Hidetoshi Miike

Monitoring of heart and respiratory rates by photoplethysmography using a digital filtering technique

An apparatus for simultaneously monitoring heart and respiratory rates was developed using photoplethysmography (PPG) and digital filters, and compared with conventional methods. The PPG signal, which includes both heart and respiratory components, was measured at the earlobe with an original transmission mode photoplethysmographic device. A digital filtering technique was used to distinguish heart and respiratory signals from the PPG signal. The cut-off frequency of the respiratory signal filter was selected automatically depending on the heart rate. Using digital filtering techniques, heart and respiratory signals were separated at rest and during exercise. The digital signal processor was employed to realize an adaptive and real-time filtering. The heart rate was calculated by the zero-crossing method and the respiratory rate from the peak interval of the filtered signal. To evaluate the newly developed monitor, an ECG for heart rate and a transthoracic impedance plethysmogram for respiratory rate were monitored simultaneously. To obtain higher heart and respiratory rates, exercise was performed on an electrical bicycle ergometer. Heart and respiratory rates calculated by the new method compare to those obtained from ECG and the transthoracic impedance plethysmogram. The maximum error of heart and respiratory rates was 10 beats/min and 7 breaths/min, respectively.

An off-line signature verification system using an extracted displacement function

This paper proposes an off-line signature verification system based on a displacement extraction method. The optimum displacement functions are extracted for any pair of signatures using minimization of a functional. The functional is defined as the sum of the squared Euclidean distance between two signatures and a penalty term requiring smoothness of the displacement function. A coarse-to-fine search method is applied to prevent the calculation from stopping at local minima. Based on the obtained displacement function, the dissimilarity between a questionable signature and the corresponding authentic one is measured. The proposed system achieved error rate of 24.9% in a experiment.

Detection of motion fields under spatio-temporal non-uniform illumination

In actual scene analysis, the influence of non-ideal conditions such as non-uniform illumination should be taken into account. The conventional methods for the estimation of motion fields are violated in this situation. In this study, two approaches are proposed to extract reliable motion fields under spatio-temporal non-uniform illumination. These are an extended constraint equation with spatio-temporal local optimization and a pixel-based temporal filtering. Experiments have been made to confirm the performance of the proposed methods and to clarify the difference of characteristics between them.

Detection of Physiological Parameters without Any Physical Constraints in Bed Using Sequential Image Processing.

Physiological parameters, specifically, body movement and respiratory waveform, were observed utilizing an original image sequence processing system. In this study, sequential image processing methods were used to observe both patients with acute myocardial infarction and normal subjects in bed. The results of standard differential image processing and a gradient-based method were strongly correlated with body movement of the subject. Furthermore, the respiratory waveform was detected using the gradient-based method. This image sequence processing system appears very promising for the evaluation of physical activity without any physical constraints in bed.

Evaluation of Body Motion by Optical Flow Analysis

For quantitative evaluation of body motion, a fully noncontact and unconstraining monitoring method was developed by introducing image sequence analysis. A spatiotemporal local optimization method was applied to determine optical flow in the image sequence. The optical flow visualized the apparent velocity field of the entire body motion, including both breast movement of respiration and posture changes in a bed. The experiment was carried out under regulated posture changes and under a sleeping condition by measuring heart rate, respiration and digitized image sequences using a video camera. A temporal increase in heart rate reflected the magnitude of physical activities. We proposed two candidate parameters for evaluation of respiratory and physical activities based on comparison among experimental results. The average of squared motion velocities reflected the magnitude of physical activities. The representative field-averaged component showed a waveform with periodic fluctuation corresponding to that of respiration obtained with a nasal thermistor.

Field theory approach for determining optical flow

Based on the continuity equation, a new approach for determining optical flow from multiple image frames is proposed. The flow velocity of any point in space is computed by a set of constraint equations obtained for more than two points of time, assuming stationary flow field.

Photoplethysmographic measurement of heart and respiratory rates using digital filters

A monitor. for simultaneous recording of heart and respiratory rates has been developed using photoplethysmography (PPG) and digital filters. PPG signal includes both heart and respiratory synchronous components. Digital filtering technique was employed to differentiate between those. With increasing heart and respiratory rates, the cut-off frequency o f filter was changed empirically. Obtained signals agreed with those obtained with ECG and thermistor. The digital filtering technique may provide on-line monitor for heart and respiratory rates.

Hydrodynamic flows traveling with chemical waves

Abstract Hydrodynamic flows are generated by chemical waves propagating in thin solution layers of the Belousov-Zhabotinskii reaction. The sample dishes are covered to prevent flow patterns arising from evaporative cooling. Investigations by space-resolved velocimetry and spectrophotometry reveal that convective flow travels with each circular wave. Flow velocities reach 150 μm/s and surpass the speed of wave propagation. An oscillatory change of flow direction is induced in wave trains emerging from a rotating spiral wave.

Realizing Visual Functions with the Reaction–Diffusion Mechanism

The present paper proposes a computational model for the realization of visual functions of edge and/or feature detection and segmentation. The model utilizes a reaction–diffusion model which is an extended version of the diffusion-based Difference of Gaussians (DOG) filter previously proposed by Marr and Hildreth as an edge detection model. The proposed model self-organizes spatial patterns having edges and/or features and segments. These patterns are sustained by the intrinsic mechanism of the proposed model under specific conditions. In addition, the model also helps to solve the stereo matching problem in random dot stereograms and the aperture problem in optical flow computation. These visual functions of the proposed model are demonstrated with both artificial and real images.

A method for measuring respiration and physical activity in bed by optical flow analysis

A fully noncontact and unconstrained monitoring method, based on optical flow of movement of body surface that is developed by introducing image sequence analysis, is described. A spatiotemporal local optimization method is applied to determine optical flow in the image sequence. The optical flow visualizes the apparent velocity field of the entire body motion, including breast movement due to respiration and posture changes in a bed. A temporal increase in heart rate reflects the magnitude of physical activities. We propose two candidate parameters for evaluation of respiratory and physical activities based on comparison among experimental results. The average of squared motion velocities reflects the magnitude of physical activities. The representative field-averaged component shows a waveform with periodic fluctuation corresponding to that of respiration obtained with a nasal thermistor. This optical flow analysis is a promising new technique for evaluation of body motion for clinical use.