Langendorff perfused hearts have been frequently studied in recent years using optical fluorescence imaging. This in vitro approach, which enables the heart to continue beating after extraction from the body of the animal, allows investigation of physiological functions with relative simplicity compared to in vivo setups. For example, when combined with voltage- and calcium- sensitive dyes, optical mapping of transmembrane potential, calcium transients, and other parameters can lead to a better understanding of cardiac mechanisms underlying heart failures and diseases. However, biomedical optical imaging is fundamentally limited to superficial investigations due to light scattering in tissues, restricting mapping to the heart surface only. The ability to visualize the heart septum would be important for comprehensive cardiac research. While 3D ultrasound can offer imaging of the entire heart, it can only provide mechanical contrast and the spatio-temporal resolution is also insufficient for imaging the heart in 3D on a beat-by-beat basis. Herein, we investigate on the capabilities of optoacoustic tomographic imaging of the Langendorff heart. The heart isolation method allows direct imaging without the presence of surrounding tissues and reduced blood content, significantly improving the penetration depth as well as image quality. The imaging system can acquire 3D images of the heart with optical contrast at an imaging rate of 100 Hz and 150 µm resolution. This enables capturing beat-by-beat heart motion with temporal resolution of 33 sampling instances per heartbeat. The high spatial resolution also allows identifying important internal heart features, including the septum, valves, cordae tendineae, and papillary muscles.
Proc. SPIE. 10064, Photons Plus Ultrasound: Imaging and Sensing 2017
KEYWORDS: Image visualization, Real time imaging, Tissues, Heart, Data acquisition, Temporal resolution, Transducers, Photoacoustic tomography, In vivo imaging, Spherical lenses, Beam propagation method, Mouse models
Extraction of murine cardiac functional parameters on a beat-by-beat basis remains challenging with the existing imaging modalities. Novel methods enabling in vivo characterization of functional parameters at a high temporal resolution are poised to advance cardiovascular research and provide a better understanding of the mechanisms underlying cardiac diseases. We present a new approach based on analyzing contrast-enhanced optoacoustic (OA) images acquired at high volumetric frame rate without using cardiac gating or other approaches for motion correction. Acute myocardial infarction was surgically induced in murine models, and the method was modified to optimize for acquisition of artifact-free optoacoustic data. Infarcted hearts could be differentiated from healthy controls based on a significantly higher pulmonary transit time (PTT: infarct 2.07 s vs. healthy 1.34 s), while no statistically significant difference was observed in the heart rate (318 bpm vs. 309 bpm). In combination with the proven ability of optoacoustics to track targeted probes within the injured myocardium, our method is capable of depicting cardiac anatomy, function, and molecular signatures on a beat-by-beat basis, both with high spatial and temporal resolution, thus providing new insights into the study of myocardial ischemia.
Determination of ovarian status and follicle monitoring are common methods of diagnosing female infertility. We
evaluated the suitability of selective plane illumination microscopy (SPIM) for the study of ovarian follicles. Owing to
the large field of view and fast acquisition speed of our newly developed SPIM system, volumetric image stacks from
entire intact samples of pig ovaries have been rendered demonstrating clearly discernible follicular features like follicle
diameters (70 μm - 2.5 mm), size of developing Cumulus oophorus complexes (COC ) (40 μm - 110 μm), and follicular
wall thicknesses (90 μm-120 μm). The observation of clearly distinguishable COCs protruding into the follicular antrum
was also shown possible, and correlation with the developmental stage of the follicles was determined. Follicles of all
developmental stages were identified, and even the small primordial follicle clusters forming the egg nest could be
observed. The ability of the system to non-destructively generate sub-cellular resolution 3D images of developing
follicles, with excellent image contrast and high throughput capacity compared to conventional histology, suggests that it
can be used to monitor follicular development and identify structural abnormalities indicative of ovarian ailments.
Accurate folliculometric measurements provided by SPIM images can immensely help the understanding of ovarian
physiology and provide important information for the proper management of ovarian diseases.