Rapid and Accurate Detection of Bone Quality Using Ultrasound Critical Angle Reflectometry

Abstract

The present invention is an apparatus, method and system for determining the coefficient of elasticity of a target by detecting an ultracritical reflection of ultrasound waves directed at the target using an ultrasound transducer at two or more angles simultaneously and calculating the elasticity coefficient of the target.

1 . A method for determining an elasticity coefficient of a target, comprising the steps of:
 determining simultaneously two or more critical-angle reflections of an ultrasound wave from the target using an ultrasound transducer comprising a transmitter and two or more receivers; and   calculating the elasticity coefficients of the target.   
   
   
       2 . The method of  claim 1 , wherein the target comprises bone. 
   
   
       3 . The method of  claim 1 , wherein the target comprises human bone. 
   
   
       4 . The method of  claim 1 , wherein the target comprises a human bone from a human being suffering from or suspected of having osteoporosis. 
   
   
       5 . The method of  claim 1 , wherein the target comprises bone from a human being suffering from or suspected of having osteoporosis under treatment with bisphosphonate. 
   
   
       6 . The method of  claim 1 , wherein the detection step is non-invasive. 
   
   
       7 . The method of  claim 1 , wherein one or more elasticity coefficients are determined from the square of ultrasound velocity as determined from the identified critical angle. 
   
   
       8 . The method of  claim 1 , further comprising the steps of:
 determining a maximum elasticity coefficient and a minimum elasticity coefficient to estimate a degree of target anisotropy; and   using the critical-angle reflection values detected at multiple rotational orientations from the ultrasound transducer fixed at a position normal to a bone surface.   
   
   
       9 . The method of  claim 2 , further comprising the step of determining a maximum elasticity coefficient and a minimum elasticity coefficient to estimate a degree of bone anisotropy. 
   
   
       10 . The method of  claim 1 , further comprising the step of automating the determination of the normal of the transducer to the target. 
   
   
       11 . The method of  claim 1 , wherein the step of detecting simultaneously is further defined as comprising the simultaneous reception from 2, 4, 8, 16, 24, 36, 48, 64 or 128 receivers. 
   
   
       12 . The method of  claim 1 , further comprising the step of storing the critical-angle values detected in the reflection of an ultrasound wave at two or more receivers that are concentric with a transmitter. 
   
   
       13 . The method of  claim 1 , further comprising the steps of:
 storing the detected critical-angle reflections of ultrasound waves at different points in time; and   comparing the measurements to track changes in the coefficient of elasticity of the target.   
   
   
       14 . The method of  claim 1 , wherein the step of detecting at two or more angles uses a transducer head comprising at least one transmitter and two or more receivers that detect simultaneously the reflected ultrasound energy from the target, wherein the transmitter and the two or more transducers have a common focal point. 
   
   
       15 . The method of  claim 1 , wherein the transmitter is concave. 
   
   
       16 . The method of  claim 1 , wherein the two or more receivers for part of a concave array in at least two dimensions. 
   
   
       17 . The method of  claim 1 , wherein the transmitter and the two or more receivers are concave and concentric. 
   
   
       18 . The method of  claim 1 , wherein the transmitter is concave and the two or more receivers are concave and the transmitter and the two or more receivers are concentric about a common focal point. 
   
   
       19 . The method of  claim 1 , wherein the receivers are further defined as a receiving array and the array comprises 48 independent receiving transducers that are concentric and concave and share a focal point with the transmitter. 
   
   
       20 . The method of  claim 4 , wherein the human has bone disease, a bone-losing condition other than osteoporosis, or a condition suspected of causing inferior bone strength. 
   
   
       21 . The method of  claim 5 , wherein the treatment of osteoporosis comprises drugs other than bisphosphonate, e.g., an estrogen, an estrogen analog, a parathyroid hormone peptide, a fluoride, a vitamin D, and a calcitonin. 
   
   
       22 . The method of  claim 5 , wherein the treatment is suspected of causing bone loss. 
   
   
       23 . The method of  claim 5 , wherein the treatment is suspected of causing bone loss caused by a steroid or anticonvulsant. 
   
   
       24 . The method of  claim 5 , wherein the step of detecting simultaneously two or more critical-angle reflections of an ultrasound wave from the target is taken prior to initiation of bisphosphonate treatment, in order to identify patients with inferior bone quality in whom bisphosphonate should be used with caution. 
   
   
       25 . A method for determining the effect on a coefficient of elasticity of bone from a patient undergoing treatment for osteoporosis, comprising the steps of:
 detecting simultaneously at two or more angles the critical-angle reflections of ultrasound waves directed at a bone using an ultrasound transducer with one or more transmitters and two or more receivers; and   calculating the anisotropy of the bone from the ratio of a maximum elasticity coefficient and a minimum elasticity coefficient, wherein elasticity coefficients are derived as the square of the velocities of an ultrasound waves as determined from the critical angle.   
   
   
       26 . The method of  claim 25 , further comprising the steps of:
 storing a first detected critical-angle reflection of ultrasound waves at two or more receivers prior to, or concurrent with, treatment with a bisphosphonate or derivative thereof   storing a second detected critical-angle reflection of ultrasound waves at two or more receivers after a period of time; and   comparing the first and second measurements to track changes in the elasticity coefficient of the bone during treatment with the bisphosphonate or derivative thereof.   
   
   
       27 . The method of  claim 25 , wherein the step of detecting simultaneously at two or more angles the critical-angle reflection of ultrasound waves directed at a bone using an ultrasound transducer further comprises measuring a maximum and a minimum elasticity of a cortical and a trabecular region of the bone; and
 estimating the anisotropy of the bone in vivo.   
   
   
       28 . The method of  claim 27 , wherein determining the elasticity of cortical bone, trabecular bone, and anisotropy of a patient's bone is non-invasive. 
   
   
       29 . The method of  claim 28 , wherein the measurement of elasticity is at a heel. 
   
   
       30 . The method of  claim 28 , wherein the step of calculating the anisotropy of the bone further comprises determining the maximum and the minimum elasticity coefficient of a cortical and a trabecular bone region, wherein the measurements correspond to an axis of a weight-bearing and a non-weight-bearing bone, respectively. 
   
   
       31 . The method of  claim 25 , wherein the patient has bone disease, a bone-losing condition other than osteoporosis, or a condition suspected of causing inferior bone strength. 
   
   
       32 . The method of  claim 26 , wherein the treatment of osteoporosis comprises an estrogen, an estrogen analog, a parathyroid hormone peptide, a fluoride, a vitamin D, and a calcitonin. 
   
   
       33 . The method of  claim 26 , wherein the treatment is suspected of causing bone loss caused by steroid or anticonvulsant. 
   
   
       34 . The method of  claim 26 , wherein the step of detecting simultaneously two or more critical-angle reflections of an ultrasound wave from the target is prior to initiation of bisphosphonate treatment, in order to identify patients with inferior bone quality in whom bisphosphonate should be used with caution. 
   
   
       35 .- 84 . (canceled) 
   
   
       85 . A method for simultaneously measuring maximum and minimum elasticity coefficients and anisotropy of bone non-invasively in vivo in accordance with the method of  claim 1 . 
   
   
       86 . A method for taking simultaneous measurements of maximum and minimum elasticity coefficients and anisotropy of cortical and trabecular bone non-invasively in vivo in accordance with the method of  claim 25 . 
   
   
       87 - 89 . (canceled)