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
daniele.tosi@ul.ie
dan82ddt
www.ofsrc.ul.ie

About
University of Limerick
Optical Fibre Sensors Research Centre
[Marie Curie Fellow @ OFSRC]

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

Partnerships
Cleveland Clinic
EFPI cardiovascular/demo
Johns Hopkins
Robotic surgery

UL, OFSRC
Pointec (licensing)

Harbin Inst. Technol.
Cyprus IT (EFPI partner)
Staff exchange partnership

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

Shenzhen
Custom catheters supplier


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


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

AIR-GAP

Launch SM
fiber


Diaphragm
MM fiber

UL EFPI (pre-etch)
Air-gap length L
FP Spectrum ~ S0 + k cos[4πL/λ]

L = 20.6μm

Single-mode ﬁber

phragm
Dia
ir-gap
A

L
d

Capillary

UL EFPI (pre-etch)


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

L0 - Sp ΔP

Pressure

Sp = 1.60 nm/kPa

L

Commercial EFPI
EFPI head: 200µm

Encapsulation: 500µm

Input fiber: 125µm


Commercial EFPI


Pressure detection
RMSE = 2.29 mmH2O

RMSE = 1.30 mmH2O


Pressure detection
RMSE = 2.29 mmH2O

RMSE = 2.29 mmH2O =
= 0.21 mmHg
RMSE = 1.30 mmH2O


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 ﬁlter
FBG cascade ⬌ Multiplexing

•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

Strain + temperature encoded in the sensing element

Strain: can be converted into force, by package
Temperature: 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)


Cross-sensitivity
Detuning: 0.03 kPa/°C
-96% glass
-99.6% mould


White light setup
Courtesy of Politecnico di Torino

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.
.

.
.
.

...
...
...

Switch
SLED
FBGA

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.
.

White light setup

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.
. FBGA

.
.
.

FBG matrix
...
...
.
.
.
...
SLED

Switch
SLED
FBGA

Switch

Circulator


Coherent light setup

.
.
.

.
.
.

FBG matrix
...
...
.
.
.
...

Switch
Laser
controller
Photodiode

Laser array


Circulator
Coherent light Switch
setup

.
.
.

Laser

FBG matrix
...
...
TEC
. Photodiode .
.
.
.
.
...

Switch
Laser
controller
Photodiode

Laser array


Interrogation
White light

Coherent light

Encoding

Wavelength

Amplitude

Resolution

1 pm (150 pm)

<< 1 pm

Throughput

1-100 Hz total

>kHz/channel

Switching

1/N * W

1/(N*W)

# Sensors

2-50/channel

<10

Cost (box)

$12k

$2.5k

Stability

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
Contrast liquid

4F
2x probes (distal)

French(F) = 1/3mm

Excess bending


Foley catheter

Urology catheter, bi-sex

Foley catheter
Seal: epoxy or medical tape

1cm
FO
Infusion + uroflowmetry

4F

Side holes
allow infusion


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 fibers
Trocar provides blockage


Cardiovascular
Top-notch
Performance
Miniature size
Distribution and
Integration
Immunity

➡
➡
➡
➡
➡
➡
➡
➡

Miniature size (∅125μm, ∅40μm custom)
Lightweight, non-invasive, embeddable
Versatile ﬁber coating and catheterization
Punctual sensors
Multiplexed, switched, quasi-distributed

➡


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 Reserve
2x optical fiber pressure
sensors allow direct
detection of FFR, preand post-sthenosis

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

Intra-aortic balloon (IAB)


Fiber-optic IAB
Pressure detection
FO selling points:
- better stability to
patients movements
- better reproduction
of pulse peak
Fiber-optic cable


Setup phantom
Heart simulator

Spectrometer
ASE source

EFP
I sp
ectr

Heart pumping
Fiber inlet

Pres
sure

um

mea
s.

Sensor positioning
(short access)

Interrogator/processing

Cardio phantom


Stability (1 hr)
65

EFPI
Fluidic

0.63 mmHg

Pressure (mmHg)

64.5
64
63.5
63

2.76 mmHg

62.5
0

10

20

30

40

50

60

Time (min)

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

Ventricular assist
Demonstration at Cleveland Clinic, Mar 2013

FPI positioning
Ventricular assist

Reference (ﬂuidic)

Pressure readout


Ventricular assist
Demonstration at Cleveland Clinic, Mar 2013


Urodynamic
Top-notch
Performance
Miniature size
Distribution and
Integration
Immunity

➡
➡
➡
➡
➡
➡
➡
➡
➡

Punctual sensors

➡
➡


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 measurement
Feasibility test with Federico II University, Naples.

Infusion (375ml)

Urination

EFPI

Pico2000


In-vivo measurement


In-vivo measurement

Urination
Cough

Stimulus


Direct BOO (proposal)

Differential pressure measurement
Bladder outlet obstruction (BOO) diagnostic

Interrogator


RF ablation of tumors
Top-notch
Performance
Miniature size
Distribution and
Integration
Immunity

➡
➡
➡
➡
➡
➡
➡
➡

Integration (lab in a ﬁber)

➡ Fire-safe, passive device


RFA description
Radiofrequency 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

Needle, 1mm diameter
Ablation, ~15min/cm
Tumor, up to 5cm size

RF field


RFA in liver
Liver 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 distribution
IR thermal camera - imaging

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

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


Ex-vivo experiments

8mm


Ex-vivo experiments

5mm


Ex-vivo experiments

1mm


Preliminary conclusions
The 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
Top-notch
Performance
Miniature size
Distribution and
Integration
Immunity

➡ <1με, 0.01˚C, <10Pa resolution
➡ Miniature size (∅125μm, ∅40μm custom)
➡
➡
➡
➡ Multiplexed, switched, quasi-distributed
➡ Integration (lab in a ﬁber)
➡
➡


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 ﬁberoptic 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-aﬁber, 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.

Thank you - Xie xie

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

Daniele Tosi - OFSRC presentation at Jiliang University

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