This paper introduces a new method for a short-time measurement of bio-impedance in a cross section of local tissue. Validity concerning a new configuration for the electrode and the measurement method has already been done using three-dimension numerical analysis as reported in a previous paper. In this paper, we focus on living tissues represented by an equivalent circuit model. A model in the cross section of the tissue can be substituted for a distribution equivalent circuit, and the parameter of impedance is estimated using the Gauss-Newton method. Simulation results show that the parameter for contact impedance, fat, mammary, muscle and tumor layers can be estimated with an error of less than 0.01%.
Intrinsic optical imaging has been widely used to elucidate functional architectures in the cerebral cortex. Although several methods have been invented to visualize the functional architectures from intrinsic signals, which are very small, they are limited to extracting them because they don't take into account the tuning properties of optical signals. We propose here a new method to represent functional maps on stimulus selectivity at each local region by calculating the correlation coefficient between the optical signals and the tuning curve model. We have applied it to the visualization of orientation preference columns in the cat visual cortex. The extracted maps from the new method have a higher contrast than maps created using the conventional method, resulting in orientation preference columns that are clearly identifiable.
As the result of developments in computer technology in recent years, the calculation, simulation and analysis of the stress environment for the artificial hip prosthesis and the femur have been made possible. In order to perform an exact calculation, three-dimensional modeling with the hip prosthesis and femur is required. The modeling of a femur is done by reconstructing the femoral outline data from CT images using three-dimensional CAD. The outline extraction work is performed by the experience and subjectivity of the operator, and the reliability of the data and working efficiency is low. In this paper, algorithms that extract the femur outline from CT images automatically are proposed. A Snake-based outline extraction algorithm is used. Although this method is capable of extracting the cortical bone outline of femoral diaphysis with sufficient accuracy, there was high incorrect detection at the trochanter. The shape of the trochanter is complicated, and it is difficult to process using a simple algorithm. Therefore, we proposed a method of visually expressing the possibility that a certain pixel in an image is high or low. This method is capable of detecting portions of images with high differentiations in value (contrast changes rapidly). It can also detect outlines at the diaphysis and trochanter. The problems of this technique are that the pixels judged as possibly being a part of the outline appear in the portion that is not a true outline, and that the pixels judged as possibly being on the outline may not be continuous. When each method was used independently, neither was capable of performing a positive outline extraction. However, an outline sampling sufficiently high certainty was achieved when using the two methods simultaneously.
The purpose of this study is to develop a new technique for the quantitative evaluation of spasticity in the ankle joint of hemiplegic patients. Each subject sat on a bed, and his/her foot was supported with a jig to measure the ankle joint angle. The subject was instructed to relax and not to resist the application of a step-like load, which was applied to dorsiflex the ankle joint. The ankle joint angle and electromyograms of the soleus muscle and tibialis anterior muscle were measured. First, the step-like response was approximated with a proposed mathematical model based on musculoskeletal and physiological characteristics using the least squares method in order to estimate net inertia, elastic coefficient and viscous coefficient of his/her foot. The proposed model involved an elastic component depending on both muscle activities and ankle joint angle. The responses were approximated well with the proposed model. Next, the torque generated by the elastic component was estimated. Then the normalized elastic torque was approximated with a dumped sinusoid using the least squares method. The time constant and frequency of the normalized elastic torque were calculated. The time constant and frequency of hemiplegic subjects varied depending on the step-like load, but those of healthy subjects didn't vary. This suggests that the proposed method provides a good quantitative index of spasticity, as shown in the relationship between the time constant and frequency of the normalized elastic torque.
The aim of this research is to develop a human-computer interface system for quadriplegic patients. In this study, we developed a two-channel human-computer interface system for inputting characters of the Japanese language using mandibular and tongue movement. The interface consists of a polymer mouthpiece and a slide potentiometer. Operation involves the user looking at character patterns displayed on a PC screen and selecting elements by making a 'biting' movement with the upper and lower incisors. The final selection of a character element is made by pushing a switch with the tip of the tongue. The display is a two-dimensional matrix composed of 50 syllables of the Japanese alphabet, as well some symbols used in writing. The operator first selects the line of the character element, and then the column corresponding to the element of choice. The illumination of a pilot lamp provides the user with a visual means of confirming the exact position of the character element selected. The time taken for the whole operation was recorded. Two subjects carried out the experiments over a period of three days. It was possible to input Japanese syllables in about 4 s.
Pressure ulcers are an ischemic necrosis caused by sustained mechanical loads. We measured blood flow using a laser Doppler flowmeter to investigate the quantitative relationship between pressure and shear force on the body surface. Constant pressure and shear force were applied to the forearm (A: soft tissue) and processus styloideus ulnae (B: bony prominence) using a pneumatic pressure device attached to a measurement probe. In the case of A, blood flow decreased as pressure load was increased. It is possible that there is a several-fold force in bony prominence for the comparison of B (50 mmHg) with A (100 mmHg). If shear force is applied, the shear force (0.9 N/cm2) might be approximately equivalent to the pressure (50 mmHg) under the comparison condition of A (50 mmHg and 0.9 N/cm2) with A (100 mmHg). These results suggest that the reduction of shear force against the tissue surface is essential to prevent the crisis of pressure ulcers in addition to normal pressure.
In this study, we present a new method for constructing panorama images from a series of coronary cineangiograms. The obtained panorama images enable us to observe a complete coronary at a glance. In order for medical staff to take angiocardiographic images, one often has to move a patient's bed in order to catch the vessels to be visualized in the viewing field after injecting a contrast medium. Moreover, those vessels are usually in consistently contrasted because it takes time for the contrast medium to reach the end of every vessel. In this study, we present a method that reduces such inconvenience and constructs useful coronary images for clinical diagnosis. First, we roughly estimate the heartbeat cycle and the bed movement using a spatiotemporal image generated from a series of original coronary cineangiograms. Next, we group each angiocardiogram frame based on heartbeat phase and estimate the bed movement spatiotemporally. Panorama images can then be obtained by merging a few frames in the same heartbeat phase with a composite background image. This makes it possible to easily observe a contrasted, complete coronary in a still viewing field.
Although Legionnaires' disease is an issue of global importance, the isolation of Legionella species is a lengthy process requiring incubation on agar plates for more than one week. A method for rapid detection is therefore required to restrict the increasing range of Legionnaires' disease and to control Legionella species. While the nucleic acid amplification test (NAT) has been applied to bacterial screening, it has not yet been applied for the detection of the few Legionella species commonly found in large environmental water bodies like hot springs given the relative limits of the sample volumes that can be processed using NAT. We therefore designed a genetic detection system using a metal-coated flat sheet (MCFS) membrane for Legionella species that operates as follows: The MCFS-membrane is coated with silver on a flat filtration membrane. Legionella species become concentrated on the MCFS-membrane when water from a hot spring is aspirated through the membrane. The genes of the Legionella species that become concentrated in the membrane are then isolated by applying an electric field. Legionella species can then be identified by polymerase chain reaction (PCR) using specific primers. Here, we report the first attempt to detect Legionella species from various hot springs. A 10-μm-pore size MCFS-membrane captured approximately 30% of the Legionella species in the hot spring. Genes were isolated from most of the Legionella species in the MCFS-membrane when an electric field of 20 V/cm was applied to the membrane before PCR amplification. In addition to detecting Legionella species, this technique also facilitated bacterial concentration and genetic isolation. Amplification of DNA was not inhibited by hot spring components or proteins and lipids derived from humans, as these were removed by the MCFS-membrane. The time required for bacterial identification using this method was shortened to four hours.
Most patients with osteoarthritis of the knee (OA knee) have cartilages that are worn out and transformed inside of the knees. Structurally, the load rests upon the inside of the knees when the tibia doesn't rotate externally against the thighbone. Therefore, we believe that a good method for preventing OA knee is to rotate the tibia externally against the thighbone. To enable this we developed shoes, which we call SHM shoes, to suppress Reverse-SHM. The soles of the shoes have screw-shaped rubbers which create external rotational moment when landing. In this paper, we examined the effectiveness of the SHM shoes. The subjects were three females without OA knees in Experiment 1 and three females with OA knees in Experiment 2. They walked wearing normal shoes and four kinds of SHM shoes. We measured the angles of tibia rotation against the thighbone. As a result of the experiments, compared to actions when normal shoes were worn, it was shown that the patients' tibia rotated externally immediately after the soles contacted the ground at all times SHM shoes were worn. In other words, the results suggest that SHM shoes are able to curb Reverse-SHM.
This research proposes a self-optimizing hanging protocol for the viewing station of DR (digital radiography) diagnosis. The hanging protocol can manage several image sizes (film-sizes) corresponding to the level of importance. The protocol creates four patterns automatically, which become candidates of the optimal hanging pattern. These patterns are created by the combination of three basic operations, which are “screen separation,” “image zoom factor,” and “image order.” Then, the protocol selects the optimizing pattern dynamically using three evaluation measures, which are “resolution,” “ordering,” and “utilization.” Using the hanging protocol, the medical doctor and radiologists can obtain an efficient reading by decreasing mouse operation.
In this paper, we describe a method for recognizing hand motions using a multi-channel surface electromyogram (SEMG), in which the channels are selected using the Monte Carlo method. SEMG measured for the skin surface is widely used as an information source to determine various types of body movements. In our system, we use a 96-channel matrix-type (6×16) surface electrode attached to the forearm in order to measure the SEMG generated from many active muscles during hand movement. In our system, it is very important to select 16 channels that are suitable for recognition from the 96 channels available for the multi-channel electrode. This can be achieved using the Monte Carlo method as follows. The system first generates 1,000 randomly selected 16-channel sets for the multi-channel electrode. These sets are evaluated for the recognition rate of hand movement, and the set of 16 channels that records the highest recognition rate is used for real-time recognition. Using this method, we can select a suitable measurement position of SEMG for each subject. Seven normal subjects were experimentally tested using our system. The recognition rates of 18 hand motions, including 10 finger movements, were assessed for every subject. Using the proposed method, we were able to distinguish all the motions, and the average recognition rate in the real-time recognition experiment was measured to be greater than 97%. We thus conclude that our proposed method will be useful for the recognition of hand motion.
In this study, to eliminate the motion artifacts contaminating photoplethysmograpic (PPG) signals, a clip-type earlobe photoplethysmography sensor was improved and a noise-reduction algorithm based on a multiple-regression model was examined. Motion artifacts are thought to be caused by a change in the flow of blood. We thought that such motion artifacts could be reduced considering the acceleration change during body motion. In this study, an acceleration sensor was integrated with a commercially available clip-type earlobe PPG sensor. For the first step, typical motion artifact waveforms were calculated by choosing every motion artifact waveform, arranging the peak time and averaging. In the second step, to make a multiple regression analysis between averaged acceleration and averaged motion artifact waveform, regression coefficients were calculated. Finally, an original PPG signal with motion artifact was filtered using an individually adjusted multiple regression model. In experiments, five subjects were asked to walk and run on a treadmill to verify this filtering method. Results show that our new motion artifacts reduction algorithm is proven to be effective for decreasing the influence of body motion, and the detection accuracy of the number of pulsations has improved up to 13.3%.
The falling asleep period is the time when one shifts from being awake to sleep stages 1 and 2. The change during this period can be observed by monitoring brain waves. In this research, we developed a technique to presume the shift of sleeping depth during the period of falling asleep by monitoring brain waves. We used a Lorenz Plot for the heart rate RRI during the falling asleep period, enabling us to confirm that a change took place on the distribution of the Lorenz Plot, according to the change that occurred during the sleep stage. To evaluate the change in these distributions, we projected a Lorenz Plot on the y-x axis, and analyzed shifting of the center and variation in each sleep stage. As a result, the distance from the starting point to the center of distribution became longer for sleep stage 1 and sleep stage 2, and sleep became deeper from the waking stage. Distributions also began to stabilize gradually as the sleep stage became deeper, though they varied widely and were unstable during the waking stage. Evaluating these phenomena quantitatively, we can easily estimate the pathology of the sleep stage when one is falling asleep.
To realize an accurate cardiovascular dynamics simulation that represents the change in blood pressure and blood flow in the left ventricle (LV) and blood vessels, it is necessary to provide the left ventricular model and circulation model together with a coupling calculation algorithm of both models. Previous studies have employed a time-varying elastance model in which a coupling calculation with a circulation model is easy to realize. However, there has been a problem that it is difficult to simulate heart disease caused by damage to ventricular cell functions. On the other hand, the LV mechanical model, which uses a relationship between the shape and contraction force of myocardial cells such as the finite element method (FEM), is effective to analyze various aspects of cardiovascular dynamics. However, since the FEM-based LV mechanical model requires convergence calculation, it is not easy to exchange circulation models to be coupled. In this study, we propose a flexible simulation system by which the simulation models can be easily exchanged. The system is constructed with independent simulators for a left ventricular mechanical model and a circulation model. We have realized a coupling calculation algorithm that is capable of calculating cardiovascular dynamics from these two models.
Due to the experimental limitations in studying human heart functions, the use of computer simulation is becoming more and more important. However, research on the contraction model of the ventricular cell and propagation model of the excitation wave have mainly been studied independently despite the fact that myocardial excitation—contraction coupling is fundamental to the heart function. In this article, an excitable contraction model of ventricular tissue cable is constructed to study the effect of different stimulating patterns on tissue contraction. The contraction force for each element is calculated based on an electro-physiological ventricular cell model (Kyoto Model). The mechanical deformation of tissue is solved using the finite element method. The electrophysiological calculation and mechanical calculations are coupled to obtain a simulation reflecting the force-length relation of the myocardial cell. Several factors such as the starting point and conduction velocity of stimulation signals affect contraction behavior. Here, we show that the activation time (AT), which is the time the stimulation signal needs to spread over the tissue, is a dominant indicator for determining the tissue contraction force. When AT decreases, the tissue contraction force increases monotonically. This fact suggests that the minimization of AT could be an important clue for achieving effective tissue contraction. Furthermore, the effect of increasing stimulating points has been analyzed. Simulation data suggests the importance of the number and position of pacing leads to improve the pump function of a failing heart in cardiac resynchronization therapy such as biventricular pacing.
Recently, much research has been done to evaluate mental stress based on heartbeat fluctuation and lower restraint, and a non-invasive ECG measurement method is been expected to be able to record the heartbeat during daily life. In this study, a new ECG measuring method that uses capacity coupled electrodes without any reference electrode is proposed. In this paper, five different settings of signal electrodes and ground connections were compared: One capacity coupled signal electrode with no ground electrode, two capacity coupled signal electrodes with no ground electrode, two capacity coupled signal electrodes with a common ground electrode on the skin, one capacity coupled signal electrode with one capacity coupled ground electrode, and two capacity coupled signal electrodes with the amplifier grounded. We also examined our new ECG measurement method under different electrical environments: in a noise-filled laboratory, outdoors with no commercial electrical power nearby, and inside a car with the engine and air conditioner operating. As a result, our new measurement method proved to be effective for obtaining ECG signals during daily life.
Bone-conducted ultrasounds (BCUs) can be perceived by the profoundly deaf, who hardly sense sounds even with conventional hearing aids, as well as normal-hearing subjects. A bone-conducted ultrasonic hearing aid (BCUHA) was developed for the profoundly deaf. With the BCUHA, ultrasounds at about 30 kHz are amplitude-modulated by speech sounds and presented to the user's mastoid by a vibrator, and users can perceive demodulated speech sounds. The basic parameters of the BCUHA were determined from the results of our former studies of the characteristics of BCU perception. Psychoacoustical tests were carried out to evaluate the utility of the BCUHA. The results showed: (1) more than 40% of profoundly deaf subjects were able to perceive sounds and 17% were able to recognize words using BCUHA; (2) articulations for Japanese monosyllables were about 60%; and, (3) intelligibility for familiar 4-mora Japanese words reached 80%. These results indicate the practicability of BCUHA.
It is reported that the wall shear stress affects the biochemical function of endothelial cells such as the production of nitric oxide (NO), which has an anti-arteriosclerosis effect, and the generation and development of arteriosclerosis plaque. On the other hand, the shear stress in a stream distant from the wall also provides important information, and it is reported that the stream shear stress affects the deformation of erythrocytes. Therefore, if these intravascular shear stresses can be assessed quantitatively and noninvasively, it is expected that useful information can be supplied for the prevention of arteriosclerosis. The conventional method for shear stress estimation, which combines vascular reconstruction using MRI or IVUS, and CFD requires improvements in order to provide real-time processing and more a quantitative estimation. In this paper, a novel method that enables a real-time, quantitative estimation of intravascular shear stress distribution is proposed. It is based on using Newton's law of viscosity and the estimated viscosity coefficient and shear rate obtained by ultrasonic velocity measurement. An experimental investigation was performed in which two types of fluids with different viscosity coefficients (water, and water mixed by PVA) were flowed at a constant flow rate (20 mL/s) in a silicone tube with a plaque-like step. After ultrasonically measuring the velocity vector distribution in the tube, the viscosity coefficient, shear rate and shear stress were estimated based on the proposed method. Using the proposed method, the averaged error in the estimated value of the viscosity coefficient compared to the value measured using a viscometer was 9%. The averaged value of the shear stress distribution estimated in the higher viscosity fluid (water mixed by PVA: 1.0 Pa) became larger than that in the lower viscosity fluid (water: 0.2 Pa). These results reveal that the proposed method is technically valid for quantitative shear stress estimation.
The use of electronic patients' record systems has been realized in many hospitals. Such systems make it easier to retrieve information than referencing paper records. Doctors and assistant medical staff must both refer to the same medical records for current patients. Medical records consist of sentences that have an attribute of clinical process. The clinical process cycle is comprised of three attributes: observation, diagnosis and treatment (hereafter abbreviated as “ODT”). Generally, the ODT cycle is a sequence of sentences that defines the structure of a record. The flow of attributes is interpreted as the context of a medical record. It is important for doctors to consider the context of each related document. However, if the records retrieved are not related to the context of the current matter, there is no need to refernce them. We propose a context—based similarity measurement model for retrieving medical records. The model exploits ODT cycles to calculate similarity values in the records. In a document, the model takes account of relations between sentences when two sentences have the same attribute (s) or sentences have a sequential attribute in a continuous ODT cycle. When two records have a homogeneous relation, the model measures the similarity between the documents. Then, similarity values between the records are referred to in a matching and ranking retrieval process. The proposed model was evaluated in two experiments. While there isn't much difference in matching between the model and a vector space model that measures similarity values by counting the term frequency included in two records, the proposed model is superior to the vector space model in terms of ranking. We conclude that the context—based model should be adapted in combination with the vector space model in order to execute effective retrieval.
This paper presents a method of volume segmentation for brain fluorodeoxyglucosepositron emission tomography (FDG-PET) images using a Gaussian mixture model (GMM). In FDG-PET diagnosis, an abnormal decrease of regional cerebral glucose metabolism (CMRGlc) should be discriminated from one caused by normal brain atrophy as the effect of aging. To achieve it without any incorporation of a structural image such as magnetic resonance imaging (MRI), a volumetric study on FDG-PET image sequences should be performed; thus, a robust method for volume segmentation with CMRGlc is required. The proposed method assumes that the probabilistic distribution of CMRGlc has three groups; originated from the gray matter, white matter, and cerebrospinal fluid space. Two consecutive GMM runs successfully clustered FDG-PET images into three clusters resulting in robust volume segmentation without any heuristic operation such as thresholding. The proposed method was applied to FDG-PET images from 71 healthy volunteers, and a significant increase in the low CMRGlc region on age was observed. We conclude that successive GMM is useful for the segmentation of PET FDG images.
We developed a parallel wire drive system as a control device for tele-echography. We designed the construction of the handle, which a medical doctor operates, and the location of six actuators connected to the handle via cables by introducing the Force Closure theory. The actuator adjusts cable tension by calculating the length of the cable. Using the six parallel wires, a doctor can send a 5-dimensional position command by controlling the handle in the same way as commonly done during ultrasound diagnosis, translation, rotation to a medical robot and feeling the contact force on the body surface of a remote patient abdomen. It's also possible to use the device for echography training.
Examination by echography greatly depends on the expertise and experience of the operator, though there is no research to assist the handler of the ultrasound probe. If cross sections of internal organs are automatically recognized from the echogram, it is possible to provide a position feedback system for the operator, which may also act as a guidance system for inexperienced operators. We have developed an algorithm to recognize a cross section of the heart from successive echograms. We first divided an echogram into sub-regions and detected the position of the mitral valve by the analyzing brightness variation and the correlation coefficient between sub-regions. We confirmed that recognition of the mitral valve corresponds to the motion of the ultrasound probe with reliable accuracy. Furthermore, combining this technique with an optical flow method, we elucidated the contract velocity of wall motion in eight radial regions by centering the mitral valve. Finally, we recognized a short-axis view of the heart by comparing the correlation of the contraction velocity between specified regions.