Favian Su

Fully automatic analysis of the knee articular cartilage T1ρ relaxation time using voxel-based relaxometry.

To develop and compare with the classical region of interest (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 osteoarthritis (OA) and anterior cruciate ligament (ACL) subjects.

Abnormal tibial position is correlated to early degenerative changes one year following ACL reconstruction

Altered knee kinematics following ACL reconstruction may predispose patients to the development of early onset post‐traumatic osteoarthritis. The goal of our study was to examine the longitudinal interrelationship between altered tibial position relative to the femur and cartilage health measured by quantitative T1ρ MRI. Twenty‐five patients with isolated unilateral ACL injury underwent kinematic and cartilage T1ρ MRI at baseline prior to ACL reconstruction and then at 1‐year post‐reconstruction. Tibial position relative to the femur in the anterior–posterior plane was calculated as well as cartilage T1ρ relaxation values in the injured and uninjured knee. At baseline prior to ACL reconstruction, the tibia was in a significantly more anterior position relative to the femur in the ACL deficient knee compared to the healthy contralateral knee. This difference was no longer present at 1‐year follow‐up. Additionally, the side–side difference in tibial position correlated to increased cartilage T1ρ relaxation values in the medial compartment of the knee 1‐year post‐reconstruction. Altered tibial position following ACL reconstruction is correlated with detectable cartilage degeneration as soon as 1 year following ACL reconstruction.

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

OBJECTIVE To determine if cartilage T1ρ and T2 relaxation time measures after ACL injury and prior to reconstruction (baseline) are associated with patient-reported outcomes at baseline, 6-months, and 1-year after surgery. DESIGN Fifty-four ACL-injured participants were scanned in both knees at baseline using 3T MR T1ρ and T2 mapping. Participants also completed Knee-injury and Osteoarthritis Outcome Score (KOOS) and Marx activity level questionnaires at baseline, 6-months, and 1-year after reconstruction. The difference between cartilage T1ρ or T2 of the injured and contralateral knee (side-to-side difference, SSD) was calculated to account for physiological variations among patients. Linear regression models were built to evaluate the association between the baseline SSD T1ρ or T2 and KOOS or Marx at all time points. RESULTS Higher baseline SSD T1ρ posterolateral tibia (pLT) was associated with worse KOOS in all subscales except symptoms at baseline, worse KOOS pain at 6-months, and worse KOOS in all subscales except sports function at 1-year. Higher baseline SSD T2 femoral trochlea (TrF) was associated with worse KOOS activities of daily living (ADL) at 1-year. Higher baseline SSD T1ρ pLT was associated with lower Marx activity level at 1-year. More severe cartilage lesions, as assessed by Whole-Organ MRI Scoring (WORMS), was significantly associated with worse KOOS pain at 6-months and 1-year. CONCLUSION T1ρ and T2 of cartilage after ACL injury were associated with KOOS after injury and both KOOS and Marx after reconstruction. Such associations may help clinicians stratify outcomes post-injury, and thus, improve patient management.

Analysis of the articular cartilage T1ρ and T2 relaxation times changes after ACL reconstruction in injured and contralateral knees and relationships with bone shape

The objectives of this study were twofold: (1) to evaluate the longitudinal change in cartilage T1ρ and T2 6‐ and 12‐months after ACL reconstruction (ACLR) in both reconstructed and intact contralateral knees with the aim of validating the role of the contralateral knee as an internal control in longitudinal studies; (2) to explore relationships between bone shape at the time of injury and the progression of T1ρ and T2 over 12‐months after ACLR. T1ρ and T2 cartilage relaxation times and 3D MRI‐based statistical shape modeling (SSM) of tibia and femur were computed for both knees of forty ACL‐injured patients and 15 healthy controls. ACL subjects were scanned 8.4 ± 6.4 weeks after injury (2.4 ± 3.7 weeks prior to ACLR), 6‐ and 12‐months after ACLR. Longitudinal changes in T1ρ and T2 values were assessed using linear mixed model, and partial correlation coefficients were calculated between bone shape and longitudinal changes in T1ρ and T2 values. Significant longitudinal increases in T1ρ and T2 values were observed in reconstructed and contralateral knees 6‐months after ACLR. Tibial bone shape features, associated with the medial plateau height and width, were observed to be correlated with cartilage T1ρ and T2 progression in reconstructed knees. Our results suggest that caution should be used in considering contralateral knee as internal controls in longitudinal ACL studies and 3D MRI‐based‐SSM might serve as an imaging biomarker for the early stratification of patients at risk for developing post‐traumatic accelerated cartilage degeneration and potentially osteoarthritis after ACL tear.

MR T1ρ quantification of cartilage focal lesions in acutely injured knees: correlation with arthroscopic evaluation

OBJECTIVE Quantitative T1ρ MRI has been suggested as a promising tool to detect changes in cartilage composition that are characteristic of cartilage damage and degeneration. The objective of this study was to evaluate the capability of MR T1ρ to detect cartilage lesions as evaluated by arthroscopy in acutely ACL-injured knees and to compare with the Whole-Organ Magnetic Resonance Imaging Score (WORMS) using clinical standard MRI. METHOD Ten healthy controls (mean age 35) with no ACL injury or history of osteoarthritis (OA) and 10 patients with acute ACL injuries (mean age 39) were scanned at 3 Tesla (3T). ACL patients underwent ACL reconstruction, where focal lesions were graded according to an Outerbridge grading system during arthroscopic evaluation. Normalized MR T1ρ values (T1ρ z-scores normalized to control values in matched regions) in full thickness, and superficial and deep layers of cartilage were compared between defined sub-compartments with and without focal lesions. Intraclass (ICC) correlation and the root mean square coefficient of variation (RMS-CV) were performed to evaluate the inter-observer reproducibility of T1ρ quantification. Sub-compartments of cartilage were also evaluated using WORMS scoring and compared to their Outerbridge score respectively. RESULTS The inter-observer ICC and the RMS-CV of the sub-compartment T1ρ quantification were 0.961 and 3.9%, respectively. The average T1ρ z-scores were significantly increased in sub-compartments with focal lesions compared to those without focal lesions and to the control cohort (p<0.05). CONCLUSION Our results indicate that T1ρ provided a better diagnostic capability than clinical standard MRI grading in detecting focal cartilage abnormalities after acute injuries. Quantitative MRI may have great potential in detecting cartilage abnormalities and degeneration non-invasively, which are occult with standard morphological MRI.

High-temporospatial-resolution dynamic contrast-enhanced (DCE) wrist MRI with variable-density pseudo-random circular Cartesian undersampling (CIRCUS) acquisition: evaluation of perfusion in rheumatoid arthritis patients

This study is to evaluate highly accelerated three‐dimensional (3D) dynamic contrast‐enhanced (DCE) wrist MRI for assessment of perfusion in rheumatoid arthritis (RA) patients. A pseudo‐random variable‐density undersampling strategy, circular Cartesian undersampling (CIRCUS), was combined with k–t SPARSE‐SENSE reconstruction to achieve a highly accelerated 3D DCE wrist MRI. Two healthy volunteers and 10 RA patients were studied. Two patients were on methotrexate (MTX) only (Group I) and the other eight were treated with a combination therapy of MTX and anti‐tumor necrosis factor (TNF) therapy (Group II). Patients were scanned at baseline and 3 month follow‐up. DCE MR images were used to evaluate perfusion in synovitis and bone marrow edema pattern in the RA wrist joints. A series of perfusion parameters was derived and compared with clinical disease activity scores of 28 joints (DAS28). 3D DCE wrist MR images were obtained with a spatial resolution of 0.3 × 0.3 × 1.5 mm3 and temporal resolution of 5 s (with an acceleration factor of 20). The derived perfusion parameters, most notably transition time (dT) of synovitis, showed significant negative correlations with DAS28‐ESR (r = −0.80, p < 0.05) and DAS28‐CRP (r = −0.87, p < 0.05) at baseline and also correlated significantly with treatment responses evaluated by clinical score changes between baseline and 3 month follow‐up (with DAS28‐ESR r = −0.79, p < 0.05, and DAS28‐CRP r = −0.82, p < 0.05). Highly accelerated 3D DCE wrist MRI with improved temporospatial resolution has been achieved in RA patients and provides accurate assessment of neovascularization and perfusion in RA joints, showing promise as a potential tool for evaluating treatment responses. Copyright

Persistent Biomechanical Alterations After ACL Reconstruction Are Associated With Early Cartilage Matrix Changes Detected by Quantitative MR

Background: The effectiveness of anterior cruciate ligament (ACL) reconstruction in preventing early osteoarthritis is debated. Restoring the original biomechanics may potentially prevent degeneration, but apparent pathomechanisms have yet to be described. Newer quantitative magnetic resonance (qMR) imaging techniques, specifically T1ρ and T2, offer novel, noninvasive methods of visualizing and quantifying early cartilage degeneration. Purpose: To determine the tibiofemoral biomechanical alterations before and after ACL reconstruction using magnetic resonance imaging (MRI) and to evaluate the association between biomechanics and cartilage degeneration using T1ρ and T2. Study Design: Cohort study; Level of evidence, 2. Methods: Knee MRIs of 51 individuals (mean age, 29.5 ± 8.4 years) with unilateral ACL injuries were obtained prior to surgery; 19 control subjects (mean age, 30.7 ± 5.3 years) were also scanned. Follow-up MRIs were obtained at 6 months and 1 year. Tibial position (TP), internal tibial rotation (ITR), and T1ρ and T2 were calculated using an in-house Matlab program. Student t tests, repeated measures, and regression models were used to compare differences between injured and uninjured sides, observe longitudinal changes, and evaluate correlations between TP, ITR, and T1ρ and T2. Results: TP was significantly more anterior on the injured side at all time points (P < .001). ITR was significantly increased on the injured side prior to surgery (P = .033). At 1 year, a more anterior TP was associated with elevated T1ρ (P = .002) and T2 (P = .026) in the posterolateral tibia and with decreased T2 in the central lateral femur (P = .048); ITR was associated with increased T1ρ in the posteromedial femur (P = .009). ITR at 6 months was associated with increased T1ρ at 1 year in the posteromedial tibia (P = .029). Conclusion: Persistent biomechanical alterations after ACL reconstruction are related to significant changes in cartilage T1ρ and T2 at 1 year postreconstruction. Longitudinal correlations between ITR and T1ρ suggest that these alterations may be indicative of future cartilage injury, leading to degeneration and osteoarthritis. Clinical Relevance: Newer surgical techniques should be developed to eliminate the persistent anterior tibial translation commonly seen after ACL reconstruction. qMR will be a useful tool to evaluate the ability of these newer techniques to prevent cartilage changes.

Gait Characteristics Associated With a Greater Increase in Medial Knee Cartilage T1ρ and T2 Relaxation Times in Patients Undergoing Anterior Cruciate Ligament Reconstruction

Background: Osteoarthritis of the medial tibiofemoral joint (MTFJ) is prevalent among patients undergoing anterior cruciate ligament reconstruction (ACLR). Magnetic resonance T1ρ and T2 relaxation times provide noninvasive methods to quantify early cartilage degeneration. Altered sagittal-plane gait biomechanics have been observed after ACLR, but their associations with longitudinal changes in MTFJ cartilage T1ρ and T2 remain unclear. Hypothesis/Purpose: To examine whether the peak knee flexion moment (KFM), knee flexion angle (KFA), and vertical ground-reaction force (vGRF) during gait are associated with prospective changes in medial tibiofemoral cartilage T1ρ and T2 in ACL-reconstructed knees and to compare these gait characteristics between patients undergoing ACLR and healthy control participants. We hypothesized that a higher KFM, KFA, and vGRF would be associated with greater increases in cartilage relaxation times and that patients undergoing ACLR would demonstrate altered gait characteristics compared with healthy controls. Study Design: Controlled laboratory study. Methods: Thirty-three patients undergoing ACLR underwent gait analysis before and 6 months and 1 year after ACLR and knee magnetic resonance imaging (MRI) before and 6 months, 1 year, and 2 years after ACLR. Twelve healthy controls underwent knee MRI and gait analysis at baseline and 1 year. Cartilage T1ρ and T2 were calculated for the medial tibia and medial femoral condyle. Linear regressions were used to evaluate associations between gait characteristics and changes in cartilage relaxation times from before ACLR to follow-up time points. Independent t tests were used to compare differences in gait between patients undergoing ACLR and control participants. Results: A higher KFM and KFA before ACLR were related to greater increases in medial femoral condyle T1ρ and T2 at 6 months after ACLR. Similarly, a higher KFM, KFA, and vGRF at 6 months were associated with greater increases in medial tibia and medial femoral condyle T1ρ and T2 at 1 and 2 years after ACLR. Gait characteristics at 1 year were not associated with changes in cartilage relaxation times at 2 years after ACLR. Compared with healthy controls, patients undergoing ACLR demonstrated a lower KFM at 6 months after ACLR. Conclusion/Clinical Relevance: The findings of this study revealed that a higher KFM, KFA, and vGRF during gait, especially at 6 months after ACLR, were associated with greater deterioration of MTFJ cartilage health at later time points.

Frontal Plane Knee Mechanics and Early Cartilage Degeneration in People With Anterior Cruciate Ligament Reconstruction: A Longitudinal Study

Background: Abnormal frontal plane gait mechanics are known risk factors for knee osteoarthritis, but their role in early cartilage degeneration after anterior cruciate ligament reconstruction (ACLR) is not well understood. Hypothesis/Purpose: The objective was to evaluate the association of frontal plane gait mechanics with medial knee cartilage magnetic resonance (MR) relaxation times over 1 year in patients with ACLR and controls. It was hypothesized that (1) there will be an increase in frontal plane medial knee loading and medial knee MR relaxation times over time in the patients with ACLR, and (2) increases in frontal plane medial knee loading will be associated with an increase in medial knee MR relaxation times. Study Design: Case-control study; Level of evidence, 3. Methods: Patients with ACLR (n = 37) underwent walking gait analyses and bilateral quantitative MR imaging (MRI) before surgery and at 6 and 12 months after ACLR. Healthy control participants (n = 13) were evaluated at baseline and 12 months. Gait variables included peak knee adduction moment (KAM), KAM impulse, and peak knee adduction angle. MRI variables included medial femur and medial tibia whole compartment and subregional T1ρ and T2 relaxation times. Statistical analyses included a comparison of changes over time for gait and MRI variables, correlations between changes in gait and MRI variables over time, and differences in change in MRI variables in patients who showed an increase versus decrease in KAM impulse. Results: There were significant increases in medial T1ρ (Δ 4%-11%) and T2 (Δ 2%-10%) relaxation times from baseline to 6 months for both knees in the ACLR group and in KAM (Δ 13%) for the injured knee. From baseline to 6 months, patients who had an increase in KAM impulse in the injured knee had a greater increase in medial T1ρ and T2 relaxation times as compared with those who did not have an increase in KAM impulse. Longitudinal changes for the control group were not significant. Conclusion: There is an increase in medial knee relaxation times over the first 6 months after ACLR. People with an increase in medial knee loading show an increase in medial knee relaxation times when compared with those who do not have an increase in medial knee loading over the first 6 months.