Adaptive Spectral Doppler Estimation Based on the Modified Amplitude Spectrum Capon

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Biomedical Engineering

Background:

• Conventional ultrasound systems face limitations in frequency and temporal resolution, impacting spectrogram quality and fast blood flow tracking.
• High blood velocities and short Doppler signal observation windows (OWs) in adaptive methods exacerbate spectral broadening, reducing imaging accuracy.

Purpose of the Study:

• To develop and validate an adaptive ultrasound technique that reduces spectral broadening over time.
• To improve spectral resolution and contrast, particularly for high-velocity blood flow imaging using shorter observation times.

Main Methods:

• Proposed an adaptive technique combining covariance matrix Eigen space with the amplitude spectrum Capon (ASC) algorithm.
• Utilized a coherence-based post-filter to further enhance spectral resolution and accuracy.
• Validated the method using simulations (femoral artery, parabolic flow, carotid bifurcation) and in vivo hepatic vein data.

Main Results:

• The proposed method significantly improved frequency resolution and contrast, even with extremely small observation windows (N=[2, 4]).
• Achieved substantial performance gains compared to existing adaptive algorithms (Capon, APES, projection-based Capon, projection-based APES) in both simulated and in vivo data.
• Demonstrated improvements in frequency resolution (up to 74%) and contrast (up to 96.5 dB) using in vivo data with an OW of N=4.

Conclusions:

• The novel adaptive ultrasound technique effectively enhances spectral resolution and contrast.
• This method offers a significant advancement for accurate blood flow imaging, especially in challenging scenarios with high velocities and limited observation times.