Masamitsu Haruna

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.

Dynamic Optical Coherence Tomography of Small Arteries and Veins of Human Fingers

It is demonstrated for the first time to our knowledge that the dynamic optical coherence tomography (OCT) can provide us real-time and high-resolution in vivo imaging of pulsation of a small artery of a human finger in synchronization with the heartbeat. The dynamic OCT shows us an interesting phenomenon that the vessel wall thickness (or the tunica-media thickness) is invariant during the pulsation. Furthermore, the dynamic motion of a small vein was observed under the condition where the upper arm of a volunteer is pressed for temporal obstruction of blood flow. The small vein expands gradually due to blood congestion of fingers caused by the obstruction, while the vessel wall thickness reduces remarkably. The dynamic OCT is thus very useful to find new phenomena in dynamic physiology of peripheral vessels, leading to finding out premonitory symptoms of aging of vessels.

Maximum-Intensity-Projection Imaging for Dynamic Analysis of Mental Sweating by Optical Coherence Tomography

Optical coherence tomography (OCT) shows great potential for microscopic observation of human sweating dynamics. It should be a key technology in the development of new techniques for the study of dynamic physiology. In this study, the dynamic motion of eccrin sweat glands is visualized by three-dimensional (3-D) OCT imaging, and a novel 3-D image construction method, using maximum intensity projection (MIP) of B-mode OCT images, is proposed for in vivo dynamic analysis of mental sweating on human fingertips. Time-sequential MIP-OCT images with a frame spacing of 1.4 s provide quantitative analysis of the sweating dynamics, which in turn leads to the evaluation of the activity of the sympathetic nerve. Dynamic changes in the microstructure of eccrin sweat glands can be clearly observed in the 3-D images constructed by volume rendering.

Real-time OCT imaging of laser ablation of biological tissue

During laser ablation of a diseased area, the surrounding tissues and organs suffer serious damage. In order to optimize laser ablation of biological tissues, it is necessary to observe the laser ablation in situ. The real-time imaging of tissue laser ablation is realized in the fusion system of the YAG ablation laser and optical coherence tomography (OCT). A swept-source OCT (SS-OCT) is combined with a YAG-laser ablation system. In this paper, we demonstrate real-time OCT imaging of tissue laser ablation. The fiber-optic swept source OCT (SS-OCT) with 25 frames / s is used for the in situ observation where tissue laser ablation is made continuously by 10-Hz YAG laser pulses. Dynamic analysis for laser ablation, therefore, is made, taking thermal effect into account.

Dynamic Analysis of Eccrin Sweat Glands on Human Fingertips by Optical Coherence Tomography

OCT is highly potential for dynamic analysis of eccrin sweat glands. It is found in our experiment that the spiral lumen of an active sweat gland expands drastically in response to mental stress. Mental-stress-induced sweating is analyzed quantitatively based on time-sequential OCT images.

Dynamic analysis of laser ablation of biological tissue using a real-time OCT

In laser ablation of biological tissues, tomography of the tissue surface is necessary for measurement of the crater depth and observation of the thermal damage of the tissue. Optical coherence tomography (OCT) is a very promising candidate for an in-situ observation of the tissue. We demonstrate here dynamic analysis of tissue laser ablation using a real-time OCT.

Dynamic Imaging of Small Arteries and Veins of Human Fingers by Optical Coherence Tomography

In vivo dynamic OCT imaging of small arteries and veins of human fingers are demonstrated. We can observe pulsation of the artery in synchronization with heartbeat, leading to a screening of aging of blood vessels.

Maximum-intensity-projection images of human sweat glands using optical coherence tomography

We demonstrate for the first time the maximum intensity projection (MIP) for OCT, on the analogy of the X-ray CT, where a spiral duct of sweat glands on human fingertip is observed very clearly. The MIP OCT is a quick 3D-image construction method suitable for dynamic analysis of mental-stress-induced sweating.

Dynamic analysis of a small artery of a human finger by optical coherence tomography

OCT is highly potential for development of a new field of dynamic skin physiology, as recently reported by the authors. In this paper, we demonstrate dynamic analysis of a small artery of a human finger by the SS-OCT. Among the vascular system, only the small artery has two physiological functions both for the elastic artery (like main and middle arteries) and for muscle-controlled one (like arterioles). It, therefore, is important for dynamic analysis of blood flow and circulation. In the time-sequential OCT images obtained with 25 frames/s, it is found that the small artery makes a sharp response to sound stress for contraction and expansion while it continues pulsation in synchronization with the heartbeats. This result indicates that the small artery exhibits clearly the two physiological functions for blood flow and circulation. In response to sound stress, blood flow is controlled effectively by thickness change of the tunica media which consists of five to six layers of smooth muscles. It is thus found that the thickness of the tunica media changes remarkably in response to external stress, reflecting activity of the sympathetic nerve. The dynamic OCT of the small artery presented here will allow us not only to understand the mechanism of blood flow control and also to detect abnormal physiological functions in the whole vascular system.

Dynamic analysis of mental sweating by optical coherence tomography

In the dynamic OCT of mental sweating, we have found internal mental sweating without ejection of excess sweat from the spiral lumen to the skin surface. Internal sweating occurs more often in the case where mental stress is applied to a volunteer, and it is more useful for evaluation of activity of the sympathetic nerve. Furthermore, the MIP imaging has been proposed for quick 3-D imaging of the spiral lumen of sweat glands. Using time-sequential MIP images with the frame spacing as short as 1.4 sec, several sweat glands can be tracked simultaneously to quantify sweating stimulated by a mental stress.