Controlled, non-linear focused ultrasound treatment

Abstract

A system for treating tissue within a body is configured to deliver a first level of ultrasound energy to a target tissue region for a first duration resulting in the generation of microbubbles in the target tissue region, determine one or more characteristics of the target tissue region in the presence of the microbubbles, and deliver a second level of ultrasound energy to the target tissue region for a second duration, wherein one or both of the second energy level and the second duration are based, at least in part, on the determined one or more characteristics of the target tissue region.

1 . A method of treating tissue within a body, comprising: 
 delivering a first level of ultrasound energy to a target tissue region for a first duration resulting in the generation of microbubbles in the target tissue region;    determining one or more characteristics of the target tissue region in the presence of the microbubbles; and    delivering a second level of ultrasound energy to the target tissue region for a second duration, wherein one or both of the second energy level and the second duration are based, at least in part, on the determined one or more characteristics of the target tissue region.    
     
     
         2 . The method of  claim 1 , wherein each of the first duration and second duration are between 0.05 to 3 seconds.  
     
     
         3 . The method of  claim 1 , wherein the second energy level is determined by adjusting one or more of a frequency, a phase, and an amplitude of a drive signal used to generate the first energy level in order to achieve a maximum coagulation volume while controlling a coagulation location.  
     
     
         4 . The method of  claim 1 , wherein the second level of ultrasound energy is delivered to a different focal location in the target tissue region than the first level.  
     
     
         5 . The method of  claim 1 , wherein the second level of ultrasound energy is based, at least in part, on maintaining a temperature of the target tissue region above a prescribed threshold temperature.  
     
     
         6 . The method of  claim 1 , wherein the second level of ultrasound energy is based, at least in part, on maintaining a temperature of the target tissue region below a prescribed threshold temperature.  
     
     
         7 . The method of  claim 1 , wherein the one or more characteristics of the target tissue region are determined, at least in part, by obtaining a temperature sensitive image of the target tissue region.  
     
     
         8 . The method of  claim 1 , wherein the one or more characteristics of the target tissue region are determined, at least in part, by obtaining an actual thermal dose distribution associated with the target tissue region, and comparing the obtained actual thermal dose distribution with a predicted thermal dose distribution.  
     
     
         9 . The method of  claim 1 , wherein the second ultrasound energy level is different from the first ultrasound energy level.  
     
     
         10 . The method of  claim 1 , further comprising repeating the steps of 
 determining one or more characteristics of the target tissue region in the presence of microbubbles in the target tissue region, and    delivering the second level of ultrasound energy to the target tissue region,    until a desired effect on the target tissue region is achieved.    
     
     
         11 . A system for treating tissue within a body, comprising: 
 means for delivering a first level of ultrasound energy to a target tissue region for a first duration resulting in the generation of microbubbles in the target tissue region;    means for determining one or more characteristics of the target tissue region in the presence of the microbubbles; and    means for delivering a second level of ultrasound energy to the target tissue region for a second duration, wherein one or both of the second energy level and second duration are based, at least in part, on the determined one or more characteristics of the target tissue region.    
     
     
         12 . A controller for a focused ultrasound system, the focused ultrasound system having a plurality of transducer elements for delivering ultrasound energy to a target tissue region in a patient's body, the controller configured to: 
 cause the delivery of a first level of ultrasound energy to the target tissue region for a first duration resulting in the generation of microbubbles in the target tissue region;    determine one or more characteristics of the target tissue region in the presence of the microbubbles; and    cause the delivery of a second level of ultrasound energy to the target tissue region for a second duration, wherein one or both of the second ultrasound energy level and the second duration are based, at least in part, on the determined one or more characteristics of the target tissue region.    
     
     
         13 . The system of  claim 12 , wherein each of the first duration and second duration are between 0.05 to 3 seconds.  
     
     
         14 . The system of  claim 12 , wherein the second energy level is determined by adjusting one or more of a frequency, a phase, and an amplitude of a drive signal used to generate the first energy level in order to achieve a maximum coagulation volume while controlling a coagulation location.  
     
     
         15 . The system of  claim 12 , wherein the second level of ultrasound energy is delivered to a different focal location in the target tissue region than the first level.  
     
     
         16 . The system of  claim 12 , wherein the second level of ultrasound energy is based, at least in part, on maintaining a temperature of the target tissue region above a prescribed threshold temperature.  
     
     
         17 . The system of  claim 12 , wherein the second level of ultrasound energy is based, at least in part, on maintaining a temperature of the target tissue region below a prescribed threshold temperature.  
     
     
         18 . The system of  claim 12 , wherein the one or more characteristics of the target tissue region are determined, at least in part, by obtaining a temperature sensitive image of the target tissue region.  
     
     
         19 . The system of  claim 12 , wherein the one or more characteristics of the target tissue region are determined, at least in part, by obtaining an actual thermal dose distribution associated with the target tissue region, and comparing the obtained actual thermal dose distribution with a predicted thermal dose distribution.  
     
     
         20 . The system of  claim 12 , wherein the second ultrasound energy level is different from the first ultrasound energy level.  
     
     
         21 . The system of  claim 12 , wherein the controller is configured to repeat the processes of determining one or more characteristics of the target tissue region in the presence of microbubbles in the target tissue region, and delivering the second level of ultrasound energy to the target tissue region, until a desired effect on the target tissue region is achieved.