The estimation of oxy-and deoxy-hemoglobin (HbO2 and Hb) concentration change in cerebral blood flow by near infrared spectroscopy (NIRS) has been being used for the assessment of cerebral function in recent years. However, some oscillating artifacts in the estimation seen even when subjects are in the resting state have made practical application difficult. This paper focuses on a method to eliminate the artifacts and level the baseline in the estimation. At first, we examined the appropriateness of the two-component model generally used in NIRS estimation, in which it is believed that HbO2 and Hb alone cause the changes in absorbance. Several estimations based on observations at different wavelength couples were carried out. If the two-component model is appropriate, these estimations should be identical. However, they significantly differed from each other. In order to avoid this problem, we introduced a wavelength-independent component into the model. This component represents factors such as light scattering, transmittance change in optics, and absorbance change caused by other matter, which are not considered in the two-component model. The wavelength-independent artifact was eliminated by using the differences in absorbance at the point of wavelength coupling. The Wiener filter was used to stabilize the estimation. Compared with the two-component model, the proposed three-component model was able to level the baseline in the estimation of concentration change well. The power spectra of the concentration changes estimated by the two models were also compared. A peak at about 1.2 Hz correlating with the heartbeat was observed in the case of the two-component model ; however, it disappeared when the three-component model was used. This method is useful to eliminate artifacts in the estimation of concentration change in HbO2 and Hb since it does not require any modification when used with multi-wavelength-type NIRS hardware.
The joint angles of the lower limbs are important parameters in evaluating the ability and stability of walking when training to walk or control FES gait. In this study, a simplified measurement method for lower limb joint angles that uses gyroscopes attached to the thigh, the shank and the foot is proposed. The method was examined by measuring the leg joint angles of three neurologically intact subjects when walking. The results showed a high correlation between the joint angles measured with the commercially available electric goniometer and those by the proposed method. Appropriate attachment positions of the sensors were also suggested from the experimental results. The proposed simplified measurement method for lower limb joint angles is expected to be effective for walking training or FES gait restoration at clinical sites.
This paper studies improvement of the clinical practicality of the control command input method for motor disabled patients using the recognition of specific motions via an artificial neural network (ANN). Several good ANNs that had different combinations of input signals and/or different number of neurons in the hidden layer were selected for each subject. The final recognition was determined by the majority decision rule by three good ANNs. The AND operation of the outputs of selected ANNs was also used to reduce the number of misrecognitions. The results with neurologically intact subjects and a hemiplegic patient showed that the proposed method would be effective clinically compared to the method using a single ANN with a fixed combination of input signals for all patients. It was also shown that trained ANNs with the proposed method could be used on other days with good performance.
An intravascular forward-looking ultrasound probe that is 3 mm in diameter has been developed. We used the probe as acoustic sources and receivers to make an ultrasound forward-looking image, but many artifacts were observed because of the strong directivity of the probe. For decreasing the directivity of the probe, a convex-shaped 1-3 composite PZT transducer, which is 0.7 mm in diameter and has a curvature radius of 0.75 mm, was fabricated and a low directivity feature was confirmed. A probe which has eight separated 1-3 composite convex-shaped transducers was fabricated. The probe is 3 mm in diameter and has a working channel that is 0.5 mm in diameter. Images of a single 0.6 mm width steel square rod and a pair of 0.4 mm width steel square rods separated by 0.8 mm were constructed using the fabricated probe.
This paper proposes a simulation system for intraoral radiography. The simulator we have developed enables dental students or interns to practice intraoral radiography without X-ray radiation and film costs. A system user can quickly obtain an intraoral radiograph after setting an indicator cone and film with respect to the simple dental mannequin mounted on the system. In this paper, we develop a dental-shape database from multi-slice CT images of human teeth, and formulate an algorithm to output the image of the intraoral radiograph on a computer display, where the dental-shape data, three-dimensional positional data of the indicator cone and film are input. Realistic observations of actual intraoral radiography are simulated.
A three-dimensional (3D) image overlay navigation system has been developed for open MRI-guided glioma surgery. The images are created by employing animated auto-stereoscopic images of integral videography (IV), which provides geometrically accurate 3D images and reproduces motion parallax without using any supplementary glasses or tracking devices. The spatially projected 3D images are superimposed onto the patient and are viewed via a half-slivered mirror. We developed a fast and semiautomatic tumor segmentation method and a spatial image registration method for intra-operative IV image-guided diagnosis and therapy. Two sets of preliminary experiments showed that the total system error was 0.90±0.21 mm in patient-to-image registration, and the procedure time of guiding a needle toward a target was shortened to 24%. The augmented reality of the image overlay system promises to increase the surgical instrument placement accuracy and reduce the procedure time as the result of intuitive 3D viewing.
This paper presents a method of material properties estimation for highly accurate finite element analysis of living soft tissue. It employs a compression test inside MRI in order to visualize the deformation of hypodermic structures, and an FE model of the compressed tissue in which the same boundary conditions as the compression test are assigned. The FE analysis is iterated with updated material constants until the difference between the two images, the observed MR image deformity and a synthesized deformed image, is minimized. The synthesized deformed image is obtained by warping the pre-compression MR image according to the displacement fields computed by the FE analysis. This method can, therefore, take subcutaneous structures and non-linear material characteristics of soft tissue into consideration. The estimated material constants guarantee high reproducibility of the FE analysis that can be evaluated in detail by comparing the two deformed images. This method is believed to be capable of conducting highly accurate FE analysis and its quantitative evaluation. The presented method was applied to a 3-layer silicon rubber sample. The results revealed that the performance of our method was excellent. The error in estimation was less than 7% for all layers, and the error in reproducibility of the FE analysis with the estimated material constants was confirmed to be 8%.
The self-reference method is a magnetic resonance (MR) thermometry method for mapping temperature changes in a target organ using the baseline phase field in a region of interest (ROI) estimated by the polynomial extrapolation of the field in the surrounding region (s) for estimating (RFE) and subtracting the baseline from the measured field. In the present work, optimization of the ROI and RFE to adopt this technique to MR-guided focused ultrasound surgery (MRgFUS) of uterine fibroid was examined. Both numerical simulation with the Gaussian-profiled heating region and application to clinical data showed that the optimal radius of the ROI should be larger than or equal to 2.7-times of σ, the radius of the temperature field with 1/e of the highest temperature at the heat center, whereas the optimal ratio of the areas of the ROI and RFE should be larger than or equal to 1.5. Use of multiple, isolated RFEs in place of a single, doughnut-like RFE surrounding the ROI was proposed to reduce temperature error due to the unfavorable phase inhomogeneity included in the RFE. The error induced in the isolated RFE was equivalent to that induced in the single RFE in the simulation when the ROI size and ROI to RFE ratio were identical. In the clinical data, the isolated RFEs yielded better agreement with the conventional, baseline subtraction method in Bland-Altman plots.
In this paper, we propose a method for estimating both the territory and location of single motor units (MUs) of the first dorsal interosseous muscle (FDI) by comparing the observed surface motor unit action potential (SMUAP) with model analysis. An eight-channel surface electromyogram (EMG) recorded the isometric contraction of 10% maximal voluntary contraction (MVC) by means of bipolar electrodes, each 1 mm in diameter, placed on the skin surface. To characterize and visualize features reflecting the territory and location of MUs, we investigated an SMUAP profile in which the peak amplitude of the SMUAP of an eight-channel EMG was plotted against each channel. While some SMUAP profiles were bell-shaped, most of them were flat-topped. A novel square-shaped territory model, not the circular-shaped territory model, was proposed to explain these profiles. Both territories and locations of single motor units were estimated for two subjects. A new finding was that most of the square-shaped territories expanded 10-15 mm horizontally along the skin surface. The present study showed the usefulness of the proposed method, particularly the introduction of the square-shaped territory model and SMUAP profile.
IKr specific blockers commonly exhibit reverse frequency-dependent prolongation of the action potential duration (APD). APD prolongation induced by IKr specific blockers varies according to the species of animal. The APD of animals with few KCNE1 genes (e.g., humans, rabbits and cats) is only slightly prolonged by IKr specific blockers. On the other hand, the APD of animals with more KCNE1 genes (e.g., guinea pigs) is markedly prolonged by IKr specific blockers, and the APD prolongation exhibits strong reverse frequency-dependency. However, the mechanism of the difference in APD prolongation is not clearly understood. In this study, we analyzed the relation of APD prolongation induced by an IKr specific blocker and the KCNE1 expression level with simulations using cardiac membrane action potential models that differ in the KCNE1 expression level based on electrophysiological experiments. In the experiments, KCNE1 of 0.2 ng, 1 ng and 5 ng was coinjected with KCNQ1 of 5 ng in Xenopus Oocytes. Expressed currents were recorded 1-2 days after injection by the double-microelectrode voltage clamp method at 35°C. Maximum IKs conductance and relations between time constants, maximum activation parameter and membrane action potential were obtained from fitting functions describing IKs channel properties in the Luo-Rudy model to experimental results with the Nelder-Mead simplex method. In simulations, we stimulated three models differing in KCNE1 expression level at six frequencies. From the simulation results, it was confirmed that an increase in KCNE1 expression level strengthened APD prolongation and the reverse frequency-dependency induced by the IKr specific blocker. In time histories of IKs, IKs increased as the result of high-frequency stimulation in the case of more KCNE1 genes. An increase in IKs induced by time constant prolongation with an increase in the KCNE1 expression level led to a relative decrease in IKr contribution ratio to outward ion currents. This is the mechanism of the difference in APD prolongation and reverse frequency-dependency induced by an IKr specific blocker according to animal species.
Muscular fatigue gradually progresses during long-time repetitive exercise in sports or rehabilitation, and in turn, it causes a higher risk of injury. Especially, the risk is higher than expected for skiing exercise because skiing exercise is alternately repeated all day long including ski-lift riding. Additionally, skiers must disembark from the ski lift after riding it to the top of the slope. In this study, we measured surface EMG at the tibialis anterior (TA) and the vastus lateralis (VL) muscles with respect to knee joint angles using a portable data acquisition system. For estimating muscular fatigue, we calculated the mean power frequency (MPF) of the surface EMG for selected intervals as determined by knee joint angles. The results showed that MPF at VL declined in the first half of the trial, and then plateaued in the latter half of the trial. The trend in decreasing MPF was steep in the afternoon compared to that in the morning. Therefore, the muscle activities during skiing can be evaluated by the MPF of EMG for selected intervals using knee joint angles.
We previously investigated the effect of movement-associated intention on nervous activities using neurophysiologic indexes in order to estimate how movement is generated under expected or unexpected conditions. In this study, we measured magnetoencephalographic (MEG) signals during passive finger movement, and evaluated the effect of the existence of anticipation on cortical activities. The subjects were 10 right-handed healthy volunteers. The subjects anticipated the passive movement by receiving warning signals before the movement, and the passive movement was generated as the result of the subjects' anticipation. In the first experiment (Experiment I), a series of warning signals was presented to indicate the onset of passive movement. In the second experiment (Experiment II), a warning signal was given to indicate the direction of passive movement. The passive movement was lifting or lowering the right middle finger (only lifting was applied in Experiment I). Consequently, in Experiment I, for passive movement with a warning signal, MEG deflection before the movement and shortening of the peak latency with a reduction in the amplitude of somatosensory evoked field (SEF) components were observed, compared to values under the condition of no warning signal. However, in Experiment II, there was no change in peak latency, but reduction in the SEF amplitude under the conditions of a warning signal being given. The present results indicate a possibility that anticipation prior to the predictable passive movement modulated the cortical activities in physiological condition.
Reading comprehension requires the processing of both semantic components and grammatical aspects, which includes the analysis of words and their order (syntax) to understand the sentence structure. Here, we report an MEG (magnetoencephalography) study performed to measure the time course of neural responses and to image their activities while subjects were reading Japanese complex sentences. The stimulus sentences consisted of subject, object, and verb phrases, constituting the main clause and subordinate clause, and were presented visually phrase-by-phrase while conducting the MEG. We examined normal word-order (CAN ; canonical) sentences and scrambled (SCR) sentences that included “displacement” of the object phrase to the top of its subordinate clause. The localization of distributed sources was performed for the response to the object (or subject in the SCR sentence) phrase and verb phrase in the subordinate clause. Main activities in the left hemisphere were commonly found for the two phrases in the occipitotemporal border (fusiform gyrus) and occipital (visual cortex) regions within 190-300 ms from the onset of the phrases. After 300 ms, activities became strong in the prefrontal region. These activities in the posterior and anterior brain regions may reflect visual form analysis of words and working memory process, respectively. For the displaced subject phrase of the SCR sentence, early activity at about 140 ms was found in the left occipital-to-occipitotemporal region, suggesting facilitation of visual form analysis. Specific activity was also found strongly in the region around the left motor/premotor cortex in a wide latency range of 200-550 ms for both subject and verb phrases of SCR sentence. This finding suggests the possibility of motor/premotor activity, such as a mirror neuron circuit, in processing the displaced phrase without overt speech. Thus, the present study indicates the involvement of multiple regions other than classical language areas when processing syntactic aspects of scrambled sentences.
This study is the first step towards the proper application of microcirculatory blood flow in the human cardiovascular system. Blood plays an indispensable role in mass and gas transfer in the capillaries ; thus, it is important to make clear the behavior of human blood in capillary vessels of 5-8 μm in diameter. In order to clarify the blood flow behavior in capillaries, a new micro capillary vascular network model allowing the clear observation of flows using a high-powered microscope was developed inside a silica glass using a femto-second laser micro/nano fabrication system. Using this system it was possible to fabricate three-dimensional micro-tubes and micro-cavities inside a transparent material. The present capillary models have a diameter of about 5-20 μm. We succeeded in observing blood flow in this capillary model using a micro-flow visualization technique. Red blood cells and tracer particles sometimes flowed smoothly in the model, but sometimes adhered to the channel wall and formed capillary blockage. This phenomenon occurred independently of particle type and particle diameter. The surface roughness on the channel wall seemed to be involved in these particle-adhering phenomena.
The authors of this letter propose a novel “multi-layer hybrid scaffold” consisting of artificial blood capillary networks and cell-containing hydrogel for tissue engineering. The artificial blood capillary network was fabricated using a Membrane Micro Embossing (MeME) process, a unique, newly developed microfabrication process capable of fabricating freestanding thin polymer membrane micro-channels with both simplicity and high precision. With this process, a thin thermoplastic polymer membrane was placed on a deformable support substrate and embossed to fit 3D structures on a master mold by backpressure from the support. A one step heat-sealing method was used to successfully fabricate a highly branched “membrane micro-channel network” of biodegradable poly-lacticacid (PLA) micro-channels measuring 50 μm in width, 50 μm in depth, and 5 μm in wall thickness. The biocompatibility of the fabricated micro-channel was confirmed by culturing human umbilical vascular endothelial cells (HUVEC) on the micro-channel. This technology will provide a useful method for regenerating large organs in the future.
Ventricular aneurysm is one of the complications that follow a myocardial infarction. Left ventricular (LV) plastic and reconstructive surgery, Dor procedure, is widely performed in order to improve patients' cardiac functions. However, it is anticipated that the abscission region of the ventricle might cause some complications, such as mitral valve regurgitation. Therefore, the decision of what to be done with that area might affect therapeutic consequences. In this study, the authors have developed a measurement system for surface movement and a display system to demonstrate decreased LV systolic function during surgery. This system is capable of evaluating the cardiac function using displacement data obtained from superficial motion of the specific regions. Prior to measurement, the reflective ball markers were sutured on the surface of the heart without any complications or infarctions. The point of the markers indicated the anatomically specific points, such as apex, septum, mitral valve, and papillary muscles. The location of points was sequentially measured by an optical three-dimensional location sensor. The superficial area of the left ventricle from the left thoracotomy view was divided into 12 triangular regions each composed of three markers. As the contraction of the regional area corresponds to the cardiac systolic function, the changes in each area were examined. The contraction rate of the heart was superimposed onto the video images of a natural heart, which were obtained simultaneously. An animal study was performed to compare heart functions under a normal pulsating state and during the time of a myocardial infarction. The physical data such as electrocardiogram, blood flow and pressure were simultaneously obtained and compared using this approach. With the physical data, it was confirmed that strain change in the regional area was coincident with a contraction of the actual heart. It was also found that this method is simple enough to set up in the operation theater. In the near future, this method will contribute widely to the clinical diagnoses of patients, when advanced surgery such as robot surgery and/or organ transplant become popular.
A method to estimate the speed and direction of wave propagation of cardiac excitation in optical mapping and the utility are presented in this paper. Optical mapping has been widely used in arrhythmia studies where an isolated animal heart is stained with a membrane voltage-sensitive dye. We developed an optical mapping system consisting of a high-speed CMOS camera with high spatial resolution and advanced our understanding of the basic mechanisms of arrhythmia. Conduction velocity, the local velocity of the propagation of cardiac excitation, depends on cardiac tissue properties, fiber orientation, wave-front curvature, past activity, and drug effects. Conduction velocity is important to analyze the dynamics of cardiac electrical activity and must be estimated accurately by the accurate determination of depolarization times. However, it is difficult to obtain depolarization times correctly in optical mapping data because optical mapping has low temporal resolution. Taking advantage of the high spatial resolution in optical mapping, we extracted wavefronts from each frame of an optical mapping to obtain depolarization times and estimate conduction velocity by polynomial fitting to the times and positions of the wavefronts. Our method was applied to simulated data, epicardial activation during pacing and spiral wave reentry, which is known as one of the mechanisms to occur and maintain tachyarrhythmia, and estimated vector fields. For simulated data, the calculated velocity agreed well with the actual simulated velocity. In cardiac wave propagation during pacing, our method was able to estimate not only the mean conduction velocity, but also instantaneous conduction velocity. In spiral wave reentry, we quantitatively analyzed the delay of conduction velocity near the spiral wave reentry core and the relationship between conduction velocity and fiber orientation. Our method will be useful for the quantitative analysis of complex arrhythmia in optical mapping.
In this paper, we propose new control techniques to stabilize the drive voltage (output voltage) of a total artificial heart (TAH). To supply the electric power for driving a TAH, one of the methods is a transcutaneous energy transmission system (TETS) with air-core coils. It is possible to transfer energy by means of electromagnetic induction between two air-core coils placed face-to-face on each side of the skin. With such a design, however, the output voltage fluctuates due to the change in the value of mutual inductance between the two coils when the relative positions between two coils are changed. In order to stabilize the driving voltage of an artificial heart, it is necessary to control the output voltage using a feedback loop. Considering the problems of infectious disease and quality of life (QOL), it is desirable that the output voltage is controlled without a feedback cable. This paper reports on new control techniques that control the output voltage using a primary coil current that can be measured outside the body. As a result, we found that the efficiency of the transcutaneous transformer is more than 90% between the frequencies of 500-800 kHz, and the fluctuation of the output voltage, when the coils were shifted parallel to each other and the gap between the coils were varied, can be controlled to within 2.2 V (without control : 19.4 V).
In this paper, in order to improve energy transmission efficiency and minimize the size and complexity of the system, we propose a direct-drive system for an artificial heart using an ultrasonic motor for the artificial heart actuator. To supply energy for a total artificial heart (TAH), a transcutaneous energy transmission system (TETS) is one of the most attractive methods. It transmits energy through the skin without wires, using electromagnetic induction between two coils placed on either side of the skin. It is desirable for the energy transmission efficiency to be high and that internal circuitry is miniaturized. In a typical conventional method, the internal circuit consists of an actuator driver circuit, a rectifier and a smoothing circuit, due to the need to drive the artificial heart with DC power. Therefore, it is undesirable for the heat generation of the internal circuit to be excessively high and the physical volume of the internal circuit to be too large. With the proposed method, using an ultrasonic motor driven by AC power, the internal circuit can be eliminated and the AC power transmitted through the body input directly to the motor. First, we designed and tested an externally coupled transcutaneous transformer (ECTT) for an ultrasonic motor. Second, energy transmission efficiency and temperature increases in various parts of the TETS were measured, and the flow rate was estimated. As a result, a maximum energy transmission efficiency of 97% from the input of the transcutaneous transformer to the input of the artificial heart actuator was obtained. The volume of the internal circuit was also reduced by 75%. The temperature increase of the internal circuit was reduced by 90% compared to that of a conventional TETS. It was also confirmed that this proposed system has enough power to drive a TAH.
In conventional laparoscopic surgery, one medical doctor who only holds the laparoscope during the surgery is required. Therefore, in this study, we introduce an automatic tracking and zooming system for laparoscopic surgery by means of a steady laparoscope on the abdominal surface. The system can be added to a conventional laparoscopic system and can analyze camera images in real-time. The markers of this system are attached at the top of the forceps and extracted, and the focusing area can be estimated. In this study, we introduce two marker tracking algorithms ; one tracks a single marker on the forceps, which is assumed as the focal point ; and the other tracks two different colored markers, which can estimate a more practical focusing point. In order to perform high-quality real-time movie processing, the system uses a CPU and GPU (graphics processing unit) in parallel. The tracking algorithm is carried out by the CPU, image enlargement is carried out by the GPU, and then a high frame rate and low delay time are achieved. For the automatic smooth camera work, a new control model with many parameters is proposed. Through animal experimentation was performed six times, and appropriate values of parameters evaluated by two experienced doctors were obtained. After the evaluations of the experienced doctors, the effectiveness of the system was proven : cholecystectomy successfully conducted in animal experiments without the support of a scope-holding doctor.
Endoscopic surgery is minimally invasive and presents many advantages for the patient such as reduced pain, less scarring, and quicker recovery. However, endoscopic cameras offer a narrow field of view and display only visible surfaces, which limit the application range for surgery. Thus, augmented reality (AR) visualization superposition of pre-or intra-operative 3-dimensional (invisible) information about the interior of tissues such as a tumor in a 2-dimensional endoscopic view has become an important research challenge. The purpose of our study was to realize a real-time endoscopic image overlay system for intra-operative localization of a tumor in deformative organs. Thus, we have proposed a method for endoscopic image overlay called “direct calibration of endoscopic camera (DCEC)” and developed a prototype of the system based on 3-dimensional measurement using micro-fluxgate magnetic sensors in combination with the DCEC. In this paper, we propose a novel procedure to collect sample points for the DCEC using a permanent magnet as a sample point generator under the condition that another permanent magnet is embedded in the vicinity of the tumor. To evaluate the effectiveness of the proposed procedure, we estimated a threshold of magnetic force generated from one permanent magnet embedded near the tumor through computer simulation.
When conducting laser ablation of biological tissue, a tomography of the tissue surface is necessary to measure the crater shape and crater depth, and observe damage to the surrounding tissue. In this paper, we demonstrate the in situ observation of biological tissue surfaces during laser ablation using optical coherence tomography (OCT). For the laser ablation of tissue, a Q-switched Nd : YAG laser is used as the light source, which supplies laser pulses of 10 ns at a wavelength of 1.06 μm and a repetition rate of 10 Hz. The OCT imaging optics consist of a low coherence interferometer where a 0.85-μm SLD is used as the light source, providing the spatial resolution of 18 μm. In the experiment, the crater depth of a human tooth is measured using these OCT images, and then the ablation rate of 0.21 μm/pulse is determined. Moreover, time-serial tomographic observation of the crater during laser ablation is carried out, showing all of the OCT images continuously.
Laryngo-stroboscopy is a common clinical tool used to observe vocal fold oscillation, yet it is not appropriate for visualizing the oscillations that contain sub-harmonic waves that often appear in pathological vocal folds. Here, we propose a novel technique based on stroboscopy in which such pathological vocal fold oscillations can be observed by applying FFT (fast Fourier transformation) analysis. We tested two algorithms to determine the stroboscopic illumination frequency : Illuminations on the basis of (i) beat frequency and (ii) multi-light sources. A vocal fold oscillation model with two different fundamental frequencies mimicking pathological conditions such as nodular vocal folds was used to evaluate the performance of the algorithms. The beat frequency was extracted from the sound wave by FFT analysis and used to stroboscopically illuminate the oscillations, demonstrating that the algorithm is useful for observing pathological oscillations, but may be inapplicable to clinical cases because of its low light intensity. In contrast, the alternative algorithm using multi-light sources to illuminate each fundamental oscillation simultaneously showed good performance visualizing the pathological oscillations as well as in the level of clarity, demonstrating that the newly designed laryngo-stroboscopy system is valuable for observing pathological vocal fold oscillations.
The body water (extracellular fluid volume) of a healthy person with constant electric resistivity (47Ω · cm) can be estimated by a body-fat meter using the bioimpedance method. However, for dialysis patients, for whom the management of extracellular fluid volume is very important, accurate estimation is not possible because of individual variation in resistivity depending on kidney function and accumulation of body water. In this study, we investigated the usefulness of a simple method for determining electric resistivity in dialysis patients. Since Posm does not change in ECUM (Extracorporeal Ultrafiltration Method) therapy, which removes only moisture and low molecular weight solute by ultra-filtration, change in extracellular fluid volume can be computed by change in the colloid osmotic pressure with a body water movement model. Experimentally, we measured the serous colloid osmotic pressure and impedance in various parts of the body (right arm, left arm, soma, right leg, left leg) of patients undergoing ECUM treatment. Then we estimated extracellular fluid volume changes using the body water movement model and the amount of fluid removal and serous colloid osmotic pressure measured from the blood. The electric resistivity for each patient could be calculated from the extracellular fluid volume and the impedance in each body part. Using the electric resistivity calculated for each patient, extracellular fluid volume can be estimated by simply measuring the living body impedance. In other words, since the excess and deficiency of body water can be measured quantitatively, it can be used for setting the tolerable level of fluid intake and standard body weight during dialysis. Moreover, extracellular fluid volume can be roughly estimated using the approximate electric resistivity calculated using only the set fluid removal quantity and the measured impedance of each body part in ECUM therapy. Thus, a body water meter specific to each dialysis patient can be made by carrying out ECUM therapy only once and determining the approximate electric resistivity from living body impedance measurement and the set fluid removal quantity and incorporating the approximate value into the so-called body-fat meter.
We propose a reflection-type pulse oximeter that employs two pairs of a light-emitting diode (LED) and a gated avalanche photodiode (APD). One LED radiates a red line with an emission wavelength of 635 nm and the other a near-infrared line with 945 nm. These are driven with a pulse current at frequency ƒ (= 10 kHz). Superposition of a transistor-transistor-logic (TTL) gate pulse on a direct-current (dc) bias, which is set so as not to exceed the breakdown voltage of each APD, makes the APD work in a gain-enhanced operation mode. Each APD is gated at frequency 2ƒ (= 20 kHz), and the signal output is fed into a laboratory-made lock-in amplifier that works synchronously with the pulse modulation signal of each LED at frequency ƒ (= 10 kHz). A combination of the gated APD and lock-in like signal detection scheme is useful for the reflection-type pulse oximeter owing to the capability of detecting a weak signal against a large background light.
This paper describes the development of microcapsules with high disintegration rate efficiency for drug delivery systems (DDS) using shock waves and the design of the microcapsules. The microcapsules, which include a gas bubble, are made by a micro-manipulation system, and it was found that the production possibility depends on the chemical composition of the microcapsule. To obtain the design index of the capsule structure and configuration, a bubble deformation process near a curved elastic wall, which was an experimental model of the microcapsule membrane, was observed and analyzed. The results show that disintegration efficiency depends on the capsule size and Young's modulus of the membrane. As for Young's modulus, the disintegration efficiency peak value was around 100 kPa under several conditions. The Young's modulus of the microcapsule membrane changed with chemical composition, and was determined by comparing the aspirating process of the capsule membrane with the results of finite element analysis. When the apparent Young's modulus of the membrane considering visco-elasticity is more than 250 kPa, microcapsules including gas bubbles can be produced. In this case, the capsule membrane's optimum elasticity for easy disintegration is 250 kPa when considering the above results. Therefore, it is necessary to design a microcapsule with a gas bubble to optimize elasticity for production and ensure high disintegration rate efficiency.