Intracranial Pressure Monitor Mike Socie – Leader Becky Koszalinski – Communicator Justin Lundell – BSAC Dan Frost – BWIG Client: Josh Medow, M.D. UW Hospital Advisor: Professor Naomi Chesler, UW-Madison

Presentation Outline Problem Statement Background Information Current Methods Design Constraints Possible Designs Future Work

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

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

Background: Current Methods Current methods include: CT scan Ultrasound Exploratory surgery Shunt taps Improved methods would allow: At home use Continuous monitoring Measurement without radiation Accessibility to patient Ease of testing for children Cost effective testing

Background: Power Sources Induction Powers device non-invasively Direct current power Wires through skin -> infection Battery Finite lifespan -> replacement surgeries

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

Design Options Resonant Coils Component Based Two transducer options Resistance based Capacitance based Two signal output options RFID tags Voltage to frequency converter

Design 1: Resonant Coils Advantages: Fewer parts than component based design Easy signal transmission Disadvantages: Undetermined drift Durable? voltage

Design 2: Component Based

Design 2: Component Options Transducers Resistance based More available High drift Not power efficient Capacitance based Less available Low drift More power efficient Signal Output RFID tags Require less parts Passive technology Voltage to freq. converter Require multiple parts Require power

Design Matrix Weighting Resonant Coils Components: Resistance & RFID Resistance & V to F converter Capacitance & RFID Capacitance & V to F converter Power Consumption 1 / 6 5 3 2 4 Durability Precision Drift 1 Ease of Construction 2 / 6 Total: 1 * 5 3.8 3.0 2.3 3.7

Future Work & Challenges Select and purchase materials Construct prototype Test drift, accuracy, and durability

References Dr. Josh Medow, Neurosurgery, UW Hospital “Measuring Strain Gauges” National Instruments. http://zone.ni.com/devzone/cda/tut/p/id/3642. “Wheatstone Bridge Background” dwiarda. http://www.dwiarda.com/scientific/bridgemore.html “Wheatstone Bridge” Wikipedia. http://en.wikipedia.org/wiki/Wheatstone_bridge. Webster, John. Medical Instrumentation: Application and Design 1st Edition. 1978.