Middle ear effusions (MEEs) are accumulated middle ear secretions or fluid behind the eardrum during otitis media (OM). A portable, handheld OCT system was developed to non-invasively investigate various optical scattering properties of MEEs in pediatric subjects. Furthermore, clinically relevant parameters of MEEs, including viscosity and bacterial load, were measured from the extracted MEEs after the surgical procedure to treat OM. In vivo OCT images of the middle ear prior to the surgery, OCT images of the extracted MEEs, and biological parameters were correlated to determine the relationship between the optical signatures in MEEs and the clinical findings of OM.
Significance: Optical coherence tomography (OCT) offers high spatial resolution and contrast for imaging intraoral structures, yet few studies have investigated its clinical feasibility for dental plaque and gingiva imaging in vivo. Furthermore, the accessibility is often limited to anterior teeth due to bulky imaging systems and probes.
Aim: A custom-designed, handheld probe-based, spectral-domain OCT system with an interchangeable attachment was developed to assess dental plaque and gingival health in a clinical setting.
Approach: Healthy volunteers and subjects with gingivitis and sufficient plaque were recruited. The handheld OCT system was operated by trained dental hygienists to acquire images of dental plaque and gingiva at various locations and after one-week use of oral hygiene products.
Results: The handheld OCT can access premolars, first molars, and lingual sides of teeth to visualize the plaque distribution. OCT intensity-based texture analysis revealed lower intensity from selected sites in subjects with gingivitis. The distribution of the dental plaque after one-week use of the oral hygiene products was compared, showing the capability of OCT as a longitudinal tracking tool.
Conclusions: OCT has a strong potential to display and assess dental plaque and gingiva in a clinical setting. Meanwhile, technological challenges remain to perform systematic longitudinal tracking and comparative analyses.
Significance: Recent advances in nonlinear optics in neuroscience have focused on using two ultrafast lasers for activity imaging and optogenetic stimulation. Broadband femtosecond light sources can obviate the need for multiple lasers by spectral separation for chromatically targeted excitation.
Aim: We present a photonic crystal fiber (PCF)-based supercontinuum source for spectrally resolved two-photon (2P) imaging and excitation of GCaMP6s and C1V1-mCherry, respectively.
Approach: A PCF is pumped using a 20-MHz repetition rate femtosecond laser to generate a supercontinuum of light, which is spectrally separated, compressed, and recombined to image GCaMP6s (930 nm excitation) and stimulate the optogenetic protein, C1V1-mCherry (1060 nm excitation). Galvanometric spiral scanning is employed on a single-cell level for multiphoton excitation and high-speed resonant scanning is employed for imaging of calcium activity.
Results: Continuous wave lasers were used to verify functionality of optogenetic activation followed by directed 2P excitation. Results from these experiments demonstrate the utility of a supercontinuum light source for simultaneous, single-cell excitation and calcium imaging.
Conclusions: A PCF-based supercontinuum light source was employed for simultaneous imaging and excitation of calcium dynamics in brain tissue. Pumped PCFs can serve as powerful light sources for imaging and activation of neural activity, and overcome the limited spectra and space associated with multilaser approaches.
KEYWORDS: Optical coherence tomography, In vivo imaging, Bacteria, Image analysis, Pathogens, Resistance, 3D image processing, Stereoscopy, Human subjects, Luminescence
Mechanical ventilation is a critical intervention given to intensive care unit (ICU) patients who need airway support. However, this intervention with an endotracheal tube (ETT) is associated with complications such as ventilator-associated pneumonia (VAP). VAP is reported to develop within 48 hours after intubation and is associated with a mortality rate between 20 to 50%. The formation of bacterial biofilms within these ETT tubes provides a niche for infectious bacteria to become resistant to antibiotics. Suctioning of the ETT is believed to prevent airway colonization by pathogens, reduce resistance to airflow, and decrease biofilm formation. However, reports have shown that standard-of-care suctioning is not adequate to eliminate secretions from the ETT, and additional measures aiming to reduce the formation of ETT biofilms have been proposed to reduce VAP. We have recently demonstrated the use of catheter-based 3-D OCT imaging to identify the presence of in vivo biofilms within the ETTs of intubated human subjects in the ICU. In this study, we quantify the volume of mucus and biofilm in ETTs in intubated ICU patients using 3-D OCT, and define the efficacy of suctioning. Longitudinal OCT imaging was performed daily before and after suctioning at approximately 24-hour intervals until extubation. Extubated ETTs were subsequently imaged for further analysis. OCT image analysis results were correlated with clinical data and fluorescence microscopy/Gram stain images to verify the presence of bacteria and biofilm. In vivo catheter-based 3-D OCT offers the potential to rapidly determine the efficacy of ETT suctioning in order to effectively compare suctioning and brushing strategies in an effort to reduce the incidence of VAP.
A biological sample consists of a variety of complex biomolecules, and fluorescence microscopy enables visualization of specific molecules at the sub-cellular level. However, these fluorescence techniques require certain fluorescence dyes to label the sample, and the fluorophores raise serious problems such as photo toxicity and photobleaching which could affect biological functionality in living systems. Advanced label-free optical imaging techniques based on nonlinear optical phenomena overcome these limitations of fluorescence microscopy. We have developed a novel label-free multimodal multiphoton nonlinear optical imaging system based on a near-IR femtosecond laser with photonic crystal fiber and pulse shaper. This highly integrated system offers numerous label-free techniques including third harmonic generation, three-photon excited fluorescence, second harmonic generation, two-photon excited fluorescence, fluorescence lifetime imaging, and broadband coherent anti-Stokes Raman scattering microspectroscopy in one platform. All of the nonlinear signals are spectrally separated by dichroic filters and simultaneously measured by photomultiplier tubes. Moreover, this system includes phase-variance optical coherence tomography as well to enable vascular imaging. We have applied our system to investigate processes in numerous biological samples. Our imaging technique is highly integrated and time efficient to generate big data, offering an array of biomolecular information at one time without staining, three-dimensional sub-micron resolution with deeper penetration, and less photodamage. The big data output from this system is analyzed by multivariate analysis such as principal component analysis and hierarchical cluster analysis. Therefore, this novel technology and methodology will have a great impact on fast in vivo label-free biomedical imaging as a big data generator.
Approximately 29 million Americans have diabetes, and 86 million are living with prediabetes, increasing the risk of developing type 2 diabetes. Complications of wound healing in diabetic patients represent a significant health problem. Impaired diabetic wound healing is characterized by reduced collagen production and diminished angiogenesis. During the proliferative phase of wound healing, the injured tissue undergoes angiogenesis, re-epithelialization, and fibroplasia. Monitoring the development of new blood vessels, metabolic changes, and collagen deposition, is critical to elucidate the process of diabetic wound healing and to improve the development of therapeutic drugs. This study employs a custom-built multimodal microscope where Optical Coherence Tomography Angiography (OCTA) is used for studying neovascularization, Fluorescence Lifetime Imaging Microscopy (FLIM) for NADH/FAD assessment, Second Harmonic Generation (SHG) microscopy for analyzing collagen deposition, and Coherent anti-Stoke’s Raman Scattering (CARS) microscopy for visualizing water/lipid distribution, all together to non-invasively follow closure of a skin wound in healthy diabetic (db/db) mice treated with placebo and angiogenesis-promoting topical formulation (GlaxoSmithKline). The (db/db) mouse model presents hyperglycemia, obesity, and delayed wound healing that is pathologically similar to human type 2 diabetes mellitus. In this ongoing study, the animals are treated once daily for 14 days after wounding. Images of the wound and surrounding areas are taken at different time points for 28 days. In this experiment, the wound healing process is investigated to gain deeper understanding of the drug mechanism. The capability to non-invasively monitor wound healing mechanisms can become a valuable tool in development of new drug compounds for diabetic wound care.
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