Improved segmented modified Look-Locker inversion recovery T(1) mapping sequence in mice

OBJECT: To develop and evaluate a 2D modified Look-Locker (MOLLI) for high-resolution T(1) mapping in mice using a 3T MRI scanner. MATERIALS AND METHODS: To allow high-resolution T(1) mapping in mice at high heart rates a multi-shot ECG-triggered 2D MOLLI sequence was developed. In the proposed T(1) mapping sequence the optimal number of sampling points and pause cardiac cycles following an initial adiabatic inversion pulse was investigated in a phantom. Seven native control and eight mice, 3 days post myocardial infarction (MI) after administration of gadolinium were scanned. Two experienced readers graded the visual T(1) map quality. RESULTS: In T(1) phantoms, there were no significant differences (<0.4% error) between 12, 15 and 20 pause cardiac cycles (p = 0.1, 0.2 and 0.6 respectively) for 8 acquisition cardiac cycles for 600bpm in comparison to the conventional inversion recovery spin echo T(1) mapping sequence for short T(1)’s (<600 ms). Subsequently, all in-vivo scans were performed with 8 data acquisitions and 12 pause cardiac cycles to minimize scan time. The mean native T(1) value of myocardium in control animal was 820.5±52 ms. The post-contrast T(1) measured 3 days after MI in scar was 264±59 ms and in healthy myocardium was 512±62 ms. The Bland-Altman analysis revealed mean difference of only -1.06% of infarct size percentage between T(1) maps and LGE. CONCLUSIONS: A multi-shot 2D MOLLI sequence has been presented that allows reliable measurement of high spatial resolution T(1) maps in mice for heart rates up to 600bpm.