Fat-saturated dark-blood cardiac T2 mapping in a single breath-hold

Conventional cardiac T2 mapping suffers from the partial-voluming effect in the endocardium and epicardium due to the co-presence of intra-cavity blood and epicardial fat. The aim of the study is to develop a novel single-breath-hold Fat-Saturated Dark-Blood (FSDB) cardiac T2-mapping technique to mitigate the partial-voluming and improve T2 accuracy.

The proposed FSDB T2-mapping technique combines T2-prepared bSSFP, a novel use of double inversion-recovery with heart-rate-adaptive TI, and spectrally-selective fat saturation to mitigate partial-voluming from both the blood and fat. FSDB T2 mapping was compared to conventional T2 mapping via simulations, phantom imaging, healthy-subject imaging (n = 8), and patient imaging (n = 7). In the healthy subjects, a high-resolution coplanar anatomical imaging was performed to provide a gold standard for segmentation of endocardium and epicardium. T2 maps were registered to the gold standard image to evaluate any inter-layer T2 difference, which is a surrogate for partial-voluming.

Simulations and phantom imaging showed that FSDB T2 mapping was accurate in a range of heartrates, off-resonance, and T2 values, and blood/fat reasonably nulled in a range of heartrates. In healthy subjects, FSDB T2 mapping showed similar T2 values over different myocardial layers in all 3 short-axis slices (e.g. basal epicardial/mid-wall/endocardial T2 = 42 ± 2 ms/41 ± 1 ms/42 ± 1 ms), whereas conventional T2 mapping showed considerably increased T2 in the endocardium and epicardium (e.g. basal epicardial/mid-wall/endocardial T2 = 48 ± 3 ms/43 ± 1 ms/49 ± 3 ms). The homogeneous T2 in the FSDB T2 mapping increased the apparent LV-wall thickness by 25-41% compared with the conventional method.

The proposed technique improves accuracy of myocardial T2 mapping against partial-voluming associated with both fat and blood, facilitating a multi-layer T2 evaluation of the myocardium. This technique may improve utility of cardiac T2 mapping in diseases affecting the endocardium and epicardium, and in patients with a small heart.