Feasibility of Diffusion-weighted Imaging (DWI) for Assessing Cerebrospinal Fluid Dynamics: DWI-fluidography in the Brains of Healthy Subjects

Abstract

Purpose: The present study aimed to investigate whether diffusion-weighted imaging (DWI) can qualify and quantify cerebrospinal fluid (CSF) dynamics in the brains of healthy subjects. For this purpose, we developed new DWI-based fluidography and compared the CSF dynamics seen on the fluidography with two apparent diffusion coefficients obtained with different DWI signal models at anatomical spaces filled by CSF.

Methods: DWI with multiple b values was performed for 10 subjects using a 7T MRI scanner. DWI-fluidography based on the DWI signal variations in different motion probing gradient directions was developed for visualizing the CSF dynamics voxel-by-voxel. DWI signals were measured using an ROI in the representative CSF-filled anatomical spaces in the brain. For the multiple DWI signals, the mono-exponential and kurtosis models were fitted and two kinds of apparent diffusion coefficients (ADC_C and ADC_K) were estimated in each space using the Gaussian and non-Gaussian diffusion models, respectively.

Results: DWI-fluidography could qualitatively represent the features of CSF dynamics in each anatomical space. ADCs indicated that the motions at the foramen of Monro, the cistern of the velum interpositum, the quadrigeminal cistern, the Sylvian cisterns, and the fourth ventricle were more drastic than those at the subarachnoid space and anterior horns of the lateral ventricle. Those results seen in ADCs were identical to the findings on DWI-fluidography.

Conclusion: DWI-fluidography based on the features of DWI signals could show differences of CSF dynamics among anatomical spaces.

Keywords: cerebrospinal fluid; diffusion-weighted imaging; magnetic resonance imaging; neurofluid.

Fig. 1

Images at the same section in a representative case (29-year-old man). Anatomical T1-weighted images (a and f), images acquired using diffusion-weighted imaging with four different b values (b and g, 80 s/mm²; c and h, 160 s/mm²; d and i, 320 s/mm²; and e and j, 640 s/mm²), F map (k: unit, the ratio to the largest value among all variations), and color-coded flow anisotropy maps (l–o: left and right, red; anterior and posterior, green; superior and inferior, blue).

Fig. 2

Corresponding sections of the anatomical T1-weighted image (left column, a, c, e, and g) and non-diffusion-weighted imaging (right column, b, d, f, and h) for locating each ROI to measure the signals from the cerebrospinal fluid (red circles on b, d, f, and h; subarachnoid space on b; anterior horn and trigone of the lateral ventricles, and foramen of Monro on d; Sylvian cistern and quadrigeminal cistern on f; and fourth ventricle on h).

Fig. 3

Representative signal attenuations measured in typical ROI at four anatomical spaces and each fitting curve defined with non-Gaussian model function. aLV, anterior horn; FM, foramen of Monro; SAS, subarachnoid space; SC, Sylvian cistern.

Fig. 4

A comparison graph among all anatomical cavities for ADCs estimated using the Gaussian and non-Gaussian diffusion models. aLV and tLV, anterior horn and trigone of the lateral ventricles; CVI, cistern of velum interpositum; FM, foramen of Monro; FV, fourth ventricle; QC, quadrigeminal cistern; SAS, subarachnoid space; SC, Sylvian cistern. † Significantly lower than those at FM, CVI, QC, SC, and FV (P < 0.05). ‡ Significantly lower than those at FM (P < 0.05). * Significantly lower than those at tLV, FM, CVI, QC, SC, and FV (P < 0.05). ** Significantly higher than those at the other spaces (P < 0.05). § Significantly higher than those at the tLV, CVI, and QC (P < 0.05).