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Dr. Antonios Lontos

Associate Professor

The project ΥΓΕΙΑ/ΔΥΓΕΙΑ/0311/27 (ΒΙΕ) was co-financed by the European Regional Development Fund and the

Republic of Cyprus through the Research Promotion Foundation.

Scientific Session: Track SS8

Optimizing the diagnostic value of Myocardial Perfusion Imaging

using a dynamic phantom assembly

Construction of inflatable lungs to simulate

respiratory motion in Myocardial Perfusion Imaging (MPI)

XIV MEDITERRANEAN CONFERENCE ON MEDICAL AND BIOLOGICAL ENGINEERING AND COMPUTING

MARCH 31ST - APRIL 2ND 2016, PAPHOS, CYPRUS

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1. Introduction

2. Image processing and 3D design

3. Design and construction of the moulds

4. Construction of inflatable lungs

5. Conclusions

Contents

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Slide 3/25 1. Introduction

• One of the most common heart disease is the Coronary Artery Disease (CAD)

• Coronary artery stenosis can be evaluated by Myocardial Perfusion Imaging (MPI)

• Myocardial Perfusion Images (MPI) is influenced not only by the cardiac motion but also by various other

parameters such as the respiratory motion

Computational models and patient data are useful.

But mechanically controlled phantoms (with inflatable lungs and heart beating) are very

important to optimize MPI studies.

Research scope

• Accurate design and Construction of inflatable lungs with lung-equivalent material.

• Validation of the inflatable lungs

• Development of a respiratory-diaphragm motion phantom, and implement it within the existing cardiac

phantom

• Help in validation of new protocols before implementation using phantom.

• Educational purposes to physicians, medical physicists, technicians and students

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Slide 4/25 2. Image processing and 3D design

Anthropomorphic phantom for testing

Thorax-CT flash-anatomy 86 planes

It is a fully tissue equivalent and represents an average male in size and shape. Both lungs and heart will be operating by special equipment for the actual simulation of the respiratory motion and heart beating

Using special software, lungs can be design. From each image, the outside contour can be collected. By attaching the one contour to other in specific height the real 3D design can be constructed. As it is shown the geometrical shape of the lungs is very complicated and difficult to construct

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Slide 5/25 2. Image processing and 3D design

Left and right lung shape The shape of both lungs was slightly changed in order to predict smoother geometry The total volume of the lung was the same as measured from CT scan images The left lung volume is 510 ml and the right lung volume is 565 ml

• The inside volume filled by tissue equivalent material • Upper openings help respiratory simulation and filling of the lung with the tissue

equivalent material • Transparent acrylic material was attached at the top of each lung • Elastic tubes were connected with the acrylic material and air pumps • Using these tubes and controlled air pump, respiratory motion can be simulated

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Left lung assembly Right lung assembly

2. Image processing and 3D design

Silicon membrane thickness = 2mm Main consideration: Anatomy, strength and elasticity of the silicon

Air tight fittings for air tubes

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Slide 7/25 3. Design and construction of the molds

Design of the different parts of the left lung mold

Design and construction considerations

(1) Better injection of the silicon rubber, (2) Better solidify of the material, (3) Silicon lung removal,

(4) Dimensioning and injection parameters, (5) Assemble and disassemble of the different mold parts

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Construction of aluminum moulds for heart and lungs using CNC machines

4-axis Computer Numerical Control machine

3. Design and construction of the molds

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Preparation of CNC manufacturing using special CAM software

3. Design and construction of the molds

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Construction of left lung mold

• The assembly and disassembly of lung molds is very important • Fit perfectly each other in order to leave smooth and uniform shape • Assembly and disassembly procedure was described and followed

3. Design and construction of the molds

• Material aluminum 6061 T6, which is very good material for injection molding • Easy to manufacture and can predict very good and shiny surfaces • Shiny surfaces are very important for the silicon lungs quality

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Molds for the heart - inner part

3. Design and construction of the molds

Previous Research work: Heart design

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Moulds for the heart – outer part

3. Design and construction of the molds

Previous Research work: Heart design

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TYPICAL GENERAL CHARACTERISTICS

ELASTOSIL M 4645 A/B Silastic 3481

Color Transparent White

Mixed viscosity, mPa.s 50,000 25,000

Elongation at break, % 330 560

Hardness, (Shore A) 40 21

Tensile strength, MPa 5 4.9

Tear strength, N/mm 28 26

Base and Curing Agent mixture (by weight)

10:1 100:5

Curing time 12 hours 7 days

Typical properties of the silicon materials

Two different silicon rubbers were used: 1. Elastosil M4645 A/B, RTV-2 2. Silastic 3481, Hardener Silastic 81

• Tissue equivalent materials • Transparent for visibility during the experimental set up and procedure • Excellent mold release, fast and non-shrink cure at room temperature

4. Construction of inflatable lungs

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Construction of left lung mold and equipment

Special equipment: • Weight scale: High accuracy weight scale was use during the mixing of silicon and hardener. • Vacuum pump: Vacuum pump was used for removing air bubbles after mixing and stirring of the two

components. • Injection molding equipment: A special cylinder was used for the injection of silicon from the bottom

opening of the mold.

4. Construction of inflatable lungs

The mold cavity was filled from the bottom to the top in order to release air and avoid trapping air bubbles.

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Silicon left and right lungs

Left lung

Right lung from white silicon rubber

Right lung

White silicon rubber White and transparent silicon rubber

4. Construction of inflatable lungs

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Silicon lungs

• Both materials have the same size and shape with slight different in properties and color. • Special thermoplastic boundaries for the limitation of the lungs expansion during inhalation (air

pumping)

Thermoplastic boundaries

4. Construction of inflatable lungs

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Silicon heart final construction, transparent silicon

Inner part Outer part

Inner part Outer part

4. Construction of inflatable lungs and heart

Previous Research work: Heart design

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Inner part testing

Outer part testing

NO pressure With pressure

NO pressure With pressure

4. Construction of inflatable lungs and heart

Previous Research work: Heart design

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Silicon heart final assembly and testing

NO pressure With pressure

4. Construction of inflatable lungs and heart

Previous Research work: Heart design

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• A tissue equivalent material was inserted in the lungs cavity

• This material has similar characteristic mass and porosity as lung tissue

• The inserted material help in simulating the real movement of the lungs during respiratory

• Supports were placed on the top and the bottom of lungs

• All the materials that used in the phantom can be characterized as tissue equivalent

• Two compact size pumps with suction and blowing ports were used as vacuum pumps and small compressor (maximum flow of a 17,5 lt/min, pressure of 1 bar)

• Two electro-proportional valves control the respiratory motion (air pressure with respect to time)

• A special water tank was use to validate lungs volume expansion

o Expiration 510 ml and 565 ml, Inhalation up to 700 ml and 775 ml (Test for every 50 ml, tidal volumes 350-600 ml ), 2% Deviation

o Respiratory cycles 10-14 breaths per minute (± 20 ms)

Construction of the respiratory motion simulator for the phantom

4. Construction of inflatable lungs

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Cage construction for better simulation of the respiratory motion

Thermoplastic cage Thermoplastic cage with silicon lungs

4. Construction of inflatable lungs

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Slide 22/25 4. Construction of inflatable lungs

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Slide 23/25 4. Construction of inflatable lungs

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Slide 24/25 5. Conclusions

• Human-sized inflatable lungs were constructed to simulate the respiratory motion in MPI

studies.

• CT slices were used to design the lungs.

• Left and Right lungs with initial volumes 510 and 565 mL.

• Each lung was covered with a 1-mm-thick thermoplastic structure to properly inflate in

all directions in a physiologically correct manner.

• The tidal volume and the breathing cycle of the inflatable lungs were mechanically

validated.

• The tidal volume of the lungs was also validated from CT acquisitions using the OsiriX

imaging software.

• Mechanically controlled phantoms are useful to investigate Myocardial Perfusion

Imaging.

CONCLUSIONS

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The project ΥΓΕΙΑ/ΔΥΓΕΙΑ/0311/27 (ΒΙΕ) is co-financed by the European Regional Development Fund and the Republic of Cyprus through the Research Promotion Foundation.

The author would like to thank: - Yiannis Parpottas, Ph.D. in Nuclear Physics - Isabelle Chrysanthou, Ph.D. in Medical Physics - Antonis Antoniou, Ph.D. in Mechanical Engineering - Panayi Panayiotis (CNC manufacturing , Moulds Construction) “Machinery Panagiotis J. Panagi”

Thank you for your attention