Assessment of cerebrospinal fluid flow patterns using the time-spatial labeling inversion pulse technique with 3T MRI: early clinical experiences

Abstract

CSF imaging using the time-spatial labeling inversion pulse (time-SLIP) technique at 3T magnetic resonance imaging (MRI) was performed to assess cerebrospinal fluid (CSF) dynamics. The study population comprised 15 healthy volunteers and five patients with MR findings showing expansive dilation of the third and lateral ventricles suggesting aqueductal stenosis (AS). Signal intensity changes were evaluated in the tag-labeled CSF, untagged brain parenchyma, and untagged CSF of healthy volunteers by changing of black-blood time-inversion pulse (BBTI). CSF flow from the aqueduct to the third ventricle, the aqueduct to the fourth ventricle, and the foramen of Monro to the lateral ventricle was clearly rendered in all healthy volunteers with suitable BBTI. The travel distance of CSF flow as demonstrated by the time-SLIP technique was compared with the distance between the aqueduct and the fourth ventricle. The distance between the foramen of Monro and the lateral ventricle was used to calculate the CSF flow/distance ratio (CD ratio). The CD ratio at each level was significantly reduced in patients suspected to have AS compared to healthy volunteers. CSF flow was not identified at the aqueductal level in most of the patients. Two patients underwent time-SLIP assessments before and after endoscopic third ventriculostomies (ETVs). CSF flow at the ETV site was confirmed in each patient. With the time-SLIP technique, CSF imaging is sensitive enough to detect kinetic changes in CSF flow due to AS and ETV.

Keywords: MRI; cerebrospinal fluid; hydrocephalus.

Figure 1

Selective inversion-recovery (IR) pulse (tag) set to observe cerebrospinal fluid (CSF) flow using the time-spatial labeling inversion pulse (time-SLIP) technique. (A) To observe CSF flow from the aqueduct to the third ventricle, the superior margin of the tag is set at the border zone between the aqueduct and the third ventricle (→). (B) To observe CSF flow from the aqueduct to the fourth ventricle, the inferior margin of the tag is set at the border zone between the aqueduct and the fourth ventricle (→). (C) To observe CSF flow from the third ventricle to the lateral ventricle, the superior margin of the tag is set at the level of the foramen of Monro (→). (D) To observe CSF flow from the third ventricle to the prepontine cistern through the ventriculostomy site after endoscopic third ventriculostomy (ETV), the inferior margin of the tag is set at the ventriculostomy site (→). (E) To observe CSF flow from the prepontine cistern to the third ventricle through the ventriculostomy site after ETV, the superior margin of the tag is aligned with the ventriculostomy site (→).

Figure 2

The ROIs are set to detect changes in signal intensity according to the black-blood time-inversion pulse (BBTI). CSF labeled with a selective IR pulse (A), untagged CSF (B), and untagged brain parenchyma (C).

Figure 3

CSF flow as imaged using the time-SLIP technique is evaluated by calculating the following: 1) the CSF flow/distance (CD) ratio of the distance between the lower portion of the aqueduct and the obex of the fourth ventricle versus the maximum travel distance of the rendered CSF flow. 2) The CD ratio of the height from the foramen of Monro to the superior wall of the lateral ventricle versus the maximum travel distance of the rendered CSF flow.

Figure 4

In the control group, ROIs are set in the labeled CSF (A), untagged CSF (B), and untagged brain parenchyma (C). Signal changes in each ROI are graphed according to the BBTI.

Figure 5

Images obtained for a 33-year-old man in the control group. CSF flow is rendered clearly using the time-SLIP technique from the aqueduct to the third ventricle (→) (A), from the aqueduct to the fourth ventricle (B), and from the third ventricle to the lateral ventricle (→) (C).

Figure 6

Images for a 24-year-old man in the hydrocephalic group. A) A membranous septum and prestenotic dilation in the aqueduct is observed on T2WI of sagittal sections (→). Images obtained using the time-SLIP technique show the following findings. Before ETV, no CSF flow from the aqueduct to the third ventricle is observed (→) (B) and CSF flow is clearly observed from the aqueduct to the fourth ventricle (→) (C). D) After ETV, CSF flow from the aqueduct to the fourth ventricle has disappeared (→). Turbulent and pulsatile CSF flow is observed from the prepontine cistern to the third ventricle (→) (E) and from the third ventricle to the prepontine cistern through the ventriculostomy site (→) (F).

Figure 7

A 7-year-old girl suspected of AS and known to have a tumor in the trigone of the right lateral ventricle. Although CSF imaging by the time-SLIP technique shows no CSF flow from the third ventricle to the lateral ventricle before ETV (→) (A), CSF flow is clearly observed after ETV (→) (B).

Figure 8

The CD ratios of the rendered CSF flow are significantly higher in the control group than in the hydrocephalic group at the level of the fourth (A) and lateral ventricles (B) (*p < 0.001).