Sem scanner sensing apparatus, system and methodology for early detection of ulcers

Abstract

A handheld, conforming capacitive sensing apparatus configured to measure Sub-Epidermal Moisture (SEM) as a mean to detect and monitor the formation of pressure ulcers. The device incorporates an array of electrodes which are excited to measure and scan SEM in a programmable and multiplexed manner by a battery-less RF-powered chip. The scanning operation is initiated by an interrogator which excites a coil embedded in the apparatus and provides the needed energy burst to support the scanning/reading operation. Each electrode measures the equivalent sub-epidermal capacitance corresponding and representing the moisture content.

What is claimed is: 
     
         1 . An apparatus for sensing sub-epidermal moisture from a location external to a patient's skin, comprising:
 a bipolar RF sensor embedded on a flexible substrate;   a conformal pressure pad disposed adjacent and underneath the substrate;   wherein the conformal pressure pad is configured to support the flexible substrate while allowing the flexible substrate to conform to a non-planar sensing surface of the patient's skin; and   interface electronics coupled to the sensor;   wherein said interface electronics are configured to control emission and reception of RF energy to interrogate the patient's skin.   
     
     
         2 . An apparatus as recited in  claim 1 , further comprising:
 an annular spacer adjacent and underneath the conformal pressure pad;   wherein the annular spacer comprises a central opening configured to allow the conformal pressure pad to deflect freely into the central opening.   
     
     
         3 . An apparatus as recited in  claim 1 , further comprising:
 an array of bipolar RF sensors spaced across the flexible substrate;   wherein each of the sensors is independently coupled to the interface electronics to independently interrogate the patient's skin.   
     
     
         4 . An apparatus as recited in  claim 3 :
 wherein each of the sensors is configured to measure an equivalent sub-epidermal capacitance of a target region of skin;   said sub-epidermal capacitance corresponding to the moisture content of the target region of skin.   
     
     
         5 . An apparatus as recited in  claim 4 :
 wherein the array of sensors comprises a first sensor having a first contact area and a second sensor having a second contact area larger than the first sensor; and   wherein the first and second sensors interrogate the skin at different depths.   
     
     
         6 . An apparatus as recited in  claim 4 :
 wherein the substrate comprises a substrate assembly comprising a substrate layer; and   wherein the sensor comprises a sensing pad having a first electrode embedded on a first side of the substrate and a second electrode embedded on a second side of the substrate.   
     
     
         7 . An apparatus as recited in  claim 6 , further comprising a biocompatible cover layer disposed over said first side of said substrate layer. 
     
     
         8 . An apparatus as recited in  claim 6 , further comprising a cover layer disposed under said second side of said substrate layer. 
     
     
         9 . An apparatus as recited in  claim 6 , further comprising:
 a stiffener layer disposed under said second side of said substrate layer;   wherein the stiffener layer comprises a footprint substantially similar to that of the sensor array.   
     
     
         10 . An apparatus as recited in  claim 6 :
 wherein said first electrode comprises an annular ring having an inner radius and an outer radius;   wherein said second electrode comprises an outer radius having a smaller diameter than the inner radius of the first electrode; and   wherein said second electrode is concentric with said first radius.   
     
     
         11 . An apparatus as recited in  claim 1 , wherein the interface electronics are configured to transmit data retrieved from said sensors. 
     
     
         12 . An apparatus as recited in  claim 4 , further comprising:
 a pressure sensor positioned in line with said RF sensor;   said pressure sensor configured to measure an applied pressure of the substrate at a location on the patient's skin.   
     
     
         13 . An apparatus as recited in  claim 1 , wherein the flexible substrate comprises Kapton or Polyimide. 
     
     
         14 . A scanner for sensing sub-epidermal moisture from a location external to a patient's skin, comprising:
 an array of bipolar RF sensors embedded on a flexible substrate; and   a conformal pressure pad disposed adjacent and underneath the substrate;   wherein the conformal pressure pad is configured to support the flexible substrate while allowing the flexible substrate to conform to a non-planar sensing surface of the patient's skin;   wherein said sensor array is configured to emit and receive RF energy to interrogate the patient's skin; and   wherein each of the sensors are independently are individually wired to independently interrogate the patient's skin.   
     
     
         15 . A scanner as recited in  claim 14 , further comprising:
 interface electronics coupled to the sensor;   wherein said interface electronics is configured to control the emission and reception of RF energy.   
     
     
         16 . A scanner as recited in  claim 14 , further comprising:
 an annular spacer adjacent and underneath the conformal pressure pad;   wherein the annular spacer comprises a central opening configured to allow the conformal pressure pad to deflect freely into the central opening.   
     
     
         17 . A scanner as recited in  claim 14 :
 wherein each of the sensors is configured to measure an equivalent sub-epidermal capacitance of a target region of skin;   said sub-epidermal capacitance corresponding to the moisture content of the target region of skin.   
     
     
         18 . A scanner as recited in  claim 14 :
 wherein the array of sensors comprises a first sensor having a first contact area and a second sensor having a second contact area larger than the first sensor; and   wherein the first and second sensors interrogate the skin at different depths.   
     
     
         19 . A scanner as recited in  claim 14 :
 wherein each sensor comprises a first electrode in the form of an annular ring having an inner radius and an outer radius and a second electrode comprising an outer radius having a smaller diameter than the first electrode; and   wherein said second electrode is concentric with said first radius.   
     
     
         20 . A scanner as recited in  claim 19 :
 wherein the substrate comprises a substrate assembly comprising a substrate layer; and   wherein the first electrode is embedded on a first side of the substrate and the second electrode embedded on a second side of the substrate.   
     
     
         21 . A scanner as recited in  claim 20 , further comprising:
 an upper biocompatible cover layer disposed over said first side of said substrate layer and a lower cover layer disposed under said second side of said substrate layer.   
     
     
         22 . A scanner as recited in  claim 20 , further comprising:
 a stiffener layer disposed under said second side of said substrate layer;   wherein the stiffener layer comprises a footprint substantially similar to that of the sensor array.   
     
     
         23 . A scanner as recited in  claim 14 , further comprising:
 an array of pressure sensors positioned in line with said RF sensor;   said pressure sensors are configured to measure an applied pressure of the substrate at corresponding locations on the patient's skin.   
     
     
         24 . A method for monitoring the formation of pressure ulcers at a target location of a patient's skin, comprising:
 positioning a flexible substrate adjacent the target location of the patient's skin;   the flexible substrate comprising one or more bipolar RF sensors;   conforming the flexible substrate to the patient's skin at the target location;   exciting the one or more bipolar RF sensors to emit RF energy into the patient's skin; and   measuring the capacitance of the skin at the target location as an indicator of the Sub-Epidermal Moisture (SEM) at the target location.   
     
     
         25 . A method as recited in  claim 24 :
 wherein the one or more sensors comprise an array of sensors disposed across said substrate; and   wherein the one or more sensors are individually controlled to independently excite the one or more sensors.   
     
     
         26 . A method as recited in  claim 24 , further comprising:
 measuring an applied pressure of the substrate at the target location on the patient's skin.   
     
     
         27 . A method as recited in  claim 25 , further comprising:
 measuring an applied pressure of the substrate on the patient's skin at each of the sensors in the array.