Non-invasive blood flow measurements utilizing autoregressive analysis with averaged reflection coefficients
First Claim
1. An autoregressive analysis system for obtaining the average power spectrum of a plurality of signal groups each comprising a plurality of information signals, comprising:
- means for determining the start and end of each of said signal groups;
means responsive to said information signals of each of said groups as determined by said determining means for calculating reflection coefficients for each of said signal groups;
means responsive to said information signals and said reflection coefficients for each of said signal groups for generating a residual energy level for each of said signal groups;
means for averaging said reflection coefficients of said signal groups and said residual energy levels of said signal groups; and
means responsive to said averaged reflection coefficients and said averaged residual energy level for generating the average power spectrum.
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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.
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Citations
17 Claims
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1. An autoregressive analysis system for obtaining the average power spectrum of a plurality of signal groups each comprising a plurality of information signals, comprising:
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means for determining the start and end of each of said signal groups; means responsive to said information signals of each of said groups as determined by said determining means for calculating reflection coefficients for each of said signal groups; means responsive to said information signals and said reflection coefficients for each of said signal groups for generating a residual energy level for each of said signal groups; means for averaging said reflection coefficients of said signal groups and said residual energy levels of said signal groups; and means responsive to said averaged reflection coefficients and said averaged residual energy level for generating the average power spectrum. - View Dependent Claims (2, 3, 4)
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5. A blood flow analysis system for measuring velocity of blood moving within a patient'"'"'s internal structures, comprising:
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means for transmitting a beam of ultrasonic frequency acoustic waves into said patient structures; means for receiving the reflected acoustical echoed signals from moving acoustic scatterers in said blood; means for determining signals representing the difference between said transmitted and said received signals; means for sampling said difference signals for a plurality of cardiac cycles; means for determining the start and end of each of the patient'"'"'s cardiac cycles in response to electrocardiogram signals from said patient; means responsive to said start and end of each of said cardiac cycles and said sampled difference signals for each individual cardiac cycle for dividing said sampled difference signals into a predefined number of time segments of signals each representing the same amount of time with the total amount of time equal to each individual cardiac cycle; means responsive to said sampled difference signals for each of said time segments for calculating reflection coefficients modeling said blood flow; means responsive to said sampled difference signals and said reflection coefficients for generating a residual energy level for each of said time segments representing the energy not accounted for by said modeling; means responsive to said residual energy level and said reflection coefficients for each individual time segment of all cardiac cycles for averaging said reflection coefficients and said residual energy levels; and means responsive to said averaged reflection coefficients and said averaged residual energy level of each individual time segment for determining the average power spectrum of each individual time segment. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A blood flow analysis system for measuring the velocity of blood moving within internal patient vessels, comprising:
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means for transmitting a beam of ultrasonic frequency acoustic signals into said patient vessels for a plurality of cardiac cycles; means for receiving the reflected acoustic echoed signals from moving blood cells in said blood vessels over said plurality of cardiac cycles; means for determining signals representing the difference between said transmitted and received signals; means for sampling the difference signals; a first set of program instructions for determining the start and end of each of said cardiac cycles in response to said patient'"'"'s electrocardiogram signals; a second set of program instructions responsive to said start and end of each of said plurality of cardiac cycles and said corresponding sampled difference signals of each of said plurality of cardiac cycles for dividing said corresponding sampled difference signals into a predefined number of channels of said sampled difference signals for each of said plurality of cardiac cycles with each channel representing the same amount of time with the total amount of time of all channels of a particular cardiac cycle equal to that cardiac cycle; a third set of program instructions responsive to said sampled difference signals of each of said channels for generating reflection coefficients for modeling the amount of blood movement for all of said cycles; a fourth set of program instructions responsive to said reflection coefficients and said sampled difference signals for each of said channels for all of said cardiac cycles for generating a residual energy level for each of said channels representing energy not accounted for by said modeling; a fifth set of program instructions responsive to said reflection coefficients for a particular channel for all cardiac cycles for determining the average of said reflection coefficients for said particular channel for all of said cardiac cycles; a sixth set of program instructions responsive to said residual energy level for a particular channel for all cycles for determining the average of said residual energy levels for said particular channel for all of said cardiac cycles; a seventh set of program instructions for calculating the total energy of all sampled difference signals for each particular channel for all of said cardiac cycles; a eighth set of program instructions for calculating the average energy spectrum from said averaged reflection coefficients and average residual energy level for each of the averaged channels; an ninth set of program instructions for dividing the averaged power spectrum by said total energy for each of said averaged channels to produce a normalized power spectrum for each averaged channel; and a tenth set of program instructions responsive to normalized power spectrum for displaying said normalized power spectrum for each of said averaged channels. - View Dependent Claims (13)
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14. A method for measuring blood flow within internal blood vessel of a patient by analyzing sampled reflected ultrasonic signals from moving blood cells within the vessels during cardiac cycles and electrocardiogram signals received from said patient, comprising the steps of:
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determining the start and end of aid patient'"'"'s cardiac cycles in response to said electrocardiogram signals; dividing said sampled reflected ultrasonic signals up into a predefined number of time channels for each of said cardiac cycles with the total of said time channels corresponding to that one of said cardiac cycles; calculating reflection coefficients modeling said blood flow in response to said sampled reflected ultrasonic signals for each channel for all of said cardiac cycles; computing a residual energy level for each of said time channels of all cardiac cycles representing the energy not accounted for by said modeling; averaging said reflection coefficients and said residual energy levels for each individual time channel of all cardiac cycles; and determining the average power spectrum of each of the combined time channels in response to the average reflection coefficients and the average residual energy level for each of said combined time channels. - View Dependent Claims (15, 16, 17)
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Specification