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

为了阐明正常压力性脑积水(NPH)的颅内动力学特征，我们利用相位对比(PC)电影磁共振成像技术计算了导水管内驱动血管搏动和脑脊液(CSF)流动的频谱相转移函数(PTF)。在与导水管长轴中点垂直的平面上，用心脏触发PC电影MRI测量了脑脊液流量和血流波形。以脑内动脉流入和静脉流出时相的差值为输入函数(驱动血管搏动)，以导水管内脑脊液流量为输出函数，由这两个函数计算出与动力学特性相关的PTF。测定蛛网膜下腔出血后出血患者(SAH-NPH)、SAH-NPH分流术后组和健康志愿者(对照组)的PTF。在静脉注射乙酰唑胺5分钟后测定S的PTF(F)(增加脑血容量)。SAH-NPH组一次谐波的PTF明显大于对照组，分流术后组PTF较SAH-NPH组更接近对照组。在任何频率注射乙酰唑胺前后，PTF均无显著差异；与血流动力学无关。PTFPTF分析与PC电影MRI呈正相关，这使得无创性地获得NPH病例的颅内动力学特性信息成为可能。

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.