Development and Validation of a Brain Phantom for Therapeutic Cooling Devices

Abstract

Tissue cooling has been proven as a viable therapy for multiple conditions and injuries and has been applied to the brain to treat epilepsy and concussions, leading to improved long-term outcomes. To facilitate the study of temperature reduction as a function of various cooling methods, a thermal brain phantom was developed and analyzed. The phantom is composed of a potassium-neutralized, superabsorbent copolymer hydrogel. The phantom was tested in a series of cooling trials using a cooling block and 37 deg water representing nondirectional blood flow ranging up to 6 gph, a physiologically representative range based on the prototype volume. Results were compared against a validated finite difference (FD) model. Two sets of parameters were used in the FD model: one set to represent the phantom itself and a second set to represent brain parenchyma. The model was then used to calculate steady-state cooling at a depth of 5 mm for all flow rates, for both the phantom and a model of the brain. This effort was undertaken to (1) validate the FD model against the phantom results and (2) evaluate how similar the thermal response of the phantom is to that of a perfused brain. The FD phantom model showed good agreement with the empirical phantom results. Furthermore, the empirical phantom agreed with the predicted brain response within 3.5% at physiological flow, suggesting a biofidelic thermal response. The phantom will be used as a platform for future studies of thermally mediated therapies applied to the cerebral cortex.