconstruction requires attenuation and scatter. • How do we know how much attenuation?
  34. 34. SPECT-CT
  35. 35. • Create projections from model of patient • Compare projections with data from patient • Improve model
  36. 36. • Tomography requires lines of sight through 180º • Filtered Back Projection enhances edges and backprojects to reconstruct images • Iterative Reconstruction accounts for noise, attenuation, scatter, resolution. Compare model of patient with data to improve model. • Quality Control
  37. 37. Bullseye artifact results from poor homogeneity
  38. 38. • Tomography requires lines of sight through 180º • Filtered Back Projection enhances edges and backprojects to reconstruct images • Iterative Reconstruction accounts for noise, attenuation, scatter, resolution. Compare model of patient with data to improve model. • Quality Control to verify center of rotation, uniformity, ability to pick up cold spheres and rods
  39. 39. rat heart

×