Electromagnetic non-invasive measurement and monitoring system for osteoporosis

• US 4,850,372 A
• Filed: 08/25/1987
• Issued: 07/25/1989
• Est. Priority Date: 08/25/1987
• Status: Expired due to Fees

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Ko, Harvey W., Skura, Joseph P.
• Primary Examiner(s): Jaworski, Francis J.
• Assistant Examiner(s): Manuel, George
• Application Number:
  US07/089,193
• Time in Patent Office: 700 Days
• Field of Search: 128/804, 128/653, 128/734, 324/308, 324/321
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/4504 Bones A61B5/4547 takes precedence

Abstract

A method for noninvasively sensing bone mass loss associated with osteoporosis is disclosed. The method uses an electromagnetic field to measure impedance (or conductivity) changes in the bone. A decrease in conductivity is indicative of osteoporosis.

Claims

1. A method for monitoring osteoporosis, comprising the steps of:

noninvasively measuring the impedance an intact non-fractured of bone and other biological material in a region of a bone at plurality of different times;

said measuring step further comprising,

generating an oscillating near field magnetic flux that is spatially concentrated in said region of the bone thereby producing eddy currents primarily in bone and secondarily in other biological matter located in said region of the bone, such eddy currents inducing a secondary magnetic emission which varies in response primarily to the impedance of said bone and secondarily to other biological matter located in said region of said bone,

detecting said induced secondary magnetic emission and displaying an informational signal indicating the local impedance in said region of the bone; and

,

comparing said impedance measurements to monitor osteoporosis of the bone wherein a decrease in conductivity in said region of the bone is indicative of osteoporosis.

2. The method of claim 1, wherein noninvasively measuring impedance for each of said plurality of times comprises the following steps:

producing an oscillating magnetic field that is spatially concentrated in said region of the bone using a coil means, whereby eddy currents induced in bone and other biological matter will induce a secondary magnetic emission which alters the mutual inductance of said coil means in accordance with the impedance of bone and other biological matter is said region; and

,

detecting a change in said mutual inductance of said coil means, wherein an increase in mutual inductance indicates an increase in impedance and a decrease in mutual inductance indicate a decrease in impedance.

3. The method of claim 2, wherein said producing step comprises the step of exciting said coil means at a resonant frequency using an oscillator means, wherein said detecting step comprises the step of detecting changes in resonance caused by variations in said mutual inductance, wherein a higher resonant amplitude will indicate a higher impedance region.

4. A method of detecting osteoporosis, comprising the steps of:

noninvasively measuring the impedance of an intact non-fractured bone and other biological matter at a plurality of localized regions along a bone;

said measuring step for each of said plurality of localized regions further comprises,

generating a spatially concentrated oscillating near field magnetic flux at each particular region of said bone to induce eddy currents in bone and other biological matter within said region, such eddy currents inducing a secondary magnetic emission which varies in response to the impedance of bone and other biological matter within said region,

detecting said induced secondary magnetic emission and displaying an informational signal indicating the impedance detected at said region; and

,

comparing said impedance measurements with a normal conductivity profile to detect osteoporosis, wherein a drop-in conductivity below the normal conductivity profile is indicative of osteoporosis.

5. The method of claim 4, wherein noninvasively measuring impedance for each of said plurality of regions comprises the following steps:

producing an oscillating magnetic field that is spatially concentrated in a localized region along said bone using a coil means, whereby eddy currents induce a secondary magnetic emission which alters the mutual inductance of said coil means in accordance with the impedance of bone and other biological matter in said region; and

,

detecting a change in the mutual inductance of said coil means, wherein an increase in mutual inductance indicates an increase in impedance and a decrease in mutual inductance indicates a decrease in impedance.

6. The method of claim 5, wherein said producing steps comprise the step of exciting said coil means at a resonant frequency using an oscillator means, wherein said detecting step comprises the step of detecting changes in the resonance caused by variations in said mutual inductance.

7. A method for monitoring osteoporosis, comprising the steps of:

generating an oscillating near field magnetic flux that is spatially concentrated in an intact non-fractured region of a patient'"'"'s bone thereby producing eddy currents primarily in bone, such eddy currents inducing a secondary magnetic emission which varies in response primarily to the impedance of said bone; and

,

detecting said induced secondary magnetic emission and displaying an informational signal indicating local impedance in said region of the bone, wherein a decrease in impedance is indicative of a decrease in bone density and of osteoporosis.