Abstract
The aim of this study is to evaluate diurnal variation in knee cartilage 3 Tesla magnetic
resonance imaging (MRI) T2 mapping relaxation times, as well as activity- and body
mass index (BMI)-dependent variability, using quantitative analysis of T2 values from
segmented regions of the weight-bearing articular surfaces of the medial and lateral
femoral condyles and tibial plateaus. Ten healthy volunteers' daily activity (steps)
were tracked with Fitbit pedometers. Sagittal MRI T2 maps were obtained in the morning
and afternoon on days 2 and 3. Mean T2 values were analyzed for variation related
to the number of steps taken (activity), time of day (diurnal variation), and BMI
using mixed effect model. Significant (albeit small) differences in the medial femoral
and medial tibial cartilage regions were identified between morning and afternoon
scans (diurnal variation). Daily activity did not result in significant changes and
increasing BMI only demonstrated a slight increase in T2 values for the lateral tibial
plateau. These findings suggest that it may be necessary to control diurnal variation
when using quantitative MRI T2 mapping to assess articular cartilage longitudinally
in healthy participants. Further investigation is needed to confirm these findings
and determine if they also apply to symptomatic patients.
Keywords
knee cartilage - quantitative T2 mapping - diurnal variation - Fitbit - activity tracking
