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. 2025 Sep;53(9):2120-2130.
doi: 10.1007/s10439-025-03774-3. Epub 2025 Jun 17.

Orientation-Independent T2 Mapping Enhances MRI-Based Cartilage Characterization

Henri P P Leskinen  1   2 , Juuso Tuppurainen  1   3 , Jiri Jäntti  1   3 , Janne T A Mäkelä  1 , Ervin Nippolainen  1 , Isaac O Afara  1   4   5 , Juha Töyräs  1   4   5 , Olli Nykänen  1 , Mikko J Nissi  6
Affiliations

Orientation-Independent T2 Mapping Enhances MRI-Based Cartilage Characterization

Henri P P Leskinen et al. Ann Biomed Eng. 2025 Sep.

Abstract

Purpose: Quantitative T2 mapping is an important MRI method for assessing degenerative changes in articular cartilage. Recently, in a measurement setup with automated sample re-orientation, it was demonstrated that T2 can be split into its orientation-independent components. This quantitative MRI study aims to assess the diagnostic significance of the automated approach with ex vivo human cartilage.

Methods: T2 maps of 30 human osteochondral samples harvested from 5 cadaveric individuals were acquired at 9.4T in 13 orientations, allowing calculation of the T2 components. Additionally, T1, adiabatic T1ρ, and continuous wave T1ρ with two spin-lock frequencies were scanned in a single orientation. For reference, the collagen network anisotropy, proteoglycan content and biomechanical indentation properties were measured. The relationships between quantitative MRI and reference parameters were studied using Mann-Whitney U-test and Spearman's rank correlation. All parameters were compared between healthy and degenerated groups based on OARSI grading.

Results: The anisotropic relaxation rate component of T2 (R2a), and all T1 and T1ρ parameters differed (p < 0.05) between the groups in superficial cartilage. R2a correlated moderately with PLM anisotropy (r = 0.44) and optical density (r = - 0.37) in the deep zone. Isotropic T2 component (R2i) correlated with instantaneous modulus (r = 0.48), and R2a with phase shift between stress and strain during indentation testing (r = - 0.44). T1 and T1ρ parameters correlated with both, instantaneous and dynamic modulus in several zones of cartilage.

Conclusion: The elevation of T2 in degenerated cartilage is primarily driven by the R2a component, whereas the R2i component showed no significant difference between healthy and degenerated human articular cartilage.

Keywords: Orientation-independent T2; Osteoarthritis; Quantitative MRI; T2 anisotropy; T2 relaxation.

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Conflict of interest statement

Declarations. Competing Interests: The authors have no competing interest regarding this study to disclose. This manuscript is entirely original, has not been copyrighted, published, submitted, or accepted for publication elsewhere. All authors have participated in the study and meet the criteria for authorship.

Figures

Fig. 1
Fig. 1
T2 parameter maps for healthy and degenerated samples. R2a, T2tot, T2 at 0° and T2 Anisotropy showed difference between SZ of healthy and degenerated samples. Changes in the appearance of the zonal structure are among the most prominent changes. △ = articular surface. ▽ = bone-cartilage interface. Please note the varying scale between samples.
Fig. 2
Fig. 2
Boxplot of qMRI parameters in the superficial zone and bulk cartilage in the two sample groups. A Isotropic and B anisotropic R2, C T2, D Adiabatic and Continuous wave T1ρ, and E) T1. Statistically significant findings indicated with an asterisk (*).
Fig. 3
Fig. 3
A Optical density B, phase shift, and C moduli results in healthy and degenerated cartilage presented as boxplots in the healthy and degenerated groups. Phase shift at 1 Hz dynamic mechanical testing showed statistically significant difference between healthy and degenerated cartilage. Statistically significant findings are indicated with an asterisk (*).
Fig. 4
Fig. 4
PLM anisotropy, optical density, and light microscopy of Saf-O -stained slices in samples with three different degeneration levels. All histological slices were parallel to each other and within 30 µm.
See this image and copyright information in PMC

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