Spectral PTF analysis using cine-MRI in normal pressure hydrocephalus

摘要

To clarify intracranial dynamical properties in normal pressure hydrocephalus (NPH), we assessed a spectral phase transfer function (PTF) calculated from the driving vascular pulsation and cerebrospinal fluid (CSF) flow in the aqueduct. Because the PTF is thought to change in accordance with the degree of pressure damping. On a vertical plane against a mid-point on the long axis of the aqueduct [1], Both CSF flow and blood flow waveforms were measured with cardiac phase contrast cine-MRI. Taking the difference in each cardiac phase between arterial inflow and venous outflow in the brain [A(t)-V(t)] as the input function (driving vascular pulsation)[2], and the CSF flow in the aqueduct as the output function [C(t)], the frequency response function [G(/)] related to the intracranial dynamical properties [2] is obtained from: G(f) = C(f)/ [A(f) - V(f)], PTF(f) = tan~(-1)/[I(f) / R(f)] where R(f) and I(f) are the real and the imaginary parts of G(f). The PTF was determined in patients (n=9) with NPH after a subarachnoid hemorrhage (SAH-NPH), in an SAH-NPH post-shunt operation group (n=4), and in healthy volunteers (control group) (n=4). The PTF(f)s were also measured 5 min after an intravenous injection of acetazolamide (increase of cerebral blood volume)[l]. The PTF was compared with the pressure volume response (PVR) as an index of the intracranial compliance.