Isotropic morphometry and multicomponent T₁ ρ mapping of human knee articular cartilage in vivo at 3T

The progressive loss of hyaline articular cartilage due to osteoarthritis (OA) changes the functional and biochemical properties of cartilage. Measuring the T₁ ρ along with the morphological assessment can potentially be used as noninvasive biomarkers in detecting early-stage OA. To correlate the biochemical and morphological data, submillimeter isotropic resolution for both studies is required.

To implement a high spatial resolution 3D-isotropic-MRI sequence for simultaneous assessment of morphological and biexponential T₁ ρ relaxometry of human knee cartilage in vivo.

Prospective.

Ten healthy volunteers with no known inflammation, trauma, or pain in the knee.

Standard FLASH sequence and customized Turbo-FLASH sequence to acquire 3D-isotropic-T₁ ρ-weighted images on a 3T MRI scanner.

The mean volume and thickness along with mono- and biexponential T₁ ρ relaxations were assessed in the articular cartilage of 10 healthy volunteers.

Nonparametric rank-sum tests. Bland-Altman analysis and coefficient of variation.

The mean monoexponential T₁ ρ relaxation was 40.7 ± 4.8 msec, while the long and short components were 58.2 ± 3.9 msec and 6.5 ± 0.6 msec, respectively. The mean fractions of long and short T₁ ρ relaxation components were 63.7 ± 5.9% and 36.3 ± 5.9%, respectively. Statistically significant (P ≤ 0.03) differences were observed in the monoexponential and long components between some of the regions of interest (ROIs). No gender differences between biexponential components were observed (P > 0.05). Mean cartilage volume and thickness were 25.9 ± 6.4 cm³ and 2.2 ± 0.7 mm, respectively. Cartilage volume (P = 0.01) and thickness (P = 0.03) were significantly higher in male than female participants across all ROIs. Bland-Altman analysis showed agreement between two morphological methods with limits of agreement between -1000 mm³ and +1100 mm³ for volume, and -0.78 mm and +0.46 mm for thickness, respectively.

Simultaneous assessment of morphological and multicomponent T₁ ρ relaxation of knee joint with 0.7 × 0.7 × 0.7 mm isotropic spatial resolution is demonstrated in vivo. Comparison with a standard method showed that the proposed technique is suitable for assessing the volume and thickness of articular cartilage.

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:1707-1716.