1. Introduction

Investigations of CSF motion based on MRI have been actively performed [1–6]. CSF motion is thought to be composed of three components: cardiac-driven motion, respiratory-driven motion, and bulk flow [7, 8]. Cardiac-driven motion is primarily induced by arterial blood vessel pulsation and relates to the regulation of intracranial pressure (ICP) [2, 4, 9, 10]. A change in intrathoracic pressure caused by respiration induces the modulation of venous blood pressure, resulting in respiratory-driven motion [6, 11–14]. Bulk flow is a slow motion relating to CSF production and absorption, thus playing a role to washout wastes from the brain through the glymphatic system [7, 8, 15, 16].

Hydrocephalus is the most commonly known disease relating to the alternation of CSF dynamics through, for example, a velocity increase in the aqueduct [17–19]. Although hydrocephalus increases intracranial pressure (ICP) in some cases, normal pressure hydrocephalus (NPH), including idiopathic NPH (iNPH), does not increase ICP, and thus, it is difficult to know the exact status of the disease using invasive pressure measurement, as in a lumber puncture (LP) procedure. Even in such a case there might be abnormality in the CSF dynamics. Therefore, the investigation of the relationship between hydrocephalus and CSF motion is essential. It is also known that the development of Alzheimer's disease (AD) relates to the accumulation of amyloid beta protein and thus to the malfunction of the glymphatic system, which in turn the bulk flow [8]. Thus, the characterization of the CSF dynamics may lead to the key for clarifying the status and the symptom of the abovementioned diseases.

The asynchronous PC technique uses a rapid signal acquisition scheme, such as steady state free precession (SSFP), to obtain velocity images with the order of 217 ms per frame. When combined with the ECG and respiratory signals monitored during acquisition, this technique

Visualization and Characterization of Cerebrospinal Fluid Motion Based on Magnetic Resonance Imaging

http://dx.doi.org/10.5772/intechopen.73302

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Cardiac-gated PC velocity measurement was performed in three spatial directions at 1.5 T for 13 young, healthy volunteers (8 males and 5 females with mean SD age of 29 5); 13 elderly, healthy volunteers (4 males and 9 females with mean SD age of 72 8); and 13 patients with iNPH (2 males and 11 females with mean SD age of 75 5). Detailed imaging conditions are

In segmenting the CSF space from the T2-weighted images with relatively large voxel size

reduce the possible partial volume effect [23]. This method differentiated tissues with different signal intensities even in an identical voxel and determined the boundary between the tissues,

Four-dimensional velocity mapping (4D-VM) visualizes the cardiac-driven CSF motion in intracranial space, which is composed of cardiac-gated PC acquisition in three spatial directions. In-plane velocities were indicated as arrows, while out-plane velocities were color-

In general, a vector field is fully characterized by the divergence and curl of the velocity field based on Helmholtz's theorem [24]. The curl of the velocity field was calculated as follows to

coded. The time-resolved velocity maps or 4D-VM were superimposed on T2 images.

) [22], the spatial-based fuzzy clustering method (SFCM) was applied to

may simultaneously measure the cardiac- and respiratory-driven CSF velocities.

2.2. CSF motion visualization based on cardiac-gated PC imaging

Figure 1. Schematic diagram of cardiac-gated (a) and asynchronous (b) PC acquisitions.

shown elsewhere [10].

(approximately 1 mm<sup>3</sup>

2.3.1. Curl of the velocity field

provide the intensity of the vortex:

resulting in a reasonably segmented image.

2.3. Four-dimensional velocity mapping

This chapter presents the techniques for the visualization and characterization of CSF motion in intracranial space based on the cardiac-gated PC [20, 21] and asynchronous PC technique of MRI.
