Formation of ultrasound based heating regions adjacent blood vessels

Abstract

An ultrasound system used for both imaging and delivery high intensity ultrasound energy therapy to treatment sites and a method for treating tumors and other undesired tissue within a patient's body with an ultrasound device. The ultrasound device has an ultrasound transducer array disposed on a distal end of an elongate, relatively thin shaft. In one form of the invention, the transducer array is disposed within a liquid-filled elastomeric material that more effectively couples ultrasound energy into the tumor, that is directly contacted with the device. Using the device in a continuous wave mode, a necrotic zone of tissue having a desired size and shape (e.g., a necrotic volume selected to interrupt a blood supply to a tumor) can be created by controlling at least one of the f-number, duration, intensity, and direction of the ultrasound energy administered. This method speeds the therapy and avoids continuously pausing to enable intervening normal tissue to cool.

What is claimed is: 
     
         1 . A method comprising:
 providing an ultrasonic transducer array configured to emit focused high intensity ultrasound energy;   determining a treatment zone; and   energizing the ultrasonic transducer array to cause pre-focal heating of a substantial portion of tissue between the transducer array and a focal point of the transducer array, wherein the focal point is directed to the treatment zone.   
     
     
         2 . The method of  claim 1 , wherein the pre-focal heating raises a temperature of the tissue to about 50° C. 
     
     
         3 . The method of  claim 2 , wherein energizing the ultrasonic transducer array raises a temperature of the focal point to between about 70° C. and about 90° C. 
     
     
         4 . The method of  claim 3 , wherein energizing the ultrasonic transducer array forms a lesion at the focal point. 
     
     
         5 . The method of  claim 1 , wherein the treatment zone is determined such that a necrosis at the treatment zone causes a decrease in a blood supply to a tumor. 
     
     
         6 . The method of  claim 1 , comprising imaging the treatment zone. 
     
     
         7 . The method of  claim 6 , wherein the ultrasonic transducer array is configured to emit ultrasound imaging pulses. 
     
     
         8 . The method of  claim 6 , wherein energizing the ultrasonic transducer array to cause pre-focal heating and imaging the treatment zone are performed simultaneously. 
     
     
         9 . The method of  claim 6 , wherein imaging the treatment zone comprises Doppler flow imaging of blood flow. 
     
     
         10 . The method of  claim 1 , further comprising disposing a balloon between the ultrasonic transducer array and the treatment zone to acoustically couple the ultrasonic transducer array with the treatment zone. 
     
     
         11 . The method of  claim 10 , wherein the balloon comprises a semi-permeable membrane. 
     
     
         12 . The method of  claim 1 , wherein the treatment zone includes a volume disposed adjacent to a blood vessel. 
     
     
         13 . The method of  claim 1 , further comprising introducing the ultrasonic transducer array into a body cavity. 
     
     
         14 . The method of  claim 1 , wherein the ultrasonic transducer array is further configured to generate ultrasonic pulses and to receive ultrasonic echoes. 
     
     
         15 . A method comprising:
 providing an ultrasonic transducer array configured to emit focused high intensity ultrasound energy;   determining a treatment zone disposed adjacent to a blood vessel; and   energizing the ultrasonic transducer array to cause pre-focal heating of a substantial portion of tissue between the transducer array and a focal point of the transducer array, wherein the focal point is directed to the treatment zone.   
     
     
         16 . The method of  claim 15 , further comprising providing an ultrasonic signal to the ultrasonic transducer array.