A potential source of false negative finding in gated myocardial perfusion SPECT

Introduction: In theory, the generation of the standard ungated data set is just summation of all the intervals for each projection from the gated data set. The reconstruction strategy employed may be stream-lined to reduce the computational demands of gated SPECT reconstruction and, thus, may be a potential source of false negative findings in the ungated qualitative image set. Methodology: The phantom phase investigation employed an experimental repeat-measures design while the clinical phase employed a retrospective repeat-measures design. A perspex cardiac phantom with defect insert and 45 rest/stress patient files were examined quantitatively with CEqual quantitation software for reconstructed ungated data and summed data post reconstruction of the gated data. For each individual study, the two methods of reconstruction were performed simultaneously as a 'batch' to ensure identical reconstruction parameters and slice orientation. Results: Compared to data reconstructed as ungated files, summation of reconstructed gated files results in; a decrease in defect extent by 1.9% of myocardial area or a 20.4% reduction in defect area, a decrease in defect severity by 68.9 standard deviations for the entire myocardium or a 13.6% decrease in severity for the defect area, a decrease in left ventricular lumen by 19.2%, an increase in total heart diameter by 9.8% and an increase in wall thickness by 32.3%. Conclusion: Not only does the generation of perfusion data via summation of the reconstructed gated data fail to provide the anticipated relief in computational demands of gated SPECT reconstruction, but it also introduces potential false negative results for coronary artery disease.