Gated SPECT quantification for myocardial thickness, left ventricular volumes and ejection fraction: methodology and phantom validation

We present a novel counts- and geometry-based method for gated single photon emission computerized tomography (SPECT) quantification to assess myocardial thickness, left ventricular (LV) volumes and ejection fraction (EF). A median search approach and integrated counts strategy were used to determine the endo- and epi-cardial boundaries of the LV. The method was validated using 6 cardiac phantoms with a wide range of wall thicknesses from 6 mm to 16 mm and LV volumes from 33 mL to 128 mL. Tc-99m radioactive isotope with a concentration of 2.5 μCi/mL was injected into the phantoms to simulate normal myocardial perfusion. Two solid plastic inserts were placed in the simulated myocardium of phantoms to mimic dense perfusion defect. Phantom was submerged into a cylindrical tank filled with water to simulate photon attenuation of the human body. A total of 72 image acquisitions were acquired. Images were reconstructed, filtered, reorientated, aligned and computer animated to generate an 11-bin image sequence of simulated gated SPECT. Phantom wall thickness, volumes, and ejection fraction were calculated from the simulated gated SPECT. Correlations between SPECT quantified and actual values of thickness, volume and ejection fraction simulated by the phantoms were excellent. The quantitative results were not significantly affected by the dense perfusion defects simulated. In conclusion, the method developed is feasible to detect the LV boundaries and allows for precise estimation of myocardial thickness, LV volumes and ejection fraction as simulated by phantoms. Further patient validation for the method is warranted for clinical application.