Probing cardiomyocyte mobility with multi-phase cardiac diffusion tensor MRI

Abstract

Purpose Cardiomyocyte organization and performance underlie cardiac function, but the in vivo mobility of these cells during contraction and filling remains difficult to probe. Herein, a novel trigger delay (TD) scout sequence was used to acquire high in-plane resolution (1.6 mm) Spin-Echo (SE) cardiac diffusion tensor imaging (cDTI) at three distinct cardiac phases. The objective was to characterize cardiomyocyte organization and mobility throughout the cardiac cycle in healthy volunteers. Materials and methods Nine healthy volunteers were imaged with cDTI at three distinct cardiac phases (early systole, late systole, and diastasis). The sequence used a free-breathing Spin-Echo (SE) cDTI protocol (b-values = 350s/mm2, twelve diffusion encoding directions, eight repetitions) to acquire high-resolution images (1.6x1.6x8mm3) at 3T in ~7 minutes/cardiac phase. Helix Angle (HA), Helix Angle Range (HAR), E2 angle (E2A), Transverse Angle (TA), Mean Diffusivity (MD), diffusion tensor eigenvalues (λ1-2-3), and Fractional Anisotropy (FA) in the left ventricle (LV) were characterized. Results Images from the patient-specific TD scout sequence demonstrated that SE cDTI acquisition was possible at early systole, late systole, and diastasis in 78%, 100% and 67% of the cases, respectively. At the mid-ventricular level, mobility (reported as median [IQR]) was observed in HAR between early systole and late systole (76.9 [72.6, 80.5]° vs 96.6 [85.9, 100.3]°, p<0.001). E2A also changed significantly between early systole, late systole, and diastasis (27.7 [20.8, 35.1]° vs 45.2 [42.1, 49]° vs 20.7 [16.6, 26.4]°, p<0.001). Conclusion We demonstrate that it is possible to probe cardiomyocyte mobility using multi-phase and high resolution cDTI. In healthy volunteers, aggregate cardiomyocytes re-orient themselves more longitudinally during contraction, while cardiomyocyte sheetlets tilt radially during wall thickening. These observations provide new insights into the three-dimensional mobility of myocardial microstructure during systolic contraction.

Patch2Self denoising of Diffusion MRI with Self-Supervision and Matrix Sketching

“…In Fig. 4C,D we show how P2S-sketch does not cause any signal loss even in the presence of physiological noise (porcine cardiac data) [32, 63] and ghost artefacts [70, 51], which are ubiquitous in MRI acquisitions. Note that in either case, P2S-sketch strictly only suppresses noise and does not lead to signal loss or smoothing.…”

Comparison of interpolation methods of predominant cardiomyocyte orientation from in vivo and ex vivo cardiac diffusion tensor imaging data

“…As a consequence, motion occurring during readout may lead to spatial inconsistency of information contained in low and high spatial frequencies. To date, shortening readout duration by means of parallel imaging or multishot acquisition schemes has allowed for performance of cDTI at spatial resolutions of 1.6 × 1.6 mm 2 and 1.8 × 1.8 mm 2 54,62 . Additionally, lowering the readout bandwidth leads to increased susceptibility to off‐resonance artifacts that may require dedicated treatment 63,64 .…”

“…Assuming a T 2 of 60 ms (Reference 65 ) leads to an additional signal attenuation of ≈20%, which needs to be considered. Moulin et al 54 compensated for the prolonged echo time by partial Fourier sampling and an under‐sampling factor of 2 in conjunction with a more powerful gradient system to achieve an echo time of 61 ms (versus 81 ms) for a spatial resolution of 1.6 × 1.6 mm 2 . Our simulation does not consider blurring due to broadening of the point spread function by decay during echo planar imaging.…”

“…Two resolution settings were chosen to cover the range of commonly used resolution of in vivo scans: 37,51‐54 a fine setting of 1.5 × 1.5 × 8 mm 3 and a coarse setting of 2.5 × 2.5 × 8 mm 3 . These two input data sets were obtained by down‐sampling the high‐resolution data.…”

A groupwise registration and tractography framework for cardiac myofiber architecture description by diffusion MRI: an application to the ventricular junctions

“…Other in vivo studies [21,22] have also demonstrated that changes in diffusion tensor metrics, such as Fractional Anisotropy (FA), and Apparent Diffusion Coefficient (ADC) agree with late gadolinium enhancement (LGE) imaging and can depict areas with myocardial infarction and tissue remodeling. Despite growing progress in the field of MRI pulse sequences [23][24][25][26], hardware [27] and reconstruction methods [28], clinical in vivo DTI MRI remains limited in spatial resolution and signal to noise ratio (SNR) by clinical field strength, and scan times [29]. In vivo cardiovascular DTI must also take into account combined respiratory and cardiac motions, and compensated for them with a dedicated acquisition scheme [23].…”