Multimodal Shortwave Infrared Imaging for Visualization of Injection Laryngoplasty

Injection laryngoplasty relies on accurate placement of filler, which can be difficult to visualize in the visible light spectrum (400-700 nm). Shortwave infrared (SWIR, 1000-2000 nm) wavelengths offer advantages due to increased penetration depth and reduced scattering. The study aims to perform a multispectral characterization of the larynx in the SWIR and to provide accurate visualization of injection laryngoplasty via SWIR imaging techniques.

Basic science.

Laboratory.

Larynges were prepared from fresh porcine samples and preserved human cadaveric specimens. Using a custom SWIR imaging system, multispectral imaging was conducted on porcine and human larynges at 1050, 1200, 1300, 1450, 1550, and 1650 nm. Following injection laryngoplasty with common injection agents (saline, carboxymethylcellulose gel, and calcium hydroxyapatite sphere suspension), larynges were imaged with different SWIR imaging modalities: reflection imaging and fluorescence imaging (798 nm excitation).

Multispectral imaging of the larynx revealed a significant increase in contrast between the vocal fold stratified squamous epithelium and adjacent respiratory mucosa at 1550 nm compared to visible light. With injection laryngoplasty, saline and superficial carboxymethylcellulose gel injections were successfully visualized and localized at 1550 nm. Calcium hydroxyapatite sphere suspension had SWIR fluorescence properties due to hydroxyapatite, allowing visualization and material localization during injection.

Multimodal SWIR imaging can successfully provide accurate visualization of filler materials during injection laryngoplasty. This novel visualization technique opens the path toward precision-guided surgical techniques in laryngology.