Abstract
Fiber-optics confocal microscopy (FCM) is an emerging imaging technology with various applications in basic research and clinical diagnosis. FCM allows for real-time in situ microscopy of tissue at sub-cellular scale. Recently FCM has been investigated for cardiac imaging, in particular, for discrimination of cardiac tissue during pediatric open-heart surgery. FCM relies on fluorescent dyes. The current clinical approach of dye delivery is based on systemic injection, which is associated with high dye consumption, and adverse clinical events. In this study, we investigated approaches for local dye delivery during FCM imaging based on dye carriers attached to the imaging probe. Using three-dimensional confocal microscopy, automated bench tests, and FCM imaging we quantitatively characterized dye release of carriers composed of open-pore foam only and foam loaded with agarose hydrogel. In addition, we compared local dye delivery with a model of systemic dye delivery in the isolated perfused rodent heart. We measured the signal-to-noise ratio (SNR) of images acquired in various regions of the heart. Our evaluations showed that foam-agarose dye carriers exhibited a prolonged dye release vs. foam-only carriers. Foam-agarose dye carriers allowed reliable imaging of 5–9 lines, which is comparable to 4–8 min of continuous dye release. Our study in the living heart revealed that the SNR of FCM images using local and systemic dye delivery is not different. However, we observed differences in the imaged tissue microstructure with the two approaches. Structural features characteristic of microvasculature were solely observed for systemic dye delivery. Our findings suggest that local dye delivery approach for FCM imaging constitutes an important alternative to systemic dye delivery. We suggest that the approach for local dye delivery will facilitate clinical translation of FCM, for instance, for FCM imaging during pediatric heart surgery.
Highlights
Fiber-optics confocal microscopy (FCM) is based on confocal microscopy, which was invented and patented in the 1950s by Minsky (1961)
FCM has emerged as a tool for basic biomedical research (Bharali et al, 2005; Vincent et al, 2006; Lewandowski et al, 2010) and clinical applications
In these cardiac interventions and many other clinical applications FCM imaging relies on intravenous injection of high-dose fluorescein sodium as a fluorescent marker
Summary
Fiber-optics confocal microscopy (FCM) is based on confocal microscopy, which was invented and patented in the 1950s by Minsky (1961). To conventional confocal microscopy, FCM allows for high-resolution optical imaging at various depths within a specimen. In contrast to conventional confocal microscopic systems FCM systems comprise a coherent fiber-optic bundle with a length of up to several meters. The unique capability of real-time, in situ microscopic imaging has led to development of FCM-based approaches for clinical diagnosis in gastrointestinology (Inoue et al, 2005; Kiesslich and Neurath, 2005; Goetz et al, 2006; Anandasabapathy, 2008), pulmonology (Thiberville et al, 2009; Salaun et al, 2013), and urology (Wu et al, 2011)
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