fig1 illustrates a biopsy needle 10 according to the invention comprising a stylet 12 received within a narrow diameter ( 18 to 22 gauge ) hollow cannula 14 . the cannula 14 comprises a proximal hub 16 , a sharp distal tip 18 , and a central lumen 20 therethrough ( fig2 ). the outer surface of the cannula 14 is preferably polished to a smooth finish and formed of a material suitable for introduction into the human body such as stainless steel . to further ease the introduction of the cannula 14 into a portion of a human body , the outer surface of the cannula 14 can be coated with silicone . as shown in fig2 the biopsy needle 10 is of the chiba style , wherein the cannula distal tip 18 is beveled at an acute angle to a longitudinal axis 22 of the cannula 14 . the stylet 12 , similarly comprises a proximal hub 24 ( fig1 ) and a sharp beveled distal tip 26 . with the stylet 12 fully received within the cannula lumen 20 , the beveled surfaces of the cannula distal tip 18 and of the stylet distal tip 26 preferably align to form a smooth cutting surface . other tip designs commonly used in the art , such as a franseen tip having multiple beveled surfaces , may substitute for the chiba type tip illustrated in fig1 and 2 . in a fine - needle aspiration biopsy , a surgeon uses the biopsy needle 10 to obtain a sample of tissue cells and surrounding fluid from a specific area of a patient &# 39 ; s body . the surgeon inserts the cannula distal tip 18 , with the stylet distal tip 26 received and properly aligned within , into the patient &# 39 ; s body in the direction of the desired area . in many procedures , ultrasound imaging using pulsed sound energy provides real - time information to the surgeon concerning the location of the cannula distal tip 18 with respect to a desired area of the patient &# 39 ; s body . in the present invention , the outer surface of the cannula 14 is smooth and polished to reduce tissue trauma and patient discomfort , while an echogenicity enhancement 28 on the stylet 12 within the cannula lumen 20 increases the perceived echogenicity of the biopsy needle 10 within the body . the term echogenicity refers to the relative extent that a surface reflects incident ultrasound wave energy directly back to a sensor , which is proximal to the source or emitter of the ultrasonic wave energy . ultrasound energy from a transducer ( not shown ) reflects off of the echogenicity enhancement 28 , through the wall of the cannula 14 and back to the transducer . as shown in fig2 the echogenicity enhancement 28 comprises a portion of the stylet 12 wherein a plurality of adjacent shallow concave annular grooves 30 circumscribe the outer surface of the stylet 12 . the portion of the stylet having the grooves 30 preferably approaches the stylet distal tip 26 closely , as accurate placement of the sharp distal tips of the stylet and cannula 26 , 18 remains the ultimate goal of the echogenicity enhancement 28 . the grooves 30 may extend proximally to the stylet hub 24 for enhanced imaging of essentially the entire biopsy needle 10 , but need only be located adjacent the distal tip 26 for accurate placement thereof . the grooves 30 can be oriented and arranged to provide a diffraction grating tuned to the frequency of the ultrasound waves according to the following formula : ## equ1 ## where d is the distance between adjacent grooves 30 , n is an integer , λo is a center wavelength of the ultrasound energy , and θ is the incidence angle between the direction of travel of the ultrasound waves and the cannula longitudinal axis 22 . further expedients for enhancing echogenicity of the stylet 12 are illustrated in fig3 through 14 , wherein like parts are numbered with like numerals . as shown in fig3 the echogenicity enhancement 28 may comprise a plurality of adjacent convex annular grooves 32 about the outer surface of the stylet 12 . alternatively , as shown in fig4 the echogenicity enhancement 28 may comprise a plurality of equally spaced apart concave annular grooves 34 about the outer surface of the stylet 12 , wherein intervals 36 between adjacent grooves 34 are convex . as shown in fig5 the echogenicity enhancement 28 may comprise a plurality of equally spaced apart annular grooves 38 about the outer surface of the stylet 12 , and wherein each groove 38 has a truncated v - shape . any of the grooves 30 , 32 , 34 , or 38 previously described can be formed as a continuous spiral as opposed to separate annular grooves . for example , in fig6 the echogenicity enhancement 28 comprises a continuous spiral groove 40 about the surface of the stylet 12 , wherein the groove has a generally square cross sectional shape . fig7 illustrates an alternative method for forming a spiral pattern on the stylet 12 . a wire coil 42 spirals about a reduced diameter portion 44 of the stylet 12 , and is attached at each end of the reduced diameter portion 44 by means of solder 46 . alternatively , as shown in fig8 the wire coil 42 spirals about a narrow diameter stylet 12 , and solder 48 at the stylet distal tip 26 secures one end of the wire coil 42 to the stylet 12 , and additional solder 50 secures the opposite end of the wire coil 42 to the stylet . the solder 48 at the distal end 26 is milled to form the beveled stylet distal tip 26 conforming to the cannula distal tip 18 . in fig9 the stylet 12 comprises a series of conical campanulate beads 52 arranged in end to end relationship to form the elongated stylet 12 . longitudinal patterns on the stylet 12 also provide echogenicity enhancement . for instance , fig1 illustrates a stylet 12 wherein the echogenicity enhancement 28 comprises a series of narrow and shallow longitudinal grooves 54 along the surface of the stylet 12 , arranged in a pattern encircling the stylet 12 . alternatively , fig1 illustrates the echogenicity enhancement 28 as a cross - hatched pattern 56 . alternative roughened sections similar to the cross hatched pattern 56 , such as a particle blasted section ( not shown ) can also provide echogenicity enhancement 28 . further , the longitudinally oriented echogenicity enhancement 28 can comprise an elongated section of the stylet 12 having various cross sectional shapes . for example , fig1 illustrates such a section 58 wherein the cross sectional shape is hexagonal , whereas fig1 illustrates such a section 60 wherein the cross sectional shape is cruciate . as an alternative to forming an echogenicity enhancing pattern upon the stylet 12 , fig1 illustrates the echogenicity enhancement 28 as a reduced diameter section 62 of the stylet 12 filled with epoxy 64 or similar material containing small particles of plastic or metal &# 34 ; chaff &# 34 ; 66 of a sound reflecting nature . for purposes of illustration , the stylet 12 of fig1 is illustrated with a sample notch 68 , to show that all types of cutting stylets may be echogenically enhanced according to the present invention . while particular embodiments of the invention have been shown , it will be understood , of course , that the invention is not limited thereto since modifications can be made by those skilled in the art , particularly in light of the foregoing teachings . reasonable variation and modification are possible within the foregoing disclosure of the invention without departing from its true spirit and scope . for instance , the echogenicity enhancement 28 may be provided upon the inner surface of the cannula 14 , particularly on the inner wall of the lumen 20 , thus providing enhanced echogenicity while retaining a smooth outer surface to the cannula 14 . the invention is particularly described in connection with certain specific embodiments thereof by way of illustration and not of limitation , and the scope of the appended claims should be construed as broadly as the prior art will permit .
an echogenic medical needle is disclosed which comprises a tubular cannula body , a stylet received within the cannula body , and an echogenicity enhancement within the cannula for improved ultrasound imaging . preferably , the echogenicity enhancement is on the stylet and comprises a series of annular grooves about the stylet .