Ultrasonic technique for assessing wall vibrations in stenosed blood vessels

A method for detecting a stenosis, comprising the steps of:

• generating and collecting ultrasound data reflected from an internal site using an ultrasound machine including an ultrasound transducer and an ultrasound back-end subsystem;
• yielding an ultrasound signal;
• processing the ultrasound signal using a tissue vibration processor to obtain a tissue vibration signal corresponding to soft-tissue vibrations at the internal site caused by blood flow turbulence, the blood flow turbulence being indicative of the stenosis, wherein contributions from sources other than soft tissue vibrations caused by the stenosis have been reduced in the
• tissue vibration signal;
• carrying out the following with the ultrasound back-end subsystem programmed with non-transitory computer readable media instructions:
• from the tissue vibration signal, the vibration image indicating a spatial position of the soft-tissue vibrations caused by blood flow turbulence relative to the internal site;
• generating a B-mode image from the ultrasound signal showing underlying anatomy of the internal site;
• generating a color-flow image from the ultrasound signal indicative of blood flow at the internal site;
• overlaying the generated vibration image with the generated B-mode image and with the generated color-flow image so as to provide stenosis position information with reference to the underlying anatomy and blood flow of the internal site.

A method for detecting a stenosis using ultrasound data, comprising the steps of:

• generating ultrasound data reflected from an internal site using an ultrasound machine including an ultrasound transducer;
• processing the ultrasound data using a tissue vibration processor, programmed with non-transitory computer readable media instructions, to identify tissue vibrations at the internal site, producing a tissue vibration signal from which contributions to the tissue vibration from a source other than blood flow turbulence, the blood flow turbulence being indicative of the stenosis at the internal site has been reduced, said tissue vibration signal providing an indication of the stenosis, wherein processing the ultrasound data comprises:
• (a) estimating a correlation signal from an ensemble of the ultrasound data;
• (b) carrying out an eigen decomposition of the correlation signal to identify a signal subspace and a noise subspace;
• (c) estimating a frequency of dominant vibration components in the signal subspace and the noise subspace;
• and
• (d) based upon an estimate of the frequency of the dominant vibration components, determining a vibration amplitude and a vibration frequency, at least one of the vibration amplitude and the vibration frequency comprising the tissue vibration signal;
• and
• outputting an indication of the tissue vibration signal to a user in a format perceptible to the user, to enable the user to detect the stenosis, wherein the indication conveys to the user that a stenosis is present at the internal site.

A method for detecting a stenosis using ultrasound data, comprising the steps of:

• generating ultrasound data reflected from an internal site using an ultrasound machine including an ultrasound transducer;
• processing the ultrasound data using a tissue vibration processor, programmed with non-transitory computer readable media instructions, to identify tissue vibrations at the internal site, producing a tissue vibration signal from which contributions to the tissue vibration from a source other than blood flow turbulence, the blood flow turbulence being indicative of the stenosis at the internal site has been reduced, said tissue vibration signal providing an indication of the stenosis, wherein processing the ultrasound data comprises:
• (a) computing coefficients of an autoregressive process from an ensemble of the ultrasound data;
• (b) computing linear prediction filter coefficients from the coefficients;
• (c) estimating a power spectrum from the linear prediction filter coefficients and detecting peaks in the power spectrum;
• and
• (d) based upon an estimate of the power spectrum and the peaks, determining a vibration amplitude and a vibration frequency, at least one of the vibration amplitude and the vibration frequency comprising the tissue vibration signal;
• and
• outputting an indication of the tissue vibration signal to a user in a format perceptible to the user, to enable the user to detect the stenosis, wherein the indication conveys to the user that a stenosis is present at the internal site.

Apparatus for detecting a stenosis at an internal site using ultrasound, comprising:

• an ultrasound transducer configured to receive ultrasound data;
• an ultrasound transducer controller coupled to the ultrasound transducer to control operation of the ultrasound transducer;
• and
• an ultrasound back-end subsystem configured to:
• process the ultrasound data to identify tissue vibrations caused by the stenosis, thereby producing a tissue vibration signal corresponding to soft-tissue vibrations at the internal site caused by blood flow turbulence, the blood flow turbulence being indicative of the stenosis, wherein contributions from sources other than soft tissue vibrations caused by the stenosis have been reduced in the tissue vibration signal;
• generate a vibration image from the tissue vibration signal with a tissue vibration processor;
• generate a B-mode image from the ultrasound signal showing underlying anatomy of the internal site;
• overlay the generated vibration image with the generated B-mode image;
• and
• output the overlaid images so as to provide stenosis position information with reference to the underlying anatomy and blood flow of the internal site.

Apparatus for detecting a stenosis at an internal site using ultrasound, comprising:

• an ultrasound transducer for receiving ultrasound data;
• an ultrasound transducer controller coupled to the ultrasound transducer to control its operation;
• and
• a tissue vibration processor that processes the ultrasound to identify tissue vibrations caused by the stenosis, producing a tissue vibration signal corresponding to soft-tissue vibrations at the internal site caused by blood flow turbulence, the blood flow turbulence being indicative of the stenosis, wherein contributions from sources other than soft tissue vibrations caused by the stenosis have been reduced in the tissue vibration signal, wherein the tissue vibration processor determines tissue vibrations at the internal site by:
• (a) estimating a correlation matrix from the color-flow signal;
• (b) carrying out an eigen decomposition of the correlation matrix to identify a signal subspace and a noise subspace;
• (c) estimating a frequency of dominant vibration components in the signal subspace and the noise subspace;
• and
• (d) based upon an estimate of the frequency of the dominant vibration components, determining a vibration amplitude estimate and a vibration frequency estimate, at least one of the vibration amplitude estimate and the vibration frequency estimate comprising the tissue vibration signal.

Apparatus for detecting a stenosis at an internal site using ultrasound, comprising:

• an ultrasound transducer for receiving ultrasound data;
• an ultrasound transducer controller coupled to the ultrasound transducer to control its operation;
• and
• a tissue vibration processor that processes the ultrasound to identify tissue vibrations caused by the stenosis, producing a tissue vibration signal corresponding to soft-tissue vibrations at the internal site caused by blood flow turbulence, the blood flow turbulence being indicative of the stenosis, wherein contributions from sources other than soft tissue vibrations caused by the stenosis have been reduced in the tissue vibration signal, wherein the tissue vibration processor determines tissue vibrations at the internal site by:
• (a) estimating a mean clutter velocity from the color-flow signal, using autocorrelation;
• (b) down mixing the color-flow signal with the mean clutter velocity, producing a down mixed signal;
• (c) computing a phase of the down mixed signal and a mean phase of the down mixed signal;
• (d) subtracting the mean phase from the phase of the down mixed signal, producing a residual phase;
• (e) decomposing the residual phase into its dominant components;
• and
• (f) applying energy and frequency thresholds to substantially suppress any contribution to the tissue vibration due to noise and blood flow, yielding an estimate of vibration amplitude and vibration frequency of tissue.

Apparatus for detecting a stenosis at an internal site using ultrasound, comprising:

• an ultrasound transducer configured to receive ultrasound data;
• an ultrasound transducer controller coupled to the ultrasound transducer to control operation of the ultrasound transducer;
• and
• an ultrasound back-end subsystem configured to:
• process the ultrasound data to identify tissue vibrations caused by the stenosis, thereby producing a tissue vibration signal corresponding to soft-tissue vibrations at the internal site caused by blood flow turbulence, the blood flow turbulence being indicative of the stenosis, wherein contributions from sources other than soft tissue vibrations caused by the stenosis have been reduced in the tissue vibration signal;
• generate a vibration image from the tissue vibration signal with a tissue vibration processor;
• produce a color-flow image indicative of blood flow at the internal site,
• overlay the color-flow image with the vibration image;
• and
• output the overlaid color-flow image with the vibration image to provide stenosis position information with reference to the blood flow at the internal site.

A method for detecting a stenosis, comprising the steps of:

• generating ultrasound data reflected from an internal site using an ultrasound machine including an ultrasound transducer and an ultrasound back-end subsystem;
• extracting tissue vibration data from the ultrasound data using a vibration processor, where the vibration processor decreases components of the ultrasound data induced by transducer movement, respiration and cardiac pulsation in the tissue vibration data, such that the tissue vibration data corresponds to vibrations caused by blood flow turbulence, the blood flow turbulence being
• indicative of the stenosis;
• carrying out the following with the ultrasound back-end subsystem programmed with non-transitory computer readable media instructions:
• from the tissue motion signal, the vibration image indicating a spatial position of the tissue motion relative to the internal site;
• generating a color-flow image from the ultrasound data indicative of blood flow at the internal site;
• overlaying the generated vibration image with the generated color-flow image so as to provide stenosis position information with reference to the blood flow at the internal site;
• and
• outputting the overlaid images.