Degradation of Liquid Degradation of Liquid Embolic PolymerEmbolic Polymer

- - A Pulsatile Flow ModelA Pulsatile Flow Model

BME 440 DesignBME 440 Design

Group 1Group 1

October 31, 2005October 31, 2005

OverviewOverview

Previous TechniquesPrevious Techniques

Current StudiesCurrent Studies

Future applicationsFuture applications

Aneurysm BackgroundAneurysm Background•Aneurysm – Out pouching of a blood vessel

•Caused by weakened internal elastic lamina

•Clinical

•Ruptured or un-ruptured

•Rupture causes hemorrhage

•Rupture rate 10-25 per 100,000 population

•60,000 annually in the U.S. suffer from aneurysms – Half ruptured, half not.

•If the aneurysm ruptures, the damage is as follows: 35% die, 30% suffer severe morbidity, 35% recover

•Mechanical degradation of polymer

•Embolism

Previous TechniquesPrevious Techniques

• Surgery

• Removal of Aneurysm

• Platinum coil (Gugliemi Coils)Gugliemi Coils)

• CatheterizationCatheterization

• InsertionInsertion

• ManeuverabilityManeuverability

Previous MaterialsPrevious Materials

•Liquid acrylics

•Glue-like

•Ethylene vinyl alcohol

•Toxic solvent- DMSO

•Alginate

• Conflicting evidence

•Growth factors

Types of ModelsTypes of Models

• In-vitroIn-vitro• GlassGlass• PolycarbonatePolycarbonate• PlexiglassPlexiglass

• In-vivoIn-vivo• Porcine Porcine • CanineCanine

Polymer DeliveryPolymer Delivery• Catheter ChoiceCatheter Choice

• Single line catheterSingle line catheter• Concentric catheterConcentric catheter• Efficiency Efficiency

• High percentage of High percentage of polymer deposition polymer deposition

• Re-canalization Re-canalization • Side by side catheterSide by side catheter

• In-vitro (can control flow)In-vitro (can control flow)• Injection of polymer; no Injection of polymer; no

initial flow initial flow • In-vivo (constantly flowing)In-vivo (constantly flowing)

• Injection of polymer; Injection of polymer; initial flowinitial flow

Catheter Injection

Injection Against FlowInjection Against Flow

• Minimizing the Effects of Flow

• Surgical Clip

• Balloon

• Stent

Design ImplementationDesign Implementation•2D and 3D models

•Watertight

•2D – Block geometry with machined aneurysm

•Easy to clean

•Large gasket

•Adaptable

•Pressure supplied by clamping mechanism

•Bifurcation and Wall Aneurysm•Adaptable 2-in-1 architecture

•Removable screw mechanism

End View

Side View

Rubber Seal

MS.Paint MS.Paint Schematics Schematics of Modelof Model

Gasket MaterialsGasket Materials•NecessitiesNecessities

•Water TightWater Tight

•CompressibleCompressible

•DurableDurable

•Compression Set Compression Set

ResistanceResistance

Dow CorningDow Corning

Flow MechanismFlow Mechanism•Flow Pump OptionsFlow Pump Options

•Diaphragm (Pulsatile)Diaphragm (Pulsatile)•Peristaltic (Steady)Peristaltic (Steady)

•Important CharacteristicsImportant Characteristics•Biological similarityBiological similarity

•Variable flow rateVariable flow rate

•Length of useLength of use

•Ease of useEase of use

•CostCost

Various PumpsVarious Pumps•SP100VC ($159) – Cased Variable Flow SP100VC ($159) – Cased Variable Flow Peristaltic PumpPeristaltic Pump

•Flow Range: 0.03ml/min to 13ml/minFlow Range: 0.03ml/min to 13ml/min

•Control: KnobControl: Knob

•SP100VO (OEM) SP100VO (OEM) ($59)($59) – Variable Flow – Variable Flow Peristaltic PumpPeristaltic Pump

•Flow Range: 0.09ml/min to 13ml/minFlow Range: 0.09ml/min to 13ml/min

•Control: Vary VoltageControl: Vary Voltage

•SP200VC ($169) – Cased Variable Flow SP200VC ($169) – Cased Variable Flow Peristaltic PumpPeristaltic Pump

•Flow Range: 0.06ml/min to 62ml/minFlow Range: 0.06ml/min to 62ml/min

•Control: KnobControl: Knob

•SP100VOBL ($179) – Brushless DC SP100VOBL ($179) – Brushless DC Variable Flow Peristaltic PumpVariable Flow Peristaltic Pump

•Flow Range: 0.09ml/min to 20ml/minFlow Range: 0.09ml/min to 20ml/min•Control: Vary VoltageControl: Vary Voltage•Continuous Use – Long LifeContinuous Use – Long Life

•PM10.001 ($135) – Miniature PM10.001 ($135) – Miniature Diaphragm Pump. (Pulsatile Flow)Diaphragm Pump. (Pulsatile Flow)

•Max Flow: 100ml/minMax Flow: 100ml/min•Control: Vary input voltageControl: Vary input voltage

APTAPT

Fluid and Pressure ConcernsFluid and Pressure Concerns

• Desired Fluid FlowDesired Fluid Flow• 70-100 cm/min velocity70-100 cm/min velocity• 1-5 mm tube diameter1-5 mm tube diameter• Yields a flow range of .55–19.7 ml/min (Q = Yields a flow range of .55–19.7 ml/min (Q =

v*a)v*a)• PressurePressure

• Increased flow rate = increased pressureIncreased flow rate = increased pressure• Pressure range helps find possible system Pressure range helps find possible system

materials (i.e. gaskets, pipes, tubing, etc)materials (i.e. gaskets, pipes, tubing, etc)

Degradation MonitoringDegradation Monitoring

• High Speed CameraHigh Speed Camera• Monitors individual particle lossMonitors individual particle loss• CostlyCostly• Image distortion due to materialsImage distortion due to materials• Software OptionsSoftware Options

• Image differentiation analysisImage differentiation analysis• Computer Aided Speckle Interferometry (CASI)Computer Aided Speckle Interferometry (CASI)

• Fine Mesh GauzeFine Mesh Gauze• Downstream collection of particlesDownstream collection of particles• Smaller particles can escape Smaller particles can escape • Inhibits flowInhibits flow

Degradation Monitoring (Cont)Degradation Monitoring (Cont)

• Fiber Optic CameraFiber Optic Camera• Evades material distortionEvades material distortion• Site specificSite specific• Hard to implement without hindering flowHard to implement without hindering flow• Resolution and speedResolution and speed

Versatility FeaturesVersatility Features

• Bifurcation vs. Side WallBifurcation vs. Side Wall• Steady Flow vs. Pulsatile FlowSteady Flow vs. Pulsatile Flow• Open Flow vs. Closed FlowOpen Flow vs. Closed Flow• Flow RateFlow Rate

Material ChoicesMaterial Choices

• GlassGlass• ExpensiveExpensive• Easily destroyedEasily destroyed• PrimitivePrimitive

• PlexiglassPlexiglass• CheapCheap• Mechanically StrongMechanically Strong• MachinableMachinable

• PolycarbonatePolycarbonate• Very similar to plexiglass. Very similar to plexiglass. • Slightly more expensive, but is better in most Slightly more expensive, but is better in most

categoriescategories

ConclusionConclusion

• Polymer to be tested: ChitosanPolymer to be tested: Chitosan• Model Structure MaterialModel Structure Material

• PolycarbonatePolycarbonate

• Gasket MaterialGasket Material• Silicon RubberSilicon Rubber

• Pump choicePump choice

AcknowledgementsAcknowledgements

Professor ChenProfessor Chen Professor StreyProfessor Strey Lester-machine shopLester-machine shop Professor BluesteinProfessor Bluestein

ReferencesReferences

1.1. Soga et al. Neurosurgery, 55(6):1401-1409, 2004.Soga et al. Neurosurgery, 55(6):1401-1409, 2004. All All figures, unless otherwise noted, are referenced from this paper.figures, unless otherwise noted, are referenced from this paper.

2.2. APT Instruments. Flow Pumps and Accessories.APT Instruments. Flow Pumps and Accessories. http://www.aptinstruments.com/http://www.aptinstruments.com/

3.3. Dow Corning. Rubber Applications and Markets.Dow Corning. Rubber Applications and Markets. http://www.dowcorning.com/content/rubber/rubberapps/app_gasket.asp?http://www.dowcorning.com/content/rubber/rubberapps/app_gasket.asp?WT.srch=1WT.srch=1