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Femoroacetabular impingement (FAI) is a cause of hip pain and can lead to hip osteoarthritis. Radiological measurements obtained from radiographs or magnetic resonance imaging (MRI) are normally used for FAI diagnosis, but they require time‐consuming manual interaction, which limits accuracy and reproducibility. This study compares standard radiologic measurements against radiomics features automatically extracted from MRI for the identification of FAI patients versus healthy subjects. Three‐dimensional Dixon MRI of the pelvis were retrospectively collected for 10 patients with confirmed FAI and acquired for 10 healthy subjects. The femur and acetabulum were segmented bilaterally and associated radiomics features were extracted from the four MRI contrasts of the Dixon sequence (water‐only, fat‐only, in‐phase, and out‐of‐phase). A radiologist collected 21 radiological measurements typically used in FAI. The Gini importance was used to define 9 subsets with the most predictive radiomics features and one subset for the most diagnostically relevant radiological measurements. For each subset, 100 Random Forest machine learning models were trained with different data splits and fivefold cross‐validation to classify healthy subjects versus FAI patients. The average performance among the 100 models was computed for each subset and compared against the performance of the radiological measurements. One model trained using the radiomics features datasets yielded 100% accuracy in the detection of FAI, whereas all other radiomics features exceeded 80% accuracy. Radiological measurements yielded 74% accuracy, consistent with previous work. The results of this preliminary work highlight for the first time the potential of radiomics for fully automated FAI diagnosis. [ABSTRACT FROM AUTHOR]

Background: There is limited understanding of differences in the composition and structure of ligaments between healthy males and females, and individuals of different ages. Females present higher risk for ligament injuries than males and there are conflicting reports on its cause. This study looks into T1ρ parameters for an explanation as it relates to proteoglycan, collagen, and water content in these tissues. Purpose: To investigate gender‐related and age‐related differences in T1ρ parameters in knee joint ligaments in healthy volunteers using a T1ρ‐prepared zero echo‐time (ZTE)‐based pointwise‐encoding time‐reduction with radial acquisition (T1ρ‐PETRA) sequence. Study Type: Prospective. Population: The study group consisted of 22 healthy subjects (11 females, ages: 41 ± 18 years, and 11 males, ages: 41 ± 14 years) with no known inflammation, trauma, or pain in the knee joint. Field Strength/Sequence: A T1ρ‐prepared 3D‐PETRA sequence was used to acquire fat‐suppressed images with varying spin‐lock lengths (TSLs) of the knee joint at 3T. Assessment: Monoexponential, biexponential, and stretched‐exponential 3D‐PETRA‐T1ρ parameters were measured in the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and patellar tendon (PT) by manually drawing ROIs over the entirety of the tissues. Statistical Tests: Mann–Whitney U‐tests were used to compare 3D‐PETRA‐T1ρ parameters in the ACL, PCL, and PT between males and females. Spearman correlation coefficients were used to determine the association between age and T1ρ parameters. Statistical significance was defined as P < 0.05. Results: Significant correlations with age were found the three ligaments with most of the measured T1ρ parameters (rs = 0.28–0.74) with the exception of the short fraction in the PCL (P = 0.18), and the short relaxation time in the ACL (P = 0.58) and in the PCL (P = 0.14). Data Conclusion: 3D‐PETRA‐T1ρ can detect age‐related differences in monoexponential, biexponential, and stretched‐exponential T1ρ parameters in three ligaments of healthy volunteers, which are thought to be related to changes in tissue composition and structure during the aging process. Level of Evidence: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Background: Multiparameter characterization using MR fingerprinting (MRF) can quantify multiple relaxation parameters of intervertebral disc (IVD) simultaneously. These parameters may vary by age and sex. Purpose: To investigate age‐ and sex‐related differences in the relaxation parameters of the IVD of the lumbar spine using a multiparameter MRF technique. Study Type: Prospective. Subjects: 17 healthy subjects (8 male; mean age = 34 ± 10 years, range 20–60 years). Field Strength/Sequence: 3D‐MRF sequence for simultaneous acquisition of proton density, T1, T2, and T1ρ maps at 3.0T. Assessment: Global mean T1, T2, and T1ρ of all lumbar IVDs and mean T1, T2, and T1ρ of each individual IVD (L1–L5) were measured. Gray level co‐occurrence matrix was used to quantify textural features (median, contrast, correlation, energy, and homogeneity) from T1, T2, and T1ρ maps. Statistical Tests: Spearman rank correlations (R) evaluated the association between age and T1, T2, and T1ρ of IVD. Mann–Whitney U‐tests evaluated differences between males and females in T1, T2, and T1ρ of IVD. Statistical significance was defined as P‐value <0.05. Results: There was a significant negative correlation between age and global mean values of all IVDs for T1 (R = −0.637), T2 (R = −0.509), and T1ρ (R = −0.726). For individual IVDs, there was a significant negative correlation between age and mean T1 at all IVD segments (R range = −0.530 to −0.708), between age and mean T2 at L2‐L3, L3‐L4, and L4‐L5 (R range = −0.493 to 0.640), and between age and mean T1ρ at all segments except L1‐L2 (R range = −0.632 to −0.763). There were no significant differences between sexes in global mean T1, T2, and T1ρ (P‐value = 0.23–0.76) The texture features with the highest significant correlations with age for all IVDs were global T1ρ mean (R = −0.726), T1 energy (R = −0.681), and T1 contrast (R = 0.709). Conclusion: This study showed that the 3D‐MRF technique has potential to characterize age‐related differences in T1, T2, or T1ρ of IVD in healthy subjects. Level of Evidence: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

Currently no disease-modifying osteoarthritis drug has been approved for the treatment of osteoarthritis (OA) that can reverse, hold, or slow the progression of structural damage of OA-affected joints. The reasons for failure are manifold and include the heterogeneity of structural disease of the OA joint at trial inclusion, and the sensitivity of biomarkers used to measure a potential treatment effect. This article discusses the role and potential of different imaging biomarkers in OA research. We review the current role of radiography, as well as advances in quantitative three-dimensional morphological cartilage assessment and semiquantitative whole-organ assessment of OA. Although magnetic resonance imaging has evolved as the leading imaging method in OA research, recent developments in computed tomography are also discussed briefly. Finally, we address the experience from the Foundation for the National Institutes of Health Biomarker Consortium biomarker qualification study and the future role of artificial intelligence. [ABSTRACT FROM AUTHOR]

The objective of the current study was to investigate age‐ and gender‐related differences in lumbar intervertebral disk (IVD) strain with the use of static mechanical loading and continuous three‐dimensional (3D) golden‐angle radial sparse parallel (GRASP) MRI. A continuous 3D‐GRASP stack‐of‐stars trajectory of the lumbar spine was performed on a 3‐T scanner with static mechanical loading. Compressed sensing reconstruction, motion deformation maps, and Lagrangian strain maps during loading and recovery in the X‐, Y‐, and Z‐directions were calculated for segmented IVD segments from L1/L2 to L5/S1. Mean IVD height was measured at rest. Spearman coefficients were used to evaluate the associations between age and global IVD height and global IVD strain. Mann–Whitney tests were used to compare global IVD height and global IVD strain in males and females. The prospective study enrolled 20 healthy human volunteers (10 males, 10 females; age 34.6 ± 11.4 [mean ± SD], range 22–56 years). Significant increases in compressive strain were observed with age, as evidenced by negative correlations between age and global IVD strain during loading (ρ = −0.76, p = 0.0046) and recovery (ρ = −0.68, p = 0.0251) in the loading X‐direction. There was no significant correlation between age and global IVD height, global IVD strain during loading and recovery in the Y‐direction, and global IVD strain during loading and recovery in the Z‐direction. There were no significant differences between males and females in global IVD height and global IVD strain during loading and recovery in the X‐, Y‐, and Z‐directions. It was concluded that our study demonstrated the significant role aging plays in internal dynamic strains in the lumbar IVD during loading and recovery. Older healthy individuals have reduced IVD stiffness and greater IVD compression during static mechanical loading of the lumbar spine. The GRASP‐MRI technique demonstrates the feasibility to identify changes in IVD mechanical properties with early IVD degeneration due to aging. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance fingerprinting (MRF) techniques have been recently described for simultaneous multiparameter cartilage mapping of the knee although investigation of their ability to detect early cartilage degeneration remains limited. Purpose: To investigate age‐dependent changes in knee cartilage T1, T2, and T1p relaxation times measured using a three‐dimensional (3D) MRF sequence in healthy volunteers. Study Type: Prospective. Subjects: The study group consisted of 24 healthy asymptomatic human volunteers (15 males with mean age 34.9 ± 14.4 years and 9 females with mean age 44.5 ± 13.1 years). Field Strength/Sequence: A 3.0 T gradient‐echo‐based 3D‐MRF sequence was used to simultaneously create proton density‐weighted images and T1, T2, and T1p maps of knee cartilage. Assessment: Mean global cartilage and regional cartilage (lateral femur, lateral tibia, medial femur, medial tibia, and patella) T1, T2, and T1ρ relaxation times of the knee were measured. Statistical Tests: Kruskal–Wallis tests were used to compared cartilage T1, T2, and T1ρ relaxation times between different age groups, while Spearman correlation coefficients was used to determine the association between age and cartilage T1, T2, and T1ρ relaxation times. The value of P < 0.05 was considered statistically significant. Results: Higher age groups showed higher global and regional cartilage T1, T2, and T1ρ. There was a significant difference between age groups in global cartilage T2 and T1ρ but no significant difference (P = 0.13) in global cartilage T1. Significant difference was also present between age groups in cartilage T2 and T1ρ for medial femur cartilage and medial tibia cartilage. There were significant moderate correlations between age and T2 and T1ρ for global cartilage (R2 = 0.63–0.64), medial femur cartilage (R2 = 0.50–0.56), and medial tibia cartilage (R2 = 0.54–0.66). Conclusion: Cartilage T2 and T1p relaxation times simultaneously measured using a 3D‐MRF sequence in healthy volunteers showed age‐dependent changes in knee cartilage, primarily within the medial compartment. [ABSTRACT FROM AUTHOR]