Fully automatic analysis of the knee articular cartilageT_1ρrelaxation time using voxel-based relaxometry

Abstract

Purpose To develop and compare with classical ROI-based approach, a fully-automatic, local and unbiased way of studying the knee T1ρ relaxation time by creating an atlas and using Voxel Based Relaxometry (VBR) in OA and ACL subjects Materials and Methods In this study 110 subjects from 2 cohorts: (i) Mild OA 40 patients with mild-OA KL ≤ 2 and 15 controls KL ≤ 1; (ii) ACL cohort (a model for early OA): 40 ACL-injured patients imaged prior to ACL reconstruction and 1-year post-surgery and 15 controls are analyzed. All the subjects were acquired at 3T with a protocol that includes: 3D-FSE (CUBE) and 3D-T1ρ. A Non-rigid registration technique was applied to align all the images on a single template. This allows for performing VBR to assess local statistical differences of T1ρ values using z-score analysis. VBR results are compared with those obtained with classical ROI-based technique Results ROI-based results from atlas-based segmentation were consistent with classical ROI-based method (CV = 3.83%). Voxel-based group analysis revealed local patterns that were overlooked by ROI-based approach; e.g. VBR showed posterior lateral femur and posterior lateral tibia significant T1ρ elevations in ACL injured patients (sample mean z-score=9.7 and 10.3). Those elevations were overlooked by the classical ROI-based approach (sample mean z-score =1.87, and −1.73) Conclusion VBR is a feasible and accurate tool for the local evaluation of the biochemical composition of knee articular cartilage. VBR is capable of detecting specific local patterns on T1ρ maps in OA and ACL subjects

The association between MR T1ρ and T2 of cartilage and patient-reported outcomes after ACL injury and reconstruction

“…Additionally, all T1ρ and T2 echoes of the contralateral knee were registered to first T1ρ echo of the injured knee to assure that the same anatomical regions of cartilage were being compared in the analysis. The registration was accomplished using an intensity-based multi-resolution pyramidal approach 29, 30 . Mean T1ρ and T2 values were calculated for each cartilage compartment after transferring the segmentations from CUBE onto the maps.…”

Principal component analysis-T1ρ voxel based relaxometry of the articular cartilage: a comparison of biochemical patterns in osteoarthritis and anterior cruciate ligament subjects

“…All images were morphed to the space of a reference to obtain anatomically matched T 1ρ -weighed images using a previously developed technique (21). Briefly, we applied an intensity-based multi-resolution pyramidal approach.…”

“…A novel, fully-automatic and unbiased algorithm for studying knee relaxation times has been previously proposed, by creating an atlas of the knees and using voxelbased relaxometry (VBR) (21). This technique allows for the investigation of local cartilage composition differences between two groups through voxel-based statistical parametric mapping (SPM).…”

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

“…Texture, laminar and Z-score analyses have been used to examine the spatial distribution and heterogeneously quantitative data within the cartilage, showing that the natural heterogeneity of quantitative T 2 and T 1ρ values in healthy cartilage, typically increases with OA 26,27,28–32 . These processing techniques have shown promise but to date few investigations look at the full cartilage plate, therefore missing important regions of degeneration, such as the trochlea 30,33 . One challenge to carrying out 3D comparisons is the registration of data between time-points and individuals.…”