Patent Document

PRIORITY CLAIM 
     This application claims the priority to the U.S. Provisional Application Ser. No. 61/141,473, entitled “Echogenic Enhancement for a Needle” filed on Dec. 30, 2008. The specification of the above-identified application is incorporated herewith by reference. 
    
    
     BACKGROUND 
     Needle biopsies are common procedures for the diagnosis and staging of disease. These procedures are often done under ultrasound guidance to allow physicians performing the procedure to visualize the position of the needle in relation to target and surrounding tissue structures. Thus, the echogenicity of the needle (i.e., the visibility of the needle under ultrasound) often impacts the success of the procedure. The echogenecity may be affected by the size of the needle, a difference between the acoustic impedance of the needle and that of the surrounding tissue, an angle of the needle relative to the transducer, the frequency of the ultrasound energy used and various characteristics of the processing algorithm. 
     Various techniques have been developed in an attempt to improve the echogenic properties of needles including mechanical treatments of the outer surface of the needle or echogenic coatings. However, the current mechanical treatments involving the creation of discrete shapes repeated along the axis and/or about the circumference of a needle are complex to form. Other mechanical treatments include the formation of circumferential grooves or spirals around the needle. However, these grooves are tuned to only one angle and one frequency such that a slightly different spacing and/or a different frequency may have a significant negative impact on echogenic performance. The application of echogenic coatings increases the complexity of the devices and does not necessarily enhance the performance of these coated devices relative to the mechanical treatments described above. Furthermore, the echogenic properties of these coatings may decay over time. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a needle comprising a surface with a plurality of first ultrasound reflecting depressions formed therein, the first depressions being distributed along at least a portion of a length of the needle separated from one another by intervening sections, each of the first depressions extending along a curve between first and second ends adjacent to corresponding ones of the intervening sections with troughs at which surfaces of each of the first depressions most closely approach a longitudinal axis of the needle being offset toward the first ends of each of the first depressions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a needle, according to an exemplary embodiment of the present invention; 
         FIG. 2  shows an enlarged partial side view of a needle with depressions along a length of the needle, according to the exemplary embodiment of  FIG. 1 ; 
         FIG. 3  shows an enlarged partial side view of a needle with depressions of a variety of shapes, according to a further embodiment of the present invention; 
         FIG. 4  shows an enlarged partial side view of a needle with depressions of a variety of shapes and spaces, according to another embodiment of the present invention; and 
         FIG. 5  shows an enlarged partial side view of a needle with depressions along a length of the needle and a coating layer, according to a further embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention, which may be further understood with reference to the following description and the appended drawings, relates to devices for conducting biopsies under ultrasound guidance. Exemplary embodiments of the invention are directed to a pattern on an outer surface of a needle such that the needle has enhanced ultrasound visibility, allowing the needle to remain visible at various angles relative to the transducer. It will be understood by those of skill in the art that although the exemplary embodiments are described as a needle, the device may be any medical device that may be seen under ultrasound guidance. It will also be understood by those of skill in the art that since ultrasound is an electromagnetic energy, the patterns described herein, which enhance visibility, may also be used with other energy sources such as, for example, light. 
     As shown in  FIG. 1 , a needle  100  according to an exemplary embodiment of the invention comprises a longitudinal body  118  extending between a distal end  120  and a proximal end  122 . An outer surface  104  of the needle  100  includes a plurality of depressions  106  formed along at least a portion of a length of the needle  100  to enhance the visibility of the needle  100  under ultrasound guidance by scattering and reflecting back toward a transducer sound waves incident thereon. The needle  100  will generally comprise a lumen  102  extending therethrough to an opening in a distal tip  110  at a distal end  120  of the needle  100  for collecting target tissue as would be understood by those skilled in the art. As shown in  FIG. 1 , the tip  110  may be formed by a cut through the needle  100  at an angle relative to a longitudinal axis of the longitudinal body  118 . so that a distal-most surface of the needle  100  extends along an angle relative to a longitudinal axis of the needle  100  with an area of the opening to the lumen  102  greater than a cross-sectional area of the lumen  102  within the needle  100 . 
     As would be understood by those skilled in the art, the needle  100  may be formed of any biocompatible material rigid enough to penetrate the tissue targeted by the procedure to which the needle  100  is directed. For example, the needle  100  may be formed of stainless steel or tungsten to enhance the echogencity of the needle. As would be understood by those skilled in the art, tungsten has an acoustic impedance greater than that of stainless steel increasing the difference in acoustic impedance between the needle  100  and the surrounding tissue and thereby enhancing echogenicity. It will be understood in the art, however, that any of a variety of materials may be used to form the needle  100  so long as the material is biocompatible and provides a visible difference in echogenicity as compared to the tissue through which it will be deployed. 
     The depressions  106 , as shown in the enlarged side view of  FIG. 2 , are shaped to directly reflect sound waves received over a broad range of angles so that the transducer may be placed in a variety of positions relative to the needle  100 . That is, the shapes of the depressions  106  are selected to present at least a part of a face thereof substantially perpendicular to incoming ultrasound radiation over a wide range of incoming angles so that this radiation will be reflected back to the device from which it originated. Thus, a surface of the depression  106  ranges from a steep portion  112  extending from a first end portion abutting a space  108  between adjacent depressions  106  nearly perpendicular to a longitudinal axis of the needle  100  to a trough  114  at which the depression  106  transitions to a shallow portion  116  extending to a second end portion of the depression  106  at an angle less steep than that of the steep portion  112 . That is, as the depth of each of the steep portion  112  is equal to that of the shallow portion  116 , the trough  114  is closer to the first end than to the second end of the depression  106 . At the first end, the surface of the steep portion  112  is, therefore, close to a plane perpendicular to a longitudinal axis of the needle  100  sloping slightly toward a plane parallel to the longitudinal axis. Thus, at least a portion of sound waves from a transducer positioned anywhere in the range of slightly more than 0° to close to 90°, relative to a longitudinal axis of the needle  100  will impact a portion of the depression  106  which is substantially perpendicular to a front of the wave sending the wave directly back to the transducer. The steep portion  112  is positioned to reflect waves back to a transducer aimed nearly parallel (close to)0° to the needle  100  while the shallow portion is oriented to reflect waves back to a transducer positioned substantially perpendicular to the longitudinal axis (close to 90°) of the needle  100  while the gradual transition between these portions provides surfaces oriented to reflect back to a transducer ultrasound radiation impinging on the needle  100  at any angle between these extremes. It will be understood by those of skill in the art that where the transducer is positioned proximally of the distal end  120  of the needle  100 , the steep portion  112  may face proximally such that the sound waves reflect over a broad range of needle-transducer angles. 
     In a preferred embodiment, each depression  106  extends around an entire circumference of the needle  100 . However, it will be understood by those skilled in the art that the depression  106  may extend around only a portion of the circumference of the needle  100  or may be configured as a slot on the outer surface  104  of the needle  100 . A space  108  which is substantially flat along a length of the needle  100  is located between each pair of adjacent depressions  106 . In the embodiment shown in  FIGS. 1 and 2 , the depressions  106  are substantially evenly spaced such that each space  108  is equal in length. However, it will also be understood by those of skill in the art that the length of each space  108  may vary along the length of the needle  100 . Although the needle  100  is described as being substantially cylindrical, it will be understood by those of skill in the art that the needle  100  may take a variety of shapes so long as it includes a plurality of depressions  106  about at least a portion of a perimeter of the outer surface  104 . 
     It will be understood by those of skill in the art that the features of the needle  100 , as described above may also be included in other medical devices that may be viewed under ultrasound guidance. For example, in another embodiment, a sheath, which may be slidable along a portion of a length of a needle may include a pattern substantially similar to the pattern formed by the depressions  106  on the needle  100 . In another embodiment, a stylet, which may be slidable through a lumen of a needle to prevent non-target tissue from entering the lumen may be formed with a pattern substantially similar to the pattern formed by the depressions  106  on the needle  100 . 
     A needle  200  according to another embodiment of the invention is substantially the same as the needle  100  described above except that the depressions  206  of the needle  200  are not all of the same shape. For example, the depressions  206  include a plurality of first depressions  206   a  each of which includes a steep portion  212  oriented to more effectively reflect energy back to a transducer oriented substantially parallel to the needle  200  from the steep portion  212  while each of a plurality of second depressions  206   b  is shaped as a shallow bowl  214  oriented to more effectively reflect energy to a transducer oriented at a steeper angle relative to the longitudinal axis of the needle  200  (at an angle close to 90° relative to the needle  200 ). In the embodiment of the needle  200  shown in  FIG. 3 , each of the first depressions  206   a  is located between a pair of second depressions  206   b  are separated by a space  208  which is substantially flat along a length of the needle  200 . As described above in regard to the needle  100 , the spaces  208  of the needle  200  are substantially equal in size. However, it will be understood by those of skill in the art that the various depressions  206   a ,  206   b  may be separated by spaces  208  of varying size, as shown in  FIG. 4 . It will also be understood by those of skill in the art that the different sizes of the spaces  208  may further tune the response to the sound waves at different angles. Furthermore, those skilled in the art will understand that more than 2 shapes of depressions  206  may be included in the needle  200 . For example, a plurality of first depressions may be oriented to effectively reflect energy delivered from a probe angled between 0 and 30° relative to the longitudinal axis of the needle  200  while a plurality of second depressions is oriented to effectively reflect energy delivered from a probe angled between 30 and 60° relative to the longitudinal axis and a plurality of third depressions is oriented to effectively reflect energy delivered from a probe angled between 60 and 90° relative to the longitudinal axis. 
     In a further embodiment of the present invention, as shown in  FIG. 5 , a needle  300 , which may be substantially similar to either of the needles  100  and  200  described above, further comprises a coating layer  316  covering a plurality of depressions  306 . Although  FIG. 5  shows the needle  300  including depressions  306  of a single shape as in the needle  100 , it will be understood by those of skill in the art that the coating layer  316  may be included on any of the needle embodiments described above with any variety of depression shapes and spacings. The coating layer  316  may be formed of a material having an acoustic impedance similar to that of the body tissue within which the needle  300  is to be deployed, but with a lower speed of sound transmission therethrough. This difference in the speed of sound transmission through the tissue and the coating layer  316  refracts the sound waves toward the needle  300 , steepening their angle of impact and improving the amount of acoustic energy reflected back to the transducer. An example of a coating layer that may be used is PTFE, which has a lower speed of sound, resulting in the refracted sound waves. A depth of the coating  316  may also be varied to optimize constructive interference and minimize destructive interference between incoming sound waves and reflected sound waves leaving the surface  318  of the coating  316 . 
     The embodiments of the present invention, as described above, may be easily manufactured using a simple tool. For example, the depressions  106  may be formed in the needle  100  using a tool with a protrusion a profile of which matches a desired shape of the depression  106 . The tool may be rotated about a circumference, or a part of a circumference, of the needle  100  with the protrusion contacting the outer surface  104  to form the depressions  106  in the longitudinal body  118  the needle  100  as would be understood by those skilled in the art. Alternatively, instead of rotating the tool about the needle  100 , the needle  100  may be rotated about a longitudinal axis of the needle while the tool remains stationary such that the protrusion contacts the outer surface  104  of the needle  100 . The plurality of depressions  106  may be formed by simply moving the tool along the longitudinal axis of the needle  100  or by moving the needle  100  along the longitudinal axis, by a desired distance of the space  108 , and rotating the tool or the needle  100  as described above. This may be repeated until a desired number of depressions  106  have been formed. Alternatively, a tool may include multiple protrusions to form the desired number of depressions  106  in one operation or in a reduced number of operations. For example, a tool to form a needle such as the needle  200  may include a first protrusion having a shape corresponding to the desired shape of the first depressions  206   a  while a second protrusion has a shape corresponding to a desired shape of the second depressions  206   b , etc. 
     Alternatively, patterns formed by the depressions  106 ,  206 ,  306  may be applied to the needles  100 ,  200 ,  300 , respectively, in the form of rings or other similar elements applied around at least a portion of the outer surfaces of the needles  100 ,  200  and  300 . In another embodiment, a press may be used to stamp the needles with the depressions  106 ,  206 ,  306  to form the desired patterns on the needles  100 ,  200  and  300 . In another embodiment, the depressions  106 ,  206  may be formed by laser micro-machining or by using an EDM process. However, it will be understood by those of skill in the art that any of a variety of methods may be used for forming any of the depressions  106 ,  206 ,  306  in the needles  100 ,  200 ,  300 . As would be understood by those skilled in the art, once the depressions  306  have been formed by any of the above-described methods, the needle  300  may be coated with a desired thickness of the selected material to form the coating  306  using any known technique. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the structure and methodology of the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims and their equivalents.

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