KLT-based quality controlled compression of a single lead egg
First Claim
1. A method of encoding a plurality of sampled ECG records, each record representing a heartbeat, said method comprising the steps of:
- (a) aligning the records about their R-peaks;
(b) sizing the records to have the same number of samples and forming a sample set of the sized records; and
(c) performing a Karhunen-Loeve Transform (KLT) on the sample set, thereby generating a set of eigenvalues and associated eigenvectors for the sample set, and a set of KLT coefficients for each record.
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Abstract
A compression algorithm for the compression of ECG recordings uses the Karhunen-Loeve Transform (KLT) to transform a set of N sampled ECG beats from a matrix of N×M samples into a new form, from which a selected subset can be retained for storage, transmission, or analysis. In order to reduce computation time and storage space, a multirate downsampling operation may be applied, which retains the appropriate spectral information in each block. The downsampled beats are then padded to make them of uniform size, and a Karhunen-Loeve Transform is applied to the sample set. Coefficients from the Karhunen-Loeve Transform of the sample set are retained for reconstruction according to one of two criteria. The average variance of the reconstructed sample set may be controlled, or different numbers of coefficients may be retained for each beat. The KLT compressed data may be reconstituted by reverse KLT transforming the data.
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Citations
29 Claims
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1. A method of encoding a plurality of sampled ECG records, each record representing a heartbeat, said method comprising the steps of:
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(a) aligning the records about their R-peaks; (b) sizing the records to have the same number of samples and forming a sample set of the sized records; and (c) performing a Karhunen-Loeve Transform (KLT) on the sample set, thereby generating a set of eigenvalues and associated eigenvectors for the sample set, and a set of KLT coefficients for each record. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. Apparatus for encoding a plurality of sampled ECG records, each record representing a heartbeat, said apparatus comprising:
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means for centering the records about their R-peaks; means for sizing the records to have the same number of samples and forming a sample set of the sized records; and means for performing a Karhunen-Loeve Transform (KLT) on the sample set, thereby generating a set of eigenvalues and eigenvectors for the sample set, and a set of KLT coefficients for each record. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A method of detecting irregular heartbeats from a string of sampled heartbeat records comprising the steps of:
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(a) centering the records about their R-peaks; (b) sizing the records to have the same number of samples and forming a sample set of the sized records; (c) performing a Karhunen-Loeve Transform (KLT) on the sample set, thereby generating a set of eigenvalues and associated eigenvectors for the sample set, and a set of KLT coefficients for each record; (d) ordering the eigenvalues and their associated eigenvectors in decreasing order of eigenvalue size; (e) retaining an ordered subset of the most significant KLT coefficients for each record and an ordered subset of the eigenvectors associated with largest eigenvalues for the sample set wherein a variable number of KLT coefficients for each record is retained, according to a criterion which minimizes reconstruction error; and (f) flagging each record for which more than a predetermined number of coefficients are retained, as pertaining to potentially irregular heartbeats. - View Dependent Claims (25, 26, 27, 28, 29)
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Specification