An in vitro experiment for the fundamental research to develop a catheter-based laser vascular-welding device used in aortic dissection was studied. We employed laser vascular-welding by means of combining diode laser irradiation and indocyanine green stain to the dissected vessel surface in a swine aortic dissection model to obtain localized heat generation. We successfully demonstrated laser vascular-welding of this aortic dissection del. The breaking strengths of the welded aortic pieces were measured. The breaking strength of 170 gf/cm² obtained with 425 W/cm² 2.4s irradiation may be strong enough for successful therapy of aortic dissection regarding the dissecting force caused by blood flow. By analyzing the reflecting and transmitting light of the diode laser from the welding section, we could monitor the progress of the welding process in the deep portion of the dissection model. A welding section temperature of approximately 300°C, which corresponds to the melting point of elastin, was estimated by thermal conduction calculation using the finite element method. From the fluorescence image of the aortic pieces, elastic fiber was observed at the dissection model surface. The mechanism of this laser vascular-welding may be based on elastic fiber entwining. We believe there is potential for this method to be applied to catheter-based therapy for aortic dissection.

抄録全体を表示

A number of papers have been reported describing the mechanism of Korotkoff Sound generation. The phenomenon of self-excited oscillation in a collapsible tube is one of the influential theories among them. This oscillation is closely related to the compliance and cross sectional area of the tube and the flow in the tube. In this study, using a circulatory simulator, we have compared the oscillation with Korotkoff Sound generation. Three latex tubes with different compliances were used to find the relationship between Korotkoff Sounds and arterial compliance. The compliance of each of these tubes is different in value, but nearly similar to the carotid arteries of the cow. As a result, each latex tube indicated different changes in power spectral density between 100-300Hz in every number of Korotkoff Sounds. Furthermore, the number of Korotkoff Sounds flowing in the tube generating self-excited oscillation agreed with the number of frequency components included between 100-300Hz. On the basis of these results, the classification of latex tubes of different compliances could be distinguished using changes in power spectral density of the Korotkoff Sounds. In the same manner, biological arterial compliance could also be measured. Therefore, we came to the conclusion from our results that Korotkoff Sounds are strongly influenced by compliance. In addition, the method might be applied for the non-invasive measurement of arterial compliance.

抄録全体を表示

We have developed a non-wearing type of pupillography with better temporal and spatial resolution than conven-tional devices. The subject lies on a comfortable bed, where his/her head is supported by a soft pillow, and looks into the pupillographic device. A video camera sensitive to infrared light is positioned about 70cm from the participant's eye and the video image is digitized at 125Hz with a resolution of 2μm diameter utilizing recent developments in high-speed electronic counters. To test the applicability of this new device, we investigated the association of pupillographic measurements with sleepiness under the condition of sleep deprivation. In nine physically and mentally healthy young subjects, physiological arameters were recorded every 2hr in an overnight sleep-deprived setting. As papillary measures, spontaneous pupillary movements were recorded continuously for a period of 4.096 seconds with the pupillography at 125Hz. Two parameters are calculated to describe the pupil behavior: average size of the pupil and pre-determined index reflecting the fluctuation of the pupil size. The effect of length of sleep deprivation on these two parameters was analyzed. While the length of sleep deprivation had no significant effect on the average pupil size, it had a significant effect on the index of pupil fluctuation: the level of fluctuation increased gradually during the course of overnight sleep deprivation. These results are in good accordance with previous reports in literature, although we analyzed the component of higher frequency regarding the pupil size fluctuation as compared to previous studies. This preliminary study provides evidence that this pupillography is reliably applicable to physiological studies with multiple measurements. It is expected that the non-invasive nature of this device will allow its use in a broad range of clinical studies as well.

抄録全体を表示

Our aim in this study is to obtain images of current distributions including morphological information on the heart. Such images are obtained by projecting two-dimensional (2-D) current-arrow maps, calculated from magnetocardiogram (MCG) signals, onto a three-dimensional (3-D) heart model obtained from magnetic resonance (MR) images. We used a superconducting quantum interference device (SQUID) system to measure the normal component (Bz) of MCG signals. The signals were measured at 64 points with an 8×8 array above the chest, and were acquired at a sampling rate of 1kHz. The MR images were obtained by scanning coronal planes with a 6mm vertical separation. We made individual heart models for three healthy subjects from heart-outline points extracted from the MR images of the subjects. Current-arrow maps were calculated by taking the orthogonal partial derivatives of the MCG signal normal component. The current-arrow maps for three healthy subjects were then projected on the individual heart models by means of displacement-free mapping of the current vectors to the corresponding heart-outline points. The currentarrow maps, which were projected to the individual heart model, strongly reflect the respective electrophysiological phases (P-wave, QRS-complex, and T-wave), and give us a clear view of the anatomical sites of activation in the heart.

抄録全体を表示

Optical imaging based on intrinsic signals is widely used in visualizing the functional organization of the cortex. However, the evoked optical changes are small compared to the background optical intensity. It is critical for the application of this technique to separate the stimulus-driven optical change from the background optical changes. The background optical changes or noises are generally independent of the stimulus presentation. Therefore, in this study we propose a signal extraction method based on the temporal relation between the stimulus presentation and optical changes recorded. We have applied this method to the primary visual cortex of cats. It was demonstrated that the noises caused by the movement of blood vessels or the cortical surface could be removed by the proposed method.

抄録全体を表示