Single-photon emission computed tomography (SPECT)

• SPECT acquisition
  • Elliptical orbit
    • Heart distance changes for each rotation
    • Resolution variations can occur between projections
    • May cause image artifacts in the apex (defect), base and septum (decreased counts)
  • Circular orbit
    • Heart is near the center of the rotation
    • Resolution approximately the same for all projections
    • Some projections further away from body
• Acquisition Parameters
  • Matrix: 64x64 or 128x128 - generally accepted
  • Pixel Size: 6 - 6.5 mm (Typical Extrinsic Resolution)
  • Projections: 32 to 64
  • Time per projection: 25 to 50 seconds
  • 180° or 360° arc obtained
• Solid State SPECT Imaging systems (Digital SPECT)
  • Spectrum Dynamics
    • We have the Veriton now
  • GE Discovery
  • Phantom Data Anger vs Digital Single-photon emission computed tomography (SPECT)
    • Veriton has much better spatial resolution → you can discern many more of the black dots in the figure below with the Veriton
    • 

Who is suitable for SPECT?

• Lower likelihood patients
• Lower risk patients
• No prior history of HFrEF or prior MI
• Able to exercise to an adequate level
• Relatively normal body habitus and BMI
• Previous study had good quality images
• McGhie: “If I’m going to go with pharmacologic, I would prefer PET, but sometimes insurance won’t pay for it. I don’t order very many stress echo or stress SPECT.”

Collimators

• Collimators are the “focusing” device of a SPECT camera
• Made up of holes (usually parallel)
• Exclude photons not traveling parallel to the hole
• Rated by sensitivity and resolution
  • inverse relationship (↑ resolution, ↓ sensitivity)
• See Eric’s slides for diff flavors of collimators