System for treating a volume of tissue with high intensity focused ultrasound

Abstract

A method and system for treating a desired volume of tissue using HIFU or other energy modality includes ablating a pattern of elemental treatment volumes each having a volume that is greater than that of the focal zone of the HIFU transducer but smaller than the overall volume of the desired treatment volume. In at least one embodiment, the elemental treatment volumes are arranged to form a shell which partially or wholly encapsulates the desired volume of tissue, which then necroses in situ. The elemental treatment volumes are created by distributing HIFU energy in multiple doses with repeated passes of the focal zone of the HIFU transducer in a trajectory over or along a perimeter of each elemental treatment volume.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A system for treating uterine fibroids or other uterine tissue, comprising:
 a hand-held or hand-guided HIFU applicator with a movable transducer focal zone that is configured to deliver HIFU treatment signals to a treatment site in a uterine fibroid or other uterine tissue;   an imaging transducer that produces imaging signals representative of the uterine fibroids or other uterine tissue; and   a processor programmed to determine a pattern in which to apply HIFU around the periphery of a fibroid or other targeted volume of uterine tissue and to control the position of the focal zone of the HIFU transducer to apply HIFU energy in this pattern.   
     
     
         2 . The system of  claim 1 , wherein the pattern in which HIFU is applied consists of a number of elemental treatment volumes created around the periphery of the fibroid or other targeted volume of uterine tissue. 
     
     
         3 . The system of  claim 2 , wherein each elemental treatment volume has size selected such that an interior region is treated by indirect heating as the treatment energy is repeatedly applied to a perimeter of the elemental treatment volume. 
     
     
         4 . The system of  claim 2 , wherein the processor is programmed to control the position the focal zone of the HIFU transducer in a pattern to create a number of elemental treatment volumes within an interior of the uterine fibroid or the targeted volume of uterine tissue. 
     
     
         5 . The system of  claim 1 , wherein the HIFU treatment signals are transmitted at a power sufficient to convert a substantial portion of the power at a fundamental frequency of the therapeutic HIFU signals to power in the harmonics of the fundamental frequency at the treatment site. 
     
     
         6 . The system of  claim 5 , wherein the processor is programmed to determine a power level for the HIFU treatment signals such that a substantial portion of the power at a fundamental frequency of the therapeutic HIFU signals is converted to power in the harmonics of the fundamental frequency at the treatment site based on a number of test signals transmitted at different power levels. 
     
     
         7 . The system of  claim 2 , wherein the elemental treatment volume is cylindrical and has a diameter approximately equal to a length of the focal zone. 
     
     
         8 . The system of  claim 1 , wherein the processor is programmed to control a mechanical linkage that adjusts the position of the HIFU transducer to move the focal zone. 
     
     
         9 . The system of  claim 1 , wherein the processor is programmed to control an electronic beam steerer to move the focal zone. 
     
     
         10 . The system of  claim 1 , wherein the processor is programmed to automatically detect the boundaries of the uterine fibroid or other volume of uterine tissue to be treated. 
     
     
         11 . The system of  claim 1 , wherein the processor is programmed to receive input from a user that is indicative of the boundaries of the uterine fibroid or other volume of uterine tissue to be treated. 
     
     
         12 . A system for thermally necrosing a uterine fibroid or other uterine tissue with high intensity focused ultrasound (HIFU), comprising:
 a hand-held or hand-guided HIFU applicator with a movable transducer focal zone that is configured to deliver therapeutic HIFU signals having a fundamental frequency to the treatment site;   a transmit controller configured to supply driving signals to the HIFU transducer such the transducer produces therapeutic HIFU signals at a power sufficient to convert a substantial portion of the power at a fundamental frequency of the therapeutic HIFU signals to power in the harmonics of the fundamental frequency at the treatment site; and   a position controller that is configured to position the focal zone of the HIFU transducer in the uterine fibroid or other uterine tissue to create one or more elemental treatment volumes without temperature feedback.   
     
     
         13 . The system of  claim 12 , wherein each elemental treatment volume is a cylinder having a diameter substantially equal to a length of the focal zone. 
     
     
         14 . The system of  claim 12 , wherein the power of the HIFU treatment signals is selected that the HIFU treatment signals reach or exceed the onset of shock at the treatment site. 
     
     
         15 . A system for treating a volume of tissue at a treatment site with high intensity focused ultrasound (HIFU), the system comprising:
 a HIFU transducer that delivers HIFU treatment signals to tissue at a movable focal zone within the treatment site; and   one or more processors programmed to control a supply of driving signals to the HIFU transducer that cause the HIFU transducer to deliver the HIFU treatment signals to the treatment site at a selected power, and further to control positioning of the focal zone of the HIFU transducer such that the HIFU treatment signals create a plurality of elemental treatment volumes at a periphery of the volume of tissue,   wherein the elemental treatment volumes are smaller than the volume of tissue at the treatment site and are distributed both vertically and horizontally relative to each other at the periphery of the volume of tissue.   
     
     
         16 . The system of  claim 15 , wherein HIFU energy is distributed in multiple doses in a trajectory over or along a perimeter of each elemental treatment volume, with repeated passes of the focal zone of the HIFU transducer in the same trajectory over or along the perimeter of each elemental treatment volume 
     
     
         17 . The system of  claim 15 , wherein the horizontal and vertical distribution of the elemental treatment volumes relative to each other at the periphery of the volume of tissue produces a shell of treated tissue around an interior space of the volume of tissue. 
     
     
         18 . The system of  claim 17 , wherein some or all of the tissue within a center of the shell of treated tissue necroses due to heat conduction from when the shell is being produced. 
     
     
         19 . The system of  claim 15 , further comprising a mechanical wobbler that steers the focal zone of the HIFU treatment signals over or along the perimeter of each elemental treatment volume at a rate that confines heat conduction within a center of each elemental treatment volume as the elemental treatment volumes are being created. 
     
     
         20 . The system of  claim 15 , further comprising an electronic beam steerer that steers the focal zone of the HIFU treatment signals over or along the perimeter of each elemental treatment volume at a rate that confines heat conduction within a center of each elemental treatment volume as the elemental treatment volumes are being created.