Ek T Tan¹, Kelly C Zochowski¹, Kenneth Serrano¹, and Darryl B Sneag^1
1Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States

Diffusion imaging may provide intracellular muscle denervation characterization complimentary to T₂- and fat fraction (FF) mapping. Non-invasive muscle diameter assessment was performed using multi-shell diffusion MRI with a cylindrical model. The apparent fiber diameter (AFD) was obtained using a dictionary method mapping restricted and free fractions to AFD. 16 subjects with suspected muscle denervation involving the brachial plexus and 4 healthy control subjects were imaged. The denervated AFD was smaller than non-denervated and healthy controls by 11 µm and 23 µm respectively. AFD in healthy controls were 67-101 µm, which compare well against histology values from the literature (50-90 µm).

Benjamin Marty^1,2, Fabian Balsiger³, Pierre-Yves Baudin^1,2, Lopez Alfredo^1,2, Ericky CA Araujo^1,2, and Harmen Reyngoudt^1,2
1Neuromuscular Investigation Center, NMR Laboratory, Institute of Myology, Paris, France, ²NMR Laboratory, CEA, DRF, IBFJ, MIRCen, Paris, France, ³Support Center for Advanced Neuroimaging, Institute for Diagnostic and Interventional Neuroradiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland

Our objective was to determine the influence of the reconstruction parameters on fat fraction and water T1 estimated in the skeletal muscle using MR fingerprinting with water and fat separation, to propose an optimized reconstruction procedure maximizing the accuracy and precision of the MRI variables, and evaluate it on in vivo data. We show that aliasing artefacts generate a bias in the estimates that could be mitigated by introducing a simple correction factor. Then, the accuracy and precision were improved by reconstructing the frames using a single radial spoke, and by using 10 SVD components for dictionary matching.

Thom T. J. Veeger¹, Gustav J. Strijkers², Valentina Mazzoli³, Hans C. van Assen¹, Jurriaan H. de Groot⁴, Lukas M. Gottwald⁵, Aart J. Nederveen⁵, Hermien E. Kan^1,6, and Melissa T. Hooijmans^2
1Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Biomedical Engineering & Physics, Amsterdam Movement Sciences, Amsterdam University Medical Center, Location AMC, Amsterdam, Netherlands, ³Radiology, Stanford University, Stanford, CA, United States, ⁴Rehabilitation Medicine, Leiden University Medical Center, Leiden, Netherlands, ⁵Radiology and Nuclear Medicine, Amsterdam Movement Sciences, Amsterdam University Medical Center, Location AMC, Amsterdam, Netherlands, ⁶Duchenne Center Netherlands, Veenendaal, Netherlands

We assessed strain rate distributions within the Tibialis Anterior muscle by acquiring whole lower leg 4D PC-MRI during dynamic exercise, with and without load. Our data revealed a spatially heterogeneous strain rate pattern along the length of the Tibialis Anterior muscle during movement cycle. During dorsiflexion, the smallest negative strain rates were observed (in first approximation) along the fiber in the most proximal segment and the largest positive strain rates (in first approximation) across the fiber in the most distal segment, while plantarflexion showed the expected opposite. No effect of load was detected on strain rates.

Sophia Swago¹, Abigail Cember², Brianna Moon¹, Puneet Bagga³, Neil Wilson⁴, Mark A. Elliott², Hari Hariharan², Ravinder Reddy², and Walter Witschey^2
1Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States, ²Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, ³St. Jude Children's Research Hospital, Memphis, TN, United States, ⁴Siemens Medical Solutions USA Inc, Malven, PA, United States

Water suppression limits the detection of non-labile proton downfield resonances in 1H magnetic resonance spectroscopy (MRS) due to cross-relaxation with water, and the cross-relaxation properties of these resonances has yet to be quantified in human skeletal muscle. We use spectrally-selective excitation in an inversion recovery experiment to compare the apparent T1 relaxation time of downfield resonances in skeletal muscle under selective and nonselective inversion conditions at 7T. Nonselective inversion significantly prolongs the longitudinal relaxation rate of resonances found 8.0, 8.2, and 8.5 ppm. This change is larger for the resonances at 8.2 and 8.5 ppm, indicating a stronger cross-relaxation effect.

Yuankui Wu¹, Xiaomin Liu¹, Jun Hua^2,3, Xiaodan Li¹, Haimei Cao¹, Yingjie Mei⁴, and Yikai Xu^1
1Department of Medical Imaging, Nanfang Hospital, Southern Medical University, Guangzhou, China, ²Neurosection, Division of MRI Research, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ³F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁴Philips healthcare, Guangzhou, China

Dermatomyositis (DM) is a chronic autoimmune microangiopathy. Accurate quantification of muscular microcirculation can assist in early diagnosis and improve clinical outcomes. Inflow-based vascular-space-occupancy (iVASO) is a novel perfusion technique without the need for exogenous contrast agents. This study aimed to determine the potential diagnostic value of iVASO-MRI for patients with DM. The results showed decreased arteriolar muscular blood volume (MBVa) in DM patients, which worsens with the progression of disease, and the diminished MBVa in morphologically-normal appearing muscles. This suggests that iVASO-derived MBVa has the potential to be used as a biomarker for early diagnosis of DM.

Martin Schwartz^1,2, Petros Martirosian¹, Günter Steidle¹, 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

Estimation of diffusion tensor parameters in healthy subjects and patients suffering from neuromuscular disease can be markedly affected by a high rate of spontaneous muscular activities during the MR examination. Therefore, a concept for realistic simulation of spontaneous muscular activities in diffusion tensor imaging and the estimation of their influence on derived parameters is given in this work. The degradation of the derived parameters depends strongly on the robustness of the chosen approach for tensor estimation.

Louise Otto¹, Martijn Froeling², Ruben van Eijk^1,3, Renske Wadman¹, Inge Cuppen⁴, Danny van der Woude⁵, Bart Bartels⁵, Fay-Lynn Asselman¹, Jeroen Hendrikse², and Ludo van der Pol^1
1Department of Neurology, UMC Utrecht Brain Center, University Medical Center, Utrecht, Utrecht, Netherlands, ²Department of Radiology, University Medical Center Utrecht, the Netherlands, Utrecht, Netherlands, ³Biostatistics & Research Support, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands, ⁴Department of Neurology and Child Neurology, UMC Utrecht Brain Center, University Medical Center, Utrecht, Utrecht, Netherlands, ⁵Department of Child Development and Exercise Center, University Medical Center Utrecht, the Netherlands, Utrecht, Netherlands

Quantitative MRI of muscles allows to measure disease progression or to assess therapeutic effects in neuromuscular diseases. We executed two studies on patients with spinal muscular atrophy, treated and untreated, with a protocol consisting of DIXON, T2 mapping and DTI on a 3T MR scanner. In treatment-naïve adult patients we demonstrated that qMRI was able to measure subclinical disease progression. In young children with SMA, quantitative MR parameters of the DIXON and DTI sequence showed ongoing fatty infiltration and normalization of thigh muscle microstructure during the first year of nusinersen treatment.

Can Wu^1,2, Qi Peng³, William Paredes⁴, Moriel Vandsburger⁵, and Matthew K. Abramowitz^4
1Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Philips Healthcare, Andover, MA, United States, ³Department of Radiology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, United States, ⁴Department of Medicine, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, United States, ⁵Department of Bioengineering, University of California, Berkeley, Berkeley, CA, United States

Chronic kidney disease (CKD) is associated with reduced skeletal muscle mass, strength, and function, but a quantitative approach to systematically assess changes in skeletal muscle is lacking. The purpose of this study was to develop a multimodal MR method for quantitative assessment of skeletal muscle in patients with CKD compared to normal controls. The study revealed significant changes of T1ρ, intra- and extra-myocellular lipid ratio, ADC, and FA in CKD or dialysis patients. In addition, there was significant correlation between T1ρ and DTI biomarkers. These findings may provide new insights into the impaired skeletal muscle function in CKD patients.

Linda Heskamp¹, Matthew Birkbeck^1,2,3, Roger Whittaker¹, Ian Schofield¹, and Andrew Blamire^1
1Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University, Newcastle upon Tyne, United Kingdom, ²Newcastle Biomedical Research Centre, Newcastle University, Newcastle upon Tyne, United Kingdom, ³Northern Medical Physics and Clinical Engineering, Freeman Hospital, Newcastle upon Tyne NHS Foundation Trust, Newcastle upon Tyne, United Kingdom

Motor units (MUs) play a fundamental role in muscle physiology and disease. Contraction of muscle fibres belonging to a MU induces signal voids on diffusion weighted (DW) images enabling us to image these MUs (MUMRI). We demonstrated that MUMRI can also extract the twitch profile of single MUs. Computational modelling showed that the attenuation of net magnetisation and the cumulative phase changes increase with twitch magnitude. Therefore, we can measure the MU time profile by altering the timing of electrical nerve stimulation relative to the diffusion-encoding gradients. We applied this experimentally and measured in-vivo contraction times of human MUs.

Lara Schlaffke¹, Robert Rehmann¹, Anja Schreiner¹, Marlena Rohm¹, Johannes Forsting¹, Martijn Froeling², Martin Tegenthoff¹, Matthias Vorgerd¹, and Anne-Katrin Güttsches^1
1Neurology, University Clinic Bergmannsheil Bochum gGmbH, Bochum, Germany, ²Radiology, UMC Utrecht, Utrecht, Netherlands

Skeletal muscle biopsy is the gold-standard in the diagnosis of inflammatory and hereditary muscle disorders. Ten patients who underwent muscle biopsy for diagnostic purposes were examined by qMRI (Fat-fraction, water T2-time and diffusion). The fat fraction, the severity of degenerative and inflammatory parameters and the amount of type 1/2-fibers were determined in all samples. The amount of fat tissue correlated significantly between histopathology and qMRI. EPG Water T2-time correlated with the in the histopathologic analysis. The study provides the basis for qMRI methods in the follow up of patients with neuromuscular disorders, especially in the context of emerging treatment strategies.