Diagnostic and monitoring electrical impedance tomography (eit) system for osteoporosis

Abstract

A method of measuring Bone Mineral Density (BMD) including providing a model of a plurality of constituents of at least a portion of a subject body, the model including at least one bone constituent, injecting electric current into the portion of the subject body using a current injection electrode, such that at least part of the current flows through the at least one bone constituent, measuring a value of electric potential at a surface of the subject body using a pickup electrode, using a value of the injected electric current as input to a model of the at least a portion of a subject body, and calculating a value of conductance of the bone constituent corresponding to a value of the injected electric current and the measured value of the electric potential. Related apparatus and methods are also described.

What is claimed is: 
     
         1 . A system for measuring Bone Mineral Density (BMD) comprising:
 a plurality of injection electrodes for injecting electric current into a portion of a subject, such that at least part of the current flows through at least one bone constituent;   a plurality of pickup electrodes for measuring a value of electric potential at a surface of the subject;   an attachment device for attaching electrodes to a body part, the electrodes attached to the attachment device and placing at least some of the electrodes in a specific geometric relation to each other; and   a computational unit;   wherein the computational unit is configured to:   receive input of measured values of electric potential at the surface of the subject;   use the measured values of electric potential to estimate the subject's Bone Mineral Density (BMD).   
     
     
         2 . The system of  claim 1  in which the attachment device is configured to fit over a wrist. 
     
     
         3 . The system of  claim 2  in which the attachment device is configured in a shape which locates the electrodes surrounding the wrist. 
     
     
         4 . The system of  claim 1  in which the attachment device comprises a sleeve. 
     
     
         5 . The system of  claim 1  in which the attachment device comprises a sleeve for sliding over a patient's body part. 
     
     
         6 . The system of  claim 1  wherein the computational unit is configured to:
 calculate a value of conductance of the at least one bone constituent based on the input; and 
 calculate the subject's Bone Mineral Density (BMD) based on the value of conductance of the bone constituent. 
 
     
     
         7 . The system of  claim 1  in which at least one of the electrodes is an active electrode. 
     
     
         8 . The system of  claim 1  in which one or more of the injection electrodes which inject the current are also used as pickup electrodes to measure the potential. 
     
     
         9 . The system of  claim 2  in which the attachment device is configured in a shape which enables placing the attachment device at a specific location on the wrist. 
     
     
         10 . The system of  claim 2  in which the attachment device has the electrodes attached to the attachment device positioned to place the injection electrodes and the pickup electrodes at specific locations on the wrist. 
     
     
         11 . The system of  claim 1  in which the attachment device comprises 4 or 5 electrodes. 
     
     
         12 . The system of  claim 1  in which at least some of the electrodes are arranged in an arrangement selected from a group consisting of:
 a line; 
 an array; and 
 a ring. 
 
     
     
         13 . A method of measuring Bone Mineral Density (BMD) comprising:
 injecting electric current into a portion of a subject body using a plurality of current injection electrodes, such that at least part of the current flows through at least one bone constituent;   measuring a plurality of values of electric potential at a surface of the subject body using a plurality of pickup electrodes;   using the measured values of the electric potential to estimate the subject's Bone Mineral Density (BMD) based on an Electrical Impedance model of at least a portion of the subject's body.   
     
     
         14 . The method of  claim 13  and further comprising placing the current injection electrodes and the pickup electrodes on the portion of the subject body using an attachment device shaped to fit the portion of the subject body. 
     
     
         15 . The method of  claim 14  and in which the attachment device is configured to fit over a wrist. 
     
     
         16 . The method of  claim 14  in which the placing the current injection electrodes and the pickup electrodes on the portion of the subject body comprises placing the electrodes at locations on the wrist. 
     
     
         17 . The method of  claim 14  and in which the attachment device is a sleeve. 
     
     
         18 . The method of  claim 13  in which the bone constituent comprises a long bone. 
     
     
         19 . The method of  claim 13  in which the plurality of current injection electrodes are arranged in an arrangement selected from a group consisting of:
 a line along the bone constituent; 
 an array adjacent to the bone constituent; and 
 a ring adjacent to the bone constituent. 
 
     
     
         20 . The method of  claim 14  in which the plurality of pickup electrodes are arranged in an arrangement selected from a group consisting of:
 a line along the bone constituent; 
 an array adjacent to the bone constituent; and 
 a ring adjacent to the bone constituent.