Discriminating between atrial fibrillation and sinus rhythm in physiological signals obtained from video
First Claim
1. A method for determining whether a subject is having an atrial fibrillation event, the method comprising:
- receiving a video of a region of exposed skin of a subject where a videoplethysmographic (VPG) signal can be registered by at least one imaging channel of a video imaging device used to capture that video;
defining a size N of a batch of image frames such that Nmin≦
N≦
Nmax, where Nmin is a minimum size of a batch of image frames and Nmax is a maximum size of a batch of image frames; and
for each batch of image frames of size N;
processing this batch of image frames to isolate pixels associated with said region of exposed skin;
processing said isolated pixels to obtain a time-series signal for this batch;
extracting a VPG signal from said time-series signal;
computing a power spectral density across all frequencies within said VPG signal;
calculating a pulse harmonic strength for this VPG signal;
comparing the pulse harmonic strength (PHS) to a discrimination threshold obtained from a Receiver Operating Characteristic (ROC) curve constructed from health vitals obtained for a group of cardiac patients, said threshold discriminating between low PHS values and high PHS values; and
classifying, as a result of said comparison, that said subject is one of;
in atrial fibrillation, and in sinus rhythm, wherein when PHS is below said threshold said subject is classified as being in atrial fibrillation, and in normal sinus rhythm otherwise.
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Abstract
What is disclosed is a system and method for determining whether a subject is in atrial fibrillation. A video is received of a region of exposed skin of a subject. The video is acquired of a region where a videoplethysmographic (VPG) signal can be registered by at least one imaging channel of a video imaging device. For each batch of image frames, pixels associated with the region of exposed skin are isolated and processed to obtain a time-series signal. A VPG signal is extracted from the time-series signal. The power spectral density (PSD) is computed across all frequencies within the VPG signal. A pulse harmonic strength (PHS) is calculated for this VPG signal. The pulse harmonic strength is compared to a discrimination threshold, defined herein. A determination is made whether the subject in the video is in atrial fibrillation or in normal sinus rhythm.
15 Citations
28 Claims
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1. A method for determining whether a subject is having an atrial fibrillation event, the method comprising:
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receiving a video of a region of exposed skin of a subject where a videoplethysmographic (VPG) signal can be registered by at least one imaging channel of a video imaging device used to capture that video; defining a size N of a batch of image frames such that Nmin≦
N≦
Nmax, where Nmin is a minimum size of a batch of image frames and Nmax is a maximum size of a batch of image frames; andfor each batch of image frames of size N; processing this batch of image frames to isolate pixels associated with said region of exposed skin; processing said isolated pixels to obtain a time-series signal for this batch; extracting a VPG signal from said time-series signal; computing a power spectral density across all frequencies within said VPG signal; calculating a pulse harmonic strength for this VPG signal; comparing the pulse harmonic strength (PHS) to a discrimination threshold obtained from a Receiver Operating Characteristic (ROC) curve constructed from health vitals obtained for a group of cardiac patients, said threshold discriminating between low PHS values and high PHS values; and classifying, as a result of said comparison, that said subject is one of;
in atrial fibrillation, and in sinus rhythm, wherein when PHS is below said threshold said subject is classified as being in atrial fibrillation, and in normal sinus rhythm otherwise. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A system for determining whether a subject is having an atrial fibrillation event, the system comprising:
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a memory and a storage device; and a processor in communication with said memory and storage device, said processor executing machine readable instructions for performing; receiving a video of a region of exposed skin of a subject where a videoplethysmographic (VPG) signal can be registered by at least one imaging channel of a video imaging device used to capture that video; defining a size N of a batch of image frames such that Nmin≦
N≦
Nmax, where Nmin is a minimum size of a batch of image frames and Nmax is a maximum size of a batch of image frames; andfor each batch of image frames of size N; processing this batch of image frames to isolate pixels associated with said region of exposed skin; processing said isolated pixels to obtain a time-series signal for this batch; extracting a VPG signal from said time-series signal; computing a power spectral density across all frequencies within said VPG signal; calculating a pulse harmonic strength for this VPG signal; comparing the pulse harmonic strength (PHS) to a discrimination threshold obtained from a Receiver Operating Characteristic (ROC) curve constructed from health vitals obtained for a group of cardiac patients, said threshold discriminating between low PHS values and high PHS values; and classifying, as a result of said comparison, that said subject is one of;
in atrial fibrillation, and in sinus rhythm, wherein when PHS is below said threshold said subject is classified as being in atrial fibrillation, and in normal sinus rhythm otherwise. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification