The plantar aponeurosis extends from the calcaneus in the shape of a fan toward the five heads of the metatarsals, and plays an important role in the stability and shock absorbing capacity of the foot. We speculated that the “viscoelastic socks” absorb instantaneous impact owing to their viscoelasticity and thus reduce the load on the plantar aponeurosis. The purpose of this study was to verify this load reduction through quantitative measurement of the dynamic changes of the medial longitudinal arch structure of the foot during gait. Eleven healthy male adults (age, 22.1±1.1 years) participated in the study. Experiments were conducted under conditions of wearing and not wearing the viscoelastic socks to clarify the structural changes in the longitudinal arch during gait using a strain gauge attached to the first tarsometatarsal joint of the right foot. The results of 9 subjects demonstrated a tendency that wearing the viscoelastic socks reduced the changes in the medial longitudinal arch during the timing from heel contact to toe contact and from heel off to toe off. These findings suggest that compared with the conventional socks, the viscoelastic socks may reduce the changes of the arch during gait and mitigate the mechanical burden on the plantar aponeurosis.
Monitoring urea in spent dialysate by ultraviolet (UV) spectroscopy is a useful noninvasive method for reagent-free, real-time assessment of the kinetics of uremic substances during hemodialysis. This study investigated the UV absorption properties of creatinine (Cr) and uric acid (UA), which are uremic nitrogen compounds like urea, and the application of UV detection of these compounds to the monitoring of spent dialysate. We found that the UV absorbance of urea from 230nm to 300nm was less than 0.001. On the other hand, the absorbance spectrum of Cr had a large peak at wavelength 236nm, while the spectrum of UA showed two peaks at 236nm and 290nm. There was a significant correlation between the actual concentration in spent dialysate and that predicted from the peak value at 236nm for Cr (r=0.96, n=27) and UA (r=0.88, n=27). In addition, there was a significant correlation between the actual concentration of UA in spent dialysate and that predicted from the peak value at 290nm (r=0.99, n=27), and the correlation was stronger at 290nm than at 236nm. Furthermore, at wavelength 290nm, there was a significant correlation between actual and predicted concentrations for both Cr (r=0.89) and urea (r=0.91, n=27), suggesting that low molecular weight uremic substances in spent dialysate can be monitored at this wavelength. These findings indicate that monitoring Cr at 236nm and UA at 290nm in spent dialysate is more suitable than monitoring urea.
We are developing a therapeutic system that uses acoustic radiation force to control a micro object in blood vessel aiming to reach target sites such as tumors. To realize this system, we have proposed a method to analyze the 3D structure of blood vessel network by fusing the Doppler-mode and B-mode ultrasound volumes, including the blood vessel network near the target area. However, there was limitation to perform verification experiments with blood vessels in vivo, because of the difficulties of inserting a micro object into an actual blood vessel. Therefore, for 3D reconstruction of blood vessel, we considered to fabricate a phantom with the actual shape of blood vessels which can be imaged by both B-mode and Doppler-mode ultrasound. First, we prepared six types of materials including silicon and rubber to mimic vessel wall, which can be fabricated by a 3D printer. Next, we prepared two types of materials;agar and PEGMA, to mimic surrounding tissues, and blended graphite powder to reproduce speckles on echograms. After verification with echograms, the optimal combination selected was UV-curable resin (can be molded by a 3D printer) as vessel wall and agar as surrounding tissue. The fabricated phantom with water flow to mimic blood flow was examined for visualization of the branched structure by both B-mode and Doppler-mode. As a result of 3D reconstruction of the ultrasound volumes, the branched structure of the blood vessel was clearly visualized.
In this study, we developed a new approach for simultaneous noncontact measurements of electrocardiograms (ECGs) and pulse beats (PBs) using passive and semi-active capacitive-coupling methods. The applicability of this method to blood-pressure (BP) monitoring of subjects in bed was then evaluated. For ECG measurements, two sets of five-layered conductive-cloth electrodes were placed under the subject's upper back and waist. A so-called driven-seat ground (DSG) was adopted for ECG measurements to reduce interference with the PB detection circuit. The DSG signal was fed back to the fifth layer of the electrode. For PB detection, one conductive cloth sheet was placed under the right calf and another under the right heel. The sheets formed capacitive couplings with the body via clothing, and the couplings were incorporated into a multi-vibrator. Changes in the oscillatory frequency of the multi-vibrator caused by PBs were measured as voltage changes. To increase the sensitivity of PB detection under the heel, the sheet area ratio between the calf and the heel was set to 5:1. Seven participants were instructed to lie on a bed in the supine position, and experimental measurements were performed on them. In the experiment, the following procedures were conducted : the subject rested for 20 s;a Valsalva test (VT) was conducted for 15 s;and the subject rested again for 100 s. As reference signals, continuous measurements of BP from the left fingertip, as well as chest ECG and photo-plethysmographic signals from the right fingertip were recorded. For evaluation analysis, all PBs were detected over the 80-second period of the output signals beginning 10 seconds after the end of the VT. As a result, the sensitivity of the PB was 99.2±1.1%. The mean correlation coefficient between the PB arrival time and systolic BP was-0.83±0.15. These results suggest the possibility of using the proposed method for noncontact BP monitoring during rest in bed.