DEVICE FOR POSITIONING AN ULTRASOUND TRANSDUCER INSIDE A MR SCANNER
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.
This application is a continuation of U.S. application Ser. No. 12/296,769 filed Oct. 10, 2008, now U.S. Pat. No. ______, which is a US National Stage Entry of PCT/US2007/064184 filed Mar. 16, 2007, which claims the benefit of U.S. Provisional Application Ser. No. 60/744,605 filed Apr. 11, 2006.
DESCRIPTIONThe following relates to medical imaging systems. It finds particular application to facilitating the positioning of an ultrasound transducer inside a Magnetic Resonance (MR) scanner, but is also applicable to other medical imaging modalities.
High intensity focused ultrasound (HIFU) is used to treat tumors, especially uterine fibroids. The treatment is based on warming tissue in and/or near the focus of the ultrasound beam. Sufficient warming causes cell death and subsequently a lesion in the treated volume, which often includes the tumor and some margin of healthy tissue immediately adjacent. The body then slowly absorbs the lesion, leaving the treated area tumor-free.
To achieve the foregoing, the ultrasound transducer needs to be able to be moved in a manner that focuses the beam at a desired location on the subject while avoiding exposing organs. For suitable movement, at least two translational and two angular degrees of freedom are needed. Controlling the location and extent of the warming can be facilitated via feedback from a device that can visualize both the anatomy of the treatment area and the temperature profile generated. A MR scanner can perform both functions by running dedicated sequences.
The temperature profile is obtained by locally measuring the magnetic resonance frequency of the protons in the subject. The frequency has a temperature factor that is relatively small being only one millionth of one percent per degree Celsius. The mechanisms for moving the transducer therefore are made of materials that are non-magnetic. Small amounts of any metal can be used, however, plastics and/or ceramics are mainly used. In addition the motors for powering the movements typically are placed about one meter away or more. At the same time the precision of the system is about 0.5 mm or better. This makes the system critical with respect to mechanical slack and bending.
Conventional treatment systems use positioning devices that focus the high intensity ultrasound on tissue to be treated. The transducer typically is held by a structure shaped similar to a fork that is rotated about a central axis. As a consequence, one side of the transducer is lifted while the other side of the transducer is lowered. This swiveling about the axis when lifting one side of the transducer during focusing creates problems when the transducer is to be placed relatively close to the subject, and such close positioning is often crucial when treating different size patients with tumors located at different depths. In order to make the fork stiff translation in the up-down direction is typically sacrificed, limiting the range of movements.
In one aspect, a device that positions an ultrasound transducer for ultrasound therapy to focus a treatment beam emitted by the ultrasound transducer at tissue of interest is illustrated. The device includes at least three anchors which support the ultrasound transducer and at least three extendable structures, each with a coupling that supports a corresponding one of the at least three anchors. A drive mechanism 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.
One advantage includes facilitating positioning an ultrasound transducer for a high intensity focused ultrasound treatment.
Another advantage lies in freely translating the ultrasound transducer in all directions and independently inclined around two directions.
Another advantage includes translating and inclining members with minimum length relative to the amplitudes of the movements, and these members are mechanically stressed only in the lengthwise directions to minimize the amount of transducer displacement caused by elastic deformation in its suspension.
Another advantage is the translating and inclining members are made using a small amount of material to minimize their influence on the magnetic field inside the subject and on a temperature measurement.
Another advantage resides in using medical imaging to facilitate focusing the beam of the ultrasound transducer at a region of interest.
Still further advantages will become apparent to those of ordinary skill in the art upon reading and understanding the detailed description of the preferred embodiments.
The drawings are only for purposes of illustrating embodiments and are not to be construed as limiting the claims.
The device 16 includes a receptacle or frame 18, which supports the ultrasound transducer 14. The receptacle 18 has anchors 201, 202, . . . , 20N (collectively referred to herein as anchors 20), wherein N is a positive integer. Each of the anchors 201, 202, . . . , 20N is respectively supported by couplings 221, 222, . . . , 22N (collectively referred to herein as couplings 22). Each of the couplings 221, 222, . . . , 22N respectively reside at an end of extendible structures 241, 242, . . . , 24N (collectively referred to herein as extendible structures 24). The extendible structures 24 are moveably attached to a support plate 26 and extend and retract from the subject along a first axis 28. The couplings 22 allow the anchors 20 to translate and/or rotate therein when one or more of the extendible structures 24 extends or retracts. As the anchors 20 translate and/or rotate within their respective couplings 22, the receptacle 18 translates and/or rotates towards or away from the subject and, hence, the transducer 14 translates and/or rotates towards or away from the subject.
By way of example,
In the mode of motion illustrated in
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The receptacle 18, the anchors 20, the couplings 22, the extendible structures 24, the support plate 26, the axial motion mechanism 40 and the longitudinal motion mechanism 46 reside within a cavity of a container or shell 50. Controls 52 are used to drive the extendible structures 24, the axial motion mechanism 40 and the longitudinal motion mechanism 46 in order to focus the ultrasound beam 12. The controls 52 can include mechanical components for manually focusing the beam 12 and/or electrical components for electrically focusing the beam 12.
The device 16 is used in conjunction with a scanning system 54 or other device that is capable of providing information about tissue and/or temperature profiles associated with the treatment area. Such information is used to facilitate positioning the receptacle 18 to focus the ultrasound beam 12. As illustrated in
In this example, the scanning system 54 includes two main magnets 56 (e.g., permanent or resistive) separated by an imaging region 58 in an open configuration. A support mechanism 60 is used to position the subject within the imaging region 58. As depicted, the device 16 resides within the support mechanism 60. The positioning of the two main magnets 56 is such that the magnets generate a magnetic field (B0) in the subject. Magnetic field gradient coils (not shown, typically housed in or adjacent the main magnets) are arranged to superimpose selected magnetic field gradients on B0. Such gradients include orthogonal magnetic field gradients such as x, y and/or z gradients defined within a Cartesian plane. One or more radio frequency coils (not shown, typically disposed between the gradient coils and the subject) inject radio frequency excitation pulses (B1) into and/or receive resonance signals from the imaging region 58.
A console 62 and a display 64 are used to plan patient procedures (e.g., selecting imaging protocol(s), set imaging parameters, etc.), commence scanning, present reconstructed images, as well as various other features. The console 62 provides instructions to a scanner controller 66 that controls a gradient controller 68, a radio frequency (RF) source 70, and a receiver 72. The gradient controller 68 controls the magnetic field gradient coils to spatially encode the resulting magnetic resonances. The RF source 70 generates and provides the radio frequency excitation pulses (B1) to the one or more radio frequency coils. During a readout phase, detection circuitry (not shown) detects the magnetic resonance signals, and the receiver 72 receives the spatially encoded magnetic resonances. The acquired spatially encoded magnetic resonances are stored in a storage component 74 and/or provided to a processing component 76, which reconstructs one or more images from the data. Raw and/or processed data (e.g., images) are displayed at the display 64, archived, filmed, conveyed for further processing, etc.
The acquired data and/or resulting images are used to focus the beam 12 on at the region of interest, which is optionally controlled from the console 62 through transducer beam power and control electronics 63 and/or motor power and control electronics 65. For example, the data and/or images provide numerical and/or graphical information about the region of interest such as the images of the treatment tissue and temperature profiles associated therewith. Thus, the data allows the operator to see the area that is being exposed to the beam 12. The operator can then, if needed, use the console 62 to control the electronics 63 and/or 65 to drive the controls 52 to reposition the receptacle 18 via one or more of the five degrees of freedom described herein to move the transducer 14 and refine the focus position of the beam 12. In one embodiment, the ultrasound beam and/or its focal spot are superimposed on the displayed image, e.g. in phantom, with a color change or shift, or the like. This provides the operator with visual feedback as the transducer is positioned. For example, the superimposed images can provide assurance that the focal spot is centered in the target tumor and that no vital or sensitive organs lie in the ultra sound beam.
Now referring to
As illustrated in
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It is to be appreciated that the components of the device 26 can be designed for use inside a MR or other type of medical imaging scanner. In addition, the components can be constructed from available or readily manufactured from non-magnetic materials.
At reference numeral 130, the device 16 suitably positions the ultrasound transducer 14 to an initial position for treating a particular region in the subject. The ultrasound transducer 14 is activated and an ultrasound beam 12 is directed into the subject. At 132, the imaging system 54 is used to collect data representative of tissue in the treatment region and a temperature profile of the treatment region. Optionally, the temperature profiles are superimposed on the displayed image, e.g. by temperature depending shading. At 134, the operator determines from the data whether the position of the ultrasound transducer should be refined to further focus the beam at the treatment area. Assuming the operator desires to refine the position of the ultrasound transducer, at 136, the operator uses the controls 52 to extend or retract one or more of the extendible structures 24, as describe above, for example, through the arm and wheel system 100. Such movement results in translation and/or rotational movement of the beam to move the focus depth of the beam. Optionally, the operator uses the controls 52 to move the support 26 in a transverse and/or longitudinal direction with respect to the patient to move the beam to move a different transverse and/or longitudinal location.
The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims
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 (B0) 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 B0, the magnetic field gradient coils being controlled by a gradient controller;
- one or more radio frequency coils configured to inject radio frequency excitation pulses (B1) 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.
Type: Application
Filed: Dec 2, 2016
Publication Date: Mar 23, 2017
Inventors: Matti Lindstrom (Espoo), Gosta Ehnholm (Helsinki)
Application Number: 15/367,508