A geometry- and count-based method for gated SPECT quantification of myocardial thickness, left ventricular volume, and ejection fraction

We present a novel geometry and count-based method for gated single photon emission computerized tomography (SPECT) quantification to assess myocardial thickness, left ventricular (LV) volume and ejection fraction (EF). A median search associated with an integrated counts strategy was used to determine the endocardial and epicardial boundaries of the LV. The method was validated using six cardiac phantoms with a wide range of simulated myocardial thickness from 6 mm to 16 mm and LV volume from 33 mL to 128 mL. Tc-99 m radioactive isotope with a concentration of 2.5 μCi/mL was injected into the phantoms to simulate normal myocardial perfusion. Solid plastic inserts were placed in the simulated myocardium to mimic dense myocardial perfusion defects. Each cardiac phantom was subsequently submerged into a cylindrical container filled with water simulating uniform photon attenuation. A total of 72 image acquisitions were acquired using two different SPECT cameras. Images were reconstructed, filtered, re-orientated, aligned, and computer animated to generate gated SPECT image sequences. Phantom wall thickness, volume, and ejection fraction were quantified from the gated SPECT images using the new method. Correlations between SPECT quantified and actual values of phantom thickness, volume and ejection fraction were excellent. The quantitative results were not significantly affected by the myocardial perfusion defects simulated, and the results from the two SPECT cameras were highly reproducible. In conclusion, the new method developed is feasible to precisely detect the LV boundaries and may allow for accurate assessments of myocardial thickness, LV volume and ejection fraction.