Dynamic brain phantom for intracranial volume measurements.

Knowledge of intracranial ventricular volume is important for the treatment of hydrocephalus, a disease in which cerebrospinal fluid (CSF) accumulates in the brain. Current monitoring options involve MRI or pressure monitors (InSite, Medtronic). However, there are no existing methods for continuous cerebral ventricle volume measurements. In order to test a novel impedance sensor for direct ventricular volume measurements, we present a model that emulates the expansion of the lateral ventricles seen in hydrocephalus. To quantify the ventricular volume, sensor prototypes were fabricated and tested with this experimental model. Fluid was injected and withdrawn cyclically in a controlled manner and volume measurements were tracked over 8 h. Pressure measurements were also comparable to conditions seen clinically. The results from the bench-top model served to calibrate the sensor for preliminary animal experiments. A hydrocephalic rat model was used to validate a scaled-down, microfabricated prototype sensor. CSF was removed from the enlarged ventricles and a dynamic volume decrease was properly recorded. This method of testing new designs on brain phantoms prior to animal experimentation accelerates medical device design by determining sensor specifications and optimization in a rational process.