Characterization of lamina propria remodeling in pediatric eosinophilic esophagitis using second harmonic generation microscopy.

Eosinophilic esophagitis (EoE) is a chronic inflammatory condition characterized by an intense infiltration of eosinophils into the esophageal epithelium. When not adequately controlled, eosinophilic inflammation can lead to changes in components of the extracellular matrix (ECM) of the lamina propria. Particularly, alterations to the collagen fiber matrix can lead to lamina propria fibrosis (LPF), which plays an important role in the fibrostenotic complications of EoE. Current approaches to assess LPF in EoE are prone to inter-observer inconsistencies and provide limited insight into the structural remodeling of the ECM. An objective approach to quantify LPF can eliminate inter-observer inconsistencies and provide novel insights into the fibrotic transformation of the lamina propria in EoE. Second harmonic generation (SHG) microscopy is a powerful modality for objectively quantifying disease associated alterations in ECM collagen structure that is finding increasing use for clinical research. We used SHG with morphometric analysis (SHG-MA) to characterize lamina propria collagen fibers and ECM porosity in esophageal biopsies collected from children with active EoE (n = 11), inactive EoE (n = 11), and non-EoE (n = 11). The collagen fiber width quantified by SHG-MA correlated positively with peak eosinophil count (r = 0.65, p < 0.005) and histopathologist scoring of LPF (r = 0.52, p < 0.005) in the esophageal biopsies. Patients with active EoE had a significant enlargement of ECM pores compared to inactive EoE and non-EoE (p < 0.005), with the mean pore area correlating positively with EoE activity (r = 0.76, p < 0.005) and LPF severity (r = 0.65, p < 0.005). These results indicate that SHG-MA can be utilized to objectively characterize and provide novel insights into lamina propria ECM structural remodeling in children with EoE, which could aid in monitoring disease progression.

Measurement of rat and human tissue optical properties for improving the optical detection and visualization of peripheral nerves.

Peripheral nerve damage frequently occurs in challenging surgical cases resulting in high costs and morbidity. Various optical techniques have proven effective in detecting and visually enhancing nerves, demonstrating their translational potential for assisting in nerve-sparing medical procedures. However, there is limited data characterizing the optical properties of nerves in comparison to surrounding tissues, thus limiting the optimization of optical nerve detection systems. To address this gap, the absorption and scattering properties of rat and human nerve, muscle, fat, and tendon were determined from 352-2500 nm. The optical properties highlighted an ideal region in the shortwave infrared for detecting embedded nerves, which remains a significant challenge for optical approaches. A 1000-1700 nm hyperspectral diffuse reflectance imaging system was used to confirm these results and identify optimal wavelengths for nerve imaging contrast in an in vivo rat model. Optimal nerve visualization contrast was achieved using 1190/1100 nm ratiometric imaging and was sustained for nerves embedded under ≥600 µm of fat and muscle. Overall, the results provide valuable insights for optimizing the optical contrast of nerves, including those embedded in tissue, which could lead to improved surgical guidance and nerve-sparing outcomes.

Label-free intraoperative nerve detection and visualization using ratiometric diffuse reflectance spectroscopy.

Iatrogenic nerve injuries contribute significantly to postoperative morbidity across various surgical disciplines and occur in approximately 500,000 cases annually in the US alone. Currently, there are no clinically adopted means to intraoperatively visualize nerves beyond the surgeon's visual assessment. Here, we report a label-free method for nerve detection using diffuse reflectance spectroscopy (DRS). Starting with an in vivo rat model, fiber- and imaging-based DRS independently identified similar wavelengths that provided optimal contrast for nerve identification with an accuracy of 92%. Optical property measurements of rat and human cadaver tissues verify that the source of contrast between nerve and surrounding tissues is largely due to higher scattering in nerve and differences in oxygenated hemoglobin content. Clinical feasibility was demonstrated in patients undergoing thyroidectomies using both probe-based and imaging-based approaches where the nerve were identified with 91% accuracy. Based on our preliminary results, DRS has the potential to both provide surgeons with a label-free, intraoperative means of nerve visualization and reduce the incidence of iatrogenic nerve injuries along with its detrimental complications.

Characterization of a reversible thermally-actuated polymer-valve: A potential dynamic treatment for congenital diaphragmatic hernia.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is a fetal defect comprising an incomplete diaphragm and the herniation of abdominal organs into the chest cavity that interfere with fetal pulmonary development. Though the most promising treatment for CDH is via interventional fetoscopic tracheal occlusion (TO) surgery in-utero, it has produced mixed results due to the static nature of the inserted occlusion. We hypothesize that a suitable noninvasively-actuatable, cyclic-release tracheal occlusion device can be developed to enable dynamic tracheal occlusion (dTO) implementation. OBJECTIVE: To conduct an in-vitro proof-of-concept investigation of the construction of thermo-responsive polymer valves designed for targeted activation within a physiologically realizable temperature range as a first step towards potential development of a noninvasively-actuatable implantable device to facilitate dynamic tracheal occlusion (dTO) therapy. METHODS: Six thermo-responsive polymer valves, with a critical solution temperature slightly higher than normal physiological body temperature of 37°C, were fabricated using a copolymer of n-isopropylacrylamide (NIPAM) and dimethylacrylamide (DMAA). Three of the valves underwent ethylene oxide (EtO) sterilization while the other three served as controls for EtO-processing compatibility testing. Thermal response actuation of the valves and their steady-state flow performances were evaluated using water and caprine amniotic fluid. RESULTS: All six valves consisting of 0.3-mole fraction of DMAA were tested for thermal actuation of caprine amniotic fluid flow at temperatures ranging from 30-44°C. They all exhibited initiation of valve actuation opening at ~40°C with full completion at ~44°C. The overall average coefficient of variation (CV) for the day-to-day flow performance of the valves tested was less than 12%. Based on a Student t-test, there was no significant difference in the operational characteristics for the EtO processed versus the non-EtO processed valves tested. CONCLUSIONS: We successfully fabricated and demonstrated physiological realizable temperature range operation of thermo-responsive polymer valves in-vitro and their suitability for standard EtO sterilization processing, a prerequisite for future in-vivo surgical implantation testing.

Molecular imaging of conscious, unrestrained mice with AwakeSPECT.

UNLABELLED: We have developed a SPECT imaging system, AwakeSPECT, to enable molecular brain imaging of untrained mice that are conscious, unanesthetized, and unrestrained. We accomplished this with head tracking and motion correction techniques. METHODS: The capability of the system for motion-corrected imaging was demonstrated with a (99m)Tc-pertechnetate phantom, (99m)Tc-methylene diphosphonate bone imaging, and measurement of the binding potential of the dopamine transporter radioligand (123)I-ioflupane in mouse brain in the awake and anesthetized (isoflurane) states. Stress induced by imaging in the awake state was assessed through measurement of plasma corticosterone levels. RESULTS: AwakeSPECT provided high-resolution bone images reminiscent of those obtained from CT. The binding potential of (123)I-ioflupane in the awake state was on the order of 50% of that obtained with the animal under anesthesia, consistent with previous studies in nonhuman primates. Levels of stress induced were on the order of those seen in other behavioral tasks and imaging studies of awake animals. CONCLUSION: These results demonstrate the feasibility of SPECT molecular brain imaging of mice in the conscious, unrestrained state and demonstrate the effects of isoflurane anesthesia on radiotracer uptake.

Full-field imaging-based instantaneous hyperspectral absolute refractive index measurement.

Multispectral refractometers typically measure refractive index (RI) at discrete monochromatic wavelengths via a serial process. We report on the demonstration of a white light full-field imaging-based refractometer capable of instantaneous multispectral measurement of absolute RI of clear liquid-gel samples across the entire visible light spectrum. The broad optical bandwidth refractometer is capable of hyperspectral measurement of RI in the range 1.30-1.70 between 400 and 700 nm with a maximum error of 0.0036 units (0.24% of actual) at 414 nm for an η=1.50 sample. We present system design and calibration method details as well as results from a system validation sample.

Effect of temperature, pH, and corneal birefringence on polarimetric glucose monitoring in the eye.

Over the last two decades polarimetry has been investigated as a noninvasive alternative for glucose monitoring in support of diabetic patients. In particular, the anterior chamber of the eye containing the fluid known as the aqueous humor has been confirmed to be the optimal sensing site for polarimetric glucose measurements due to its reasonable pathlength (1 cm), low scatter, and minimal depolarization index. In essence, the eye can be thought of as an optical window into the body. In this paper, we will first introduce the key challenges that must be overcome to make the use of polarized light in the eye a viable method for noninvasive glucose monitoring, summarize our work toward this endeavor, and then report on our latest research, namely, the effect of temperature, pH, and corneal birefringence on our polarimetric glucose monitoring system.

Development and calibration of an automated Mueller matrix polarization imaging system.

The high fatality rate associated with the late detection of skin cancer makes early detection crucial in preventing death. The current method for determining if a skin lesion is suspect to cancer is initially based on the patient's and physician's subjective observation of the skin lesion. Physicians use a set of parameters called the ABCD (asymmetry, border, color, diameter) rule to help facilitate diagnosis of potential cancerous lesions. Lesions that are suspicious then require a biopsy, which is a painful, invasive, and a time-consuming procedure. In an attempt to reduce the aforementioned undesirable elements currently associated with skin cancer diagnosis, a novel optical polarization-imaging system is described that has the potential to noninvasively detect cancerous lesions. The described system generates the full 16-element Mueller matrix in less than 70 s. The operation of the system was tested in transmission, specular reflection, and diffuse reflectance modes, using known samples, such as a horizontal linear polarizer, a mirror, and a diffuser plate. In addition, it was also used to image a benign lesion on a human subject. The results of the known samples are in good agreement with their theoretical values with an average accuracy of 97.96% and a standard deviation of 0.0084, using 16 polarization images. The system accuracy was further increased to 99.44% with a standard deviation of 0.005, when 36 images were used to generate the Mueller matrix.