Multi-vendor multi-site T(1ρ) and T(2) quantification of knee cartilage

Cartilage compositional MRI-a narrative review of technical development and clinical applications over the past three decades

Articular cartilage damage and degeneration are among hallmark manifestations of joint injuries and arthritis, classically osteoarthritis. Cartilage compositional MRI (Cart-C MRI), a quantitative technique, which aims to detect early-stage cartilage matrix changes that precede macroscopic alterations, began development in the 1990s. However, despite the significant advancements over the past three decades, Cart-C MRI remains predominantly a research tool, hindered by various technical and clinical hurdles. This paper will review the technical evolution of Cart-C MRI, delve into its clinical applications, and conclude by identifying the existing gaps and challenges that need to be addressed to enable even broader clinical application of Cart-C MRI.

Novel spin-lock time sampling strategies for improved reproducibility in quantitative T1ρ mapping

This study aimed to optimize the sampling of spin-lock times (TSLs) in quantitative T1ρ mapping for improved reproducibility. Two new TSL sampling schemes were proposed: (i) reproducibility-guided random sampling (RRS) and (ii) reproducibility-guided optimal sampling (ROS). They were compared to the existing linear sampling (LS) and precision-guided sampling (PS) schemes for T1ρ reproducibility through numerical simulations, phantom experiments, and volunteer studies. Each study evaluated the four sampling schemes with three commonly used T1ρ preparations based on composite and balanced spin-locking. Additionally, the phantom and volunteer studies investigated the impact of B0 and B1 field inhomogeneities on T1ρ reproducibility, respectively. The reproducibility was assessed using the coefficient of variation (CoV) by repeating the T1ρ measurements eight times for phantom experiments and five times for volunteer studies. Numerical simulations resulted in lower mean CoVs for the proposed RRS (1.74%) and ROS (0.68%) compared to LS (2.93%) and PS (3.68%). In the phantom study, the mean CoVs were also lower for RRS (2.7%) and ROS (2.6%) compared to LS (4.1%) and PS (3.1%). Furthermore, the mean CoVs of the proposed RRS and ROS were statistically lower (P < 0.001) compared to existing LS and PS schemes at a B1 offset of 20%. In the volunteer study, consistently lower mean CoVs were observed in bilateral thigh muscles for RRS (9.3%) and ROS (9.2%) compared to LS (10.9%) and PS (10.2%), and the difference was more prominent at B0 offsets higher than 50 Hz. The proposed sampling schemes improve the reproducibility of quantitative T1ρ mapping by optimizing the selection of TSLs. This improvement is especially beneficial for longitudinal studies that track and monitor disease progression and treatment response.

Repeatability of Quantitative Knee Cartilage T1, T2, and T1ρ Mapping With 3D-MRI Fingerprinting

BACKGROUND

Three-dimensional MR fingerprinting (3D-MRF) techniques have been recently described for simultaneous multiparametric mapping of knee cartilage. However, investigation of repeatability remains limited.

PURPOSE

To assess the intra-day and inter-day repeatabilities of knee cartilage T1, T2, and T1ρ maps using a 3D-MRF sequence for simultaneous measurement.

STUDY TYPE

Prospective.

SUBJECTS

Fourteen healthy subjects (35.4 ± 9.3 years, eight males), scanned on Day 1 and Day 7.

FIELD STRENGTH/SEQUENCE

3 T/3D-MRF, T1, T2, and T1ρ maps.

ASSESSMENT

The acquisition of 3D-MRF cartilage (simultaneous acquisition of T1, T2, and T1ρ maps) were acquired using a dictionary pattern-matching approach. Conventional cartilage T1, T2, and T1ρ maps were acquired using variable flip angles and a modified 3D-Turbo-Flash sequence with different echo and spin-lock times, respectively, and were fitted using mono-exponential models. Each sequence was acquired on Day 1 and Day 7 with two scans on each day.

STATISTICAL TESTS

The mean and SD for cartilage T1, T2, and T1ρ were calculated in five manually segmented regions of interest (ROIs), including lateral femur, lateral tibia, medial femur, medial tibia, and patella cartilages. Intra-subject and inter-subject repeatabilities were assessed using coefficient of variation (CV) and intra-class correlation coefficient (ICC), respectively, on the same day and among different days. Regression and Bland-Altman analysis were performed to compare maps between the conventional and 3D-MRF sequences.

RESULTS

The CV in all ROIs was lower than 7.4%, 8.4%, and 7.5% and the ICC was higher than 0.56, 0.51, and 0.52 for cartilage T1, T2, and T1ρ, respectively. The MRF results had a good agreement with the conventional methods with a linear regression slope >0.61 and R2 > 0.59.

CONCLUSION

The 3D-MRF sequence had high intra-subject and inter-subject repeatabilities for simultaneously measuring knee cartilage T1, T2, and T1ρ with good agreement with conventional sequences.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 1.

T1rho MR properties of human patellar cartilage: correlation with indentation stiffness and biochemical contents

OBJECTIVE

Cartilage degeneration involves structural, compositional, and biomechanical alterations that may be detected non-invasively using quantitative MRI. The goal of this study was to determine if topographical variation in T1rho values correlates with indentation stiffness and biochemical contents of human patellar cartilage.

DESIGN

Cadaveric patellae from unilateral knees of 5 donors with moderate degeneration were imaged at 3-Telsa with spiral chopped magnetization preparation T1rho sequence. Indentation testing was performed, followed by biochemical analyses to determine water and sulfated glycosaminoglycan contents. T1rho values were compared to indentation stiffness, using semi-circular regions of interest (ROIs) of varying sizes at each indentation site. ROIs matching the resected tissues were analyzed, and univariate and multivariate regression analyses were performed to compare T1rho values to biochemical contents.

RESULTS

Grossly, superficial degenerative change of the cartilage (i.e., roughened texture and erosion) corresponded with regions of high T1rho values. High T1rho values correlated with low indentation stiffness, and the strength of correlation varied slightly with the ROI size. Spatial variations in T1rho values correlated positively with that of the water content (R2 = 0.10, p < 0.05) and negatively with the variations in the GAG content (R2 = 0.13, p < 0.01). Multivariate correlation (R2 = 0.23, p < 0.01) was stronger than either of the univariate correlations.

CONCLUSION

These results demonstrate the sensitivity of T1rho values to spatially varying function and composition of cartilage and that the strength of correlation depends on the method of data analysis and consideration of multiple variables.

Variation in cartilage T2 and T2* mapping of the wrist: a comparison between 3- and 7-T MRI

BACKGROUND

To analyze regional variations in T2 and T2* relaxation times in wrist joint cartilage and the triangular fibrocartilage complex (TFCC) at 3 and 7 T and to compare values between field strengths.

METHODS

Twenty-five healthy controls and 25 patients with chronic wrist pain were examined at 3 and 7 T on the same day using T2- and T2*-weighted sequences. Six different regions of interest (ROIs) were evaluated for cartilage and 3 ROIs were evaluated at the TFCC based on manual segmentation. Paired t-tests were used to compare T2 and T2* values between field strengths and between different ROIs. Spearman's rank correlation was calculated to assess correlations between T2 and T2* time values at 3 and 7 T.

RESULTS

T2 and T2* time values of the cartilage differed significantly between 3 and 7 T for all ROIs (p ≤ 0.045), with one exception: at the distal lunate, no significant differences in T2 values were observed between field strengths. T2* values differed significantly between 3 and 7 T for all ROIs of the TFCC (p ≤ 0.001). Spearman's rank correlation between 3 and 7 T ranged from 0.03 to 0.62 for T2 values and from 0.01 to 0.48 for T2* values. T2 and T2* values for cartilage varied across anatomic locations in healthy controls at both 3 and 7 T.

CONCLUSION

Quantitative results of T2 and T2* mapping at the wrist differ between field strengths, with poor correlation between 3 and 7 T. Local variations in cartilage T2 and T2* values are observed in healthy individuals.

RELEVANCE STATEMENT

T2 and T2* mapping are feasible for compositional imaging of the TFCC and the cartilage at the wrist at both 3 and 7 T, but the clinical interpretation remains challenging due to differences between field strengths and variations between anatomic locations.

KEY POINTS

•Field strength and anatomic locations influence T2 and T2* values at the wrist. •T2 and T2* values have a poor correlation between 3 and 7 T. •Local reference values are needed for each anatomic location for reliable interpretation.

Patellar Dislocation in Adolescent Patients: Influence on Cartilage Properties Based on T1ρ Relaxation Times

BACKGROUND

Adolescents who experience a patellar dislocation have an elevated risk of patellofemoral posttraumatic osteoarthritis. Magnetic resonance imaging (MRI)-based T1ρ relaxation times were measured for adolescents to evaluate patellofemoral cartilage after patellar dislocation. Long T1ρ relaxation times are an indicator of cartilage degradation.

HYPOTHESIS

The primary hypothesis is that patellofemoral cartilage T1ρ relaxation times will be elevated in the acute phase after patellar dislocation. The secondary hypothesis is that T1ρ relaxation times will be higher for knees with multiple rather than single dislocations due to repeated traumatic injury.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In total, 23 adolescents being treated for a recent patellar dislocation, 13 for a first-time dislocation (47 ± 38 days since most recent dislocation) and 10 for multiple dislocations (55 ± 24 days since most recent dislocation), and 10 healthy controls participated in MRI-based T1ρ relaxation time mapping. For multiple regions of the patellofemoral joint, mean T1ρ values were compared between the 3 groups with multiple group comparisons and post hoc tests. T1ρ relaxation times were also correlated against measures of patellofemoral anatomy and alignment for single and multiple dislocations. Statistical significance was set at P < .05.

RESULTS

T1ρ relaxation times were significantly longer for injured knees (single and multiple dislocations) than controls at the medial and central patella and central trochlear groove. For the regions on the patella, significant differences between injured and control knees exceeded 15%. No significant differences were identified between single and multiple dislocations. For the initial dislocation group, T1ρ relaxation times within multiple regions of the patellofemoral joint were significantly correlated with lateral patellar alignment or patellar height.

CONCLUSION

Elevated patellofemoral cartilage T1ρ relaxation times are consistent with a high risk of long-term patellofemoral osteoarthritis for adolescents who experience patellar dislocations. T1ρ relaxation times were elevated for multiple regions of patellofemoral cartilage. T1ρ relaxation times were expected to increase with additional dislocation episodes, but relaxation times after single and multiple dislocations were similar. After a first dislocation, parameters related to patellar maltracking were correlated with cartilage degradation.

3D T1rho sequences with FASE, UTE, and MAPSS acquisitions for knee evaluation

PURPOSE

For biochemical evaluation of soft tissues of the knee, T1rho magnetic resonance imaging (MRI) has been proposed. Purpose of this study was to compare three T1rho sequences based on fast advanced spin echo (FASE), ultrashort echo time (UTE), and magnetization-prepared angle-modulated partitioned k-space spoiled gradient echo snapshots (MAPSS) acquisitions for the knee evaluation.

MATERIALS AND METHODS

We developed two T1rho sequences using 3D FASE or 3D radial UTE acquisitions. 3D MAPSS T1rho was provided by the manufacturer. Agarose phantoms with varying concentrations were imaged. Additionally, bilateral knees of asymptomatic subjects were imaged sagittally. T1rho values of the phantoms and 4 regions of interest (ROI) of the knees (i.e., anterior and posterior meniscus, femoral and tibial cartilage) were determined.

RESULTS

In phantoms, all T1rho values monotonically decreased with increasing agarose concentration. 3D MAPSS T1rho values of 51, 34, and 38 ms were found for 2, 3, and 4% agarose, respectively, similar to published values on another platform. In the knee, the raw images were detailed with good contrast. Cartilage and meniscus T1rho values varied with the pulse sequence, being the lowest in the 3D UTE T1rho sequence. Comparing different ROIs, menisci generally had lower T1rho values compared to cartilage, as expected in healthy knees.

CONCLUSION

We have successfully developed and implemented the new T1rho sequences and validated them using agarose phantoms and volunteer knees. All sequences were optimized to be clinically feasible (~ 5 min or less) and yielded satisfactory image quality and T1rho values consistent with the literature.

MRI-based T1rho and T2 cartilage compositional imaging in osteoarthritis: what have we learned and what is needed to apply it clinically and in a trial setting?

Cartilage MRI-based T1rho and T2 compositional measurements have been developed to characterize cartilage matrix quality and diagnose cartilage damage before irreversible defects are found, allowing intervention at an early, potentially reversible disease stage. Over the last 2 decades, this technology was investigated in numerous studies and was validated using specimen studies and arthroscopy; and longitudinal studies documented its ability to predict progression of degenerative disease and radiographic osteoarthritis (OA). While T1rho and T2 measurements have shown promise in early disease stages, several hurdles have been encountered to apply this technology clinically. These include (i) challenges with cartilage segmentation, (ii) long image acquisition times, (iii) a lack of standardization of imaging, and (iv) an absence of reference databases and definitions of abnormal cut-off values. Progress has been made by developing deep-learning based automatic cartilage segmentation and faster imaging methods, enabling the feasibility of T1rho and T2 imaging for clinical and scientific trial applications. Also, the Radiological Society of North America (RSNA) Quantitative Imaging Biomarker Alliance mechanism was used to establish standardized profiles for compositional T1rho and T2 imaging, and multi-center feasibility testing is work in progress. The last hurdles are the development of reference databases and establishing a definition of normal versus abnormal cartilage T1rho and T2 values. Finally, effective treatments for prevention and slowing progression of OA are required in order to establish T1rho and T2 as imaging biomarkers for initiating and monitoring therapies, analogous to the role of dual X-ray absorptiometry (DXA) bone mineral density measurements in the management of osteoporosis. KEY POINTS: • T1rho and T2 cartilage measurements have been validated in characterizing cartilage degenerative change using histology and arthroscopy as a reference. • They have also been shown to predict progression of cartilage degeneration and incidence of radiographic OA. • Advances have been made to facilitate clinical and trial application of T1rho and T2 by improved standardization of imaging and by establishing deep learning-based automatic cartilage segmentation. • Effective treatments with disease-modifying OA specific drugs may establish T1rho and T2 cartilage compositional measurements as biomarkers to initiate and monitor treatment.

Repeatability of quantitative T1rho magnetic resonance imaging in normal brain tissues at 3.0T

PURPOSE

T1rho imaging is a promising MRI technique for imaging of brain disease. This study aimed to assess the repeatability of quantitative T1rho imaging in the normal brain grey and white matter.

METHODS

The study prospectively recruited 30 healthy volunteers without a history of neurological diseases or brain injury, and T1rho was performed and quantified from three imaging sessions. Repeat measures analysis of variance (ANOVA) and within-subject coefficients of variation (wCoV) was used to detect differences in T1rho values between the three scans.

RESULTS

The results showed low wCoVs of less than 4.3% (range 0.92-4.27%) across all the brain structures. No significant differences were observed in T1rho measurement between the three scans (p > 0.05). The amygdala and hippocampus showed the highest T1rho values of 91.79 ± 2.55 msec and 91.07 ± 2.11 msec respectively, and the palladium and putamen had the lowest values of 67.60 ± 1.84 msec and 71.83 ± 1.85 msec respectively.

CONCLUSION

T1rho shows high test-retest repeatability for whole brain imaging in serial imaging sessions, indicating it to be a reliable sequence for quantitative brain imaging.

Updates on Compositional MRI Mapping of the Cartilage: Emerging Techniques and Applications

Osteoarthritis (OA) is a widely occurring degenerative joint disease that is severely debilitating and causes significant socioeconomic burdens to society. Magnetic resonance imaging (MRI) is the preferred imaging modality for the morphological evaluation of cartilage due to its excellent soft tissue contrast and high spatial resolution. However, its utilization typically involves subjective qualitative assessment of cartilage. Compositional MRI, which refers to the quantitative characterization of cartilage using a variety of MRI methods, can provide important information regarding underlying compositional and ultrastructural changes that occur during early OA. Cartilage compositional MRI could serve as early imaging biomarkers for the objective evaluation of cartilage and help drive diagnostics, disease characterization, and response to novel therapies. This review will summarize current and ongoing state-of-the-art cartilage compositional MRI techniques and highlight emerging methods for cartilage compositional MRI including MR fingerprinting, compressed sensing, multiexponential relaxometry, improved and robust radio-frequency pulse sequences, and deep learning-based acquisition, reconstruction, and segmentation. The review will also briefly discuss the current challenges and future directions for adopting these emerging cartilage compositional MRI techniques for use in clinical practice and translational OA research studies. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

The Corticosteroid Meniscectomy Trial of Extended-Release Triamcinolone Injection After Arthroscopic Partial Meniscectomy: Protocol for a Double-Blind Randomized Controlled Trial

Background

Meniscal tear in older adults often accompanies knee osteoarthritis and is commonly treated with arthroscopic partial meniscectomy (APM) when patients have persistent pain after a trial of physical therapy. Cross-sectional evidence suggests that synovitis is associated with baseline pain in this patient population, but little is known about the relationship between synovitis and postoperative recovery or progression of knee osteoarthritis.

Purpose/Hypothesis

Intra-articular extended-release triamcinolone may reduce inflammation and thereby improve outcomes and slow disease progression. This article presents the rationale behind the Corticosteroid Meniscectomy Trial (CoMeT) and describes its study design and implementation strategies.

Study Design

Randomized controlled trial.

Methods

CoMeT is a 2-arm, 3-center, randomized placebo-controlled trial designed to establish the clinical efficacy of extended-release triamcinolone administered via intra-articular injection immediately after APM. The primary outcome is change in Knee injury and Osteoarthritis Outcome Score Pain subscore at 3-month follow-up. Synovial biopsy, joint fluid aspirate, and urine and blood sample analyses will examine the associations between various objective measures of baseline inflammation and pre- and postoperative outcome measures and clinical responses to triamcinolone intervention. Quantitative 3-T magnetic resonance imaging will evaluate cartilage and meniscal composition and 3-dimensional bone shape to detect early joint degeneration.

Results

We discuss methodologic innovations and challenges.

Conclusion

To our knowledge, this is the first randomized double-blind clinical trial that will analyze the effect of extended-release triamcinolone acetonide on pain, magnetic resonance imaging measures of structural change and effusion/synovitis, soluble biomarkers, and synovial tissue transcriptomics after APM.

Reproducibility of T1ρ and T2 quantification in a multi-vendor multi-site study

OBJECTIVE

To evaluate the multi-vendor multi-site reproducibility of two-dimensional (2D) multi-echo spin-echo (MESE) T2 mapping (product sequences); and to evaluate the longitudinal reproducibility of three-dimensional (3D) magnetization-prepared angle-modulated partitioned k-space spoiled gradient echo snapshots (MAPSS) T1ρ and T2 mapping (research sequences), and 2D MESE T2 mapping, separated by 6 months, in a multi-vendor multi-site setting.

METHODS

Phantoms and volunteers (n = 5 from each site, n = 20 in total) were scanned on four 3 T magnetic resonance (MR) systems from four sites and three vendors (Siemens, General Electric, and Phillips). Two traveling volunteers (3 knees) scanned at all 4 sites at baseline and 6-month follow-up. Data was transferred to one site for centralized processing. Coefficients of variation (CVs) were calculated to evaluate reproducibility.

RESULTS

For baseline 2D MESE T2 measures, average CV were 0.37-2.45% (intra-site) and 5.96% (inter-site) for phantoms, and 3.15-8.49% (intra-site) and 14.16% (inter-site) for volunteers. For longitudinal phantom data, intra-site CVs were 1.42-3.48% for 3D MAPSS T1ρ, 1.77-3.56% for 3D MAPSS T2, and 1.02-2.54% for 2D MESE T2. For the longitudinal volunteer data, the intra-site CVs were 2.60-4.86% for 3D MAPSS T1ρ, 3.33-7.25% for 3D MAPSS T2, and 3.11-8.77% for 2D MESE T2.

CONCLUSION

This study demonstrated excellent intra-site reproducibility of 2D MESE T2 imaging, while its inter-site variation was slightly higher than 3D MAPSS T2 imaging (10.06% as previously reported). This study also showed excellent reproducibility of longitudinal T1ρ and T2 cartilage quantification, in a multi-vendor multi-site setting for both product 2D MESE T2 and 3D MAPSS T1p/T2 research sequences.

Quantitative MRI for Evaluation of Musculoskeletal Disease: Cartilage and Muscle Composition, Joint Inflammation, and Biomechanics in Osteoarthritis

ABSTRACT

Magnetic resonance imaging (MRI) is a valuable tool for evaluating musculoskeletal disease as it offers a range of image contrasts that are sensitive to underlying tissue biochemical composition and microstructure. Although MRI has the ability to provide high-resolution, information-rich images suitable for musculoskeletal applications, most MRI utilization remains in qualitative evaluation. Quantitative MRI (qMRI) provides additional value beyond qualitative assessment via objective metrics that can support disease characterization, disease progression monitoring, or therapy response. In this review, musculoskeletal qMRI techniques are summarized with a focus on techniques developed for osteoarthritis evaluation. Cartilage compositional MRI methods are described with a detailed discussion on relaxometric mapping (T 2 , T 2 *, T 1ρ ) without contrast agents. Methods to assess inflammation are described, including perfusion imaging, volume and signal changes, contrast-enhanced T 1 mapping, and semiquantitative scoring systems. Quantitative characterization of structure and function by bone shape modeling and joint kinematics are described. Muscle evaluation by qMRI is discussed, including size (area, volume), relaxometric mapping (T 1 , T 2 , T 1ρ ), fat fraction quantification, diffusion imaging, and metabolic assessment by 31 P-MR and creatine chemical exchange saturation transfer. Other notable technologies to support qMRI in musculoskeletal evaluation are described, including magnetic resonance fingerprinting, ultrashort echo time imaging, ultrahigh-field MRI, and hybrid MRI-positron emission tomography. Challenges for adopting and using qMRI in musculoskeletal evaluation are discussed, including the need for metal artifact suppression and qMRI standardization.

SuperMAP: Deep ultrafast MR relaxometry with joint spatiotemporal undersampling

PURPOSE

To develop an ultrafast and robust MR parameter mapping network using deep learning.

THEORY AND METHODS

We design a deep learning framework called SuperMAP that directly converts a series of undersampled (both in k-space and parameter-space) parameter-weighted images into several quantitative maps, bypassing the conventional exponential fitting procedure. We also present a novel technique to simultaneously reconstruct T1rho and T2 relaxation maps within a single scan. Full data were acquired and retrospectively undersampled for training and testing using traditional and state-of-the-art techniques for comparison. Prospective data were also collected to evaluate the trained network. The performance of all methods is evaluated using the parameter qualification errors and other metrics in the segmented regions of interest.

RESULTS

SuperMAP achieved accurate T1rho and T2 mapping with high acceleration factors (R = 24 and R = 32). It exploited both spatial and temporal information and yielded low error (normalized mean square error of 2.7% at R = 24 and 2.8% at R = 32) and high resemblance (structural similarity of 97% at R = 24 and 96% at R = 32) to the gold standard. The network trained with retrospectively undersampled data also works well for the prospective data (with a slightly lower acceleration factor). SuperMAP is also superior to conventional methods.

CONCLUSION

Our results demonstrate the feasibility of generating superfast MR parameter maps through very few undersampled parameter-weighted images. SuperMAP can simultaneously generate T1rho and T2 relaxation maps in a short scan time.

Early knee OA definition-what do we know at this stage? An imaging perspective

While criteria for early-stage knee osteoarthritis (OA) in a primary care setting have been proposed, the role of imaging has been limited to radiography using the standard Kellgren-Lawrence classification. Standardized imaging and interpretation are critical with radiographs, yet studies have also shown that even early stages of radiographic OA already demonstrate advanced damage to knee joint tissues such as cartilage, menisci, and bone marrow. Morphological magnetic resonance imaging (MRI) shows degenerative damage earlier than radiographs and definitions for OA using MRI have been published though no accepted definition of early OA based on MRI is currently available. The clinical significance of structural abnormalities has also not been well defined, and the differentiation between normal aging and structural OA development remains a challenge. Compositional MRI of cartilage provides information on biochemical, degenerative changes within the cartilage matrix before cartilage defects occur and when cartilage damage is potentially reversible. Studies have shown that cartilage composition can predict cartilage loss and radiographic OA. However, while this technology is most promising for characterizing early OA it has currently limited clinical application. Better standardization of compositional MRI is required, which is currently work in progress. Finally, there has been renewed interest in computed tomography (CT) for assessing early knee OA as new techniques such as weight bearing and spectral CT are available, which may provide information on joint loading, cartilage, and bone and potentially have a role in better characterizing early OA. In conclusion, while imaging may have a limited role in diagnosing early OA in a primary care setting, there are advanced imaging technologies available, which detect early degeneration and may thus significantly alter management as new therapeutic modalities evolve.

Multi-vendor multi-site quantitative MRI analysis of cartilage degeneration 10 Years after anterior cruciate ligament reconstruction: MOON-MRI protocol and preliminary results

OBJECTIVE

To describe the protocol of a multi-vendor, multi-site quantitative MRI study for knee post-traumatic osteoarthritis (PTOA), and to present preliminary results of cartilage degeneration using MR T1ρ and T2 imaging 10 years after anterior cruciate ligament reconstruction (ACLR).

DESIGN

This study involves three sites and two MR platforms. The patients are from a nested cohort (termed as Onsite cohort) within the Multicenter Orthopaedic Outcomes Network (MOON) cohort 10 years after ACLR. Phantoms and controls were scanned for evaluating reproducibility. Cartilage was automatically segmented, and T1ρ and T2 were compared between operated, contralateral, and control knees.

RESULTS

Sixty-eight ACL-reconstructed patients and 20 healthy controls were included. In phantoms, the intra-site coefficients of variation (CVs) of repeated scans ranged 1.8-2.1% for T1ρ and 1.3-1.7% for T2. The inter-site CVs ranged 1.6-2.1% for T1ρ and 1.1-1.4% for T2. In human subjects, the intra-site scan/rescan CVs ranged 2.2-3.5% for T1ρ and 2.6-4.9% for T2 for the six major compartments. In patients, operated knees showed significantly higher T1ρ and T2 values mainly in medial femoral condyle, medial tibia and trochlear cartilage compared with contralateral knees, and showed significantly higer T1ρ and T2 values in all six compartments compared to healthy control knees. The patient contralateral knees showed higher T1ρ and T2 values mainly in the lateral femoral condyle, lateral tibia, trochlear, and patellar cartilage compared to healthy control knees.

CONCLUSION

A platform and workflow with rigorous quality control has been established for a multi-vendor multi-site quantitative MRI study in evaluating PTOA 10 years after ACLR. Our preliminary report suggests significant cartilage matrix changes in both operated and contralateral knees compared with healthy control knees.

Efficient phase-cycling strategy for high-resolution 3D gradient-echo quantitative parameter mapping

Magnetization-prepared (MP) gradient-echo (GRE) sequences suffer from signal contaminations from T₁ recovery during the readout train, which can be eliminated by paired RF phase cycling (PC) at the cost of doubling the scan time. The objective of this study was to develop and validate a novel unpaired PC strategy to eliminate the time penalty for high-resolution quantitative parameter mapping in 3D MP-GRE sequences. Based on the observation that the contaminating T₁ recovery signal along the GRE readout train is independent of magnetization preparation, its impact can be eliminated using a novel curve-fitting approach with complex-valued data without needing paired PC acquisitions. Four new unpaired PC schemes were compared with two traditional paired PC schemes in both phantom and in vivo human knee studies at 3 T using a MP angle-modulated partitioned k-space spoiled gradient-echo snapshots (MAPSS) T_1ρ mapping sequence. In the phantom study, all methods resulted in consistent T_1ρ measurements (∆T_1ρ  < 0.5%) at the center slice when B₀ /B₁ values were uniform. Results were not consistent when off-center slices with nonideal B₀ /B₁ were included. Two unpaired PC schemes had comparable or significantly improved quantitative accuracy and scan-rescan reproducibility compared with the paired PC schemes. There was no significant T_1ρ quantitative variability increase or spatial fidelity loss using the new unpaired PC schemes. Unpaired PC schemes also had different T_1ρ spectral responses at different B₀ frequency offsets, which can potentially be exploited to reduce sensitivity to B₀ field inhomogeneities. The human knee study results were consistent with the phantom study findings. In conclusion, an unpaired PC strategy potentially allows more accurate quantitative parameter mapping with halved scan time compared with the paired PC approach to eliminate signal contaminations from T₁ recovery. It therefore offers additional flexibility in SNR optimization, spatial resolution improvement, and choice of imaging sampling points to obtain more accurate quantitative parameter mapping.

Elevated Patellofemoral and Tibiofemoral T1ρ Relaxation Times Following a First Time Patellar Dislocation

OBJECTIVE

The study was performed to evaluate cartilage within the knee following a first-time patellar dislocation, using elevated MRI-based T1ρ relaxation times as an indicator of low proteoglycan concentration. The hypothesis is that MRI-based T1ρ relaxation times for patellofemoral and tibiofemoral cartilage are significantly longer for knees being treated for patellar dislocation than for healthy control knees.

DESIGN

Twenty-one subjects being treated for a first-time, unilateral dislocation of the patella and 16 healthy controls participated in MRI-based T1ρ relaxation time mapping. Mean relaxation times were quantified for patellofemoral and tibiofemoral regions for injured knees, the contralateral knees, and healthy controls. T1ρ values for each region were compared between the 3 groups with generalized estimating equations. Linear regressions were also performed to correlate T1ρ relaxation times with time from injury.

RESULTS

The knees with a disloction had longer T1ρ relaxation times than the contralateral knees and control group at the medial patella and longer relaxation times than the control group at the lateral tibia (P < 0.05). T1ρ relaxation times at the medial patella also decreased with time from injury (r² = 0.21, P = 0.037).

CONCLUSIONS

Compositional changes to cartilage on the medial patella are related to traumatic impact during a dislocation. Potential exists for cartilage properties at the medial patella to improve with time. Cartilage degradation at the lateral tibia is not directly related to traumatic impact. The current baseline data are a starting point to characterize the pathway from a first-time dislocation to progressive cartilage degradation and osteoarthritis.

The relation between the biochemical composition of knee articular cartilage and quantitative MRI: a systematic review and meta-analysis

OBJECTIVE

Early and non-invasive detection of osteoarthritis (OA) is required to enable early treatment and monitoring of interventions. Some of the earliest signs of OA are the change in proteoglycan and collagen composition. The aim of this study is to establish the relations between quantitative magnetic resonance imaging (MRI) and biochemical concentration and organization in knee articular cartilage.

METHODS

A preregistered systematic literature review was performed using the databases PubMed and Embase. Papers were included if quantitative MRI and a biochemical assay or polarized light microscopy (PLM) was performed on knee articular cartilage, and a quantified correlation was described. The extracted correlations were pooled using a random effects model.

RESULTS

21 papers were identified. The strongest pooled correlation was found for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) vs proteoglycan concentration (r = 0.59). T1ρ relaxation times are inversely correlated to proteoglycan concentration (r = -0.54). A weak correlation between T2 relaxation times and proteoglycans was found (r = -0.38). No correlation between T2 relaxation time and collagen concentration was found (r = -0.02). A heterogeneous set of correlations between T2 relaxation times and PLM were identified, including strong correlations to anisotropy.

CONCLUSION

DGEMRIC measures are significantly correlated to proteoglycan concentration. The needed contrast agent is however a disadvantage; the T1ρ sequence was found as a non-invasive alternative. Remarkably, no correlation was found between T2 relaxation times and collagen concentration. T2 relaxation times is related to organization, rather than concentration of collagen fibers.

PROSPERO ID

CRD42020168337.

T2 MRI at 3T of cartilage and menisci in patients with hyperuricemia: initial findings

OBJECTIVE

To compare and evaluate T₂ values of compartmental femorotibial cartilage and subregional menisci in patients with hyperuricemia at 3T.

MATERIALS AND METHODS

Thirty-two subjects were included in this study and subdivided into two subgroups: 15 healthy controls (3 females, 12 males; mean age = 45.3 ± 10.9 years), 17 patients with hyperuricemia (2 females, 15 males; mean age = 44.4 ± 12.7 years). All subjects were assessed on a 3T MR scanner using an 8-channel phased-array knee coil (transmit-receive). Wilcoxon rank sum test and analysis of covariance (ANCOVA) were performed to determine whether there were any statistically significant differences in T₂ values of compartmental femorotibial cartilage and subregional menisci between the two subgroups.

RESULTS

Lateral tibial cartilage (48.6 ± 3.5 ms) in healthy subgroup had significantly lower (p < 0.05) T₂ values than all subcompartments of femorotibial cartilage in hyperuricemia subgroup. Medial tibial cartilage (56.5 ± 4.3 ms) in hyperuricemia subgroup had significantly higher (p < 0.05) T₂ values than all subcompartments of femorotibial cartilage except medial tibial cartilage in healthy subgroup. Medial anterior horn of meniscus (39.4 ± 2.9 ms) in healthy subgroup had significantly lower (p < 0.05) T₂ values than all subregional menisci except both medial anterior horn and medial body segment of meniscus in hyperuricemia subgroup.

CONCLUSION

T₂ values in certain compartmental femorotibial cartilage and subregional menisci in patients with hyperuricemia are evidently and abnormally heightened compared with those in healthy subjects, to which special attention should be paid when diagnosing and treating the patients with hyperuricemia in the clinical setting. The LT cartilage had significantly lower T₂ values (48.6 ± 3.5 ms) in healthy subgroup compared to all compartmental femorotibial cartilage in cohort with HU. MF cartilage had significantly lower T₂ values (51.6 ± 2.9 ms) in healthy subgroup compared to both LF (54.4 ± 4.1 ms) and MT (56.5 ± 4.3 ms) in cohort with HU. MT cartilage had significantly higher T₂ values (56.5 ± 4.3 ms) in cohort with HU subgroup compared to LF (52.5 ± 3.0 ms) in healthy subgroup. T₂ mapping may be promising and potential sensitive discriminator of understanding and examining the early compositional and structural change in proteoglycan-collagen matrix of human femorotibial cartilage in patients with hyperuricemia.

MOntelukast as a potential CHondroprotective treatment following Anterior cruciate ligament reconstruction (MOCHA Trial): study protocol for a double-blind, randomized, placebo-controlled clinical trial

BACKGROUND

After anterior cruciate ligament (ACL) reconstruction, patient-reported outcomes are improved 10 years post-surgery; however, cytokine concentrations remain elevated years after surgery with over 80% of those with combined ACL and meniscus injuries having posttraumatic osteoarthritis (PTOA) within 10-15 years. The purpose of this multicenter, randomized, placebo-controlled trial is to assess whether a 6-month course of oral montelukast after ACL reconstruction reduces systemic markers of inflammation and biochemical and imaging biomarkers of cartilage degradation.

METHODS

We will enroll 30 individuals undergoing primary ACL reconstruction to participate in this IRB-approved multicenter clinical trial. This trial will target those at greatest risk of a more rapid PTOA onset (age range 25-50 with concomitant meniscus injury). Patients will be randomly assigned to a group instructed to take 10 mg of montelukast daily for 6 months following ACL reconstruction or placebo. Patients will be assessed prior to surgery and 1, 6, and 12 months following surgery. To determine if montelukast alters systemic inflammation following surgery, we will compare systemic concentrations of prostaglandin E2, monocyte chemoattractant protein-1, and pro-inflammatory cytokines between groups. We will also compare degradative changes on magnetic resonance imaging (MRI) collected 1 and 12 months following surgery between groups with reductions in early biomarkers of cartilage degradation assessed with urinary biomarkers of type II collagen breakdown and bony remodeling.

DISCUSSION

There is a complex interplay between the pro-inflammatory intra-articular environment, underlying bone remodeling, and progressive cartilage degradation. PTOA affects multiple tissues and appears to be more similar to rheumatoid arthritis than osteoarthritis with respect to inflammation. There is currently no treatment to delay or prevent PTOA after ACL injury. Since there is a larger and more persistent inflammatory response after ACL reconstruction than the initial insult of injury, treatment may need to be initiated after surgery, sustained over a period of time, and target multiple mechanisms in order to successfully alter the disease process. This study will assess whether a 6-month postoperative course of oral montelukast affects multiple PTOA mechanisms. Because montelukast administration can be safely sustained for long durations and offers a low-cost treatment option, should it be proven effective in the current trial, these results can be immediately incorporated into clinical practice.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04572256 . Registered on October 1, 2020.

The QIBA Profile for MRI-based Compositional Imaging of Knee Cartilage

MRI-based cartilage compositional analysis shows biochemical and microstructural changes at early stages of osteoarthritis before changes become visible with structural MRI sequences and arthroscopy. This could help with early diagnosis, risk assessment, and treatment monitoring of osteoarthritis. Spin-lattice relaxation time constant in rotating frame (T1ρ) and T2 mapping are the MRI techniques best established for assessing cartilage composition. Only T2 mapping is currently commercially available, which is sensitive to water, collagen content, and orientation of collagen fibers, whereas T1ρ is more sensitive to proteoglycan content. Clinical application of cartilage compositional imaging is limited by high variability and suboptimal reproducibility of the biomarkers, which was the motivation for creating the Quantitative Imaging Biomarkers Alliance (QIBA) Profile for cartilage compositional imaging by the Musculoskeletal Biomarkers Committee of the QIBA. The profile aims at providing recommendations to improve reproducibility and to standardize cartilage compositional imaging. The QIBA Profile provides two complementary claims (summary statements of the technical performance of the quantitative imaging biomarkers that are being profiled) regarding the reproducibility of biomarkers. First, cartilage T1ρ and T2 values are measurable at 3.0-T MRI with a within-subject coefficient of variation of 4%-5%. Second, a measured increase or decrease in T1ρ and T2 of 14% or more indicates a minimum detectable change with 95% confidence. If only an increase in T1ρ and T2 values is expected (progressive cartilage degeneration), then an increase of 12% represents a minimum detectable change over time. The QIBA Profile provides recommendations for clinical researchers, clinicians, and industry scientists pertaining to image data acquisition, analysis, and interpretation and assessment procedures for T1ρ and T2 cartilage imaging and test-retest conformance. This special report aims to provide the rationale for the proposed claims, explain the content of the QIBA Profile, and highlight the future needs and developments for MRI-based cartilage compositional imaging for risk prediction, early diagnosis, and treatment monitoring of osteoarthritis.

An efficient R1ρ dispersion imaging method for human knee cartilage using constant magnetization prepared turbo-FLASH

This work aimed to develop an efficient R_1ρ dispersion imaging method for clinical studies of human knee cartilage at 3 T. Eight constant magnetizations (M_prep ) were prepared by tailoring both the duration and amplitude (ω₁ ) of a fully refocused spin-lock preparation pulse. The limited M_prep dynamic range was expanded by the measure, equivalent to that with ω₁  = ∞, from the magic angle location in the deep femoral cartilage. The developed protocol with M_prep  = 60% was demonstrated on one subject's bilateral and two subjects' unilateral asymptomatic knees. The repeatability of the proposed protocol was estimated by two repeated scans with a three-month gap for the last two subjects. The synthetic R_1ρ and R₂ derived from R_1ρ dispersions were compared with the published references using state-of-the-art R_1ρ and R₂ mapping (MAPSS). The proposed protocol demonstrated good (<5%) repeatability quantified by the intra- and intersubject coefficients of variation in the femoral and tibial cartilage. The synthetic R_1ρ (1/s) and the references were comparable in the femoral (23.0 ± 5.3 versus 24.1 ± 3.8, P = 0.67) and the tibial (29.1 ± 8.8 versus 27.1 ± 5.1, P = 0.62), but not the patellar (16.5 ± 4.9 versus 22.7 ± 1.6, P < 0.01) cartilage. The same trends were also observed for the current and the previous R₂ . In conclusion, the developed R_1ρ dispersion imaging scheme has been revealed to be not only efficient but also robust for clinical studies of human knee cartilage at 3 T.

T1rho mapping of cartilage and menisci in patients with hyperuricaemia at 3 T: a preliminary study

AIM

To compare and assess T_1rho values of the femorotibial cartilage compartments and subregional menisci in patients with hyperuricaemia at 3 T.

MATERIALS AND METHODS

Thirty-two patients were enrolled in the study and were subdivided into two subgroups: 15 healthy controls (three women, 12 men; mean age = 45.3 ± 10.9 years, age range 25-72 years) and 17 patients with asymptomatic hyperuricaemia (two women, 15 men; mean age = 44.4 ± 12.7 years, age range 26-77 years). All patients were evaluated using 3 T magnetic resonance imaging (MRI) using an eight-channel phased-array knee coil (transmit-receive). Wilcoxon's rank sum test and analysis of covariance (ANCOVA) were conducted to determine whether there were any statistically significant differences in the T_1rho values of the femorotibial cartilage compartments and subregional menisci between the two subgroups.

RESULTS

Lateral tibial cartilage (45.8 ± 2.9 ms) in the healthy subgroup had significantly lower (p<0.05) T_1rho values than those of all subcompartments of the femorotibial cartilage in the hyperuricaemia subgroup. The lateral femoral cartilage (LF) in hyperuricaemia (54.6 ± 3.9 ms) subgroup had significantly higher (p<0.05) T_1rho values than those of all subcompartments of the femorotibial cartilage except the LF in the healthy subgroup. Significantly higher (p<0.05) T_1rho values existed in the LF of the healthy (54.6 ± 4.7 ms) subgroup in comparison with those of all subcompartments of femorotibial cartilage except the LF in hyperuricaemia subgroup.

CONCLUSIONS

T_1rho values in certain compartments of the femorotibial cartilage in patients with hyperuricaemia are elevated compared to those in healthy patients presumably due to reduced proteoglycan content, to which particular attention should be paid when diagnosing and treating the patients with hyperuricaemia in a clinical setting.

Bone Structure Analysis of the Radius Using Ultrahigh Field (7T) MRI: Relevance of Technical Parameters and Comparison with 3T MRI and Radiography

Bone fractal signature analysis (FSA-also termed bone texture analysis) is a tool that assesses structural changes that may relate to clinical outcomes and functions. Our aim was to compare bone texture analysis of the distal radius in patients and volunteers using radiography and 3T and 7T magnetic resonance imaging (MRI)-a patient group (n = 25) and a volunteer group (n = 25) were included. Participants in the patient group had a history of chronic wrist pain with suspected or confirmed osteoarthritis and/or ligament instability. All participants had 3T and 7T MRI including T1-weighted turbo spin echo (TSE) sequences. The 7T MRI examination included an additional high-resolution (HR) T1 TSE sequence. Radiographs of the wrist were acquired for the patient group. When comparing patients and volunteers (unadjusted for gender and age), we found a statistically significant difference of horizontal and vertical fractal dimensions (FDs) using 7T T1 TSE-HR images in low-resolution mode (horizontal: p = 0.04, vertical: p = 0.01). When comparing radiography to the different MRI sequences, we found a statistically significant difference for low- and high-resolution horizontal FDs between radiography and 3T T1 TSE and 7T T1 TSE-HR. Vertical FDs were significantly different only between radiographs and 3T T1 TSE in the high-resolution mode; FSA measures obtained from 3T and 7T MRI are highly dependent on the sequence and reconstruction resolution used, and thus are not easily comparable between MRI systems and applied sequences.

Aggrecan, the Primary Weight-Bearing Cartilage Proteoglycan, Has Context-Dependent, Cell-Directive Properties in Embryonic Development and Neurogenesis: Aggrecan Glycan Side Chain Modifications Convey Interactive Biodiversity

This review examines aggrecan's roles in developmental embryonic tissues, in tissues undergoing morphogenetic transition and in mature weight-bearing tissues. Aggrecan is a remarkably versatile and capable proteoglycan (PG) with diverse tissue context-dependent functional attributes beyond its established role as a weight-bearing PG. The aggrecan core protein provides a template which can be variably decorated with a number of glycosaminoglycan (GAG) side chains including keratan sulphate (KS), human natural killer trisaccharide (HNK-1) and chondroitin sulphate (CS). These convey unique tissue-specific functional properties in water imbibition, space-filling, matrix stabilisation or embryonic cellular regulation. Aggrecan also interacts with morphogens and growth factors directing tissue morphogenesis, remodelling and metaplasia. HNK-1 aggrecan glycoforms direct neural crest cell migration in embryonic development and is neuroprotective in perineuronal nets in the brain. The ability of the aggrecan core protein to assemble CS and KS chains at high density equips cartilage aggrecan with its well-known water-imbibing and weight-bearing properties. The importance of specific arrangements of GAG chains on aggrecan in all its forms is also a primary morphogenetic functional determinant providing aggrecan with unique tissue context dependent regulatory properties. The versatility displayed by aggrecan in biodiverse contexts is a function of its GAG side chains.