Black blood myocardial T₂ mapping

Purpose: To develop a black blood heart-rate adaptive T₂-prepared balanced steady-state free-precession (BEATS) sequence for myocardial T₂ mapping. Methods: In BEATS, blood suppression is achieved by using a combination of preexcitation and double inversion recovery pulses. The timing and flip angles of the preexcitation pulse are auto-calculated in each patient based on heart rate. Numerical simulations, phantom studies, and in vivo studies were conducted to evaluate the performance of BEATS. BEATS T₂ maps were acquired in 36 patients referred for clinical cardiac MRI and in 1 swine with recent myocardial infarction. Two readers assessed all images acquired in patients to identify the presence of artifacts associated with slow blood flow. Results: Phantom experiments showed that the BEATS sequence provided accurate T₂ values over a wide range of simulated heart rates. Black blood myocardial T₂ maps were successfully obtained in all subjects. No significant difference was found between the average T₂ measurements obtained from the BEATS and conventional bright-blood T₂; however, there was a decrease in precision using the BEATS sequence. A suppression of the blood pool resulted in sharper definition of the blood–myocardium border and reduced partial voluming effect. The subjective assessment showed that 16% (18 out of 108) of short-axis slices have residual blood artifacts (12 in the apical slice, 4 in the midventricular slice, and 2 in the basal slice). Conclusion: The BEATS sequence yields dark blood myocardial T₂ maps with better definition of the blood–myocardium border. Further studies are warranted to evaluate diagnostic accuracy of black blood T₂ mapping.