Advanced Biomedical Engineering Vol. 6(2017)

We have developed a novel electronic musical instrument with a pre-programmed score, called “Cymis,” to help the disabled enjoy playing musical pieces. In 2008, field experiments commenced at a nursing home (capacity 52 clients; average age 58.6; cerebral palsy 32 clients). The purpose of the present study was to demonstrate that Cymis is useful and effective for helping the severely disabled maintain or improve their quality of life. First, the accessibility of Cymis was revealed by the fact that 34 clients (63%) played Cymis for an average of 5.6 years. Second, each client’s progress in performance, which possibly reflects improvements of upper-limb motor control function, was examined for the longest duration of over 7 years. Among 31 clients, 13 (42%) showed progress, 17 (55%) showed no change (5 of whom showed progress initially but then regressed to their original status), and 1 (3%) revealed deterioration in condition. Third, psychological effects were measured using an original Face Scale before and after playing Cymis, for a total of 395 performances by 38 clients. Clients became happier in 208 performances (53%), showed no changes in 139 (35%), and became sadder in 48 (12%). Finally, with respect to their care plans, 19 of 52 clients (37%) selected Cymis in 2015, and this number itself implies the importance of Cymis. Basic reasons for selection were investigated by care workers’ assessments from mental and psychological perspectives. In conclusion, Cymis was useful, effective, and attractive to the disabled; it permitted them to enjoy playing music that might not otherwise be possible, and some evidence of therapeutic effect was found.

We have developed retinal prosthetic devices based on suprachoroidal-transretinal stimulation (STS). The effectiveness and safety of such novel devices are confirmed by in vitro and in vivo tests based on scientific knowledge. Animal testing is especially important because it demonstrates the total safety of the device. We successfully developed a long-term evaluation system with automatic stimulation and measurement of electrochemical characteristics in freely moving rabbits. This system allows evaluation of long-term safety and change in electrochemical characteristics. In addition, we conducted a pilot evaluation of the safety of STS using bullet-shaped electrodes in rabbits. No obvious injuries were observed in all examinations. However, the array moved away from the retina in a few rabbits. Visual and electrical evoked potentials (EEPs) were recorded after three-month implantation. The function of the retinal neurons around the electrode is assumed to be maintained because EEPs were observed after three-month stimulation. However, the evoked potentials become indistinct with time in some rabbits. The development of implantable recording electrode capable of long-term evaluation is necessary for assessing the function of retina exposed to electrical stimulation. Long-term safety and change in electrochemical characteristics can be confirmed easily using this system. No histological difference was observed between the active and inactive electrodes, suggesting that the amount of charge used in the study can be safely injected. The charge injection capacity (CIC) of these electrodes provides an indication of the safety threshold for STS. The electrode array should have a curvature to fit the eyeball to avoid movement of the array away from the retina. The electrode height is slightly greater compared to the sclera thickness. Accordingly, methods to enhance the CIC vs. geometrical surface area are required if the electrode height is reduced. We were able to obtain an indication of the required performance for the stimulation electrode based on the safe charge injection for STS (CIC of approximately 90 μC/cm² in PBS) and establish a system capable of evaluating safety and durability of retinal prostheses for long-term stimulation.

Bipedal locomotion requires an automatic process for rhythmic motor generation, as well as volitional and precise motor control for purposeful action. The neural substrates for these two distinct locomotion controls in humans are still unclear. This functional magnetic resonance imaging (MRI) study investigated the neural activity of the locomotor-related brain regions along with participants' lower limb behavior. Participants lay face-up in the MRI bore and moved their legs up and down at the knees under two conditions. Under the non-obstacle condition, they moved their legs while watching a point-of-view video that showed walking straight along a corridor at a constant speed. On the other hand, under the obstacle condition, the point-of-view video showed walking while avoiding obstacles in the passage. Two white markers were pasted on the soles of the participants' feet and images were captured by a video camera throughout the experiment to track the participants' lower limb movements. The horizontal fluctuation of lower limb movement was extracted offline. We assumed that the horizontal fluctuation reflected participants' volitional behavior of lower limb movement. The results showed that the obstacle condition elicited greater fluctuation of lower limb movement compared to the non-obstacle condition, and elicited brain activation in wider areas including the parietal and occipital lobes compared to the non-obstacle condition. The involvement of the parietal and occipital lobes in volitional control is consistent with findings of previous animal studies. In a correlation analysis between the signal change extracted from the locomotor-related cortical/subcortical regions and the horizontal fluctuation of the feet, activities in the cortical motor areas (primary motor cortex, premotor cortex, and supplementary motor area) showed weak but significant correlation with the fluctuation of lower limb movement. Activities in the cerebellar and mesencephalic locomotor regions showed no significant correlation, but almost constant activation irrespective of fluctuation of the lower limbs. These results suggest that the parietal, occipital cortices, and cortical motor areas are involved in volitional control.

Surgery can become safer and more reliable if the conditions of the organs can be physically and quantitatively assessed through simultaneous intraoperative measurements and physical estimations of deformed organs. This study proposes a new method for estimating external forces based on local displacement of elastic bodies. Using this method, one can estimate the magnitude and position of forces not only on the forceps but also in the invisible field. Simulation studies confirmed the effectiveness of this method. The experimental results showed that partial observation of a deformed shape achieved successful estimation of the external forces.

In this study, we improved upon a high-input impedance monitoring device comprising capacitive sheet electrodes placed under a bed sheet, aiming to detect all ECG waves including T waves. To accomplish this, we widened the passbands for ECG and respiratory movement (RM) signals. However, because this widening may lower noise tolerance, we substituted conventional front-end buffers with buffers able to discharge DC potential. Further, the backside of the modified electrode was doubly shielded by using the electric potential of the buffer's output and ground. We also introduced a virtual midpoint circuit to realize stable ECG and independent RM measurements of the chest and abdomen with the goal to detect obstructive sleep apnea in future applications. We tested our device on seven healthy adults during a six-hour sleep experiment. In all subjects, we detected T waves and observed ECG and RM signals in supine and lateral positions. In experiments in which respiratory rate was changed at regular intervals, the RM signal was synchronized with the simultaneously measured reference signal. The sensitivity and accuracy of R waves averaged over all subjects were 93.2% and 92.9%, respectively. Both averaged sensitivity and accuracy for T waves were 94.5%, while averaged accuracy of chest and abdominal RM was 70.9% and 74.0%, respectively. The results for ECG signals indicate that our improved system is applicable to unconstrained monitoring of vital signs in adults. Although there is still room for improvement in RM measurements, the results suggest that our system may also be used to detect variations in breathing.

It has been shown that injection of a minute electrical noise to an afferent input enhances the steadiness of force output, while reducing the variability of motor unit discharge intervals. To elucidate the involvement of alpha motor neurons in this noise effect, the effect of electrical noise injection into the soleus muscle (SOL) on the excitability of the alpha motor neuron group was examined. Nine young human subjects lying supine on a bed received a minute, subthreshold electrical white-noise-like stimulation to the SOL. In each subject, a 20-min trial with noise (Noise) and another 20-min trial without noise as control (Con) were performed in random order. The H-waves and M-waves were successively elicited at 1 Hz during each trial. The results showed that the static properties (mean, standard deviation, and coefficient of variation) of H-wave and M-wave amplitude fluctuations were not different between Noise and Con conditions (p > 0.05). On the other hand, the scaling exponent α, a dynamic property of the fluctuation of H- and M-wave amplitude, decreased significantly under Noise condition in H-wave amplitude (p < 0.05), but was unchanged in M-wave amplitude (p > 0.05). These results indicate that application of electrical noise to the afferent input affects the dynamic properties of motor neuron excitability, thus supporting the notion that the motor neurons are involved in the effect of noise injection on the motor control system.

Two different experiments utilizing the motor imagery of finger movement were conducted. We attempted to reveal the difference in corticospinal excitability between tonic contraction (TC) and rhythmic movement (RM) by transcranial magnetic stimulation (TMS). The magnetic coil was placed over the subject’s primary motor cortex to elicit motor-evoked potentials (MEPs) by TMS. We have previously shown that the MEP amplitude is modulated by the frequency of active and passive finger movements. We hypothesized that visual feedback affects the corticospinal excitability. In the present study, the subject observed both TCs and RMs, and the MEP amplitudes elicited by TMS during both tasks were analyzed to assess changes in corticospinal excitability influenced by the motor imagery. A mirror box was used to show the subject the finger movement executed by a third person as if it were his own finger movement. For the TC task, the third person performed a pinching task consisting of TC of the index finger and thumb. The subject received visual feedback of the TC in the mirror. For the RM task, the subject observed the mirror while the third person performed RM of the index finger until TMS was applied. The frequencies of finger movement were 0.5, 1, 2, 3, and 4 Hz. The resulting MEP amplitudes for the RM task at movement frequencies of 2, 3, and 4 Hz were significantly lower than that for the TC task. These results indicate that corticospinal excitability is increased by visual feedback of TC but is modulated by that of RM.

Bronchoscopic diagnosis of peripheral lung cancer with ground-glass opacity (GGO) is difficult because GGO lesions cannot be visualized using currently available radial probe endobronchial ultrasound. Therefore, a forward-looking single fiber scanning optical coherence tomography (OCT) probe with a local observation function has been developed to achieve precise sampling. The new OCT probe is only 1 mm in diameter. The probe is composed of a patterned electroplated copper coil fabricated on a polyimide tube using non-planar photofabrication technique, and an optical fiber having a permanent magnetic tube with a diameter of 0.5 mm. When an electrical alternating current is supplied to the coil, the permanent magnet vibrates electromagnetically with the optical fiber. To increase the fiber vibration amplitude, a micro gradient-index (GRIN) lens is set in front of the tip of the optical fiber. Using the micro GRIN lens, the output beam is focused, and the scanning range is enlarged. The view angle becomes approximately 45°, and image resolution becomes approximately 60 μm. The structure of grating was successfully imaged using the new OCT probe. Further improvements and animal experiments are necessary to determine the clinical application of the probe.

Diffuse correlation spectroscopy (DCS) is an emerging optical technique for noninvasive measurement of hemodynamics of living tissues. Using emitter and detector optical probes attached to the body surface, DCS estimates the mean speed of blood flow in the tissue, through which the emitted near-infrared light propagates (blood flow index: BFI). The advantage of DCS is that the mean blood flow in deeper tissues such as muscle layers can be measured noninvasively. To investigate the sensitivity of DCS in detecting the physiological changes of blood flow in deep and shallow tissues, we measured the blood flow speed in 14 healthy participants during a reactive hyperemia test and skin temperature changes. In the reactive hyperemia test, blood flow returned to the steady state faster in deep tissues than in shallow tissues, and temperature-dependent reallocation of local blood flow in shallow and deep tissues was clearly observed. These results demonstrate that DCS can measure the differences in physiological blood flow dynamics in deep and shallow tissues, suggesting the potential use of DCS to noninvasively quantify changes at microcirculation level in both shallow and deep tissue layers.

Development of direct neural interface (DNI) including visual prostheses absolutely requires confirmation of their long-term safety and stability. Functional evaluation by electrically evoked potentials (EEPs) is effective in this regard, although the recording system must be stable for chronic use. In addition, control of anesthetic depth is important for stable recording of the evoked potentials. The purpose of this study was to develop a chronically implanted electrode capable of recording visual evoked responses safely during repeated anesthesia over long periods, which would allow more effective safety evaluations of not only visual prostheses but also DNI. We developed two types of electrodes, and implanted them into rabbits. A general screw electrode was used for comparison with the novel electrodes. Structurally, the newly developed platinum (Pt) ball-tip screw electrode consisted of a plastic screw with smoothly surfaced Pt balls on the tip. The depth of implantation into the brain was adjustable via a threaded insert installed in the skull. The newly developed platinum/iridium (Pt/Ir) ball-tip planar multi-electrode array (MEA) comprised Pt/Ir ball electrodes placed in a two-dimensional lattice pattern, which was implanted just beneath the skull. These electrodes recorded variations in visual evoked potentials (VEPs) in response to 20 J flash stimuli over a period of 48 weeks. After 48 weeks of implantation, the ability of the electrodes to continue recording EEPs was confirmed (500 µA, 500 µs, cathodic first biphasic). During the recording of VEPs and EEPs, stable anesthesia was maintained with isoflurane (end-tidal 2.4%). The depth of anesthesia using isoflurane could be adjusted safely, and allowed stable recording of evoked potentials throughout the long-term study. However, stable recording using the general screw electrode was possible only for a short period. We also obtained stable latency and N₁ amplitude readings over the 48 weeks using the newly developed electrodes, and successfully recorded EEPs after the 48-week period. These results suggest that the novel electrodes work well over the entire duration of the study, and may allow assessment of long-term safety and stability of not only visual prostheses, but also other devices utilizing brain machine interfaces or direct neural interfaces.

In this study, we used a small implantable complementary metal–oxide–semiconductor (CMOS) imaging device developed by our research group to estimate the blood flow changes by focusing on the movement of red blood cells in the captured movements. Conventional methods for determining blood flow velocity have limitations in that variation occurs due to manual measurement. Therefore, we developed a novel technique to measure blood flow in the brain. This method involves calculating the changes of selected pixels using a normalized cross-correlation coefficient. Using this cross-correlation method, we analyzed a mouse cerebral infarction model to detect changes in brain activity. The results of analysis showed that the average velocity of blood flow upstream of the infarction site decreased while the velocity in blood vessel parallel to the infarction increased after occlusion was induced. These results thus confirmed that the new method can detect blood velocity changes, suggesting the feasibility of the cross-correlation method for estimating blood flow velocity.

In recent years, a rapid increase in bacterial strains resistant to modern antibiotics has been observed. This alarming rise in drug-resistant organisms has emphasized the importance of identifying new effective antimicrobial agents. Since traditional approaches for drug susceptibility testing are time-consuming and labor-intensive, more efficient methods are urgently needed. Here, we report an automatic image analysis system for drug susceptibility testing that provides results within 3 hours using a drug susceptibility testing microfluidic (DSTM) device. The device consists of five sets of four microfluidic channels prepared by soft lithography. The channels are in close proximity to allow simultaneous observations. The antimicrobial agent and bacterial suspension to be tested are added to the channel and incubated for 3 hours. Previously, microscopic images of the DSTM device were analyzed manually by an expert to evaluate the susceptibility of a strain. In this work, we present an automatic computer vision algorithm for processing images and performing analysis. The algorithm enhances the quality of the input image, detects cells in each channel, extracts a variety of cell-related characteristics, and estimates drug susceptibility using a pre-trained support vector machine. We address the issue of overlapping cells by incorporating a graph-based cell separation algorithm. The minimum concentration of a drug for which the proposed method predicted susceptibility represents the minimum inhibitory concentration (MIC). The novel method was implemented as a standalone application and tested on a dataset containing images of 101 clinically isolated strains of Pseudomonas aeruginosa incubated in the presence of five different drugs. The estimated MICs correlated well with the results obtained using the conventional broth microdilution method.