System and method for shear wave elastography by transmitting ultrasound with subgroups of ultrasound transducer elements
Systems and methods for performing shear wave elastography using push and/or detection ultrasound beams that are generated by subsets of the available number of transducer elements in an ultrasound transducer. These techniques provide several advantages over currently available approaches to shear wave elastography, including the ability to use a standard, low frame rate ultrasound imaging system and the ability to measure shear wave speed throughout the entire field-of-view rather than only those regions where the push beams are not generated.
1. A method for measuring a mechanical property of an object using an ultrasound system having an ultrasound transducer that includes a plurality of transducer elements, the steps of the method comprising:
a) controlling the ultrasound transducer to energize a plurality of subgroups of transducer elements to transmit a corresponding plurality of different focused ultrasound beams each focused at a different lateral location and each transmitted at a different time, thereby inducing multiple different shear waves in the object;
b) for each different lateral location, obtaining elastography data representative of the multiple different shear waves by transmitting at least one detection ultrasound beam into the object and receiving echo signals in response thereto;
c) generating processed elastography data by processing the obtained elastography data to separate the multiple different shear waves into multiple different directional components to reduce effects of interference between the multiple different shear waves; and
d) calculating a mechanical property of the object using the processed elastography data.
2. The method as recited in claim 1 , wherein at least some successively transmitted focused ultrasound beams are generated in step a) by spatially adjacent subgroups of transducer elements.
3. The method as recited in claim 1 , wherein at least some successively transmitted focused ultrasound beams are generated in step a) by spatially overlapping subgroups of transducer elements.
4. The method as recited in claim 1 , wherein step b) includes:
i) dividing the transducer elements in the ultrasound transducer into a plurality of subgroups of transducer elements;
ii) successively transmitting a set of ultrasound beams using a different subgroup of transducer elements, thereby successively transmitting ultrasound to different regions in the object;
iii) repeating step ii) at a pulse repetition frequency such that each set of ultrasound beams is effectively repeated at the pulse repetition frequency.
5. The method as recited in claim 1 , wherein step c) includes applying a directional filter to the elastography data.
6. The method as recited in claim 1 , wherein step a) includes transmitting at least some of the plurality of different focused ultrasound beams to focus at different depth locations than other ones of the plurality of different focused ultrasound beams.
7. The method as recited in claim 1 , wherein the plurality of different focused ultrasound beams are transmitted in sequential sets, wherein each set contains multiple simultaneously generated focused ultrasound beams that are focused at different locations.
8. The method as recited in claim 1 , wherein calculating the mechanical property in step d) includes using at least one of a time-to-peak method, a cross-correlation method, a direct inversion method, and a frequency dependent analysis method.
9. The method as recited in claim 1 , wherein at least some of the plurality of focused ultrasound beams are transmitted for a longer duration than others of the plurality of focused ultrasound beams.
10. The method as recited in claim 1 , wherein some of the plurality of subgroups of transducer elements include more transducer elements than others of the plurality of subgroups of transducer elements.