Three‐Dimensional Surface‐Based Analysis of Cartilage MRI Data in Knee Osteoarthritis: Validation and Initial Clinical Application

Abstract

Background Traditional quantitative analysis of cartilage with MRI averages measurements (eg, thickness) across regions‐of‐interest (ROIs) which may reduce responsiveness. Purpose To validate and describe clinical application of a semiautomated surface‐based method for analyzing cartilage relaxation times (“composition”) and morphology on MRI, 3D cartilage surface mapping (3D‐CaSM). Study Type Validation study in cadaveric knees and prospective observational (cohort) study in human participants. Population Four cadaveric knees and 14 participants aged 40–60 with mild–moderate knee osteoarthritis (OA) and 6 age‐matched healthy volunteers, imaged at baseline, 1, and 6 months. Field Strength/Sequence 3D spoiled gradient echo, T1rho/T2 magnetization‐prepared 3D fast spin echo for mapping of T1rho/T2 relaxation times and delayed gadolinium enhanced MRI of cartilage (dGEMRIC) using variable flip angle T1 relaxation time mapping at 3T. Assessment 3D‐CaSM was validated against high‐resolution peripheral quantitative computed tomography (HRpQCT) in cadaveric knees, with comparison to expert manual segmentation. The clinical study assessed test–retest repeatability and sensitivity to change over 6 months for cartilage thickness and relaxation times. Statistical Tests Bland–Altman analysis was performed for the validation study and evaluation of test–retest repeatability. Six‐month changes were assessed via calculation of the percentage of each cartilage surface affected by areas of significant change (%SC), defined using thresholds based on area and smallest detectable difference (SDD). Results Bias and precision (0.06 ± 0.25 mm) of 3D‐CaSM against reference HRpQCT data were comparable to expert manual segmentation (−0.13 ± 0.26 mm). 3D‐CaSM demonstrated significant (>SDD) 6‐month changes in cartilage thickness and relaxation times in both OA participants and healthy controls. The parameter demonstrating the greatest 6‐month change was T2 relaxation time (OA median %SC [IQR] = 8.8% [5.5 to 12.6]). Data Conclusion This study demonstrates the construct validity and potential clinical utility of 3D‐CaSM, which may offer advantages to conventional ROI‐based methods. Level of Evidence 2. Technical Efficacy Stage 2. J. Magn. Reson. Imaging 2020;52:1139–1151.

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

“…A 3D surface analysis provides the possibility of spatially localizing the deformational and compositional effects of joint-loading on articular cartilage and could also assist in determining the regions most prone to exhibit cartilage degeneration. 29…”

“…As the disease‐induced compositional changes in cartilage reflected in T 1ρ and T 2 measurements can be of the same order, and appear in similar cartilage regions, as exercise‐induced changes, it is important to mitigate these effects when conducting clinical OA trials. A 3D surface analysis provides the possibility of spatially localizing the deformational and compositional effects of joint‐loading on articular cartilage and could also assist in determining the regions most prone to exhibit cartilage degeneration 29 …”

“…Surface‐based analysis (3D Cartilage Surface Mapping, 3D‐CaSM) of femoral, tibial, and patellar cartilage was performed using the freely available Stradwin software v. 5.4a (University of Cambridge Department of Engineering, Cambridge, UK; now freely available as “StradView” at http://mi.eng.cam.ac.uk/Main/StradView/). 29 After creating sparse manual cross‐sections (on every 2 nd –4 th sagittal slice) of the patella, tibia, and femur including their surrounding cartilage on the 3D‐FS SPGR datasets, a triangulated surface mesh object of each segmented bone–cartilage structure was automatically generated using shape‐based interpolation and the regularized marching tetrahedra method 30 . Following cartilage thickness calculation and the generation of inner and outer cartilage surfaces, these surfaces were used to analyze the registered quantitative T 1ρ and T 2 maps.…”

Quantitative analysis of the ACL and PCL using T1rho and T2 relaxation time mapping: an exploratory, cross-sectional comparison between OA and healthy control knees

“…The subject cohort used in this cross-sectional study has previously been described in a study assessing longitudinal changes in cartilage morphology and composition [ 12 ]. Between April 2017 and June 2018, 15 patients with knee OA were recruited from specialist orthopaedic knee clinics at a University teaching hospital.…”

“…Quantitative MRI may also be helpful in such studies looking at understanding and monitoring the biological changes that occur in ligaments post augmentation or repair. Newer techniques have used 3D cartilage surface mapping to analyse these cartilage changes [ 12 ]. Furthermore, Prasad et al used a longitudinal approach and found that T1rho and T2 measurements may predict progression of knee OA, in particular degenerative cartilage abnormalities [ 13 ].…”