Daniele Tosi - OFSRC presentation at Jiliang University

Optical fiber sensors for medical applications Research activities at University of Limerick

[Jiliang University, 10 Dec 2013]

Daniele Tosi

[email protected]

www.ofsrc.ul.ie

http://www.ofsrc.ul.ie

http://www.ofsrc.ul.ie

Daniele Tosi - Optical fiber sensors for medical applications - Research activities at University of Limerick

AboutUniversity of LimerickOptical Fibre Sensors Research Centre[Marie Curie Fellow @ OFSRC]


Partnerships

UL, OFSRCPointec (licensing)Cleveland Clinic

EFPI cardiovascular/demo

Johns HopkinsRobotic surgery

Partners ItalyPolitecnico di Torino (FBG)Federico II Napoli (urodynamic)Universita’ di Pavia (RFA)Politecnico di Milano (RFA)LunaTEC

Cyprus IT (EFPI partner)

ShenzhenCustom catheters supplier

Harbin Inst. Technol.Staff exchange partnership


Outline➡ Optical fiber sensors: properties and technology‣EFPI - pressure, temperature, refractive index‣Fiber Bragg grating (FBG), DTG, LPG‣Sensor integration and interrogation‣Catheterization

➡ Emerging applications in medical/biomedical‣Cardiovascular, FFR, IABP‣Urodynamics‣Monitoring of radiofrequency thermal ablation‣Robotic surgery tools

➡ Conclusions


OFS properties

Top-notch Performance

Miniature size

Distribution and Integration

Immunity

➡ Excellent sensitivity to press., temp., strain➡ <1με, 0.01˚C, <10Pa resolution➡ Cross-sensitivity abating/compensation

➡ Miniature size (∅125μm, ∅40μm custom)➡ Lightweight, non-invasive, embeddable➡ Versatile fiber coating and catheterization

➡ Punctual sensors➡ Multiplexed, switched, quasi-distributed➡ Integration (lab in a fiber)

➡ Immune to EMI, radiation, MRI➡ Fire-safe, passive device➡ No interference with existing equipment


EFPIEFPI: Fiber-optic Fabry-Perot interferometric sensor based on all-silica glass structure: (1) launch fiber, (2) diaphragm, (3) capillary

Capillary

Launch SM fiber

Diaphragm MM fiber

AIR-GAP

(optionalFBG)

Single-mode fiberA

ir-ga

pD

iaph

ragm

Capillary

Ld


UL EFPI (pre-etch)

L = 20.6μm

Air-gap length LFP Spectrum ~ S0 + k cos[4πL/λ]


UL EFPI (pre-etch)

Pressure

Air-gap length L = L0 - Sp ΔPFP Spectrum ~ S0 + k cos[4π(L - Sp ΔP)/λ]Temperature: L = L0 - Sp ΔP + ST ΔT ⇒ FBG

L0 - Sp ΔP

L


UL EFPI (pre-etch)

Sp = 1.60 nm/kPa


Commercial EFPIEFPI head: 200µm

Encapsulation: 500µm Input fiber: 125µm


Commercial EFPI


Pressure detectionRMSE = 2.29 mmH2O

RMSE = 1.30 mmH2O


Pressure detectionRMSE = 2.29 mmH2O

RMSE = 1.30 mmH2O

RMSE = 2.29 mmH2O = = 0.21 mmHg


Improved detection

D. Tosi, S. Poeggel. G. Leen, E. Lewis, “Adaptive filter-based interrogation of high-sensitivity fiber optic Fabry-Perot interferometry sensors,” Sensors and Actuators A: Physical, in press


Fiber Bragg grating (FBG)

FBG = fiber optic filterFBG cascade ⬌ Multiplexing


Fiber Bragg grating (FBG)

•Information encoded in FBG optical spectrum•Linear dependance on strain and temperature•Top performance sensor•Easy interrogation

Reflected Bragg wavelength shifts linearly with variation of tensile strain and temperature


Fiber Bragg grating (FBG)Strain + temperature encoded in the sensing element

Strain: can be converted into force, by packageTemperature: for sensing, and compensation


Draw-tower grating

IOS hypertermia sensor: 5 FBG in 3 cm


Long period grating (LPG)


EFPI/FBG


EFPI/FBG

Δλ(ΔT, ΔP)

ΔL(ΔT,ΔP)


Detuning: 0.03 kPa/°C

-96% glass-99.6% mould

Cross-sensitivity


White light setup

...

...

...

.

.....

.

..

Switch

SLED

FBGA

Courtesy of Politecnico di Torino


White light setup

...

...

...

.

.....

FBG matrix

.

..

Switch

SLED

FBGASwitch Circulator

SLED

FBGA

Courtesy of Politecnico di Torino


Coherent light setupCourtesy of Politecnico di Torino

Switch

Laser array

Laser controller

Photodiode

...

...

...

.

.....

FBG matrix

.

..

Coherent light setup


...

...

...

.

.....

FBG matrix

.

..

Switch

Laser array

Laser controller

Photodiode

Laser PhotodiodeTEC

Circulator SwitchCourtesy of Politecnico di Torino


Interrogation

White light Coherent light

Encoding

Resolution

Throughput

Switching

# Sensors

Cost (box)

Stability

Wavelength Amplitude

1 pm (150 pm) << 1 pm

1-100 Hz total >kHz/channel

1/N * W 1/(N*W)

2-50/channel <10

$12k $2.5k

Excellent Low


Further integration

➡ Lab in a fiber‣Integration of several sensing units in a single fiber‣FBG (array), LPG, EFPI + bio/chemical (SPR)

➡ Quasi-distributed‣Dense monitoring of parameters, localized‣Bundle of EFPI, array of FBG, combination EFPI/FPI

➡ Cross-compensation‣Sensing parameter + temperature + ref. index‣Compensation matrix, detuning


Pigtail catheter


Pigtail catheter

4F

French(F) = 1/3mm

Contrast liquid

Excess bending

2x probes (distal)


Foley catheter

Urology catheter, bi-sex


Foley catheter

FO

1cm

4F

Side holes allow infusionInfusion + uroflowmetry

Seal: epoxy or medical tape


Needle/trocar

Radiofrequency ablation needle


Needle/trocar(1) Insert FO probe/bundle, retracted

(2) Expand/block into position

(optional: cut needle arms to desired length)

(3) Push and project fibersTrocar provides blockage


Cardiovascular


Miniature size


Immunity

➡ Excellent sensitivity to press., temp., strain➡ ➡


➡ Punctual sensors➡ Multiplexed, switched, quasi-distributed➡

➡ Immune to EMI, radiation, MRI➡ ➡ No interference with existing equipment


Cardiovascular➡ Blood pressure monitoring

‣Localized: allows localizing the phenomena without

damping, spatial averaging, fluid transfer (walls)

‣Multi-sensor: 2x sensors for obstructions (FFR)

‣Requires high speed: 100 Hz hardware to detect pulse

‣Used in the study of vasodilators/vasoconstrictors,

localize the pressure effect (pilot project)


Fractional Flow Reserve


Fractional Flow Reserve2x optical fiber pressure

sensors allow direct detection of FFR, pre-

and post-sthenosis

Problems in long-term:- Drift: >5 mmHg/hr - Temperature compensation- Amplitude drifts


Intra-aortic balloon (IAB)


Fiber-optic IAB

Fiber-optic cable

Pressure detection

FO selling points:- better stability to patients movements- better reproduction of pulse peak


Setup phantomHeart simulator

Interrogator/processing

Heart pumping

Sensor positioning(short access)

EFPI spectrum

Pressure meas.

SpectrometerASE source

Heart pumpinginletFiber inlet


Cardio phantom


Stability (1 hr)

0 10 20 30 40 50 60

62.5

63

63.5

64

64.5

65

Time (min)

Pres

sure

(mm

Hg)

EFPIFluidic

0.63 mmHg

2.76 mmHg

Typical FO drift ~ 5 mmHg/hr. St. Jude drift: 4mmHg/10min


Ventricular assistDemonstration at Cleveland Clinic, Mar 2013

FPI positioning

Ventricular assist

Reference (fluidic)Pressure readout


Ventricular assistDemonstration at Cleveland Clinic, Mar 2013


Urodynamic


Miniature size


Immunity

➡ ➡ ➡


➡ Punctual sensors➡ Multiplexed, switched, quasi-distributed➡

➡ ➡ ➡ No interference with existing equipment


Urodynamic“Standard” invasive urodynamics: Mid-term (20-40 minutes) monitoring of the detrusor muscle pressure and flowmetry during a urology analysis that consists of infusion and voiding of the bladder

Why fiber-optic: - FO sensors have a better responsivity and lower damping than air-charged catheter- It is possible to fit multiple fibers in the bladder: change the way bladder obstructions are diagnosed


Urodynamic

Diagnostic based on nomogram: detrusor pressure vs uroflowmetry➡ Direct detection of bladder outlet obstruction (BOO)


In-vivo measurementInfusion (375ml) Urination

EFPI

Pico2000

Feasibility test with Federico II University, Naples.


In-vivo measurementFeasibility test with Federico II University, Naples.


In-vivo measurement

CoughStimulus

Urination

Feasibility test with Federico II University, Naples.


Direct BOO (proposal)

InterrogatorDifferential pressure measurementBladder outlet obstruction (BOO) diagnostic


RF ablation of tumors


Miniature size


Immunity

➡ ➡ ➡ Cross-sensitivity abating/compensation


➡ ➡ Multiplexed, switched, quasi-distributed➡ Integration (lab in a fiber)

➡ Immune to EMI, radiation, MRI➡ Fire-safe, passive device➡ No interference with existing equipment


RFA descriptionRadiofrequency thermal ablation (RFA):Achieving the complete ablation of a cancerous tumor by burning the tumor + surrounding by means of Joule effect. In RFA the heat field is generated through 5-50W RF

Tumor, up to 5cm size

Needle, 1mm diameter

Ablation, ~15min/cm

RF field


RFA in liverLiver tissue sets a specific problem: ebullience releases the watery part of cells, which conduct more than liver - the RF circuit is disconnected after 2-9 minutes

➡ Not possible for RFA to remove mid/large tumors, over 2 cm in diameter➡ RFA is performed at ~60˚C rather than >100˚C. Cells mortality not guaranteed➡ Need to resort to microwave ablation (MWA)➡ Biocompatible gels can isolate needle from ebullient cells

Numbers: 764k deceases (#3)


Heat distributionIR thermal camera - imaging

Is the model confirmed by localized sensors?Is it possible to increase RFA efficiency/duration?


Heat distributionIR thermal camera - imaging

Is the model confirmed by localized sensors?Is it possible to increase RFA efficiency/duration?


Ex-vivo - setupExperiments with Universita’ di Pavia, San Matteo Hospital, Politecnico di Milano


Ex-vivo experimentsExperiments with Universita’ di Pavia, San Matteo Hospital, Politecnico di Milano

8mm



5mm



1mm


Preliminary conclusionsThe preliminary results obtained with EFPI/FBG do not match the physical model, nor the thermal camera imaging.

We observe during ablation a higher temperature, and higher pressure than expected (105˚C and 80 kPa).

Denser monitoring is needed to have a full reproduction of the physical phenomena.

Is it possible to increase the RFA efficiency, by online monitoring of pressure/temperature field?


Robotic surgery


Miniature size


Immunity

➡ Excellent sensitivity to press., temp., strain➡ <1με, 0.01˚C, <10Pa resolution➡ Cross-sensitivity abating/compensation

➡ Miniature size (∅125μm, ∅40μm custom)➡ ➡

➡ ➡ Multiplexed, switched, quasi-distributed➡ Integration (lab in a fiber)

➡ Immune to EMI, radiation, MRI➡ ➡


Robotic surgery•Integration of miniature FO sensors in surgical tool

•Measurement of force: 3D lateral + axial, return haptic

•Microsurgery (vitreoretinal surgery).

•Size matter! <125μm attractive, 40μm fibers for animal...

Da Vinci surgical tool: insufficient resolution to address microsurgery procedures. Need for a surgical tool that embeds sensors with <mN force detection + temperature compensation, to return a haptic feedback to the doctor.


Tool shafts

X. Liu, I. Iordachita, X. He, R. T. Taylor, J. U. Kang, “Miniature fiber-optic force sensor based on low-coherence Fabry-Perot interferometry for vitreoretinal microsurgery,” Biomedical Optics Express, v. 3, n. 5, 2012


Robotic surgery sensors

•Two alternative technologies: EFPI, FBG

•FBG in a spring configuration, to translate force to strain

•Low sensitivity: 10 mN ⇢ 1 pm (1με)•It needs temperature compensation

•EFPI promising, but larger size

•Transfer of axial forces through the capillary

•Proposal: all-EFPI configuration, axial+lateral+temperature


Conclusions➡ Optical fiber sensors are well on their way to address

medical opportunities, usually in multiB markets➡ Research emphasis on multi-sensing structures: lab-in-a-

fiber, quasi-distributed, dense monitoring➡ Scalability is a key factor for transitioning from lab to

market, but compatibly with disposable cost➡ Emerging applications raise the bar for sensing

complexity: size, integration, mechanical prop., catheters➡ Biocompatibility is a key issue: prevalence of all-glass

structures, most packages not FDA-compliant!


Acknowledgments‣ Federico II University - Urologic Clinic

‣ Universita’ di Pavia, Politecnico di Milano

‣ Cleveland Clinic

‣ FP7 Marie Curie (299985-PROBESENSE)

‣ Science Foundation Ireland (RFP/ECE2898)

‣ Enterprise Ireland (IP-2012-0166-Y)

‣ University of Limerick, MSSI and CES depts.


➡ Cooperation➡ Partnerships➡ Funding proposals... are welcome...

Thank you - Xie xie

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Daniele Tosi - OFSRC presentation at Jiliang University

Technology