D* from diffusion MRI reveals a correspondence between ventricular cerebrospinal fluid volume and flow in the ischemic rodent model

Abstract

Quantitative measurement of cerebrospinal fluid (CSF) flow and volume and longitudinal monitoring of CSF dynamics provide insights into the compensatory characteristics of post-stroke CSF. In this study, we compared the MRI pseudo-diffusion index ( D*) of live and sacrificed rat brains to confirm the effect of ventricular CSF flow on diffusion signals. We observed the relationship between the CSF peak velocities and D* through Monte Carlo (MC) simulations to further understand the source of D* contrast. We also determined the dominant CSF flow using D* in three directions. Finally, we investigated the dynamic evolutions of ventricular CSF flow and volume in a stroke rat model ( n = 8) from preoperative to up to 45 days after surgery and determined the correlation between ventricular CSF volume and flow. MC simulations showed a strong positive correlation between the CSF peak velocity and D* ( r = 0.99). The dominant CSF flow variations in the 3D ventricle could be measured using the maximum D* map. A longitudinal positive correlation between ventricular CSF volume and D* was observed in the lateral ( r = 0.74) and ventral-third ( r = 0.81) ventricles, respectively. The directional D* measurements provide quantitative CSF volume and flow information, which would provide useful insights into ischemic stroke with diffusion MRI.

Changes in cardiac-driven perivascular fluid movement around the MCA in a pharmacological model of acute hypertension detected with non-invasive MRI

“…Nonetheless, recent studies have further explored the source of D* contrast in the CSF and shown a strong correlation between D* from diffusion-weighted signals and CSF peak velocity using Monte Carlo simulations. 11 Therefore measurements of D* may serve as a quantitative marker of fluid movement in the PVS and have the potential to be a useful non-invasive biomarker for derangement of PV function linked to pathological states of the brain.…”

Transient ischemic stroke triggers sustained damage of the choroid plexus blood-CSF barrier

“…In disease conditions, activated SPAK has an important role in converting stress and cytokine inflammatory signaling, including TLR4 and NF-κB dependent activation, into NKCC1-mediated hyper-or pathological secretion of CSF (Robert et al, 2023). Other research in the field has also linked changes to these protein complexes to ChP CSF production dysregulation (Podvin et al, 2011;Jang et al, 2022). Further studies will be needed to investigate impact of increased phosphorylation states of SPAK and NKCC1 on ChP CSF regulation in ischemic stroke brains.…”

Clinical magnetic resonance imaging evaluation of glymphatic function

“…Some studies have correlated the diffusion coefficient measured by low b-value DWI to the velocity of the spins bulk flow. 71,[100][101][102][103][104][105][106][107][108][109][110] A low b-value diffusion gradient (5-150 s/mm 2 ) can be used to assess bulk flow velocities, 71,100,111 perfusion imaging, 112 and functional MRI. 101 Apparent diffusion coefficient (ADC) measurements using low b-values (short diffusion time) show restricted diffusion of CSF in choroid plexus cysts.…”

“…Additionally, it was demonstrated that the ADC may be used to evaluate both the pathological condition of the brain and the flow of CSF. 106 The phase shift in MRI diffusion-weighted images was used to measure the CSF flow velocity in the optic nerve in patients with normal tension glaucoma 107 and in patients with idiopathic intracranial hypertension (IIH). 108 In both patient groups, CSF flow velocity was lower than that of the healthy controls.…”

“…Some studies have correlated the diffusion coefficient measured by low b‐value DWI to the velocity of the spins bulk flow 71,100–110 . A low b‐value diffusion gradient (5–150 s/mm 2 ) can be used to assess bulk flow velocities, 71,100,111 perfusion imaging, 112 and functional MRI 101 .…”