Journal of Nuclear Cardiology Abstracts S115 Volume 6, Number 1, Part 2 Wednesday afternoon, April 21, 1999 54.56 ATTENUATION CORRECTION IMPROVES SPECT QUANTIFICATION USING THE YALE-CQ METHOD. Y.H. Liu, E.P. Ficaro, J.N. Kritzman, J.R. Corbett, F.LTh. Wackers Yale University, New Haven, CT, USA. We investigate the effect of attenuation correction on the accuracy of SPECT quantification using the Yale circumferential quantification (Yale-CQ) method in phantoms. Myocardial perfusion defects of varying extents and severities were simulated in a cardiac phantom using tillable defect inserts. Five defect inserts ranging from 5 to 40 ml were used. Twenty different phantom configurations mimicked 20 myocardial peffusion defect sizes, ranging from 0% to 32% of the simulated left ventricular myocardial volume (LV). A triple-headed SPECT system equipped with a 241Amtransmission line source was used to simultaneously acquire transmission/emission (TCT/ECT) images. Attenuation maps were reconstructed from TCT data using a weighted least-squared algorithm, and attenuation correction emission (AC) images were reconstructed with the attenuation maps using the same reconstruction algorithm. Filtered back projection images without attenuation correction (Non-AC) were also generated from the ECT data. The Yale-CQ method with incorporation of a previously developed scale factor was used for quantification. Quantification of phantom defect sizes using the Yale-CQ method correlated well with actual defect sizes. For Non- AC: 1"=0.98, y= 1.00x-0.15; mean error= -0.15 % LV, 2SD= 4.02 %LV. For AC: 1=1.00, y= 1.04x-0.15; mean error= 0.2% LV, 2SD = 2.48 %LV. Conclusion: application of attenuation correction improves accuracy of SPECT quantification using the Yale-CQ method. 54.58 COMPARATIVE ACCURACY OF QUANTIFICATION OF Tl-20'l AND Tc-99m SPECT DEFECTS USING THE YALE-CQ METHOD IN PHANTOMS S.Kirac, Y.-H.Liu, F.J.Th.Wackers.Yale University, New Haven, CT The Yale-CQ SPECT quantification program, using an empirically derived correction factor (CF), provides accurate and reproducible quantification of defect size using Tc-99m filled phantoms. We compared the accuracy for quantification of defect size using Tc-99m and T1-201 filled phantoms. SPECT imaging was performed on a cardiac phantom using multiple tillable inserts to simulate "defects" of various extent (0 to 32% of phantom volume) and severity (inserts filled with Tc-99m and T1-201 dilutions ranging from 0 to 100% of normal). 70 different phantom configurations were created by combin- ing 23 defect extents and anterior and inferior Iocations. 140 SPECT images were acquired using the same triple-head gamma camera. After using standard reconstruction software without attenuation correction, defects were quantified and expressed as % of phantom volume using the Yale-CQ program and correction factor. Mean reconstructed T1- 201 SPECT defect size was significantly smaller than Tc-99m SPECT size (6.1+0.9% vs 8.3+1.1%, p<0.001) and also than actual mean phantom defect size (6.1+0.9% vs 9.5+1.1%, p<0.001). Overall TI-201 SPECT defect sizes correlated well with actual defect size:r=0.92, but the regression slope showed a systematic underesti- mation: y= 0.72x-0.76. Bland-Airman analysis of agreement revealed underestimation of T1-201 defect size over the entire range of defect sizes with a mean difference 3.4% and 2SD 7.5%. Generation of normal T1-201 phantom database did not improve accuracy, however the addition of a T1-201 specific CF significantly improved correla- tion with Tc-99m defects (r=0.95, y= 1.04x-0.84) and with actual defect size (r=0.94, y=0.98x-1.52). Conclusion: Accurate quantifica- tion of TI-201 and Tc-99m SPECT defect sizes requires radiotracer- specific normal data files and correction factors. 54.57 ACCURACY AND REPRODUCIBILITY OF QUANTIFICATION OF SPECT DEFECTS USING THE YALE-CQ METHOD: VALIDATION IN PHANTOMS. S.Kirac, Y.H.Liu, F.J.Th.Wackers, Yale University. New Haven, CT The Yale-CQ software for quantification of SPECT images is based upon quantification of myocardial perfusion defects using circumfer- ential profiles and normal data files. In a pilot study, an empirical correction factor was derived to compensate for systemic underesti- mation of defect size. In this study, the Yale-CQ program with cor- rection factor was validated in a cardiac phantom with 5 tillable inserts ("defects") of different volumes, filled with 7 concentrations of Tc- 99m. A total of 30 different phantom configurations, simulating defects of varying extent and severity by combining different volumes, concentrations and locations, were imaged using a different triple-head SPECT camera than used in the pilot study. After back projection, short and long axis slices were generated using standard reconstruction software without attenuation correction. Defects were quantified and expressed as % of phantom volume using the Yale-CQ program and correction factor. Phantom SPECT defect sizes correlated well with actual defect sizes: r=0,98, y=0.98x+0.84. Bland-Altman analysis of agreement revealed good accuracy over the entire range of defect sizes with a mean difference of 0.7%, and 2 SD of 3.8%. Reproducibility with quantification in the pilot study by was also excellent with a mean difference 0.5% and 2 SD of 3.0%. Conclusion: The Yale-CQ SPECT quantification program, using an empirically derived correction factor, provides accurate and reproducible quantification of phantom defects over a wide range of defect sizes, when acquired on different gamma camera systems. 54.59 CRITICAL EVALUATION OF A SIMULTANEOUS AQUISITION DUAL TL-201/SESTAMIBI IMAGING PROTOCOL IN PATIENTS WITH KNOWN CAD James A. Case, Timothy M. Bateman, Kelly A. Moutray, S. James Cullom, James H. O'Keefe. Cardiovascular Consultants, P.C., Kansas City, Missouri, USA A recently reported simultaneous acquisition dual isotope SPECT myocardial perfusion protocol demonstrated high concordance between standard sequential (SEQ) T1-201/MIBI imaging and simultaneous (SIM) T1-201/MIBI. However, this study included pts with a normal scan. To better understand SIM's capabilities, we assessed it specifically in 20 pts with known CAD. The dosage protocol was 4.5 mCi TI-201 and 9 mCi MIBI. Data were acquired using a Prism3000 camera, 30 angles (180°), LEGP collimation, 4 acquisition energy windows. Patients were imaged 60 minutes after resting T1- 201 injection and 30 minutes after peak-stress MIBI injection. Down scatter corrected SIM images were compared to SEQ images using blinded consensus interpretation by 3 observers, and a 20-segment model 0=normal to 3=severely abnormal Segmental concordance (normal, ischemic, and infarcted) was 86% (343/400). By coronary territory, condordances were 90%, 80% and 70% for the LAD, LCx, and RCA respectively. 95% (6/133) of abnormal resting segments differed by 1 pt or less, compared with 92% (15/183) for repeat scoring of the abnormal stress segments (p=ns). Conclusion:This simultaneous dual isotope protocol including scatter subtraction, provides results indistinguishable from conventional sequential dual isotope imaging. W E D N E S D A Y P M A P R I L 21