Abstract for presentation at 38th Annual Scientific Meeting of the Australian and New Zealand Society of Nuclear Medicine 2008

Quantitative SPECT Reconstruction using CT - Derived Corrections

  • Miss Kathy Willowson, Institute of Medical Physics, University of Sydney and Department of Nuclear Medicine, Royal North Shore Hospital, Australia
  • A/Prof Dale Bailey, Department of Nuclear Medicine, Royal North Shore Hospital and Institute of Medical Physics, University of Sydney, Australia
  • Prof Clive Baldock, Institute of Medical Physics, University of Sydney, Australia

    • Aim: To implement CT-based quantitative SPECT using Transmission Dependent Scatter Correction (TDSC) in conjunction with corrections for attenuation, dead time and partial volume effect (PVE).
    Method: Using the CT data from a SPECT/CT scanner, an attenuation map is first created and used to perform TDSC prior to reconstruction. The scatter corrected data are reconstructed using OSEM with attenuation correction, with subsequent correction for dead time. The camera sensitivity is used to transform pixel values to units of activity. The system’s recovery coefficient has been modelled to allow PVE corrections where necessary. Quantitative evaluation was performed with (a) a cylindrical phantom filled with 316MBq of Tc99m, and (b) an anthropomorphic torso phantom, containing concentrations of 481kBq.ml-1 in the liver region and 270kBq.ml-1 in the inner chamber of the cardiac insert. Further evaluation was performed comparing corrected clinical lung ventilation/perfusion SPECT/CT studies to the calibrated injected dose of [Tc99m]-MAA.
    Results: The reconstructions from the cylindrical phantom yielded total activity within 1% of the true activity. Several regions of interest from the anthropomorphic phantom study produced average concentrations in the liver and cardiac chamber within 2% and 4% of the true concentrations, respectively. Analyzing 12 patient lung ventilation/perfusion studies yielded an average absolute difference between calculated and true activities of 4%, accurate to within a maximum error of ~10%.
    Conclusion: The above results confirm the accuracy of the developed CT based quantitative method. The method will now be extended to include other radiopharmaceuticals.

    Conference Organiser - ICMS Pty Ltd