Abstract:
A multi-layered structure in the form of a disposable patch is described for supporting a light source and useful in conjunction with procedures for the non-invasive visualization of veins, arteries or other subcutaneous structures of the body or for facilitating intravenous insertion or extraction of fluids, medication or the like, which in a representative embodiment includes a coupling layer for interfacing and optically coupling with the body surface and conforming to the surface topography of the body portion of interest, a ring for supporting a light source, and a reflective layer between the source and coupling layer for redirecting light reflected from the body surface back through the coupling layer.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/680,600 filed May 13, 2005. 
     
    
     RIGHTS OF THE GOVERNMENT  
       [0002]     The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates generally to medical devices and procedures, and more particularly to a disposable housing structure in the form of an adhesive patch structure for supporting a light source, such as an infrared light source, useful in conjunction with systems and methods for enhancing visualization of veins, arteries and other subcutaneous structures of the body in the administration of medical treatment to a patient.  
         [0004]     In the administration of medical care of a patient requiring vascular access, especially in an emergency situation, such as that encountered by a physician, nurse, emergency medical technician (EMT), or other health care provider, in the treatment of an accident victim at the scene of the accident, or by a medic in the treatment of the wounded on a battlefield, the conditions under which the care is administered may be adverse, such as nighttime lighting conditions. It is well settled that expeditious administration of medical care to the victim improves the prospects of recovery of the victim. For example, the life of a wounded soldier on the battlefield may depend on the immediate intravenous administration of blood plasma or other lost body fluids or of medications. Similar immediate procedures by a physician or EMT may be required in order to treat a victim at the scene of an accident. Further, during transport of the victim to a hospital or similar medical care facility, administration of medical procedures may be necessary under poor lighting conditions or under other adverse conditions (e.g., torn clothing, bleeding, etc) consequent of the accident. Shock may have caused the veins of the victim to partially collapse, or the patient may have veins which are difficult to find (such as in the treatment of infants or obese persons) which further complicates procedures for gaining access to the veins. The treatment of patients requiring vascular access in non-emergency situations may also be complicated by patient size, obesity, skin pigmentation or other physical characteristic.  
         [0005]     In the practice of the procedures for visualization of subcutaneous structures using either visible, infrared or near infrared light, proper support of the light source in order to accurately direct the light onto a body portion of interest may be an awkward procedure for the health care provider in treating a patient. There is therefore indicated a need for a hands-free device for supporting the light source and directing light from the source onto the body portion of interest in the imaging process.  
       SUMMARY OF THE INVENTION  
       [0006]     A multi-layered structure in the form of a disposable patch is described for supporting a light source and useful in conjunction with procedures for the non-invasive visualization of veins, arteries or other subcutaneous structures of the body or for facilitating intravenous insertion or extraction of fluids, medication or the like, which in a representative embodiment includes a coupling layer for interfacing and optically coupling with the body surface and conforming to the surface topography of the body portion of interest, a ring for supporting a light source, and a reflective layer between the source and coupling layer for redirecting light reflected from the body or scattered by the subcutaneous structures back through the coupling layer into the body surface under examination.  
         [0007]     The invention is particularly useful in conjunction with systems and methods for the detection and display of subcutaneous structures such as described in U.S. Pat. No. 6,230,046 to Crane et al, which describes system and method for enhancing the visualization of veins, arteries or other subcutaneous natural or foreign structures in the body and for facilitating intravenous insertion or extraction of fluids, medications or the like in the administration of medical treatment to a patient, including a light source of selected wavelength(s) for illuminating or transilluminating a selected portion of the body and a low-level light detector and suitable filters for generating an image of the illuminated body portion. Substantial background material useful in the understanding of the invention may be found by reference to U.S. Pat. No. 6,230,046 and to Publication Number US 2004/0215081.  
         [0008]     It is therefore a principal object of the invention to provide a housing structure for supporting a light source useful in the real-time, non-invasive visualization or identification of subcutaneous structures of the body.  
         [0009]     It is another object of the invention to provide a patch structure for supporting the light source in a hands free manner.  
         [0010]     It is yet another object of the invention to provide a patch structure adhesively attachable to a body portion of a patient.  
         [0011]     It is another object of the invention to provide a patch structure that can be applied to a body portion of the patient in close conformance to the topography of complex surface features of the body.  
         [0012]     It is yet another object of the invention to provide a patch structure that couples optically with the surface of the body portion of a patient in illuminating the body portion with light of selected wavelength.  
         [0013]     It is yet another object of the invention to provide a patch structure for use in medical imaging procedures that useful in scanning the surface of the body under examination with near infrared light in order to choose an optimum illumination position for the light source.  
         [0014]     These and other objects of the invention will become apparent as a detailed description of representative embodiments thereof proceeds. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The invention will be more clearly understood from the following detailed description of representative embodiments thereof read in conjunction with the accompanying drawing figure that shows an exploded view of a representative embodiment of the patch structure of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     Referring now to the accompanying drawing figure, shown therein in an exploded view are the essential elements of a patch  11  structure representative of the invention along with the supporting structural elements that render the structure a complete unit. In accordance with a principal feature of the invention, patch  11  is configured to facilitate the illumination of a body portion of a patient with visible (V), infrared (IR) or near infrared (nIR) light in the practice of a process for visualization of subcutaneous structures in the body. A first substantially optically transparent layer  12  is configured to interface with the surface of the body portion of interest to be illuminated. For the purpose of describing the invention and defining the scope thereof, the terms “optical” or “optically” shall, in accordance with customary usage, be defined to include the ultraviolet, visible, nIR and IR regions of the electromagnetic spectrum lying between about 0.1 to about 1500 microns.  
         [0017]     In order to minimize reflections at the interface and to efficiently illuminate the body surface with the available light from a suitable light source that is used in conjunction with the invention, the refractive index of layer  12  should be closely matched to the refractive index of the body portion of interest. The refractive index to infrared light of skin and tissue of the body is generally about 1.3 to 1.6. Accordingly, in contemplation of the invention, efficient coupling would result for a refractive index of layer  12  in the range of about 1.33 to 1.55. In order to efficiently couple light into the body surface, layer  12  should make substantially intimate laminar contact with the body surface in order to conform to various complex surface features of the skin, such as moles or hair, or various skin conditions such as acne, psoriasis, lesions, or other blemishes that would result in pockets or gaps of air in the interface that inhibit optical coupling with the body surface, and result in Fresnel reflections at the interface. Layer  12  should also provide a layer of thermal insulation between the light source and the surface of the skin so as to prevent discomfort to the patient or thermal damage to the skin, and to provide a sterile barrier between the light source should the patch or source need to be paced near or across a wound. Materials comprising layer  12  useful in the structure of patch  11  as an optical coupling layer and as a thermal diffuser include polyurethane, polyethylene, poly methacrylate, polyester, polydimethylsiloxane, a hydrocolloid gel or other highly transmissive, conformable material. Other materials may be selected by one skilled in the art guided by these teachings without departing from the spirit of the invention of the scope of the appended claims, material selection therefore not considered limiting of the invention herein. In the representative structure shown in the drawing that was built in demonstration of the invention, layer  12  comprised a thin layer (20 to 80 mils thick, preferably 30-50 mils) (1 mil=0.001 inch) of a hydrogel (such as Tegaderm™) as having good thermal insulative properties, good refractive match of approximately 1.33, and conforms well with the body surface contours. In the demonstration structure, layer  12  was about 41 mils thick and supported by a thin 1 mil thick film  13  of an IR transparent polymer having a suitable refractive index in the range of about 1.35 to 1.5, such polyethylene or polyurethane or other suitable elastomeric material such as polydimethylsiloxane, to protect layer  12  from tearing during use of the patch. Layer  12  may include an optional ring  14  of an IR opaque dye (e.g., Epolight™ 1175 or 1130 or ADS900AF) in order to prevent light scattering beyond the edges of coupling layer  12 .  
         [0018]     Structural support for layer  12  is provided by a pair of thin layer  16  (0.1 to 1 mil) and layer  17  (0.5 to 2 mils) of a structural polymer, such as polyethylene, polyurethane, polyethylene terephthalate (PET), polyethylene or polyurethane, each having a central opening for passing light through the structure to illuminate the body surface through layer  12 . Layer  16  is comprised of a high toughness, low strain to failure polymeric material to prevent the premature fracture or tearing of the thin reflective aluminum film described below in order to prevent leakage of light from layer  12  back through layers  16 ,  17 . Additionally, layers  16 ,  17  provide some structural rigidity to the overall structure of patch  11  while permitting layer  12  to conform to the body surface contour as just described.  
         [0019]     A reflective film can be included in the structure in order to direct back through coupling layer  12  light that might be reflected from the body surface at the coupling layer/body surface interface or from the subcutaneous structures being observed. In the structure of the embodiment shown in the drawing and built in demonstration of the invention, a reflective aluminum film  18  was supported on the underside of layer  16  for directing back through layer  12  light that is backscattered from the interface with the body surface. Aluminum film  18  also serve as a conductor of heat away from the light source. A special adhesive layer comprising ring  19  (such as Entrofilm 892 used in demonstration of the invention) provides adhesion between layer  13  supporting the hydrogel coupling layer and the reflective aluminum layer  18 . Structural support ring  21  (2 to 6 mils thick) of a synthetic polymeric or natural material was applied to polymer layer  17  for additional structural support. This support ring  21  permits the removal of layers  29  and  30  (described below) without wrinkling the other layers of the patch structure, thereby providing structural support for the patch after layers  29 ,  30  are removed when the patch is used as intended. Layer  17  may include high refractive index lines printed thereon to conduct light to the light source, which may contain circuits that control the light output of the source for optimum imaging; these lines may also be used to detect backscattered light to indicate presence of tissue or contact with the body surface as a safety feature against inadvertent heating of the body surface. The paths are high index lines (shown in the drawing as radially extending lines on layer  17 ) that are formed in the polymeric portion of layer  16  to provide light intensity values at various places of the patch/skin interface. It should be noted that the aluminum film may also be used to detect the presence of tissue via a change in capacitance caused by the presence with the intervening dielectric materials.  
         [0020]     A visible (V), IR or nIR light source  25  (such as one or more light emitting diodes, a chemiluminescent source or other suitable source, shown by dashed lines) may be inserted into and supported within two rings  26 ,  27  of foam, such as polyethylene foam and connected to a suitable source of power (not shown) for illumination of the body surface area of interest in accordance with the intended use of the invention. In an aspect of the invention contemplated herein, the light source  25  can include a disposable source, such as including a battery powered LED, for field or emergency usage. Foam layer  26  (abut 20 to 80 mils thick) provides primary support for the light source and may preferably comprise carbon filed polyethylene foam to prevent light leaks from the source. Foam layer  27  (about 0.5 to 4 mils thick) controls the adhesion of the two layer structure specifically to prevent layer  26  from sticking to the light source and to release the source when use of the patch is complete. As such, layer  27  must have a specific adhesion and thermal capabilities. The adhesion values of between 2 and 10 pound/linear inch with a value between 4 and 6 pound/linear inch peel will provide a suitable adhesion in contemplation of the invention. A protective pull-tab  29  comprising a protective contaminant barrier layer (1 to 5 mils thick, preferably 2 to 4 mils) of polyester or other suitable material is removed and discarded prior to attachment of source  25 . A second protective contaminant barrier layer  30  of a polymer (1 to 7 mils thick, preferably 2 to 4 mils) covers the under surface of patch  11  at layer  12  and is removed and discarded prior to the application of patch  11  to the skin of the subject. Layers  29 ,  30  should be nIR transparent with low scattering. In the demonstration embodiment, layers  29 ,  30  were each 3 mils thick. Prior to the removal of protective layer  30 , the patch structure may be used in a scanning mode to determine the optimum location for illuminating the intended cannulation site for placement of the patch in an imaging procedure.  
         [0021]     The patch structure according to the teachings of the invention may be of any convenient size consistent with the size of the person on which the patch is used, and thicknesses of the individual layers comprising the patch structure may be selected by the skilled artisan practicing the invention within the intended scope of these teachings, the thicknesses hereinabove recited as included in demonstration of the invention being representative only. It is noted further that the invention may find use in veterinary medicine as well as for human application. In the demonstration embodiment, overall size of the patch was about 2 to 6 inches in diameter and about 0.170 inch in overall thickness for use on an adult person. Minimum size of the patch may be limited by the size of the light source selected for use in conjunction with the patch and by the size of the body features of infant patients.  
         [0022]     The entire teachings of all references cited herein are incorporated herein by reference.  
         [0023]     The invention therefore provides a disposable patch structure for supporting a light source having particular application in systems and methods for enhanced visualization of subcutaneous structures. It is understood that modifications to the invention may be made as might occur to one with skill in the field of the invention within the scope of the appended claims. All embodiments contemplated hereunder that achieve the objects of the invention have therefore not been shown in complete detail. Other embodiments may be developed without departing from the spirit of the invention or from the scope of the appended claims.