Date of Award

Summer 2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biomedical Engineering - (Ph.D.)

Department

Biomedical Engineering

First Advisor

William Corson Hunter

Second Advisor

Richard A. Foulds

Third Advisor

Stanley S. Reisman

Fourth Advisor

John Tavantzis

Fifth Advisor

Sergei Adamovich

Sixth Advisor

Max Roman

Abstract

This study provides a novel explanation for the CerebrQ-Spinal Fluid (CSF) flow pattern observed in phase contrast cine-MRJ studies. CSF dynamics has been traditionally explained as a bulk flow from the site of production to the site of absorption. Studies done with phase contrast cine-MRI show a more complex CSF movement, that is not explainable by the bulk flow paradigm. This study describes a mechanism explaining how the energy delivered by the heart in each cycle is responsible not only for the blood flow, but also for the CSF circulation. This mechanism is based on a cyclic variation of brain compliance, dependent on the blood volume inside the brain vessels. As the cardiac cycle changes the blood volume inside the vessels, it also conditions a compliance cycle of the brain tissue.

For better comprehension of the mechanism, a conceptual model, mathematical model and computer model are described. To capture the essence of CSF dynamics a three compartmental model is created representing: the ventricular system, the intracranial subarachnoideal space, and the spinal subarachnoideal space. The implemented driving function represents the blood volume variation with time produced by the cardiac cycle. In turn it detennines cyclic changes in brain parenchyma compliance. Brain parenchyma compliance changes as a function of the blood volume inside the brain vessels; therefore, during systole the compliance diminishes, during diastole compliance increases. As brain tissue compliance changes the CSF volume inside each compartment is redistributed. Cyclic compliance variation of brain tissue creates a pulsatile CSF flow. The CSF dynamics model is also used for the analysis of altered CSF dynamics; Normal Pressure Hydrocephalus and Idiopathic Intracranial Hypertension are explained as a consequence of altered compliance of the brain tissue.

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