Authors Timothy Eng Team Leader Mary Lim BWIG Lauren Hensley BSAC April Zehm Communicator

Client & Advisor Dr. Victor Haughton, M.D. UW Department of Radiology UW Medical School Professor Justin Williams Department of Biomedical Engineering

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

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

Background Information Chiari I Malformation Chiari I Malformation –Brainstem and cerebellar tonsils (brain tissue) lower into cranial vault  Obstructs CSF flow  Causes increased PRESSURE on brain and in spinal canal –Symptoms: headaches, pain, dysphagia, numbness, motory and sensory inhibition, loss of consciousness –Treatment: surgery (physical enlargement)

Anatomy of Chiari I

Bernoulli’s Law P + ½ ρv 2 = constant P + ½ ρv 2 = constant Pressure is proportional to diameter of tube Pressure is proportional to diameter of tube Velocity is inversely proportional to diameter of tube Velocity is inversely proportional to diameter of tube

Design Constraints Must replicate anatomical size of human spinal canal and cranial vault Must replicate anatomical size of human spinal canal and cranial vault Requires oscillatory flow that mimics actual CSF flow Requires oscillatory flow that mimics actual CSF flow Pressure measured accurately along various points Pressure measured accurately along various points Ability to interchange pieces Ability to interchange pieces Must attach to provided pump Must attach to provided pump MRI compatible MRI compatible

Chosen Design Two working modules Two working modules –Replicate CT scans of normal patients and Chiari I malformation –Oscillatory flow induced by piston pump –Interchangeable, polycarbonate pieces –Pressure quantifiable via transducer

Problems Encountered Budget Constraints Budget Constraints –Expected cost exceeded $200 limit Time Constraints Time Constraints –3-4 hours/block; 20 blocks needed Available Equipment Constraints Available Equipment Constraints –Shop machinery inadequate for small scale design –Accuracy and precision would be compromised

Design Modifications CT scan images replaced with range of cylinders CT scan images replaced with range of cylinders –Form inner funnel-like shape in module Pressure measured in same fashion Pressure measured in same fashion Maintains interchangeability of pieces Maintains interchangeability of pieces Meets design specifications; approved by client as acceptable (but temporary) solution to problem Meets design specifications; approved by client as acceptable (but temporary) solution to problem

Prototype Construction Acquired materials Acquired materials –Polycarbonate sheet –Non-magnetic stainless steel screws –Adaptors for pump –Flexible tubing Piecewise Construction Piecewise Construction Testing for functionality Testing for functionality

Schematic of Prototype Side view schematic

Functional Prototype Polycarbonate Polycarbonate Inexpensive Inexpensive Measures pressure changes at various points within module Measures pressure changes at various points within module Easy to assemble and interchange pieces Easy to assemble and interchange pieces Simple design can be modified to utilize CT scans/improve accuracy of model Simple design can be modified to utilize CT scans/improve accuracy of model

Piston Pump Will be used by client Will be used by client Generates oscillatory flow Generates oscillatory flow Electronically controlled Electronically controlled Compatible with multiple modules Compatible with multiple modules

Placement of the Module Module connected to pump via plastic adaptors Module connected to pump via plastic adaptors Fluid flows through module in oscillatory manner (sine function can be generated) Fluid flows through module in oscillatory manner (sine function can be generated)

Cost Analysis 3/8” 12”x24” polycarbonate sheet$ /8” 12”x24” polycarbonate sheet$ ” non-magnetic stainless steel 6” non-magnetic stainless steel screwswith 1/4” diameter (4) screwswith 1/4” diameter (4) + wing nuts (4)$ /4” flexible plastic tubing (3 ft)$ /4” flexible plastic tubing (3 ft)$ 0.87 Plastic Adaptors$ 0.00 Plastic Adaptors$ 0.00 Goop Marine(rubber sealant)$ 4.39 Goop Marine(rubber sealant)$ 4.39 TOTAL: $40.08

Future Work Present to client Present to client Increase accuracy of design Increase accuracy of design –Alter inner cavity by replicating CT scans of normal and Chiari I patients –Increase size of pieces for anatomical correctness –Increase number of pressure points measured Assist in data collection Assist in data collection –Monitor pressure changes

References Arnett, B Arnold-Chiari malformation. History of Neurology: reprinted Arnett, B Arnold-Chiari malformation. History of Neurology: reprinted Automation Creations, Inc “Material Property Data.” Accessed 12 March URL: Automation Creations, Inc “Material Property Data.” Accessed 12 March URL: Chang, H.S. and Nakagawa, H Hypothesis on the pathophysiology of syringomyelia based on simulation of cerebrospinal fluid dynamics. Journal of Neurology, Neurosurgery and Psychiatry 74: 344. Chang, H.S. and Nakagawa, H Hypothesis on the pathophysiology of syringomyelia based on simulation of cerebrospinal fluid dynamics. Journal of Neurology, Neurosurgery and Psychiatry 74: 344. Haughton, V. Personal Interview. Jaunary 6, Haughton, V. Personal Interview. Jaunary 6, Haughton, V. Personal Interview. February 13, Haughton, V. Personal Interview. February 13, Haughton, V. Personal Interview. April 14, Haughton, V. Personal Interview. April 14, Haughton, V. Personal Interview. April 16, Haughton, V. Personal Interview. April 16, Loth, F., Yardimci, M.A., and Alperin, N Hydrodynamic modeling of cerebrospinal fluid motion within the spinal cavity. Journal of Biomechanical Engineering 123. Loth, F., Yardimci, M.A., and Alperin, N Hydrodynamic modeling of cerebrospinal fluid motion within the spinal cavity. Journal of Biomechanical Engineering 123. Mueller, D. “The adult chiari I malformation.” The Chiari Clinic. Accessed: 01 March, URL: Mueller, D. “The adult chiari I malformation.” The Chiari Clinic. Accessed: 01 March, URL: Hoffman, R.D Piston Pump. The Internet Glossary of Pumps. Accessed: 15 February URL: Hoffman, R.D Piston Pump. The Internet Glossary of Pumps. Accessed: 15 February URL: The Ventricular System and CSF. Accessed 08 March URL: The Ventricular System and CSF. Accessed 08 March URL: