Validation of in Vivo Myocardial Strain with PET Derived Feature Tracking: Direct Comparison with Tagging-Cine Magnetic Resonance.

Purpose: The aim of this study was to validate positron emission tomography feature tracking (PETFT) for assessing endocardial wall strain by comparing it with conventional tagging-cine magnetic resonance (MR) derived strain analysis (TAG). Methods: Consecutive 62 patients who underwent 13N-ammonia PETMR (52 males, mean age 66 years) were enrolled. PETFT and TAG were obtained through simultaneous acquisition with electrocardiography-gated PET and cine-MR for rest scan. Global longitudinal and circumferential strain (GLS and GCS) were calculated. Correlations and Bland-Altman plots were employed to evaluate associations, bias, and 95% limit of agreement (LOA) between PETFT and TAG. Results: PETFT and TAG showed significant correlations (r=0.69 [95% CI: 0.54 to 0.80], p<0.0001; r=0.55 [95% CI: 0.33-0.80], p < 0.0001 for GCS and GLS, respectively). Bland-Altman plot showed acceptable agreements (Bias 0.7 ± 6.7, LOA -12.5 to 13.9; Bias 1.3 ± 5.5, LOA -9.5 to 12.0 for GCS and GLS, respectively). In patients with abnormal perfusion, the correlations were still significant (r=0.76 [95% CI: 0.62 to 0.93], p<0.0001; r=0.59 [95% CI: 0.18 to 0.82], p=0.007 for GCS and GLS, respectively). Conclusion: PETFT has been identified as a feasible technique compared to TAG, demonstrating its potential as a novel tool for assessing wall strain in routine clinical practice. However, discrepancies in strain values may arise due to differences in algorithms and the presence of perfusion defects.