LAUSR

PURPOSE Respiratory gating reduces respiratory blur in cardiac SPECT. It can be implemented as 3 gating schemes: i) equal amplitude-based gating (AG); ii) phase or time-based gating (TG); or iii) equal count-based gating (CG), i.e., a variant of amplitude-based method. The goal of this study is to evaluate the effectiveness of these respiratory gating methods for patients with different respiratory patterns in myocardial perfusion SPECT. METHODS We reviewed 1274 anonymized patient respiratory traces obtained via the Vicon motion-tracking system during their 99m Tc-sestamibi SPECT scans and grouped them into four breathing categories: i) regular respiration (RR); ii) periodic respiration (PR); iii) respiration with apnea (AR) and iv) un-classified respiration (UR). For each respiratory pattern, 15 patients were randomly selected and their list-mode data were rebinned using the 3 gating schemes. A preliminary reconstruction was performed for each gate with the heart region segmented and registered to a reference gate to estimate the respiratory motion. A final reconstruction incorporating respiratory motion correction was done to get a final image set. The estimated respiratory motion, the full-width-at-half-maxima (FWHM) measured across the image intensity profile of the left ventricle wall, as well as the normalized standard deviation measured in a uniform cuboid region of the thorax were analyzed. RESULTS There are 47.1%, 24.3%, 13.5% and 15.1% RR, PR, AR and UR patients respectively among the 1274 patients in this study. The differences among the 3 gating schemes in RR were smaller than other respiratory patterns. The AG and CG methods showed statistically larger motion estimation than TG particularly in the AR and PR patterns. Noise of AG varied more in different gates especially for AR and UR patterns. CONCLUSION More than half of the patients reviewed exhibited non-regular breathing patterns. Amplitude-based gating, i.e., AG and CG, is a preferred gating method for such patterns and is a robust respiratory gating implementation method given the respiratory pattern of the patients is unknown before data acquisition. Phase gating is also a feasible option for regular respiratory pattern.