Frequency optimization in ultrasound treatment

Abstract

In ultrasound therapy, the frequency of sonications can be optimized, within a certain frequency range, to maximize the absorption or the acoustic intensity at the target in a manner specific to the patient.

What is claimed is: 
     
         1 . A patient-specific frequency-optimization method for ultrasound therapy of a target within the patient, the method comprising:
 (a) for at least one segment of an ultrasound transducer and for each of a plurality of ultrasound frequencies within a test range, sonicating the target and measuring a parameter correlated with an amount of ultrasound energy absorbed in the target; and   (b) for each said at least one segment, selecting for subsequent ultrasound therapy, among the frequencies within the test range, a frequency corresponding to a value of the measured parameter that itself corresponds to a maximum amount of ultrasound energy absorbed in the target.   
     
     
         2 . The method of  claim 1 , further comprising, following frequency selection in step (b), driving the at least one segment at the selected frequency and at a therapeutic energy level to thereby sonicate the target, the therapeutic energy level exceeding an energy level of sonications applied in step (a). 
     
     
         3 . The method of  claim 1 , further comprising defining a plurality of segments within the ultrasound transducer based, at least in part, on an anatomy of the patient. 
     
     
         4 . The method of  claim 3 , wherein steps (a) and (b) are performed for each of the segments, the method further comprising, during ultrasound therapy, driving the segments together, each at its respective selected frequency. 
     
     
         5 . The method of  claim 1 , wherein the plurality of frequencies within the test range is defined dynamically based, at least in part, on a value of the parameter measured for a previously tested frequency. 
     
     
         6 . The method of  claim 1 , wherein the parameter is selected from the group consisting of a power, an energy, an intensity, an acoustic force, a tissue displacement, and a temperature. 
     
     
         7 . The method of  claim 1 , wherein the parameter is measured using thermometry. 
     
     
         8 . A system for selecting a patient-specific frequency for ultrasound therapy of a target within the patient, the system comprising:
 an ultrasound transducer and an associated controller capable of driving the transducer at any frequency within a test range of frequencies so as to sonicate the target;   a measurement facility for measuring a parameter correlated with an amount of ultrasound energy absorbed in the target; and   a computational facility for (i) causing the ultrasound transducer controller to drive at least one segment of the transducer sequentially at each of a plurality of frequencies within the test range so as to sonicate the target, (ii) causing the measuring facility to measure a parameter correlated with an amount of ultrasound energy absorbed in the target for each of the frequencies, and (iii) for each of the at least one segment, selecting for subsequent focused-ultrasound therapy, among the frequencies within the test range, a frequency corresponding to a value of the measured parameter that itself corresponds to a maximum amount of ultrasound energy absorbed in the target.   
     
     
         9 . The system of  claim 8 , wherein the measurement facility comprises a magnetic-resonance imaging apparatus. 
     
     
         10 . The system of  claim 8 , wherein the ultrasound transducer comprises a plurality of segments. 
     
     
         11 . The system of  claim 10 , wherein the controller is configured to cause the ultrasound transducer, during ultrasound therapy, to drive the segments together, each at its respective selected frequency. 
     
     
         12 . A patient-specific frequency-optimization method for ultrasound therapy of a target within the patient, the method comprising:
 defining a plurality of segments within an ultrasound transducer array; and   separately for each of the segments, driving the segment successively at each of a plurality of frequencies within a test frequency range so as to sonicate the target, and   measuring a parameter correlated with an amount of ultrasound energy absorbed in the target for each of the frequencies; and   for each of the plurality of frequencies, combining values of the parameter measured for the plurality of segments into a total parameter value correlated with a total amount of ultrasound energy absorbed in the target; and   selecting for subsequent focused-ultrasound therapy, among the plurality of frequencies, a frequency corresponding to a value of the measured total parameter that itself corresponds to a maximum total amount of ultrasound energy absorbed in the target.   
     
     
         13 . The method of  claim 12 , wherein the parameter is selected from the group consisting of a power, an energy, an intensity, an acoustic force, a tissue displacement, or a temperature. 
     
     
         14 . The method of  claim 12 , wherein the parameter is measured using thermometry. 
     
     
         15 . The method of  claim 12 , wherein the parameters is measured using acoustic radiation force imaging. 
     
     
         16 . A system for selecting a patient-specific frequency for ultrasound therapy of a target within the patient, the system comprising:
 an ultrasound transducer comprising a plurality of segments, and an associated controller capable of driving each of the transducer segments at any of a plurality of frequencies within a range of frequencies so as to sonicate the target;   a measurement facility for measuring a parameter correlated with an amount of ultrasound energy absorbed in the target; and   a computational facility for (i) causing the ultrasound transducer controller to separately drive each of the segments sequentially at each of a plurality of frequencies within a test range so as to sonicate the target, (ii) causing the measurement facility to measure a parameter correlated with an amount of ultrasound energy absorbed in the target for each of the frequencies, (iii) for each of the plurality of frequencies, combining values of the parameter measured for the plurality of segments into a total parameter value correlated with a total amount of ultrasound energy absorbed in the target, and (iv) selecting for subsequent focused-ultrasound therapy, among the plurality of frequencies, an optimal frequency corresponding to a value of the measured total parameter that itself corresponds to a maximum total amount of ultrasound energy absorbed in the target.   
     
     
         17 . The system of  claim 16 , wherein the measurement facility comprises a magnetic-resonance imaging apparatus. 
     
     
         18 . The system of  claim 16 , wherein the measured parameter is a tissue displacement. 
     
     
         19 . The system of  claim 16 , wherein the controller is configured to cause the ultrasound transducer, during ultrasound therapy, to drive the segments together at the selected optimal frequency.