Analysis of Doppler Embolic Signals

Abstract

A broad view on the analysis of Doppler embolic signals is presented, uniting physics, engineering and computing, and clinical aspects. The overview of the field discusses the physiological significance of emboli and Doppler ultrasound with particular attention given to Transcranial Doppler; an outline of high-performance computing is presented, disambiguating the terminology and concepts used thereafter. The presentation of the major diagnostic approaches to Doppler embolic signals focuses on the most significant methods and techniques used to detect and classify embolic events including the clinical relevancy. Coverage of estimators such as time-frequency, time-scale, and displacement-frequency is included. The discussion of current approaches targets areas of identified need for improvement. A brief historical perspective of high-performance computing of Doppler blood flow signals and particularly Doppler embolic signals is accompanied by the reasoning behind the technological trends and approaches. The final remarks include, as a conclusion, a summary of the contribution and as future trends, some pathways hinting to where new developments might be expected.

Displacement-Frequency Doppler Blood Flow Estimation

“…Finally some concluding studies reported the Short Time Modified Covariance and the remarks are drawn highlighting possible application of the discrete Choi-Williams distribution as good alternatives to the method. conventional method, when applied to arterial blood flow Doppler signals [1][2][3].II TIME-FREQUENCY METHODOLOGY Recently, it was noted that with time-frequency representation it was difficult to observe important events Each bin of a time signal contains information about all the occurring during the systolic phase of the cardiac cycle blood cells in the sample volume at a given time. The time (vortex n systol1c drop or embol1c events durg systole) This iS because the highest velocities of blood occur during observed anywhere in the signal.…”

“…Finally some concluding studies reported the Short Time Modified Covariance and the remarks are drawn highlighting possible application of the discrete Choi-Williams distribution as good alternatives to the method. conventional method, when applied to arterial blood flow Doppler signals [1][2][3].…”

“…the ultrasound beam and the direction of the moving target, c v(s -= 1 the velocity of sound in the medium, andj(s) is the maximum frequency at time n(s), which can be extracted using the where M is the number of relevant time instants in the time Modified Geometric Method [2], assuming that the maximum domain signal, svl is the sample volume length along the axis velocity is relatively static between relevant bins. It should be of the vessel and v(s) the highest component of velocity along noted that the computational load required by the Modified the vessel at time n(s).…”