Koren Roach¹, Valentina Pedoia¹, Jinhee J Lee¹, Tijana Popovic¹, Sharmila Majumdar¹, and Richard B Souza^1
1UCSF, San Francisco, CA, United States

Hip osteoarthritis is likely caused by changes in gait biomechanics and cartilage biochemistry and composition. In this study, we employed multivariate functional principal component analysis to identify gait waveform characteristics that were related to T_1ρ and T₂ relaxation times in the femoral and acetabular cartilage. Our results indicated that transverse and sagittal plane waveform characteristics are significantly related to T_1ρ and T₂ relaxation times in the femoral and acetabular cartilage and may be key planes of motion on which to focus preventative therapies for hip osteoarthritis.

David B Berry¹, Erin K Englund², Vitaly Galinsky³, Lawrence R Frank³, and Samuel R Ward^2,3,4
1Nanoengineering, University of California, San Diego, La Jolla, CA, United States, ²Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States, ³Radiology, University of California, San Diego, La Jolla, CA, United States, ⁴Bioengineering, University of California, San Diego, La Jolla, CA, United States

There is growing interest in using the Random Permeable Barrier Model (RPBM) to measure muscle microstructure. The goal of this study was to evaluate the accuracy of RPBM in predicting muscle fiber size in histology informed models of healthy and injured skeletal muscle from simulated DTI data. RPBM was found to systematically underestimate fiber size, but accurately predicted surface area to volume ratio (S/V) of the simulated muscle fibers. While the clinical interpretation of S/V ratio is unclear, this indicates that accurate measurement of S/V may serve as a proxy to changes in muscle fiber size and therefore function.

Claudia Iriondo¹, Alaleh Razmjoo², Francesco Caliva², Sharmila Majumdar², and Valentina Pedoia^2
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²University of California, San Francisco, San Francisco, CA, United States

To-the-point (TTP) is a novel approach for analyzing compositional MR imaging data. By representing tibial and femoral cartilage T2 values as a dense point cloud, our approach can leverage the data's inherent sparsity while maintaining local geometric properties, leading to improved feature extraction and faster image processing times. Experiments on the whole OAI T2 dataset show strong performance in an OA diagnosis task 82.44% sens, 82.59% spec, with extracted features even identifying patients who would become diagnosed with OA 1 to 2 years in the future.

Rajiv G Menon¹, Marcelo V. W. Zibetti¹, and Ravinder R Regatte^1
1Center for Biomedical Imaging, Department of Radiology, New York University Langone Health, New York, NY, United States

The goal of this study was to develop a non-invasive MRI technique to measure 3D dynamic internal strains in the intervertebral discs (IVDs) of lumbar spine during loading and recovery phases. For this purpose, a combination of static mechanical loading of the IVD using MR-compatible ergometer and continuous  MRI-acquisition with a 3D-GRASP acquisition was used. Data was acquired on five healthy volunteers, and dynamic strains under loading and recovery conditions were calculated in 5-IVD segments from L1/L2 to L5/S1. By measuring temporal evolution of strain during rest, loading and recovery phases, dynamic strain information in the IVD may be investigated.

Deva D. Chan^1,2, Paull C. Gossett², Robert L. Wilson³, Woong Kim², Yue Mei^4,5,6, Kent Butz², Nancy Emery⁷, Eric A. Nauman², Stéphane Avril⁶, and Corey P. Neu^2,3
1Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, United States, ²Biomedical Engineering, Purdue University, West Lafayette, IN, United States, ³Mechanical Engineering, University of Colorado Boulder, Boulder, CO, United States, ⁴Engineering Mechanics, Dalian University of Technology, Dalian, China, ⁵International Research Center for Computational Mechanics, Dalian University of Technology, Dalian, China, ⁶Center for Biomedical and Healthcare Engineering, MINES Saint-Étienne, Saint-Étienne, France, ⁷Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, United States

IVD degeneration is the most recognized cause of low back pain, characterized by the decline of tissue structure and mechanics. MRI relaxometry is one quantitative measure of IVD degeneration, yet MRI metrics of mechanics have not been fully explored. We quantified patterns of IVD strain and mechanics during physiological compression and bending. Strains patterns depended on the loading mode, and shear modulus in the nucleus pulposus was typically an order of magnitude lower than the annulus fibrosis, except in bending, where the apparent stiffness depended on the loading direction. Strain and material properties provide new possible biomarkers for IVD degeneration.

Benjamin Marty^1,2, Teresa Gerhalter^1,2,3, Lena V. Gast³, Katharina Porzelt⁴, Matthias Türk⁴, Matthias Hammon³, Michael Uder³, Rolf Schröder⁵, Pierre G. Carlier^1,2, and Armin M. Nagel^3,6,7
1NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology, Paris, France, ²NMR Laboratory, CEA/DRF/IBFJ/MIRCen, Paris, France, ³Institute of Radiology, University Hospital, FAU, Erlangen, Germany, ⁴Institute of Neurology, FAU, Erlangen, Germany, ⁵Department of Neuropathology, University Hospital Erlangen, FAU, Erlangen, Germany, ⁶Division of Medical Physics in Radiology, DKFZ, Heidelberg, Germany, ⁷Institute of Medical Physics, FAU, Erlangen, Germany

Facioscapulohumeral muscular dystrophy (FSHD) is a neuromuscular disorder characterized by structural changes affecting skeletal muscle tissues, resulting in muscle wasting and dysfunction. Here, we determined the value of quantitative ¹H and ²³Na muscle MRI approaches for providing variables related to disease severity (fat fraction) and disease activity (water T2, water T1, total sodium content and inversion-recovery ²³Na) in patients with FSHD. We found that MRI variables related to water mobility and ion homeostasis were increased at an early stage of the degeneration process in several muscles of FSHD patients and represent potential candidates for assessing treatment response in clinical trials.

Harmen Reyngoudt^1,2, Ericky Caldas de Almeida Araujo^1,2, Pierre-Yves Baudin³, Benjamin Marty^1,2, and Pierre G. Carlier^1,2
1NMR Laboratory, Neuromuscular Investigation Center, Institute of Myology, Paris, France, ²NMR Laboratory, CEA/DRF/IBFJ/MIRCen, Paris, France, ³Consultants for Research in Imaging and Spectroscopy, Tournai, Belgium

¹H NMRS-based water T₂ (T_2w) has shown to be decreasing when muscle fat fraction levels are elevated (>60%). Here, two myopathy patient groups with similar fat fraction levels (>60%) emerged, being a group with T_2w>30 ms and a group with T_2w<30 ms, which seemed to be correlated to the respective water resonance linewidths. Interpretation of these reduced T_2w values at high fat fractions needs to be handled cautiously. The larger linewidths observed in the spectra characterized by shorter T_2w may be due to the local B₀ gradients induced by susceptibility differences between muscle and fat.

Daehyun Yoon¹, Neha Antil¹, Sandip Biswal¹, and Amelie Lutz^1
1Radiology, Stanford university, Stanford, CA, United States

The conventional MRI examination of brachial plexus using 2D fast spin-echo sequences suffers from 1) long scan time due to a large field of view, 2) insufficient fat suppression due to strong off-resonance, 3) confusion between nerves and blood vessels. We recently presented a novel MSDE-CUBE-FLEX sequence addressing these issues by combining 1) outer volume suppression, 2) fast triple-echo Dixon technique, 3) magnitude-preparation to suppress blood signal. In this work, we compared the MSDE-CUBE-FLEX and 2D FSE sequences for imaging brachial plexus, which shows clear improvements in brachial plexus visualization with the MSDE-CUBE-FLEX sequence. 

Valentina Mazzoli¹, Kevin Moulin¹, Feliks Kogan¹, Brian Hargreaves¹, and Garry E. Gold^1
1Department of Radiology, Stanford University, Stanford, CA, United States

The apparent diffusion coefficient measured using DTI in skeletal muscles depends on the time allowed for diffusing water molecules to probe the local environment and on the size of muscle cells. Here we explore the use of Oscillating Gradient Spin Echo diffusion to obtain information on skeletal muscle microstructure over smaller distances than conventionally probed using PGSE. Our results show the ability to image skeletal muscle during active contraction (foot dorsiflexion and plantarflexion) using OGSE, and diffusion values are dependent on the oscillation frequency and on the contraction status of the muscle

Marco Barbieri¹, Paola Fantazzini¹, Anna Festa², Fabio Baruffaldi², Claudia Testa¹, and Leonardo Brizi^1
1Physics and Astronomy, University of Bologna, Bologna, Italy, ²IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy

Methods to improve the early detection of diseases associated with an increased bone fragility are objects of investigation. Single-sided NMR is an appealing approach for medical applications. In this work we propose a new methodology to assess the bone volume fraction (BV/TV) of trabecular bone (TB), without the need of using a reference sample, exploiting the separation between intra- and inter-trabecular ¹H signals from quasi-continuous T₂ distributions. BV/TV of TB samples estimated using NMR were found in strong agreement with micro-CT estimations. This is promising for the application of single-sided NMR scanners to in-vivo assessing of bone micro-structure.

Zhenyu Cai^1,2, Zhao Wei², Mingxin Chen², Saeed Jerban², Hyungseok Jang², Eric Chang^2,3, Jiang Du², and Yajun Ma^2
1Radiology, Fuwai Hospital Chinese Academy of Medical Sciences, Shenzhen, shenzhen, China, ²Radiology, University of California San Diego, San Diego, CA, United States, ³VA San Diego Healthcare System, San Diego, CA, United States

The osteochondral junction (OCJ) is the region where calcified cartilage meets subchondral bone (SCB), and is likely to be highly related to osteoarthritis (OA). However, it is difficult to image OCJ tissues due to their relatively short transverse relaxation times, which cause little or no signal to appear with conventional imaging sequences. In this study, we developed a 3D T1-weighed fast ultrashort echo time cones sequence with fat saturation (FS-UTE-Cones) to generate a high OCJ contrast image of the human knee on a clinical 3T MRI scanner.

Yanping Xue^1,2, Yajun Ma¹, Zhao Wei¹, Francis Tang¹, Mei Wu¹, Saeed Jerban¹, Eric Y Chang^1,3, and Jiang Du^1
1University of California, San Diego, San Diego, CA, United States, ²Radiology, Beijing Chao-Yang Hospital, Beijing, China, ³VA San Diego Healthcare System, San Diego, CA, United States

Quantitative MRI biomarkers, such as T2, T2*, and T1rho have been used to detect cartilage degeneration. However, these biomarkers are sensitive to the magic angle effect. Magnetization transfer (MT) modeling provides magic angle insensitive parameters such as macromolecular proton fraction (MMF). This study focuses on the clinical evaluation of cartilage degeneration using 3D ultrashort echo time cones MT (3D UTE-Cones-MT) modeling in osteoarthritis (OA) patients. Both MMF and MT ratio (MTR) show significant negative correlations with WORMS grading of knee cartilage. This study highlights the potential of 3D UTE-Cones-MT techniques for detection of early cartilage degeneration in OA.

Linda Heskamp¹, Augustin C. Ogier^2,3, David Bendahan³, and Arend Heerschap^1
1Radiology and Nuclear Medicine, Radboud university medical center, Nijmegen, Netherlands, ²Aix Marseille Univ, Université de Toulon, CNRS, LIS, Marseille, France, ³Aix Marseille Univ, CNRS, CRMBM, Marseille, France

In patients with facioscapulohumeral muscular dystrophy (FSHD) it is known what the genetic origin of the disease is, but unknown how it is initiated and propagates along muscles. In a cross-sectional and longitudinal study we analyzed fat infiltration in lower leg muscles, tendon-to-tendon, with a 3D Dixon method. This revealed that fat infiltration starts with a distal “fat burst” in the first years of its initiation after which fat replacement further proceeds in a slower pace towards the proximal tendons. This indicates that the disease is triggered by an event typical for the distal parts of lower extremity muscles.

Misung Han¹, Radhika Tibrewala¹, Emma Bahroos¹, Valentina Pedoia^1,2, and Sharmila Majumdar^1,2
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Center for Digital Health Innovation, University of California, San Francisco, San Francisco, CA, United States

Cartilage degeneration, characterized by collagen structure disruption, proteoglycan depletion, and increased water content, has been shown to alter T₂ and T_1ρ relaxation times. A composite metric, R₂-R_1ρ, which further reflects an anisotropic component of R₂, has recently demonstrated high sensitivity to cartilage degeneration; however, quantification of R₂ and R_1ρ respectively requires long scan times. In this work, we validated the potential of assessing R₂-R_1ρ using one pair of signals with T_1ρ preparation and T₂ preparation from a combined T_1ρ/T₂ quantification sequence for in vivo knee MRI at 3T.