The study of time-varying speckle phenomena observed in light-fields scattered from living objects is reviewed. The laser speckles produced from living objects may be called ‘bio-speckles’ and fluctuate temporally due to various physiological movements such as blood flow. The time-varying properties of the bio-speckles are experimentally investigated from the analyses of the power spectrum and the autocorrelation function. Based on the knowledge of dynamic bio-speckles, some methods are introduced for evaluating blood flow in the skin surface, internal organs, and ocular fundus. The experimental results show that the degree of blood flow is reflected sensitively by the time-varying properties of the bio-speckles and this can be utilized for monitoring the blood flow.

Bio-speckle phenomena and their application to the evaluation of blood flow

New sensor technologies open possibilities for measuring traditional biosignals in new innovative ways. This, together with the development of signal processing systems and their computing power, can sometimes give new life to old measurement techniques. Ballistocardiogram is one such technique, originally promising but quickly replaced by the now very popular electrocardiogram. A ballistocardiograph chair, designed to look like a normal office chair, was built and fitted with pressure sensitive EMFi-films. The films are connected via a charge amplifier to a medical bioamplifier. The system was accepted for medical use in Tampere University Hospital and patient measurements have been performed. The system is presented and it's performance evaluated. A wireless version of the system is needed to hide the cabling from the user. This makes the chair indistinguishable from a normal office chair. Overview of first wireless prototype is given. To analyze recorded BCG, individual BCG cycles must be extracted from the signal containing respiration and movement artifacts. A method for this and results of it's application are presented. The developed system can be used for BCG measurements and it is able to automatically extract individual BCG cycles, but it has some limitations which are presented in the paper.

An EMFi-film sensor based ballistocardiographic chair: performance and cycle extraction method

An unconstrained respiratory rate (RR) and heart rate (HR) monitoring system to be used during sleeping is proposed. The system consisted of eight polyvinylidene fluoride cable sensors, charge amplifiers and measuring software, together with an analogue-to-digital converter unit. The cable sensors were horizontally embedded into a textile sheet on a bed surface covering the upper half of the body. The digital infinite impulse response filters were constructed to extract cardiorespiratory signals from displacement of the sensors. The system software automatically searched the optimum sensor(s) based on the power of the respective filter outputs. Then, the system obtained the 5 s average HR and 15 s average RR by measuring the intervals between the peaks of the respective autocorrelation functions of the filtered output. If the subject changed his posture, the system captured the image of the body position as a time stamp using a CCD camera. To show the validity of this method, the HR and RR obtained by this monitor were compared with those simultaneously measured using respiratory flow and an electrocardiogram. The results showed that the mean frame-by-frame difference ranged from -1.2 to 0.2 beats min(-1) for the HR and, for RR, ranged from -0.8 to 1.4 breath min(-1) during the short-term recordings. Similar differences were obtained during the first 2 h of overnight recordings. The proposed system is feasible for the combined long-term monitoring of a person's RR and HR with sleep posture changes and may be helpful for practical use in the home.

Unconstrained cardiorespiratory and body movement monitoring system for home care.

We have measured noninvasively the embryonic heart rate (HR) of the Japanese quail (Coturnix coturnix japonica), the chicken (Gallus domesticus), the duck (Anas platyrhynchos), the turkey (Meleagris gallopavo), the peafowl (Pavo cristatus), and the Chinese goose (Anser cygnoides) during approximately the last half of the incubation period. The average daily HR was determined over 30 s, every 5 min for 30 min. The HR was variable, particularly toward the end of incubation and during pipping. The time trend of changes in daily HR was similar in quail, chicken, and turkey eggs: a temporal increase occurred at 60%-70% of the incubation period, with a subsequent decrease toward the end of prepipping development, and then an increase with the breathing of air by the lungs. The duck and goose embryos decreased the HR during the last stages of prepipping development. Although the changes in internal pipping HR of the duck were various, the HR of the goose was predominantly increasing during pipping. A gradual inc...

Embryonic Heart Rate during Development of Domesticated Birds

New sensor technologies open possibilities for measuring traditional biosignals in new innovative ways. This, together with the development of signal processing systems and their increasing computing power, can sometimes give new life to old measurement techniques. Ballistocardiogram (BCG) is one such technique, originally promising but later replaced by the now very popular electrocardiogram. It's usability was previously limited by the large size of the devices required to record it, and the complex nature of the recorded signal, which gave little information in visual inspection. In this paper, we present how a lightweight and flexible electromechanical film (EMFi) sensor can be used to record BCG. A ballistocardiographic chair, designed to look like a normal office chair, was built and fitted with two sensitive EMFi sensors. Two different measurement setups to record the signal from the EMFi sensors were developed. The first, so-called wired setup, uses a commercial bio-amplifier, and a special pre-amplifier to interface to it. The latter, so-called wireless setup, uses our own hardware to transmit the recorded digitized signals wirelessly to a nearby PC. Both of these systems are presented and their performance evaluated. Also, the suitability, limitations and advantages of the EMFi sensor over existing sensors and methods are discussed. The validity of the EMFi sensor and amplifier output is tested using a mechanical vibrator. Lastly, a summary of signal analysis methods developed for our system is given. The developed systems have be used for medical BCG measurements, and the recordings indicate that the both the systems are functional and capture useful BCG signal components.

An Electromechanical Film Sensor Based Wireless Ballistocardiographic Chair: Implementation and Performance

A new, noncontact system for measuring the heart rate of avian embryos in the egg has been developed using a laser speckle phenomenon. The system was based upon detection of egg movements attributable to cardiac contractions of the embryo by measuring the intensity fluctuation of speckle produced in the proximity of the egg under laser light illumination (i.e. noncontact measurement). The applicability of the noncontact system to determine the heart rate of developing chick embryos was examined simultaneously with a contact system employing an audio cartridge. Both systems were found to be feasible in determining the heart rate of embryos during the late prenatal and paranatal stages. With the aid of adeques signal processing, the measurement of cardiogenic movements of the egg can be used to count the heart rate during the middle stages of incubation.

Noncontact measurements of avian embryo heart rate by means of the laser speckle: comparison with contact measurements

Using a flexible piezoelectric film, the authors developed a simple system to determine noninvasively the heart rate of chicken embryos and hatchlings. The film was piezoelectric polyvinylidene fluoride (PVDF), which is sensitive enough to detect cardiogenic ballistic movements of the egg (ballistocardiogram (BCG)) and precordial movements of the hatchling attributable to cardiac contractions (apexcardiogram (ACG)). The BCG could be detected, during the second half of incubation, by placing the egg on the PVDF film on a soft substrate. The detected signal was found to be a measure of movement velocity. The ACG could be measured when the hatchling's chest wall made contact with the PVDF film installed in a box in which the hatchling was confined. The heart rate was counted from the lag time of autocorrelation calculated for a certain time segment (e.g. 2s) of the BCG and ACG recordings.

G. C. Whittow

Papers

Noncontact measurements of avian embryo heart rate by means of the laser speckle: comparison with contact measurements

Simple, noninvasive system for measuring the heart rate of avian embryos and hatchlings by means of a piezoelectric film.