The effect of Butterworth and Metz reconstruction filters on volume and ejection fraction calculations with 99Tcm gated myocardial SPECT.

This study was carried out to measure the differences produced by change of reconstruction filter in calculations of left-ventricular end-diastolic volumes, end-systolic volumes, stroke-volumes and left-ventricular ejection-fractions from (99)Tc(m) Sestamibi (Bristol-Myers Squibb) gated myocardial perfusion SPECT studies. 30 patients had gated SPECT myocardial perfusion imaging at rest. The acquired projections were separately filtered with two filters, a low-pass filter (Butterworth) and an edge-enhancement filter (Metz). Each study was then further processed to determine left-ventricular end-diastolic volume, end-systolic volume, stroke volume and ejection fraction, and to assess defect size. The results for each patient with the two filters were compared. Calculated end-diastolic volumes, end-systolic volumes and left-ventricular ejection fractions, for each filter, were well correlated. Stroke volumes showed worse correlation. The differences between left-ventricular ejection-fractions, end-diastolic volumes and end-systolic volumes were statistically significant. There was no significant difference in stroke volumes. Ejection fractions were inversely correlated with defect size, but change in ejection fraction due to filter was not. End-diastolic and end-systolic volumes were correlated with defect size, but change in volumes due to filter was not. Thus the results for changes produced by choice of filter are not dependent on defect size. Using different reconstruction pre-filters in gated myocardial perfusion SPECT significantly changes the results of calculations of physiological parameters. Each centre should be consistent in the use of filters as this may affect the clinical consequences of the result.