Problem: currently there is no clinically accepted method to track the ventricular volume

1. Normal Brain Hydrocephalic Brain A Novel Approach for Volume Measurement of CSF in the BrainBioengineering DepartmentSukraaj Basati, Olga D. Escanilla, Owais Iqbal, Poonam PatelAdvisor: Dr. Andreas Linninger MOTIVATION PROPOSED SOLUTION • Malfunction of intracranial dynamics of the brain leads to • enlarged ventricles due to inadequate absorption of cerebrospinal fluid (CSF) • neural damage and can be fatal = Hydrocephalus: • Current Treatment • Shunt: most common procedure • based on static pressure • often malfunctions and is expensive • failure rate of shunt system • 25-40% (1 yr post-implantation) • Problem: • currently there is no clinically accepted method to track the ventricular volume in hydrocephalic patients • Proposed Solution: • Develop a prototypical ventricular volume sensor • Product Requirement: • measure voltage drop by standard 4-point probe • reliable voltage-volume measurements • biocompatible and easy to calibrate Our team fabricated several sensor prototypes and investigated their reproducibility, frequency and position dependency. Principle Sensor Prototypes EXPERIMENTS / RESULTS Volume vs Voltage (5 Trials) Reproducibility of Measurements: Wire Material: Stainless Steel Purpose: Find most sensitive material Purpose: Show consistency of voltage-volume measurements • Result:↑ volume = ↓voltage • cost vs biocompatibility Result: As volume accumulates, voltage drop is observed, with standard deviation of 7-10% within 30mL of volume addition Exp. Setting Position Dependency: • Parallel: smaller voltage range voltage drop observed for limited volume range only Pt-Ir Frequency Dependency: • Optimal frequency for largest voltage-volume gain: 135 kHz Parallel Average Voltage vs Volume Perpendicular Frequency vs Voltage • Perpendicular: • “neater data” • gives wider • range of volume SS: 90-150 kHz Pt-Ir: 80-175 kHz ANALYSIS AND CONCLUSIONS • Sensor measures relative volume not absolute volume so it requires calibration • Although both Stainless Steel wire and Pt-Ir wire electrodes gave reliable volume measurements, we recommend Stainless Steel at this point of investigation due to cost • Based on our preliminary study, the sensor is reliable only between volume change of 1-30mL, however, this is adequate for CSF measurement in monitoring hydrocephalus • Sensor position needs to be consistent to minimize voltage fluctuations • with center placement yields maximum voltage drop measurements • for a higher range of volume change measurement, perpendicular alignment • of the sensor to the axis of volume increase is recommended • Our research found the proposed sensors to be adequate for monitoring hydrocephalus • Specification of Device • input signal: • ~100 µA sin (135 kHz) • desired range of use: • 1-30 mL • average sensitivity: • 0.3 mV/mL SS: sensitivity = 0.02 - 0.04 mV / mL • calibration curve: -.021x + 21.40 • Pt – Ir: sensitivity of 0.2 - 0.3 mV / mL • calibration curve = -0.314x + 15.57 Sensor Dimensions Balloon Test Setting FUTURE WORK Acknowledgements • Feedback system • Test in hydraulic brain model, then in animals • Material and dimension modification (suggest more biocompatible material and fabrication process) • We thank Dr. Linninger, Dr. Rousche, Dr. Schneeweis, Dr. Penn (UC) and Mr. Srinivas Kondapalli for their critical assistance and materials