Comparison between cardiac magnetic resonance stress T1 mapping and [15O]H2O positron emission tomography in patients with suspected obstructive coronary artery disease

Aims To compare cardiac magnetic resonance (CMR) measurement of T1 reactivity (Delta T1) with [O-15]H2O positron emission tomography (PET) measurements of quantitative myocardial perfusion. Methods and results Forty-three patients with suspected obstructed coronary artery disease underwent [O-15]H2O PET and CMR at 1.5-T, including rest and adenosine stress T1 mapping (ShMOLLI) and late gadolinium enhancement to rule out presence of scar tissue. Delta T1 was determined for the three main vascular territories and compared with [O-15]H2O PET-derived regional stress myocardial blood flow (MBF) and myocardial flow reserve (MFR). Delta T1 showed a significant but poor correlation with stress MBF (R-2 = 0.04, P = 0.03) and MFR (R-2 = 0.07, P = 0.004). Vascular territories with impaired stress MBF (i.e. <= 2.30 mL/min/g) demonstrated attenuated Delta T1 compared with vascular territories with preserved stress MBF (2.9 +/- 2.2% vs. 4.1 +/- 2.2%, P = 0.008). In contrast, Delta T1 did not differ between vascular territories with impaired (i.e. <2.50) and preserved MFR (3.2 +/- 2.6% vs. 4.0 +/- 2.1%, P = 0.25). Receiver operating curve analysis of Delta T1 resulted in an area under the curve of 0.66 [95% confidence interval (CI): 0.57-0.75, P = 0.009] for diagnosing impaired stress MBF and 0.62 (95% CI: 0.53-0.71, P = 0.07) for diagnosing impaired MFR. Conclusions CMR stress T1 mapping has poor agreement with [O-15]H2O PET measurements of absolute myocardial perfusion. Stress T1 and Delta T1 are lower in vascular territories with reduced stress MBF but have poor accuracy for detecting impaired myocardial perfusion.