quantitative assessment of human bone tissue by novel ultrasound techniques presenter : pei - jarn...
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Quantitative Assessment of Quantitative Assessment of Human Bone Tissue by Novel Human Bone Tissue by Novel
Ultrasound TechniquesUltrasound Techniques
Presenter : Pei - Jarn ChenPresenter : Pei - Jarn Chen
NCKU BME Ultrasound Lab.
OutlineOutline1. Introduction1. Introduction ---- Osteoporosis---- Osteoporosis ---- Quantitative Ultrasound (QUS)---- Quantitative Ultrasound (QUS)2. Motivations2. Motivations3. Material and Methods3. Material and Methods (a) Quantitative assessment of osteoporosis from (a) Quantitative assessment of osteoporosis from
the tibia shaft by the tibia shaft by dual-transducers techniquedual-transducers technique (b) Measurements of ultrasonic parameters on (b) Measurements of ultrasonic parameters on
calcaneus by calcaneus by two-sided interrogation two-sided interrogation techniquestechniques
(c) Measurements of acoustic velocity dispersion (c) Measurements of acoustic velocity dispersion on calcaneus using on calcaneus using time-domain split spectrum time-domain split spectrum processing (SSP) techniquesprocessing (SSP) techniques
4. Results4. Results5. Conclusion and Discussion5. Conclusion and Discussion6. Future developments6. Future developments
IntroductionIntroduction1. Osteoporosis1. Osteoporosis
http://www.mayohealth.com http://www.nof.org
WHO : (1994)Osteoporosis is defined as a disease characterized by both a loss of bone mass and microarchitecture alteration, leading to hyperfragility, and to an uncommonly high risk of fracture.
cortical
cancellous (trabecular)
Type I : -- induced by estrogen
deficiency -- women after menopause
Type II : -- Senile osteoporosis-- affects both sexes after age
70 and results in a reduced bone density of both the cortical and trabecular bone
2. 2. Bone Density Assessment System Bone Density Assessment System in Clinicin Clinic
(a) Non-ultrasound techniques SPA (Single Gamma Photon
Absorptiometry) DPA (Dual Gamma Photon
Absorptiometry) DEXA (Dual-Energy X-ray
Absorptiometry) QCT (X-ray Computed Tomography)
----- BMD (Bone Mineral Density, g/cm2, g/cm3)
Disadvantages : (1) radiation (2) high cost (3) mechanical properties ?
(b) Ultrasound techniques ---- QUS (quantitative ultrasound) Advantages: (1) moveable (2) radiation free (3)
low cost
DEXA----- Lunar DPX
RegionRegion AreaArea BMC(g)BMC(g) BMD(g/cmBMD(g/cm22)) T-scoreT-score Z-scoreZ-score
NeckNeck 4.704.70 3.983.98 0.8470.847 -0.0-0.0 0.30.3
TrochTroch 8.288.28 6.956.95 0.8390.839 1.31.3 1.51.5
InterInter 15.7615.76 19.1319.13 1.2141.214 0.70.7 0.80.8
TotalTotal 28.7428.74 1.051.05 0.8090.809 0.60.6 1.31.3
Normal T-score > -1Low bone mass -2.5 < T-score < -1Osteoporosis T< -2.5Severe osteoporosis (1) T < -2.5 (2) fracture* Unit : SD (standard deviation)
WHO criteria
• T- score: the difference in SD between the individual’s BMD and the mean BMD of health young (24-40).• Z - score: bone density compared with that of an average of people in same age group and gender
Broadband Ultrasound Attenuation ( BUA )
Speed of Sound ( SOS ) E: Young’s Modulus : density
Acoustic impedance Backscattering coefficient
(AIB, apparent integrated backscattering) Velocity dispersion
E
v
xfeII )(0
cz
3. Quantitative Ultrasound (QUS)3. Quantitative Ultrasound (QUS)
water
bone
BUA BUA (dB / MHz)(dB / MHz) Measurement Measurement
Signal Frequency domain
fyxBUA
fyxA
fyxAfyx
MHzslope
r
,,
,,
,,*20,,
]6.02.0[
log
BUABUA
f
dB
FFT
)(
)(
21
21
ttt
ssx
t
xvelocityBone
xb
b
xtx
velocityLimb
SOS measurements
(1) Time domain (signal velocity, group velocity)
* TOF : time of flight
Time of Flight ( TOF)
1. First Arrival2. Threshold3. Zero Crossing4. Envelope Peak
T
1234
P. H. F. Nicholson, G. Lowet, C. M. Langton, J. Dequeker and G. Van der Perre, “ A comparison of time-domain and frequency-domain approaches to ultrasonic velocity measurement in trabecular bone”, Phys. Med.Biol., 41, pp. 2421-2435, 1996.
water
bone
Signal Frequency domain (2π unwrapped )
MHzf
r
r
fvSOS
dff
v
fv
fAfAf
5.0
*21
1
(2) Frequency domain ( phase velocity)
* unwrapped technique
f
SOS
FFT
◆ ◆ based on : attenuated with power lawbased on : attenuated with power law
dss
s
VV PP
0
20
)(2
)(
1
)(
1
Velocity Dispersion
yii 0
※ Kramers – Kronig Relationship ( O’Donnell , 1981)( O’Donnell , 1981)
※ Conventional approaches (a) time domain (b) frequency domain
VDM may convey important structural information not already contained in BMD, SOS, or BUA . ( Droin, 1998)
* * Velocity dispersion Velocity dispersion magnitudemagnitude ( m s( m s-1-1 MHz MHz-1-1)) VDM = ∆V = V( fmax ) - VDM = ∆V = V( fmax ) - V( fmin )V( fmin )
Conventional velocity dispersion measurements
frequency domain
fdfC
CfV
w
wp )(
1)(
Vp(f) : phase velocity
Cw : acoustic speed in water
d : thickness of phantom
f : frequency
(f) : phase difference
between water and medium
time domain
f1f2
fn
f1
f2
fn
Vp(f1)me
diu
m
Vp(f2)
Vp(fn)
1. discontinuity
2. absolute phase
* substitution method
Recent VDM researches on Recent VDM researches on Calcaneus Calcaneus in vitroin vitro measurements measurements
Authors n Frequency range Dispersion (mean ± standard (kHz) deviation) (m s-1 MHz-1)
Wear (2000)
Nicholson et al (1996)
Strelitizki and Evans (1996)
Dorin et al (1998)
24 200-600 -18 ± 15
70 200-800 -40
10 600-800 -32 ± 27
15 200-600 -15 ± 13
Negative (63/70)
Positive (7/70)
P. H. F. Nicholson, G. Lowet, C. M. Langton, J. Dequeker and G. Van der Perre, “ A comparison of time-domain and frequency-domain approaches to ultrasonic velocity measurement in trabecular bone”, Phys. Med. Biol., 41, pp. 2421-2435, 1996.
Motivations Motivations 1.Bone thickness is always not available in 1.Bone thickness is always not available in in in
vivovivo measurements . measurements . → → one equation with one equation with two unknown parameterstwo unknown parameters → How to reduce → How to reduce the errorsthe errors ??
2. VDM2. VDM ※ ※ frequency frequency domaindomain (1) resolution, window gate selection(1) resolution, window gate selection (2) change rapidly in low SNR range(2) change rapidly in low SNR range (3) Calcaneus VDM positive? negative?(3) Calcaneus VDM positive? negative? ※ ※ time domaintime domain→ multiple transducers→ multiple transducers→ → CouldCould VDM be acquired in time-domain VDM be acquired in time-domain
with one transducer based on one shot with one transducer based on one shot broadband pulse ?broadband pulse ?
wbone
bonew
Vd
dVV
w
p
bone
p
p
V
dd
d
V
VV
1
1
15 20 25 30 35 40 45 50-40
-30
-20
-10
0
10
20
30
40
true calcaneus width (mm)
err
or
(%)
SOS: 1600 m/sSOS: 2000 m/sSOS: 3000 m/s
The SOS estimation errors vs. true bone tissue thickness for different bone velocities assuming a preset bone thickness of 40 mm. ( + : 1600 m/s, * : 2000 m/s, : 3000 m/s).◇
1. For a dry system, a 6 mm decrease in heel thickness caused an increase of 24 m/s in SOS as reported by Johansen
2. For a dry system, such as CUBA system, presses transducers against the skin to obtain the calcaneus width and the mean speed of sound (SOS) measured by contact type (soft tissue intact) is lower 89 m/s than the mean bone SOS (no soft tissue) in in vitro measurements .
1. A. Johansen, and M. D. Stone, “ The effect of angle edema on bone ultrasound assessment of the heel,” Osteoporos Int., vol. 7, pp. 44-47, 1997.
2. K. D. Häulser, etc. “ Water bath and contact methods in ultrasonic evaluation of bone,” Calcif Tissue Int., vol. 61, pp. 26-29, 1997.
Material and Methods
1.1. Quantitative assessment of osteoporosisQuantitative assessment of osteoporosis from the tibia shaft by from the tibia shaft by dual-ultrasound dual-ultrasound
techniquetechnique
3. Measurements of acoustic velocity 3. Measurements of acoustic velocity dispersion on calcaneus using dispersion on calcaneus using time-time-domain split spectrum processing (SSP) domain split spectrum processing (SSP) techniquetechnique
2.2. Measurements of ultrasonic parameters onMeasurements of ultrasonic parameters on calcaneus by calcaneus by two-sided interrogation two-sided interrogation
techniquetechnique
1
2
xCw
1
2 2xC
zCw b
2 x
CBECw w
2
xC
zC
CDC
DECw b b w
A--B--A
A--B--C--B--A
A--B--E
A--B--C--D--E
--------------(1)
---------------(2)
---------------------------(3)
---------(4)
#1
#2 x z
A B
D
CTransducer
Transducer
y
E
Coupling medium Tibia shaft
Dual-ultrasound Dual-ultrasound techniquetechnique
b
w
C
Czz : Effective distance
z
(transmitter & receiver)
( receiver)
,1 1
,2 2
Cb
Cy
K Kb
( )
[( ) ] ( )
1
1 2 1 2
111 2 2 2
K
1
212
2 2 1
12 2
1
4 2( )
( )and
: the TOFs from the trigger of the transmitting pulse to the front and the rear echoes of bone tissue received by transducer #1
: the TOFs on transducer #2
: sound speed in bone tissue (tibia)
y : the separation distance of two transducers
then
where
Pulser/Receiver
PANAMETRICS
5058PR
PANAMETRICS
5052PR
High sampling rateA/D card (100Mhz)
Channel A Channel B
T/R RCVR
Pulse/FunctionGenerator
Pulser / receiver
Ext.Tri.
Ext.Tri.Syn.
oscilloscope
HP 8111A
Jelly
sampleJelly
System Setup
Theoretical DerivationTheoretical Derivation
w
ww V
dt
dw
ffmw
bf
ff tV
dddd
V
d
V
ddm
)( 2121
)(f
fwdwfm
mwb
V
dttVdd
dVV
Vf = 1540 m/s
Vw= 1487 m/s at 22 oC
Two-sided interrogation Two-sided interrogation techniques (1)techniques (1)
* df = df1= df2
2121 tt
V
d
f
f
2342 tt
V
d
f
f
dw
ffmw
bf
ff tV
dddd
V
d
V
ddm
)( 2121
)22
()22
( 341231 ttttV
ttVdd fwwm
)2
()(2
34123412
ttttttVtttt
Vd
dVV
wdwf
m
mwb
Two-sided interrogation Two-sided interrogation techniques (2)techniques (2)
TransducerTransducerTransducer: Part number : Panametrics V391Frequency : 0.5 MHzType : Immersion transducerElement size : 29 mm (1.125")Focusing configurations :1.5", PTF (Point Target Focus) Spherical focus
1. Good axial resolution
2. Improved signal-to-noise (SNR) in attenuated or scattering materials
x1
x2
xn
x1’
x2’
xn’
med
ium
Velocity dispersion ?
f ( Hz )
V (m/s)
A0(t) A(t)
decompose decompose
VDM ----- Theory development
※ ※ SSP - SSP - Bilgutay, 1981 Bilgutay, 1981
BPF : bandpass filter
Split Spectrum Processing (SSP)
Y(t)
BPF f1(t)
BPF f2(t)
BPF fn(t)
X’1(t)
X’2(t)
X’n(t)
Y’(t)
expansion reconstruction
filter bank
x’n(t)
N
i
N
iii tythty
1 1
)()()(
)()()( fYfHfY
n
ii fHfH
1
)()(
)2sin()(2
2
2 tfAeth i
t
it
if H(f) =1
Bandpass filter bank design
5
2000 5 10
0 2000 4000 6000 0 5 10 15
x 105
each gaussion filter in t domain FFT of each Gaussion filter
Hz
x
fB ci
2
Total filter numbers
N = BT + 1B: total bandpass filter width ( fmax- fmin )
T : total signal time
fc: central frequency
: predetermined threshold
: attenuation coefficient
X: thickness
Each filter bandwidth
Bi = 50 kHz
( Ping He, 1998 )
( Karpur, 1987 )
0 2 4 6 8 10 12
x 105
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Hz
Summed bandpass filter
Individual Gaussian filter
fmin fmax
B
1,....,0minmaxmin
Nnn
N
ffffi
t f
1 2 3 4 5 6 7 8 9 10
x 104
10-7
10-6
10-5
10-4
10-3
The ROC curve of gauss filter width with RMS error
RM
S e
rror m
agni
tude
gaussion band width (Hz)
-150 m/s-40m/s 0 m/s 40 m/s 150 m/s
1 2 3 4 5 6 7 8 9 10
x 104
-2000
-1500
-1000
-500
0
500
1000 The ROC curve of gaussion filter width with velocity error
gaussion band width (Hz)
velo
city e
rror
(m/s
)
-150 m/s-40 m/s 0 m/s40 m/s 150 m/s
Gaussian Filter Design
NiyixEN
irms /)()(
2
1
* optimal bandwidth
→ 50 KHz
Reconstruction error Error between preset velocity and SOS evaluated
0 1000 2000 3000 4000 5000 6000-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
b--- input signal with SSPk--- simulated input signal
Velocity dispersion and BUA estimation
0 2000 4000 6000 0 2000 4000 6000
BUAi
incident transmission
)(
)(log20
tA
tABUA
ri
ii
d : medium thickness
ti : time of difference
Cw : acoustic speed in water
phase velocity
d
tCC
fViw
wip
1)(
Ai(t) : narrow band incident signal in time domain
Ari(t) : narrow band reference signal through water
Δti
ResultsResults
1.1. Quantitative assessment of osteoporosisQuantitative assessment of osteoporosis from the tibia shaft by from the tibia shaft by dual-ultrasound dual-ultrasound
techniquetechnique
3. Measurements of acoustic velocity 3. Measurements of acoustic velocity dispersion on calcaneus using dispersion on calcaneus using time-time-domain split spectrum processing (SSP) domain split spectrum processing (SSP) techniquetechnique
2.2. Measurements of ultrasonic parameters onMeasurements of ultrasonic parameters on calcaneus by calcaneus by two-sided interrogation techniquetwo-sided interrogation technique
thi cknes
s
(mm)
1
(sec)
1
(sec)
2
(sec)
2
(sec)
sos
(m/ sec)
y
(mm)
8.96 62.80 69.32 63.28 70.84 2748.5 8.5720
Thickness= 8.96 mm, SOS= 2748.5 m s-1 Plexiglas
System performance test (1)
τ1τ1
τ2 τ2’
τ1’
0 20 40 60 80 100 120-1.5
-1
-0.5
0
0.5
1
0 20 40 60 80 100 120-1
-0.5
0
0.5
1
Dual-ultrasound techniquesDual-ultrasound techniques
0 20 40 60 80 100 120-1.5
-1
-0.5
0
0.5
1
0 20 40 60 80 100 120-1
-0.5
0
0.5
1
thi ckness
(mm)
y
(mm)
1
(sec)
1
(sec)
2
(sec)
2
(sec)
SOS*2
(m/ sec)
* 8.5720 65.64 70.16 65.74 71.02 2731.3
unknown thickness Plexiglas
System performance test (2)
Accuracy = 99.3%
CV%= 3.53 % for 10 measurementsat different sites
In-vivo measurements
0 20 40 60 80 100 120 140 160 180-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 50 100 150 200 250 300-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0 20 40 60 80 100 120-4
-2
0
2
4
0 20 40 60 80 100 120-2
-1
0
1
2
0 20 40 60 80 100 120-1
-0.5
0
0.5
1
1.5
0 20 40 60 80 100 120-1.5
-1
-0.5
0
0.5
1
normal subject
osteoporosis
0 .90 1 .00 1 .10 1 .20 1 .30
B M D (g/ cm ^2)
2500 .00
3000 .00
3500 .00
4000 .00
4500 .00
SO
S (m
/s)
Subjects: --- 18 outpatients recruited from NCKU Hospital--- suffering from low back pain, radiological evidence of
osteoporosis and/or compression fracture of the vertebral body -- post-menopausal or senile osteoporosis: 5 males, 4 females
( mean age 65 years, 56 ~ 73 )-- nine patients had been immobilized for more than 3 months
after various orthopedic surgeries ( mean age 52 years, 21 ~ 72)
R= 0.93
BMD- measured by DEXA (Lunar DPX, radiology of NCKU Hospital)
Two-sided interrogation techniquesTwo-sided interrogation techniques
In vitro measurements
model 2583model 2572
2583: normal bone SOS = 1576 m s-1 BUA= 69 dB/MHz 2572: osteoporosis SOS = 1501 m s-1 BUA= 48 dB/MHz
porcine skin (7.3 mm)
In vivoIn vivo measurements measurements
Subjects : 6 males 8 females Measurement site : left calcaneus
Time-domain split spectrum processing Time-domain split spectrum processing (SSP) techniques(SSP) techniques
※ Model-based ultrasound signals with velocity dispersion
FN(fN)
RN(t)
R(t)
Y(t)
R2(t)
R1(t)
f1 f2 fN
f1 f2 fN
f1 f2 fN
F1(f1)
F2(f2)
attenuation & dispersion
Fig. Schematic representation of model-based ultrasound signal
0022 22/)( ifit eeAetY t Σ
Ri(t) Time delay tgi Zi(t)dfie
)( 0ffbC
dt
issogi
)()( tZtZ i
2600 2800 3000 3200 3400 3600 3800
-0.1
-0.05
0
0.05
0.1
-150 m/s MHz-80 m/s MHz -40 m/s MHz 0 m/s MHz
2600 2800 3000 3200 3400 3600 3800
-0.1
-0.05
0
0.05
0.1
0 m/s MHz 40 m/s MHz 80 m/s MHz 150 m/s MHz
0 1000 2000 3000 4000 5000 6000-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1k- simulated input signalr-- simulated output signal
bs= - 80 m/s MHzcalcaneus: 2 cmattenuation : 20 dB1550 m/s at 0.5 MHz
bs : velocity dispersion parameters (m/s MHz)Cso : group velocityf0 : central frequency
The simulation results of an ultrasound pulse transmits the calcaneus with velocity dispersion ( -80 m s-1 MHz-1)
negative dispersion
positive dispersion
※ Comparison with K. Wear’s numerical simulation
Simulation parameters: medium : calcaneus
f0= 500 kHz, f=1/(2t) = 100 kHz, = 2.3 cm-1MHz-1,
d = 2 cm, Cs=1550 m s-1 at 500 kHz, 0=0, Cw=1480 m s-1
2600 2800 3000 3200 3400 3600 3800
-0.1
-0.05
0
0.05
0.1
-150 m/s MHz-80 m/s MHz -40 m/s MHz 0 m/s MHz
Velocity dispersion = - 150 ms-1 MHz-1
( K. A. Wear , 2000)
Time (10^-8 sec)
2 3 4 5 6 7 8 9
x 105
1450
1500
1550
1600
1650
Hz
SOS
(m/s
)
bs = -150 m/sMHz
bs = 150 m/sMHz
Fig. The analysis of phase velocity by SSP technique with various velocity dispersion. ( -150 m s-1 MHz-1 ~ 150 m s-1 MHz-1) - : preset value + : SOS predicted by SSP technique
SSP results with model-based ultrasound signals
Preset VDM (m/s Preset VDM (m/s MHz)MHz)
Predicted VDM by Predicted VDM by SSPSSP
Error Error (%)(%)
150150 126.52126.52 15.6615.66
8080 72.6272.62 9.229.22
4040 36.6536.65 8.378.37
00 0.00.0 0.00.0
-40-40 -36.68-36.68 8.308.30
-80-80 -72.59-72.59 9.269.26
-150-150 -125.96-125.96 16.0216.02
※ The comparisons with conventional The comparisons with conventional techniques in frequency-domaintechniques in frequency-domain
Conventional techniqueConventional technique ( Nicholson, 1996)( Nicholson, 1996)
2π unwrapped
Circular- rotating Circular- rotating technique (Ping He, technique (Ping He, 2001)2001)
2 3 4 5 6 7 8 9 10 11 12
x 105
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
Hz
SO
S (
m/s
)
VDM by SSPPreset VDMVDM by f-domainVDM by Ping He
Bs= -40 m/s
2 3 4 5 6 7 8 9 10 11 12
x 105
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
Hz
SOS (
m/s)
VDM by SSPPreset VDMVDM by f-domainVDM by Ping He
Bs= 0 m/s MHz
2 3 4 5 6 7 8 9 10 11 12
x 105
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
Hz
SO
S (
m/s
)
VDM by SSPPreset VDMVDM by f-domainVDM by Ping He
Bs= 40 m/s
Bs= - 40 m/s MHz
Bs= 40 m/s MHz
Bs= 0 m/s MHz
mimic calcaneus phantoms mimic calcaneus phantoms a. a. normal bonenormal bone (model 2583, CIRS Inc., Norfolk, VA. )(model 2583, CIRS Inc., Norfolk, VA. ) manufacturer’s specifications manufacturer’s specifications ::
thickness 3.63 cm, SOS = 1576 m sthickness 3.63 cm, SOS = 1576 m s -1-1, ,
BUA= 69 dB MHzBUA= 69 dB MHz-1-1 ( 0.2 ~ 0.55 MHz ) ( 0.2 ~ 0.55 MHz )
b. b. osteoporosis boneosteoporosis bone
(model 2572, CIRS Inc., Norfolk, VA. )(model 2572, CIRS Inc., Norfolk, VA. ) manufacturer’s specifications : manufacturer’s specifications :
thickness 3.64cm, SOS = 1510 m sthickness 3.64cm, SOS = 1510 m s -1-1, ,
BUA= 48 dB MHzBUA= 48 dB MHz-1-1 ( 0.2 ~ 0.55 MHz) ( 0.2 ~ 0.55 MHz)
Phantoms measurements
model 2583 model 2572* SOS: speed of sound
0.5 MHz unfocused0.5 MHz unfocused
2 * Transducer 2 * Transducer
T/R : 5058 PR, Panametrics Inc., Waltham, MA.
oscilloscope: TDS 520D, ( Tektronix Inc., Beaverton, OR.)
Measurement system
0 .00 200000 .00 400000 .00 600000 .00 800000 .00 1000000 .00
1450 .00
1500 .00
1550 .00
1600 .00
1650 .00
1700 .00
SO S (m / s)
H z
Phantom VDM by SSP(mean ± SD)(m / s MHz)
Signal velocity
(manufacturer’s specifications )(m / s)
Signal velocity by SSP(μ ± σ m/s)(m / s)
normal 1 85.41 ± 9.63 1576 1559.72 ± 7.51
osteoporosis 2 34.08 ± 4.15 1510 1499.98 ± 2.37
Fig. The comparisons of signal velocity(: 0.25, 0.5, 0.75 MHz) and phase velocity analyzed by SSP technique [ osteoporotic bone phantom ( * ), normal bone phantom ()].
1. normal bone: CIRS ( model: 2583)2. osteoporotic bone: CIRS ( model : 2572)
0 1 2 3 4 5 6 7 8 9 10
x 105
1200
1300
1400
1500
1600
1700
1800
Hz
phas
e ve
locity
(m/s
)
group velocityphase velocity by SSPphase velocity (unwrap)phase velocity (cir. rot.)
0 1 2 3 4 5 6 7 8 9 10
x 105
1200
1300
1400
1500
1600
1700
1800
Hz
phas
e ve
locity
(m/s
)
group velocityphase velocity by SSPphase velocity (unwrap)phase velocity (cir. rot.)
The comparisons between time-domain The comparisons between time-domain SSP and conventional techniques in SSP and conventional techniques in frequency-domainfrequency-domain
Normal bone phantom (Model 2583) ※ different window gate selection
0 1 2 3 4 5 6 7 8 9 10
x 105
1200
1300
1400
1500
1600
1700
1800
Hz
phas
e ve
loci
ty (m
/s)
group velocityphase velocity by SSPphase velocity (unwrap)phase velocity (cir. rot.)
0 1 2 3 4 5 6 7 8 9 10
x 105
1200
1300
1400
1500
1600
1700
1800
Hz
phas
e ve
locity
(m/s
)
group velocityphase velocity by SSPphase velocity (unwrap)phase velocity (cir. rot.)
The comparisons between time-domain The comparisons between time-domain SSP and conventional techniques in SSP and conventional techniques in frequency-domainfrequency-domain
Osteoporosis phantom (Model 2572) ※ different window gate selection
VP : group velocity by envelop peak Vc : group velocity at 0. 8 MHz by SSP techniqueVDM : velocity dispersion magnitude between 0.4 ~ 1.2 MHz
SOSUBIS: SOS by UBIS 5000BUAUBIS: BUA by UBIS 5000
The results of in vivo measurements on calcaneus
Discussion (1)Discussion (1)(a) Quantitative assessment of osteoporosis from the (a) Quantitative assessment of osteoporosis from the
tibia shaft by tibia shaft by dual-ultrasound techniquedual-ultrasound technique
1. Without knowing he thickness of tibia, the proposed 1. Without knowing he thickness of tibia, the proposed techniques can estimate the SOS with tibia, only from techniques can estimate the SOS with tibia, only from the different TOFs acquired from two transducers.the different TOFs acquired from two transducers.
2. High accuracy ( 99 %) and low CV (3.53 %) reveal in 2. High accuracy ( 99 %) and low CV (3.53 %) reveal in Plexiglas phantom measurements with developed Plexiglas phantom measurements with developed system.system.
3. High correlation coefficient (R = 0.93) exists between 3. High correlation coefficient (R = 0.93) exists between BMD (DEXA) and SOS BMD (DEXA) and SOS in vivoin vivo measurements. measurements.
Discussion (2-1)Discussion (2-1)(b) Measurements of ultrasonic parameters on(b) Measurements of ultrasonic parameters on
calcaneus by calcaneus by two-sided interrogation techniquetwo-sided interrogation technique1. The proposed two-sided interrogation technique can 1. The proposed two-sided interrogation technique can
directly measure the bone thickness and estimates the directly measure the bone thickness and estimates the SOS on calcaneus, neglecting the soft tissue effect.SOS on calcaneus, neglecting the soft tissue effect.
2. Based on the test of bone phantom attached with 2. Based on the test of bone phantom attached with porcine skin , the accuracy with SOS estimation is high porcine skin , the accuracy with SOS estimation is high up 99 % and 96 % using proposed techniquesup 99 % and 96 % using proposed techniques..
3.3. Based on 14 normal subjects Based on 14 normal subjects in vivo in vivo measurements, measurements, the thickness of calcaneus ranged between the thickness of calcaneus ranged between 3.3 ~ 4.7 3.3 ~ 4.7 cmcm and the SOS of calcaneus ranged from and the SOS of calcaneus ranged from 1473 m s1473 m s-1-1 to to 15371537 m sm s-1-1. Those agree with literatures’ reports. . Those agree with literatures’ reports. (1. (1. Glüer, 1995; 29.0 ± 2.9 mm from radiographics, 30.0 ± 2.8 Glüer, 1995; 29.0 ± 2.9 mm from radiographics, 30.0 ± 2.8 mm from CT. 2. Laugier, 1997; 1485 ~ 1550 m smm from CT. 2. Laugier, 1997; 1485 ~ 1550 m s-1-1, 5.8 ~ 18.2 , 5.8 ~ 18.2 dB cmdB cm-1-1 MHz MHz-1-1))
Discussion (2-2)Discussion (2-2)
4. The SOS on calcaneus measured with 4. The SOS on calcaneus measured with proposed technique were lower than the proposed technique were lower than the results with constant accumulated thickness results with constant accumulated thickness (bone + soft tissue) assumption and those (bone + soft tissue) assumption and those from UBIS 5000 measurements.from UBIS 5000 measurements.
Discussion (3-1)Discussion (3-1)(c) Measurements of acoustic velocity (c) Measurements of acoustic velocity
dispersion on calcaneus using dispersion on calcaneus using time-domain time-domain split spectrum processing (SSP) techniquesplit spectrum processing (SSP) technique
1.The SSP technique decomposes a 1.The SSP technique decomposes a
broadband pulse into serial signals having broadband pulse into serial signals having
different frequency using an optimal different frequency using an optimal
bandpass filter bank combined by many bandpass filter bank combined by many
narrow bandpass filter with constant narrow bandpass filter with constant
bandwidth .bandwidth .
2. 2. The VDM can be obtained only from one The VDM can be obtained only from one
shot broadband ultrasound pulse with a shot broadband ultrasound pulse with a
single interrogation.single interrogation.
3. The VDM evaluated by SSP technique are 3. The VDM evaluated by SSP technique are consistent with the simulation on model-consistent with the simulation on model-based signals, especial for the low based signals, especial for the low velocity dispersion ( < 80 m svelocity dispersion ( < 80 m s-1-1 MHz MHz-1-1).).
4. 4. The VDM measurements of two The VDM measurements of two commercial bone phantoms are agreeable commercial bone phantoms are agreeable to the results measured by three to the results measured by three transducers with different central transducers with different central frequencies.frequencies.
Discussion (3-2)Discussion (3-2)
ConclusionConclusion1. Three novel ultrasound techniques 1. Three novel ultrasound techniques
proposed in this thesis are fair simple, proposed in this thesis are fair simple, straightforward and easily performed in straightforward and easily performed in time-domain to estimate the SOS, VDM time-domain to estimate the SOS, VDM on bone tissue.on bone tissue.
2. 2. Based on the phantoms measurements, Based on the phantoms measurements, the simulation with model-based signals the simulation with model-based signals and the and the in vivo in vivo measurements, measurements, respectively; the results reveal that the respectively; the results reveal that the proposed three novel ultrasound proposed three novel ultrasound techniques may have the potential on techniques may have the potential on clinical applications for osteoporosis clinical applications for osteoporosis assessments.assessments.
Future DevelopmentsFuture Developments1. A QUS scan system developed on PC based 1. A QUS scan system developed on PC based
on two-sided interrogation technique has on two-sided interrogation technique has been developed and is in progress . been developed and is in progress .
2. The VDM image based on proposed SSP 2. The VDM image based on proposed SSP technique may be developed in above technique may be developed in above system.system.
3. The techniques proposed in this thesis 3. The techniques proposed in this thesis hope to be performed in an embedded hope to be performed in an embedded SOPC system (System on Programmable SOPC system (System on Programmable Chip) (i.e. FPGA-NIOS system).Chip) (i.e. FPGA-NIOS system).
4. The relations between VDM,4. The relations between VDM, BMD and BMD and bone microstructurebone microstructure are worth to further are worth to further studystudy..
Dual Energy X-ray Absorptiometry (DEXA)
SB70B38
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where:
I I exp[-( M M )]
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(
Reference CurveReference Curve
407 healthy Caucasian U.S. females,ranging in age from 20 to 79 years were used to establish the normality curve.