Device for positioning an ultrasound transducer inside a mr scanner

Abstract

A device positions an ultrasound transducer for ultrasound therapy to focus a treatment beam emitted by the ultrasound transducer at tissue of interest. The device includes at least three anchors which support the ultrasound transducer. The device further includes at least three extendable structures, each with a coupling that supports a corresponding one of the at least three anchors. A drive mechanism of the device independently drives each of the at least three extendable structures towards or away from a subject to move the ultrasound transducer within at least three degrees of freedom.

1 . A medical treatment system comprising:
 a medical imaging scanner configured to generate diagnostic images of a region of interest of a subject in an imaging region including generating a magnetic field in the imaging region ;   a subject support configured to support the subject with the region of interest in the imaging region;   an ultrasonic transducer configured to emit a focused ultrasound beam to treat target tissue in the region of interest, the ultrasound transducer being disposed in the magnetic field; and   a non-ferromagnetic mechanical drive mechanism configured to mechanically position the ultrasonic transducer with five degrees of freedom, the non-ferromagnetic mechanical drive mechanism being disposed in the magnetic field.   
     
     
         2 . A medical treatment system as set forth in  claim 1  wherein the medical imaging system further includes:
 a main magnet configured to generate a magnetic field (B 0 ) in the subject residing within an imaging region of the medical imaging scanner; 
 magnetic field gradient coils configured to superimpose selected magnetic field gradients on B 0 , the magnetic field gradient coils being controlled by a gradient controller; 
 one or more radio frequency coils configured to inject radio frequency excitation pulses (B 1 ) produced by radio frequency (RF) source into the imaging region; 
 a receiver configured to receive spatially encoded magnetic resonances; 
 a console configured to control the medical imaging scanner and 
 a reconstruction processor programmed to reconstruct the received spatially encoded magnetic resonances into the diagnostic images and into a temperature profile; 
 a display on which the diagnostic images and the temperature profile are displayed. 
 
     
     
         3 . The medical treatment system as set forth in  claim 1 , the mechanical drive mechanism includes:
 three anchors supporting the ultrasound transducer;   three lead screws each with a coupling configured to couple to a respective one of the three anchors;   three lead screw nuts configured to rotate around a respective one of the lead screws to move the ultrasound transducer toward and away from the subject with three degrees of freedom; and   arm and wheel mechanisms configured to turn the lead screw nuts.   
     
     
         4 . The medical treatment system as set forth in  claim 2 , wherein the reconstruction processor is further configured to superimpose the temperature profile and a depiction of the ultrasound beam on the displayed diagnostic images. 
     
     
         5 . A method for positioning an ultrasound beam used to treat a target region of a subject with high intensity focused ultrasound (HIFU), including:
 initially positioning the ultrasound beam for treating the target region of the subject by moving an ultrasound transducer using at least five degrees of freedom ;   actuating the ultrasound transducer to commence treatment of the subject;   with an imaging scanner, capturing information representative of tissue in a region of interest that includes the target region and a temperature profile of the region of interest;   re-positioning the ultrasound beam based on the information by moving the ultrasound transducer using the at least five degrees of freedom; and   continuing the treatment.   
     
     
         6 . The method as set forth in  claim 5 , positioning the ultrasonic beam includes:
 translating an ultrasonic transducer with two degrees of freedom; and   moving the transducer towards and away from the region of interest with three degrees of freedom.   
     
     
         7 . The method as set forth in  claim 5 , wherein the five degrees of freedom include translational motion toward and away from the subject and two rotational motions. 
     
     
         8 . The method as set forth in  claim 5 , wherein moving the ultrasound transducer includes rotating threaded elements to extend and contract lead screws connected with the ultrasound transducer. 
     
     
         9 . The method as set forth in  claim 8 , wherein rotating the threaded elements is performed with arm and wheel mechanisms. 
     
     
         10 . The method as set forth in  claim 5 , wherein moving the ultrasound transducer is performed using a positioning device which includes at least three anchors which support the ultrasound transducer, three extensible lead screw and lead screw nut structures, each coupled with a coupling that supports a corresponding one of the at least three anchors, and arm and wheel mechanisms which independently rotate each of the lead screw nuts causing the lead screw to extend or retract. 
     
     
         11 . The method as claimed in  claim 5 , wherein the imaging scanner includes a magnetic resonance scanner which generates a magnetic field in the ultrasound transducer and a non-ferromagnetic drive mechanism which moves the ultrasound transducer using the at least five degrees of freedom is disposed in the magnetic field, the method further including:
 generating an image of the region of interest that includes the target region;   reconstructing the captured information into a temperature profile of the region of interest; and   displaying the image representation and the temperature profile on a display device.   
     
     
         12 . The method as set forth in  claim 11 , further including:
 superimposing the image representation and the temperature profile;   displaying the superimposed image representation and temperature profile on the display device.   
     
     
         13 . A system including:
 an ultrasonic transducer which emits a treatment beam; and   a device for positioning the ultrasonic transducer to focus the treatment beam emitted by the ultrasonic transducer at target tissue in a region of interest for an ultrasound therapy medical treatment, the device comprising:
 a support plate, 
 at least three anchors which support the ultrasound transducer, 
 at least extensible structures, each with a first coupling that rotatably supports a corresponding one of the at least three anchors and a second coupling that supports the corresponding extendible structures on the support plate, the extendible structures each including a lead screw and a lead screw nut, 
 a drive mechanism which includes arm and wheel mechanisms configured to turn each of the lead screw nuts to extend and retract the extendible structures toward or away from the subject, the drive mechanism independently moving the support plate in at least two orthogonal directions different from extension directions, such that the ultrasound transducer is moved with at least five degrees of freedom. 
   
     
     
         14 . A method of treating a target region of a subject with an ultrasound beam, the method including:
 with a medical imaging scanner, generating images of the region of interest; and   with the system as set forth in  claim 13 , positioning the transducer to direct the treatment beam at the target region.   
     
     
         15 . The method as set forth in  claim 14 , further including:
 with the medical imaging scanner, generating a temperature profile of the region of interest; and   on a display device, displaying the image representation and the temperature profile.