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Purpose: To evaluate in vivo T2 mapping as quantitative, imaging-based biomarker for meniscal degeneration in humans, by studying the correlation between T2 relaxation time and degree of histological degeneration as reference standard.Methods: In this prospective validation study, 13 menisci from seven patients with radiographic knee osteoarthritis (median age 67 years, three males) were included. Menisci were obtained during total knee replacement surgery. All patients underwent pre-operative magnetic resonance imaging using a 3-T MR scanner which included a T2 mapping pulse sequence with multiple echoes. Histological analysis of the collected menisci was performed using the Pauli score, involving surface integrity, cellularity, matrix organization, and staining intensity. Mean T2 relaxation times were calculated in meniscal regions of interest corresponding with the areas scored histologically, using a multi-slice multi-echo postprocessing algorithm. Correlation between T2 mapping and histology was assessed using a generalized least squares model fit by maximum likelihood.Results: The mean T2 relaxation time was 22.4 ± 2.7 ms (range 18.5-27). The median histological score was 10, IQR 7-11 (range 4-13). A strong correlation between T2 relaxation time and histological score was found (rs = 0.84, CI 95% 0.64-0.93).Conclusion: In vivo T2 mapping of the human meniscus correlates strongly with histological degeneration, suggesting that T2 mapping enables the detection and quantification of early compositional changes of the meniscus in knee OA.Key Points: • Prospective histology-based study showed that in vivo T 2 mapping of the human meniscus correlates strongly with histological degeneration. • Meniscal T 2 mapping allows detection and quantifying of compositional changes, without need for contrast or special MRI hardware. • Meniscal T 2 mapping provides a biomarker for early OA, potentially allowing early treatment strategies and prevention of OA progression. [ABSTRACT FROM AUTHOR]

Due to aging populations and increasing rates of obesity in the developed world, the prevalence of osteoarthritis (OA) is continually increasing. Decreasing the societal and patient burden of this disease motivates research in prevention, early detection of OA, and novel treatment strategies against OA. One key facet of this effort is the need to track the degradation of tissues within joints, especially cartilage. Currently, conventional imaging techniques provide accurate means to detect morphological deterioration of cartilage in the later stages of OA, but these methods are not sensitive to the subtle biochemical changes during early disease stages. Novel quantitative techniques with magnetic resonance imaging (MRI) provide direct and indirect assessments of cartilage composition, and thus allow for earlier detection and tracking of OA. This review describes the most prominent quantitative MRI techniques to date-dGEMRIC, T2 mapping, T1rho mapping, and sodium imaging. Other, less-validated methods for quantifying cartilage composition are also described-Ultrashort echo time (UTE), gagCEST, and diffusion-weighted imaging (DWI). For each technique, this article discusses the proposed biochemical correlates, as well its advantages and limitations for clinical and research use. The article concludes with a detailed discussion of how the field of quantitative MRI has progressed to provide information regarding two specific patient populations through clinical research-patients with anterior cruciate ligament rupture and patients with impingement in the hip. While quantitative imaging techniques continue to rapidly evolve, specific challenges for each technique as well as challenges to clinical applications remain.

'Delayed gadolinium-enhanced MRI of cartilage' (dGEMRIC) and 'T2 mapping' are novel MRI techniques to quantitatively measure the quality of articular cartilage. The advantage of these novel techniques is that they are able to detect the loss of important composites of cartilage before damage to and deformities of the cartilage become visible on radiographs or on conventional MRI. These novel MRI techniques can be used to investigate the effectiveness of potentially preventative or disease-modifying therapy at an early stage of cartilage disease, e.g. in osteoarthritis. It is possible that in the future dGEMRIC and T2 mapping will be used in routine clinical practice to diagnose osteoarthritis at an earlier stage and to predict disease progression. However, much more research is still needed. At the Erasmus Medical Center in Rotterdam, the Netherlands, work is being carried out on the validation, implementation and translation into clinical practice of these and other novel techniques of quantitative measurement of cartilage quality.