Abstract:
Methods and devices for manipulating an articulating arm of an ultrasound therapy system are provided. In one embodiment an articulating arm comprises a first articulating arm link, a second articulating arm link, a rotating joint configured to rotationally connect the first articulating arm link to the second articulating arm link so that the first and second articulating arm links are substantially perpendicular, and an arm limiter attached to the second articulating arm link, the arm limiter being configured to limit rotation of the second articulating arm link along the rotating joint with respect to the first articulating arm link. An ultrasound therapy transducer and imaging system can be mounted on the articulating arm. Methods for performing manipulating the arm and system are also provided.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. 119 of U.S. Provisional Patent Application No. 61/842,811, filed Jul. 3, 2013, titled “Articulating Arm Limiter for Cavitational Ultrasound Therapy System”, which application is incorporated herein by reference. 
     
    
     INCORPORATION BY REFERENCE 
       [0002]    All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. 
       FIELD 
       [0003]    This disclosure relates generally to support and positioning apparatuses for ultrasound therapy systems. More specifically, this disclosure relates to micromanipulator systems with improved control and safety over prior systems. 
       BACKGROUND 
       [0004]    Histotripsy and Lithotripsy are non-invasive tissue ablation modalities that focus pulsed ultrasound from outside the body to a target tissue inside the body. Histotripsy mechanically damages tissue through cavitation of micro bubbles which homogenizes cellular tissues into an a-cellular liquid that can be expelled or absorbed by the body, and Lithotripsy is typically used to fragment urinary stones with acoustic shockwaves. 
         [0005]    Histotripsy is the mechanical disruption via acoustic cavitation of a target tissue volume or tissue embedded inclusion as part of a surgical or other therapeutic procedure. Histotripsy works best when a whole set of acoustic and transducer scan parameters controlling the spatial extent of periodic cavitation events are within a rather narrow range. Small changes in any of the parameters can result in discontinuation of the ongoing process. 
         [0006]    Histotripsy requires high peak intensity acoustic pulses which in turn require large surface area focused transducers. These transducers are often very similar to the transducers used for Lithotripsy and often operate in the same frequency range. The primary difference is in how the devices are driven electrically. 
         [0007]    Histotripsy pulses consist of a (usually) small number of cycles of a sinusoidal driving voltage whereas Lithotripsy is (most usually) driven by a single high voltage pulse with the transducer responding at its natural frequencies. Even though the Lithotripsy pulse is only one cycle, its negative pressure phase length is equal to or greater than the entire length of the Histotripsy pulse, lasting tens of microseconds. This negative pressure phase allows generation and continual growth of the bubbles, resulting in bubbles of sizes up to 1 mm. The Lithotripsy pulses use the mechanical stress produced by a shockwave and these 1 mm bubbles to cause tissue damage or fractionate stones. 
         [0008]    In comparison, each negative and positive cycle of a Histotripsy pulse grows and collapses the bubbles, and the next cycle repeats the same process. The maximal sizes of bubbles reach approximately tens to hundreds of microns. These micron size bubbles interact with a tissue surface to mechanically damage tissue. 
         [0009]    In addition, Histotripsy delivers hundreds to thousands of pulses per second, i.e., 100-1 kHz pulse repetition frequency. Lithotripsy only works well within a narrow range of pulse repetition frequency (usually 0.5-1 Hz). Studies show that the efficacy and efficiency of lithotripsy decreases significantly when the pulse repetition frequency is increased to 10-100 Hz. The reduced efficiency is likely due to the increased number of mm size bubbles blocking the shock waves and other energy from reaching the stone. 
         [0010]    Histotripsy typically comprises delivering acoustic pulses that operate at a frequency between approximately 50 KHz and 5 MHz, having a pulse intensity with a peak negative pressure of approximately 8-40 MPa, a peak positive pressure of more than 10 MPa, a pulse length shorter than 50 cycles, a duty cycle between approximately 0.1% and 5% and in some embodiments less than 5%, and a pulse repetition frequency of less than 5 KHz. 
         [0011]    Diagnostic ultrasound can be used during Histotripsy procedures to visualize the surgical anatomy and monitor the process in real time. The Histotripsy cavitation bubble cloud can appear very clearly on diagnostic ultrasound as a hyperechoic (light) region and ablated homogenized tissue can appear as a hypoechoic (dark) region. Large and irregular tissue volumes can be ablated using Histotripsy by electronically changing the focus of a therapeutic array or by mechanically moving the focus of the therapeutic transducer within the surgical target area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which: 
           [0013]      FIG. 1  illustrates one embodiment of an ultrasound therapy system including an articulating arm with an arm limiter. 
           [0014]      FIGS. 2A-2B  illustrates the weight compensator and articulating arm of the system of  FIG. 1 . 
           [0015]      FIG. 3  illustrates a joint connecting two links of an articulating arm according to one embodiment. 
           [0016]      FIGS. 4A-4B  show different views of an arm limiter for an articulating arm. 
           [0017]      FIG. 5  shows another view of the system of  FIG. 1 . 
       
    
    
     SUMMARY OF THE DISCLOSURE 
       [0018]    An articulating arm is provided, comprising a first articulating arm link, a second articulating arm link, a rotating joint configured to rotationally connect the first articulating arm link to the second articulating arm link so that the first and second articulating arm links are substantially perpendicular, and an arm limiter attached to the second articulating arm link, the arm limiter being configured to limit rotation of the second articulating arm link along the rotating joint with respect to the first articulating arm link. 
         [0019]    In some embodiments, the arm limiter further comprising a collar portion and a stop limiting portion, the collar portion and the stop limiting portion being configured to attach together around the second articulating arm link. 
         [0020]    In one embodiment, the stop limiting portion includes cutouts configured to engage with and conform to the first articulating link when a specified maximum rotation of the second articulating arm has been reached. 
         [0021]    In one embodiment, the arm further comprises a weight compensator attached to the first articulating arm link and configured to reduce a load on the articulating arm. 
         [0022]    In some embodiments, the arm limiter is set to an appropriate angle in order to prevent undesirable recoiling of the weight compensator and therefore jerk motion on the end of the articulating arm. 
         [0023]    An ultrasound therapy system is provided, comprising an articulating arm having a first articulating arm link, a second articulating arm link, a rotating joint configured to rotationally connect the first articulating arm link to the second articulating arm link so that the first and second articulating arm links are substantially perpendicular, and an arm limiter attached to the second articulating arm link, the arm limiter being configured to limit rotation of the second articulating arm link along the rotating joint with respect to the first articulating arm link, an ultrasound therapy transducer mounted the articulating arm; and an imaging system mounted to the articulating arm. 
         [0024]    In one embodiment, the system further comprises a handle portion coupled to the articulating arm, wherein manipulation of the handle portion adjusts the articulating arm from a locked configuration in which the articulating arm cannot be moved to an unlocked configuration in which the articulating arm can be moved and positioned. 
       DETAILED DESCRIPTION 
       [0025]      FIG. 1  shows a micromanipulator system  100  configured to support and control the movement of an ultrasound therapy transducer  102  and/or an imaging system  104 , such as a transrectal imaging probe. The system can include an articulating arm  106  that can include a plurality of links and joints to move with up to 6 degrees of freedom, and a handle  108  (e.g., a pistol grip) that can be manipulated by a user to control movement of the system. The handle  108  can be actuated by the user to lock the articulating arm in place, or unlock the articulating arm to allow for movement and positioning of the system. Additionally, a side handle  109  can be attached to the micromanipulator to help the user hold and position the micromanipulator system with one hand while the other hand holds the handle  108  on the articulating arm. The therapy transducer  102 , imaging system  104 , and articulating arm  106  can all be supported by and attached to a portable cart  110 , which can include the power generator(s) and/or electronic controller(s)  116 , and any additional hardware and software needed to control and operate the therapy and imaging systems, as well as input devices (e.g., keyboard, GUI) and display devices for treatment planning, execution, and monitoring. 
         [0026]    In some embodiments, the micromanipulator system is configured for treatment of benign prostatic hyperplasia. For example, the therapy transducer  102  can be configured to direct focused ultrasound energy from the perineum to the prostate of a patient, while the imaging system  104  provides ultrasound images of the prostate and therapy. In one embodiment of the system  100 , the articulating arm  106  can be configured to hold and precisely position the components and cabling described above, which can weigh upwards of 15 lbs. 
         [0027]    Still referring to  FIG. 1 , a weight compensator  112  can be attached to at least one of a plurality of articulating joints in the articulating arm  106  to reduce a vertical load on the articulating arm. In one embodiment, the weight compensator  112  can be a spring loaded mechanism that works against gravity so that the user does not need to carry all the weight of the system. The compensator can be applied to a joint or link that handles vertical motion in order to reduce the overall weight of the system carried by the user. In some instances, the weight compensator can recoil, causing a sudden jerk or movement in the articulating arm. These sudden jerks or movements can cause injury to the patient if the imaging probe is positioned within the patient. To prevent sudden jerks in the articulating arm  106 , at least one arm motion limiter  114  can be installed on the arm to reduce rotation at one or more joints of the arm to a specified rotation amount, which can thereby prevent recoil of the weight compensator. This arm motion limiter will be described in more detail below. 
         [0028]      FIG. 2A  shows a schematic view of a weight compensator  212 . The weight compensator can include a spring-loaded compensating end  224  having a cutout  226  configured to engage an adjacent link or joint of an articulating arm. The weight compensator  212  can mount on a first link (such as a horizontal link represented by line  230 ) and the cutout  226  can engage with an adjacent second link that is substantially perpendicular to the first link. The spring-loaded compensating end  224  can then compensate for the weight of the articulating arm by reducing a vertical load on the arm. The tension of the weight compensator can be adjusted by twisting or rotating adjusting ring  228 . 
         [0029]    Referring now to  FIG. 2B , an articulating arm  206  can include multiple links  216   a - 216   f  interconnected by rotational joints  218   a - 218   f,  respectively. In one embodiment, the links can comprise aluminum rods having an outer diameter of 25-100 mm. Each joint connects two neighboring links and enables up to 360 degrees of relative motion between the neighboring links. As a system, these links and joints offer a wide range of motion with up to 6 degrees of freedom for the articulating arm  206 . One end of the articulating arm (e.g., the distal end) can comprise the handle  208  described above. 
         [0030]    When the handle  208  is disengaged (at rest) the links of the articulating arm can be locked in place so as to fix the position of the articulating arm. Engaging (squeezing) the handle  208  can unlock the rotational joints and enable the surgeon or user to position the therapy transducer and imaging system. When the handle is engaged, the surgeon or user must support the weight of both the therapy transducer and imaging system, and the weight of half of the arm (e.g., a combined weight of approximately 15 lbs). It can be challenging to deftly manipulate this load in all directions and can lead to safety issues, such as the potential to injure the patient&#39;s rectum with the imaging probe as it is being positioned in the rectum for prostate imaging. 
         [0031]    As described above, a spring-loaded weight compensator can be added to compensate the arm load on one or more joints. When mounted on a horizontal link, as shown in  FIG. 1 , the spring can compensate for the vertical load or weight in the up/down direction. This configuration can eliminate the sudden weight load that occurs when the pistol grip handle is released, and eases or eliminates the weight burden of the system as the surgeon inserts the imaging probe into the rectum. However, one significant drawback with the weight compensator is that can recoil when the arm link is fully extended, which can cause a sudden jerk in the arm. This sudden jerk is a safety issue since the sudden recoil could harm the patient. 
         [0032]    An arm limiter can be mounted to the articulating arm to eliminate the potential for the weight compensator to recoil. This can be done by limiting the rotation of specific links around its adjacent link. Still referring to  FIG. 2B , in one specific embodiment, the rotation of link  216   d  can be limited to a specific range of motion (e.g., limited to 120 degrees of rotation) around link  216   c  with an arm limiter installed at joint  218   c  (between links  216   c  and  216   d ). Additionally, this arm limiter can restrict the rotation between link  216   b  and link  216   d  (when in the horizontal position) to a specific range of motion (e.g., be less than 180 degrees). In one specific embodiment, in order to eliminate the potential for recoil from the weight compensator, the arm limiter can be configured to restrict an angle between adjacent links to 150° or less. In other embodiments, the relative maximum angle between the links depends on the design of the arm. 
         [0033]      FIG. 3  shows a top down view of an arm limiter  314  and arm limiter collar  315  installed between links  316   b  and  316   d  of an articulating arm  306 . Note that links  316   b  and  316   d  are in the same plane (the plane of the page) and that there may be another central link not shown in the drawing perpendicular to links  316   b  and  316  that extends out of the plane of the page (similar to the arrangement of links  216   b,    216   c,  and  216   d  in  FIG. 2B ). The arm limiter can be installed on the joint between link  316   d  and the central link, or on the central link itself. The collar  315  holds the arm limiter  314  onto the desired link, and the arm limiter  314  includes one or more stop limit portions  319  comprising cutouts or protrusions that engage the link to be rotation limited when a desired maximum rotation has been reached. In  FIG. 3 , the stop limiting portion  319  limits the rotation of link  316   d  to a limited rotation angle  321 , illustrated in  FIG. 3  Therefore, the stop limiting portion  319  of the arm limiter  314  can act as physical stops that engage the desired link to physically prevents further rotation of that link. The arm limiter can be configured to limit rotation between the two links to any desired range, such as to less than 150 degrees. Furthermore, the allowed angle of rotation between the adjusted links can be adjusted which will be described in more detail below. 
         [0034]      FIGS. 4A-4B  illustrate various views of the arm limiter  414  and collar  415 .  FIG. 4A  is a top down view, showing attachment of the arm limiter to the collar with screws  417 . The collar and limiter can be clamped around the desired link or joint of the articulating arm to prevent or limit rotation of the adjacent link. As described above, stop limiting portion  419  can limit rotation of the desired link to limited rotation angle  421 . 
         [0035]      FIG. 4B  shows a side view of the collar  415  and arm limiter  414 . In this example, the collar and arm limiter can be clamped around a vertical link extending in direction  420  (shown as a dashed line), and stop limiting portion  419  of the arm limiter can be configured to engage and act as a stopping mechanism against the adjacent (in this example, horizontal) link extending in direction  422  (shown as a dashed line). Thus, the arm limiter can be mounted onto a joint or link extending in direction  420  to limit the rotation of a link extending in direction  422 . If the links are cylindrical, for example, the stop limiting portion  419  can include cutouts or protrusions having a curvature designed to conform to the adjacent link when the maximum rotation is reached. 
         [0036]      FIG. 5  illustrates another view of arm limiter  514  installed on a vertical link  516   c  of an articulating arm  506 , but not yet engaging the adjacent horizontal link  516   d.  The collar and cutouts or stop limiting portion  519  can also be seen in  FIG. 5 .  FIG. 5  also shows another view of side handle  509  on the therapy transducer  502  configured to provide additional assistance for moving the load of the articulating arm by enabling the user to use two hands to support and guide the load. 
         [0037]    Variations of the arm limiter design can restrict the manipulation of the arm and its load in different ways. Different limitation angles and/or a combination of multiple arm limiters for multiple joints could be used to meet a myriad of different load requirements and/or application requirements. 
         [0038]    The examples and illustrations included herein show, by way of illustration and not of limitation, specific embodiments in which the subject matter may be practiced. As mentioned, other embodiments may be utilized and derived there from, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Such embodiments of the inventive subject matter may be referred to herein individually or collectively by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept, if more than one is, in fact, disclosed. Thus, although specific embodiments have been illustrated and described herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.