Background-Optical coherence tomography (OCT) is a depth-resolved, noninvasive, non-destructive imaging modality, the use of which has yet to be fully realized in developmental biology. Methods and Results-We visualized embryonic chick hearts at looping stages using an OCT system with a 22 m axial and 27 m lateral resolution and an acquisition rate of 4000 A-scans per second. Normal chick embryos from stages 14 to 22 and sham-operated and cardiac neural crest-ablated embryos from stages 15 and 18 were scanned by OCT. Three-dimensional data sets were acquired and processed to create volumetric reconstructions and short video clips. The OCT-scanned embryos (2 in each group) were photographed after histological sectioning in comparable planes to those visualized by OCT. The optical and histological results showing cardiovascular microstructures such as myocardium, the cardiac jelly, and endocardium are presented. Conclusions-OCT is a powerful imaging modality which can provide new insight in assessing and understanding normal and abnormal cardiac development in a variety of animal models. Key Words: imaging Ⅲ morphogenesis Ⅲ tomography Ⅲ cardiac volume Ⅲ heart defects, congenital T he study of heart development has undergone a renaissance in research in recent years. 1 Various technologies, including video light microscopy, 2,3 ultrasound, 4 confocal microscopy, 5 high resolution MRI, 6 and optical coherence tomography 7 (OCT) have been applied in the past to visualize embryonic hearts 8 to gain more insight into the complex developmental process of cardiovascular development.OCT is an echo-based imaging modality that measures the time-of-flight of back-reflected light using low-coherence interferometry. 9 Through the use of broadband near-infrared light sources, OCT achieves resolutions of Ϸ10 to 30 m, with depth penetrations of a few millimeters. Since its introduction in 1991, 7 OCT has been used in the imaging of semi-transparent tissues (eg, anterior segment and cornea of the eye, 10 Xenopus laevis tadpoles 11,12 ) and in highly lightscattering tissues (eg, retina, 7 subluminal structures in the gastrointestinal tract 13 ). Further, current-generation systems are capable of video-rate imaging. 14 Catheter-based OCT systems are being developed to image atherosclerotic plaques clinically. 15 Proof-of-principle experiments in basic research have imaged the atrioventricular node 16 and used color Doppler OCT to quantify flow dynamics in the Xenopus laevis heart. 17In this study, we demonstrate three-dimensional OCT imaging of the chick embryo heart during looping. Using this three-dimensional data, we compared OCT images with histological sections and generated volumetric reconstructions of the early heart tube in normal and cardiac neural crest (CNC)-ablated embryos. Methods OCTThe principles and physics of OCT have been described in detail 7,9 but will be briefly summarized here. OCT and ultrasound perform B-scan imaging in analogous manners; a 2-dimensional image (ie, B-scan) is composed of a series of 1-dimens...
The heart is the first organ to function in vertebrate embryos. The human heart, for example, starts beating around the 21st embryonic day. During the initial phase of its pumping action, the embryonic heart is seen as a pulsating blood vessel that is built up by (1) an inner endothelial tube lacking valves, (2) a middle layer of extracellular matrix, and (3) an outer myocardial tube. Despite the absence of valves, this tubular heart generates unidirectional blood flow. This fact poses the question how it works. Visual examination of the pulsating embryonic heart tube shows that its pumping action is characterized by traveling mechanical waves sweeping from its venous to its arterial end. These traveling waves were traditionally described as myocardial peristaltic waves. It has, therefore, been speculated that the tubular embryonic heart works as a technical peristaltic pump. Recent hemodynamic data from living embryos, however, have shown that the pumping function of the embryonic heart tube differs in several respects from that of a technical peristaltic pump. Some of these data suggest that embryonic heart tubes work as valveless ''Liebau pumps.'' In the present study, a review is given on the evolution of the two above-mentioned theories of early cardiac pumping mechanics. We discuss pros and cons for both of these theories. We show that the tubular embryonic heart works neither as a technical peristaltic pump nor as a classic Liebau pump. The question regarding how the embryonic heart tube works still awaits an answer.
Pulmonary nodules were detected reliably at CT with 50 mA and pitch of 2 or with 25 mA and a pitch of 1. However, further reduction of the dose to that used at chest radiography was associated with a significant decrease in the number of nodules 5 mm or smaller that were detected, possibly due to artifacts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.