Beckman Laser Institute and Medical Clinic

Cartilage provides critical structural support for the upper airway and facial framework, and its reshaping is central to reconstructive and aesthetic procedures in the head and neck. While a range of non-scalpel techniques have been explored as minimally invasive approaches to modifying cartilage shape, achieving deformation without compromising tissue integrity remains a challenge. Electromechanical reshaping (EMR) offers a promising, minimally invasive approach to cartilage modification but is similarly limited by tissue injury that compromises cellular viability. This study investigates a pulsed EMR strategy designed to address these limitations and evaluates its feasibility using optical imaging in ex vivo rabbit septal cartilage.

The paper presents an approach to laser treatment for a wide range of conditions using laser tissue modification through non-ablative thermomechanical action and the creation of microdefects, including gas bubbles, microcracks, micropores, and denatured micro zones. Microdefects can be temporary or permanent and control the physicochemical and mechanical properties of tissues, facilitating their modification aimed at restoring the compliance of calcified arteries and regenerating damaged articular cartilage. Microdefects and thermomechanical effects promote stress relaxation and intercellular interactions through the generation and transfer of signaling molecules, thereby regulating cellular nutrition and metabolism. A theoretical model has been developed based on a sequence of processes, including tissue heating under spatiotemporally modulated laser radiation, local rupture of chemical bonds leading to the formation of microdefects and thermomechanical stresses. Backscattered light measurements are used to monitor the formation of microdefects to develop a real-time feedback system to ensure the effectiveness and safety of laser therapy.

In this talk, I will review the various material platforms (metallic, dielectric, and compound structures) and geometric platforms which have been utilized in “meta”-optical fiber devices to date. I will present our recent development of “Meta”-optical fiber, an advanced optical fiber integrated with emerging metasurface concepts. I will present the development of ultrathin optical metalens which is cascaded on the facet of optical fiber that enables advanced optical functions such as light focusing. I will also discuss the ability to develop tunable meta-optical fiber for advanced beam steering and dynamic focusing, and their potential application for biomedical imaging. These advanced “meta”-optical fibers open a pathway to revolutionary in-fiber optical imaging/endoscopy, biomedical imaging, lasers/spectroscopies, and optical/quantum communication devices.

Background/Objectives: Cilia are hair-like organelles with various mechanosensory and chemosensory functions. In particular, motile cilia generate directional fluid flow important for multiple processes. Motile ciliopathies have serious clinical implications, including developmental and respiratory disorders. Evaluating the most suitable imaging methods for studying ciliary structure and function has great clinical significance. Methods: Here, we provide an overview of ciliary function, imaging modalities, and applications in ciliopathic diseases. Results: Optical imaging has become a crucial tool for studying ciliary structure and function, providing high-resolution, non-invasive imaging capabilities that are valuable for in vivo applications. Optical coherence tomography (OCT) is well suited for the visualization of ciliary anatomy and quantitative studies of microfluidic flow. Conclusions: A deeper understanding of ciliary biology can lead to novel approaches in diagnosing, treating, and monitoring ciliopathies, contributing to more effective and individualized care.

We propose protoacoustic radiography (PAR), an imaging modality combining proton excitation and acoustic detection for three-dimensional (3D) imaging from a single proton projection. PAR avoids the effect of multiple Coulomb scattering in imaging by detecting ultrasound. Proton-induced acoustic waves propagate spherically, enabling 3D imaging from a single projection. Additionally, the distinctive feature of proton beams-concentrating energy deposition primarily at the Bragg peak-allows for precise depth-selectivity through proton energy tuning. We performed PAR using clinical proton machines, and our results demonstrate the capability of PAR to reconstruct targets at various depths (between ∼20 and 23 cm) with an axial resolution of 1.3 mm by fully leveraging the Bragg peak and by tuning the kinetic energy of the proton beam. PAR offers opportunities for precise structural determination with protons both in biomedicine and nondestructive testing.

Dynamic Light Scattering Imaging (DLSI) quantifies fluid flow and scattering by estimating correlation time and scattering ratios. This study demonstrates DLSI’s sensitivity to volumetric flow and flow dynamics, optimizing parameter settings for biomedical imaging applications.

There are important limitations to the current diagnostic tools for obstructive sleep apnea (OSA). The limitations warrant the development of a more accurate, minimally invasive, and objective tool to better characterize upper airway airflow obstruction during sleep. Swept-source optical coherence tomography (OCT) as a range-finding technique was utilized for upper airway volumetric reconstruction. An acousto-optic modulator was integrated into the OCT system for extending the imaging range to be suitable for the typical diameter of the upper airway. High spatial resolution images were acquired at and translated at before manual segmentation for three-dimensional (3D) reconstruction and numerical analysis. The Lattice-Boltzmann method as a computational fluid dynamics (CFD) technique was utilized to pinpoint the precise locations of turbulent airflow in the airspace. Upper airway OCT imaging of a 28-year-old individual with sleep disorder breathing was obtained during awake and sleep periods. The volumetric structure and 3D reconstruction of the upper airway through a micrometer-resolution optical imaging approach were successfully demonstrated. Cross-sectional volumetric changes from awake to sleep periods were calculated, and the greatest airway obstruction was observed at the level of the oropharynx. In addition to CFD analysis, measuring airflow pressure differences along the upper airway aided in accurately localizing the dominant sites of obstruction during sleep. The combination of the proposed OCT imaging system with 3D remodeling and CFD analysis led to accurate reconstruction of the upper airway and identification of obstruction sites during sleep. This technology can improve surgical decision-making and outcomes in OSA.

Mutations in dynamin 2 (DNM2) have been associated with two distinct movement disorders: Charcot-Marie-Tooth neuropathies (CMT) and centronuclear myopathy (CNM). Most of these mutations are clustered in the pleckstrin homology domain (PHD), which engages in intramolecular interactions that limit dynamin self-assembly and GTPase activation. CNM mutations interfere with these intramolecular interactions and suppress the formation of the autoinhibited state. CMT mutations are located primarily on the opposite surface of the PHD, which is specialized for phosphoinositide binding. It has been speculated that the distinct locations and interactions of residues mutated in CMT and CNM explain why each set of mutations causes either one disease or the other, despite their close proximity within the PHD sequence. We previously reported that at least one CMT-causing mutant, lacking residues 555DEE557 (ΔDEE), displays the same inability to undergo autoinhibition as observed in CNM-linked mutants. Here, we show that both the DNM2ΔDEE and CNM-linked DNM2A618T mutants form larger and more stable structures on the plasma membrane than that of wild-type DNM2 (DNM2WT). However, DNM2A618T forms cytoplasmic inclusions at concentrations lower than those of either DNM2WT or DNM2ΔDEE, suggesting that CNM-linked mutations confer more severe gain-of-function properties than the ΔDEE mutation.

We introduce a method utilizing single laser-generated cavitation bubbles to stimulate cellular mechanotransduction in dermal fibroblasts embedded within 3D hydrogels. We demonstrate that fibroblasts embedded in either amorphous or fibrillar hydrogels engage in Ca2+ signaling following exposure to an impulsive mechanical stimulus provided by a single 250 µm diameter laser-generated cavitation bubble. We find that the spatial extent of the cellular signaling is larger for cells embedded within a fibrous collagen hydrogel as compared to those embedded within an amorphous polyvinyl alcohol polymer (SLO-PVA) hydrogel. Additionally, for fibroblasts embedded in collagen, we find an increased range of cellular mechanosensitivity for cells that are polarized relative to the radial axis as compared to the circumferential axis. By contrast, fibroblasts embedded within SLO-PVA did not display orientation-dependent mechanosensitivity. Fibroblasts embedded in hydrogels and cultured in calcium-free media did not show cavitation-induced mechanotransduction; implicating calcium signaling based on transmembrane Ca2+ transport. This study demonstrates the utility of single laser-generated cavitation bubbles to provide local non-invasive impulsive mechanical stimuli within 3D hydrogel tissue models with concurrent imaging using optical microscopy. Statement of significanceCurrently, there are limited methods for the non-invasive real-time assessment of cellular sensitivity to mechanical stimuli within 3D tissue scaffolds. We describe an original approach that utilizes a pulsed laser microbeam within a standard laser scanning microscope system to generate single cavitation bubbles to provide impulsive mechanostimulation to cells within 3D fibrillar and amorphous hydrogels. Using this technique, we measure the cellular mechanosensitivity of primary human dermal fibroblasts embedded in amorphous and fibrillar hydrogels, thereby providing a useful method to examine cellular mechanotransduction in 3D biomaterials. Moreover, the implementation of our method within a standard optical microscope makes it suitable for broad adoption by cellular mechanotransduction researchers and opens the possibility of high-throughput evaluation of biomaterials with respect to cellular mechanosignaling.

Chlorine exposure can cause severe airway injuries. While the acute effects of chlorine inhalation are well-documented, the structural changes resulting from the post-acute, high-level chlorine exposure remain less understood. Airway sloughing is one of the standards for doctors to evaluate the lung function. Here, we report the application of a high-resolution swept-source optical coherence tomography system to investigate the progression of injury based on airway sloughing evaluation in a chlorine inhalation rabbit model. This system employs a 1.2 mm diameter flexible fiberoptic endoscopic probe via an endotracheal tube to capture in vivo large airway anatomical changes before and as early as 30 min after acute chlorine exposure. We conducted an animal study using New Zealand white rabbits exposed to acute chlorine gas (800 ppm, 6 min) during ventilation and monitored them using optical coherence tomography (OCT) for 6 h. To measure the volume of airway sloughing induced by chlorine gas, we utilized deep learning for the segmentation task on OCT images. The results showed that the volume of chlorine induced epithelial sloughing on rabbit tracheal walls initially increased, peaked around 30 min, and then decreased. Furthermore, we utilized a spectral encoded interferometric microscopy system to study ex vivo airway cilia beating dynamics based on Doppler shift, aiding in elucidating how chlorine gas affects cilia beating function. Cilia movability and beating frequency were decreased because of the epithelium damage. This quantitative approach has the potential to enhance the diagnosis and monitoring of injuries from toxic gas inhalation and to evaluate the efficacy of antidote treatments for these injuries.