AuthorsAuthors

Timothy EngTimothy EngTeam LeaderTeam Leader

Mary LimMary LimBWIGBWIG

Lauren HensleyLauren HensleyBSACBSAC

April ZehmApril ZehmCommunicatorCommunicator

Client & AdvisorClient & Advisor

Dr. Victor Haughton, M.D.Dr. Victor Haughton, M.D.UW Department of RadiologyUW Department of Radiology

UW Medical SchoolUW Medical School

Professor Justin WilliamsProfessor Justin WilliamsDepartment of Biomedical Department of Biomedical

Engineering Engineering

AbstractAbstract A physical model of the human hindbrain A physical model of the human hindbrain

and upper cervical spinal canal was desired and upper cervical spinal canal was desired to study the effects of varying dimensions to study the effects of varying dimensions and obstructions on pressure changes within and obstructions on pressure changes within the spinal canal. A prototype was assembled the spinal canal. A prototype was assembled to roughly mimic the Chiari I malformation. to roughly mimic the Chiari I malformation. The final design is a multi-piece module, The final design is a multi-piece module, which houses a funnel-like cavity. The which houses a funnel-like cavity. The module will be used with an electronically module will be used with an electronically controlled piston pump and pressure will be controlled piston pump and pressure will be quantified using a transducer. Future work quantified using a transducer. Future work includes increasing the complexity of the includes increasing the complexity of the cavity within the module by replicating CT cavity within the module by replicating CT scans of this part of the spinal canal.scans of this part of the spinal canal.

Problem StatementProblem Statement

The goal of this project was to create a The goal of this project was to create a life-size physical model of the human life-size physical model of the human hindbrain and upper cervical spinal hindbrain and upper cervical spinal canal. This will be used to study how canal. This will be used to study how varying dimensions and obstructions varying dimensions and obstructions affect cerebrospinal fluid (CSF) flow in affect cerebrospinal fluid (CSF) flow in terms of pressure. Oscillatory flow is terms of pressure. Oscillatory flow is required in the model, and pressure required in the model, and pressure must be quantifiable. must be quantifiable.

Background InformationBackground Information Chiari I MalformationChiari I Malformation

– Brainstem and cerebellar tonsils (brain Brainstem and cerebellar tonsils (brain tissue) lower into cranial vaulttissue) lower into cranial vault Obstructs CSF flowObstructs CSF flow Causes increased PRESSURE on brain and in Causes increased PRESSURE on brain and in

spinal canalspinal canal

– Symptoms: headaches, pain, dysphagia, Symptoms: headaches, pain, dysphagia, numbness, motory and sensory numbness, motory and sensory inhibition, loss of consciousnessinhibition, loss of consciousness

– Treatment: surgery (physical Treatment: surgery (physical enlargement)enlargement)

Anatomy of Chiari IAnatomy of Chiari I

http://tribble.missouri.edu/ns/chiari/aboutchiarimalformation.htm#chiari

Bernoulli’s LawBernoulli’s Law

P + ½ P + ½ ρρvv22 = = constantconstant

Pressure is Pressure is proportional to proportional to diameter of tubediameter of tube

Velocity is inversely Velocity is inversely proportional to proportional to diameter of tubediameter of tube

Design ConstraintsDesign Constraints Must replicate anatomical size of Must replicate anatomical size of

human spinal canal and cranial vaulthuman spinal canal and cranial vault Requires oscillatory flow that mimics Requires oscillatory flow that mimics

actual CSF flowactual CSF flow Pressure measured accurately along Pressure measured accurately along

various pointsvarious points Ability to interchange piecesAbility to interchange pieces Must attach to provided pumpMust attach to provided pump MRI compatibleMRI compatible

Chosen DesignChosen Design Two working Two working

modulesmodules– Replicate CT scans of Replicate CT scans of

normal patients and normal patients and Chiari I malformationChiari I malformation

– Oscillatory flow Oscillatory flow induced by piston induced by piston pumppump

– Interchangeable, Interchangeable, polycarbonate piecespolycarbonate pieces

– Pressure quantifiable Pressure quantifiable via transducervia transducer

Problems EncounteredProblems Encountered

Budget ConstraintsBudget Constraints– Expected cost exceeded $200 limitExpected cost exceeded $200 limit

Time ConstraintsTime Constraints– 3-4 hours/block; 20 blocks needed3-4 hours/block; 20 blocks needed

Available Equipment ConstraintsAvailable Equipment Constraints– Shop machinery inadequate for small Shop machinery inadequate for small

scale designscale design– Accuracy and precision would be Accuracy and precision would be

compromisedcompromised

Design ModificationsDesign Modifications

CT scan images replaced with range CT scan images replaced with range of cylinders of cylinders – Form inner funnel-like shape in moduleForm inner funnel-like shape in module

Pressure measured in same fashionPressure measured in same fashion Maintains interchangeability of Maintains interchangeability of

piecespieces Meets design specifications; Meets design specifications;

approved by client as acceptable approved by client as acceptable (but temporary) solution to problem(but temporary) solution to problem

Prototype ConstructionPrototype Construction

Acquired materialsAcquired materials– Polycarbonate sheetPolycarbonate sheet– Non-magnetic Non-magnetic

stainless steel screwsstainless steel screws– Adaptors for pumpAdaptors for pump– Flexible tubingFlexible tubing

Piecewise Piecewise ConstructionConstruction

Testing for Testing for functionalityfunctionality

Schematic of PrototypeSchematic of Prototype

Side view schematic

Functional PrototypeFunctional Prototype Polycarbonate Polycarbonate Inexpensive Inexpensive Measures pressure Measures pressure

changes at various changes at various points within modulepoints within module

Easy to assemble Easy to assemble and interchange and interchange piecespieces

Simple design can be Simple design can be modified to utilize CT modified to utilize CT scans/improve scans/improve accuracy of modelaccuracy of model

Piston PumpPiston Pump

Will be used by Will be used by clientclient

Generates Generates oscillatory flowoscillatory flow

Electronically Electronically controlledcontrolled

Compatible with Compatible with multiple multiple modulesmodules

Placement of the ModulePlacement of the Module

Module Module connected to connected to pump via plastic pump via plastic adaptorsadaptors

Fluid flows Fluid flows through module through module in oscillatory in oscillatory manner (sine manner (sine function can be function can be generated)generated)

Cost AnalysisCost Analysis

3/8” 12”x24” polycarbonate sheet3/8” 12”x24” polycarbonate sheet $29.76$29.76 6” non-magnetic stainless steel6” non-magnetic stainless steel

screwsscrews with 1/4” diameter (4)with 1/4” diameter (4)

+ wing nuts (4)+ wing nuts (4) $ 5.06$ 5.06 1/4” flexible plastic tubing (3 ft)1/4” flexible plastic tubing (3 ft) $ $

0.870.87 Plastic AdaptorsPlastic Adaptors $ 0.00$ 0.00 Goop MarineGoop Marine (rubber sealant)(rubber sealant) $ 4.39$ 4.39

TOTAL: TOTAL: $40.08$40.08

Future WorkFuture Work

Present to clientPresent to client Increase accuracy of designIncrease accuracy of design

– Alter inner cavity by replicating CT scans Alter inner cavity by replicating CT scans of normal and Chiari I patientsof normal and Chiari I patients

– Increase size of pieces for anatomical Increase size of pieces for anatomical correctnesscorrectness

– Increase number of pressure points Increase number of pressure points measuredmeasured

Assist in data collectionAssist in data collection– Monitor pressure changesMonitor pressure changes

ReferencesReferences Arnett, B. 2002. Arnold-Chiari malformation. Arnett, B. 2002. Arnold-Chiari malformation. History of Neurology: History of Neurology:

reprinted 2003reprinted 2003.. Automation Creations, Inc. 2004. “Material Property Data.” Accessed 12 Automation Creations, Inc. 2004. “Material Property Data.” Accessed 12

March 2004. URL: March 2004. URL: www.matweb.comwww.matweb.com Chang, H.S. and Nakagawa, H. 2003. Hypothesis on the pathophysiology Chang, H.S. and Nakagawa, H. 2003. Hypothesis on the pathophysiology

of syringomyelia based on simulation of cerebrospinal fluid dynamics.of syringomyelia based on simulation of cerebrospinal fluid dynamics. Journal of Neurology, Neurosurgery and Psychiatry Journal of Neurology, Neurosurgery and Psychiatry 74: 344.74: 344.

Haughton, V. Personal Interview. Jaunary 6, 2004.Haughton, V. Personal Interview. Jaunary 6, 2004. Haughton, V. Personal Interview. February 13, 2004. Haughton, V. Personal Interview. February 13, 2004. Haughton, V. Personal Interview. April 14, 2004.Haughton, V. Personal Interview. April 14, 2004. Haughton, V. Personal Interview. April 16, 2004. Haughton, V. Personal Interview. April 16, 2004. Loth, F., Yardimci, M.A., and Alperin, N. 2001. Hydrodynamic modeling of Loth, F., Yardimci, M.A., and Alperin, N. 2001. Hydrodynamic modeling of

cerebrospinal fluid motion within the spinal cavity. cerebrospinal fluid motion within the spinal cavity. Journal of Journal of Biomechanical EngineeringBiomechanical Engineering 123. 123.

Mueller, D. “The adult chiari I malformation.” Mueller, D. “The adult chiari I malformation.” The Chiari ClinicThe Chiari Clinic. Accessed: . Accessed: 01 March, 2004. URL: 01 March, 2004. URL: http://tribble.missouri.edu/ns/chiari/aboutchiarimalformation.htmhttp://tribble.missouri.edu/ns/chiari/aboutchiarimalformation.htm

Hoffman, R.D. 2003. Piston Pump. The Internet Glossary of Pumps. Hoffman, R.D. 2003. Piston Pump. The Internet Glossary of Pumps. Accessed: 15 February 2004. URL: Accessed: 15 February 2004. URL: http://www.animatedsoftware.com/pumpglos/pistpump.htmhttp://www.animatedsoftware.com/pumpglos/pistpump.htm

The Ventricular System and CSF. Accessed 08 March 2004. URL: The Ventricular System and CSF. Accessed 08 March 2004. URL: http://faculty.washington.edu/chudler/vent.htmlhttp://faculty.washington.edu/chudler/vent.html