[Enlarge image]Top: Schematic of the VOS volumetric optoacoustic spectroscopy system and an optoacoustic image of a murine embryo at gestational day (GD) 16.5. Bottom: Cross-sectional images of the four-chamber embryonic heart (GD 16.5) at three different phases of the cardiac cycle. Scale bars = 1 mm.
Noninvasive monitoring of fetal cardiac development is crucial for understanding the sequences of the process and identifying any potential issues that might arise. Murine embryonic models are often used for studying the underlying causes of congenital heart disease because of their similarities to those of humans.1 But the rapid volumetric motion and small size of the murine embryonic heart make real-time visualization and functional characterization of the developing heart very challenging. Among the various techniques proposed for assessing embryonic cardiac development, we believe that optoacoustic imaging—which has demonstrated capacity in the longitudinal assessment of in utero morphological development in murine embryos2 and placental oxygenation3—holds the key to addressing this issue.
We have developed a real-time volumetric optoacoustic spectroscopy (VOS) imaging platform for the noninvasive evaluation of morphological, dynamic and functional changes in the murine embryonic heart during development.4 This technique leverages the large angular aperture of the hemispherical matrix array detector to provide high-resolution, transabdominal volumetric images of multiple murine embryos simultaneously in vivo. Embryonic organs, including the heart, placenta, brain vascular networks and spinal cord, can be visualized. The five-dimensional (real-time volumetric and spectroscopic) capacity of VOS and its high resolution (~100 µm spatial and 10 ms temporal) enable the visualization of the embryonic four-chamber heart.
Real-time rendering of high-resolution volumetric images of the internal embryonic heart leverages extensive analysis of cyclic cardiac motions and the time intervals between cardiac phase events to evaluate the quality of systolic and diastolic heart function during development. Additionally, by utilizing multi-wavelength spectroscopy, VOS enables us to map the distribution of oxygenated and deoxygenated hemoglobin across different cardiac chambers and quantify the oxygenation state of the embryonic heart.
We believe that our work will provide critical information for assessing embryonic cardiac development, which could allow the future clinical translation of VOS for evaluating human fetal cardiac diseases. The real-time and noninvasive characteristics of VOS offer significant advantages in longitudinal studies, especially in evaluating the dynamic progression of cardiac conditions such as congenital heart disease by identifying related morphological and functional changes in the developing heart.
Researchers
Maryam Hatami, Jessica Gutierrez, Pavel Bolshakov, Alexander Schill and Manmohan Singh, University of Houston, USA
Ali Özbek, Xosé Luís Deán-Ben and Daniel Razansky, University of Zurich and ETH Zurich, Switzerland
Kirill V. Larin, University of Houston and Baylor College of Medicine, USA
References
1. A. M. Moon, Pediatric Res. 59, 749 (2006).
2. J. Laufer et al. J. Biomed. Opt. 17, 061220 (2012).
3. K. Huda et al. Photoacoustics 20, 100209 (2020).
4. M. Hatami et al. Adv. Sci. 11, e2400089 (2024).