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Background: The use of acute Tc-99m sestamibi imaging has provided a valuable methodology to asse... more Background: The use of acute Tc-99m sestamibi imaging has provided a valuable methodology to assess myocardium at risk and collateral blood¯ow. Objective: The purpose of this study was to determine the impact of physical, physiologic, and reconstruction factors on the extent and severity of Tc-99m sestamibi images in a porcine model of coronary occlusion and reperfusion. Methods and results: Eleven pigs underwent 40 min of coronary occlusion using a balloon catheter followed by reperfusion. Radiolabeled microspheres were injected during occlusion for blood¯ow determination and 20±30 mCi of Tc-99m sestamibi was injected intravenously for cardiac imaging. Each animal underwent four modes of gamma camera imaging: a cardiac and respiratory gated SPECT study, an ungated SPECT study, a post-mortem SPECT study and an ex-situ study where the heart was sliced into ®ve short axis slices and directly imaged. All animals had extensive wall motion abnormalities at the time of imaging. Myocardial risk area by ex-situ imaging was 32 9% LV and did not signi®cantly change with the addition of a chest cavity and tomographic reconstruction (post-mortem and gated imaging) or cardiac and respiratory motion (ungated imaging). Defect severity was signi®cantly underestimated with the addition of a chest cavity and tomographic reconstruction but was unaltered by cardiac and respiratory motion. Conclusions: The assessment of risk area acutely by SPECT Tc-99m sestamibi imaging is unaected by cardiac motion obviating the necessity for gated imaging. Estimated defect severity (which has been used as a measure of collateral¯ow) is signi®cantly reduced by the chest wall and tomographic acquisition and reconstruction suggesting a role for scatter and attenuation algorithms for this measure.
Background: The use of acute Tc-99m sestamibi imaging has provided a valuable methodology to asse... more Background: The use of acute Tc-99m sestamibi imaging has provided a valuable methodology to assess myocardium at risk and collateral blood¯ow. Objective: The purpose of this study was to determine the impact of physical, physiologic, and reconstruction factors on the extent and severity of Tc-99m sestamibi images in a porcine model of coronary occlusion and reperfusion. Methods and results: Eleven pigs underwent 40 min of coronary occlusion using a balloon catheter followed by reperfusion. Radiolabeled microspheres were injected during occlusion for blood¯ow determination and 20±30 mCi of Tc-99m sestamibi was injected intravenously for cardiac imaging. Each animal underwent four modes of gamma camera imaging: a cardiac and respiratory gated SPECT study, an ungated SPECT study, a post-mortem SPECT study and an ex-situ study where the heart was sliced into ®ve short axis slices and directly imaged. All animals had extensive wall motion abnormalities at the time of imaging. Myocardial risk area by ex-situ imaging was 32 9% LV and did not signi®cantly change with the addition of a chest cavity and tomographic reconstruction (post-mortem and gated imaging) or cardiac and respiratory motion (ungated imaging). Defect severity was signi®cantly underestimated with the addition of a chest cavity and tomographic reconstruction but was unaltered by cardiac and respiratory motion. Conclusions: The assessment of risk area acutely by SPECT Tc-99m sestamibi imaging is unaected by cardiac motion obviating the necessity for gated imaging. Estimated defect severity (which has been used as a measure of collateral¯ow) is signi®cantly reduced by the chest wall and tomographic acquisition and reconstruction suggesting a role for scatter and attenuation algorithms for this measure.