Multi-component T 2 ∗ relaxation modelling in human Achilles tendon: Quantifying chemical shift information in ultra-short echo time imaging.

To examine multi-component relaxation modelling for quantification of on- and off-resonance relaxation signals in multi-echo ultra-short echo time (UTE) data of human Achilles tendon (AT) and compare bias and dispersion errors of model parameters to that of the bi-component model. Multi-component modelling is demonstrated for quantitative multi-echo UTE analysis of AT and supported using a novel method for determining number of MR-visible off-resonance components, UTE data from six healthy volunteers, and analysis of proton NMR measurements from ex vivo bovine AT. Cramer-Rao lower bound expressions are presented for multi- and bi-component models and parameter estimate variances are compared. Bias error in bi-component estimates is characterized numerically. Two off-resonance components were consistently detected in all six volunteers and in bovine AT data. Multi-component model exhibited superior quality of fit, with a marginal increase in estimate variance, when compared to the bi-component model. Bi-component estimates exhibited notable bias particularly in R 2 , 1 ∗ in the presence of off-resonance components. Multi-component modelling more reliably quantifies tendon matrix water components while also providing quantitation of additional non-water matrix constituents. Further work is needed to interpret the origin of the observed off-resonance signals with preliminary assignments made to chemical groups in lipids and proteoglycans. © 2021 International Society for Magnetic Resonance in Medicine.

Citation

Muhammad A R Anjum, Felix M Gonzalez, Anshuman Swain, Johannes Leisen, Zahra Hosseini, Adam Singer, Monica Umpierrez, David A Reiter. Multi-component T 2 ∗ relaxation modelling in human Achilles tendon: Quantifying chemical shift information in ultra-short echo time imaging. Magnetic resonance in medicine. 2021 Jul;86(1):415-428

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PMID: 33590557

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