Affiliation:
1. Leeds Institute of Cardiovascular and Metabolic Medicine University of Leeds Leeds UK
2. Leeds Teaching Hospitals Trust Leeds UK
3. Faculty of Industrial Design Engineering Delft University of Technology Delft Netherlands
4. Center for Medical Image Computing, Department of Medical Physics & Biomedical Engineering and Department of Neuroinflammation University College London London UK
5. Astrea Bioseparation Comberton UK
6. Bioxydyn Limited Manchester UK
7. Medical Radiation Physics, Clinical Sciences Lund Lund University Lund Sweden
Abstract
PurposeTensor‐valued diffusion encoding can probe more specific features of tissue microstructure than what is available by conventional diffusion weighting. In this work, we investigate the technical feasibility of tensor‐valued diffusion encoding at high b‐values with q‐space trajectory imaging (QTI) analysis, in the human heart in vivo.MethodsTen healthy volunteers were scanned on a 3T scanner. We designed time‐optimal gradient waveforms for tensor‐valued diffusion encoding (linear and planar) with second‐order motion compensation. Data were analyzed with QTI. Normal values and repeatability were investigated for the mean diffusivity (MD), fractional anisotropy (FA), microscopic FA (μFA), isotropic, anisotropic and total mean kurtosis (MKi, MKa, and MKt), and orientation coherence (Cc). A phantom, consisting of two fiber blocks at adjustable angles, was used to evaluate sensitivity of parameters to orientation dispersion and diffusion time.ResultsQTI data in the left ventricular myocardium were MD = 1.62 ± 0.07 μm2/ms, FA = 0.31 ± 0.03, μFA = 0.43 ± 0.07, MKa = 0.20 ± 0.07, MKi = 0.13 ± 0.03, MKt = 0.33 ± 0.09, and Cc = 0.56 ± 0.22 (mean ± SD across subjects). Phantom experiments showed that FA depends on orientation dispersion, whereas μFA was insensitive to this effect.ConclusionWe demonstrated the first tensor‐valued diffusion encoding and QTI analysis in the heart in vivo, along with first measurements of myocardial μFA, MKi, MKa, and Cc. The methodology is technically feasible and provides promising novel biomarkers for myocardial tissue characterization.
Funder
European Society of Cardiology
Cancerfonden
Vetenskapsrådet
Wellcome Trust
Subject
Radiology, Nuclear Medicine and imaging