Tissue mimicking elastography phantoms

Abstract

Tissue mimicking materials for elastography phantoms have elastic, ultrasound, and magnetic resonance characteristics that are characteristic of human soft tissues and well suited for the calibration and performance assessment of elastography imaging systems. In one embodiment, the material is formed from a base material containing an oil dispersed within a gel matrix and at least one inclusion formed from a gel. In another embodiment, the material is formed from a gel-forming material suffused throughout an open-cell reticulated mesh matrix.

What is claimed is:  
     
         1 . A tissue mimicking material for testing elastography imagers, comprising: 
 (a) a base material comprising an oil dispersed throughout a gel matrix formed from a gel-forming material; and    (b) at least one inclusion of a defined shape at least partially surrounded by the base material, the inclusion comprising the same gel-forming material as the base material, wherein the elastic contrast between the base material and the at least one inclusion is such that the elastic contrast between normal soft tissue and abnormal soft tissue is mimicked, making the tissue mimicking material suitable for use in testing elastography imagers.    
     
     
         2 . The tissue mimicking material of  claim 1  wherein the elastic contrast between the base material and the at least one inclusion is between about 1 and about 4.  
     
     
         3 . The tissue mimicking material of  claim 1  wherein the elastic contrast between the base material and the at least one inclusion is between about 1 and about 3.  
     
     
         4 . The tissue mimicking material of  claim 1  wherein the base material is elastically linear for strains of up to about 10 percent.  
     
     
         5 . The tissue mimicking material of  claim 1  wherein the speed of sound in the base material and the at least one inclusion is between about 1300 m/s and about 1650 m/s.  
     
     
         6 . The tissue mimicking material of  claim 1  wherein the T1 values of the base material and the at least one inclusion are between about 200 ms and about 1200 ms, and the T2 values of the base material and the at least one inclusion are between about 40 ms and about 700 ms.  
     
     
         7 . The tissue mimicking material of  claim 1  wherein the elastic contrast between the base material and the at least one inclusion varies by less than about 20% over a period of at least six months.  
     
     
         8 . The tissue mimicking material of  claim 1  wherein the gel-forming material comprises gelatin or a mixture of agar and gelatin.  
     
     
         9 . The tissue mimicking material of  claim 1  wherein the base material and the at least one inclusion both comprise an oil-in-gelatin dispersion and further wherein the concentration of oil in the base material differs from the concentration of oil in the at least one inclusion.  
     
     
         10 . The tissue mimicking material of  claim 1  wherein the gel-forming material in at least one of the base material or the at least one inclusion further comprises at least one additional additive selected from the group consisting of a crosslinking agent, an organic hydroxy compound, microscopic solid particles, a copper salt, a chelating agent, and an agent for inhibiting attack by microorganisms.  
     
     
         11 . The tissue mimicking material of  claim 1  wherein the oil is selected from the group consisting of safflower oil, olive oil, castor oil, and kerosene.  
     
     
         12 . An abnormal tissue mimicking material for testing elastography imagers comprising an open-cell reticulated mesh material and a gel-forming material suffused into the mesh material, wherein the Young's modulus of the abnormal tissue mimicking material mimics the Young's modulus of abnormal soft tissue.  
     
     
         13 . The abnormal tissue mimicking material of  claim 12  wherein the Young's modulus of the abnormal tissue mimicking material is between about 10 and about 300 kPa.  
     
     
         14 . The abnormal tissue mimicking material of  claim 12  wherein the open-cell reticulated mesh material is a polyether mesh or a polyurethane mesh.  
     
     
         15 . The abnormal tissue mimicking material of  claim 12  wherein the open-cell reticulated mesh material comprises between about 10 and about 30 cells per inch.  
     
     
         16 . The abnormal tissue mimicking material of  claim 12  wherein the gel-forming material comprises a material selected from the group consisting of gelatin, agar, a mixture of gelatin and agar, an emulsion of oil-in-gelatin, and an emulsion of oil in a mixture of agar and gelatin.  
     
     
         17 . The abnormal tissue mimicking material of  claim 12  wherein the gel-forming material comprises agar.  
     
     
         18 . The abnormal tissue mimicking material of  claim 17  wherein the material is elastically nonlinear for strains of up to about 10 percent.  
     
     
         19 . The abnormal tissue mimicking material of  claim 12  wherein the gel-forming material further comprises at least one additional additive selected from the group consisting of a crosslinking agent, an organic hydroxy compound, microscopic solid particles, a copper salt, a chelating agent, and an agent for inhibiting attack by microorganisms.  
     
     
         20 . The abnormal tissue mimicking material of  claim 12  wherein the gel-forming material comprises an inner volume comprising agar suffused into the mesh material and an outer shell comprising gelatin suffused into the mesh material, wherein the outer shell surrounds the inner volume.  
     
     
         21 . The abnormal tissue mimicking material of  claim 20  wherein the outer shell comprises a mixture of agar and gelatin.  
     
     
         22 . The abnormal tissue mimicking material of  claim 22  wherein the inner volume is substantially spherically shaped and the outer shell has a plurality of spicules extending outward away from the inner volume.  
     
     
         23 . A tissue mimicking material for testing elastography imagers, comprising: 
 (a) a base material comprising a gel-forming material; and    (b) at least one inclusion comprising the abnormal tissue mimicking material  claim 12  at least partially surrounded by the base material, wherein the elastic contrast between the base material and the at least one inclusion is such that the elastic contrast between normal soft tissue and abnormal soft tissue is mimicked, making the tissue mimicking material suitable for use in testing elastography imagers.    
     
     
         24 . The tissue mimicking material of  claim 23  wherein the elastic contrast between the base material and the at least one inclusion is between about 1 and about 4.  
     
     
         25 . The tissue mimicking material of  claim 23  wherein the elastic contrast between the base material and the at least one inclusion is between about 1 and about 3.  
     
     
         26 . The tissue mimicking material of  claim 23  wherein the speed of sound in the base material and the at least one inclusion is between about 1300 and 1650 m/s.  
     
     
         27 . The tissue mimicking material of  claim 23  wherein the T1 values of the base material and the at least one inclusion are between about 200 ms and about 1200 ms and the T2 values of the base material and the at least one inclusion are between about 40 ms and about 200 ms.  
     
     
         28 . The tissue mimicking material of  claim 23  wherein the elastic contrast between the base material and the at least one inclusion varies by less than about 20% over a period of at least six months.  
     
     
         29 . The tissue mimicking material of  claim 23  wherein the gel-forming material in the base material is selected from the group consisting of gelatin, agar, or a mixture of gelatin and agar.  
     
     
         30 . An elastography phantom comprising: 
 (a) an elastography phantom container enclosing an interior space; and    (b) the tissue mimicking material of  claim 1  contained within the interior space of the container.    
     
     
         31 . An elastography phantom comprising: 
 (a) an elastography phantom container enclosing an interior space; and    (b) the tissue mimicking material of  claim 23  contained within the interior space of the container.    
     
     
         32 . A method for testing an elastography imager comprising, mapping local elastic strains of a tissue mimicking material to obtain a elastogram of the tissue mimicking material, the tissue mimicking material comprising: 
 (i) a base material comprising an oil dispersed throughout a gel matrix formed from a gel-forming material; and    (ii) at least one inclusion of a defined shape at least partially surrounded by the base material, the inclusion comprising the same gel-forming material as the base material, wherein the elastic contrast between the base material and the at least one inclusion is such that the elastic contrast between normal soft tissue and abnormal soft tissue is mimicked.    
     
     
         33 . The method of  claim 32  wherein the elastogram is an ultrasound elastogram or a magnetic resonance elastogram.  
     
     
         34 . A method for testing an elastography imager comprising, mapping local elastic strains of a tissue mimicking material to obtain a elastogram of the tissue mimicking material, the tissue mimicking material comprising: 
 (i) a base material comprising a gel-forming material; and    (ii) at least one inclusion of a defined shape at least partially surrounded by the base material, the at least one inclusion comprising an open-cell reticulated mesh material and a gel-forming material suffused into the mesh material, wherein the elastic contrast between the base material and the at least one inclusion is such that the elastic contrast between normal soft tissue and abnormal soft tissue is mimicked.    
     
     
         35 . The method of  claim 34  wherein the elastogram is an ultrasound elastogram or a magnetic resonance elastogram.