Digital Techniques For Myocardial Perfusion Spect

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SPECT Techniques for data acquisition, processing and display in Nuclear Cardiology

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Digital Techniques For Myocardial Perfusion Spect

  1. 1. Digital Techniques for Myocardial Perfusion SPECT Dr. Muhammad Ayub Diplomate Certification Board of Nuclear Cardiology Diplomate Certification Board of Cardiovascular CT Punjab Institute of Cardiology, Lahore
  2. 2. SINGLEPHOTONEMISSIONCOMPUTEDTOMOGRAPHY A Modern SPECT Gamma Camera
  3. 3. SPECT Equipment• Camera – Single Detector – Multi detector• Analog to digital converter• Computer interface – Data storage – Data processing – Display
  4. 4. Gamma Camera• Gantry Display• Camera Heads PHA – Collimator x y – Scintillation Crystal Lead Shield – Photo multiplier tubes Pulse Processing Electronics – PHA – ADC PMTs Crystal Collimator
  5. 5. Cardiac SPECT Acquisition • Gamma camera with 1 or 2 heads (90 angle) • 180 rotation • 32 steps (16 per head if 2) • Planar projection acquisition at each stepStep and shoot acquisition
  6. 6. Workstation• Types – Unix Workstations – PCs, Macs• Storage• Memory• Graphics• Software
  7. 7. PHA
  8. 8. Tomographic Acquisition• Matrix• Angular Range• Angular Steps• Time per Step• Gated Vs non gated acquisition• Continuous Vs Step and Shoot acquisition
  9. 9. Tomographic Acquisition• Matrix – 64 x 64 Standard – 128 x 128
  10. 10. Tomographic Acquisition• Angular Range RAO 135 – 180 degrees – 360 degrees 215 LPO
  11. 11. Tomographic AcquisitionAngular Steps – 3 degrees Recommended for Tc Studies – 6 degrees Recommended for Tl Studies – 12 degrees Not Recommended
  12. 12. Image Acquisition• Orbit – Circular Standard – Non-circular Optional
  13. 13. Tomographic Acquisition Gated SPECT
  14. 14. Technical Considerations• QC – Energy – Uniformity – Linearity – COR
  15. 15. Problems• Motion Artifacts• COR defects• Soft tissue attenuation• Foreign Objects
  16. 16. Image Processing• Filtered Back projection• Filtering• Iterative Reconstruction• Corrections – Attenuation Correction – Scatter Correction
  17. 17. Theory of Back Projection 1 0 22.5 Imaging a point source 45 • Rotating camera headPoint • Step and shoot at 8source 67.5 angles over 180 90 • Only photons  to camera face are detected • Planar ‘projection’ 180 acquisition at each step
  18. 18. Back Projection of 4 Ray Sums Camera angle x 0° 22.5° Depth in 45° transaxial slice 67.5° Transaxial Plane
  19. 19. Filtering• Pre filtering• 3D Post Filtering• Types – Low pass – Metz – Wiener – Band
  20. 20. Types of Filters Used Magnitude•Ramp filter –Always applied –Removes star-burst effect (good!) –Amplifies high frequency noise (bad!) Frequency•Smoothing filter 1.0 –E.g. Hanning or Butterworth –Smooths image (removes noise 0.0 generated by ramp filter)
  21. 21. Pre filtration
  22. 22. 3 D Post FilterLow pass Filter
  23. 23. Metz Filter
  24. 24. Wiener Filter
  25. 25. Band Pass Filter
  26. 26. Filter Example: ButterworthButterworth[Cutoff = 0.3 Order =5] Filtered Raw image Filter Reconstructed slice Too smooth!
  27. 27. Filter Example: ButterworthButterworth[Cutoff = 0.5 Order =5] Filter Filtered Raw Reconstructed image slice Good quality
  28. 28. Image Reconstruction• Short Axis• Vertical Long Slices• Horizontal Long Slices• Slice Thickness
  29. 29. Transverse Reconstruction
  30. 30. The Iterative Loop Flow chart of a loop in iterative process• Initial estimate – e.g. uniform object• Compare forward projection to real projections• Perform several iterations: – Each time, alter original transverse estimate until pseudo- projections converge with real ones.
  31. 31. New Methods WIDE BEAM RECONSTUCTION Sharir, T. et al. J Am Coll Cardiol Img 2008;1:156-163Copyright ©2008 American College of Cardiology Foundation. Restrictions may apply.
  32. 32. Oblique Reformatting
  33. 33. Image Display• Cardiac Stress Rest Display Format• Colored and Black & White Display• 3D display• Cine Display• Animation
  34. 34. The use of different colors (as opposed to intensities) in a translationtable may produce pseudocontouring: the false perception of an edgewhen none, in fact, is present. An image thatshows a linear transition from maximal to minimal counts is shownusing 3 different color tables. The steady transition of the image isshown most faithfully by the gray scale.
  35. 35. Visual scoring 2 1 100% Score 4 normal 100 - 70% 04 70 3 2 3 mild 70 - 50% 50 14 2 moderate 50 - 30% 4 30 4 1 severe 30 - 10% 2 104 0 0 absent 10 - 0%
  36. 36. Normal Scan
  37. 37. 3D Display
  38. 38. Quantitative Display• Bulls Eye Reconstruction – Cequal – PTQ map• Quantitative Gated SPECT Display
  39. 39. PTQ Map
  40. 40. Segmental analysis short-axis V-long axis 16 9 8 1 17 7 2 15 10 18 6 3 14 11 19 5 4 13 12 20 apical basalA four-point 0 : normal uptakegrading system 1 : slightly decreased uptake 2 : severely decreased uptake 3 : no uptake ; defect
  41. 41. Quantitative Gated SPECT
  42. 42. QGS
  43. 43. Thank You

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