A method to study the hemodynamics of chicken embryo's aortic arches using optical coherence tomography

Embryonic Mouse Cardiodynamic OCT Imaging

The embryonic heart is an active and developing organ. Genetic studies in mouse models have generated great insight into normal heart development and congenital heart defects, and suggest mechanical forces such as heart contraction and blood flow to be implicated in cardiogenesis and disease. To explore this relationship and investigate the interplay between biomechanical forces and cardiac development, live dynamic cardiac imaging is essential. Cardiodynamic imaging with optical coherence tomography (OCT) is proving to be a unique approach to functional analysis of the embryonic mouse heart. Its compatibility with live culture systems, reagent-free contrast, cellular level resolution, and millimeter scale imaging depth make it capable of imaging the heart volumetrically and providing spatially resolved information on heart wall dynamics and blood flow. Here, we review the progress made in mouse embryonic cardiodynamic imaging with OCT, highlighting leaps in technology to overcome limitations in resolution and acquisition speed. We describe state-of-the-art functional OCT methods such as Doppler OCT and OCT angiography for blood flow imaging and quantification in the beating heart. As OCT is a continuously developing technology, we provide insight into the future developments of this area, toward the investigation of normal cardiogenesis and congenital heart defects.

Label-free optical imaging in developmental biology [Invited]

Application of optical imaging in developmental biology marks an exciting frontier in biomedical optics. Optical resolution and imaging depth allow for investigation of growing embryos at subcellular, cellular, and whole organism levels, while the complexity and variety of embryonic processes set multiple challenges stimulating the development of various live dynamic embryonic imaging approaches. Among other optical methods, label-free optical techniques attract an increasing interest as they allow investigation of developmental mechanisms without application of exogenous markers or fluorescent reporters. There has been a boost in development of label-free optical imaging techniques for studying embryonic development in animal models over the last decade, which revealed new information about early development and created new areas for investigation. Here, we review the recent progress in label-free optical embryonic imaging, discuss specific applications, and comment on future developments at the interface of photonics, engineering, and developmental biology.

Ultrahigh-speed line-scan SD-OCT for four-dimensional in vivo imaging of small animal models

We report an ultrahigh-speed and high-resolution line-scan spectral-domain optical coherence tomography (SD-OCT) system that integrates a number of mechanisms for improving image quality. The illumination uniformity is significantly improved by the use of a Powell lens; Phase stepping and differential reconstruction are combined to suppress autocorrelation artifacts; Nonlocal means (NLM) is employed to enhance the signal to noise ratio while minimizing motion artifacts. The system is capable of acquiring cross-sectional images at more than 3,500 B-scans per second with sensitivities between 70dB and 90dB. The high B-scan rate enables image post-processing with nonlocal means, an advanced noise reduction algorithm that affords enhanced morphological details and reduced motion artifacts. The achieved axial and lateral resolutions are 2.0 and 6.2 microns, respectively. We have used this system to acquire four-dimensional (three-dimensional space and one-dimensional time) imaging data from live chicken embryos at up to 40 volumes per second. Dynamic cardiac tissue deformation and blood flow could be clearly visualized at high temporal and spatial resolutions, providing valuable information for understanding the mechanical and fluid dynamic properties of the developing cardiac system.