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

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Vital Signs for Vital Organs™