development of a patient-specific modular vascular phantom...

Development of a patient-specific modular vascular phantom with clinically relevant mechanical properties

Supervisor: Prof. Elena De Momi

Co-Supervisor: Dr. Helge Wurdemann

Student: Antonio Gallarello

852517

Academic Year: 2016-2017

Nome Cognome, assoc.prof. ABC Dept.

Cardiovascular Diseases

Antonio Gallarello [email protected]

2

Introduction

of deaths in 2013

of hospital inpatient

expenditure in 2015

18%

32%

$33bnCardiovascular device market value in 2015

• Average life expectancy reached 80.5 years in 2013 (OECD, 2015)

• 15% of population aged over 65 years in 2010expected to grow up to 27% in 2050

• Cardiovascular diseases remain the main cause of mortality in OECD countries

• They represent the highest share of inpatient expenditure in hospitals

• The global cardiovascular market is projected to grow with a Compound Annual Grow Rate of 6.6% (Grandviewresearch, 2016)

15% Aged over 65

80.5Up to

y.o.

Need of new devices able to reduce hospitalization costs and patient recovery time


Device validation procedure


3

Discovery +

Ideation

Invention+

Prototyping

ClinicalTrials

Product on

market

Invention+

Prototyping

• Researchers test the prototypes in controlled laboratory settings refining itaiming at reducing risk of harm in people

In vivo

x They are usually expensive

x They require ethical approval

x Animal-specific conditions

Complete animal anatomy

Need for human-like in vitro models which can be able to mimic patient-specific conditions and are physiologically shaped (Sulaiman et al., 2008)

In vitro

Can be cost-efficient

Do not require ethical approval

Controllable and repeatable

x Usually simplified models

Introduction


Vascular phantoms: a review


4

• Use:

• In-vitro device testing

• Particle Image Velocimetry (PIV)

• Training and rehearsal purposes

• Manufacturing:

• Rigid or flexible materials

• Idealised or patient-specific morphologies

• 3D Printing or traditional processes

Rigid patient-specific tortuous aneurysm for endovascular repair surgery simulation (Peerin et al., 2016).

Flexible phantom of aortic arch aneurysm for stenting procedure (Sulaiman et al., 2008)

Aortic arch and descending aorta 3D printed with HeartPrint Flex and used for testing a Intravascular Ultrasound Catheter (Poorten et al., 2016).

Introduction


Aim and objectives


5

Objectives

Development of a vascular phantom environment according to Kbasnytsia et al., 2016

Patient specific data

Human-like distensibility

MR Compatibility

Hard-wearing materials

Good transparency

Cost-effective

The phantom will be used at UCL for early-stage test of a new 2-DOFs catheter


The workflow

3D Reconstruction

Material evaluation

Phantom design

Validation protocols


6


3D Reconstruction


7

Methods

High quality Compute Tomography (CT) angiography:

• Contrast agent allows highlighting of the blood vessels.Im

agin

g3

D R

eco

nst

ruct

ion

Ref

inin

g

Segmentation and 3D reconstruction (3D Slicer):

• ROI selection and cropping

• Segmentation

• 3D model generation

STL mesh refining (Meshmixer, Autodesk):

• Undesired features removal


Materials


8

Mat

eri

als

• TangoPlus FLX 930 (Shore 27A), Stratasys

• Ecoflex® 00-30, Smooth-on

• Ecoflex® 00-50, Smooth-on

• Dragon skin® 00-30, Smooth-on

3D Printable material using Polyjet technology, it needs support material

Rubber-like silicones relying on traditional manufacturing procedures

Specimen preparation

Tensile testsMaterial

modelling�� ≝ �

��

��

�� + ��

�� + �� − � + �

�

�� − � ��

�

��

�

��

�� − �� ≝ �� − 3 +

1

�� − 1 �

Order i CoefficientsDragonskin µi αi Di

1 -4.63 -2.18 0.182 2.03 -1.20 0.003 2.81 -3.25 0.00

Eco-Flex 00-30 µi αi Di

1 4.49E-04 5.42 1.0622 3.74E-02 -4.17 0.00

Eco-Flex 00-50 µi αi Di

1 1.24E-04 7.37 0.652 6.09E-02 -4.75 0.00

TangoPlus D1 C10 C01

1 0.18 0.10 0.00

Ogden

Ogden

Ogden

Neo-HookeanUCL Internal Standards – Cardiovascular Eng. Lab

Methods


Boundary Conditions

Longitudinal Displacement andRotation

CircumferentialDisplacement andRotation

Simulation-I


9

Geometry Materials

Hollow-tube model

Cylindrical sector• TangoPlus FLX 930

[Neo-Hookean]

• Ecoflex® 00-30

[Ogden 2nd order]

• Ecoflex® 00-50

[Ogden 2nd order]

• Dragon skin® 00-30

[Ogden 3rd order]

Loadαr

t

r = 13.4 [mm]α = 20°

Variable thicknesst ϵ (0.5; 5) [mm]

Pressure on the internal surface

P(1)= 0.0106 MPa= 80 mmHg; P(2)= 0.0159 MPa = 120 mmHg

Methods


Simulation-II


10

Compliance= 2��

�∆⁄ � [��Displacement

If left to atmospheric pressure, all the materials experience too large deformations that would lead to non physiological conditions

A constrained configuration must be adopted for the phantom where its displacement can be controlled also acting on the environment surrounding it

Methods


Manufacturing-I: The phantom


11

EcoFlex 00-30 has been adopted to create the phantom with a human-like thickness of 2 mm

Inte

rnal

co

reIn

tern

al c

ore

Exte

rnal

Mo

uld

Exte

rnal

Mo

uld

Cas

tin

g p

roce

ss

Editing Slicing Printing

(PVA)

+2 mm

Editing Splitting

Methods


Manufacturing-II: The hosting system


12

Methods

Compliance chamber

Floating in water

Connection

Silicone phantom

Valves

Watertight acrylic box

½” BSP Connections


Validation protocols-I


Non-pulsatile validation Setup:

• Syringe pump

• Pressure sensor

Procedure:

Distensibility measure varying the level of water

in the compliance chamber

D=∆�

��

∆� [��]

13

Methods

Compliancemodule


Results I


Results

Results of the non-pulsatile validation where the range of achievable compliance has been investigated.

Std [1/mmHg] 1.94 0.46 2.09 1.83 1.47 1.38 0.55 1.18 0.73 [10-5]

The achievable compliance has very high repeatability Increasing the size of the chamber higher values could be reached

14

(Baeck)

Compliancemodule


Validation protocols-II


Pulsatile validation Setup:

• Vivitro Pulse Duplicator

• HFR (50 fps) camera

• Catheter tip pressure sensor

• Throttle valve for lumped resistance

Procedure

• 10 cycles with 70 bpm H.R.

• 9 configurations

• Tracking algorithm for vessel

deformation

Aortic valve

VentricleMitral valve

Atrium

Systemic resistance

Compliance

Connection With aortic valve

Lumped resistance

15

Methods

Chessboard for plane detection

HFR Camera


Results II


Results of the pulsatile validation for each configuration

16

Results


Results II


17

Compliance

Res

ista

nce

Pressure waveform for each configuration

Results


Validation protocols-III


MR

Setup:3T MR Scan

Procedure:MR scans of the phantom were performed in aninflated (120 mmHg) and in a deflated condition(0 mmHg)

18

Methods


Results III


19

MRI results of the phantom scan

2nd scan

1st scan

Chemical shift artefactscan be attenuated withFluid Attenuated InversionRecovery (FLAIR)

Results


Conclusion & Future work


Discussion

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Patient specific data

Human like distensibility MR Compatibility

Hard-wearing materials

Good transparencyCost-effective

Further advance this model to cover the entire morphology of the aorta in a modular manner.

Include pathological conditions such as aneurysms and dissections.

Other materials could be investigated as transparency might allow PIV studies.

Future work

Thank you!

development of a patient-specific modular vascular phantom...

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