Method for making hydrogel markers

Abstract

A hydrogel marker is placed under stress during its curing stage, in one embodiment, by application of an externally applied force. The stress may also be induced during or after the dehydration process. The direction of the externally applied force increases the length, width, depth, or radial extent of the marker. The elastic limit of the marker is exceeded when the external force is applied so that the marker substantially retains its stressed size and shape when the externally applied force is removed. When the stretched or otherwise deformed dehydrated marker is hydrated, it substantially returns to the configuration it had prior to its dehydration and prior to the application of the externally applied force.

1 .- 16 . (canceled) 
     
     
         17 . A method for manufacturing a biopsy site marker, the method comprising:
 (a) forming a body of the biopsy site marker from a hydrogel;   (b) curing the hydrogel;   (c) inducing stress in the hydrogel during the step of curing, the stress being induced in a transverse direction relative to a longitudinal axis defined by the body, thereby decreasing a length of at least one dimension of the body, such that the body will expand in length about the at least one dimension upon deployment of the biopsy site marker in tissue; and   (d) inserting a permanent marker element into the hydrogel.   
     
     
         18 . The method of  claim 17 , wherein the stress is induced in at least one of a radial direction, a height direction, and a width direction. 
     
     
         19 . The method of  claim 18 , wherein the stress is induced in both the height direction and the width direction. 
     
     
         20 . The method of  claim 17 , wherein the stress is induced using a mechanical force. 
     
     
         21 . The method of  claim 17 , wherein the stress is induced using a gravitational pull. 
     
     
         22 . The method of  claim 17 , wherein the step of forming the body of the biopsy site marker includes forming the hydrogel into an irregular shape configured to inhibit migration of the biopsy site marker when the biopsy site marker is disposed within tissue. 
     
     
         23 . The method of  claim 17 , wherein the step of inserting a permanent marker element includes inserting a helical coil into the hydrogel. 
     
     
         24 . A method for forming a biopsy site marker, the method comprising:
 (a) forming a bioabsorbable hydrogel into a marker body, the hydrogel having an elastic limit, the marker body defining a longitudinal axis;   (b) subjecting the bioabsorbable hydrogel to a curing process after formation of the marker body to transition the hydrogel from a liquid state to solid dry state;   (c) deforming the marker body transversely relative to the longitudinal axis during the curing process beyond the elastic limit of the hydrogel, thereby compressing a width defined by a portion of the marker body during the step of forming the marker body; and   (d) inserting a non-bioabsorbable marker element into the marker body such that the marker element is surrounded by the hydrogel.   
     
     
         25 . The method of  claim 24 , wherein the step of inserting the marker element includes centering the marker element within the marker body. 
     
     
         26 . The method of  claim 24 , further comprising inserting the cylindrical marker body into tissue to permit absorption of fluid into the hydrogel to thereby expand the diameter of the cylindrical marker body. 
     
     
         27 . The method of  claim 24 , where the step of deforming the marker body includes increasing a length of the marker body. 
     
     
         28 . The method of  claim 24 , wherein the step of forming the marker body includes forming a cylindrical shape with the hydrogel. 
     
     
         29 . A method for forming a hydrogel into a body of a biopsy site marker, the method comprising:
 (a) subjecting the hydrogel to a curing process to form the marker body, wherein the marker body defines a longitudinal axis, wherein the curing process includes dehydrating the hydrogel to transition the hydrogel from a liquid state to solid state;   (b) deforming a first portion of the marker body transversely relative to the longitudinal axis during the curing process, wherein the act of deforming includes exceeding an elastic limit of the hydrogel to thereby reduce a transverse dimension of the marker body; and   (c) inserting a metallic non-bioabsorbable marker element into the cylindrical marker body.   
     
     
         30 . The method of  claim 29 , wherein the reduction in the transverse dimension includes reducing the width of the first portion of the marker body. 
     
     
         31 . The method of  claim 29 , wherein marker body defines a cylindrical shape, wherein the reduction in the transverse dimension includes reducing the diameter of the first portion of the marker body.