Adaptive Maximal Blood Flow Velocity Estimation From Transcranial Doppler Echos

• Published in: IEEE journal of translational engineering in health and medicine Vol. 8; pp. 1 - 11
• Main Authors: Wadehn, Federico, Heldt, Thomas
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.01.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Arteries; Blood; Blood flow; Blood vessels; Carotid arteries; Doppler effect; envelope tracing; Estimation; Feedback loops; Flow velocity; Image edge detection; Intracranial pressure; intracranial pressure estimation; Iterative closest point algorithm; maximal blood flow velocity; Occlusion; Quality; Quality assessment; Segmentation; Signal quality; signal quality assessment; Signal to noise ratio; Spectrogram; Spectrograms; Transcranial Doppler ultrasound; Ultrasonic imaging; Waveforms; Transcranial Doppler ultrasound; intracranial pressure estimation; envelope tracing; signal quality assessment; maximal blood flow velocity
• ISSN: 2168-2372; 2168-2372
• DOI: 10.1109/JTEHM.2020.3011562

Objective: Novel applications of transcranial Doppler (TCD) ultrasonography, such as the assessment of cerebral vessel narrowing/occlusion or the non-invasive estimation of intracranial pressure (ICP), require high-quality maximal flow velocity waveforms. However, due to the low signal-to-noise ratio of TCD spectrograms, measuring the maximal flow velocity is challenging. In this work, we propose a calibration-free algorithm for estimating maximal flow velocities from TCD spectrograms and present a pertaining beat-by-beat signal quality index. Methods: Our algorithm performs multiple binary segmentations of the TCD spectrogram and then extracts the pertaining envelopes (maximal flow velocity waveforms) via an edge-following step that incorporates physiological constraints. The candidate maximal flow velocity waveform with the highest signal quality index is finally selected. Results: We evaluated the algorithm on 32 TCD recordings from the middle cerebral and internal carotid arteries in 6 healthy and 12 neurocritical care patients. Compared to manual spectrogram tracings, we obtained a relative error of −1.5%, when considering the whole waveform, and a relative error of −3.3% for the peak systolic velocity. Conclusion: The feedback loop between the signal quality assessment and the binary segmentation yields a robust algorithm for maximal flow velocity estimation. Clinical Impact: The algorithm has already been used in our ICP estimation pipeline. By making the code and the data publicly available, we hope that the algorithm will be a useful building block for the development of novel TCD applications that require high-quality flow velocity waveforms.