Controlled high efficiency lesion formation using high intensity ultrasound

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 for administering an ultrasonic therapy to a target, comprising the steps of:
 (a) providing an ultrasonic transducer that emits a focused high energy ultrasonic energy when energized;   (b) positioning the ultrasonic transducer to focus it at an imaged target;   (c) directing the ultrasonic transducer toward a desired focal point within the target;   (d) energizing the ultrasonic transducer so that it emits the focused high energy ultrasonic energy at the desired focal point, causing heating of a portion of the target disposed at the desired focal point;   (e) creating a positive feedback process between the ultrasound transducer and the target; and   (f) utilizing an imaging technique to monitor the degree of tissue injury caused by the heating.   
     
     
         2 . The method of  claim 1 , wherein the heating creates a lesion and wherein a desired shape and size of the lesion are selected so that formation of the lesion substantially deprives the target of a blood supply, causing the ultimate destruction of the target. 
     
     
         3 . The method of  claim 1 , wherein the heating creates a lesion and wherein a desired shape and size of the lesion are selected to cause heating of a blood vessel. 
     
     
         4 . The method of  claim 1 , wherein the target is a blood vessel. 
     
     
         5 . The ultrasonic system of  claim 1 , wherein said high intensity ultrasonic energy is configured to heat tissue between the transducer and focal point to a temperature of 50° C. or more. 
     
     
         6 . The ultrasonic system of  claim 1 , wherein the heating creates a lesion wherein the lesion has a volume of about 4.5 cubic centimeters. 
     
     
         7 . The method of  claim 1 , wherein the target is a prostate. 
     
     
         8 . The method of  claim 7 , wherein imaging and therapy are interleaved in time to monitor the ultrasonic therapy. 
     
     
         9 . The method of  claim 7 , further comprising the step of administering ultrasound contrast prior to administering the ultrasound therapy. 
     
     
         10 . The method of  claim 9 , further comprising inducing cavitation to further increase tissue injury. 
     
     
         11 . The method of  claim 9 , further comprising the step of monitoring the formation of cavitation with the imaging. 
     
     
         12 . The method of  claim 7 , further comprising alternating between ultrasound therapy and ultrasound imaging to generate a plurality of ultrasound image frames during treatment.