Quantification of Arterial, Venous, and Cerebrospinal Fluid Flow Dynamics by Magnetic Resonance Imaging Under Simulated Micro-Gravity Conditions Open Access
Zahid, Arslan (Spring 2020)
Abstract
Background: Astronauts undergoing long-duration spaceflight are exposed to numerous health risks, including Spaceflight-Associated Neuro-Ocular Syndrome (SANS), a spectrum of ophthalmic changes that can result in permanent loss of visual acuity. The etiology of SANS is not well understood but is thought to involve changes in cerebrovascular flow dynamics in response to microgravity. There is a paucity of knowledge in this area; in particular, cerebrospinal fluid (CSF) flow dynamics have not been well characterized under microgravity conditions. Our study was designed to determine the effect of simulated microgravity (head-down tilt [HDT]) on cerebrovascular flow dynamics. We hypothesized that under microgravity conditions simulated by HDT, increased pressure in the intracranial space would alter intracranial CSF and venous flow dynamics by causing: 1) venous congestion reflected by increased venous cross-sectional area; and 2) a decrease in cardiac-related CSF flow oscillations.
Methods: In a prospective cohort study, we measured flow in major cerebral arteries, veins, and CSF spaces in fifteen healthy volunteers using phase contrast magnetic resonance (PCMR) before and after 15° HDT.
Results: We found a significant increase in venous cross-sectional area with HDT (p=0.005), indicating venous congestion, along with a decrease in all CSF flow parameters [systolic peak flow (p=0.009), peak-to-peak pulse amplitude (p=0.001), and stroke volume (p=0.10)]. Arterial average flow (p=0.04), systolic peak flow (p=0.04), and peak-to-peak pulse amplitude (p=0.02) all also significantly decreased.
Conclusions: These results collectively demonstrate that acute application of 15° HDT caused a reduction in CSF flow parameters (systolic peak flow and peak-to-peak pulse amplitude), coupled with an increase in venous CSA suggesting increased venous congestion with HDT.
Table of Contents
Table of Contents
Background…1-3
Materials and Methods…3-8
Results…8-14
Discussion…15-20
Figures and Tables
Figure 1. Volunteer in head-down tilt in the MR scanner…5
Figure 2. Schematic of scan protocol showing examples of cerebrospinal fluid and blood flow acquisition…5
Figure 3. Example of cerebrospinal fluid, arterial, and venous ROIs as seen on an axial view at the mid-C2 vertebral level…7
Figure 4. Representative cerebrospinal fluid flow rate vs time over a cardiac cycle, showing the definitions of flow and stroke volume parameters…10
Figure 5. Representative arterial and venous flow rates vs. time over a cardiac cycle for a single subject for the right internal carotid artery and the right internal jugular vein…11
Figure 6. Changes in venous cross sectional area from supine to head-down tilt…13
Figure 7. Changes in cerebrospinal fluid peak-to-peak pulse amplitude from supine to head-down tilt…13
Figure 8. Changes in cerebrospinal fluid systolic peak flow rate from supine to head-down tilt…14
Table 1. Change in vital signs due to HDT…9
Table 2. Changes in cerebrovascular flow dynamics from baseline (supine position) to HDT…12
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Quantification of Arterial, Venous, and Cerebrospinal Fluid Flow Dynamics by Magnetic Resonance Imaging Under Simulated Micro-Gravity Conditions () | 2020-04-27 22:48:33 -0400 |
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