The fat suppression radio frequency pulse currently employed for MRI, which selectively saturates the frequency of the fat, has the narrow-band frequency characteristics. Therefore, the application duration for the pulse employed tends to be prolonged. In the present study, we designed a new fat suppression RF pulse using the Laguerre function in order to shorten the duration for fat suppression RF pulse and conducted an evaluation with the clinical equipment. The length of the RF pulse that we created allowed to reduce the duration by 47.3% compared with that employed for the clinical equipment. In addition, in the MR imaging evaluation, the new pulse was confirmed to have the fat suppression effect equivalent to that employed for the clinical equipment.
Sibilant /s/, one of unvoiced sounds, is believed to be produced by a jet of air through a sibilant groove towards the sharp edge of the teeth. In the present study, we investigated effects of an expiratory flow rate on the acoustic characteristics of sibilant /s/. A large eddy simulation was implemented to investigate flow in an intra-oral cavity model which simplifies important anatomical features of an oral cavity when sibiliant /s/ is pronounced. The results illustrated that an increase in the expiratory flow rate caused to develop turbulent vortices in a separated flow from the edge of the obstacle wall which mimics a lower tooth. The increase in turbulent intensity induced a dramatic elevation in the Powell's sound in the flow separation region, which was regarded as a sound source of sibilant /s/. A frequency spectrum analysis of the flow velocity in the flow separation region showed broadband signals up to 20,000 Hz as consistent with characteristics of sibilant /s/. The maximum of the Powell's sound, which was located near the anterior edge of the obstacle wall at smaller flow rates, shifted downstream in the flow separation as the expiratory flow rate increased and whereby turbulence developed. These results demonstrated significant influences of the expiratory flow rate on the acoustic characteristics of sibilant /s/ in particular when the flow rate elevates to cause turbulence.
Phase-contrast imaging based on a novel X-ray source, parametric X-ray radiation (PXR), has been studied at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. The PXR was generated by the 100 MeV electron beam incident on a Si single crystal. The quasi-monochromatic X-rays in the 5 to 34 keV range were used for the imaging experiments. The phase-contrast imaging method is appropriate for imaging of the soft tissues in biological materials, since it is effective for improving the low-contrast property in the standard absorption-contrast imaging of materials which have low X-ray absorption coefficients. Diffraction enhanced imaging (DEI) method was employed as the phase contrast imaging technique. Computed tomograms for a biological organ were obtained from the DEI data taken in 90 different orientations. Particular properties of PXR, i.e. compact facility, large X-ray beam irradiation field of approximately 100 mm in diameter and quasi-monochromaticity, suggest the potential of the PXR-DEI as a tool for medical diagnoses. The phase-contrast imaging by PXR was achieved in the first time.
This research is aimed to apply a contraction motion of a cultured muscle to the engineering field. The muscle cell can be contracted by the electrical stimulation. To stimulate the muscle cell, voltage was applied to the culture medium with cells. The membrane potential change by the electrical stimulation was measured using the microelectrode and analyzed employing equivalent model of the cell. Then, current was applied to the intraceller using the microelectrode. The membrane potential change by the electrical stimulation was measured using the microelectrode and the quantity of contraction was measured by a digital image analysis. These results considered an association between the membrane potential change and the quantity of contraction.
The implantable cardioverter-defibrillator (ICD) is an effective therapeutic device for rescuing patients with cardiac diseases from death caused by life-threatening arrhythmias. For development of the ICD, it is important to accurately distinguish among normal sinus rhythm, ventricular tachycardia (VT), ventricular fibrillation, and supraventricular tachycardia (SVT) . Thus, in this study, we have proposed a multiple regression model based on 14 indices extracted from two-dimensional statistics of intracardiac electrocardiograms to detect four kinds of cardiac rhythms as accurately and quickly as possible. The experimental results showed that the proposed method had a sensitivity of 0.97 for detecting SVT and a specificity of 0.99 for detecting VT, which were improved respectively from 0.83 and 0.85 obtained from the previous method, and that early detection within about 1.6 seconds was attained.
We have developed a method of preventing bathing accidents based on the respiratory rate, body motion, and water level. The respiratory waveform could be detected from the RR interval (RRI) of the bathtub electrocardiogram (ECG) . The body motion and water level were detected from the alternating current (AC) and direct current (DC) components of the acceleration signals. The device consisted of an ECG amplifier, accelerometer, Bluetooth module, and personal computer (PC) . The changes in the DC component in terms of the level change when the subject entered the bathtub were used as a trigger to switch the system on. A bathing accident was simulated that involved body motion, submergence, and apnea while taking a bath. The algorithm for detecting accidents was based on the absence of respiration and body motion and a high water level. As a result, the accident could be detected during the period of apnea. The time from accident onset to detection was 18.7 ± 7.3 seconds. It was possible to distinguish relaxation, body motion, submergence, and apnea using the bathtub ECG and an accelerometer. Thus, bathing accidents could be detected at an early stage.
Recent studies by the authors of this paper have consistently shown that the landing position of the swing foot (healthy foot) of the subjects being experienced with the three point axillary crutch can be estimated by the body acceleration. The experimental analysis also shows that the experienced subjects have the capability to land their healthy foot on the estimated positions. However, inexperienced subjects suffer from it. Basically the landing position differences of inexperienced subjects and the estimated ones results in sudden unstable acceleration of the body. The purpose of this paper is to develop a new crutch walk training apparatus that enhances inexperienced subjects' walking stability by instructing optimal landing positions. For instruction, a laser pointer was employed with the axillary crutch walk training apparatus that was developed by the authors. Some walks of subjects with the training apparatus were measured. As a result, it was confirmed that frequency of sudden changes of their bodies' acceleration decreased steadily during walk when using the proposed landing point instruction device.
A microwave Doppler sensor can sense wide range of human motion, from minute displacement of body surface caused by respiration to large movement like walking, without contact. To apply the sensor to monitoring human daily activity for safety and health, it is necessary to estimate the current state from the raw signal of the sensor output. In this paper, we propose a method to detect the following three state, “move”:the target is changing his/her position or pose, “resp.”:the target sits still and is breathing, and“hold”:the target sits still and holds his/her breath. The observed sensor signal is classified by three binary classifiers prepared for each state. For input of the classifiers, three kinds of features, energy, frequency-domain entropy, and histogram are extracted from the raw signal. The result of the experiment showed that the proposed detector surpassed that of previous related works especially in respiration detection. We tested three classification methods, least squares, SVM and AdaBoost. There was no significant difference between the performances of classification methods. Cross validation was done by two different ways of data division. In one way of the data division, both training and test data contain data of all the subjects who participated in the experiment. In the other way, training data do not contain the data which belong to the subject of the test data. As the result of this test, the classifiers trained by other persons'data were not inferior to those trained by data which contain the target's own data. This means that the state detection does not depend on the individual target. The parameters can be configured at the factory.
Actin fibers (AFs) play a key role in the mechanical strength of cells. They are pre-strained and generate a tensile force (initial tension) even when a cell is not subject to any external force. We simulated tensile and compressive tests of a cell with various initial AF tensions using a cell computational model to understand how initial tension affects the cell's mechanical properties. AF tension was mathematically described as a function of its elongation, and the initial AF tension was controlled by changing the natural length of the AFs. Our results showed that an increasingly large load was required to stretch and compress a cell for the same strain as the initial AF tension increased. Also, as the tension increased, the Young's modulus of the cell, calculated from load-strain curves, tended to be greater in both tensile and compressive tests. In tensile tests, AFs were reoriented passively in the stretched direction as the cell elongated, and a greater load was required to stretch the cell for higher values of initial AF tension because AFs contracted to pull the cell membrane inward. In compression tests, AFs became passively reoriented perpendicular to the compressed direction. These perpendicular AFs in the cell resisted cell elongation in a direction perpendicular to the cell compression, and the initial AF tension contributed to an increase in the resistance against the cell elongation. Thus, passive orientations of AFs increased the Young's modulus according to the initial AF tension. These results demonstrate that initial AF tension had a strong effect on the global tensile and compressive properties of cells.
RFID (Radio Frequency IDentification) is new individual identification media which takes the place of bar-code. If RFID tag is applied to medical environment, human error in the environment are prevented, since RFID uses wireless communication in its identification. However, its communication is affected by another wireless communications as electrical noise. In this paper, effects of mis-identification by Home use PLC (Power Line Communication), electrical-lamp shaped fluorescent lamp and electrical-lamp shaped LED lamp are estimated. An effect for aging of inverter circuit in electrical-lamp shaped fluorescent lamp is also estimated. In this experiment, capacitance in the inverter circuit is changed as a virtual aging.
We developed a computer-based neuropsychological test (CBT) using a personal computer with a touch panel that was easily operated by elderly individuals to evaluate the cognitive functioning of members of this population. Although elderly patients have been participating in exercise as part of their occupational therapy (OT) for cognitive impairment, discussions about the effectiveness of this modality are rare. This study evaluated this treatment approach in terms of changes in the patients'cognitive functioning. We administered the CBT and Mini-Mental State Examination (MMSE) before and after therapy. The results revealed that cut-off scores on the MMSE and CBT were highly correlated, but the therapeutic effect of the OT intervention could not be judged.