Purpose:
The aim of this study was to evaluate the regional (i.e. myocardial segments) variability as well as the overall image quality of cardiac T2 maps in systolic and diastolic phase, using gradient- and spin-echo (GRASE) sequence. Furthermore, fat suppression (FS) technique was activated in this sequence and T2 values were measured.
Methods:
T2 maps were acquired using GRASE technique at 1.5 T (Philips Ingenia) in 6 wolunteer and 10 patients with cardiac disease. Diastolic and systolic T2-mapping were done with and without FS. The image quality and motion artefact were measured in four sequences.
Results:
In both healthy volunteers and patients, systolic readout increased the thickness of myocardium, compared to the diastolic readout. The effect of time delay (TD) was not significant on T2 values in both groups (p > 0.05), with slightly less T2 values in systole compared to diastole (< 5 ms). The FS technique significantly increased T2 values in both systolic and diastolic phases in both groups (p = 0.000) and no significant differences was shown between them (p > 0.05). All T2 maps were of moderate quality due to being a spin echo based sequence, but systolic TD were associated with higher variability in segmental T2 values. In tachyarrhythmia patients, systolic acquisitions produced consistently excellent T2 maps (median R (2) = 0.993).
Conclusions:
GRASE technique showed more T2 variability and less T2 values, compared to diastolic readout. Slightly shorter T2 values with more variablity in systole are mostly explained by blood motion artefact due to changing double inversion recovery (DIR) as a black blood technique to TE preparation with spoiler gradient to be able to perform this technique in systolic phase. In patients
with tachyarrhythmia, systolic T2-mapping is feasible, circumvents mistriggering and produces good quality T2 maps. This extends its clinical applicability to challenging rhythms (such as rapid atrial fibrillation) and aids the investigation of thinner myocardial segments. With further validation, systolic T2-mapping may become a new and convenient standard for myocardial T2-mapping. Keywords: T2 mapping, GRASE technique, cardiac magnetic resonance imaging, systolic phase, diastolic phase.