P774Detailed assessment of cardiac anatomy, myofiber structure and vasculature of rodent hearts using X-ray phase-contrast synchrotron radiation-based micro-CT
Background: While cardiomyocytes have a limited ability to shorten, the heart efficiently pumps a large volume-fraction thanks to a complex cell organisation in a 3D fibre structure. Such information is essential to understand diseases. CT/MRI provide structural information, however, their resolution is too low to study cellular mechanics in detail. Microscopy provides sufficient detail, but 3D imaging of whole hearts often results in distortions of detailed geometry and fibres. Therefore we developed a novel approach to study heart in great detail, but on the whole organ scale.

Methods: A rat heart was formalin-fixed, ethanol-dehydrated and embedded in agarose. X-ray phase-contrast synchrotron radiation-based micro-CT was performed at 7.43 μm resolution (ESRF-ID19). The heart was rotated over 360°. Five acquisitions were necessary to cover the whole heart along its long axis. The series were reconstructed using state-of-the-art filtered backprojection.

Results: Fig 1A shows a longitudinal reslicing of a dataset. The cardiac structures can be clearly differentiated (atria, ventricles, great vessels and valves). When using volume rendering, the architecture of the tricuspid valve (Fig 1B) and aortic valve (Fig 1C) can be observed in great detail. Details of local complexity of the walls and part of the vasculature are visible (Fig 1D,E). Fiber orientation can be recognised as well in the ventricular walls. The coronary vessels tree can also be segmented.

Conclusions: We have obtained novel, high resolution, datasets of a whole heart at myofiber resolution, providing structural information on microscopic level without the need of slicing. This opens up a new range of exciting possibilities for a systems approach towards cardiac function, providing fast acquisition of the whole heart. 

![Figure][1] [1]: pending:yes