Ultrasonic bone assessment method and apparatus
First Claim
Patent Images
1. A method of non-invasive and quantitative assessment of the status of bone tissue in vivo for one or more of the quantities:
- bone-mineral density, strength, and fracture risk, comprising the steps of;
(a) acoustically coupling a pair of transducers to nearby skin on opposite sides of said bone tissue;
(b) generating an ultrasound excitation signal and directing same from one transducer to another transducer of said pair of transducers through said bone tissue, thereby producing a bone-oriented electrical output signal of the form of zs (t)=ps (t)+ns (t), where ps (t) is said bone-oriented output signal per se and ns (t) is an additive, uncorrelated Gaussian measurement noise associated with said bone-oriented signal, said excitation signal being a finite-duration signal repeated substantially in a range from 1 to 1000 Hz and consisting of plural frequencies spaced in an ultrasonic spectral region up to about 2 MHz;
(c) independently directing said excitation signal from said one transducer to said another transducer through a medium with known acoustic properties and path length and free of said bone tissue, thereby producing a reference electrical output signal of the form of zr (t)=pr (t)+nr (t), where pr (t) is said reference output signal per se and nr (t) is an additive, uncorrelated Gaussian measurement noise associated with said reference signal;
(d) parametric modeling said bone-oriented signal and said reference signal, with obtaining two parametric models thereof, ps (t) and pt (t), respectively, to thereby establish a set Θ
s of bone-oriented parameters and a set Θ
r of reference parameters correspondingly associated with said models, and(e) subjecting said two sets of parameters to comparative analysis, whereby an estimate of said one or more quantities is obtained.
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Abstract
A method for assessment of bone properties comprises passing ultrasonic signal through a bone tissue, modeling an output signal and a reference output signal and subjecting parameters of the models to comparative analysis. An apparatus is also disclosed for practicing the method.
123 Citations
46 Claims
-
1. A method of non-invasive and quantitative assessment of the status of bone tissue in vivo for one or more of the quantities:
- bone-mineral density, strength, and fracture risk, comprising the steps of;
(a) acoustically coupling a pair of transducers to nearby skin on opposite sides of said bone tissue; (b) generating an ultrasound excitation signal and directing same from one transducer to another transducer of said pair of transducers through said bone tissue, thereby producing a bone-oriented electrical output signal of the form of zs (t)=ps (t)+ns (t), where ps (t) is said bone-oriented output signal per se and ns (t) is an additive, uncorrelated Gaussian measurement noise associated with said bone-oriented signal, said excitation signal being a finite-duration signal repeated substantially in a range from 1 to 1000 Hz and consisting of plural frequencies spaced in an ultrasonic spectral region up to about 2 MHz; (c) independently directing said excitation signal from said one transducer to said another transducer through a medium with known acoustic properties and path length and free of said bone tissue, thereby producing a reference electrical output signal of the form of zr (t)=pr (t)+nr (t), where pr (t) is said reference output signal per se and nr (t) is an additive, uncorrelated Gaussian measurement noise associated with said reference signal; (d) parametric modeling said bone-oriented signal and said reference signal, with obtaining two parametric models thereof, ps (t) and pt (t), respectively, to thereby establish a set Θ
s of bone-oriented parameters and a set Θ
r of reference parameters correspondingly associated with said models, and(e) subjecting said two sets of parameters to comparative analysis, whereby an estimate of said one or more quantities is obtained. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
- 3. The method according to claim 1, wherein said parametric model of said bone-oriented output signal has the form of
- space="preserve" listing-type="equation">p.sub.s (t)=(K.sub.s0 +K.sub.s1 (t-τ
.sub.s)+ . . . +K.sub.sm (t-τ
.sub.s).sup.m) exp[-b.sub.s (t-τ
.sub.s).sup.2 ]sin[2π
ƒ
.sub.s (t-τ
.sub.s)]
said set of bone-oriented parameters, Θ
s, being {Ks0, Ks1, . . . , Ksm, bs, ƒ
s, τ
s }. - space="preserve" listing-type="equation">p.sub.s (t)=(K.sub.s0 +K.sub.s1 (t-τ
- bone-mineral density, strength, and fracture risk, comprising the steps of;
- 4. The method according to claim 2, wherein said parametric model of said bone-oriented output signal has the form of
- space="preserve" listing-type="equation">p.sub.s (t)=(A.sub.s0 +A.sub.s1 (t-τ
.sub.s)+A.sub.s2 (t-τ
.sub.s).sup.2) exp[-a.sub.s (t-τ
.sub.s)]sin[2π
ƒ
.sub.s (t-τ
.sub.s)]
said set of bone-oriented parameters, Θ
s, being {As0, As1, As2, as, ƒ
s, τ
s }. - space="preserve" listing-type="equation">p.sub.s (t)=(A.sub.s0 +A.sub.s1 (t-τ
- space="preserve" listing-type="equation">p.sub.s (t)=(K.sub.s0 +K.sub.s1 (t-τ
.sub.s)+K.sub.s2 (t-τ
.sub.s).sup.2) exp[-b.sub.s (t-τ
.sub.s).sup.2 ]sin[2π
ƒ
.sub.s (t-τ
.sub.s)]
s, being {Ks0, Ks1, Ks2, bs, ƒ
s, τ
s }.
- space="preserve" listing-type="equation">p.sub.r (t)=(A.sub.r0 +A.sub.r1 (t-τ
.sub.r)+ . . . +A.sub.rj (t-τ
.sub.r).sup.j) exp[-a.sub.r (t-τ
.sub.r)]sin[2π
ƒ
.sub.r (t-τ
.sub.r)]
τ
r, and zero otherwise, said set, Θ
r of reference parameters being {Ar0, Ar1, . . . Arj, ar, ƒ
r, τ
r }.
- space="preserve" listing-type="equation">p.sub.r (t)=(K.sub.r0 +K.sub.r1 (t-τ
.sub.r)+ . . . +K.sub.rq (t-τ
.sub.r).sup.q) exp[-b.sub.r (t-τ
.sub.r).sup.2 ]sin[2π
ƒ
.sub.r (t-τ
.sub.r)]
r, being {Kr0, Kr1, . . . , Krq, br, ƒ
r, τ
r }.
- space="preserve" listing-type="equation">p.sub.r (t)=(A.sub.r0 +A.sub.r1 (t-τ
.sub.r)+A.sub.r2 (t-τ
.sub.r).sup.2) exp[-a.sub.r (t-τ
.sub.r)]sin[2π
ƒ
.sub.r (t-τ
.sub.r)]
r, being {Ar0, Ar1, Ar2, ar, ƒ
r, τ
r }.
- space="preserve" listing-type="equation">p.sub.r (t)=(K.sub.r0 +K.sub.r1 (t-τ
.sub.r)+K.sub.r2 (t-τ
.sub.r).sup.2) exp[-b.sub.r (t-τ
.sub.r).sup.2 ]sin[2π
ƒ
.sub.r (t-τ
.sub.r)]
r, being {Kr0, Kr1, Kr2, br, ƒ
r, τ
r }.
-
s of bone-oriented parameters is estimated with the use of a least square optimization algorithm, to thereby provide a maximum likelihood estimate Θ
s,ML defined as ##EQU5## where argmin denotes a value of said bone-oriented parameters which provides a smallest value of said sum Σ
.
-
r of reference parameters is estimated with the use of a least square optimization algorithm, to thereby provide a maximum likelihood estimate Θ
r,ML defined as ##EQU6## where argmin denotes a value of said reference parameters which provides a smallest value of said sum Σ
.
- age, bony member thickness, sex, height, weight specific for an individual patient.
- age, bone tissue thickness, sex, height, weight, specific for an individual patient, input to said preprocessing step.
-
19. A method of non-invasive and quantitative assessment of the status of bone tissue in vivo for one or more of the quantities:
- bone-mineral density, strength, and fracture risk, comprising the steps of;
(a) acoustically coupling a pair of transducers to nearby skin on opposite sides of said bone tissue; (b) generating an ultrasound excitation signal and directing same from one transducer to another transducer of said pair of transducers through said bone tissue, thereby producing a bone-oriented electrical output signal of the form of zs (t)=ps (t)+ns (t), where ps (t) is said bone-oriented output signal per se and ns (t) is an additive, uncorrelated Gaussian measurement noise associated with said boneoriented signal, said excitation signal being a finite-duration signal repeated substantially in a range from 1 to 1000 Hz and consisting of plural frequencies spaced in an ultrasonic spectral region up to about 2 MHz; (c) independently directing said excitation signal from said one transducer to said another transducer through a medium with known acoustic properties and path length and free of said bone tissue, thereby producing a reference electrical output signal of the form of zr (t)=pr (t)+nr (t), where pr (t) is said reference output signal per se and nr (t) is an additive, uncorrelated Gaussian measurement noise associated with said reference signal; (d) parametric modeling said bone-oriented signal and said reference signal, with obtaining two parametric models thereof, ps (t) and pr (t), respectively, to thereby establish a set Θ
s of bone-oriented parameters and a set Θ
r of reference parameters correspondingly associated with said models;(e) preprocessing said two sets of parameters of said models, an output of said preprocessing being a reduced set of parameters characterizing said models; and (f) subjecting said two sets of parameters to comparative analysis, whereby an estimate of said one or more quantities is obtained.
- bone-mineral density, strength, and fracture risk, comprising the steps of;
-
20. A method of non-invasive and quantitative assessment of the status of bone tissue in vivo for at least one of the quantities, bone-mineral density, bone strength, bone fracture risk, bone architecture and bone quality comprising the steps of:
-
(a) acoustically coupling a pair of transducers to nearby skin on opposite sides of said bone tissue; (b) generating an ultrasound signal and directing said ultrasound signal from one transducer to another transducer of said pair of transducers through said bone tissue, to produce a bone-oriented electrical output signal zs (t), said ultrasound signal being a finite-duration signal repeated substantially in a range of from about 1 to about 1000 Hz and having plural frequencies spaced in an ultrasonic spectral region up to about 2 MHz; (c) independently directing said ultrasound signal from said one transducer to said another transducer through a medium with known acoustic properties and path length and free of said bone tissue to produce a reference electrical output signal zr (t); (d) establishing a set Θ
s of bone-oriented parameters associated with said bone-oriented output signal zs (t) and a set Θ
r of reference parameters associated with said reference signal zr (t); and(e) subjecting said set Θ
s of bone-oriented parameters and said set Θ
r of reference parameters to comparative analysis, whereby an estimate of said at least one of the quantities, bone-mineral density, bone strength, bone fracture risk, bone architecture and bone quality is obtained. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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-
40. An apparatus for non-invasive and quantitative assessment of the status of bone tissue in vivo for at least one of the quantities, bone-mineral density, bone strength, bone fracture risk, bone architecture, and bone quality comprising
a pair of ultrasonic transducers; -
means for generating an ultrasound signal, said ultrasound signal being a finite-duration signal repeated substantially in a range of from about 1 to about 1000 Hz and having plural frequencies spaced in an ultrasonic spectral region up to about 2 MHz; means for directing said ultrasound signal from one transducer to another transducer of said pair of transducers through said bone tissue to produce a bone-oriented electrical output signal zs (t); means for independently directing said ultrasound signal from said one transducer to said another transducer of said pair of transducers through a medium of known acoustic properties and path length and free of said bone tissue to produce a reference electrical output signal zr (t); means for establishing a set Θ
s of bone-oriented parameters associated with said bone-oriented output signal zs (t) and a set Θ
r of reference parameters associated with said reference signal zr (t); andmeans for performing comparative analysis of said set of bone-oriented parameters Θ
s and said set of reference parameters Θ
r to thereby obtain an estimate of said at least one of the quantities, bone-mineral density, bone strength, bone fracture risk, bone architecture and bone quality. - View Dependent Claims (41, 42)
-
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43. A method of non-invasive and quantitative assessment of the status of bone tissue in vivo for at least one of the quantities, bone-mineral density, bone strength, bone fracture risk, bone architecture and bone quality comprising the steps of:
-
(a) acoustically coupling a pair of transducers to nearby skin on opposite sides of said bone tissue; (b) generating an ultrasound signal and directing said ultrasound signal from one transducer to another transducer of said pair of transducers through said bone tissue, to produce a bone-oriented electrical output signal, said ultrasound signal being a finite-duration signal having plural frequencies spaced in an ultrasonic spectral region up to about 2 MHz; (c) repeating step (b) a plurality of times to obtain a plurality of bone-oriented output signals; (d) averaging said plurality of bone-oriented output signals to obtain an averaged bone-oriented output signal; (e) independently directing said ultrasound signal from said one transducer to said another transducer through a medium with known acoustic properties and path length and free of said bone tissue to produce a reference electrical output signal; (f) repeating step (e) a plurality of times to obtain a plurality of reference signals; (g) averaging said plurality of reference signals to obtain an averaged reference signal; (h) establishing a set Θ
s of bone-oriented parameters associated with said averaged bone-oriented output signal and a set Θ
r of reference parameters associated with said averaged reference signal; and(i) subjecting said set Θ
s of bone-oriented parameters and said set Θ
r of reference parameters to comparative analysis whereby an estimate of said at least one of the quantities, bone-mineral density, bone strength, bone fracture risk, bone architecture and bone quality is obtained. - View Dependent Claims (44, 45, 46)
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Specification