Intracranial pressure (ICP) is a critical monitoring parameter for head trauma patients and post-operative neurosurgical patients. Intracranial hypertension (IC-HTN), a condition that can arise from traumatically induced mass effect, blood collections, stroke, or cerebral edema after surgery, requires immediate action if brain injury following compromised cerebral blood flow is to be avoided. Presently, the “gold standard” for monitoring ICP is a transducer-coupled fluid-filled intraventricular catheter (IVC) placed into the cerebral ventricles or a fiber optic intraparenchymal monitor (ICP “bolt”) inserted via a burr hole in the skull. The invasive nature of ICP monitoring is the source of its disadvantages and complications (e.g., infection and hemorrhage).
The FUS lab has been investigating a method for non-invasively monitoring ICP by taking advantage of the sensitivity of guided acoustic waves to fluid pressure. By actuating and detecting the propagation of plate-mode waves across the convexity of ex vivo human skulls, our experiments and analyses have revealed a measurable change in the dispersion characteristics of the acoustic signal in response to a change in ICP. The measurement does not have a predominant reliance on physical changes in the skull itself, but is specifically sensitive to the pressure of the adjacent fluid. The method of plate-mode analysis has been established and well-studied by geophysicists (i.e., seismic geodynamics) and sensor designers (i.e., surface acoustic wave sensors), so a theoretical and mathematical foundation has already been established for the translation of this technology into clinical application.