The
The Ultrasound
Ultrasound Research
Research Interface:
Interface:
AA New
New Tool
Tool for
for Biomedical
Biomedical Investigations
Investigations
Shelby Brunke1, Laurent Pelissier2, Kris Dickie2,
Jim Zagzebski3, Tim Hall3, Thaddeus Wilson4
1Siemens
Medical Systems, Issaquah WA
Medical Corporation, Vancouver, BC
3Department of Med. Physics, University of Wisconsin
4Department of Radiology, University of Tennessee
2Ultrasonix
Introduction
Introduction
Digitally controlled ultrasound scanners offer
extensive levels of programmability, which
enable manufacturers to explore and to readily
incorporate alternative beam formation, signal
and image processing, networking, and
interfacing capabilities.
Recent efforts have led manufacturers to share
these tools for innovation with academic and
clinical researchers. This discussion will present
capabilities of two such machines and present
examples of research uses.
AAPM 2005
The
The Ultrasound
Ultrasound Research
Research Interface:
Interface:
A
A New
New Tool
Tool for
for Biomedical
Biomedical Investigations
Investigations
Examples
Examples of
of Use
Use
Jim Zagzebski, Tim Hall, Thaddeus Wilson*
Department of Med. Physics, University of Wisconsin
*Department of Radiology, University of Tennessee
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Parametric
Parametric Imaging
Imaging
• Except for Doppler, ultrasound imaging
is based entirely on echo amplitudes
• Parametric images
•Acoustic attenuation
•Scatterer size
•Speed of sound
•Elasticity (many forms)
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Ultrasound
Ultrasound Attenuation
Attenuation
Measuring
Measuring Attenuation
Attenuation
• Attenuation is used diagnostically in the
liver, breast, etc.
• However, only qualitative estimates are
made
• Record RF echo data from ROI
• Filter, measure reduction of rf signal
with depth
• In a clinical machine, signal amplitude
changes with depth are also affected
by:
– “mass exhibits shadowing”
– “mass exhibits good through transmission”
–
–
–
–
• Goals: incorporate methods for
determining attenuation locally, and in
the form of images.
log
S s (ω )
2
S r (ω )
2
Beam focusing, beam shapes
TGC settings set by operator
Internal TGC set by the manufacturer
Nonlinear processing in scanners
Depth
• Reference phantom techniques have
been developed that effectively
account for instrumentation effects.
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Human
Human liver
liver
Attenuation (dB/cm)
Attenuation in liver vs. frequency
4
3.5
3
2.5
2
1.5
1
0.5
0
Tu et al
• ROI outlined from B-mode
image (blue line)
• Areas of inhomogeneity
eliminated (red line)
• Algorithm retrieves RF echo
data from ROI, computes
attenuation
• Results in normal liver agree
with many previous reports
(0.5 dB/cm-MHz)
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Attenuation
Attenuation Imaging
Imaging
Siemens
Siemens SONOLINE
SONOLINE Antares
Antares
0.3 dB/cm/MHz contrast, 1 cm diameter
Lu et al
0
1
2
3
Frequency (MHz)
4
5
•Acquire RF data from multiple angles
•Compute α from ROI’s at each angle
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Spatial and Frequency
Compounding
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Attenuation
Attenuation Imaging
Imaging
Siemens
Siemens SONOLINE
SONOLINE Antares
Antares
““Scatterer
Scatterer Size”
Size
Size”” Imaging
Imaging
0.3 dB/cm/MHz contrast, 1 cm diameter
• RF data can be processed to yield the
“backscatter coefficient” at frequencies throughout
the signal bandwidth
• Values of backscatter vs. frequency reflect the size
of scatterers contributing to the signal.
• By applying scatterer size dependent correlation
models to the backscatter vs. data, possible to
estimate size.
•Acquire RF data from multiple angles
•Compute α from ROI’s at each angle
Spatial and Frequency
Compounding
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’Brien, IEEE
Mouse
OO’Brien,
Mouse tumor
tumor model
model (Oelze
(Oelzeand
andO’
IEEEUFFC,
UFFC,2004)
2004)
Use single element
transducer, 20 MHz
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Overlaid
-mode and
B
Overlaid BB-mode
and Scatterer
Scatterer size
size
•
•
Carcinoma
•
•
Fibroadenoma
Acquire RF echo data from
normal human thyroid
Siemens Antares, 6-13 MHz
Histology book: 100-200 µm
lobules
Scatterer size image data
appears to correlate with
anatomy.
Scatterer size
Reflects histological
structure
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Patient
Patient with
with thyroid
thyroid nodule
nodule (Wilson
(Wilson et
et al)
al)
Elasticity
Elasticity Imaging
Imaging
• Improve on manual palpation
• Use a clinical ultrasound imaging system as
a sensor of anatomic deformation
• Relative deformation quantifies the bulk
mechanical properties of tissue
• Provides new diagnostic information
Near real-time scatterer size imaging mode on Ultrasonix
RP500
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Estimation of Strain (Uses RF data frames)
Implementation
Implementation on
on Machine
Machine with
with URI
URI
Pre-compression RF line
Array Transducer
τ1
τ2
∆T
Post-compression RF line
Strain =
τ −τ 1
2
∆T
(Gradient of the axial
displacement)
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169
169 Breast
Breast Lesions;
Lesions; 11 Observer
Observer
Relative
Relative Size
Size of
of Lesions
Lesions
Invasive Ductal Carcinoma
Fibroadenoma
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Spatial Angular Compounded Elastograms
Spatial Angular Compounded Elastograms
(Ultrasonix 500 RP)
x 10
8
0
0º
-3
-3
x 10
8
0
0
x 10
8
5
7
10
6
5
7
5
7
15
5
10
6
10
6
20
4
15
5
15
5
25
3
20
10º
4
30
20
2
4
35
3
25
30
2
30
2
35
1
35
1
40
0
40
0
25
1
3
40
10
20
30
40
0
10
20
30
40
-3
12º
5
7
5
7
10
6
10
6
15
5
15
5
20
4
20
4
25
3
25
3
15º
30
2
30
2
35
1
35
1
0
40
40
0
10
20
30
40
0
10
20
(Ultrasonix, gel phantom, inclusion is 3x stiffer)
30
20
30
40
40
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0
-3
31
x 10
8
0
10
Elastogram Without Compounding
-3
x 10
8
0
0
30
SNRe (dB)
0
0
-3
29
28
o
0.5
o
1
o
2
o
3
27
26
25
0
5
10
15
o
Maximum Angle ( )
20
0
x 10
8
5
7
10
6
15
5
20
4
25
3
30
2
35
1
40
0
10
20
30
40
0
-15 º ~ 15 º
Compounded
Compounded Elastograms
Elastograms
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Speed
Speed of
of sound
sound
Speed
Speed of
of sound
sound
Hayashi et al, A new method
for measuring in vivo speed of
sound speed in the reflection
mode, J. Clin Ultrasound 16:
87-93, 1988.
Can you measure SOS in pulseecho mode?
• Beam former adds time delays to
echo data picked up from
elements in an array. Assumes
SOS = 1540 m/s.
• Some URI’s allow assumed speed
of sound to be programmed.
• Proper focusing is obtained only
when the assumed speed of
sound matches the speed of
sound in the subject. Affects
image intensity, for example.
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Speed
Speed of
of sound
sound
• Generate images of phantoms for different assumed
SOS in the beamformer
• Measure image brightness vs assumed SOS
• Peak occurs near SOS of phantom
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Conclusions
Conclusions
• Parametric imaging adds new information to
improve diagnostic accuracy
• The ‘research interface’ on high-end systems are
somewhat limiting in what the user can control
Extended control and system programming available
through close working relationship with manufacturer
RMI 403
C=1540 m/s
• The ‘research interface’ on lower-end systems
provide greater access to system resources and
system parameters
• These research interfaces provide an opportunity
to investigate imaging algorithms that were
impractical with laboratory data acquisition
systems
ATS 539
C=1460m/s
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