Effectively Measuring Exercise-Related Variations in T1ρ and T2 Relaxation Times of Healthy Articular Cartilage.

BACKGROUND

Determining the compositional response of articular cartilage to dynamic joint-loading using MRI may be a more sensitive assessment of cartilage status than conventional static imaging. However, distinguishing the effects of joint-loading vs. inherent measurement variability remains difficult, as the repeatability of these quantitative methods is often not assessed or reported.

PURPOSE

To assess exercise-induced changes in femoral, tibial, and patellar articular cartilage composition and compare these against measurement repeatability.

STUDY TYPE

Prospective observational study.

POPULATION

Phantom and 19 healthy participants.

FIELD STRENGTH/SEQUENCE: 3T; 3D fat-saturated spoiled gradient recalled-echo; T - and T -prepared pseudosteady-state 3D fast spin echo.

ASSESSMENT

The intrasessional repeatability of T and T relaxation mapping, with and without knee repositioning between two successive measurements, was determined in 10 knees. T and T relaxation mapping of nine knees was performed before and at multiple timepoints after a 5-minute repeated, joint-loading stepping activity. 3D surface models were created from patellar, femoral, and tibial articular cartilage.

STATISTICAL TESTS

Repeatability was assessed using root-mean-squared-CV (RMS-CV). Using Bland-Altman analysis, thresholds defined as the smallest detectable difference (SDD) were determined from the repeatability data with knee repositioning.

RESULTS

Without knee repositioning, both surface-averaged T and T were very repeatable on all cartilage surfaces, with RMS-CV <1.1%. Repositioning of the knee had the greatest effect on T of patellar cartilage with the surface-averaged RMS-CV = 4.8%. While T showed the greatest response to exercise at the patellofemoral cartilage region, the largest changes in T were determined in the lateral femorotibial region. Following thresholding, significant (>SDD) average exercise-induced in T and T of femoral (-8.0% and -5.3%), lateral tibial (-6.9% and -5.9%), medial tibial (+5.8% and +2.9%), and patellar (-7.9% and +2.8%) cartilage were observed.

DATA CONCLUSION

Joint-loading with a stepping activity resulted in T and T changes above background measurement error.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY STAGE: 1 J. MAGN. RESON. IMAGING 2020;52:1753-1764.