Method for using high intensity focused ultrasound and associated systems and devices

Abstract

A plurality of concepts related to HIFU therapy are disclosed, including a technique to spatially track and display the relative positions of a HIFU focal point and an imaging plane from an ultrasound imager, so that a clinician can ensure that the HIFU focus remains in the image plane during HIFU therapy, thereby facilitating image guided HIFU therapy. Also disclosed are a plurality of transvaginal probes that include a HIFU transducer optimized for the treatment of uterine fibroids. In one embodiment, the probe includes a piezoceramic crystal bonded to an aluminum lens, to achieve a HIFU transducer having a focal length of about 4 cm. In another embodiment, the probe includes a generally spoon-shaped transducer including a plurality of individual emitter elements. Still another concept disclosed herein is a method for evaluating a quality of a coupling between a liquid-filled volume encompassing a HIFU transducer and a tissue interface.

The invention in which an exclusive right is claimed is defined by the following: 
     
         1 . A probe for administering ultrasound therapy to a treatment site within a patient's body, wherein a tissue mass is disposed between the probe and the treatment site, comprising:
 (a) an elongate supporting structure having a distal end and a proximal end, said elongate supporting structure including a section at its proximal end that is adapted to be grasped and manipulated by a clinician to at least initially position the distal end of the elongate supporting structure at a desired location generally adjacent to the tissue mass;   (b) a high intensity focused ultrasound (HIFU) transducer disposed at the distal end of the elongate supporting structure, said HIFU transducer having an aperture through which HIFU waves are transmitted, said aperture being of a sufficient size to transmit therapeutic HIFU waves, so that the therapeutic HIFU waves have sufficient intensity remaining upon reaching the treatment site after being attenuated by their passage through the tissue mass, to achieve a desired therapeutic effect, without substantially damaging a portion of the tissue mass through which the therapeutic HIFU waves initially propagate toward the treatment site; and   (c) a light based imaging element configured to enable an interface between a flexible membrane substantially encapsulating the distal end of the elongate supporting structure and the tissue mass, to determine whether any air bubbles are present at the interface, the flexible membrane being configured to be inflated with a liquid to a desired extent when the distal end of the elongate supporting structure is disposed adjacent to the tissue mass, such that the flexible membrane will substantially conform to the tissue mass, thereby ultrasonically coupling the HIFU transducer to the tissue mass.   
     
     
         2 . The probe of  claim 1 , wherein the imaging element comprises an optical imaging element. 
     
     
         3 . The probe of  claim 2 , wherein the optical imaging element comprises an optical fiber. 
     
     
         4 . The probe of  claim 1 , wherein the imaging element comprises a digital imaging device. 
     
     
         5 . The probe of  claim 1 , wherein the HIFU transducer comprises an air backed piezoceramic crystal coupled to an aluminum lens element. 
     
     
         6 . The probe of  claim 1 , wherein the HIFU transducer comprises a generally spooned-shaped transducer including a plurality of discrete emitter elements, each emitter element having a substantially equivalent area. 
     
     
         7 . The probe of  claim 1 , further comprising a liquid flush line configured to discharge an irrigation liquid proximate the distal end of the elongate supporting structure, to dislodge any air bubbles proximate the distal end of the elongate supporting structure that could interfere with the HIFU beam provided by the HIFU transducer. 
     
     
         8 . A probe for administering ultrasound therapy to a treatment site within a patient's body, wherein a tissue mass is disposed between the probe and the treatment site, comprising:
 (a) an elongate supporting structure having a distal end and a proximal end, said elongate supporting structure including a section at its proximal end that is adapted to be grasped and manipulated by a clinician to at least initially position the distal end of the elongate supporting structure at a desired location generally adjacent to the tissue mass; and   (b) a high intensity focused ultrasound (HIFU) transducer disposed at the distal end of the elongate supporting structure, said HIFU transducer having an aperture through which HIFU waves are transmitted, said aperture being of a sufficient size to transmit therapeutic HIFU waves, so that the therapeutic HIFU waves have sufficient intensity remaining upon reaching the treatment site after being attenuated by their passage through the tissue mass, to achieve a desired therapeutic effect, without substantially damaging a portion of the tissue mass through which the therapeutic HIFU waves initially propagate toward the treatment site, the HIFU transducer comprising at least one of the following:
 (i) an air backed piezoceramic crystal coupled to an aluminum lens element; and 
 (ii) a generally spooned-shaped transducer comprising a plurality of discrete emitter elements, each emitter element having a substantially equivalent area. 
   
     
     
         9 . The probe of  claim 8 , further comprising a light based imaging element configured to enable an interface between a flexible membrane substantially encapsulating the distal end of the elongate supporting structure and a tissue mass to be examined, to determine whether any air bubbles are present at the interface, the flexible membrane being configured to be inflated with a liquid to a desired extent when the distal end of the elongate supporting structure is disposed adjacent to the tissue mass, such that the flexible membrane will substantially conform to the tissue mass, thereby ultrasonically coupling the HIFU transducer to the tissue mass. 
     
     
         10 . The probe of  claim 8 , wherein the imaging element comprises an optical fiber. 
     
     
         11 . The probe of  claim 8 , wherein the imaging element comprises a digital imaging device. 
     
     
         12 . A system for image guided high intensity focused ultrasound (HIFU) therapy comprising:
 (a) an ultrasound imaging probe;   (b) a first display upon which a first image generated by the ultrasound imaging probe is to be displayed;   (c) a therapy probe including a HIFU transducer;   (d) a processor configured to:
 track a spatial relationship and orientation between the ultrasound imaging probe and the therapy probe; and 
 (ii) provide a signal configured to produce a second image indicating the spatial relationship and orientation between the ultrasound imaging probe and the therapy probe; and 
   (e) a second display on which the second image indicating the spatial relationship and orientation between the ultrasound imaging probe and the therapy probe is displayed, the second image providing feedback that a clinician can use to maintain a desired spatial relationship and orientation between the ultrasound imaging probe and the therapy probe.   
     
     
         13 . The system of  claim 12 , wherein the first display and the second display are implemented as a single display on which the first image and second image are simultaneously displayed.