title: Automated signal quality assessment of mobile phone-recorded heart sound signals.
abstract: Mobile phones, due to their audio processing capabilities, have the potential to facilitate the diagnosis of heart disease through automated auscultation. However, such a platform is likely to be used by non-experts, and hence, it is essential that such a device is able to automatically differentiate poor quality from diagnostically useful recordings since non-experts are more likely to make poor-quality recordings. This paper investigates the automated signal quality assessment of heart sound recordings performed using both mobile phone-based and commercial medical-grade electronic stethoscopes. The recordings, each 60 s long, were taken from 151 random adult individuals with varying diagnoses referred to a cardiac clinic and were professionally annotated by five experts. A mean voting procedure was used to compute a final quality label for each recording. Nine signal quality indices were defined and calculated for each recording. A logistic regression model for classifying binary quality was then trained and tested. The inter-rater agreement level for the stethoscope and mobile phone recordings was measured using Conger's kappa for multiclass sets and found to be 0.24 and 0.54, respectively. One-third of all the mobile phone-recorded phonocardiogram (PCG) signals were found to be of sufficient quality for analysis. The classifier was able to distinguish good- and poor-quality mobile phone recordings with 82.2% accuracy, and those made with the electronic stethoscope with an accuracy of 86.5%. We conclude that our classification approach provides a mechanism for substantially improving auscultation recordings by non-experts. This work is the first systematic evaluation of a PCG signal quality classification algorithm (using a separate test dataset) and assessment of the quality of PCG recordings captured by non-experts, using both a medical-grade digital stethoscope and a mobile phone.
authors.affiliation: a Department of Engineering Science , University of Oxford , Oxford , UK.
authors.forename: David B
authors.initials: DB
authors.lastname: Springer
authors.affiliation: a Department of Engineering Science , University of Oxford , Oxford , UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brennan
authors.affiliation: b Department of Medicine , Groote Schuur Hospital , Cape Town , South Africa.|c Department of Medicine , University of Cape Town , Cape Town , South Africa.
authors.forename: Ntobeko
authors.initials: N
authors.lastname: Ntusi
authors.affiliation: b Department of Medicine , Groote Schuur Hospital , Cape Town , South Africa.|c Department of Medicine , University of Cape Town , Cape Town , South Africa.
authors.forename: Hassan Y
authors.initials: HY
authors.lastname: Abdelrahman
authors.affiliation: b Department of Medicine , Groote Schuur Hospital , Cape Town , South Africa.|c Department of Medicine , University of Cape Town , Cape Town , South Africa.
authors.forename: Liesl J
authors.initials: LJ
authors.lastname: Zühlke
authors.affiliation: b Department of Medicine , Groote Schuur Hospital , Cape Town , South Africa.|c Department of Medicine , University of Cape Town , Cape Town , South Africa.
authors.forename: Bongani M
authors.initials: BM
authors.lastname: Mayosi
authors.affiliation: a Department of Engineering Science , University of Oxford , Oxford , UK.
authors.forename: Lionel
authors.initials: L
authors.lastname: Tarassenko
authors.affiliation: d Departments of Biomedical Informatics & Biomedical Engineering , Emory University , Atlanta, GA , USA.
authors.forename: Gari D
authors.initials: GD
authors.lastname: Clifford
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D005260:Female; D006347:Heart Sounds; D006801:Humans; D008297:Male; D008875:Middle Aged; D010701:Phonocardiography; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D000068997:Smartphone; D017216:Telemedicine
keywords: Heart sounds; mobile health; phonocardiography; signal quality