A fast black‐blood sequence for four‐dimensional cardiac manganese‐enhanced MRI in mouse

Abstract

The increasing number of mouse models of cardiac diseases requires improvements in the current MRI tools. Anatomic and functional cardiac phenotyping by MRI calls for both time and space resolution in three dimensions. Black-blood contrast is often needed for the accurate delineation of myocardium and chambers, and is consistent with manganese contrast enhancement. In this article, we propose a fast, three-dimensional, time-resolved (four-dimensional), black-blood MRI sequence that allows mouse heart imaging at 10 periods of the cardiac cycle within 30 min at an isotropic resolution of 200 µm. Two-dimensional imaging was possible within 80 s. Blood cancellation was achieved by employing bipolar gradients without the use of a double inversion recovery preparation scheme. Saturation slices were added in two-dimensional experiments for better blood nulling. The rapidity of the two-dimensional acquisition protocol allowed the measurement of the time course of contrast enhancement on manganese infusion. Owing to the very high contrast-to-noise ratio, manganese-enhanced MRI in four dimensions made possible the accurate assessment of regional cardiac volumes in healthy animals. In experimentally infarcted mice, the size of the ischemic zone could be measured easily with this method. The technique might be valuable in evaluating mouse heart diseases and their follow-up in longitudinal studies.

Fast and robust 3D T1 mapping using spiral encoding and steady RF excitation at 7 T: application to cardiac manganese enhanced MRI (MEMRI) in mice

“…To demonstrate the efficiency of the current method in the case of cardiac disease, mice with surgically induced MI were injected with 60 μL of MnCl 2, corresponding to a dose of 86 µmol kg −1 . Manganese ions, as previously demonstrated in the literature , did not penetrate the infarcted region, leading to a decrease in the T 1 in healthy regions of the myocardium without changing the T 1 of the infarcted areas. As shown in Figure (a), the current protocol allowed us to visualize the myocardial infarct in 3D with high spatial resolution.…”

“…Between each injection, a delay of 15 min was necessary to reach the maximum Mn 2+ infusion in the heart, as previously demonstrated by Lefrançois et al . .…”

“…In this protocol ten spirals were acquired per stack, and 48 stacks were acquired per k-space. (b) The signal of each voxel was followed at different times after the inversion pulse, and fit to Equation [4] to determine T 1 . the longitudinal axis.…”

“…where A is the proportional coefficient. Note that m ∞ in Equation [4] was replaced by its equation (Equation [2]). Three fitting parameters were used: m max , A and the T 1 value.…”

Contrast‐enhanced MRI of murine myocardial infarction – Part I

“…2A). MEMRI has also been applied in an IR model with a 3 T clinical scanner and an approximately 10-fold higher dose MnCl 2 (30) and in a PO model using a 3D black-blood sequence (31). Both studies confirmed that infarct size and location on MEMRI were in agreement with TTC staining.…”