• Rahman Baboli, Azadeh Sharafi, Gregory Chang, and Ravinder R Regatte.
• Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.
• J Magn Reson Imaging. 2018 Dec 1; 48 (6): 1707-1716.

BackgroundThe 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.PurposeTo 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.Study TypeProspective.PopulationTen healthy volunteers with no known inflammation, trauma, or pain in the knee.Field Strength/SequenceStandard FLASH sequence and customized Turbo-FLASH sequence to acquire 3D-isotropic-T1 ρ-weighted images on a 3T MRI scanner.AssessmentThe mean volume and thickness along with mono- and biexponential T1 ρ relaxations were assessed in the articular cartilage of 10 healthy volunteers.Statistical TestsNonparametric rank-sum tests. Bland-Altman analysis and coefficient of variation.ResultsThe 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.Data ConclusionSimultaneous 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.Level Of Evidence2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:1707-1716.© 2018 International Society for Magnetic Resonance in Medicine.

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