Cranial nerve contrast using nerve-specific fluorophores improved by paired-agent imaging with indocyanine green as a control agent

Abstract

Nerve preservation during surgery is critical because damage can result in significant morbidity. This remains a challenge especially for skull base surgeries where cranial nerves (CNs) are involved because visualization and access are particularly poor in that location. We present a paired-agent imaging method to enhance identification of CNs using nerve-specific fluorophores. Two myelin-targeting imaging agents were evaluated, Oxazine 4 and Rhodamine 800, and coadministered with a control agent, indocyanine green, either intravenously or topically in rats. Fluorescence imaging was performed on excised brains ex vivo, and nerve contrast was evaluated via paired-agent ratiometric data analysis. Although contrast was improved among all experimental groups using paired-agent imaging compared to conventional, solely targeted imaging, Oxazine 4 applied directly exhibited the greatest enhancement, with a minimum 3 times improvement in CNs delineation. This work highlights the importance of accounting for nonspecific signal of targeted agents, and demonstrates that paired-agent imaging is one method capable of doing so. Although staining, rinsing, and imaging protocols need to be optimized, these findings serve as a demonstration for the potential use of paired-agent imaging to improve contrast of CNs, and consequently, surgical outcome.

Indocyanine green fluorescence image processing techniques for breast cancer macroscopic demarcation

“…The LR model has been suggested for tissue class prediction 20 , given a certain fluorescence intensity value. This model has been thus far used in visualization of rat orthotopic glioma model 23 , 24 , rat cranial nerve ex-vivo 25 and mouse xenografts in-vivo 26 . We previously used the LR model with fluorescence texture metrics in freshly excised breast-specimens 21 which yielded 83% mean accuracy.…”

Prediction of optimal contrast times post-imaging agent administration to inform personalized fluorescence-guided surgery

“…The contrast is quantified by the contrast-to-variability ratio and the area under the receiver operating characteristic curve (AUROC), parameters that are strongly correlated with the ability of an "ideal observer" to distinguish tumor from normal tissue. 15 Note that this is not necessarily the case for the often-used metric of "tumor-to-background" used in the fluorescence-guided surgery (FGS) literature (though under shot-noise limited cases it is a good estimate-results not shown). The validity of the mathematical model was tested in human cancer xenograft mouse models using three classes of imaging agents (a native ligand peptide-based agent, an antibody mimetic agent, and an antibody agent) and two distinct imaging techniques [common "single-agent" (SA) methods and "paired-agent" (PA) methods 16 ].…”