Ultrasonic elasticity imaging

An ultrasound imaging method comprising the following steps:

• A) repeatedly scanning a region of interest (ROI) of a body with an ultrasound transducer;
• B) applying varying stress to the ROI;
• C) acquiring first ultrasound echo samples at a first stress level, and second ultrasound echo samples at a second stress level that differs from the first stress level, the first and second echo data samples each representing the ROI;
• D) selecting a reference sample set among first ultrasound echo samples;
• E) for each of the first samples in the reference sample set, which comprise reference samples, searching within a first search region for a corresponding second sample;
• F) for the first samples not in the reference sample set, which comprise non-reference samples, searching within a second search region for the corresponding second sample, the second search region being smaller than the first search region, measured in number of samples included in the respective search region;
• G) for each reference sample, calculating a displacement vector estimate having first and second displacement components corresponding to estimated displacement of the respective reference sample in a first and a second direction, respectively;
• H) for each non-reference sample:
• i) assigning as the second displacement component the calculated second displacement component of the reference sample in the reference sample set with which the respective non-reference sample is collocated in the second direction;
• and
• ii) calculating the first displacement component corresponding to estimated displacement in the first direction;
• I) estimating displacement of tissue within the ROI from the difference in estimated positions between the first and second samples and therefrom generating and displaying a first representation of a function of the estimated tissue displacement;
• and
• J) generating and updating the first representation with a frame rate at least as fast as a predetermined minimum rate necessary for coordination by a user of transducer movement with the display of the first representation.

An ultrasound imaging method comprising the following steps:

• A) repeatedly scanning a region of interest (ROI) of a body with an ultrasound transducer;
• B) applying varying stress to the ROI;
• C) acquiring first ultrasound echo samples at a first stress level, and second ultrasound echo samples at a second stress level that differs from the first stress level, the first and second echo data samples each representing the ROI;
• D) selecting a reference sample set among first ultrasound echo samples;
• E) for each of the first samples in the reference sample set, which comprise reference samples, searching within a first search region for a corresponding second sample;
• F) for the first samples not in the reference sample set, which comprise non-reference samples, searching within a second search region for the corresponding second sample, the second search region being smaller than the first search region, measured in number of samples included in the respective search region;
• G) estimating displacement of tissue within the ROI from the difference in estimated positions between the first and second samples and therefrom generating and displaying a first representation of a function of the estimated tissue displacement;
• H) for each reference sample, calculating a displacement vector estimate having first and second displacement components corresponding to estimated displacement of the respective reference sample in a first and a second direction, respectively;
• I) for each non-reference sample:
• i) assigning as the second displacement component the calculated second displacement component of the reference sample in the reference sample set with which the respective non-reference sample is collocated in the second direction;
• and
• ii) calculating the first displacement component corresponding to estimated displacement in the first direction;
• J) generating the first representation with a first quality in a real-time mode;
• K) in a post-processing, non-real time mode:
• i) comparing the first and second ultrasound echo data samples and therefrom calculating a post-processed displacement estimate of the tissue within the ROI;
• and
• ii) generating a second representation of the post-processed displacement estimate with a second quality that is greater than the first quality.

An ultrasound imaging method comprising the following steps:

• A) repeatedly scanning a region of interest (ROI) of a body with an ultrasound transducer;
• B) applying varying stress to the ROI;
• C) acquiring first ultrasound echo samples at a first stress level, and second ultrasound echo samples at a second stress level that differs from the first stress level, the first and second echo data samples each representing the ROI;
• D) selecting a reference sample set among first ultrasound echo samples;
• E) for each of the first samples in the reference sample set, which comprise reference samples, searching within a first search region for a corresponding second sample;
• F) for the first samples not in the reference sample set, which comprise non-reference first samples, searching within a second search region for the corresponding second sample;
• G) estimating displacement of tissue within the ROI from the difference in estimated positions between the first and second samples and therefrom generating and displaying a first representation of a function of the estimated tissue displacement;
• in which:
• H) the second search region is smaller than the first search region, measured in number of samples included in the respective search region;
• I) the steps of acquiring the first and second ultrasound echo samples comprise:
• i) transmitting into the ROI a first and second series of transmit beams of ultrasound, respectively;
• ii) for each transmit beam, receiving a corresponding echo signal;
• iii) representing the echo signals as the first and second samples, the ROI thereby being represented as at least two-dimensional, first and second arrays of the first and second sample values, respectively;
• J) the step of estimating displacement of tissue within the ROI comprises:
• i) for at least one current base sample, chosen as one of selected ones of the first samples, selecting a base sample kernel comprising the first sample values located in a current region surrounding the current base sample;
• ii) for each second sample located in a search region, which comprises the second samples located within a second sample kernel,
• a) selecting a second sample kernel having the same dimensions, measured in numbers of samples, as the base sample kernel;
• b) calculating an energy function that is a predetermined function of the differences between the second sample values within the second sample kernel and corresponding first sample values in the base sample kernel;
• further comprising the following steps:
• K) designating as an optimum second sample the second sample for which the energy function is optimized;
• L) calculating a displacement vector estimate between the current base sample and the optimum second sample;
• M) calculating a display value of a predetermined function of the displacement vector estimate;
• N) repeating steps B)-E) for each base sample, thereby generating a corresponding display value for each of the remaining base samples;
• O) displaying the display values;
• P) estimating the reliability of the displacement vector estimate for at least a reference one of the base samples;
• and
• Q) dynamically adjusting the search region a function of the estimated reliability.

An ultrasound imaging system comprising:

• means for applying varying stress to a region of interest (ROI) of a body;
• an ultrasound transducer forming means for repeatedly scanning the ROI and for acquiring first ultrasound echo samples at a first stress level, and second ultrasound echo samples at a second stress level that differs from the first stress level, the first and second echo data samples each representing the ROI;
• processing means:
• for selecting a reference sample set among first ultrasound echo samples;
• for each of the first samples in the reference sample set, which comprise reference samples, for searching within a first search region for a corresponding second sample;
• for the first samples not in the reference sample set, which comprise non-reference samples, for searching within a second search region for the corresponding second sample, the second search region being smaller than the first search region, measured in number of samples included in the respective search region;
• and
• displacement estimation means, included within the processing means, for estimating displacement of tissue within the ROI from the difference in estimated positions between the first and second samples and therefrom for generating and displaying a first representation of a function of the estimated tissue displacement.