Rajakumar Nagarajan¹, Christopher Hayden², Samantha Gilmore², and Jane A Kent^2
1Human Magnetic Resonance Center, Institute for Applied Life Sciences, University of Massachusetts Amherst, Amherst, MA, United States, ²Kinesiology, University of Massachusetts Amherst, Amherst, MA, United States

Using 1H-MRS at 3T, vastus lateralis muscle acetylcarnitine was measured in 8 young male subjects at rest and in response to incremental, dynamic knee extension contractions. Intramyocellular [acetylcarnitine] increased >3-fold in response to the contraction protocol, thus buffering mitochondrial acetyl coenzyme A and thereby supporting oxidative metabolism of glucose and fat in the citric acid cycle. Measurement of acetylcarnitine has the potential to be a useful tool for the investigation of muscle substrate use and metabolic flexibility. This work is the first demonstration of dynamic changes in muscle [acetylcarnitine] at 3T.

Jia-Xin Feng¹, Jin Liu¹, Jian-Wei Liao¹, Wei Li¹, Xiao-Jun Chen¹, Lin Yao¹, Pan-Hui Huang¹, Long Qian², Ya-Jun Ma³, and Shao-Lin Li^1
1Department of Radiology, The Fifth Affiliated Hospital of Sun Yat-Sen University, Zhuhai, China, ²MR Research, GE Healthcare, Beijing, China, ³Department of Radiology, University of California San Diego, San Diego, CA, United States

Ultrashort echo time magnetization transfer (UTE-MT) is suggested to a non-invasive technique to assess collagenous matrix indirectly. In this study, we utilized UTE-MT sequence to investigate the relationship between UTE-MT ratio (UTE-MTR) measurements of paraspinal muscles and disc herniation in patients with disc degeneration. We found that the UTE-MTR showed a good performance in differentiation of patients with and without disc herniation, thus potentially valuable in predicting disc termination.

Antoine Naëgel^1,2, Jabrane Karkouri^1,2,3, Hélène Ratiney¹, Djahid Kennouche^1,4, Nicolas Royer^1,4, Guillaume Millet^1,4, Jill Slide⁵, Jérôme Morel⁶, Pierre Croisille¹, and Magalie Viallon^1
1Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, Lyon, France, ²Siemens Healthineers, Saint-Denis, France, ³Wolfson Brain Imaging Center, University of Cambridge, Cambridge, United Kingdom, ⁴LIBM - Laboratoire Interuniversitaire de Biologie de la Motricité,Université Jean Monnet Saint Etienne, Université Claude Bernard Lyon 1, Université Savoie Mont Blanc, Saint-Etienne, France, ⁵Department of Radiology, Michigan State University, East Lansing, MI, United States, ⁶anaesthetics and intensive care department, UJM-Saint-Etienne, Centre Hospitalier Universitaire de Saint-Étienne, Saint-Etienne, France

Dynamic 31P MRS was performed during a standardized exercise of the lower leg, in patients with chronic fatigue enrolled in 2 clinical studies: multiple sclerosis patients and COVID19 patients that were hospitalized in intensive care unit and requiring respiratory assistance. In this work, we also revisit certain assumptions on the metabolite T1 and question shortcuts often made to shorten 31P protocol for a better patient’s compliance.

Reese A. Dunne^1,2, Garry E. Gold², and Valentina Mazzoli^2
1Department of Mechanical Engineering, Mississippi State University, Mississippi State, MS, United States, ²Department of Radiology, Stanford University, Stanford, CA, United States

There is currently no established method to monitor muscle architecture throughout exercise intervention. This work investigates the value of DTI and fiber tractography to detect changes in fiber length in the quadriceps caused by resistance training. Five human subjects participated in a three-month training regimen, and DTI scans of their quadriceps were acquired. Through DTI tractography, fiber lengths were measured and compared between quadricep muscle components. There were no statistically significant changes in fiber length after three months of exercise, showing further optimization is needed to utilize DTI tractography for monitoring fiber length changes due to exercise.

Yunjie Liao¹ and Chen Thomas Zhao^2
1Department of Radiology, the Third Xiangya Hospital, Central South University, Changsha, China, ²Philips Healthcare, Guangzhou, China

Ankle sprain is a common athletic injury. Most patients with acute ankle sprain could not be treated properly, without precise diagnosis. Conventional Magnetic Resonance Imaging (MRI) sequences, like T1WI and T2WI, could not provide diagnostic proof as accurately as possible. Proton density weighted imaging (PDWI) collaborating with fat saturation (FS) could be a better alternative to detect the lesions. A comparative study was established, to investigate the performance of 4 sequences, with 8-channel carotid special surface coil. The results showed that PDWI-FS may be the best choice on diagnosis of ankle injuries among 4 sequences

Jeroen A Jeneson^1,2, Laura E Habets¹, Melissa T Hooijmans², Sandra M van den Berg², Bart Bartels¹, W Ludo van der Pol³, and Aart J Nederveen^2
1Child Health, University Medical Center Utrecht, Utrecht, Netherlands, ²Radiology and Nuclear Medicine, Amsterdam University Medical Center|location AMC, Amsterdam, Netherlands, ³Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, Netherlands

³¹P MRS has been used to non-invasively diagnose muscular mitochondrial dysfunction in disease. However, shifts in muscle fiber type composition due to muscle disuse are potential confounders since mitochondrial and capillary densities differ between fiber types. We obtained new quantitative information on this subject matter on basis of dynamic in vivo ³¹P MRS recordings from upper arm muscle of fourteen healthy subjects performing a maximal arm-cycling test. Analysis of the post-exercise time course of Pi in red and white myofiber pools distinguished by myoplasmic pH revealed a sevenfold difference in oxidative capacity between these fiber types in vivo.

Benjamin Marty^1,2, Pierre-Yves Baudin^1,2, Yves Fromes^1,2, Karim Wahbi³, and Harmen Reyngoudt^1,2
1NMR Laboratory, Institute of Myology, Neuromuscular Investigation Center, Paris, France, ²NMR Laboratory, CEA, DRF, IBFJ, MIRCen, Paris, France, ³Reference Center for Muscle Diseases Paris-Est, Institute of Myology, Paris, France

Becker muscular dystrophy (BMD) is a genetic neuromuscular disorder leading to muscle weakness and degeneration. Quantitative MRI has been widely proposed to characterize skeletal muscle tissue structure of BMD and revealed increased intramuscular fat fraction associated with functional decline. In this study, we measured the extracellular volume fraction (ECV) of skeletal muscle tissues using MR fingerprinting with water and fat separation. We evaluated this variable as an early imaging biomarker of skeletal muscle tissue alterations. Compared to healthy controls, we showed that the muscles of BMD subjects present elevated ECV before fatty replacement occurs.

Constantin Slioussarenko^1,2, Pierre-Yves Baudin^1,2, Harmen Reyngoudt^1,2, and Benjamin Marty^1,2
1NMR Laboratory, Institute of Myology, Neuromuscular Investigation Center, Paris, France, ²NMR Laboratory, CEA, DRF, IBFJ, MIRCen, Paris, France

In the field of neuromuscular disorders (NMD), fat fraction (FF) is an established biomarker of disease severity and water T1 (T1_H2O) has been shown to be a potential biomarker of disease activity. Those can be efficiently estimated through Magnetic Resonance Fingerprinting. However for muscle studies water-fat separation and FF quantification increase drastically the size of the dictionary and pattern matching time. We  introduce here a bicomponent dictionary where water and fat signals are stored separately. This approach allows improving MRF performance  and increasing the accuracy of FF quantification.

Matthew George Birkbeck^1,2,3, Linda Heskamp¹, Julie Hall^1,4, Ian Schofield¹, Avan Sayer^1,3, Richard Dodds^1,3, Roger Whittaker^1,5, and Andrew Blamire^1
1Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom, ²Northern Medical Physics and Clinical Engineering, Newcastle upon Tyne NHS FT, Newcastle upon Tyne, United Kingdom, ³NIHR Newcastle Biomedical Research Centre, Newcastle University, Newcastle upon Tyne, United Kingdom, ⁴Department of Neuroradiology, Newcastle Upon Tyne NHS FT, Newcastle upon Tyne, United Kingdom, ⁵Department of Neurophysiology, Newcastle upon Tyne NHS FT, Newcastle upon Tyne, United Kingdom

Sarcopenia is commonly associated with ageing, whereby individuals lose muscle mass and strength. One potential contributor to sarcopenia is the degeneration of motor units (MU), defined as a single motor neuron and the muscle fibres it innervates. We used motor unit MRI (MUMRI) to investigate changes to spontaneous MU activity and morphology in a cohort of healthy ageing adults. We found that MU activity and morphology did not appear to change with healthy ageing. We next aim to apply the MUMRI technique in patients with sarcopenia to look for evidence of accelerated MU loss compared to these healthy controls. 

Martin Schwartz^1,2, Petros Martirosian¹, Guenter Steidle¹, Thorsten Feiweier³, Bin Yang², and Fritz Schick^1
1Section on Experimental Radiology, University Hospital of Tuebingen, Tuebingen, Germany, ²Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Germany, ³Siemens Healthcare GmbH, Erlangen, Germany

Visualization of spontaneous mechanical activities in resting musculature using diffusion-weighted stimulated-echo imaging is highly depending on the sequence parameter settings as well as on the physiological parameters of the muscular contraction. Therefore, a concept for estimation of the visualization probability by using two contraction models is given in this work. Furthermore, the proposed concept is validated using diffusion-weighted measurements with varying diffusion-sensitizing times. The determined visualization probability is in good accordance to the relative number of visible spontaneous mechanical activities in the resting lower leg musculature.

Melissa Tamara Hooijmans¹, Laura E. Habets², Sandra A.M. van den Berg-Faay¹, Martijn Froeling³, Gustav J. Strijkers⁴, Fay-lynn Asselman⁵, Aart J. Nederveen¹, Jeroen A.L Jeneson², Bart Bartels², and W. Ludo van der Pol^5
1Department of Radiology and Nuclear Medicine, Amsterdam Movement Sciences, Amsterdam University Medical Center, Amsterdam, Netherlands, ²Center for Child Development, Exercise and Physical Literacy, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, Netherlands, ³Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ⁴Department of Biomedical Engineering & Physics, Amsterdam Movement Sciences, Amsterdam University Medical Center, Amsterdam, Netherlands, ⁵Department of Neurology and Neurosurgery, UMC Utrecht Brain Center, University Medical Center Utrecht, Utrecht, Netherlands

With upcoming therapeutic developments, quantitative MR is increasingly used to assess disease state and progression in neuromuscular disorders, including SMA. Yet, little is known about the disease state in the arm muscles in SMA. A multi-modal MR approach was used to examine fat fraction (FF), T2-relaxation time and diffusion properties, in the arm muscles of SMA patients and controls. Our results showed higher FF in the arm muscles of SMA patients which were negatively associated with the level of muscle strength. No clear changes were observed for qT2 while diffusion indices showed potential for mapping changes in muscle tissue itself. 

Rosemary Nicholas¹, Paul Greenhaff¹, and Susan Francis^1
1UNIVERSITY OF NOTTINGHAM, Nottingham, United Kingdom

Muscle volume and fat fraction can be quantified from mDIXON scans either manually or using automated processes.  Here we compare manual volumes of thigh and calf muscle ROIs with an automated pipeline created using FSL’s FAST segmentation, to compare muscle volume and fat fraction across subject groups and with their DXA values. Automatic volume segmentations correlated highly with manually drawn measures (r=.975) as well as DXA (r=0.840).  Group comparisons show COPD and post-COVID patients had significantly lower muscle mass and higher fat fraction. Automatic segmentation performs well compared to manually derived volumes and is more time efficient.

Nico Sollmann^1,2,3, Noah B. Bonnheim⁴, Gabby B. Joseph¹, Ravi Chachad¹, Jiamin Zhou¹, Jeannie F. Bailey⁴, Xiaojie Guo⁴, Ann A. Lazar⁵, Thomas M. Link¹, Aaron J. Fields⁴, and Roland Krug^1
1Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, ²Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Ulm, Germany, ³Department of Diagnostic and Interventional Neuroradiology, Technical University of Munich, Munich, Germany, ⁴Department of Orthopaedic Surgery, University of California San Francisco, San Francisco, CA, United States, ⁵Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, United States

Low back pain (LBP) is a global health burden, and up to 90% of affected patients are diagnosed with non-specific LBP. A structure increasingly recognized as a potential contributor to LBP is paraspinal musculature (PSM). In this study we revealed that the fat fraction (FF) of PSM derived from chemical shift encoding-based water-fat MRI (CSE-MRI) is associated with the Goutallier classification (GC) at each lumbar level as well as with self-reported pain. In contrast, other parameters (muscle volume, lumbar indentation value [LIV], muscle-fat index [MFI]) do not significantly correlate to the FF, despite being frequently used to evaluate PSM quality.