Contact-less, Multi-Spectral Imaging of Dermal Perfusion
12 May 2008-pp 793-796
TL;DR: A variation of the accepted PPG technique is described, to provide a contact-less and non-invasive method of characterizing dermal perfusion, which employs a 3-CCD, multi-spectral camera, to image the selected area.
Abstract: Photoplethysmography (PPG) has come to be accepted as a common, non-invasive method for measuring the level of oxygen saturation in arterial blood. This paper describes a variation of the accepted PPG technique, to provide a contact-less and non-invasive method of characterizing dermal perfusion. It employs a 3-CCD, multi-spectral camera, to image the selected area. The acquired images are analysed by making use of the fact that the absorption co-efficient of oxygenated blood is more in the infra-red (IR) region of the spectrum, when compared to the red region. This fact is utilised to characterize the extent of dermal perfusion in the selected area of the skin.
Citations
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Patent•
27 Aug 2012TL;DR: In this paper, a camera (1, 1') for generating a biometrical signal of a living being comprising of a filter (11, 12) for blocking incident visible light in a wavelength range up to at least 550 nm, a color sensor (12, 12') for receiving said filtered incident light and generating at least two different color signals (5, 6, 9), a combination unit (15, 16, 17), and a processing unit (16) for processing said at least one combined color signal and extracting at least 1 biometric signal of said living being.
Abstract: The present invention relates to a camera (1, 1') for generating a biometrical signal of a living being comprising: a filter (11) for blocking incident visible light in a wavelength range up to at least 550 nm, a color sensor (12, 12') for receiving said filtered incident light and generating at least two different color signals (5, 6, 9), a combination unit (15) for generating at least one combined color signal (7a, 7b) by combining said at least two color signals, and a processing unit (16) for processing said at least one combined color signal and extracting at least one biometrical signal (8) of said living being (3).
30 citations
Patent•
01 Oct 2010TL;DR: In this paper, a plurality of sub-sets of pixel values are formed by selecting a sub-set of at least one pixel value from each image defining an interval to form a group (21) of associated subsets.
Abstract: A method of forming a time- varying signal representative of at least variations in a value based on pixel values from a sequence of images, the signal corresponding in length to the sequence of images, includes obtaining the sequence of images. A plurality of groups (21) of sub-sets of pixel values are formed by selecting a sub-set of at least one pixel value from each of at least two images defining an interval to form a group (21) of associated sub-sets. For any pair of groups (21) with only sub-sets from the same images, the sub-sets from more than one image are different. Groups (21) of sub-sets are selected to form the signal in accordance with at least one selection criterion. The selected groups (21) of sub-sets cover different intervals, shorter than a length of the sequence
26 citations
TL;DR: A novel camera array for multi-spectral imaging is presented in this article, which enables the formulation of novel registration and reconstruction algorithms to globally set up robust models and ensures not only a superior spatial, but also a high spectral, and temporal resolution.
Abstract: Recently, many new applications arose for multi-spectral and hyper-spectral imaging. Besides modern biometric systems for identity verification, also agricultural and medical applications came up, which measure the health condition of plants and humans. Despite the growing demand, the acquisition of multi-spectral data is up to the present complicated. Often, expensive, inflexible, or low resolution acquisition setups are only obtainable for specific professional applications. To overcome these limitations, a novel camera array for multi-spectral imaging is presented in this article for generating consistent multi-spectral videos. As differing spectral images are acquired at various viewpoints, a geometrically constrained multi-camera sensor layout is introduced, which enables the formulation of novel registration and reconstruction algorithms to globally set up robust models. On average, the novel acquisition approach achieves a gain of 2.5 dB PSNR compared to recently published multi-spectral filter array imaging systems. At the same time, the proposed acquisition system ensures not only a superior spatial, but also a high spectral, and temporal resolution, while filters are flexibly exchangeable by the user depending on the application. Moreover, depth information is generated, so that 3D imaging applications, e.g., for augmented or virtual reality, become possible. The proposed camera array for multi-spectral imaging can be set up using off-the-shelf hardware, which allows for a compact design and employment in, e.g., mobile devices or drones, while being cost-effective.
22 citations
Patent•
06 Sep 2010
TL;DR: In this article, a system for detecting signals of the PPG type from a biological tissue, including a supporting area (2') for a portion of the tissue, a matrix (2) of nxm elementary optical receivers, and means for forming an output signal of each elementary receiver, depending on radiation which it receives from a tissue bearing upon the supporting area and as a function of time, was presented.
Abstract: The invention relates to a system (1) for detecting signals of the PPG type from a biological tissue, including: a) a supporting area (2') for a portion of the tissue, b) a matrix (2) of nxm elementary optical receivers, and means for forming an output signal of each elementary receiver, depending on radiation which it receives from a tissue bearing upon the supporting area and as a function of time, c) means for forming a PPG signal from the output signals of the receivers of the matrix.
8 citations
05 May 2009
TL;DR: A virtual instrument developed for acquiring a series of visual and near infrared images of the affected area and subsequent off-line analysis and presentation of the results for stimulated dermal perfusion and inhibition is described.
Abstract: Determining the extent of dermal perfusion is crucial in assessing the healing of chronic wounds, of the kind encountered in diabetic ulcers and burns. An automated, contact-less, non-invasive means of analyzing the dermal perfusion in selected areas would be useful in this process. Such a technique is presented in this paper. It describes a virtual instrument developed for acquiring a series of visual and near infrared images of the affected area and subsequent off-line analysis and presentation of the results. The virtual instrument has been tested with satisfying results for stimulated dermal perfusion and inhibition.
2 citations
Cites background from "Contact-less, Multi-Spectral Imagin..."
...The authors’ work on evolving a contactless and noninvasive technique for determining dermal perfusion has been presented earlier [ 6 ]....
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References
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01 May 2007
TL;DR: In this article, a singular value decomposition (SVD) based method is proposed to reduce motion artifacts from corrupted PPG signals, which is shown to achieve stable and reliable SpO2 measurement even when PPGs are distorted by motion artifacts.
Abstract: Artifact free photoplethysmographic (PPG) signals, obtained with red and infrared (IR) optical sources and detectors are necessary for non-invasive estimation of oxygen saturation (SpO2) in arterial blood. Movement of a patient corrupts the PPGs with motion artifacts, resulting in large errors in the computation of SpO2. This paper presents a novel singular value decomposition (SVD) based method to reduce motion artifacts from corrupted PPG signals. Test results on a prototype incorporating the proposed SVD technique show that stable and reliable SpO2 measurement is achieved even when PPGs are distorted by motion artifacts, thus establishing the efficacy of the proposed method.
83 citations
"Contact-less, Multi-Spectral Imagin..." refers background in this paper
...Research has also been carried out to desensitize a PPG to patient-dependent parameters [2, 3]....
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24 Apr 2006
TL;DR: The design and development of a virtual instrument for the measurement of haemodynamic parameters namely, pulse rate and oxygen saturation in arterial blood based on the popular photoplethysmographic (PPG) principle is presented.
Abstract: This paper presents the design and development of a virtual instrument for the measurement of haemo-dynamic parameters namely, pulse rate and oxygen saturation in arterial blood based on the popular photoplethysmographic (PPG) principle. A clip-on sensor, housing red and infrared (IR) light emitting diodes and suitable photo detectors is developed. The sensor is interfaced to a PC utilizing the audio channel of the sound card, thus dispensing with expensive analog to digital converter hardware. Since the frequency response of the audio channel is not suitable for the PPG waveforms of red and IR, FM modulation and demodulation are employed. An empirical relationship is developed for the computation of the oxygen saturation in arterial blood using the red and IR PPG data and the well-known and well-established extinction coefficients of haemoglobin with and without oxygen. Data acquisition and processing are accomplished under LabVIEW virtual environment.
27 citations
"Contact-less, Multi-Spectral Imagin..." refers background in this paper
...Recent advances in PPG technology have led to the development of a Virtual Instrument based Pulse Oximeter [1] and reliable and robust algorithms for artifact reduction....
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16 Oct 2002
TL;DR: It is shown that reflectance measurements can be used to determine the amount of blood O/sub 2/ saturation of a wound, and an algorithm designed to calculate the blood oxygen saturation from narrow band reflectance images at 760 and 800 nm was used.
Abstract: Reflectance spectroscopy is a common technique used to analyze blood oxygen saturation in biological tissues. This study describes a non-invasive method for mapping blood oxygen saturation in wounds using reflectance measurements obtained from a hyperspectral imaging system. The maps illustrate changes in blood oxygen saturation with high spatial resolution. This allows observation into local blood oxygen supplies of tissue as opposed to common point measurement techniques such as pulse oximetry and optical fiber probing. To demonstrate this, an algorithm designed to calculate the blood oxygen saturation from narrow band reflectance images at 760 and 800 nm was used. The algorithm incorporates the contributions of absorption by oxy-(HbO/sub 2/) and deoxy-hemoglobin (Hb) at the oxygen (O/sub 2/) sensitive and O/sub 2/ insensitive wavelength. Results of the algorithms performance are presented to demonstrate that reflectance measurements can be used to determine the amount of blood O/sub 2/ saturation of a wound.
25 citations