Contrast-free high-resolution 3D magnetization transfer imaging for simultaneous myocardial scar and cardiac vein visualization

Abstract

Objective To develop a three-dimensional (3D) high-resolution free-breathing magnetization transfer ratio (MTR) sequence for contrast-free assessment of myocardial infarct and coronary vein anatomy. Materials and methods Two datasets with and without off-resonance magnetization transfer preparation were sequentially acquired to compute MTR. 2D image navigators enabled beat-to-beat translational and bin-to-bin non-rigid motion correction. Two different imaging sequences were explored. MTR scar localization was compared against 3D late gadolinium enhancement (LGE) in a porcine model of myocardial infarction. MTR variability across the left ventricle and vessel sharpness in the coronary veins were evaluated in healthy human subjects. Results A decrease in MTR was observed in areas with LGE in all pigs (non-infarct: 25.1 ± 1.7% vs infarct: 16.8 ± 1.9%). The average infarct volume overlap on MTR and LGE was 62.5 ± 19.2%. In humans, mean MTR in myocardium was between 37 and 40%. Spatial variability was between 15 and 20% of the mean value. 3D whole heart MT-prepared datasets enabled coronary vein visualization with up to 8% improved vessel sharpness for non-rigid compared to translational motion correction. Discussion MTR and LGE showed agreement in infarct detection and localization in a swine model. Free-breathing 3D MTR maps are feasible in humans but high spatial variability was observed. Further clinical studies are warranted.

Quantitative magnetization transfer imaging for non‐contrast enhanced detection of myocardial fibrosis

“…In summary, a reference protocol was implemented comprising 25 images with 25 distinct MT weightings (at fivedifferent frequency offsets log‐spaced between 1 and 7.7 kHz and five different MT FAs linearly spaced between 360 and 800°) partly based on previous work by the authors 26 . Next, MT parameter maps were calculated based on dictionary matching using all the acquired MT images and (independently acquired) T1 and T2 maps.…”

“…In summary, a reference protocol was implemented comprising 25 images with 25 distinct MT weightings (at fivedifferent frequency offsets log-spaced between 1 and 7.7 kHz and five different MT FAs linearly spaced between 360 and 800°) partly based on previous work by the authors. 26 Next, MT parameter maps were calculated based on dictionary matching using all the acquired MT images and (independently acquired) T1 and T2 maps. Then, PSR and T B 2 values were calculated for all possible combinations of five MT weightings and the best combination was chosen based on maximizing the accuracy of the parameter values and the coefficient of determination of the match.…”

Development, validation, qualification, and dissemination of quantitative MR methods: Overview and recommendations by the ISMRM quantitative MR study group

“…However, it has been suggested that certain confounders to MOLLI T 1 measurements may enhance clinical sensitivity. 137 As illustrated in Figure 7, this somewhat counter-intuitive phenomenon arises because some confounders (e.g., magnetization transfer 84,137,138 ) are sensitive to pathological alterations, leading to inflated effect size in certain disease entities compared to unbiased measurements. However, as a result of these confounders, the measurand in MOLLI is highly dependent on the sequence parameters (e.g., TR, flip angle, slice profile), the scanner specifications and tissue properties that are not related to the tissue T 1 time.…”