Free-breathing 3-dimensional (3D) late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) techniques with high isotropic resolution and dark-blood contrast may optimize the delineation of myocardial scar patterns. The extended acquisition times required for such scans, however, are paralleled by a declining contrast agent concentration. Consequently, the optimal inversion time (TI) is continuously increasing. We hypothesize that a steadily increasing (dynamic) TI can compensate for this effect and can lead to improved blood nulling to optimize the dark-blood contrast.
Materials and Methods
Fifty consecutive patients with previous cardiac arrhythmias, scheduled for high-resolution 3D LGE MRI, were prospectively enrolled between October 2017 and February 2020. Free-breathing 3D dark-blood LGE MRI with high isotropic resolution (1.6 × 1.6 × 1.6 mm) was performed using a conventional fixed TI (n = 25) or a dynamic TI (n = 25). The average increase in blood nulling TI per minute was obtained from Look-Locker scans before and after the 3D acquisition in the first fixed TI group. This average increment in TI was used as input to calculate the dynamic increment of the initial blood nulling TI value as set in the second dynamic TI group. Regions of interest were drawn in the left ventricular blood pool to assess mean signal intensity as a measure for blood pool suppression. Overall image quality, observer confidence, and scar demarcation were scored on a 3-point scale.
Three-dimensional dark-blood LGE data sets were successfully acquired in 46/50 patients (92%). The calculated average TI increase of 2.3 ± 0.5 ms/min obtained in the first fixed TI group was incorporated in the second dynamic TI group and led to a significant decrease of 72% in the mean blood pool signal intensity compared with the fixed TI group (P < 0.001). Overall image quality (P = 0.02), observer confidence (P = 0.02), and scar demarcation (P = 0.01) significantly improved using a dynamic TI.
A steadily increasing dynamic TI improves blood pool suppression for optimized dark-blood contrast and increases observer confidence in free-breathing 3D dark-blood LGE MRI with high isotropic resolution.