NONINVASIVE MEASUREMENT OF INTRACRANIAL PRESSURE

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Elevated intracranial pressure (ICP) remains a critical problem in management of patients with neurological problems and is the most common cause of death in these patients. Elevated ICP can be managed and treated if detected at an early stage. Therefore, measurement of ICP is important for diagnosis and treatment decisions. At present, only invasive techniques are available for measurement of absolute ICP. These techniques require physical penetration of the central nervous system (CNS). The objective of this project is to develop the technology for non-invasive measurement of ICP. The non-invasive measurement of ICP would be at a lower cost and without risk or pain to the patient. Hence, this important clinical parameter would be measured more often and may significantly improve the diagnosis and treatment decisions for patients with neurological problems. The proposed project integrates knowledge from human neuro-physiology, principles of fluid dynamics, and dynamic MRI techniques in developing a novel method to non-invasively measure ICP. The technique is novel as it makes use of the change in intracranial volume (ICV) and ICP that occur naturally during each cardiac cycle rather than altering the state of the CNS by external intervention. Since the ratio of intracranial pressure and volume changes is a known function of ICP, a measurement of the ratio of these changes provides a measure of ICP. The changes in ICP and ICV during the cardiac cycle will be computed from MRI measurements of cerebrospinal fluid (CSF) and blood volumetric flow rates. The ICV change will be obtained from the net volumetric flow of blood and CSF into the cranium. The ICP changes will be estimated from pulsatile CSF pressure gradient. The CSF pressure gradient will be computed from dynamic MRI CSF flow measurement in the cervical spine. In preliminary work on a baboon, the change in ICP (i.e., the peak-to-peak pulsatile ICP) was linearly correlated with the peak-to-peak of the pulsatile CSF pressure gradient. The objective of this project is to demonstrate the feasibility of the proposed technology. The specific aims are: 1. Optimize the MRI protocol and data analysis for reproducibility and accuracy of ICV change and pressure gradient measurements. 2. Evaluate the accuracy of the estimated ICP changes from CSF pressure gradient measurements using animal model and computational fluid dynamic simulations. 3. Evaluate accuracy of the non-invasive technique by comparison with invasive measurements on an animal model of normal and elevated ICP.