Comparison of Different Attenuation Correction Methods for Dual Gating Myocardial Perfusion SPECT/CT

Dual respiratory-cardiac gating realizes motionfreeze myocardial perfusion single photon emission computed tomography (SPECT). The aim of this paper is to evaluate the performance of various attenuation maps for dual gating cardiac SPECT. We used extended cardiac-torso phantom with Tc-99m-sestamibi distribution to generate a dataset with both respiratory and cardiac motion and then grouped them based on six respiratory and eight cardiac phases. The corresponding attenuation correction (AC) maps were used to simulate different CT protocols: dual gating CT (DCT), respiratory gated CT (RCT), cine average CT (ACT), interpolated CT ('CT), helical CTs at end-inspiration (HCT-in), end-expiration (HCT-ex), and mid-respiration (HCT-mid), respectively. One hundred and twenty noise-free and realistic noisy projections were generated over 180° from RAO to LPO and reconstructed by OS-EM method using different AC maps. The reconstructed images in different respiratory phases were registered to one reference endexpiration phase and summed up as a cardiac image for each cardiac phase. The corresponding polar maps were generated and further analyzed using 17-segment plots. Relative difference (RD) of the average intensity was computed in each segment using the polar maps with DCT-AC as reference. Substantial artifacts could be found in HCT-in AC images in every cardiac phase. For all eight noise-free cardiac phases, the average RDmax for AC with ACT, HCT-ex, HCT-in, HCT-mid, RCT, and 'CT comparing to DCT were 4.76%, 4.95%, 10.54%, 4.23%, 2.39%, and 2.76%, respectively. For all eight noisy cardiac phases, the average RDmax for AC with ACT, HCT-ex, HCT-in, HCT-mid, RCT, and 'CT comparing to DCT were 4.09%, 5.04%, 9.24%, 4.02%, 3.22%, and 2.85%, respectively. The 'CT and RCT have the best AC performance for dual gating SPECT, while HCT-ex, HCT-in, HCT-mid, and ACT show inferior results. Since RCT and DCT are not commonly used in clinics due to complex implementation and radiation concern, 'CT is recommended, followed by HCTmid or HCT-ex for AC in dual gating cardiac SPECT with good accuracy and relative low radiation dose.