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Vital Signs for Vital Organs™ Non-Invasive Blood Flow Measurements Using Ultrasound Modulated...
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Transcript of Vital Signs for Vital Organs™ Non-Invasive Blood Flow Measurements Using Ultrasound Modulated...
Vital Signs for Vital Organs™
Non-Invasive Blood Flow Measurements Using
Ultrasound Modulated Diffused Light
N. Rachelia, A. Rona, Y. Metzgera, I. Breskina, G. Endenb, M. Balberga, R. Shechtera
a Ornim Medical Ltd, Israelb Biomedical Engineering Department, Ben- Gurion University, Israel
Outline
• Background• Phantom Setup• Data analysis and Results• In vivo evaluation • Conclusions• Future work
Ornim’s Regional Oximeter and Flowmeter
Monitor
Two Probes(multi-use)
Single use adhesive pad
Bed Side Monitor
• Cerebral & Tissue Oximeter – measures brain and muscle underneath the sensor
• Flow and oxygen saturation monitoring- simultaneously• Two probes – independent readings• Single use adhesive
Background
• Ornim’s patented technology utilizes principles of the acousto-optic effect
• The medium is irradiated with NIR coherent light
• Light is modulated in the tissue by a coded ultrasound series with a
narrow autocorrelation:
ftietGtg 2)()(
G(t): a series comprising of “1” and ” -1” bits, bit length = 4μsec. f = 1MHz.
Background
• The detected light I(t) is correlated with the ultrasound
series g(t):
2
)()(
tgtIUTL
0 5 10 15 20 25 300
2
4
6
8
10
12x 10
4
depth [mm]
UT
L cu
rve
ampl
itude
[A.U
]
Background
• The detected light I(t) is correlated with the ultrasound
series g(t):
2
)()(
tgtIUTL
0 5 10 15 20 25 300
2
4
6
8
10
12x 10
4
depth [mm]
UT
L cu
rve
ampl
itude
[A.U
]
Background
• The amplitude of the UTL curve is proportional to:
• Photons’ density
• Ultrasound field
• Decorrelation time
• Movement of scatterers affects the amplitude of the cross correlation
2
)()(
tgtIUTL
ftietGtg 2)()(
012345Flow Values [A.U]
Experimental setup
Phantom1
Syringe pump2
Reservoir
Tissue mimicking phantom with micro channels simulates small blood vessels
1
Generate flow at the range of 0 to 2.5 mm/sec
2Deliver coherent light and Ultrasound into the phantomRecord and analyze the light signal
3
Laser diode
3
Ultrasound generator
Photodetector
Fluid: 70% purified H2O;
10% Glycerol; 20% SpherotechInc Polystyrene spheres, 0.4-0.9µm )5% W/V(
Data Analysis and Results
• Extracting the Flow Index )CFI( from the UTL curve
1
)()(1
)(
Nk
kii tUTL
NtItCFI
0 5 10 15 20 25 300
2
4
6
8
10
12x 10
4
depth [mm]
UT
L c
urv
e a
mp
litu
de
[A.U
]
N
K
Data Analysis and Results
• The amplitude of the UTL curve decreases as flow through
the channels increases
• CFI is linear as a function of the flow velocity
• Sensitivity to flow in deep channels is lower but measurable
0 5 10 15 20 25 30-2
0
2
4
6
8
10
12x 10
4
depth [mm]
UT
L cu
rve
ampl
itude
[A.U
]
0 l/min 750 l/min1750 l/min
0 0.5 1 1.5 2 2.50.5
1
1.5
2
2.5
3
3.5
4
velocity [mm/sec]
CF
I [A
.U]
All rowsRow cRow a
R2=0.97
R2=0.99
R2=0.90
Data Analysis and Results
• The effect of scatterers concentration was tested
• Diluted the original liquid from 1% to 0.66% of Polystyrene spheres )W/V(
• The CFI is linear as a function of the normalized velocity values
0 0.005 0.01 0.015 0.02 0.0250
0.5
1
1.5
2
2.5
3
3.5
4
velocity * concentration [mm/sec*g/ml]
CF
I [A
.U]
High concentrationLow concentration
R2=0.87
In vivo Evaluation
• Preclinical model – piglets
• Comparison to a commercial, invasive, Laser Doppler )LD( Moor Instrument DRT4, with DP3b probe
• Manipulations
• Flow increase - Epinephrine
• Flow decrease -Nitropruside/hyperventilation/occlusion
In vivo Evaluation
CFILaser
DopplerEpinephrine 0.824 0.776
Nitropruside 0.914 0.919
Hyperventilation 1 1Epinephrine Injection
Nitropruside Injection
ROC analysis - AUC
Hyperventilation
Cerox 3210F- Oxygen saturation and blood flow
• Combined display of saturation and flow per channel
Saturation
Flow
Blood occlusion Exercise
Saturation
Conclusions
• A novel method for continuously and non invasively measuring flow in deep tissue based on ultrasound modulated diffused light was presented
• Data demonstrates a linear correlation of CFI to flow in channels deeper than 1cm in a synthetic phantom
• A very good in vivo correlation to Laser Doppler readings was demonstrated
Future Work
• Clinical studies – cerebral flow monitoring during surgeries
• Calibrate CFI
• Numerical model
Vital Signs for Vital Organs™
THANK YOU
http://www.ornim.com
Vital Signs for Vital Organs™