Noninvasive Measurements of Intracranial Pressure, Tissue Compliance, Susceptibility and Temperature Using Magnetic Resonance Imaging

目的：测量颅内压、组织顺应性和组织温度等物理参数对脑肿瘤和脑积水等疾病的诊断和治疗具有重要意义。提出了一种基于磁共振的评估颅内压和组织顺应性的技术，该技术基于脑循环等效电路模型的逆分析，在该模型中，MR测量的流速被用作电流。针对温度成像问题，提出了一种新的温度成像方法--复数自参照法。还研究了线扫描回波平面光谱成像(LSEPSI)的应用。方法：设计了一种反分析算法，模拟了血液和脑脊液两种主要的脑循环，对电路中的元件进行了评估。逆分析的输入是由相衬速度图得到的脑脊液流量，而估计函数是估计的动脉血流量与频域测量的血流量的平方误差之和。使用模拟大脑循环的体模进行的实验和数值模拟证实，所提出的技术产生了顺应性和压力的相关指数。对25名健康志愿者(22-63岁)和9名患者(27-69岁)进行了研究，以验证所提出的方法在志愿者的顺应性和压力指数空间中进行映射和分组的可行性。结果：在由组织顺应性和颅内压指数组成的二维空间中，健康组和患者组分布在明显不同的区域，证明了所提出的方法用于对受试者的颅内生物力学特性状态进行分类的可行性和可行性。

Purpose : Measurements of physical parameters such as intracranical pressure, tissue compliance and tissue temperature are important for diagnosis and management of deceases such as brain tumor and hydrocephalus. A magnetic-resonance-based technique to evaluate intracranial pressure and tissue compliance based on an inverse analysis of a brain-circulation-equivalent electrical circuit model, in which MR-measured flow rates were used as currents, was proposed. For temperature imaging, a new method named "Complex, Self-reference Method" was proposed. Application of the Line Scan Echo Planar Spectroscopic Imaging (LSEPSI) was also examined. In the following, the results of the noninvasive measurement of intracranial pressure and tissue compliance are described.Methods : An inverse analysis algorism to evaluate elements in an electrical circuit, which modeled two major brain circulations, blood and cerebrospinal fluid (CSF) flows, was devised. The input for the inverse analysis was the CSF flow rate obtained by phase-contrast velocity map, whereas the estimation function was the sum of the square error of the estimated arterial blood flow rate from the measured rate in the frequency domain. Experiments using a brain-circulation-mimicking phantom followed by numerical simulations confirmed that the proposed technique yielded relative indices of the compliance and pressure. Studies on 25 healthy (22-63 years old) and 9 patient (27-69 years old) volunteers were performed to examine feasibility of the proposed technique for mapping and grouping the volunteers in the compliance and pressure indices space.Results : The healthy and patient groups distributed in significantly different regions in a two-dimensional space formed by the indices of tissue compliance and intracranial pressure, demonstrating the feasibility and viability of the proposed technique for classifying the statuses of the intracranial biomechanical properties of the subjects.