Patents by Inventor Lionel Tarassenko

Lionel Tarassenko has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 10448846
    Abstract: Haemodynamic parameters such as the amplitude and phase of a pulse wave passing through a region of interest can be obtained from a video image of the exposed skin of a patient by processing of the reflectance photoplethysmographic signal using signal averaging. The region of interest is defined and a reflectance photoplethysmographic signal obtained by finding the mean pixel intensity across the region of interest for each video frame. Signal averaging is performed on the resulting pulsatile waveform by detecting peaks in the waveform, selecting those parts of the waveform which lie within a window centered on the peaks, and summing the selected parts of the waveform to find an average pulse waveform. The region of interest is then divided into sub-regions and an average pulse waveform for the video sequence is found for each of the sub-regions in the same way.
    Type: Grant
    Filed: December 14, 2015
    Date of Patent: October 22, 2019
    Assignee: OXFORD UNIVERSITY INNOVATION LIMITED
    Inventors: Lionel Tarassenko, Jonathan Daly
  • Publication number: 20190311809
    Abstract: A patient status monitor for providing an estimate of the risk of an adverse health event such as death or intensive care readmission based on a first risk estimate using patient data collected over a first time period, such as a stay in an intensive care unit, and a second risk estimate based on current vitals signs measurements. The first and second risk estimates are based on different models, the first being a static logistic regression on data selected from electronic patient records, and the second being a novelty detection algorithm based on a a training data set of vital signs measurements representing normality. The two risk estimates are combined in a weighted combination, with the first risk estimate having a weight which decreases with time from the end of the first time period.
    Type: Application
    Filed: October 31, 2017
    Publication date: October 10, 2019
    Inventors: Duncan YOUNG, Peter WATKINSON, Lionel TARASSENKO
  • Publication number: 20190069808
    Abstract: Methods, devices and systems for determining the frequency of a periodic physiological process of a subject, particularly respiration rate or heart rate, are disclosed. In one arrangement plural time windows of physiological data are obtained. Reference features corresponding to modulation modes are identified. Modulations of the reference features are extracted. Quality parameters are obtained by processing the extracted modulations. The quality parameters represent how strongly the extracted modulation exhibits a waveform of the periodic physiological process. The extracted modulations are processed to calculate the frequency of the periodic physiological process of the subject.
    Type: Application
    Filed: November 2, 2018
    Publication date: March 7, 2019
    Inventors: David Andrew CLIFTON, Drew BIRRENKOTT, Lionel TARASSENKO, Marco PIMENTEL
  • Publication number: 20180153455
    Abstract: A method of monitoring changes in oxygen saturation of a subject by analysing a three colour channel video image of the exposed skin of the subject. Within each colour channel a normalised signal obtained by dividing the intensity signal by its mean value, and the normalised signals are averaged across plural regions of interest within the exposed skin area image of the subject. Regions of interest are selected on the basis of the signal-to-noise ratios for the heart rate and breathing rate components. A single representative waveform for each colour channel is obtained by signal averaging and the ratio of the amplitudes of the representative waveforms from two different colour channels, e.g. blue and red, is taken. The changes in the ratio of amplitudes is output as a measure of changes in blood oxygen saturation.
    Type: Application
    Filed: June 2, 2016
    Publication date: June 7, 2018
    Applicant: OXFORD UNIVERSITY INNOVATION LIMITED
    Inventors: Alessandro GUAZZI, Mauricio Villarroel MONTOYA, Lionel TARASSENKO
  • Patent number: 9874472
    Abstract: Vibration amplitudes are recorded as a function of rotation speed and of frequency and the data is analyzed to estimate a noise floor amplitude threshold for each of a plurality of different speed and frequency sub-ranges. On the basis of training data known to be normal speed-frequency areas which contain significant spectral content in normal operation are deemed “known significant spectral content”, so that during monitoring of new data points which correspond to significant vibration energy at speeds and frequencies different from the known significant spectral content can be deemed “novel significant spectral content” and form the basis for an alert. The estimation of the noise floor is based on a probabilistic analysis of the data in each speed-frequency area and from this analysis an extreme value distribution expressing the probability that any given sample is noise is obtained.
    Type: Grant
    Filed: February 17, 2010
    Date of Patent: January 23, 2018
    Assignee: ROLLS-ROYCE PLC
    Inventors: Lionel Tarassenko, David A Clifton, Dennis King, Steven P King, David J Ault
  • Publication number: 20170354334
    Abstract: Haemodynamic parameters such as the amplitude and phase of a pulse wave passing through a region of interest can be obtained from a video image of the exposed skin of a patient by processing of the reflectance photoplethysmographic signal using signal averaging. The region of interest is defined and a reflectance photoplethysmographic signal obtained by finding the mean pixel intensity across the region of interest for each video frame. Signal averaging is performed on the resulting pulsatile waveform by detecting peaks in the waveform, selecting those parts of the waveform which lie within a window centred on the peaks, and summing the selected parts of the waveform to find an average pulse waveform. The region of interest is then divided into sub-regions and an average pulse waveform for the video sequence is found for each of the sub-regions in the same way.
    Type: Application
    Filed: December 14, 2015
    Publication date: December 14, 2017
    Applicant: OXFORD UNIVERSITY INNOVATION LIMITED
    Inventors: Lionel TARASSENKO, Jonathan DALY
  • Publication number: 20170332978
    Abstract: A method and apparatus for estimating the frequency of a dominant periodic component in an input signal by modelling the input signal using auto-regressive models of several different orders to generate candidate frequencies for the periodic component, generating synthetic sinusoidal signals of each of the candidate frequencies, and calculating the cross-correlation of the synthetic signals with the original signal. The frequency of whichever of the synthetic signals has the highest cross-correlation with the original signal is taken as the estimate of the frequency for the dominant periodic component of the input signal. The method may be applied to any noisy signal which has a suspected periodic component, for example physiological signals such as photoplethysmogram signals, and in the estimation of heart rate and breathing rate from such physiological signals.
    Type: Application
    Filed: December 8, 2015
    Publication date: November 23, 2017
    Applicant: OXFORD UNIVERSITY INNOVATION LIMITED
    Inventors: Alessandro GUAZZI, Syed Ahmar SHAH, Lionel TARASSENKO
  • Patent number: 9659229
    Abstract: An image of a human, animal or machine subject, is analysed to detect regions which include strong periodic intensity variations, such as a photoplethysmogram (PPG) signal in a human or animal, or some periodic vibration in a machine. The image is divided into plural regions of fixed order is fitted to a representative intensity signal for that region. The poles of the fitted autoregressive model are thresholded by magnitude to select only the pole or poles with a magnitude greater than the threshold. The pole magnitude therefore acts as a signal quality index. The dominant pole is representative of the strongest periodic information and the frequency of that spectral component can be derived from the phase angle of the pole. The image may be redisplayed with image attributes, e.g. color-coding, according to the pole magnitude in each region of interest and/or the dominant pole phase angle in each region of interest. In the case of a PPG image signal this can give maps of heart rate and breathing rate.
    Type: Grant
    Filed: January 28, 2014
    Date of Patent: May 23, 2017
    Assignee: ISIS INNOVATION LIMITED
    Inventors: David Andrew Clifton, Mauricio Christian Villarroel Montoya, Lionel Tarassenko
  • Patent number: 9615749
    Abstract: A method of remote monitoring of vital signs by detecting the PPG signal in an image of a subject taken by a video camera such as a webcam. The PPG signal is identified by auto-regressive analysis of ambient light reflected from a region of interest on the subject's skin. Frequency components of the ambient light and aliasing artefacts resulting from the frame rate of the video camera are cancelled by auto-regressive analysis of ambient light reflected from a region of interest not on the subject's skin, e.g. in the background. This reveals the spectral content of the ambient light allowing identification of the subject's PPG signal. Heart rate, oxygen saturation and breathing rate are obtained from the PPG signal. The values can be combined into a wellness index based on a statistical analysis of the values.
    Type: Grant
    Filed: August 16, 2012
    Date of Patent: April 11, 2017
    Assignee: ISIS INNOVATION LIMITED
    Inventors: David Andrew Clifton, Mauricio Christian Villarroel Montoya, Lionel Tarassenko
  • Publication number: 20160171170
    Abstract: A method of obtaining information about the rate of a periodic physiological process from a time series of measurements obtained from a patient, comprising: obtaining the time series of measurements; fitting a model defining a probability distribution over functions to the time series of measurements, wherein the model is defined by a mean function and a periodic covariance function; and outputting the result of the fitting as information about the rate of the periodic physiological process.
    Type: Application
    Filed: June 25, 2014
    Publication date: June 16, 2016
    Applicant: ISIS INNOVATION LIMITED
    Inventors: David Andrew CLIFTON, Marco PIMENTEL, Lionel TARASSENKO
  • Publication number: 20150379370
    Abstract: An image of a human, animal or machine subject, is analysed to detect regions which include strong periodic intensity variations, such as a photoplethysmogram (PPG) signal in a human or animal, or some periodic vibration in a machine. The image is divided into plural regions of fixed order is fitted to a representative intensity signal for that region. The poles of the fitted autoregressive model are thresholded by magnitude to select only the pole or poles with a magnitude greater than the threshold. The pole magnitude therefore acts as a signal quality index. The dominant pole is representative of the strongest periodic information and the frequency of that spectral component can be derived from the phase angle of the pole. The image may be redisplayed with image attributes, e.g. colour-coding, according to the pole magnitude in each region of interest and/or the dominant pole phase angle in each region of interest. In the case of a PPG image signal this can give maps of heart rate and breathing rate.
    Type: Application
    Filed: January 28, 2014
    Publication date: December 31, 2015
    Applicant: ISIS INNOVATION LIMITED
    Inventors: David Andrew CLIFTON, Mauricio Christian Villarroel MONTOYA, Lionel TARASSENKO
  • Publication number: 20150227837
    Abstract: A method of monitoring a system such as a machine, industrial system, or human or animal patient, to classify the system as normal or abnormal, in which a time-series of measurements of the system are regarded as a function to be compared to a model of normality for such functions. The model of normality can be constructed as a Gaussian Process and test functions compared to the model to derive the probability that they are drawn from the model of normality. A probability distribution for the expected extrema of sets of functions drawn from the model can also be derived and the probability of any extremum of a plurality of test functions being an extremum of a set derived from the model of normality can be obtained. The system can be classified as normal or abnormal based on the extreme probability distribution. Test functions with fewer data points can be compared to the model of normality by marginalisation with respect to the missing data points.
    Type: Application
    Filed: August 22, 2013
    Publication date: August 13, 2015
    Applicant: ISIS INNOVATION LIMITED
    Inventors: David Andrew Clifton, Lionel Tarassenko, Samuel Hugueny
  • Patent number: 8949072
    Abstract: A method of obtaining a consistent evaluation of the state of the system which has been monitored by measurement of multiple parameters of that system. The multiple parameters are used to calculate a single dimensional value based on the distance between the current state and normal states of the system using a Parzen Windows probability function. Consistent single dimensional values regardless of the dimensionality of the original data set can be obtained by finding a relationship between the single dimensional value and the probability of status of the system. Different relationships are obtained for different dimensionalities of data sets. Sensor malfunction can also be detected by testing the probability of the state implied by measuring all of the available parameters against the probability of the state implied by ignoring different individual ones of the parameters. A significant disparity in the two probabilities indicate possible sensor malfunction.
    Type: Grant
    Filed: October 9, 2009
    Date of Patent: February 3, 2015
    Assignee: Oxford Biosignals Limited
    Inventors: Lionel Tarassenko, Alistair Hann
  • Publication number: 20140303454
    Abstract: A method of remote monitoring of vital signs by detecting the PPG signal in an image of a subject taken by a video camera such as a webcam. The PPG signal is identified by auto-regressive analysis of ambient light reflected from a region of interest on the subject's skin. Frequency components of the ambient light and aliasing artefacts resulting from the frame rate of the video camera are cancelled by auto-regressive analysis of ambient light reflected from a region of interest not on the subject's skin, e.g. in the background. This reveals the spectral content of the ambient light allowing identification of the subject's PPG signal. Heart rate, oxygen saturation and breathing rate are obtained from the PPG signal. The values can be combined into a wellness index based on a statistical analysis of the values.
    Type: Application
    Filed: August 16, 2012
    Publication date: October 9, 2014
    Applicant: ISIS INNOVATION LIMITED
    Inventors: David Andrew Clifton, Mauricio Christian Villarroel Montoya, Lionel Tarassenko
  • Publication number: 20140149325
    Abstract: A method of system monitoring or, more particularly, novelty detection, based on extreme value theory in particular a points-over-threshold POT method which is applicable to multimodal multivariate data. Multimodal multivariate data points collected by continuously monitoring a system are transformed into probability space by obtaining their probability density function (pdf) values from a statistical model of normality, such as a pdf fitted to a training data set of normal data. Extremal data is defined as that whose pdf value is below a predetermined threshold and a new analytic function, in particular the Generalised Pareto Distribution (GPD) is fitted to that extremal data only. The fitted GPD can be compared to a GPD fitted to the extremal datapoints of the training data set of normal data to determine if the monitored system is in a normal state.
    Type: Application
    Filed: May 16, 2012
    Publication date: May 29, 2014
    Applicant: ISIS INNOVATION LIMITED
    Inventors: David Andrew Clifton, Samuel Yung Hugueny, Lionel Tarassenko
  • Patent number: 8332017
    Abstract: A method of analysing biomedical signals, for example electrocardiograms, by using a Hidden Markov Model for subsections of the signal. In the case of an electrocardiogram two Hidden Markov Models are used to detect respectively the start and end of the QT interval. The relationship between the QT interval and heart rate can be computed and a contemporaneous value for the slope of this relationship can be obtained by calculating the QT/RR relationship for all of the beats in a sliding time window based on the current beat. Portions of electrocardiograms taken on different days can efficiently and accurately be compared by selecting time windows of the ECGs at the same time of day, and looking for similar beats in those time windows.
    Type: Grant
    Filed: November 30, 2007
    Date of Patent: December 11, 2012
    Assignee: OBS Medical Limited
    Inventors: Lionel Tarassenko, Alan Patterson, Iain Guy Strachan
  • Patent number: 8290575
    Abstract: A way of quantifying the shape of an ECG waveform is disclosed by detecting the JT segment using two Hidden Markov Models and calculating the analytic signal of the JT segment. Parameters calculated from the analytic signal are used as shape descriptors for the JT segment. The shape descriptors may be displayed in a dimensionality-reduced mapping. Templates representing characteristic shapes can be produced by finding cluster centers in the shape descriptor space, and the novelty of new waveforms can be quantified by comparing the position in shape descriptor space of new shape descriptors to a predefined normal training set or to previously encountered waveforms. Novel shape descriptors can be used to retrieve the corresponding waveforms, and templates of such novel shapes can be created by averaging such waveforms, using dynamic time warping to allow for variations in heart rate.
    Type: Grant
    Filed: November 30, 2007
    Date of Patent: October 16, 2012
    Assignee: OBS Medical Limited
    Inventors: Lionel Tarassenko, Alan Patterson, Iain Guy Strachan
  • Publication number: 20120035885
    Abstract: Vibration amplitudes are recorded as a function of rotation speed and of frequency and the data is analyzed to estimate a noise floor amplitude threshold for each of a plurality of different speed and frequency sub-ranges. On the basis of training data known to be normal speed-frequency areas which contain significant spectral content in normal operation are deemed “known significant spectral content”, so that during monitoring of new data points which correspond to significant vibration energy at speeds and frequencies different from the known significant spectral content can be deemed “novel significant spectral content” and form the basis for an alert. The estimation of the noise floor is based on a probabilistic analysis of the data in each speed-frequency area and from this analysis an extreme value distribution expressing the probability that any given sample is noise is obtained.
    Type: Application
    Filed: February 17, 2010
    Publication date: February 9, 2012
    Applicant: Optimized Systems and Solutions Limited
    Inventors: Lionel Tarassenko, David A. Clifton, Dennis King, Steven P. King, David J. Ault
  • Publication number: 20110265026
    Abstract: A method of obtaining a consistent evaluation of the state of the system which has been monitored by measurement of multiple parameters of that system. The multiple parameters are used to calculate a single dimensional value based on the distance between the current state and normal states of the system using a Parzen Windows probability function. Consistent single dimensional values regardless of the dimensionality of the original data set can be obtained by finding a relationship between the single dimensional value and the probability of status of the system. Different relationships are obtained for different dimensionalities of data sets. Sensor malfunction can also be detected by testing the probability of the state implied by measuring all of the available parameters against the probability of the state implied by ignoring different individual ones of the parameters. A significant disparity in the two probabilities indicate possible sensor malfunction.
    Type: Application
    Filed: October 9, 2009
    Publication date: October 27, 2011
    Inventors: Lionel Tarassenko, Alistair Hann
  • Patent number: 7941209
    Abstract: Improvement in the reliability of segmentation of a signal, such as an ECG signal, is achieved through the use of duration constraints. The signal is analysed using a hidden Markov model. The duration constraints specify minimum allowed durations for specific states of the model. The duration constraints can be incorporated either in the model itself or in a Viterbi algorithm used to compute the most probable state sequence given a conventional model. The derivation of a confidence measure from the model can be used to assess the quality and robustness of the segmentation and to identify any signals for which the segmentation is unreliable, for example due to the presence of noise or abnormality in the signal.
    Type: Grant
    Filed: May 6, 2005
    Date of Patent: May 10, 2011
    Assignee: OBS Medical Limited
    Inventors: Nicholas Hughes, Lionel Tarassenko, Stephen Roberts