Reconstruction of sequential cardiac in-plane displacement patterns on the chest wall by laser speckle interferometry
TL;DR: Time-average speckle interferometry has been applied to obtain displacement patterns on the chest wall produced by cardiac action, in the absence of breathing, during various phases of the cardiac cycle and the functional details of the normal heart are outlined.
Abstract: Time-average speckle interferometry has been applied to obtain displacement patterns on the chest wall produced by cardiac action, in the absence of breathing, during various phases of the cardiac cycle. This has been achieved by an electronic shutter, controlled by the electrocardiogram of the subject. The recorded holographic plates processed under identical conditions are scanned by the pointwise method to obtain the absolute displacements at various locations corresponding to the activities of the various cardiac chambers and valves. These data are transformed to a 40*30 matrix by an interpolation method and, from this, three-dimensional displacement plots are reconstructed by an IBM PC/AT computer. These patterns show the displacements over the entire cardiac area corresponding to the activities of various regions during the cardiac cycle. The apex and aortic valve areas show the maximum displacements during the systolic phase. During the diastolic phase the activities over the low-pressure atrial regions are also observed. The results obtained outline the functional details of the normal heart and the activities over various areas are in agreement with those obtained by other noncontact techniques. >
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TL;DR: An analytical model is developed to perform and interpret the spectral analysis of vital signs from the spectrum of recorded waveforms, using an impulse-radio (IR) UWB radar, and a canceler to cancel out breathing harmonics is proposed to improve heart rate detection.
Abstract: Ultra-wide Band (UWB) technology is a new, useful and safe technology in the fleld of wireless body networks. This paper focuses on the feasibility of estimating vital signs | speciflcally breathing rate and heartbeat frequency | from the spectrum of recorded waveforms, using an impulse-radio (IR) UWB radar. To this end, an analytical model is developed to perform and interpret the spectral analysis. Both the harmonics and the intermodulation between respiration and heart signals are addressed. Simulations have been performed to demonstrate how they afiect the detection of vital signs and also to analyze the in∞uence of the pulse waveform. A fllter to cancel out breathing harmonics is also proposed to improve heart rate detection. The results of the experiments are presented under difierent scenarios which demonstrate the accuracy of the proposed technique for determining respiration and heartbeat rates. It has been shown that an IR-UWB radar can meet the requirements of typical biomedical applications such as non-invasive heart and respiration rate monitoring.
324 citations
Cites background from "Reconstruction of sequential cardia..."
...1 mm and several millimeters, depending on the person [18]....
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TL;DR: A Ka-band transceiver using low-power double-sideband transmission to detect human heartbeat and respiration signals is demonstrated, and the detection accuracy is significantly improved with low transmitted power.
Abstract: A Ka-band transceiver using low-power double-sideband transmission to detect human heartbeat and respiration signals is demonstrated. The Ka-band electromagnetic wave offers higher detection sensitivity on small movement due to its shorter wavelength. Indirect-conversion receiver architecture is chosen to reduce the dc offset and 1/f noise that can degrade the signal-to-noise ratio and detection accuracy. Furthermore, the double-sideband signals at the transmitter output can be in quadrature by choosing a proper frequency separation to relieve the severe null point problem that occurs at high frequency. As a result,the detection accuracy is significantly improved with low transmitted power. This radar sensor system achieves better than 80% detection accuracy at a distance of 2.0 m with a combined transmitted power of only 12.5 /spl mu/W in both sidebands.
279 citations
04 Dec 2006
TL;DR: In this article, the authors analyzed the harmonics observed in phase-modulated Ka-band Doppler radar, explaining the reason for better heartrate accuracy when detected from the back of the body.
Abstract: The accuracy of a Ka-band physiological movement detector was tested and compared for measurements from four different body orientations and at five different distances. A rigorous spectral analysis approach is developed when previously adopted small-angle approximation model is not applicable. This theory analyzes in detail the harmonics observed in phase-modulated Ka-band Doppler radar, explaining the reason for better heart-rate accuracy when detected from the back of the body. It also explains the advantage of double-sideband transmission in avoiding the null point problem. Simulations have been performed to illustrate this theory and provide design guidelines for the system. This theory has also been verified by experiments
237 citations
TL;DR: In this article, a flexible sensor based on an FBG encapsulated into Dragon skin 20 silicone rubber was used for developing a wearable system for respiratory and cardiac rates' monitoring, which was evaluated on healthy volunteers to evaluate its suitability for monitoring respiratory frequency and heart rate.
Abstract: There is a growing demand for strain sensors that can be embedded into wearables for several potential applications. Among others, respiratory and cardiac rates’ monitoring from chest wall displacements have driven the development of strain sensors based on fiber Bragg gratings (FBGs) coupled with polymers. In this paper, we addressed the fabrication of a flexible sensor based on an FBG encapsulated into Dragon skin 20 silicone rubber. The sensor is intended to be used for developing a wearable system for respiratory and cardiac rates’ monitoring. The sensor’s response to strain, temperature changes, and relative humidity variations has been experimentally assessed. By considering the repetitive strains induced on the chest wall by the phenomena of interest, the hysteresis response has also been analyzed. Then, an elastic band was equipped with the flexible sensor. The feasibility of this wearable system has been preliminarily assessed on healthy volunteers to evaluate its suitability for monitoring respiratory frequency ( $f_{\mathbf {R}}$ ) and heart rate (HR). The interesting results suggest that the proposed system is easy to be worn, non-invasive, stretchy, and seems to be suitable to well-match the chest wall displacements for monitoring $f_{\mathbf {R}}$ and HR. Such findings call for further investigation targeted to evaluate the accuracy of the FBG-based wearable system in monitoring respiratory and cardiac activities and the system usability in both clinical and sports sciences.
128 citations
23 Apr 2007
TL;DR: In this paper, the effects of non-linear cosine transfer function in non-contact vital sign detection have been analyzed theoretically and demonstrated by simulation based on a model developed in ADS.
Abstract: Simulations were performed based on a model developed in ADS to demonstrate the effects of non-linear cosine transfer function in non-contact vital sign detection. Harmonics and intermodulation effects have been analyzed theoretically and demonstrated by simulation. It is shown that in contrast to the observation from simple linear approximation that detection sensitivity always increases with carrier frequency, there is an optimum carrier frequency for non-contact Doppler radar vital sign detection. For typical values of human chest wall movement, the simulation shows that the upper bound of the carrier frequency should be limited to the lower region of the Ka-band to improve detection accuracy
125 citations
Cites background from "Reconstruction of sequential cardia..."
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References
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TL;DR: In this paper, the distribution of scale sizes in a speckle pattern (i.e., the Wiener spectrum) is investigated from a physical point of view, and it is shown that adding M uncorrelated speckles on an intensity basis can reduce the contrast by 1/√M.
Abstract: A speckle pattern formed in polarized monochromatic light may be regarded as resulting from a classical random walk in the complex plane. The resulting irradiance fluctuations obey negative exponential statistics, with ratio of standard deviation to mean (i.e., contrast) of unity. Reduction of this contrast, or smoothing of the speckle, requires diversity in polarization, space, frequency, or time. Addition of M uncorrelated speckle patterns on an intensity basis can reduce the contrast by 1/√M. However, addition of speckle patterns on a complex amplitude basis provides no reduction of contrast. The distribution of scale sizes in a speckle pattern (i.e., the Wiener spectrum) is investigated from a physical point of view.
2,093 citations
TL;DR: In this paper, a noninvasive and noncontact technique based on the principle of laser speckle interferometry has been developed to record the cardiac displacements observed on the chest wall.
Abstract: A noninvasive and noncontact technique based on the principle of laser speckle interferometry has been developed to record the cardiac displacements observed on the chest wall. These displacements are then reconstructed in the form of three-dimensional plots, during the P, QRS and T-waves of the ECG. A comparison of these patterns shows that the mechanical activity of each region varies significantly during these phases of cardiac cycle. As these displacements depend on the clinical status of the heart, its use with a cardiac patient shows the functional changes of the affected regions in the form of alteration of these patterns.
83 citations
39 citations
TL;DR: In this article, two new techniques making use of the scattered-light speckle pattern have been developed which yield the displacements on an arbitrary interior plane of a 3D body.
Abstract: Two new techniques making use of the scattered-light speckle pattern have been developed which yield the displacements on an arbitrary interior plane of a 3-D body. When a sheet of coherent light passes through a transparent 3-D body, a small fraction is scattered. This scattered light produces a speckle pattern in an imaging system. By recording two superimposed images of this speckle pattern, one before and one after body deformation, the displacements on the interior illuminated plane can be found. The technique of scattered-light photography uses a single illuminating beam and is sensitive to displacements greater than one speckle diameter, approximately 3 μm. Scattered-light speckle interferometry uses two illuminating beams and is sensitive to displacements greater than one half the wavelength of light being used, approximately 0.2 μm. With both techniques, the double-exposed speckle photograph is optically processed to yield displacement information. With both techniques, the maximum displacement measurable is limited by correlation requirements between the two speckle patterns. Experimental results are presented demonstrating the two new techniques.
39 citations
TL;DR: The results indicate that the DCG can be employed as a reliable noninvasive method for repetitive assessment of the pattern of contraction of the anterior, anterolateral and posterior left ventricular wall.
Abstract: The displacement cardiograph (DCG) is a noninvasive device employing an electromagnetic field to record tissue motion within the body. The sensing coil need not be in contact with the patient since the field penetrates air and stationary tissue without significant distortion. Disturbances in the field with result from ventricular wall motion are electronically converted to an analog output and a pattern inscribed on the paper of a physiological recorder. In an attempt to determine the reliability of the DCG in detecting regional areas of abnormal left ventricular wall motion, displacement cardiograms were obtained from 70 patients who underwent cardiac catheterization and left ventriculography. The DCG interpretations were in agreement with the ventriculographic picture of left ventricular wall motion in 67 of the 70 patients. There were two false positive and one false negative DCG diagnoses. The results indicate that the DCG can be employed as a reliable noninvasive method for repetitive assessment of the pattern of contraction of the anterior, anterolateral and posterior left ventricular wall.
31 citations