IMAGE-ENHANCEMENT OF SEVERELY HYPOPERFUSED MYOCARDIA FOR COMPUTATION OF TOMOGRAPHIC EJECTION FRACTION

Ejection fractions computed from Tc-99m-sestamibi myocardial perfusion gated tomograms have demonstrated a high degree of accuracy and repro ducibility. Although automated algorithms appear to provide reasonable endocardial outlines for patients over a broad spectrum of cardiac di seases, in cases of severe hypoperfusion, it is necessary to manually adjust contrast and brightness to judge whether borders are correct or must be altered, Methods: Midventricular horizontal and vertical long axis gated tomograms were generated for 116 studies chosen on the bas is of extensive, severe myocardial perfusion defects. Automated softwa re transformed cinematic tomograms into images demonstrating uniform a ppearance of the myocardium throughout the cardiac cycle. Transformed images were introduced to edge detection algorithms for subsequent cal culation of ventricular volumes and ejection fractions, Results: Linea r regression analysis demonstrated excellent intraobserver reproducibi lity for ejection fractions (r = 0.95) and volumes (r = 0.98), There w as also good agreement of ejection fractions (r = 0.86) and volumes (r = 0.94) with values derived from an expert's manual drawings, In a su bgroup of 22 patients, automated ejection fractions from transformed i mages demonstrated better agreement with independent first-pass values (r = 0.90) than did manual measurements derived from original data (r = 0.85), Conclusion: Image enhancement algorithms succeeded in provid ing accurate, reproducible gated SPECT ejection fractions in the most difficult class of patients exhibiting severe hypoperfusion.