Abstract:
A medical device comprises a cannula for insertion to a target location in a body and at least one resonator situated on a surface of the cannula. The resonator resonates in response to an ultrasonic frequency applied to the target location to indicate the location of the cannula in the body. The ultrasonic frequency is generated by a transducer located external to the body. The medical device also comprises a device converting resonated frequencies into an image.

Description:
PRIORITY CLAIM 
       [0001]    The present application claims the priority to the U.S. Provisional Application Ser. No. 61/245,454, entitled “ECHOGENIC NEEDLE MECHANISM” filed on Sep. 24, 2009. The specification of the above-identified application is incorporated herewith by reference 
     
    
     BACKGROUND 
       [0002]    Needle catheters are often employed to inject fluids and/or obtain fluid or tissue samples for diagnosis and/or treatment. In these procedures, a needle is advanced to a target tissue site within a catheter under ultrasound guidance. The needle may be advanced distally from the catheter to penetrate the target site. The ultrasound image can allow a user to visualize the position of the needle in relation to the target and surrounding structures and aids in ensuring that a correct tissue portion is treated, sampled, etc. to minimize the risk of trauma or injury to non-targeted tissue. A common challenge associated with the use of ultrasound imaging is the relatively low echogenicity of the needle and the lack of clarity in the resulting images. 
         [0003]    As would be understood by those skilled in the art, several factors play a role in the echogenicity of the needle including needle gauge, the difference in acoustic impedance between the needle and the surrounding tissue, the angle of the needle relative to the transducer, the frequency being used and various characteristics of the processing algorithm. 
       SUMMARY OF THE INVENTION 
       [0004]    A medical device according to the present invention comprises a cannula for insertion to a target location in a body and at least one resonator situated on a surface of the cannula, the resonator resonating in response to an ultrasonic frequency applied to the target location to indicate the location of the cannula in the body, wherein the ultrasonic frequency is generated by a transducer located external to the body. The medical device also comprises a device converting resonated frequencies into an image. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a side view of an exemplary device according to the present invention; 
           [0006]      FIG. 2  shows a side view of a needle according to a first exemplary embodiment for use with the device of  FIG. 1 ; 
           [0007]      FIG. 3  shows a side view of a needle according to a second exemplary embodiment for use with the device of  FIG. 1 ; 
           [0008]      FIG. 4  shows a side view of a needle according to a third exemplary embodiment for use with the device of  FIG. 1 ; and 
           [0009]      FIG. 5  shows a side view of a needle according to a fourth exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The present invention, which may be further understood with reference to the following description and the appended drawings, relates to a device to enhance the ultrasonic visibility of a needle when deployed within the body to perform a procedure such as, for example, a needle biopsy. It is noted, however, that although the exemplary embodiments of the present invention are described with respect to particular procedures, the description is not meant to limit the application of the invention, which may be employed in any of a number of procedures requiring the insertion of a needle to a target site within the body. 
         [0011]    Devices and methods according to exemplary embodiments of the invention enhance the visibility of a needle when deployed, for example, from a catheter to a target site within the body. Specifically, exemplary embodiments of the present invention seek to enhance the echogenicity of a needle in situ by providing resonating features thereupon, the resonating features designed to resonate at a predetermined frequency which may be applied thereto via an ultrasound transducer or another means known in the art. Any of a variety of known mechanical arrangements may be employed to generate a mechanical force at a distal portion of the catheter for the deployment of the needle therefrom. This invention is not restricted to needles but may also be applicable to any number of cannulas or catheters to a visualized remotely by, for example, ultrasound. In one example, the present invention may be employed in an ablation device. 
         [0012]    As shown in  FIGS. 1 and 2 , a device  100  according to a first exemplary embodiment of the present invention comprises a needle  102  having a tubular body with a lumen  104  extending therethrough from a proximal end extending into a handle  120  to a distal end comprising a puncturing tip  106 . It is noted that the use of the term distal herein refers to a direction away from a user of the device while the term proximal refers to a direction approaching a user of the device. The proximal portion of the device  100 , including the handle  120 , remains external to the body and accessible to the user while the distal portion, when in an operative position, extends into the body to a target site from which tissue samples are to be obtained in accordance with the biopsy procedure. A shaft  116  of the device  100  and the needle  102  may be rigid or, alternatively, may be longitudinally flexible and axially rigid to allow for the insertion of the shaft  116  and the needle  102  along a tortuous path (e.g., through a body lumen) to a target site within the body. The needle  102  may be formed of any suitable biocompatible material known in the art depending on the desired properties of the needle (e.g., rigidity/flexibility, etc.). 
         [0013]    A series of circumferentially aligned beams  108  are formed along at least one longitudinal length of the needle  102 . In a preferred embodiment, two sets of beams  108  are formed on opposite sides A and B (shown in phantom) of the needle  102 , as shown in  FIG. 2 . The beams  108  may be provided over any part of the needle  102  without deviating from the scope of the present invention. The beams  108  may be cantilever beams formed, for example, by laser micromachining or micro-stamping the outer surface of the needle  102 . Alternatively, a surface micromachining process may be used to deposit or etch beams  108  onto the surface of the needle  102 . In an alternate embodiment, the beams  108  located on opposite sides A and B may also be formed in different configurations, so as to distinguish an orientation of the needle  102  in situ, as those skilled in the art will understand. Specifically, shapes and sizes of the beams  108  on opposite sides A and B may be distinguishably varied from one another so that an orientation of the needle  102  can be determined based on the location of sides A and B in situ. It is preferred, however, to maintain similar resonance requirements on each side A and B so that both sides are locatable at least one predetermined frequency. 
         [0014]    The dimensions of each of the beams  108  may also be varied depending on the type of procedure being performed so that the natural frequency of the beams  108  coincides with the ultrasonic frequency of interest, as those skilled in the art will understand. If a particular procedure requires the targeting of more than one ultrasound frequency (i.e., to overcome excessive noise encountered at a first frequency, etc.), the beams  108  may be formed with different dimensions to accommodate the plurality of frequencies. Such an embodiment will aid in the location of the needle  102  in the body when any of the plurality of target frequencies are employed. Furthermore, in a preferred embodiment, beams  108  of different natural frequencies are evenly distributed along the needle  102 , such as, for example, in an alternating pattern. In one embodiment, the frequencies may include 5 MHz and 7.5 MHz, although any other frequencies may be employed without deviating from the scope of the present invention. Furthermore, the beams  108  may have varying geometries including, but not limited to rectangular, square and triangular and may also have varying thickness, widths and heights. The beams  108  may also comprise any combination and plurality of holes, cutouts, slots, slits, bends and other surface features (e.g., peaks, valleys, etc.) without deviating from the scope of the present invention. 
         [0015]    The beams  108  function as resonators in the needle, as those skilled in the art will understand. When used under ultrasound guidance, the acoustic energy from an ultrasound transducer located external to the body when in an operative configuration causes the beams  108  to resonate, thus providing an ultrasonic image of the needle  102 . 
         [0016]    Those skilled in the art will understand that cantilever beams can resonate to any multiple of their fundamental frequency. Altering the geometry of the beams  108  can increase the fundamental frequency. For example, as shown with respect to  FIG. 2 , beams  108 ′ can be formed to resemble two adjacent arced pieces lying along a longitudinal length of the needle  102 , wherein the adjacent pieces are separated from one another by a distance D 1 . The distance D 1 , along with other dimensional values of the beams  108 ′ is indicative of the resonating frequency thereof. Since the two arced pieces are not joined together at a proximal end, resonance can be increased, as those skilled in the art will understand. It is noted that any configuration of the beams  108  may be employed without deviating from the spirit and scope of the present invention. 
         [0017]    Resonance in the device of the present invention may also be improved by providing a resonating stylet  110  to be used with the needle  102 . The resonating stylet  110  would not have to be employed in conjunction with the needle  102  comprising the beams  108 . Rather, the resonating stylet  110  may function with any medical device within which the stylet  110  may be received. Specifically, as shown in  FIG. 3 , the stylet  110  may be formed in a cantilever shape, wherein a distal portion of the stylet  110  is formed with two legs  112  spaced from one another and joined to a proximal portion of the stylet at a juncture  114 . The legs  112  may be formed as a unitary element with the stylet  110  or, alternatively, may be formed separately and attached thereto via a means known in the art such as bonding, welding, etc. A distal portion of the stylet  110  serves as a resonator, wherein the dimensions of the legs  112  may dictate the appropriate resonance frequency for the ultrasound. In one embodiment, the resonance frequency of the cantilever may be approximately 5 MHz to conform to available ultrasound systems, although any other frequency may also be employed without deviating from the scope of the present invention. In a further embodiment of the present invention, the stylet  110  may also be provided with beams  108  or  108 ′ to further improve imaging or to enable visualization of the stylet  110  under a plurality of frequencies, as explained earlier. Specifically, the beams  108  or  108 ′ may be formed as cut-outs formed in the stylet or may be abutments bonded or otherwise attached to the outer surface of the stylet  110 . It is noted that the device of the present invention is not limited to the stylet  110  as depicted but may employ any stylet known in the art. Similarly, the stylet of the present invention may be employed with any device comprising ultrasonic resonators. 
         [0018]    In an alternate embodiment of the present invention, fabrication of the beams  108  of the present invention may be done using the same manufacturing technology used for electrical circuit or micro-electrical mechanical systems (“MEMS”). In this manner, a resonant mechanical system may be produced for one or more frequencies of interest. In yet another alternate embodiment, a micro-miniature ultrasonic transducer may be mounted on one or both of the needle  102  or the stylet  110  of the present invention. The micro-miniature ultrasonic transducer may function as a transmitter insertable into the body, with the external ultrasound device functioning as a receiver, as those skilled in the art will understand. 
         [0019]    In use, the needle  102  is received within a lumen  118  extending through a catheter shaft  116 , the lumen  118  is sized to slidably receive the needle  102  with a clearance between the needle  102  and an inner wall of the lumen  118 . 
         [0020]    Once the catheter shaft  116  is positioned in a desired location relative to a target tissue site in the body, an ultrasonic scanner  124  transmits a predetermined ultrasonic frequency. Specifically, a probe  126  generates the designated frequencies to the target area in the body via a path  132 . That is, a transducer  128  may be attached to an end of the probe  126 . In another embodiment, a separate handheld probe (not shown) may be employed. The transducer  128  may be coupled to the probe  126  using a means known in the art and may employ a known material (e.g., water, jelly, etc.) to reduce impedance by the skin. Upon receipt of these frequencies, the beams  108  may resonate and return the frequencies to the ultrasonic scanner  124 . A transducer  128  may then convert the received frequencies into electrical pulses that can be processed and transformed into a digital image. The ultrasonic scanner  124  then displays the image on a screen  124  visible to a user of the device and operable in real-time. In a preferred embodiment, the image is visible to the user in real time to aid in proper positioning of the catheter shaft  116  in the body. Once a distal portion of the device  100  is properly positioned within the body, actuation of an actuator (not shown) on the handle  120  the needle  102  out of the lumen  118  using a mechanical means known in the art. A stylet may be housed in the needle  102  during insertion to prevent unwanted foreign materials from entering the needle, as those skilled in the art will understand. A designated procedure such as a biopsy may then be performed. After a procedure has been completed, the user of the device  100  retracts the needle  102  by, for example, withdrawing the actuator (not shown) in the opposite direction until the puncturing tip  106  of the needle  102  is again fully housed within the catheter shaft  116 . 
         [0021]    It is noted that the design of the handle  120  may take any desired shape as dictated, for example, by ergonomics, etc. and is not limited to the arrangement shown in the embodiment of  FIG. 1 . The handle  120  is configured to control actuation of the needle  102  via telescoping tubular configuration. Furthermore, it is noted that the catheter shaft  106  may extend proximally from the handle  130  of the device  100  by any desired length, which length may, for example, be selected to conform to the specific requirements for a procedure being performed. 
         [0022]      FIG. 5  depicts a system according to an alternate embodiment of the present invention, wherein the device is formed substantially similarly to the device  100  of  FIG. 1  with the exception of a sheath  200  provided over an outer surface of the needle  102 . The sheath  200  may be provided with resonators  208  distributed thereover in any configuration. The resonators  208  may be formed as cutouts on the sheath  200  or abutments bonded or otherwise attached to the sheath  200  and may be configured to enhance the resonance of the beams  108  of the needle  102 , as those skilled in the art will understand. In use, the sheath (not shown) may be provided over the needle  102  and, once the catheter shaft  116  is positioned in a desired location relative to a target site in the body, the ultrasonic scanner  124  and transducer  128  may be operated as described above to aid in visualization of the needle  102 . 
         [0023]    The present invention may be applied to any procedure requiring the insertion of a needle into tissue via a device traversing a tortuous path. Though the present invention has been described with respect to the retrieval of tissue samples, it is submitted that devices for alternate uses such as, for example, needles for injection of fluids to or the withdrawal of fluids from the body may employ to invention without deviating from the spirit and scope of the present invention. Thus, these embodiments have been described in an exemplary manner and are not intended to limit the invention which is intended to cover all modifications and variations of this invention that come within the scope of the appended claims and their equivalents. For example, the beams of the present invention may be formed separately from the needle and can be subsequently bonded to the needle via a means known in the art. Furthermore, it is noted that the ultrasonic resonators of the present invention are not restricted for use with needles and rather, may be employed in any medical device visualized by the use of ultrasound. It is therefore submitted that the embodiments disclosed herein are not limited to limit the scope of the present invention.