Dynamic analysis for mental sweating of a group of eccrine sweat glands on a human fingertip by optical coherence tomography.

BACKGROUND: An important function of skin physiology is mental sweating, where sweating is accelerated via the sympathetic nerve by mental or physical stress externally applied to a volunteer. AIM: Activity of the sympathetic nerve (ASN) is evaluated by quantitative measurement of mental sweating. MATERIAL AND METHODS: Optical coherence tomography (OCT) is highly potential for in vivo observation of human sweating dynamics which affects ASN. We demonstrate dynamic OCT analysis of mental sweating of a group of eccrine sweat glands. The sweating dynamics is tracked simultaneously for 19 sweat glands by time-sequential piled-up en-face OCT images with the frame spacing of 3.3 s. The en-face OCT images of the spiral lumen of the eccrine sweat gland are constructed by data acquisition of the 128 B-mode OCT images. RESULTS: It is thus found that the response to mental stress is different for each sweat gland even though the sweat glands are adjacent to each other. Such strong non-uniformity is observed in mental sweating where the amount of excess sweat is different for each sweat gland although the sweat glands are adjacent to each other. DISCUSSION: The non-uniformity should be necessary to adjust as precisely the total amount of excess sweat as possible through the sympathetic nerve in response to strength of the stress.

Dynamic analysis of internal and external mental sweating by optical coherence tomography.

Mental sweating is human sweating that is accelerated via the sympathetic nerve by application of mental or physical stress. In the neurosciences, there is keen interest in this type of sweating, because the amount of sweat in response to a stress applied to a volunteer directly reflects activity of the sympathetic nerve. It is therefore of particular value that optical coherence tomography (OCT) can provide clear in vivo imaging of the spiral lumen of an eccrin sweat gland in the epidermis with a spatial resolution around 10 mum. We demonstrate dynamic OCT of mental sweating of an eccrin sweat gland on a human fingertip, where the sweating dynamics can be tracked by time-sequential OCT images with a frame spacing of one second. An instantaneous amount of sweat stored in the spiral lumen is evaluated quantitatively in each OCT image, resulting in time variation measurements of excess sweat in response to mental or physical stress. In the dynamic OCT of mental sweating, as demonstrated here, we note for the first time internal sweating without ejection of excess sweat from the spiral lumen to the skin surface. Internal sweating has not been previously detected without the availability of our dynamic OCT technique. Until now, it has been commonly accepted that sweating is always accompanied with ejection of excess sweat to the skin surface. On the basis of our findings reported here, this type of sweating should now be referred to as external sweating. In this study, we demonstrate that internal sweating occurs more often in the case where mental stress is applied to a volunteer, and that it is more useful for evaluation of activity of the sympathetic nerve. The dynamic OCT for both external and internal sweating is demonstrated.

Imaging of in vitro chicken leg using time-resolved near-infrared optical tomography.

Near-infrared optical imaging gains much attention because of its noninvasiveness and deep penetration depths into tissue. Here, we report near-infrared optical tomographic imaging of an in vitro chicken leg from time-resolved measurements. The in vitro chicken leg, dipped in a cylindrical container filled with diluted Intralipid-10% solution, was imaged with a multichannel time-resolved imaging system. A two-dimensional reconstruction algorithm based on a modified generalized pulse spectrum technique has been developed to reconstruct the images of both the absorption and reduced scattering coefficients simultaneously and quickly. The results demonstrate that a simultaneous reconstruction of absorption and reduced scattering coefficients from time-resolved measurement has a potential to reveal the changes in the optical properties associated with not only the physiological information but also the anatomical structure of the organ.

Low-coherence interferometer system for the simultaneous measurement of refractive index and thickness.

We have developed a low-coherence interferometer system used for the simultaneous measurement of refractive index n and thickness t of transparent plates. Both the phase index n(p) and group index n(g) can be determined automatically in a wide thickness range of from 10 microm to a few millimeters. Two unique techniques are presented to measure n(p), n(g), and t simultaneously. One allows us to determine n(p), n(g), and t accurately by using a special sample holder, in which the measurement accuracy is 0.3% for the thickness t above 0.1 mm. In the other technique the chromatic dispersion delta n of index is approximately expressed as a function of (n(p) - 1) on the basis of measured values of n(p) and n(g) for a variety of materials, and then the simultaneous measurement is performed with a normal sample holder. In addition, a measurement accuracy of less than 1% is achieved even when the sample is as thin as 20 microm. The measurement time is also 3 min or more.