System and method for focusing of high intensity focused ultrasound based on magnetic resonance - acoustic radiation force imaging feedback

A method for focusing a phased array of ultrasound transducer elements into a target tissue using MR-ARFI, the method comprising:

• calculating a pressure field for each transducer element in the phased array of ultrasound transducer elements to generate an unaberrated pressure field matrix;
• causing the phased array of ultrasound transducer elements to apply focused ultrasound to the ROI, wherein application of focused ultrasound by each transducer element of the phased array of ultrasound transducer elements generates a respective aberrated pressure field at a focus location in the target tissue and in a volume surrounding the focus location;
• acquiring magnetic resonance acoustic radiation force impulse (MR-ARFI) images of the focus location and the surrounding volume;
• based on the MR-ARFI images, measuring a magnitude of the aberrated pressure field generated by the applied focused ultrasound from each transducer element of the phased array of ultrasound transducer elements at its respective focus location in the target tissue and in the volume surrounding the focus location;
• determining an aberration for each transducer element of the phased array of ultrasound transducer elements from the pressure field matrix and the MR-ARFI images of the focus location and the surrounding volume using a magnitude least-squares method;
• and
• applying at least one of corrective phase adjustment and a corrective amplitude adjustment to each transducer element in the phased array of ultrasound transducer elements based on the determined aberration for each respective element.

A non-transitory computer readable storage medium having stored thereon a computer program comprising instructions that, when executed by a computer, cause the computer to:

• calculate a pressure field for each of a plurality of transducer elements in an ultrasound transducer to generate an unaberrated pressure field matrix, the ultrasound transducer configured to apply focused ultrasound to a target tissue;
• cause each of the plurality of transducer elements to apply focused ultrasound to the target tissue, with the application of focused ultrasound by each of the plurality of transducer elements generating a respective aberrated pressure field at a focus location in the target tissue and in a volume surrounding the focus location;
• acquire one or more magnetic resonance acoustic radiation force impulse (MR-ARFI) images of the focus location and the surrounding volume, each of the one or more MR-ARFI images comprising one or more voxels corresponding to the focus location and voxels corresponding to a region surrounding the focus location;
• measure a relative tissue displacement that each transducer element produces in the target tissue responsive to the applied focused ultrasound, the relative tissue displacement produced by each transducer element being measured using the voxels in the one or more MR-ARFI images corresponding to the focus location and the region surrounding the focus location;
• and
• calculate corrective phase and amplitude adjustments for each of the plurality of transducer elements based on the measured relative tissue displacement.