title: Myocardial perfusion imaging with a combined x-ray CT and SPECT system.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: UCSF Physics Research Laboratory, Department of Radiology, University of California San Francisco 94080, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kalki
authors.forename: S C
authors.initials: SC
authors.lastname: Blankespoor
authors.forename: J K
authors.initials: JK
authors.lastname: Brown
authors.forename: B H
authors.initials: BH
authors.lastname: Hasegawa
authors.forename: M W
authors.initials: MW
authors.lastname: Dae
authors.forename: M
authors.initials: M
authors.lastname: Chin
authors.forename: C
authors.initials: C
authors.lastname: Stillson
mesh_terms: D000465:Algorithms; D000818:Animals; D006321:Heart / Q000000981:diagnostic imaging*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D019275:Radiopharmaceuticals; D013552:Swine; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi