A new algorithm for the quantitation of myocardial perfusion SPECT. I: Technical principles and reproducibility

We have developed a new, completely automatic 3-dimensional softwareapproachto quantitativeperfusionSPECT.The main featuresof the softwareare myocardialsamplingbasedon an ellipsoidmodel;use of the entirecountprofilebetweenthe endocardial andepicardial surfaces; independence of thealgo rithm from myocardial shape, size, and orientation and establish mentof a standard3-dimensional point-to-pointcorrespondence amongall sampledmyocardialregions;automaticgenerationof quantitativemeasurements and 5-pointsemiquantitative scores for eachof 20 myocardialsegmentsandautomaticderivationof summed perfusion scores; and automatic generation of normal limitsfor any givenpatientpopulation on the basisof data fractionally normalized to minimize hotspotartifacts. Methods: The new algorithmwas tested on the tomographic images of 420 patientsstudiedwitha rest @°1Tl (111—167 MBq,35s/projection)— stress @“Tc-sestamibi (925—1480 MBq,25 s/projection) separate dual-isotope protocol on a single-detectorcamera, a dual detector 90° camera,anda triple-detector camera.Results:The algorithmwassuccessfulin 397of 420patients(94.5%)and816 of 840 image datasets (97.1%), with a statisticallysignificant differencebetweenthe successratesof the @°1Tl images(399/ 420, or 95.0%) and the @Tc images (417/420, or 99.3%; P < 0.001). Algorithmfailure was caused by extracardiacuptake (10/24,or 41.7%)or inaccurateidentificationof the valveplane becauseof low countstatistics(14/24, or 58.3%) and was obviated by simply limiting the image volume in which the softwareoperates.Reproducibility of measurements of summed perfusion scores (r = 0.999 and I for stress and rest, respec tively),globaldefectextent(r = 0.999and 1 for stressand rest, respectively), and segmental perfusion scores (exact agreement = 99.9%,K 0.998forstressand0.997forrest)was extremely high.Conclusion:Automatic 3-dimensional quantita tionofperfusion from@°1Tl and @mTc.sestamibi images isfeasible andreproducible. Thedescribedsoftware,becauseit is basedon the same samplingschemeused for gated SPECTanalysis, ensures intrinsicallyperfect registration of quantitative perfusion withquantitative regional wall motionand thickening information, if gatedSPECTis used.