Dataset Information

Cluster analysis of quantitative MRI T₂ and T_1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.

ABSTRACT:

Purpose

To identify focal lesions of elevated MRI T₂ and T_1ρ relaxation times in articular cartilage of an ACL-injured group using a novel cluster analysis technique.

Materials and methods

Eighteen ACL-injured patients underwent 3T MRI T₂ and T_1ρ relaxometry at baseline, 6 months and 1 year and six healthy volunteers at baseline, 1 day and 1 year. Clusters of contiguous pixels above or below T₂ and T_1ρ intensity and area thresholds were identified on a projection map of the 3D femoral cartilage surface. The total area of femoral cartilage plate covered by clusters (%CA) was split into areas above (%CA+) and below (%CA-) the thresholds and the differences in %CA(+ or -) over time in the ACL-injured group were determined using the Wilcoxon signed rank test.

Results

%CA+ was greater in the ACL-injured patients than the healthy volunteers at 6 months and 1 year with average %CA+ of 5.2 ± 4.0% (p = 0.0054) and 6.6 ± 3.7% (p = 0.0041) for T₂ and 6.2 ± 7.1% (p = 0.063) and 8.2 ± 6.9% (p = 0.042) for T_1ρ, respectively. %CA- at 6 months and 1 year was 3.0 ± 1.8% (p > 0.1) and 5.9 ± 5.0% (p > 0.1) for T₂ and 4.4 ± 4.9% (p > 0.1) and 4.5 ± 4.6% (p > 0.1) for T_1ρ, respectively.

Conclusion

With the proposed cluster analysis technique, we have quantified cartilage lesion coverage and demonstrated that the ACL-injured group had greater areas of elevated T₂ and T_1ρ relaxation times as compared to healthy volunteers.

SUBMITTER: Monu UD

PROVIDER: S-EPMC5359021 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Publications

Cluster analysis of quantitative MRI T<sub>2</sub> and T<sub>1ρ</sub> relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.

Monu U D UD Jordan C D CD Samuelson B L BL Hargreaves B A BA Gold G E GE McWalter E J EJ

Osteoarthritis and cartilage 20161005 4

<h4>Purpose</h4>To identify focal lesions of elevated MRI T<sub>2</sub> and T<sub>1ρ</sub> relaxation times in articular cartilage of an ACL-injured group using a novel cluster analysis technique.<h4>Materials and methods</h4>Eighteen ACL-injured patients underwent 3T MRI T<sub>2</sub> and T<sub>1ρ</sub> relaxometry at baseline, 6 months and 1 year and six healthy volunteers at baseline, 1 day and 1 year. Clusters of contiguous pixels above or below T<sub>2</sub> and T<sub>1ρ</sub> intensity and ...[more]

PMID: 27720806

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Project description:BackgroundFast and accurate T1ρ mapping in myocardium is still a major challenge, particularly in small animal models. The complex sequence design owing to electrocardiogram and respiratory gating leads to quantification errors in in vivo experiments, due to variations of the T1ρ relaxation pathway. In this study, we present an improved quantification method for T1ρ using a newly derived formalism of a T1ρ* relaxation pathway.MethodsThe new signal equation was derived by solving a recursion problem for spin-lock prepared fast gradient echo readouts. Based on Bloch simulations, we compared quantification errors using the common monoexponential model and our corrected model. The method was validated in phantom experiments and tested in vivo for myocardial T1ρ mapping in mice. Here, the impact of the breath dependent spin recovery time Trec on the quantification results was examined in detail.ResultsSimulations indicate that a correction is necessary, since systematically underestimated values are measured under in vivo conditions. In the phantom study, the mean quantification error could be reduced from - 7.4% to - 0.97%. In vivo, a correlation of uncorrected T1ρ with the respiratory cycle was observed. Using the newly derived correction method, this correlation was significantly reduced from r = 0.708 (p < 0.001) to r = 0.204 and the standard deviation of left ventricular T1ρ values in different animals was reduced by at least 39%.ConclusionThe suggested quantification formalism enables fast and precise myocardial T1ρ quantification for small animals during free breathing and can improve the comparability of study results. Our new technique offers a reasonable tool for assessing myocardial diseases, since pathologies that cause a change in heart or breathing rates do not lead to systematic misinterpretations. Besides, the derived signal equation can be used for sequence optimization or for subsequent correction of prior study results.

Dataset Information

Cluster analysis of quantitative MRI T₂ and T_1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.

Purpose

Materials and methods

Results

Conclusion

Publications

Cluster analysis of quantitative MRI T<sub>2</sub> and T<sub>1ρ</sub> relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Dataset Information

Cluster analysis of quantitative MRI T2 and T1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.

Purpose

Materials and methods

Results

Conclusion

Publications

Cluster analysis of quantitative MRI T<sub>2</sub> and T<sub>1ρ</sub> relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Cluster analysis of quantitative MRI T₂ and T_1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T.