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Myocardial perfusion imaging with a combined x-ray CT and SPECT system
K Kalki1, S C Blankespoor, J K Brown
1UCSF Physics Research Laboratory, Department of Radiology, University of California San Francisco 94080, USA.
Unlabelled:
We evaluated a novel combined x-ray CT and SPECT medical imaging system for quantitative in vivo measurements of 99mTc-sestamibi uptake in an animal model of myocardial perfusion.
Methods:
Correlated emission-transmission myocardial images were obtained from 7- to 10-kg pigs. The x-ray CT image was used to generate an object-specific attenuation map that was incorporated into an iterative ML-EM algorithm for reconstruction and attenuation correction of the coregistered SPECT images. The pixel intensities in the SPECT images were calibrated in units of radionuclide concentrations (MBq/g), then compared against in vitro 99mTc activity concentration measured from the excised myocardium. In addition, the coregistered x-ray CT image was used to determine anatomical boundaries for quantitation of myocardial regions with low perfusion.
Results:
The accuracy of the quantitative measurement of in vivo activity concentration in the porcine myocardium was improved by object-specific attenuation correction. However, an additional correction for partial volume errors was required to retrieve the true activity concentration from the reconstructed SPECT images.
Conclusion:
Accurate absolute SPECT quantitation required object-specific correction for attenuation and partial volume effects. Additional anatomical information from the x-ray CT image was helpful in defining regions of interest for quantitation of the SPECT images.