INTRACRANIAL PRESSURE MONITOR Dan Frost Rebecca Koszalinski Justin Lundell Michael Socie Advisor: Professor Naomi Chesler, UW-Madison Client: Joshua Medow, M.D., UW-Hospital

Background Why is this technology needed? –Shunt failure 17% –Hydrocephalus – ventricle blocked –Symptoms not specific for diagnosis –Children don’t report symptoms –Excess CT scan testing dangerous

Current Technology Existing technology –CT scan –Ultrasound –Exploratory surgery –Shunt taps What this technology lacks –Patient home testing –Multiple use monitoring –Absence of radiation –Accessibility to patient –Ease of testing for children –Cost effective testing

Current Devices Radionics Telesensor for intracranial pressure Medtronic Hemodynamic Monitor for symptomatic heart failure Duncan Graham-Rowe batteryless implant for blood pressure

Problem Statement ICP monitor should: –Measure pressure of intracranial fluid –Produce accurate recordings –Have a low drift rate –Be small, convenient to patient –Be MRI compatible

Design Constraints Small, implantable, durable Bio and MRI compatible Low power High precision (1 mmHg error) Low drift rate (<1% annually) Send output for reading

Materials & Budget Polypropylene sheets Aluminum rods MicroEpsilon EddyNCDT 2mm range pressure sensor $1.60 * 5 = $8.00 $3.00 * 4 = $12.00 $1500 analog only $3600 with digital display Purchase pending

Construction Thermoforming –Cheap –Simple process –Low repeatability –Prototype applicable Injection molding –$10,000+ for a mold –Lab equipment needed –Highly repeatable –Good for mass production

Final Prototype Aluminum Rod Membrane Polypropylene Cap 22 mm 18mm 4.76 mm 3 mm 20 mm 8 mm

Testing Liquid above zero line corresponds to positive pressure on prototype Sensor Tip Prototype P = 0 1mL = 0.6 mmHg mmHg Normal mmHg Fatal if prolonged 40+ mmHg Coma and death

Results 10mL = 6mmHg

Future Work Further testing for: –Pressure range –Accuracy –Durability If testing is successful: –Purchase sensor –Patents and FDA approval –Mass production via injection molding

References & Acknowledgements References: 1.“Measuring Strain Gauges” National Instruments “Wheatstone Bridge Background” dwiarda Dr. Josh Medow, Neurosurgery, UW Hospital 4.Collins, C.C. (1970) Biomedical transensors: A review. J. Biomed. Syst., 1: Webster, John. (1978) Medical Instrumentation: Application and Design 1st Edition 6.Budgett D., et al. (2007) Novel technology for the provision of power to implantable physiological devices. J Appl Physiol 102: Konigsberg, E., and R. H. Russel., (1968) A bettery operated miniature pressure transducer amplifier system. Biomedical Sciences Instrumentation, New York: Plenum, Vol. IV. Acknowledgements: Naomi Chesler, Josh Medow, John Webster, Tim Fauser, Adam Kramschuster