Their effect on MRI-based measurements of cerebral oxygen levels with quantitative susceptibility mapping (QSM) and cerebral blood flow (CBF) is not known.


 This study investigated whether wearing a face mask leads to changes in CBF and cerebral venous oxygen saturation measured with MRI.



MRI
A 3 T, single-delay 3D gradient-and spin-echo pseudo-continuous arterial spin labeling (pCASL) scan for CBF quantification, and gradient-echo for QSM and oxygenation quantification.


 Gray matter CBF and magnetic susceptibility were assessed by masking the pCASL CBF map and the QSM map to the T1 -weighted gray matter tissue segmentation. 
pCASL
Their effect on MRI-based measurements of cerebral oxygen levels with quantitative susceptibility mapping (QSM) and cerebral blood flow (CBF) is not known.


 A 3 T, single-delay 3D gradient-and spin-echo pseudo-continuous arterial spin labeling (pCASL) scan for CBF quantification, and gradient-echo for QSM and oxygenation quantification.


 Gray matter CBF and magnetic susceptibility were assessed by masking the pCASL CBF map and the QSM map to the T1 -weighted gray matter tissue segmentation.  Venous oxygenation was determined from venous segmentation of QSM maximum intensity projections.



QSM
Gray matter CBF and magnetic susceptibility were assessed by masking the pCASL CBF map and the QSM map to the T1 -weighted gray matter tissue segmentation. 
T1-weighted
The Effects of Wearing a 3-Ply or KN95 Face Mask on Cerebral Blood Flow and Oxygenation.BACKGROUND
 The SARS-CoV-2 virus has impacted life in many ways, one change being the use of face masks.  Their effect on MRI-based measurements of cerebral oxygen levels with quantitative susceptibility mapping (QSM) and cerebral blood flow (CBF) is not known.


 This study investigated whether wearing a face mask leads to changes in CBF and cerebral venous oxygen saturation measured with MRI.


 Repeated-measures cohort study.


 A total of 16 healthy volunteers (eight male, eight female; 22-36 years) were recruited for the 3-ply study.  Ten of the 16 participants (five male, five female; 23-36 years) took part in the KN95 study.


 FIELD STRENGTH/SEQUENCE
 A 3 T, single-delay 3D gradient-and spin-echo pseudo-continuous arterial spin labeling (pCASL) scan for CBF quantification, and gradient-echo for QSM and oxygenation quantification.


 Gray matter CBF and magnetic susceptibility were assessed by masking the pCASL CBF map and the QSM map to the T1 -weighted gray matter tissue segmentation.  Venous oxygenation was determined from venous segmentation of QSM maximum intensity projections.


 STATISTICAL TESTS
 Paired Student's t-tests and Cohen's d effect sizes were used to compare the face mask and no face mask scans for gray matter CBF, gray matter magnetic susceptibility, and cerebral venous oxygen saturation.  Standard t-tests were used to assess whether the order of scanning with and without a mask had any impact.  A statistical cut off of P < 0.05 was used.


 The 3-ply masks increased gray matter CBF from an average of 43.99 mL/(100 g*min) to 46.81 mL/(100 g*min).  There were no significant changes in gray matter magnetic susceptibility (P = 0.07), or cerebral venous oxygen saturation (P = 0.36) for the 3-ply data set.  The KN95 masks data set showed no statistically significant changes in gray matter CBF (P = 0.52) and magnetic susceptibility (P = 0.97), or cerebral venous oxygen saturation (P = 0.93).


 DATA CONCLUSION
 The changes in blood flow and oxygenation due to face masks are small.  Only CBF increased significantly due to wearing a 3-ply mask.


 EVIDENCE LEVEL
 2 TECHNICAL EFFICACY: Stage 3.
C