Cory Wyatt

Simultaneous acquisition of T1ρ and T2 quantification in knee cartilage: repeatability and diurnal variation.

To develop a robust sequence that combines T1ρ and T2 quantifications and to examine the in vivo repeatability and diurnal variation of T1ρ and T2 quantifications in knee cartilage.

Scoring Hip Osteoarthritis with MRI (SHOMRI): a Whole Joint Osteoarthritis Evaluation System

To develop a semi‐quantitative MR‐based hip osteoarthritis (OA) evaluation system (Scoring hip osteoarthritis with MRI, SHOMRI), and to test its reproducibility and face validity.

Anatomic correlates of reduced hip extension during walking in individuals with mild-moderate radiographic hip osteoarthritis

To identify radiographic and MR features of hip osteoarthritis (OA) related to reduced hip extension during walking. Sixty six subjects, were stratified into those with (n = 36, KL = 2, 3) and without (n = 30, KL = 0, 1) radiographic hip OA. Cartilage and labrum lesions were graded semi‐quantitatively on hip MRI. Alpha angle and lateral center edge (LCE) angle were measured. Sagittal kinematics and kinetics were calculated during walking at speed of 1.35 m/s using 3‐D motion capture. All subjects completed Hip disability and Osteoarthritis Outcome Score (HOOS), timed up and go, and 6 min walk tests. Variables were compared between the two groups using one‐way ANOVA (adjusting for age). Correlations of radiographic and MR parameters with peak hip extension were calculated. The OA group was older, had greater pain, and limitation of function. They also had lower peak hip extension and higher peak hip flexion; and worse acetabular and femoral cartilage lesions. Peak hip extension and flexion correlated with KL grade, cartilage lesions in the inferior and posterior femur. Reduced hip extension and greater hip flexion during walking are present in high functioning (HOOS > 85%) individuals with mild‐moderate hip OA, and are associated with cartilage lesions.

Validation of bone marrow fat quantification in the presence of trabecular bone using MRI

To validate six‐echo, chemical‐shift based MRI with T2* correction for the quantification of bone marrow fat content in the presence of trabecular bone.

T1ρ and T2 relaxation times are associated with progression of hip osteoarthritis

OBJECTIVE To evaluate whether baseline T1ρ and T2 relaxation times of hip cartilage are associated with magnetic resonance imaging (MRI) based progression of hip osteoarthritis (OA) at 18 months. METHODS 3T MRI studies of the hip were obtained at baseline and 18-month follow-up for 54 subjects without evidence of severe OA at baseline [Kellgren-Lawrence (KL) score of 0-3]. 2D fast spin-echo sequences were used for semi-quantitative morphological scoring of cartilage lesions and a combined T1ρ/T2 sequence was used to quantitatively assess cartilage composition. Progression of hip OA was defined based on incident or progression of morphological semi-quantitative grade at 18 months. Baseline T1ρ and T2 relaxation times were compared between progressors and non-progressors using one-way analysis of variance and Mann-Whitney U tests and used to predict progression with binary logistic regression after adjusting for age, gender, body mass index, and KL score. Additionally, a novel voxel-based relaxometry technique was used to compare the spatial distribution of baseline T1ρ and T2 between progressors and non-progressors. RESULTS Significantly higher baseline T1ρ and T2 values were observed in hip OA progressors compared to non-progressors, particularly in the posterosuperior and anterior aspects of the femoral cartilage. Logistic regression showed that higher baseline T1ρ or T2 values in the femoral cartilage were significantly associated with progression of femoral cartilage lesions at 18 months. CONCLUSION T1ρ and T2 relaxation parameters are associated with morphological cartilage degeneration at 18 months and may serve as potential imaging biomarkers for progression of cartilage lesions in hip OA.

Cartilage T1ρ and T2 Relaxation Times in Patients With Mild-to-Moderate Radiographic Hip Osteoarthritis

To analyze region‐specific T1ρ and T2 relaxation times of the hip joint cartilage in relation to presence or absence of radiographic hip osteoarthritis (OA) and presence or absence of magnetic resonance imaging (MRI)–detected cartilage defects.

Spatial variations in magnetic resonance-based diffusion of articular cartilage in knee osteoarthritis

PURPOSE To evaluate a pulse sequence combining stimulated echo diffusion preparation with a 3D segmented spoiled gradient echo (SPGR) acquisition for diffusion tensor imaging (DTI) of knee cartilage in healthy and osteoarthritis (OA) populations for early diagnosis and characterization of OA. METHODS Diffusion-weighted images of 40 subjects (20 healthy, 20 OA) at baseline and 20 subjects (10 healthy, 10 OA) at one year were obtained. The subjects were classified according to Kellgren Lawrence (KL) and whole organ magnetic resonance imaging scoring (WORMS) method acquired at 3 T. Cartilage full thickness and laminar mean diffusivity (MD) and fractional anisotropy (FA) values were quantified. The reproducibility of MD and FA values was assessed in five healthy human subjects based on test-retest scans. RESULTS In general, the full thickness MD values were higher in subjects with knee OA compared to healthy controls in both the baseline and follow up cohort. Laminar analysis MD and FA results were significantly different (p<0.05) between the bone-articular and articular layer with the articular layer having higher MD and lower FA value compared to the bone layer. The global reproducibility error was 6.5% for MD and 11.6% for FA. CONCLUSION The diffusion-weighted stimulated echo-based sequence may be used as a valuable tool for early diagnosis and characterization of knee OA at 3 T in the future.

Improved differentiation between knees with cartilage lesions and controls using 7T relaxation time mapping

Summary Background/Objective T1ρ and T2 relaxation mapping in knee cartilage have been used extensively at 3 Tesla (T) as markers for proteoglycan and collagen, respectively. The objective of this study was to evaluate the feasibility of T1ρ and T2 imaging of knee cartilage at 7T in comparison to 3T and to evaluate the ability of T1ρ and T2 to determine differences between normal and osteoarthritis (OA) patients. Materials and methods Twenty patients, seven healthy patients (Kellgren–Lawrence = 0), and 13 patients with signs of radiographic OA (Kellgren–Lawrence > 0) were scanned at 3T and 7T. The knee cartilage was segmented into six compartments and the T1ρ and T2 values were fit using a two-parameter model. Additionally, patients were stratified by the presence of cartilage lesions using the modified Whole Organ Magnetic Resonance Imaging Score classification of the knee. One-way analysis of variance was used to compare the healthy and OA groups at 3T and 7T. The specific absorption ratio was kept under Food and Drug Administration limits during all scans. Results T1ρ and T2 values at 3T and 7T were significantly higher in the lateral femoral condyle and patella in patients with OA. However, more regions were significant or approached significance at 7T compared with 3T, with the differences between healthy and OA patients also larger at 7T. The signal to noise ratio across all cartilage and meniscus compartments was 60% higher on average at 7T compared to 3T. Conclusion T1ρ imaging at 7T has been established as a viable imaging method for the differentiation of degenerated cartilage despite previous concerns over specific absorption rate and imaging time. The potential increased sensitivity of T1ρ and T2 imaging at 7T may be useful for future studies in the development of OA.

Multi-parametric T 2* magnetic resonance fingerprinting using variable echo times

The use of quantitative imaging biomarkers in the imaging of various disease states, including cancer and neurodegenerative disease, has increased in recent years. T1, T2, and T2* relaxation time constants have been shown to be affected by tissue structure or contrast infusion. Acquiring these biomarkers simultaneously in a multi‐parametric acquisition could provide more robust detection of tissue changes in various disease states including neurodegeneration and cancer. Traditional magnetic resonance fingerprinting (MRF) has been shown to provide quick, quantitative mapping of T1 and T2 relaxation time constants. In this study, T2* relaxation is added to the MRF framework using variable echo times (TE).

Sagittal plane walking patterns are related to MRI changes over 18-months in people with and without mild-moderate hip osteoarthritis†

The purpose was to evaluate the association of sagittal plane gait mechanics with MRI changes in the hip joint over 18‐months. Subjects with and without radiographic hip OA (n = 57) underwent MRI at baseline and 18 months for grading of cartilage lesions, bone marrow lesions (BML), cysts, and labral tears. 3D gait analyses at baseline were used for sagittal plane hip kinematics and kinetics during the stance phase. Subjects were classified as progressors or non‐progressors based on increase in any MRI OA parameter. Multivariate ANOVA were used for differences in sagittal gait parameters between progressors and non‐progressors at baseline while adjusting for age. Logistic regression was used to estimate the probability of being classified as a progressor or non‐progressor with increasing hip flexion while adjusting for age, BMI, sex, and presence of radiographic hip OA. Of the 57, 35 were classified as non‐progressors and 22 were classified as progressors. At baseline, the progressors walked with 4.5° greater hip flexion during early stance (p = 0.021) and 3.5° lesser hip extension in late stance that was nearly significant (p = 0.059). Walking with greater hip flexion at baseline was associated with a greater risk of increase in MRI defined structural changes in the hip joint (Odds Ratio = 1.1, p = 0.038). Greater hip flexion during walking was associated with a risk of structural progression of hip OA. The results may guide future interventions to alter the walking patterns and slow structural hip OA progression.© 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1472–1477, 2018.