Hemodynamically independent analysis of intracranial cerebrospinal fluid dynamics using PC cine MRI

为了阐明常压脑积水（NPH）的颅内动力学特性，我们使用相位对比（PC）电影MRI评估了从驱动血管脉动和脑脊液（CSF）流计算的谱相传递函数（PTF）。在与导水管长轴中点相对的垂直平面上，用心脏触发的PC机MRI测量脑脊液流量和血流波形。以脑动脉流入与静脉流出各心相差作为输入函数（驱动血管脉动），以输导管内CSF流量作为输出函数，从两个函数中计算与动力特性相关的PTF。测定蛛网膜下腔出血（SAH-NPH）后NPH患者、SAH-NPH分流术后组和健康志愿者（对照组）的PTF。静脉注射乙酰唑胺5 min后测定PTF(f)s（脑血容量增加）。将PTF与压力容积反应（PVR）作为颅内顺应性的指标进行比较。SAH-NPH组第1次谐波PTF明显大于对照组，分流术后SAH-NPH组PTF比SAH-NPH组更接近对照组。注射乙酰唑胺前后PTF在任何频率下均无显著差异；独立于血流动力学。PTFPTF分析与PC电影MRI呈正相关，可以获得NPH病例颅内动力学特性的无创信息。

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 using phase contrast (PC) cine MRI.On a vertical plane against a mid-point on the long axis of the aqueduct, both CSF flow and blood flow waveforms were measured with cardiac triggered PC cine MRI. Taking the difference in each cardiac phase between arterial inflow and venous outflow in the brain as the input function (driving vascular pulsation), and the CSF flow in the aqueduct as the output function, the PTF related to the dynamical properties was calculated from both functions. The PTF was determined in patients with NPH after a subarachnoid hemorrhage (SAH-NPH), in an SAH-NPH post-shunt operation group, and in healthy volunteers (control group). The PTF(f)s were also measured 5 min after an intravenous injection of acetazolamide (increase of cerebral blood volume). The PTF was compared with the pressure volume response (PVR) as an index of the intracranial compliance.The PTF of the 1st harmonic in the SAH-NPH group was significantly larger than in the control group, and the PTF in the SAH-NPH post-shunt operation group tends to be closer to that in the control group than the SAH-NPH group. There was no significant difference in PTF before and after acetazolamide injection at any frequency ; independent of hemodynamics. A positive correlation was noted between the PTFPTF analysis with PC cine MRI makes it possible to obtain information noninvasively on intracranial dynamical properties in cases of NPH.