The performance of phase analysis in the presence of perfusion defects

Objectives Phase Analysis has been developed to measure left-ventricular (LV) dyssynchrony from conventional gated SPECT myocardial perfusion imaging (MPI) studies. Although phase analysis has shown promising clinical results, it needs to be evaluated under specific conditions to prove the validity of phase measurement. The purpose of this study is to evaluate the performance of phase analysis in myocardial regions with varying degrees of perfusion uptake.

Methods A special version of the XCAT phantom was developed to track the exact B-spline points in which the uptake values of the myocardium were altered. In this study, a region of 15 B-spline points with low perfusion uptake was simulated using uptake values of 10%, 20%, 30%, 40%, and 50% of the perfusion uptake in the normal region. The gated SPECT projection data were generated from the XCAT activity and attenuation maps with attenuation and collimator resolution effects. The gated SPECT projections were reconstructed with OSEM and the transaxial images were reoriented into gated short-axis images. The reconstructed images were then submitted into a program, which sampled the B-spline points to obtain the onset of mechanical contraction phases of the exact points.

Results Phases measured in B-spline points with low perfusion uptake did not significantly differ from phases measured in the same B-spline points with normal perfusion uptake based on paired t test.

Conclusions Phase analysis is capable of measuring onset of mechanical contraction phases in regions with abnormal perfusion uptake as low as 10% of the perfusion uptake in the normal regions.

Research Support Research on MHPA supported in part by an NIH/NHLBI grant 1R01HL094438 (PI: Ji Chen, PhD)

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P values of paired t test comparing phases in underperfused regions to those in normal regions