Non-invasive blood flow measurements utilizing autoregressive analysis

Abstract

A system for non-invasively determining the amount of blood flow within an internal patient blood vessel by performing an autoregressive analysis of Doppler shifted acoustical signals resulting from the reflection of ultrasonic signals due to blood cell movement by averaging the reflection coefficients and residual energy levels resulting from the autoregressive analysis over a number of cardiac cycles. The reflection coefficients result from a linear predictive code analysis, and the term 'reflection coefficients' is not used in the customary manner as defined for ultrasonic flow analysis of blood as defining a level of reflected acoustic energy. Each cardiac cycle is determined by an analysis of the patient's electrocardiogram signals, and the resulting cardiac cycles are divided into a predefined number of time segments or channels. An autoregressive analysis is then performed on each individual channel to determine the reflection coefficients and the residual energy level for each channel. The reflection coefficients and residual energy level for each particular channel are then averaged over all the cardiac cycles to obtain an averaged reflection coefficient and averaged residual energy level for each combined channel. The power spectrum for each combined channel is then calculated from the averaged reflection coefficients and averaged residual energy level and displayed on a channel-by-channel basis utilizing different colors to represent the different power levels. The utilization of different colors greatly enhances the usability of the display by medical personnel making diagnostic decisions regarding the amount of blood flow.