VALIDATION OF A NEW COUNTS-BASED GATED SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY METHOD FOR QUANTIFYING LEFT-VENTRICULAR SYSTOLIC FUNCTION- COMPARISON WITH EQUILIBRIUM RADIONUCLIDE ANGIOGRAPHY

Background. Because myocardial wall thickness is smaller than the spat ial resolution of single photon emission computed tomography (SPECT) i maging, changes in myocardial wall thickness are related to changes in maximum pixel counts via the partial volume effect, allowing for quan tification of regional systolic wall thickening, We have dec eloped a new gated SPECT method for computing the global left ventricular eject ion fraction (LVEF) based entirely on changes in maximum regional myoc ardial counts during systolic contraction, This new method is independ ent of endocardial edge detection or other geometric measurements, Met hods and Results. In 23 patients the gated SPECT method was validated by comparison with radionuclide angiography, The correlation between c omputed LVEFs was excellent (slope = 0.97, r = 0.91), The measurement of LVEF by gated SPECT was highly reproducible, with minimal intraoper ator (slope = 0.97, r = 0.97) or inter-operator (slope = 1.00, r = 0.9 7) variability, Measurements of regional thickening indexes were also reproducible, with a mean intraoperator correlation coefficient of 0.8 9 +/- 0.05 (range 0.79 to 0.95) for the 14 myocardial regions Finally, the measurement of LVEF was not significantly influenced by changes i n reconstruction filter parameters over a range of cutoff frequencies from 0.16 to 0.28., Conclusions. This new counts-based gated SPECT met hod for measuring global left ventricular systolic function correlates well with radionuclide angiography, is highly reproducible,and has th eoretic advantages over geometric methods.