Digital Techniques For Myocardial Perfusion Spect
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SPECT Techniques for data acquisition, processing and display in Nuclear Cardiology

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

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Digital Techniques For Myocardial Perfusion Spect Presentation Transcript

  • 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. SINGLEPHOTONEMISSIONCOMPUTEDTOMOGRAPHY A Modern SPECT Gamma Camera
  • 3. SPECT Equipment• Camera – Single Detector – Multi detector• Analog to digital converter• Computer interface – Data storage – Data processing – Display
  • 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. 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. Workstation• Types – Unix Workstations – PCs, Macs• Storage• Memory• Graphics• Software
  • 7. PHA
  • 8. Tomographic Acquisition• Matrix• Angular Range• Angular Steps• Time per Step• Gated Vs non gated acquisition• Continuous Vs Step and Shoot acquisition
  • 9. Tomographic Acquisition• Matrix – 64 x 64 Standard – 128 x 128
  • 10. Tomographic Acquisition• Angular Range RAO 135 – 180 degrees – 360 degrees 215 LPO
  • 11. Tomographic AcquisitionAngular Steps – 3 degrees Recommended for Tc Studies – 6 degrees Recommended for Tl Studies – 12 degrees Not Recommended
  • 12. Image Acquisition• Orbit – Circular Standard – Non-circular Optional
  • 13. Tomographic Acquisition Gated SPECT
  • 14. Technical Considerations• QC – Energy – Uniformity – Linearity – COR
  • 15. Problems• Motion Artifacts• COR defects• Soft tissue attenuation• Foreign Objects
  • 16. Image Processing• Filtered Back projection• Filtering• Iterative Reconstruction• Corrections – Attenuation Correction – Scatter Correction
  • 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. Back Projection of 4 Ray Sums Camera angle x 0° 22.5° Depth in 45° transaxial slice 67.5° Transaxial Plane
  • 19. Filtering• Pre filtering• 3D Post Filtering• Types – Low pass – Metz – Wiener – Band
  • 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. Pre filtration
  • 22. 3 D Post FilterLow pass Filter
  • 23. Metz Filter
  • 24. Wiener Filter
  • 25. Band Pass Filter
  • 26. Filter Example: ButterworthButterworth[Cutoff = 0.3 Order =5] Filtered Raw image Filter Reconstructed slice Too smooth!
  • 27. Filter Example: ButterworthButterworth[Cutoff = 0.5 Order =5] Filter Filtered Raw Reconstructed image slice Good quality
  • 28. Image Reconstruction• Short Axis• Vertical Long Slices• Horizontal Long Slices• Slice Thickness
  • 29. Transverse Reconstruction
  • 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. 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. Oblique Reformatting
  • 33. Image Display• Cardiac Stress Rest Display Format• Colored and Black & White Display• 3D display• Cine Display• Animation
  • 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. 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. Normal Scan
  • 37. 3D Display
  • 38. Quantitative Display• Bulls Eye Reconstruction – Cequal – PTQ map• Quantitative Gated SPECT Display
  • 39. PTQ Map
  • 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. Quantitative Gated SPECT
  • 42. QGS
  • 43. Thank You