Doppler Spectrum Classification with CNNs via Heatmap Location Encoding and a Multi-head Output Layer
This work addresses the need for full automation in echocardiographic diagnostics, enabling a fully automatic pipeline from acquisition to Doppler spectrum measurements, though it is incremental as it builds on existing CNN methods.
The authors tackled the problem of automating the classification of cardiac Doppler spectra into measurement classes, which currently requires manual selection, by developing a convolutional neural network that achieved 96% accuracy on a test set from a separate clinical site.
Spectral Doppler measurements are an important part of the standard echocardiographic examination. These measurements give important insight into myocardial motion and blood flow providing clinicians with parameters for diagnostic decision making. Many of these measurements can currently be performed automatically with high accuracy, increasing the efficiency of the diagnostic pipeline. However, full automation is not yet available because the user must manually select which measurement should be performed on each image. In this work we develop a convolutional neural network (CNN) to automatically classify cardiac Doppler spectra into measurement classes. We show how the multi-modal information in each spectral Doppler recording can be combined using a meta parameter post-processing mapping scheme and heatmaps to encode coordinate locations. Additionally, we experiment with several state-of-the-art network architectures to examine the tradeoff between accuracy and memory usage for resource-constrained environments. Finally, we propose a confidence metric using the values in the last fully connected layer of the network. We analyze example images that fall outside of our proposed classes to show our confidence metric can prevent many misclassifications. Our algorithm achieves 96% accuracy on a test set drawn from a separate clinical site, indicating that the proposed method is suitable for clinical adoption and enabling a fully automatic pipeline from acquisition to Doppler spectrum measurements.