Dehydration affects spinal cord cross-sectional area measurement on MRI in healthy subjects.
METHODS
This was a prospective cohort observational study.


OBJECTIVE
To determine the effect of dehydration and rehydration on spinal cord cross-sectional area (CSA) measurement on magnetic resonance imaging (MRI).


METHODS
MRI Research Centre, University of British Columbia, Canada.


METHODS
Ten healthy subjects (aged 21-32 years) were scanned on a 3T MRI scanner at four time points: (1) baseline, (2) rescan after 1 h, (3) the next day after fasting for a minimum of 14 h and (4) after rehydration with 1.5 l of water over the course of 1 h. Two independent, established semi-automatic CSA measurement techniques (one based on two-dimensional (2D) edge detection, the other on three-dimensional (3D) surface fitting) were applied to a 3D T1-weighted scan of each subject at each time point, with the operator blinded to scan order. The percentage change in CSA from baseline to each subsequent time point was calculated. One-tailed paired t-tests were used to assess the significance of the changes from baseline.


RESULTS
A decrease in CSA following dehydration was detected by both measurement methods, with a mean change of -0.654% (s.d.=0.778, P<0.05) and -0.650% (s.d.=1.071, P<0.05) for the first and second methods, respectively.


CONCLUSIONS
Dehydration can confound CSA measurements on MRI. The magnitude of the effect is significant relative to short-term pathological changes that have been observed in diseases such as multiple sclerosis.
1] Department of Electrical and Computer Engineering (Biomedical Engineering Program), University of British Columbia, Vancouver, British Columbia, Canada [2] Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
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Wang
1] Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada [2] Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada.
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Tam
Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
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Mackie
1] Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada [2] Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada.
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Li
Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
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Traboulsee
D000328:Adult; D000465:Algorithms; D015331:Cohort Studies; D003681:Dehydration / Q000473:pathology*; D005215:Fasting; D005260:Female; D005440:Fluid Therapy; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D019370:Observation; D015203:Reproducibility of Results; D013116:Spinal Cord / Q000473:pathology*; D013997:Time Factors; D055815:Young Adult