WO2009001297A1

WO2009001297A1 - Method and apparatus for steering ultrasound therapy beam

Info

Publication number: WO2009001297A1
Application number: PCT/IB2008/052516
Authority: WO
Inventors: Balasundara Raju; Christopher Stephen Hall; Chien Ting Chin; William Tao Shi
Original assignee: Koninklijke Philips Electronics, N.V.
Priority date: 2007-06-28
Filing date: 2008-06-24
Publication date: 2008-12-31

Abstract

An apparatus and methodology for medically treating at least one region of interest of a patient is disclosed utilizing an ultrasound therapy array transducer for generating a therapy beam of given amplitude at one or more focal point locations of the at least one region of interest; a memory storage device for storing information regarding transducer beam amplitude as a function of focal point location of the beams, the device including a processor for computing beam amplitudes as a function of focal location in real time; a positioning system that is connected to the transducer for translating or rotating the position of the transducer, the positioning system being capable of changing the position of the transducer by utilizing electronic beam steering and/or mechanical re-positioning; a controller for determining whether mechanical repositioning of the transducer is needed, the controller being connected to the positioning system and being capable of causing translation or rotation of the transducer position; a user interface that couples to the controller, the user interface being capable of receiving input from the user of the desired size, shape and location of the at least one region of interest; and optionally a signaling device connected to the controller for indicating to the user that mechanical re -positioning of the transducer is needed.

Description

METHOD AND APPARATUS FOR STEERING ULTRASOUND THERAPY BEAM

[0001] The present disclosure relates to an apparatus and method for medically treating a region of interest of a patient utilizing an ultrasound therapy transducer array, the transducer being connected to a positioning system, which is connected to a controller, so that the position of the transducer can be mechanically repositioned as well as by utilizing electronic beam steering.

[0002] Ultrasound is quickly becoming a desirable approach for specific therapeutic interventions. In particular, the use of high intensity focused ultrasound is currently being used as an approach for thermal therapeutic intervention for uterine fibroids and has been examined for possible uses in the treatment of liver, brain, and other cancerous lesions. In addition, ultrasound has also been the subject of much research as a means of mediating clot dissolution (sonothrombolysis), drug delivery, and gene therapy. Ultrasound has also been shown to increase the efficacy of existing medical treatments such as the use of tPA in clot dissolution, genetic expression of proteins in gene therapy, and increased delivery of drugs in site -targeted therapies. The use of ultrasound in all of these applications is desirable because it allows the non- invasive treatment of deep tissues with little or no effect on overlying organs.

[0003] Ultrasound therapy transducers might be single element transducers that are mechanically positioned by the user prior to the start of therapy, or an electronically steered array that can direct acoustic energy at specific tissues. These transducers might have a natural focus that focuses the energy at a specified distance. Solely, neither of these methods is optimal for ultrasound therapy.

[0004] Electronic steering using array transducers is preferred as there is no physical movement of the transducer and such steering technique is relatively fast. However, electronic steering suffers from a loss of energy due to increased f-number when focusing away from the axis. This loss is further compounded when the array has small element count leading to the appearance of secondary lobes (grating lobes). The level of the unwanted grating lobe is generally dependent on the angle of steering from the transducer's axis and the frequency of operation. In such situations mechanical adjustment of the therapy probe is preferred. In some situations, several focal zones might be specified or the therapy region might be large, warranting mechanical re-positioning of the transducer.

[0005] Previously, positioning of ultrasound therapy transducers has been discussed, but such positioning discussions are solely for the purpose of initial adjustment or placement of the therapy transducer. [C. Rome, F. Couillaud, C. Moonen, "Spatial and temporal control of expression of therapeutic genes using heat shock proteins", Methods, 35, pp. 188-198, 2005.]

[0006] The disclosed apparatus and methodology offer improvements in the positioning/repositioning of ultrasound therapy transducer arrays. These and other structural and functional benefits of the disclosed apparatus and methodology will be apparent from the description which follows.

[0007] According to the present disclosure, an apparatus and methodology are disclosed for treating at least one region of interest of a patient utilizing an ultrasound therapy array transducer. In exemplary aspects, the disclosed apparatus and methodology are effective for medical and/or therapeutic treatments. Thus, the disclosed apparatus/methodology are generally effective for generating a therapy beam of given amplitude at one or more focal point locations associated with at least one region of interest. The disclosed apparatus/methodology generally includes a memory storage device for storing information regarding transducer beam amplitude as a function of focal point location of the beams and a processor for computing beam amplitudes as a function of focal location in real time. In an alternative implementation of the disclosed apparatus/methodology, a look up table with the beam amplitudes as a function of focus location is provided to facilitate operations thereof.

[0008] According to the present disclosure, a positioning system is also provided, such positioning system being connected to a transducer for translating or rotating the position of the transducer. The positioning system is generally capable of changing the location of ultrasound focal points by utilizing electronic beam steering and/or mechanical repositioning of the transducer. A controller is also generally provided, such controller being adapted to determine whether mechanical repositioning of the transducer is needed. The controller is thus connected to the positioning system and is capable of causing translation and/or rotation of the transducer, thereby altering the position thereof. A user interface is generally provided that couples to the controller. The user interface is typically capable of receiving input from the user, e.g., input concerning the desired size, shape and/or location of the region(s) of interest. The disclosed apparatus/methodology may optionally include a signaling device connected to the controller for indicating to the user that repositioning (e.g., mechanical repositioning) of the transducer is needed. [0009] Thus, in exemplary aspects of the present disclosure, an apparatus for medically treating at least one region of interest of a patient is advantageously provided, such apparatus having an ultrasound therapy array transducer for generating and delivering a therapy beam of given amplitude at one or more focal point locations of the at least one region of interest, a memory storage device for storing information regarding transducer beam amplitude as a function of focal point location of the beams, a processor in communication with the memory storage for computing beam amplitudes as a function of focal location, a positioning system that is connected to the transducer for translating and/or rotating the position of the transducer, the positioning system being capable of changing the position of the transducer by utilizing electronic beam steering and/or mechanical repositioning, a controller for determining whether mechanical repositioning of the transducer is needed, the controller being connected to the positioning system and being capable of causing translation and/or rotation of the transducer position, a user interface that couples to the controller, the user interface being capable of receiving input from the user, e.g., input concerning the desired size, shape and/or location of the at least one region of interest, and optionally a signaling device connected to the controller for indicating to the user that mechanical repositioning of the transducer is needed.

[0010] Of note, the computation of beam amplitudes as a function of focal location may be undertaken in real time, although such real time processing may be not be necessary and/or implemented in exemplary aspects of the present disclosure.

[0011] Exemplary aspects of the present disclosure provide numerous additional structures and/or perform additional advantageous functions, such additional structures and/or functions satisfying additional objects hereof. [0012] Thus, it is an aspect of the present disclosure to provide an apparatus wherein the controller comprises, in whole or in part, digital electronic circuitry.

[0013] Another aspect of the present disclosure is to provide an apparatus wherein the signaling device is selected from the group consisting of an audio speaker that outputs a desired audio signal (e.g., a beep sound), a visual device that outputs a visual cue, and combinations thereof.

[0014] Another aspect of the present disclosure is to provide an apparatus wherein the memory storage device includes one or more memory chips.

[0015] Another aspect of the present disclosure is to provide an apparatus wherein the user interface is part of or otherwise interacts with a video display associated with the disclosed apparatus.

[0016] In further exemplary aspects of the present disclosure, a method for treating at least one region of interest of a patient is provided, such method including the step of providing an apparatus for treating the at least one region of interest of the patient (e.g., medically and/or therapeutically treating such region of interest), the apparatus having an ultrasound therapy array transducer for generating and delivering a beam of given amplitude at one or more focal point locations of the at least one region of interest, a memory storage device for storing information regarding transducer beam amplitude as a function of focal point location of the beams, and a processor in communication with the memory storage device, the processor being adapted to compute beam amplitudes as a function of focal location, e.g., in real time, if desired. The apparatus also having a positioning system that is coupled or connected to the transducer for translating and/or rotating the position of the transducer, the positioning system being capable of changing the position of the transducer by utilizing electronic beam steering and/or mechanical repositioning, a controller for determining whether mechanical repositioning of the transducer is needed, the controller being connected to the positioning system and being capable of causing translation and/or rotation of the transducer position, a user interface that couples to the controller, the user interface being capable of receiving input from the user, e.g., input of the desired size, shape and location of the at least one region of interest, and optionally, a signaling device coupled or connected to the controller for indicating to a user that mechanical repositioning of the transducer is needed. The method, according to an aspect of the present disclosure, also including the steps of initially positioning the transducer for delivery of the treatment to the at least one region of interest based on prior acquired image data of the at least one region of interest, and causing the apparatus to provide transducer-based treatment to the at least one region of interest.

[0017] Additional features of the present disclosure are realized through exemplary aspects and/or implementations of the disclosed methodology.

[0018] Thus, it is an aspect of the present disclosure to provide a method wherein the controller has, in whole or in part, digital electronic circuitry.

[0019] Another aspect of the present disclosure is to provide a method wherein the signaling device is selected from the group consisting of an audio speaker that outputs a desired audio signal (e.g., a beep sound), a visual device that outputs a visual cue, and combinations thereof.

[0020] Another aspect of the present disclosure is to provide a method wherein the memory storage device includes one or more memory chips. [0021] Another aspect of the present disclosure is to provide a method wherein the user interface is part of or otherwise interacts with a video display associated with the disclosed apparatus.

[0022] Another aspect of the present disclosure is to provide a method wherein the initial positioning of the transducer is effectuated, in whole or in part, by the controller.

[0023] Another aspect of the present disclosure is to provide a method wherein the initial positioning of the transducer is effectuated, in whole or in part, by the user.

[0024] Another aspect of the present disclosure is to provide a method wherein the initial positioning of the transducer is effectuated, in whole or in part, by the user utilizing the user interface. In exemplary aspects thereof, the user interface and/or associated monitor are capable of depicting the contours of the transducer beam amplitude and ratio of grating lobe to main lobe amplitude as a function of focal location. Such contour depiction may be advantageously overlaid on the image data for the at least one region of interest.

[0025] These aspects and other features are explained in more detail with reference to the examples and the figures herein below.

[0026] To assist those of ordinary skill in the art in making and using the disclosed apparatus and method, reference is made to the accompanying figures, wherein:

[0027] Figure 1 shows an exemplary focal spot amplitude as a function of lateral location in a plane 6 cm away from an aperture. The values are normalized by dividing (for each case) the value of the amplitude when the beam was focused on axis. The number of elements in the array is shown in the legend. [0028] Figure 2 shows an exemplary ratio of the main lobe (at focus) amplitude to the grating lobe amplitude as a function of the focal spot location for two array designs.

[0029] The present disclosure provides advantageous apparatus and method(s) for treating a region of interest of a patient utilizing an ultrasound transducer array. The disclosed ultrasound transducer array is connected to a positioning system which is in turn connected to a controller, so that the position of the transducer array can be mechanically repositioned as well as by utilizing electronic beam steering.

[0030] Figure 1 and Figure 2 illustrate the problems of prior apparatus and methodology for treating patients' regions of interest using ultrasound therapy transducers. Four array transducers were studied in this illustration. The aperture size was 4 cm square and the excitation was 1.2 MHz. The four cases corresponded to: (1) an array with λ/2 spacing of 4096 (64 x 64) square elements, (2) an array with λ spacing of 1024 (32 x 32) square elements; (3) an array with 2λ spacing of 256 (16 x 16) square elements; and (4) a random array with 256 circular elements of diameter 2.10 mm each. The beam patterns from these arrays at a plane 6 cm from the aperture were simulated.

[0031] Figure 1 shows that the focal spot amplitude (i.e., intensity) decreases as the beam is electronically steered away from the axis. This decline happens even when the array has a large number of elements with a spacing of λ/2 and is attributed to larger f-numbers for off- axis steering. The decline is greater when the element count is made lower than that required for λ/2 spacing, owing to the appearance of grating lobes. In such cases, the power to be delivered by driving electronics must be increased to compensate for loss of energy associated with off- axis steering. Thus, the off-axis steering capability is limited by how much the driving electronics could be made to handle.

[0032] Another issue is the minimization of unwanted energies in grating lobes when the element count is small. For example, with 256 elements (see plot 3), the grating lobe levels (Figure 2) could be significant, especially for off-axis steering. Randomization (see plot 1) decreases the grating lobe level, but not for wide steering angles. If the acceptable grating lobe level is 15 dB (or below) the main lobe, then only a steering of up to 2 cm can be done from the axis in the example case illustrated here.

[0033] The apparatus and methodology according to the disclosure hereof utilizes an ultrasound therapy array transducer with more than one element arranged either in a periodic or random manner over an aperture.

[0034] The apparatus and methodology according to the present disclosure generally utilize an ultrasound array transducer with more than one element arranged either in a periodic or random manner over the aperture, a controller that is adapted to determine whether mechanical movement of the transducer is warranted, a signaling device (e.g., device adapted to generate audio beep, visual cue, etc.) to indicate that mechanical repositioning is necessary (optional), a positioning system that is connected to the controller, such positioning system being adapted to translate and/or rotate the transducer, if needed, a memory storage device that is adapted to store information regarding the beam amplitudes as a function of focal locations (e.g., as a look-up table) and/or communicate with a processor that is adapted to compute beam amplitudes as a function of focal locations, and a user interface that couples to the controller that is adapted to facilitate user input of relevant information, e.g., the desired size, shape and/or location of desired therapy region(s).

[0035] Of note, the user interface may be adapted to interact or otherwise communicate with a display device such as, e.g., a monitor that is adapted to depict, inter alia, contours of acoustic amplitudes. Such display device may further be adapted to overlay them on image data obtained from ultrasound imaging systems, CT, or other modalities.

[0036] Several exemplary aspects of the systems and methods of the present disclosure follow:

Example A

[0037] In one aspect, the user moves the transducer under manual control for initial positioning. This operation can be aided by image data from ultrasound scanners or other imaging modalities. The user then selects regions of interest (ROIs) for applying therapy. The controller receives this input about the ROIs and then loads the beam characteristics for the focal spots from the memory storage unit. If focal energy is below certain threshold, and/or if the unwanted grating lobes are above a certain threshold, then the system determines the minimal amount needed to translate or rotate the transducer in order to ensure the therapy parameters are within required limits. It then optionally sends a cue (audio or visual) to the user that there is mechanical adjustment, and then sends a command to the positioning system of the ultrasound transducer to move appropriately. If on the other hand, the focal energy levels and unwanted grating lobe levels are within preferred limits, then no mechanical movement is done and electronic steering of the therapy beam is done. The exact movement order will be optimized for minimizing side effects, maximizing efficiency of treatment, and increasing beneficial outcomes or some combination of the above.

Example B

[0038] An interface communicates with a monitor or the like (e.g., a screen) to show contours of the beam amplitudes for several focal regions overlaid on the image data. Similarly, contour data can be shown for amplitude of grating lobes (as ratio of main lobe level) as a function of focal location. The user then manually adjusts the position of the therapy transducer in order to ensure that the appropriate energy levels can be delivered without effects at unintended locations. In this aspect, a human user plays the role of the controller.

Example C

[0039] Similar to exemplary Example A, except that the initial positioning is done by the controller rather than manual control by the user. The controller can place the transducer such that the axis passes through the centroid of the ROIs.

[0040] The controller can be implemented using any digital electronic circuitry, including a digital signal processor (DSP), field programmable gate array (FPGA), etc. The signaling device can be implemented as an audio speaker that outputs an audio signal, e.g., a beep sound, or as a visual device that outputs a visual cue (e.g., text output, icon change, and the like on a display). The memory storage device can be implemented as one or more memory chips. The user interface can be implemented as part of the video display for the overall therapy system.

[0041] The disclosed apparatus and methods have wide ranging applicability. For example, the apparatus and methods of the present disclosure can, for example, be used for (i) ultrasound mediated drug delivery; (ii) ultrasound mediated gene delivery; (iii) ultrasound directed thermal therapies; (iv) high intensity focused ultrasound ablation; and/or (v) sonothrombolysis (e.g. ischemic cardiac and stroke therapies).

[0042] Of note, sonothrombolysis with microbubble destruction for treating atrial or coronary clots would require therapy beam steering in order to precisely position the therapy beam to avoid exposure to unwanted regions. Future sonothrombolysis treatments for stroke victims or DVT patients could involve localization of therapy using information from ultrasound imaging such as presence of microbubble accumulation around a clot in a specific region, or from MR imaging. In such cases, therapy beam steering would be necessary.

[0043] While the apparatus and methods of the present disclosure have been described with respect to specific aspects thereof, it will be recognized by those of ordinary skill in the art that many modifications, enhancements, and/or changes can be achieved without departing from the spirit and scope hereof. Therefore, it is manifestly intended that the present disclosure not be limited except perhaps by the scope of the claims and equivalents thereof.

Claims

What is claimed is:

1) An apparatus for medically treating at least one region of interest of a subject, comprising: an ultrasound transducer array for generating and delivering a therapy beam of given amplitude at one or more focal point locations of at least one region of interest; means for establishing one or more beam amplitudes as a function of at least one focal location; a positioning system for positioning the transducer, the positioning system being capable of changing the position of ultrasound focal points; a controller for, as needed, cooperating with the positioning system to position the transducer; and a user interface for, as needed, cooperating with the controller to receive input from a user.

2) The apparatus of claim 1 , further comprising a signaling device for cooperating with the controller to indicate to the user that re -positioning of the transducer is needed.

3) The apparatus of claim 1, wherein the means for establishing beam amplitudes as a function of focal location includes a memory storage device and a processor for computing beam amplitudes as a function of focal location.

4) The apparatus of claim 1, wherein the processor computes beam profiles in real time.

5) The apparatus of claim 1, wherein the user input includes a desired size, shape and/or location of the at least one region of interest. 6) The apparatus of claim 1 , wherein the controller utilizes digital electronic circuitry.

7) The apparatus of claim 2, wherein the signaling device produces audio and/or visual signals.

8) The apparatus of claim 3, wherein the memory storage device is a memory chip.

9) The apparatus of claim 1 , wherein the user interface includes a video display operatively associated with the apparatus.

10) The apparatus of claim 1, where the ultrasound transducer array has elements that are distributed either periodically or in a random manner over an aperture.

11)A method of medically treating at least one region of interest of a subject, comprising the steps of: providing an apparatus for treating the at least one region of interest, the apparatus having an ultrasound therapy array transducer for generating and delivering a beam of given amplitude at one or more focal point locations of the at least one region of interest, means for establishing one or more beam amplitudes as a function of focal location, a positioning system for positioning the transducer via electronic beam steering and/or mechanical repositioning, a controller for, as needed, cooperating with the positioning system to position the transducer, and a user interface for receiving input from a user; initially positioning the transducer for delivery of treatment to the at least one region of interest based on prior acquired image data of the at least one region of interest; and causing the apparatus to provide treatment to the at least one region of interest. 12) The method of claim 11, wherein the apparatus for cooperating with the controller to indicate to the user that re-positioning of the transducer is needed.

13) The method of claim 11, wherein the user input includes a desired size, shape and/or location of the at least one region of interest.

14) The method of claim 11 , wherein the initial positioning of the transducer is effectuated by the controller.

15) The method of claim 11 , wherein the initial positioning of the transducer is effectuated by the user.

16) The method of claim 11 , wherein the initial positioning of the transducer is done by the user via the user interface, the interface being capable of depicting the contours of the transducer therapy beam amplitude and ratio of grating lobe to main lobe amplitude as a function of focal location overlaid on the image data for the at least one region of interest.