Session S62.3

Toward an Imaging-Based Atlas of the Mouse Myocardial Fiber Structure

LJ Healy, S Joshi, O Abdullah, EW Hsu*

University of Utah
Salt Lake City, UT, USA

Imaging-based models or atlases of the fiber structure of the myocardium are highly desirable for computational analyses of its material properties and functions To date, despite that the mouse species has become a preferred platform for studying cardiac diseases, few computational models and no atlas exist for even the normal mouse heart, which is largely due to the technical challenges in fiber orientation mapping in the small organ. Construction of a mouse myocardial structural atlas necessitates advances in both methods for fiber orientation measurement, and since fiber orientations are vector rather than scalar quantities, appropriate techniques for computational anatomical and statistical analyses. By characterizing the anisotropy of tissue water diffusion exerted by the molecular environment, the so-called magnetic resonance diffusion tensor imaging (MR-DTI, or DTI) has emerged as a viable alternative to conventional histology for quantifying the structures of ordered tissues including the myocardium. However, practical applications of DTI are hampered by its inherently low SNR, large dataset size (i.e., long scan times), and by tradeoff, relatively low spatial resolution. To accelerate the DTI data acquisition, we have introduced a novel approach that combines reduced sampling and constrained reconstruction, and showed it to significantly improve the data acquisition-time efficiency (i.e., measurement accuracy versus scan time). The methodology was recently applied to DTI of the fixed mouse heart to demonstrate the practical feasibility of 3D, non-destructive mapping the myocardial structure at 100 µm spatial resolution, and at orders of magnitude more measurement points than achievable by histology. Preliminary computational anatomical analysis of the DTI-derived myocardial fiber structure, which includes creation of an unbiased atlas of the gross anatomy, warping of the fiber structure represented by the fiber helix angles, and principal component analysis (PCA) of the results, reveals a surprisingly low degree of variability among likewise hearts, that the intra-species variability can be sufficiently captured by a group size of as small as 6. Combined, these developments and findings are extremely encouraging, and pave the way for the construction of imaging-based fiber structural atlas of the mouse heart.

(Abstract Control Number: 201)