Keywords: Cartilage, Cartilage, Repair, Tissue, Maturarion

Motivation: To monitor patients after cartilage repair surgery, non-invasive imaging techniques are needed.

Goal(s): Study aimed to monitor cartilage repair tissue for up to two years post-surgery using GLCM analysis of T₂ maps to assess tissue structure and correlate it with the morphological MOCART 2.0 score.

Approach: 37 patients underwent either matrix-associated autologous chondrocyte transplantation or microfracturing. ROI’s were drawn onto T₂ maps at three time-points. GLCM features, mean T₂  and MOCART 2.0 scores were calculated and analysed.

Results: We found correlations between GLCM features and the MOCART 2.0 score, with significant changes in texture of the repair tissue over time for transplant patients.

Impact: This study reveals a correlation between GLCM and MOCART 2.0 in autologous chondrocyte transplantation and microfracturing. Only chondrocyte transplants showed significant tissue development over time, indicating complex maturation. These findings will impact patient monitoring in clinical trials after cartilage repair.

Keywords: Osteoarthritis, Cartilage, UTE-T2*

Motivation: Clinical evidence of structural benefits to cartilage from Platelet Rich Plasma (PRP) injections to treat knee osteoarthritis is lacking.

Goal(s): Our goal was to use T2 and UTE-T2* relaxation times to assess cartilage structural improvements following PRP therapy.

Approach: Patient reported outcomes, T2 and UTE-T2* maps were acquired before and 6 months after completion of PRP treatment in 50 patients with symptomatic knee osteoarthritis.

Results: On average, participants reported symptomatic improvements following PRP. Significant changes to cartilage T2 and UTE-T2* were also observed. Improvements in patient-reported knee function and stiffness correlated to concurrent decreases in both T2 and UTE-T2*.

Impact: qMRI evaluation of the clinical efficacy of PRP treatment of symptomatic knee OA shows that changes to patient reported knee function associate with concurrent changes to cartilage structure assessed with T2 and UTE-T2*.

Keywords: Cartilage, Osteoarthritis, Relaxometry

Motivation: Weight loss has been shown to be beneficial for knee symptoms and reducing cartilage degeneration.

Goal(s): To examine the impact of weight-loss in obese subjects on articular cartilage in the tibiofemoral joint using T2 relaxation time mapping. 

Approach: Knees of 65 obese patients undergoing either bariatric surgery or conservative weight loss regimens were imaged at 3T before and three years after treatment. Changes in T2 were assessed in tibiofemoral cartilage.

Results: A reduction in body mass index (BMI) was associated with shortened T2 values in tibia, indicating that weight loss may result in improved cartilage quality.

Impact: The findings provide supporting evidence for the benefits of weight loss for cartilage health and have relevance in the context of osteoarthritis prevention and treatment.

Keywords: Osteoarthritis, Osteoarthritis

Motivation: Osteoarthritis (OA) leads to cartilage degradation and pain, impacting patients' lives. MRI allows detailed cartilage assessment; however, limited sensitivity hinders early-phase clinical trials developing disease-modifying treatments.

Goal(s): To apply 3D cartilage surface mapping in a homogeneous patient group over 12 months.

Approach: Combined morphological and compositional cartilage MRI with 3D surface-based analysis to assess longitudinal changes within patients with mild OA.

Results: Bi-directional cartilage thickness, T1ρ, and T2 alterations exceeding measurement errors were observed after 12 months. Medial femorotibial cartilage thinned, while lateral tibial cartilage thickened. Cartilage thickness changes correlated negatively with T1ρ and T2 changes in tibial and patellar cartilage.

Impact: The results and methods presented can improve understanding of early structural and compositional changes in cartilage, monitoring disease progression and assessing the effectiveness of therapeutic interventions in OA.

Keywords: Cartilage, Quantitative Imaging

Motivation: Clinical adoption of quantitative MRI for cartilage repair monitoring is hindered by a lack of standardization in acquisition and tedious image analysis.

Goal(s): Our goal was to longitudinally assess high-density autologous chondrocyte implantation (HD-ACI) in the knee using a fast and robust DL T2 mapping technique, correlating with clinical outcome.

Approach: 15 HD-ACI patients (treated in femoral/patellar compartments) were longitudinally imaged and processed with a semi-automated pipeline, enabling a standardized regional analysis at a layer level. 

Results: DL T2 map reflected longitudinal significant changes in deep layer.  Significant T2 decrease in femoral HD-ACI within the first follow-up year, correlated with good clinical progression.

Impact: The demonstrated feasibility of DL T2 mapping coupled with a semi-automatic analysis to monitor changes after HD-ACI repair, allows for further investigation of the underlying biology of quantitative findings; advancing its adoption as cartilage healing biomarker in the clinical setting. 

Keywords: Cartilage, MR Fingerprinting, Knee cartilage, Deep learning

Motivation: Estimating MRF quantitative parameters with neural networks (NNs) is faster than  dictionary-matching methods (DMs), and it has the advantage of providing continuously distributed parameters.

Goal(s): We investigate different aspects of NN training and evaluate its quantitative MRF performance and compare them with DMs.

Approach: We exploit how training data sizes, noise levels, and SVD compression sizes affect the MRF performance of the NNs and compare them with DMs.

Results: The NN provides a faster way of multi-parametric mapping from NIST/ISMRM phantom and knee joint MRF data sets with comparable performance to DMs.

Impact: Well-tuned NN is much more efficient for quantitative MRF, particularly for the knee joint. Besides computational speed, fine-tuning can also increase the performance and robustness to noise.

Keywords: Cartilage, Quantitative Imaging

Motivation: Post traumatic osteoarthritis is a common complication of ACL injury. There is limited research on the early degenerative changes in cartilage of ACL injured knees.

Goal(s): To develop novel biomarkers for identifying early cartilage damage in ACL reconstructed knees. 

Approach: We employed ultrashort echo time magnetization transfer ratio (UTE-MTR) and UTE-T1 sequence to study the knee articular cartilage in ACL reconstructed patients.

Results: UTE-T1 and UTE-MTR can be used as quantitative biomarkers for assessing cartilage damage. Reduced MTR and increased T1 values indicate cartilage damage which is otherwise not appreciated on morphological imaging.

Impact: UTE-T1 and UTE-MTR sequences can detect early cartilage damage, which could help us better understand the development of post-traumatic osteoarthritis.

Keywords: Cartilage, Cartilage, Osteoarthritis, High-Field MRI, Quantitative Imaging, Relaxometry

Motivation: MR T2 and T1ρ mapping showed great promise for reliable detection and follow-up of knee osteoarthritis, however, B1⁺ inhomogeneities in knee 7T MRI often lead to signal loss and biased quantification.

Goal(s): Present study therefore evaluates the effect of high-permittivity dielectric padding on the B1⁺ field distribution and the reproducibility of T2 and T1ρ quantification in knee cartilage and meniscus.

Approach: Twelve subjects received scan-rescan at 7T to quantify B0, B1⁺, T2, T1ρ, and reproducibility changes associated with dielectric padding.

Results: Dielectric pads positioned over tibia showed improved B1⁺ homogeneity and reproducibility of T2 and T1ρ quantification in cartilage and meniscus at 7T.

Impact: Improved reproducibility of T2 and T1ρ MRI in cartilage and meniscus with dielectric padding at 7T could facilitate its clinical translation at ultra-high field and improve patient’s follow-up for the noninvasive evaluation of new prevention and treatment strategies for osteoarthritis.

Keywords: Cartilage, Cartilage

Motivation: This research investigates the limited association between cartilage volume and knee pain in osteoarthritis, potentially confounded by anatomical variability.

Goal(s): To enhance the correlation between MRI-derived cartilage volumes and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) pain scores using a knee atlas for image registration.

Approach: Using data from the Osteoarthritis Initiative, MRIs of subjects with OA were registered to an anatomical template. The atlas-based measurements were compared with traditional methods to assess the impact on correlation with WOMAC pain scores.

Results: Atlas registration resulted in more consistent cartilage volume measures, reducing variability, and doubling the correlation with WOMAC pain scores.

Impact: In knee osteoarthritis the registration of MRIs to an anatomical template significantly increases the association between cartilage volumes and osteoarthritis pain scores, enabling more accurate and sensitive detection of pain-related cartilage changes, potentially influencing OA management and therapy development.