Bong Kyu Kim

Background: Accurate intraoperative localization of small pulmonary nodules remains challenging. Multimodal optical spectroscopy may provide complementary tissue-level information beyond hemoglobin-dependent contrast. This study evaluated multimodal optical differences between lung cancer and paired normal lung tissues. Methods: Twelve patients undergoing surgical resection of primary lung cancer were prospectively enrolled. Paired ex vivo specimens were collected from tumor and normal lung parenchyma. Optical attenuation was quantified at a fixed wavelength of 638 nm and expressed as optical density (OD). Autofluorescence emission and Raman spectra were acquired under identical excitation conditions using a fiber-optic probe-based system. Optical features were compared between tumor and normal tissues and explored by histological subtype. Results: Twenty-four tumor tissues and 24 paired normal lung tissues were analyzed. Tumor tissues exhibited significantly higher optical attenuation at 638 nm than corresponding normal lung tissues in both adenocarcinoma and squamous cell carcinoma, with no significant difference in OD between subtypes. Autofluorescence intensity was consistently lower in tumor tissues than in normal lung tissues, and adenocarcinoma demonstrated higher fluorescence intensity than squamous cell carcinoma. Raman spectroscopy revealed distinct spectral differences between tumor and normal tissues and demonstrated subtype-associated variations, including relatively stronger phenylalanine- and tyrosine-related bands in adenocarcinoma. Conclusions: Ex vivo multimodal optical analysis revealed reproducible tumor-associated differences in optical attenuation, autofluorescence, and Raman spectral features between lung cancer and normal lung tissues. These findings represent tissue-level optical signatures rather than hemoglobin-free intrinsic absorption and support the potential role of multimodal optical spectroscopy as a complementary approach spectroscopic guidance during lung cancer surgery.

This study investigates a noninvasive continuous glucose monitoring (NI-CGM) system optimized for earlobe application, leveraging the site’s anatomical advantages—absence of bone, muscle, and thick skin—for enhanced optical transmission. The system integrates multimodal sensing, combining near-infrared (NIR) diffuse transmission with temperature and pressure sensors. A novel Multi-Wavelength Slope Efficiency Near-Infrared Spectroscopy (MW-SE-NIRS) method is introduced, enhancing noise robustness through the slope efficiency-based parameterization of NIR signal dynamics. By employing three NIR wavelengths with distinct scattering and absorption properties, the method improves glucose detection reliability, addressing tissue heterogeneity and physiological noise in noninvasive monitoring. To validate the feasibility, a pilot clinical trial enrolled five participants with normal or pre-diabetic glucose profiles. Continuous glucose data capturing pre- and postprandial variations were analyzed using a 1D convolutional neural network (Conv1D). For three subjects under stable physiological conditions, the model achieved 97.0% Clarke error grid (CEG) A-Zone accuracy and a mean absolute relative difference (MARD) of 5.2%. Across all participants, results showed 90.9% CEG A-Zone accuracy and a MARD of 8.4%, with performance variations linked to individual factors such as earlobe thickness variability and physical activity. These outcomes demonstrate the potential of the MW-SE-NIRS system for noninvasive glucose monitoring and highlight the importance of future work on personalized modeling, sensor optimization, and larger-scale clinical validation.

Photoacoustic spectroscopy has been shown to be a promising tool for non-invasive blood glucose monitoring. However, the repeatability of such a method is susceptible to changes in skin condition, which is dependent on hand washing and drying due to the high absorption of infrared excitation light to the skin secretion products or water. In this paper, we present a method to meet the challenges of mid-infrared photoacoustic spectroscopy for non-invasive glucose monitoring. By obtaining the microscopic spatial information of skin during the spectroscopy measurement, the skin region where the infrared spectra is insensitive to skin condition can be locally selected, which enables reliable prediction of the blood glucose level from the photoacoustic spectroscopy signals. Our raster-scan imaging showed that the skin condition for in vivo spectroscopic glucose monitoring had significant inhomogeneities and large variability in the probing area where the signal was acquired. However, the selective localization of the probing led to a reduction in the effects of variability due to the skin secretion product. Looking forward, this technology has broader applications not only in continuous glucose monitoring for diabetic patient care, but in forensic science, the diagnosis of malfunctioning sweat pores, and the discrimination of tumors extracted via biopsy.

We propose an approach to match the resonant characteristics of a photoacoustic cell with that of a microphone in order to enhance the signal-to-noise ratio in the photoacoustic sensor system. The synergetic resonance matching of a photoacoustic cell and a microphone was achieved by observing that photoacoustic cell resonance is merged with microphone resonance, in addition to conducting numerical and analytical simulations. Using this approach, we show that the signal-to-noise ratio was increased 3.5-fold from the optimized to non-optimized cell in the photoacoustic spectroscopy system. The present work is expected to have a broad impact on a number of applications, from improving weak photoacoustic signals in photoacoustic spectroscopy to ameliorating various sensors that use acoustic resonant filters.

We report an enhancement in light emission efficiency of Si nanocrystal (NC) light-emitting diodes (LEDs) by employing 5.5 periods of SiCN/SiC superlattices (SLs). SiCN and SiC layers in SiCN/SiC SLs were designed by considering the optical bandgap to induce the uniform electron sheet parallel to the SL planes. The electrical property of Si NC LED with SiCN/SiC SLs was improved. In addition, light output power and wall-plug efficiency of the Si NC LED with SiCN/SiC SLs were also enhanced by 50% and 40%, respectively. This was attributed to both the formation of two-dimensional electron gas, i.e., uniform electron sheet parallel to the SiCN/SiC SL planes due to the conduction band offset between the SiCN layer and SiC layer, and an enhanced electron transport into the Si NCs due to a lower tunneling barrier height. We show here that the use of the SiCN/SiC SL structure can be very useful in realizing a highly efficient Si NC LED.