Azadeh Sharafi¹, Smita Rao², Martijn A. Cloos¹, Ryan Brown¹, and Ravinder R. Regatte^1
1Radiology, NYU Langone Health, New York, NY, United States, ²Physical Therapy, New York University, New York, NY, United States

Diabetic peripheral neuropathy (DPN) is characterized by metabolic and microvascular impairment (1) that damage peripheral nerves (2) and cause ischemic conditions and muscle degeneration in the lower extremities (3). Researchers have investigated the possibility of reversing DPN symptoms through exercise therapy (4). Such studies will benefit from quantitative biomarkers to evaluate therapeutic strategies targeting muscle function. In this work, we developed a magnetic resonance fingerprinting (MRF) technique that is insensitive to B₁ imperfections for simultaneous T₁, T₂, and T_1ρ relaxation mapping of skeletal muscle in DPN patients in response to exercise intervention at 3T.

Benjamin Marty^1,2, Harmen Reyngoudt^1,2, Jean-Marc Boisserie^1,2, Pierre-Yves Baudin³, 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

Recently, MR fingerprinting with water and fat separation was proposed to quantify water T1 (T1_H2O) in the muscles of patients with neuromuscular disorders. In this study, we investigated the sensitivity of T1_H2O as a quantitative biomarker of disease activity, by comparing it with fat suppressed T2-weighted (FatSup-T2w) imaging and quantitative water T2 (T2_H2O) mapping, in a dataset of 61 subjects with different NMDs. We observed a significant increase of T1_H2O values in muscles with FatSup-T2w signal hyperintensities. We also investigated different hypothesis explaining the moderate correlation (ρ = 0.54) observed between T1_H2O and T2_H2O in the muscles of these patients.

Kevin Keene^1,2, Jan-Willem Beenakker^1,3, Melissa Hooijmans⁴, Karin Naarding^2,5, Erik Niks², Louise Otto⁶, Ludo van der Pol⁶, Martijn Tannemaat², Hermien Kan^1,5, and Martijn Froeling^7
1Department of Radiology, C.J. Gorter center for high field MRI, Leiden University Medical Center, Leiden, Netherlands, ²Department of Neurology, Leiden University Medical Center, Leiden, Netherlands, ³Department of Ophthalmology, Leiden University Medical Center, Leiden, Netherlands, ⁴Amsterdam University Medical Center, Amsterdam, Netherlands, ⁵Duchenne Center Netherlands, Utrecht, Netherlands, ⁶Department of Neurology, UMC Utrecht Brain Center, University Medical Center Utrecht, Utrecht, Netherlands, ⁷Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands

Multi-echo spin-echo transverse relaxometry mapping using multi-component models is used to study disease activity in neuromuscular disease. A recent model using extended phase graphs (EPG) was introduced to obtain separate T2 values for water and fat, accounting for B1 and stimulated echoes. We improved this model and showed the importance of including flip angle slice profiles with a chemical shift displacement in the slice direction and correct calibration methods for the T2 of the fat component. We showed its performance in four clinical cohorts, and showed a gradual decline in T2_water with increasing fat fractions.

Patrik Krumpolec^1,2, Radka Klepochová¹, Ivica Just Kukurová¹, Marjeta Tušek Jelenc¹, Jozef Ukropec², Ivan Frollo³, Christopher Rodgers^4,5, Barbara Ukropcová^2,6, Siegfried Trattnig^1,7, Martin Krššák^1,7,8, and Ladislav Valkovič^1,3,4
1High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ²Institute of Experimental Endocrinology, Biomedical Research Center of Slovak Academy of Sciences, Bratislava, Slovakia, ³Department of Imaging Methods, Institute of Measurements Science, Slovak Academy of Sciences, Bratislava, Slovakia, ⁴Oxford Centre for Clinical Magnetic Resonance Research, BHF Centre of Research Excellence, University of Oxford, Oxford, United Kingdom, ⁵Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom, ⁶Institute of Pathophysiology, Faculty of Medicine, Commenius University, Bratislava, Slovakia, ⁷Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria, ⁸Division of Endocrinology and Metabolism, Department of Internal MedicineIII, Medical University of Vienna, Vienna, Austria

The aim of this study was to investigate effect on the demand driven ATP production and carnosine content in the aging muscle. We utilized dynamic and saturation transfer ³¹P- and ¹H-MRS. The dynamic experiment included acquisition of baseline data during two minutes of rest, six minutes of plantar flexion exercise (3.5 minutes long FAST measurement was performed), and six minutes of recovery. We report excessive Pi-to-ATP flux and increase of PME concentration during exercise as well as lower muscle carnosine concentration leading to lower pH after exercise in seniors, which could be linked to deprived metabolic flexibility in this population.

Lin Chen^1,2, Michael Schär^1,3, Kannie W.Y. Chan^1,2,4, Jianpan Huang⁴, Zhiliang Wei^1,2, Hanzhang Lu^1,2, Qin Qin^1,2, Robert G. Weiss^1,3, Peter C.M. van Zijl^1,2, and Jiadi Xu^1,2
1Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, United States, ³Division of Cardiology Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁴Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China

Phosphocreatine (PCr) plays a vital role in neuron and myocyte energy homeostasis, and measurement of PCr provides a unique way to achieve insight into cellular energetics. Our previous study demonstrated that high-resolution PCr mapping of human skeletal muscle can be obtained on standard 3T clinical MRI scanner using artificial neural network-based chemical exchange saturation transfer (ANNCEST). Here, for further validation, we applied ANNCEST to measure PCr changes in exercised skeletal muscle and compared the measures with those from ³¹P magnetic resonance spectroscopy. The feasibility of estimating spatially resolved PCr recovery rate constants using ANNCEST was also demonstrated.

Louise A.M. Otto¹, Ludo W.L. van der Pol¹, Lara Schlaffke ², Camiel A. Wijngaarde¹, Marloes Stam¹, Renske I. Wadman¹, Inge Cuppen³, Ruben P.A. van Eijk^1,4, Fay-Lynn Asselman¹, Bart Bartels⁵, Danny van der Woude⁵, Jeroen Hendrikse⁶, and Martijn Froeling^6
1Neurology, UMC Utrecht Brain Center, University Medical Center, Utrecht, Utrecht, Netherlands, ²Neurology, BG-University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany, ³Neurology and Child Neurology, UMC Utrecht Brain Center, University Medical Center, Utrecht, Utrecht, Netherlands, ⁴Biostatistics & Research Support, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands, ⁵Child Development and Exercise Center, UMC Utrecht Brain Center, University Medical Center, Utrecht, Utrecht, Netherlands, ⁶Radiology, UMC Utrecht Brain Center, University Medical Center, Utrecht, Utrecht, Netherlands

qMRI of skeletal muscle has shown promising results in other neuromuscular diseases, but multi-parametric imaging has not been executed in Spinal Muscular Atrophy. We investigated a cohort of 31 patients and 20 controls with protocol consisting of DIXON, T2 mapping and DTI on a 3T MR scanner. All parameters differed significantly between patients and controls. DTI elucidates distinct properties of the muscle, suggesting atrophy by a lowered MD and increased FA. DTI shows correlation with muscle strength and motor function. This suggests the potential of diffusion tensor imaging of muscle in monitoring disease progression in SMA. 

Max Kaplan^1,2, Alice Hatt¹, Bezahd Babaei^1,3, Lauriane Jugé^1,2, and Lynne Bilston^1,2
1Neuroscience Research Australia, Randwick, Australia, ²University of New South Wales, Kensington, Australia, ³University of Melbourne, Parkville, Australia

Intramuscular fat (IMF) increases with BMI and age, but it is unknown how it affects skeletal muscle viscoelastic properties, despite the key role skeletal muscle mechanical properties play in our capacity to move. We studied the effects of IMF on the anisotropic mechanical properties under large deformation of the calf muscles in healthy and obese participants, using an advanced approach incorporating diffusion tensor imaging data into magnetic resonance elastography reconstructions. Results show that intramuscular fat had no significant effect on muscle shear moduli, but stretching or shortening muscle altered the parallel and/or perpendicular stiffness and viscosity of some muscles.

Matthew Birkbeck^1,2,3, Linda Heskamp¹, Ian Schofield¹, Andrew Blamire¹, and Roger Whittaker^1
1Newcastle University, Newcastle upon Tyne, United Kingdom, ²Newcastle Biomedical Research Centre, Newcastle upon Tyne, United Kingdom, ³Regional Medical Physics, Newcastle upon Tyne, United Kingdom

Motor units are fundamental components in the process of contraction of skeletal muscle. Motor unit morphology changes in response to pathologies including motor neurone disease and sarcopenia. Currently the clinical method to investigate motor unit morphology and activity is invasive needle electromyography. Here we present a novel diffusion weighted imaging technique, motor unit MRI (MUMRI). MUMRI has been used to investigate the morphology of single human motor units, producing quantitative data on cross sectional area and dimensions of human motor units. This data agrees with current literature. MUMRI has detected statistically significant changes in the morphology of motor units.

Kihwan Kim¹, Yuning Gu¹, Gahee Kim¹, Mei Wong¹, Bryan Clifford ^2,3, Sherry Huang¹, Zhi-Pei Liang^2,3, and Xin Yu^1,4
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁴Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, United States

This study examined the effects of muscle contraction, induced by electrical stimulation, on creatine kinase (CK) reaction rate and the rate of phosphocreatine (PCr) recovery after its transient depletion in mouse skeletal muscle using phosphorous-31 (³¹P) magnetic resonance fingerprinting and dynamic ³¹P magnetic resonance spectroscopy. Our results showed that electrical stimulation induced a significant increase in CK reaction rate by ~14%, as well as an increased in PCr recovery rate by 26%, suggesting a positive preconditioning effect induced by electrical stimulation.

Vadim Malis¹, Usha Sinha², and Shantanu Sinha^3
1Physics, UC San Diego, La Jolla, CA, United States, ²Physics, San Diego State University, San Diego, CA, United States, ³Radiology, UC San Diego, La Jolla, CA, United States

Strain and Strain rate tensors can be computed from velocity encoded phase contrast imaging. The study of the variation of deformation indices with force output (% Maximum Voluntary Contraction (MVC)) can provide information on the aging muscle. However, such studies have been limited by the long acquisition time precluding its use at high MVCs and in older subjects. We developed a compressed sensing VE-PC technique to enable acquisitions across a range of MVCs and applicable to older subjects as well. Significant differences in the deformation indices were seen between 11 young / 8 senior subjects as well between different %MVCs.