Method and apparatus for producing homogenous cavitation to enhance transdermal transport

Abstract

The present invention is directed to apparatus and methods for producing homogenous cavitation. An ultrasound souce comprising an ultrasound transmitting element having an axis and a cross-section along the axis is disclosed The ultrasound transmitting element also has a first axial end and a second axial end operable to produce ultrasonic waves. The cross-section has an area having a maximum value at the first axial end and a minimum value at the second axial end. A method for producing homogenous cavitation at an area of skin comprises creating a volume of fluid having a uniformly dispersed concentration of cavitation nuclei adjacent the area of skin. Ultrasound is then applied to the volume of fluid and causes cavitation at the cavitation nuclei.

1 . An ultrasound source comprising: 
 an ultrasound transmitting element having an axis and a first cross-section along said axis, said ultrasound transmitting element having a first axial end and a second axial end, said first axial end operable to produce ultrasonic waves; and    said first axial end comprising a matrix of ultrasound producing portions, said matrix having the first cross-section;    wherein said ultrasound producing portions are formed by making a first series of parallel axial cuts in the ultrasound transmitting element and a second series of parallel axial cuts in the ultrasound transmitting element, and wherein said first series of parallel axial cuts and said second series of parallel axial cuts are approximately perpendicular.    
     
     
         2 . The ultrasound source of  claim 1  wherein said ultrasound transmitting element comprises a cylindrical horn and said first cross-section is a circle.  
     
     
         3 . The ultrasound source of  claim 1  wherein said ultrasound transmitting element comprises a flat horn and said first cross-section is rectangular.  
     
     
         4 . The ultrasound source of  claim 3  wherein said matrix of ultrasound producing portions comprises a row of ultrasound producing portions.  
     
     
         5 . The ultrasound source of  claim 1  wherein each one of said ultrasound producing portions has a first end proximal to the ultrasound transmitting element, a second end distal to the ultrasound transmitting element and a cross-section.  
     
     
         6 . The ultrasound source of  claim 5  wherein at least one of said ultrasound producing portions comprises a cross-section having an area with a maximum value at the first end and an area with a minimum value at the second end.  
     
     
         7 . The ultrasound source of  claim 6  wherein at least one of said ultrasound producing portions has a circular cross-section.  
     
     
         8 . The ultrasound source of  claim 1  wherein the first end radiates ultrasound toward a skin surface and causes cavitation in the coupling medium, at the skin surface or in the skin.  
     
     
         9 . The ultrasound source of  claim 1  wherein said first end comprises an anodized coating.  
     
     
         10 . The ultrasound source of  claim 1  wherein said first end comprises carbide steel.  
     
     
         11 . The ultrasound source of  claim 10  wherein said carbide steel fist end is bonded to said ultrasound transmitting element.  
     
     
         12 . An ultrasound source comprising: 
 an ultrasound transmitting element having an axis and a cross-section along said axis, said ultrasound transmitting element having a first axial end and a second axial end, said second axial end operable to produce ultrasonic waves;    said cross-section having an area having a maximum value at the first axial end and a minimum value at the second axial end; and    said first axial end comprising a matrix of ultrasound producing portions, said matrix having the first cross-section;    wherein said ultrasound producing portions are formed by malting a first series of parallel axial cuts in the ultrasound transmitting element and a second series of parallel axial cuts in the ultrasound transmitting element, and wherein said first series of parallel axial cuts and said second series of parallel axial cuts are approximately perpendicular.    
     
     
         13 . The ultrasound source of  claim 12  wherein said cross-section has a uniform shape and an area that decreases from a maximum value at the first axial end to a minimum value at the second axial end.  
     
     
         14 . The ultrasound source of  claim 12  wherein said ultrasound transmitting element has a circular cross-section along said axis.  
     
     
         15 . The ultrasound source of  claim 12  wherein the ultrasound transmitting element produces an ultrasound wave pattern that produces uniformly distributed cavitation.  
     
     
         16 . The ultrasound source of  claim 12  wherein the first axial end radiates ultrasound toward a skin surface and causes uniformly distributed cavitation in the coupling medium, at the skin surface or in the skin.  
     
     
         17 . The ultrasound source of  claim 12  wherein said first end comprises an anodized coating.  
     
     
         18 . The ultrasound source of  claim 12  wherein said first end comprises carbide steel.  
     
     
         19 . The ultrasound source of  claim 18  wherein said carbide steel first end is bonded to said ultrasound transmitting element.  
     
     
         20 . A method for producing homogenous cavitation at an area of skin comprising: 
 creating a volume of fluid adjacent the area of skin, said fluid having a uniformly dispersed concentration of cavitation nuclei therein; and    applying ultrasound to the volume of fluid from an ultrasound transmitting element having an axis and a cross-section along said axis, said ultrasound transmitting element having a first axial end and a second axial end, said second axial end operable to produce ultrasonic waves, said first axial end comprising a matrix of ultrasound producing portions, said matrix having the first cross-section, wherein said ultrasound producing portions are formed by making a first series of parallel axial cuts in the ultrasound transmitting element and a second series of parallel axial cuts in the ultrasound transmitting element, and wherein said first series of parallel axial cuts and said second series of parallel axial cuts are approximately perpendicular;    wherein the ultrasound causes cavitation to begin at or around the cavitation nuclei.    
     
     
         21 . The method of  claim 20  wherein the cavitation nuclei comprise appropriately sized ceramic particles.  
     
     
         22 . The method of  claim 20  wherein the cavitation nuclei comprise appropriately sized polymer particles.  
     
     
         23 . The method of  claim 20  wherein the cavitation nuclei comprise appropriately sized titanium dioxide particles.  
     
     
         24 . The method of  claim 20  wherein the cavitation nuclei comprises gas bubbles.  
     
     
         25 . The method of  claim 20  further comprising delivering a substance through the area of skin.  
     
     
         26 . The method of  claim 20  further comprising extracting analyte through the area of skin.  
     
     
         27 . A method for producing homogenous cavitation at an area of skin comprising: 
 creating a volume of fluid adjacent the area of skin, said fluid having a uniformly dispersed concentration of a fluorocarbon therein, said fluorocarbon facilitating the production of cavitation; and    applying ultrasound to the volume of fluid;    wherein the ultrasound causes cavitation in the fluid, evaporation of the fluorocarbon and the creation of gas bubbles in the coupling medium.    
     
     
         28 . The method of  claim 27  further comprising delivering a substance through the area of skin.  
     
     
         29 . The method of  claim 27  further comprising extracting analyte through the area of skin.  
     
     
         30 . A method for producing homogenous cavitation at an area of skin comprising: 
 creating a volume of fluid adjacent the area of skin, said fluid having a uniformly dispersed concentration of a first substance therein, said first substance facilitating the production of cavitation;    applying ultrasound to the volume of fluid;    wherein the ultrasound causes cavitation in the fluid; and wherein the first substance is a surfactant that facilitates the occurrence of cavitation when the coupling fluid is exposed to ultrasound.    
     
     
         32 . The method of  claim 30  further comprising delivering a substance through the area of skin.  
     
     
         33 . The method of  claim 30  further comprising extracting analyte through the area of skin.  
     
     
         34 . A method for producing homogenous cavitation at an area of skin comprising: 
 providing an ultrasound source to apply an ultrasonic wave to the area of skin;    positioning a screen between the area of skin and the ultrasound source, the screen having a number of openings therein; and,    applying ultrasound to the area of skin through the screen;    wherein the openings in the screen nucleate cavitation and filter cavitation bubbles by size thereby producing a homogenous bubble population.    
     
     
         35 . The method of  claim 34  further comprising delivering a substance through the area of skin.  
     
     
         36 . The method of  claim 34  further comprising extracting analyte-through the area of skin.  
     
     
         37 . An ultrasound device comprising: 
 an ultrasound horn; and    a housing for said ultrasound horn, a portion of said housing having a reduced inside diameter relative to a diameter of said horn;    a screen positioned between an area of skin and the ultrasound horn, the screen having a number of openings therein;    wherein the reduced inside diameter focuses ultrasonic energy on a small area of skin; and    
     
     
         38 . The ultrasound device of  claim 37 , wherein said reduced inside diameter is located near the skin.  
     
     
         39 . The ultrasound device of  claim 37 , further comprising 
 a coupling medium contained in said housing.