A robust Doppler spectral envelope detection technique for automated blood flow measurements

Maximum velocity estimation in a Doppler Spectrogram is of clinical interest. Two existing approaches to maximum velocity estimation, the Geometric method (GM) and the Signal Noise Slope Intersection (SNSI) method are combined in the new approach described in this paper. Further, a data adaptive validity check is introduced that makes the proposed technique independent of user defined parameters. The method enables accurate maximum velocity point detection and obtains an automated, robust tracing of the maximum velocity envelope, which can be further used for automated blood flow measurements. In order to verify the robustness of the algorithm, Pulsatility Index measurements were compared with the observations made by a midwife trained in ultrasound. Evaluation of the steadiness of the location of identified maximum frequency point in simulated flow with varying SNR, ranging to a minimum SNR level of 6dB, also aided the verification. This technique is expected to prove useful in ultrasound machines for diagnoses by clinically inexperienced users.