Saturation Recovery Myocardial T₁ Mapping with a Composite Radiofrequency Pulse on a 3T MR Imaging System

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Purpose: To evaluate the effect of a composite radiofrequency (RF) pulse on saturation recovery (SR) myocardial T₁ mapping using a 3T magnetic resonance (MR) system.

Materials and Methods: Phantom and in vivo studies were performed with a clinical 3T MR scanner. Accuracy and reproducibility of the SR T₁ mapping using conventional and composite RF pulses were first compared in phantom experiments. An in vivo study was performed of 10 healthy volunteers who were imaged with conventional and composite RF pulse methods twice each. In vivo reproducibility of myocardial T₁ value and the inter-segment variability were assessed.

Results: The phantom study revealed significant differences in the mean T₁ values between the two methods, and the reproducibility for the composite RF pulse was significantly smaller than that for the conventional RF pulse. For both methods, the correlations of the reference and measured T₁ values were excellent (r² = 0.97 and 0.98 for conventional and composite RF pulses, respectively). The in vivo study showed that the mean T₁ value for composite RF pulse was slightly lower than that for conventional RF pulse, but this difference was not significant (P = 0.06). The inter-segment variability for the composite RF pulse was significantly smaller than that for conventional RF pulse (P < 0.01). Inter-scan correlations of T₁ measurements of the first and second scans were highly and weakly correlated to composite RF pulses (r = 0.83 and 0.29, respectively).

Conclusion: SR T₁ mapping using composite RF pulse provides accurate quantification of T₁ values and can lessen measurement variability and enable reproducible T₁ measurements.