Observation and density estimation of a large number of skin capillaries using wide-field portable video capillaroscopy and semantic segmentation

Significance

Skin capillaries are non-invasively observable; their structure and blood flow can reflect tissue and systemic conditions. Quantitative analysis of video-capillaroscopy images yields novel diagnostic methods. Because the capillary structure is heterogeneous, analyzing more capillaries can increase the evaluation reliability.

Aim

We developed a system that can observe and quantify numerous capillaries and verified the performance on human skin.

Approach

We developed a portable video-capillaroscope with a spatial resolution higher than 3.5    μ m and a wide field of view (7.4    mm × 5.5    mm ) and a method to evaluate capillary numbers and areas using U-Net. The model was trained and tested with 22 and 11 cropped images (2.4    mm × 1.9    mm ) obtained from 11 participants, respectively. They were then applied to the 7.2    mm × 5.3    mm images from four participants. Segmentation results were compared to ground-truth at the pixel level and capillary-region level.

Results

Over 1000 capillaries were simultaneously observed using the proposed system. Although pixel-level segmentation performance was low [intersection over union (IoU) = 24.5%], the number and area could be estimated. These values differed among four participants and seven sites, and they changed after skin barrier destruction.

Conclusions

The proposed system allows for observing and quantifying numerous skin capillaries simultaneously, suggesting its potential for evaluating tissue and systemic conditions.

Three-dimensional gait analysis of the effect of directional steering on gait in patients with Parkinson's disease

INTRODUCTION

Deep Brain Stimulation (DBS) is an option to treat advanced Parkinson's Disease (PD), but can cause gait disturbance due to stimulation side efffects. This study aims to evaluate the objective effect of directional current steering by DBS on gait performance in PD, utilizing a three-dimensional gait analysis system.

METHODS

Eleven patients diagnosed with PD and were implanted with directional lead were recruited. The direction of the pyramidal tract (identified by the directional mode screening) was set as 0°. Patients performed the six-meter-walk test and the time up-and-go (TUG) test while an analysis system recorded gait parameters utilizing a three-dimensional motion capture camera. The gait parameters were measured for the baseline, the directional steering at eight angles (0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°), and the conventional ring mode with 1, 2, and 3 mA. Pulse width and frequency were fixed. Placebo stimulation (0 mA) was used for a control.

RESULTS

Eleven patients completed the study. No significant difference were observed between gait parameters during the directional, baseline, placebo, or ring modes during the six-meter-walk test (p > 0.05). During the TUG test, stride length was significantly different between 0° and other directions (p < 0.001), but no significant differences were observed for the other gait parameters. Stride width was non-significantly narrower in the direction of 0°.

CONCLUSION

Controlling stimulation using directional steering may improve gait in patients with PD, while avoiding pyramidal side effects.

Force applied to a single molecule at a single nanogate molecule filter

We have investigated the origin of molecule filtering system based on a chemical potential barrier produced by thermodynamically driven molecular flow in a nanoscopic space at nanogates. Single molecule tracking experiments prove that the highly localized potential barrier allows for selective manipulation of the target molecule. We propose the presence of a force, a few fN per molecule, to decelerate the molecule's movement at the nanogate, which is comparable to or larger than the force applied by conventional electrophoretic operation. The present force can be tuned by changing the nanogate width at the nanometre level. These findings allow us to propose an accurate design of novel devices for molecular manipulation on an ultra small scale using a very small number of molecules without any external biases.

Segregation of molecules in lipid bilayer spreading through metal nanogates

A new methodology for nanoscopic molecular filtering was developed using a substrate with a periodic array of metallic nanogates with various widths between 75 and 500 nm. A self-spreading lipid bilayer was employed as the molecular transport and filtering medium. Dye-labeled molecules doped in the self-spreading lipid bilayer were filtered after the spreading less than a few tens of micrometers on the nanogate array. Quantitative analysis of the spreading dynamics suggests that the filtering effect originates from the formation of the chemical potential barrier at the nanogate region, which is believed to be due to structural change such as compression imposed on the spreading lipid bilayer at the gate. A highly localized chemical potential barrier affects the ability of the doped dye-labeled molecules to penetrate the gate. The use of the self-spreading lipid bilayer allows molecular transportation without the use of any external field such as an electric field as is used in electrophoresis. The present system could be applied micro- and nanoscopic device technologies as it provides a completely nonbiased filtering methodology.

Observation of a small number of molecules at a metal nanogap arrayed on a solid surface using surface-enhanced Raman scattering

In situ Raman spectroscopic measurements with 785 nm excitation were carried out in aqueous solutions containing bipyridine derivatives. Intense Raman signals were observed when the Ag dimer structure was optimized. The SERS activity was dependent upon on the structure of the Ag dimer with a distinct gap distance, suggesting that the intense SERS originates from the gap part of the dimer. Characteristic time-dependent spectral changes were observed. Not only a spectrum which was the superposition of two bipyridine spectra but also spectra which can be assigned to one of the bipyridine derivatives were frequently observed. Observation using solutions with different concentrations proved that the spectra originated from very small numbers of molecules at the active SERS site of the dimer.

Controlling molecular diffusion in self-spreading lipid bilayer using periodic array of ultra-small metallic architecture on solid surface

Diffusion of target molecules incorporated in the self-spreading lipid bilayer was controlled by the introduction of periodic array of metallic architecture on solid surface. Retardation of the progress of target molecules became significant when the size of gap between small metal architectures was less than a few hundred nanometers. The self-spreading dynamics of the lipid bilayer depending on the size of the small gap were analyzed semiquantitatively. Estimated change in the driving force of the spreading layer suggests that highly localized compression of the spreading layer causes selective segregation of molecules.

Control of near-infrared optical response of metal nano-structured film on glass substrate for intense Raman scattering

Near-infrared SERS activity of the Ag film under electric polarization was evaluated in aqueous solution containing 1 mM glutamic acid. Spectra were obtained in situ from the near infrared laser Raman microscope system with an excitation wavelength of 785 nm. Intensity of the SERS increased significantly upon application of an external electric field to the film. Empirical signal enhancement factor, which was determined from the peak integration ratio of the SERS vibration to the unenhanced signal from the solution of a defined sample concentration, was estimated to be in the range between 10(5) and 10(9). The evolution of the scattering signal was not observed in the absence of an applied external field. Under the present conditions, the SERS intensity was fully controlled by the applied field and the time. Relatively strong enhancement observed at the present system could be attributable to closed-packed particulate structure characterized by the diameters of approximately 20-90 nm on the Ag film. Raman images prove that the scattering signals are highly localized at the specific sites on the films showing possible achievement of relatively larger enhancement more than 10(12). Importance of the control of the size and inter-particle distance for intense Raman scattering was proved by the preparation of the well-ordered chained Ag dot array showing stronger SERS signals than those at the Ag films.