University of Oulu

Henri P P Leskinen et al 2023 Phys. Med. Biol. 68 085004

T₂ orientation anisotropy mapping of articular cartilage using qMRI

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Author: Leskinen, Henri P P1; Hänninen, Nina E1,2; Nissi, Mikko J1
Organizations: 1Department of Technical Physics, University of Eastern Finland, Kuopio, Finland
2Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.4 MB)
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Language: English
Published: IOP Publishing, 2023
Publish Date: 2023-08-21


Objective: To provide orientation-independent MR parameters potentially sensitive to articular cartilage degeneration by measuring isotropic and anisotropic components of T₂ relaxation, as well as 3D fiber orientation angle and anisotropy via multi-orientation MR scans.

Approach: Seven bovine osteochondral plugs were scanned with a high angular resolution of thirty-seven orientations spanning 180° at 9.4 T. The obtained data was fitted to the magic angle model of anisotropic T₂ relaxation to produce pixel-wise maps of the parameters of interest. Quantitative Polarized Light Microscopy (qPLM) was used as a reference method for the anisotropy and fiber orientation.

Main results: The number of scanned orientations was found to be sufficient for estimating both fiber orientation and anisotropy maps. The relaxation anisotropy maps demonstrated a high correspondence with qPLM reference measurements of the collagen anisotropy of the samples. The scans also enabled calculating orientation-independent T₂ maps. Little spatial variation was observed in the isotropic component of T₂ while the anisotropic component was much faster in the deep radial zone of cartilage. The estimated fiber orientation spanned the expected 0°–90° in samples that had a sufficiently thick superficial layer. The orientation-independent magnetic resonance imaging (MRI) measures can potentially reflect the true properties of articular cartilage more precisely and robustly.

Significance: The methods presented in this study will likely improve the specificity of cartilage qMRI by allowing the assessment of the physical properties such as orientation and anisotropy of collagen fibers in articular cartilage.

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Series: Physics in medicine & biology
ISSN: 0031-9155
ISSN-E: 1361-6560
ISSN-L: 0031-9155
Volume: 68
Issue: 8
Article number: 085004
DOI: 10.1088/1361-6560/acc169
Type of Publication: A1 Journal article – refereed
Field of Science: 3126 Surgery, anesthesiology, intensive care, radiology
Funding: Funding from the Academy of Finland (grants #285909, #293970, #319440, and #325146) is gratefully acknowledged.
Copyright information: © 2023 The Author(s). Published on behalf of Institute of Physics and Engineering in Medicine by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.