A narrative review on the use of near-infrared spectroscopy to monitor bladder volume and validation approaches.

Background And Objective: Current guidelines for patients with neurogenic bladder (NB) dysfunction suggest the use of self-intermittent catheterization with adherence to catheterization timers. Due to biorhythmic variability, unpredictable voiding times may occur. As a result, many patients abstain from extended social or work activities, turn to more secluded lifestyles, and generally experience a decrease in quality of life.

Hybrid Bladder Phantom to Validate Next-Generation Optical Wearables for Neurogenic Bladder Volume Monitoring.

Purpose: The development of optics-based wearables for bladder volume monitoring has emerged as a significant topic in recent years. Given the innovative nature of this technology, there is currently no bladder phantom available to effectively validate these devices against more established gold standards, such as ultrasound. In this study, we showcase and demonstrate the performance of our hybrid bladder phantom by using an optical device and making comparisons with ultrasound.

Spectral correction of light emitting diodes enables accurate hydration ratio calculation using narrowband diffuse reflectance spectroscopy.

Significance: Light emitting diodes (LEDs) are commonly utilized for tissue spectroscopy due to their small size, low cost, and simplicity. However, LEDs are often approximated as single-wavelength devices despite having relatively broad spectral bandwidths. When paired with photodiodes, the wavelength information of detected light cannot be resolved.

Smartphone-based single snapshot spatial frequency domain imaging.

We report a handheld, smartphone-based spatial frequency domain imaging device. We first examined the linear dynamic range of the smartphone camera sensor. We then calculated optical properties for a series of liquid phantoms with varying concentrations of nigrosin ink and Intralipid, demonstrating separation of absorption and scattering.

Accurately calibrated frequency domain diffuse optical spectroscopy compared against chemical analysis of porcine adipose tissue.

Frequency domain diffuse optical spectroscopy (fdDOS) is a noninvasive technique to estimate tissue composition and hemodynamics. While fdDOS has been established as a valuable modality for clinical research, comparison of fdDOS with direct chemical analysis (CA) methods has yet to be reported. To compare the two approaches, we propose a procedure to confirm accurate calibration by use of liquid emulsion and solid silicone phantoms.

Narrowband diffuse reflectance spectroscopy in the 900-1000 nm wavelength region to quantify water and lipid content of turbid media.

We report a narrow wavelength band diffuse reflectance spectroscopy (nb-DRS) method to determine water and fat ratios of scattering media in the 900-1000 nm range. This method was shown to be linearly correlated with absolute water and fat concentrations as tested on a set of turbid emulsion phantoms with a range of water and lipid compositions. Robustness to scattering assumptions was demonstrated and compared against measured scattering by a frequency-domain photon migration system.

Monocular 3D Probe Tracking for Generating Sub-Surface Optical Property Maps From Diffuse Optical Spectroscopic Imaging.

Objective: Diffuse optical spectroscopic imaging (DOSI) is a promising biophotonic technology for clinical tissue assessment, but is currently hampered by difficult wide area assessment. A co-integrative optical imaging system is proposed for dense sub-surface optical property spatial assessment.

Methods: The proposed system fuses a co-aligned set of camera frames and diffuse optical spectroscopy measurements to generate spatial sub-surface optical property maps.

Non-invasive Dual-Channel Broadband Diffuse Optical Spectroscopy of Massive Hemorrhage and Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) in Swine.

Objective: To quantitatively measure tissue composition and hemodynamics during resuscitative endovascular balloon occlusion of the aorta (REBOA) in two tissue compartments using non-invasive two-channel broadband diffuse optical spectroscopy (DOS).

Methods: Tissue concentrations of oxy- and deoxyhemoglobin (HbO2 and HbR), water, and lipid were measured in a porcine model (n = 10) of massive hemorrhage (65% total blood volume over 1 h) and 30-min REBOA superior and inferior to the aortic balloon.

Results: After hemorrhage, hemoglobin oxygen saturation (StO2 = HbO2/[HbO2 + HbR]) at both sites decreased significantly (-29.