Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring
One dimensional Doppler Ultrasound (DUS) is a low cost method for fetal auscultation. However, accuracy of any metrics derived from the DUS signals depends on their quality, which relies heavily on operator skills. In low resource settings, where skill levels are sparse, it is important for the devi...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2017-07-01
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| Series: | Frontiers in Physiology |
| Subjects: | |
| Online Access: | http://journal.frontiersin.org/article/10.3389/fphys.2017.00511/full |
| _version_ | 1819126689855176704 |
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| author | Camilo E. Valderrama Faezeh Marzbanrad Lisa Stroux Gari D. Clifford Gari D. Clifford |
| author_facet | Camilo E. Valderrama Faezeh Marzbanrad Lisa Stroux Gari D. Clifford Gari D. Clifford |
| author_sort | Camilo E. Valderrama |
| collection | DOAJ |
| description | One dimensional Doppler Ultrasound (DUS) is a low cost method for fetal auscultation. However, accuracy of any metrics derived from the DUS signals depends on their quality, which relies heavily on operator skills. In low resource settings, where skill levels are sparse, it is important for the device to provide real time signal quality feedback to allow the re-recording of data. Retrospectively, signal quality assessment can help remove low quality recordings when processing large amounts of data. To this end, we proposed a novel template-based method, to assess DUS signal quality. Data used in this study were collected from 17 pregnant women using a low-cost transducer connected to a smart phone. Recordings were split into 1990 segments of 3.75 s duration, and hand labeled for quality by three independent annotators. The proposed template-based method uses Empirical Mode Decomposition (EMD) to allow detection of the fetal heart beats and segmentation into short, time-aligned temporal windows. Templates were derived for each 15 s window of the recordings. The DUS signal quality index (SQI) was calculated by correlating the segments in each window with the corresponding running template using four different pre-processing steps: (i) no additional preprocessing, (ii) linear resampling of each beat, (iii) dynamic time warping (DTW) of each beat and (iv) weighted DTW of each beat. The template-based SQIs were combined with additional features based on sample entropy and power spectral density. To assess the performance of the method, the dataset was split into training and test subsets. The training set was used to obtain the best combination of features for predicting the DUS quality using cross validation, and the test set was used to estimate the classification accuracy using bootstrap resampling. A median out of sample classification accuracy on the test set of 85.8% was found using three features; template-based SQI, sample entropy and the relative power in the 160 to 660 Hz range. The results suggest that the new automated method can reliably assess the DUS quality, thereby helping users to consistently record DUS signals with acceptable quality for fetal monitoring. |
| first_indexed | 2024-12-22T08:00:02Z |
| format | Article |
| id | doaj.art-5ddd3c072e5a4872a4e1c26463a5176a |
| institution | Directory Open Access Journal |
| issn | 1664-042X |
| language | English |
| last_indexed | 2024-12-22T08:00:02Z |
| publishDate | 2017-07-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Physiology |
| spelling | doaj.art-5ddd3c072e5a4872a4e1c26463a5176a2022-12-21T18:33:16ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2017-07-01810.3389/fphys.2017.00511275108Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal MonitoringCamilo E. Valderrama0Faezeh Marzbanrad1Lisa Stroux2Gari D. Clifford3Gari D. Clifford4Department of Mathematics and Computer Science, Emory UniversityAtlanta, GA, United StatesDepartment of Electrical and Computer Systems Engineering, Monash UniversityMelbourne, VIC, AustraliaDepartment of Engineering Science, Institute of Biomedical Engineering, University of OxfordOxford, United KingdomDepartment of Biomedical Informatics, Emory UniversityAtlanta, GA, United StatesDepartment of Biomedical Engineering, Georgia Institute of TechnologyAtlanta, GA, United StatesOne dimensional Doppler Ultrasound (DUS) is a low cost method for fetal auscultation. However, accuracy of any metrics derived from the DUS signals depends on their quality, which relies heavily on operator skills. In low resource settings, where skill levels are sparse, it is important for the device to provide real time signal quality feedback to allow the re-recording of data. Retrospectively, signal quality assessment can help remove low quality recordings when processing large amounts of data. To this end, we proposed a novel template-based method, to assess DUS signal quality. Data used in this study were collected from 17 pregnant women using a low-cost transducer connected to a smart phone. Recordings were split into 1990 segments of 3.75 s duration, and hand labeled for quality by three independent annotators. The proposed template-based method uses Empirical Mode Decomposition (EMD) to allow detection of the fetal heart beats and segmentation into short, time-aligned temporal windows. Templates were derived for each 15 s window of the recordings. The DUS signal quality index (SQI) was calculated by correlating the segments in each window with the corresponding running template using four different pre-processing steps: (i) no additional preprocessing, (ii) linear resampling of each beat, (iii) dynamic time warping (DTW) of each beat and (iv) weighted DTW of each beat. The template-based SQIs were combined with additional features based on sample entropy and power spectral density. To assess the performance of the method, the dataset was split into training and test subsets. The training set was used to obtain the best combination of features for predicting the DUS quality using cross validation, and the test set was used to estimate the classification accuracy using bootstrap resampling. A median out of sample classification accuracy on the test set of 85.8% was found using three features; template-based SQI, sample entropy and the relative power in the 160 to 660 Hz range. The results suggest that the new automated method can reliably assess the DUS quality, thereby helping users to consistently record DUS signals with acceptable quality for fetal monitoring.http://journal.frontiersin.org/article/10.3389/fphys.2017.00511/fulldoppler ultrasoundempirical mode decompositionfetal monitoringdynamic time warpingsample entropysignal quality |
| spellingShingle | Camilo E. Valderrama Faezeh Marzbanrad Lisa Stroux Gari D. Clifford Gari D. Clifford Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring Frontiers in Physiology doppler ultrasound empirical mode decomposition fetal monitoring dynamic time warping sample entropy signal quality |
| title | Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring |
| title_full | Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring |
| title_fullStr | Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring |
| title_full_unstemmed | Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring |
| title_short | Template-based Quality Assessment of the Doppler Ultrasound Signal for Fetal Monitoring |
| title_sort | template based quality assessment of the doppler ultrasound signal for fetal monitoring |
| topic | doppler ultrasound empirical mode decomposition fetal monitoring dynamic time warping sample entropy signal quality |
| url | http://journal.frontiersin.org/article/10.3389/fphys.2017.00511/full |
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