Jiang Du¹, Eric Diaz¹, Michael Carl², Won Bae¹, Christine Chung¹, and Graeme Bydder^1
1Radiology, University of California, San Diego, San Diego, California, United States, ²GE Healthcare, United States

Biological tissues commonly contain distinct water compartments and display multiple T2 relaxation behavior. Current standard techniques are based on multi-component fitting of multiple spin-echo images acquired with CPMG sequences. There are a group of tissues such as menisci, ligaments, tendons and cortical bone which show little or no signal with clinical CPMG or gradient echo sequences. Both free water and water bound to the collagen fibers are typically ‘invisible’. Here we propose a bi-component T2* analysis of images acquired with an ultrashort TE (UTE) sequence with a minimum TE of 8 us to quantify the free and bound water components.

Habib Al saleh¹, Kevin Johnson¹, Richard Kijowski², and Walter F Block^1,3
1Medical Physics, University of Wisconsin, School of Medicine & Public Health, Madison, WI, United States, ²Radiology, University of Wisconsin, School of Medicine & Public Health, Madison, WI, United States, ³Biomedical Engineering, University of Wisconsin, Madison, WI, United States

Ultra-short TE exhibits a great promise for imaging short T2 species in bone, tendon, ligament and cartilage. However, a considerable effort is spent for suppression of fat and long T2 components to enhance the contrast of short T2 species. An Inverted double half RF is presented for improved suppression of fat and long T2 species at 3T. Application of this method at 3T for musculoskeletal imaging showed promising results.

Richard J Hodgson¹, Peter Wright², Andrew J Grainger², Phillip O'Connor², Dennis McGonagle³, Phillip Helliwell³, Paul Emery³, and Matthew D Robson^4
1LMBRU, University of Leeds, Leeds, Yorkshire, United Kingdom, ²Leeds Teaching Hospitals NHS Trust, ³University of Leeds, ⁴University of Oxford

Ultrashort echo time imaging allows measurement of magnetization transfer ratios and simple ratios of signal intensity which depend on T2. The Achilles tendons of 11 patients with tendinopathy and 13 healthy volunteers were imaged with UTE 140/0.07/30 imaging with and without a MT prepulse, and a similar sequence with an effective echo time of 2ms. MTR and the ratio of the TE=2ms to UTE images were calculated for the Achilles tendon. The T2 dependent ratio was significantly greater in spondyloarthritis patients but the MTR was not. T2-dependent ratios are therefore likely to be better measures of tendinopathy than the MTR.

Nikolaus M. Szeverenyi¹, Won C. Bae¹, and Graeme M. Bydder^1
1Radiology, University of California, San Diego, San Diego, CA, United States

We describe a method which exploits unaveraged dipolar effects from a specific set of tissue-to-B0 orientations to produce detailed, high contrast MR images in fibrocartilage. Minimum intensity and coefficient of variation (CV) maps allow visualization of fiber structures previously not appreciated using MRI. This technology is a reduced sampling version of the Dipolar Anisotropy Fiber Imaging (DAFI) technology we have recently introduced. An example of a human knee meniscus specimen is demonstrated.

Yongxian Qian¹, Ashley A Williams², Constance R. Chu², and Fernando E. Boada^1,3
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States, ²Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, United States, ³Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States

This work demonstrates technical feasibility of in vivo ultra-high resolution (0.14mm) UTE imaging on human knee by using a home-developed fast 3D UTE sequence.

Michael Carl¹, Nikolaus M Szeverenyi², Jiang Du², Olivier M Girard², Won Bae², and Graeme M Bydder^2
1Global Applied Science Laboratory, GE Healthcare, San Diego, CA, United States, ²University of California, San Diego, United States

We report our initial experience with susceptibility weighted imaging of short T2 tissues. Adult human subjects and human tissue samples were imaged in a 3T clinical MR system using ultrashort TE sequences. UTE phase contrast is obtained from phase accrued during the RF excitation and readout part of the sequence. The mechanism of the changes may be related to tissue order and reflect the underlying physical chemistry of collagen.

Ping-Huei Tsai¹, Cheng Li², Jeremy Magland², Teng-Yi Huang³, Felix W Wehrli², and Hsiao-Wen Chung^1
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, ²Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, ³Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

The meniscus is critical to maintaining proper mechanical functioning of the knee, and plays a vital role in load distribution. Previous studies have emphasized that the menisci¡¦s complex alignment of collagen fibers contributes to the execution of this function. However, assessing the variable orientations of these fibers in vivo is difficult due to their relatively short T2 value and perturbations from spatial variation in magnetic susceptibility. This study used 3D radial imaging with minimal phase excitation and adiabatic fat suppression pulses to obtain adequate SNR to contrast fiber orientations in human menisci. The findings indicated this methodology allows visualization of the fiber structure of the meniscus in vivo.

Adam Johansson¹, Joakim Jonsson¹, Mikael Karlsson¹, and Tufve Nyholm^1
1Department of Radiation Sciences, Umeå University, Umeå, Sweden

A method using a Gaussian mixture model (GMM) for generating a substitute for a CT image from a set of MR images is presented. The heads of five patients were imaged with CT, a T2 weighted sequence and two dual echo UTE sequences employing both different echo times and flip angles. The method is evaluated using leave-one-out cross-validation. The mean absolute error of the CT number in the substitute CT images compared to the real CT images is found to be 141 Hounsfield units.

Robert Adam Horch^1,2, Daniel Frank Gochberg^2,3, Jeffry S Nyman^4,5, and Mark D Does^1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, ⁴VA Tennessee Valley Healthcare System, ⁵Department of Orthopaedics & Rehabilitation, Vanderbilt University

Modern ultrashort-echo time imaging has enabled human cortical bone MRI in a clinical setting. However, the cortical bone NMR signal contains contributions from both collagen-bound and pore space water, which vary across donors in opposing amounts and thereby degrade the diagnostic utility of the net bone signal. Herein, we present schemes for selectively imaging either bound or pore water, utilizing their differing T₁ and T₂ characteristics to generate diagnostically useful image contrast. An adiabatic full passage inversion-recovery sequence is shown to have bound water selectivity, and a short-TE fast spin echo sequence is shown to have pore water selectivity.

Dimitrios C Karampinos¹, Suchandrima Banerjee², Kevin F. King³, Roland Krug¹, Thomas M. Link¹, and Sharmila Majumdar^1
1Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, ³Global Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States

Diffusion-weighted imaging (DWI) of spinal muscles is challenging due to the large susceptibility-induced geometric distortions and the significant fat-induced chemical shift artifacts in single-shot EPI scans without parallel imaging. Reduced FOV imaging is an alternative approach to parallel imaging for reducing distortions as well as for excluding artifact prone regions of the FOV. In the present work, a stimulated echo prepared DW-EPI sequence enabling interleaved multi-slice inner volume imaging is developed. The proposed technique benefits from the reduced distortions of reduced-FOV DWI and the SNR advantages of stimulated echo preparation. The sequence trade-offs are characterized and in vivo results are shown in DWI of lumbar spine muscles.

Els Fieremans¹, Dmitry S Novikov¹, Eric E Sigmund¹, Kecheng Liu², Jens H Jensen¹, and Joseph A Helpern^1,3
1Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, United States, ²Siemens Medical Systems, United States, ³Center for Advanced Brain Imaging, Nathan S. Kline Institute, Orangeburg, NY, United States

The diffusivity measured in tissue in vivo depends on the diffusion time and is sensitive to tissue microstructure. Here we measure the time-dependent diffusion in the human calf muscle of healthy subjects. Based on our recent modeling of diffusion restricted by permeable membranes, we derive estimates of the free diffusion coefficient, membrane permeability, surface-to-volume ratio and mean fiber diameter. The obtained fiber diameter values agree very well with histological findings. Hence, we demonstrate here for the first time a non-invasive method to create parametric maps of cell membrane permeability and cell size.

Armen Alex Gharibans¹, Curtis Laurence Johnson¹, Danchin Daniel Chen¹, and John G Georgiadis^1
1Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Driven by the hypothesis that the transverse eigenvalue asymmetry in diffusion tensor imaging of skeletal muscle is correlated with gross muscle organization, we reconstruct and superimpose the tracts corresponding to the primary and secondary eigenvectors from DTI axial slices of the calf and thigh of a group of healthy, lean volunteers at rest. The reconstruction of organized nets consisting of crossing primary and secondary tracts provides quantitative evidence of the presence of a woven fabric in the middle part of the gastrocnemius and vastus lateralis muscles.

Nathan David Bryant¹, Ravneet Vohra², Sunita Mathur³, Krista Vandenborne⁴, and Glenn A. Walter^5
1Radiology, Vanderbilt University, Nashville, TN, United States, ²Physical Therapy, University of Florida, ³Department of Physical Therapy, University of Toronto, Canada, ⁴Department of Physical Therapy, University of Florida, ⁵The Department of Physiology and Functional Genomic, University of Florida

Dystrophic muscle is especially prone to injury during eccentric contractions. During cyclic bouts of damage and recovery, the muscle tissue undergoes various stages of remodeling. T2 and diffusion weighted MRI were used to observe changes associated with damage and repair in muscle tissue. This study set out to image eccentric damage in dystrophic muscle caused by downhill (-14°) treadmill running for 15 - 20 minutes. The greatest difference was seen in λ3 and FA. A combined analysis of T2 and diffusion parameters appears to be a promising approach for monitoring recovery from damage in longitudinal studies of dystrophic skeletal muscle.

Amanda K. Wake^1,2, and Bruce M. Damon^1,2
1Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center

A novel approach of identifying and using the best subset of diffusion directions for the calculation of the diffusion tensor and associated diffusion parameters was demonstrated using simulated images and was implemented in real DT-MR data sets.

Yoshikazu Okamoto¹, Kiichi Tadano², Tomohiko Masumoto¹, Yuji Hirano¹, Tomonori Isobe², and Manabu Minami^1
1University of Tsukuba Hospital, Tsukuba, Ibaraki, Japan, ²University of Tsukuba, Tsukuba, Ibaraki, Japan

The purpose of this study is to elucidate whether the probabilistic diffusion tractography (PDT) method is useful for visualizing skeletal muscle tractography, especially for �gtangled�h muscle fibers.And in conclusion, we successfully tracked skeletal muscle using the PDT method. PDT appears to be especially useful for demonstrating tangled muscle fibers, like SOL. Scan parameters using more MPG directions can produce better visualization.

Bruce M. Damon^1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

Diffusion tensor (DT)-MRI muscle fiber tracking can be used to determine muscle architectural parameters in vivo, but the data are noise-sensitive. The purpose of this study was to determine whether or not the accuracy and precision of DT-MRI-derived muscle architectural parameters could be improved by varying voxel dimensions and by fiber tract smoothing. Simulated datasets, based on previously published in vivo ultrasound images, were generated and analyzed in Matlab. Smaller voxel volumes, high signal-to-noise ratios, and 2^nd order polynomial fitting of the initially reconstructed fiber tracts were all found to be useful ways to improve DT-MRI-based muscle architectural measurements.

Claudia Fellner¹, Christine Hechtl², Marianne Vorbuchner³, Roland Büttner², Christian Stroszczynski¹, Okka W. Hamer¹, and Cornelius Bollheimer^2
1Institute of Radiology, University Medical Center Regensburg, Regensburg, Germany, ²Department of Internal Medicine I, University Medical Center Regensburg, Regensburg, Germany,³Siemens Healthcare, Erlangen, Germany

To assess dietary-induced and age-related changes of the muscle, 7 high fat fed rats (HFR) and 14 control animals (CR) fed with standard diet underwent MRI and MRS at the age of 16 and 21 months. Maximum cross sectional area of the M. quadriceps was smaller in HFR compared with CR and decreased with increasing age. HFR yielded increased lipid content and prolonged T2 relaxation times compared with control animals. Although all effects aggravated with increasing age, dietary-induced differences were most pronounced at the age of 16 month. The results of our pilot study support the hypothesis of sarcopenic obesity.

Danchin Daniel Chen¹, Diego Hernando², Curtis Laurence Johnson¹, Armen Alex Gharibans¹, Dolores D Guest³, Christie Ward⁴, Bhibha Das³, Ellen M Evans⁴, and John G Georgiadis^1,5
1Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Department of Radiology, University of Wisconsin, Madison, WI, United States,³Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁴Department of Kinesiology, University of Georgia, Athens, GA, United States, ⁵Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Single-voxel ¹H-MR spectroscopy was utilized in a cross-sectional study of elderly women (n=41) blocked on adiposity (obese vs. lean), with the lean group (n=17) further blocked on physical fitness (sedentary vs. physically active). The lipid distribution in the vastus medialis of lean/sedentary individuals was found to be similar to that of obese individuals, while lean/active individuals had a lower concentration of lipids (p<0.005) with a higher percentage stored as IMCL (p<0.1) than the obese and the lean/sedentary individuals.

Lucas Lindeboom¹, M. Eline Kooi¹, Matthijs Hesselink², Patrick Schrauwen³, Joachim Wildberger¹, and Vera Schrauwen-Hinderling^1,3
1Radiology, Maastricht University Medical Center, Maastricht, Netherlands, ²Human Movement Sciences, Maastricht University Medical Center, Maastricht, Netherlands, ³Human Biology, Maastricht University Medical Center, Maastricht, Netherlands

Using long echo times in Proton Magnetic Resonance Spectroscopy can provide new insight into skeletal muscle metabolism. Spectra with excellent separation of methylene and methyl peaks of IMCL and EMCL can be acquired in the vastus lateralis muscle. The use of carnitine as an internal concentration reference is more reliable, due to the diminished contamination of this peak at long TE. In vivo detection of acetylcarnitine is facilitated by the relative suppression of broad peaks from short T2 metabolites. Acetylcarnitine can possibly be seen as a marker for mitochondrial imbalance between acyl-CoA load and tricarboxylic acid cycle activity.

Kiril Schewzow^1,2, Martin Andreas^2,3, Ewald Moser^1,4, Michael Wolzt², and Albrecht Ingo Schmid^1,4
1MR Center of Excellence, Medical University of Vienna, Wien, Austria, ²Dpt. of Clinical Pharmacology, Medical University of Vienna, Wien, Austria, ³Dpt. of Surgery, Medical University of Vienna, Wien, Austria, ⁴Centre of Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria

Ischemia and reperfusion in skeletal muscle were studied by BOLD-MRI. In this work, we fitted the EPI time courses of the hyperemic response to ischemia, using similar a function as in DCE-MRI. Several parameters which describe hyperemia were determined from the fit results. Significant differences between muscle groups and the impact of post-occlusive stenosis could be shown.

Andrew D. Davis¹, and Michael D. Noseworthy^2,3
1Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, ON, Canada, ²Electrical and Computer Engineering, School of Biomedical Engineering, and Department of Radiology, McMaster University, Hamilton, Ontario, Canada, ³Brain Body Institute, St. Joseph's Healthcare, Hamilton, Ontario, Canada

BOLD data was acquired while plantar flexion exercise was performed using an in-house built MRI compatible ergometer. An intense exercise protocol of 2.5 minutes plantar flexion at 0.5 Hz at 50% of the subject’s MVC was performed. Immediately following the exercise, 10 minutes of BOLD data was acquired. Region of interest (ROI) analysis was performed on the data to segment the muscle groups of the lower leg, with both broadly inclusive ROIs that touched arteries, and more carefully drawn ROIs which excluded them. FT and time-series analysis was done. Next, an exercise protocol was performed to determine the effects of applying SAT bands just outside the FOV No physiological signals were present from the carefully drawn ROIs. The peaks only showed when the ROIs included the arteries. Time course plots for the Sat bands test revealed no obvious effects on the BOLD signal course due to the SAT bands. SAT bands do no not seem to affect BOLD signal recovery characteristics: base-peak height of recovery curves agree within the uncertainty for each muscle. The FT technique seems to be sensitive to arterial inflow, but not strangulation of the microvasculature in the tissue. Since SAT bands above and below imaging plane don’t seem to affect BOLD data results from tissue oxygenation, but do dampen arterial inflow effects, they should probably be used for all BOLD muscle scanning in the leg in future studies.

Noriyuki Tawara¹, Osamu Nitta², Hironobu Kuruma², Mamoru Niitsu³, Naoyuki Tamura⁴, Hideyuki Takahashi⁴, Atsuto Hoshikawa¹, Kakuko Nakamura¹, Toru Okuwaki¹, and Akiyoshi Itoh^5
1Department of Sports Medicine, Japan Institute of Sports Sciences, Tokyo, Japan, ²Department of Physical Therapy, Faculty of Health Sciences, Tokyo Metropolitan University, Tokyo, Japan,³Department of Radiology, Saitama Medical University, Saitama, Japan, ⁴Department of Sports Sciences, Japan Institute of Sports Sciences, Tokyo, Japan, ⁵Graduate Course of Computer Sciences, College of Sciences and Technology, Nihon University, Chiba, Japan

Strengthening of the rotator cuff muscles in one of the most integral parts of a rehabilitation program for athletes with shoulder problems who are involved in throwing sports. MRI can evaluate muscle activity; T2 of exercised muscle increases compared to that of rested muscle. However, it is difficult for efficient use as the evaluation by the rehabilitation. This study evaluated the detectability of the rotator cuffs�f muscle activity induced by acute exercises. In this study, we presented the detectability of rotator cuffs�f activities. T2 calculating from SE-EPI images indicated high detectability for muscle activity in the region of shoulder.

Kang-soo Kim¹, Do-beom Son², Heung-ho Choi¹, Choong-ki Eun³, and Chi-Woong Mun^1,4
1Biomedical Engineering, Inje University, Gimhae, Gyoungnam, Korea, Republic of, ²Radiology, Haeundae Paik Hospital, Busan, Gyoungnam, Korea, Republic of, ³Medicine, Radiology, Haeundae Paik Hospital, Busan, Gyoungnam, Korea, Republic of, ⁴UHRC, Inje University, Gimhae, Gyoungnam, Korea, Republic of

The purpose of this study is to investigate the the electrophysiological signal and energy phosphate metabolism measured by EMG and 31P-MRS, respectively, to examine the relationship of muscle fatigue during isometric calf-muscle exercise in human. Four healthy, male volunteers participated in this study. The subjects performed the static ankle plantar flexion exercise at 45 degree with 30% MVC according to the exercise protocol. The correlation coefficient(r) was 0.866 and they had statistically significant (P<0.001) between EMG and 31P-MRS. If it is possible to estimate muscle fatigue using the MDF and PCr/Pi, it will be widely used in various fields.

Amanda K Wake^1,2, Wyatt M. Rose^2,3, Bruce M. Damon¹, and Amanda K Wake^1
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, ³Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Some muscle modeling techniques require exact knowledge of a muscles boundaries. However, hand-digitizing regions of interest of many slices is time consuming. The purpose of this study was to determine whether or not defining regions of interest and interpolating the masks in the intervening slices could produce accurate estimates of the muscle boundaries. The data presented will show that this approach is feasible and produces muscle boundaries that are not significantly different from hand-digitized masks.

Donghoon Lee¹, Shu Feng¹, Daniel Chen¹, and Martin Kushmerick^1
1University of Washington, Seattle, WA, United States

We report our efforts on MRI monitoring for the process of muscle damage and recovery over time, which was correlated with histology. Myotoxin was injected on mouse hind-limb muscle of one leg to damage the muscle and continuously monitor the processes of muscle damage and repair using multi-parametric MRI and histology. Acute damage and necrosis is evident with 1 – 2 days post injection, followed by macrophage infiltration then by onset of regeneration followed by recovery by the third week. Our results show parametric MRI can be a systematic monitoring tool in distinguishing underlying muscle pathology as a function of time.

Lionel M Broche¹, Henning Wackerhage², and David J Lurie^1
1ABIC, University of Aberdeen, Aberdeen, Aberdeenshire, United Kingdom, ²School of Medical Sciences, University of Aberdeen, Aberdeen, Aberdeenshire, United Kingdom

Field-cycling MRI is a novel technique that involves changing the main magnetic field in an MRI scanner during the pulse sequence. Among others, it allows the measurement of interactions between water protons and ¹⁴N quadrupolar moments from proteins in tissues in vivo. In this study we used the linearity between the quadrupolar signal and the protein concentration to determine the physiological changes that occur during muscle swelling. The study was performed in the soleus and gastrocnemius region on 12 volunteers with controlled swelling. Data show good agreement with the values reported in the literature from standard biopsy procedure.

Howard Smithline^1,2, Long Ngo^3,4, Elyse Linson¹, and Robert Greenman^4,5
1Emergency Medicine, Baystate Medical Center, Springfield, MA, United States, ²Tufts University Medical School, Boston, MA, United States, ³General Medicine and Primary Care, Beth Israel Deaconess Medical Center, Boston, MA, United States, ⁴Harvard Medical School, Boston, MA, United States, ⁵Radiology, Beth Israel Deaconess Medical Center, Boston, MA, United States

The time constant (tau) of post-exercise phosphocreatine (PCr) recovery curve, reflects oxidative metabolism. Tau-PCr calculated from repeated low-intensity exercise may be more reliable than a single low-intensity or high-intensity exercise. Five volunteers performed three low-intensity and one high-intensity plantar flexion protocol on two days. 31P spectra were acquired every 10 seconds. Monoexponential curves were fitted to normalized PCr yielding tau and its SE. Weighted (inverse variance) intraclass correlation coefficients (ICC) were calculated. ICC increased from 0.39 to 0.92 by using repeated measures for low-intensity exercise. The ICC for the high-intensity exercise was 0.82. Repeated measures of tau-PCr increase reliability.

Christopher David James Sinclair^1,2, Robert D S Pitceathly¹, Indran Davagnanam², Michael G Hanna¹, Mary M Reilly¹, Tarek A Yousry^1,2, Xavier Golay², and John S Thornton^1,2
1MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, United Kingdom, ²Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom

We evaluated 3 point Dixon gradient-echo imaging of the extra-ocular muscles at 3T as a method of fat suppression by comparing it to short tau inversion recovery (STIR) and spectral fat saturation. The 3 sequences were prescribed to have identical geometrical coverage and an imaging time of 3m44s. Seven healthy adult subjects were imaged. The 3-point Dixon method delivered the statistically highest contrast ratio between the muscle and surrounding fat indicating efficient elimination of the fat signal and clear delineation of muscle boundaries. This method offers the additional potential advantage of quantifying intra-muscular fat-fraction in the extra-ocular muscles.