Guobin Li¹, Mathias Nittka², Dominik Paul², and Wei Jun Zhang^1
1Siemens Mindit Magnetic Resonance Ltd., Shenzhen, Guang Dong, China, People's Republic of, ²Siemens Healthcare Sector, Erlangen

In SEMAC and SEMAC-MAVRIC hybrid sequences, additional z-phase encoding steps are used to correct the through-plane distortion. But the preknowledge of the distortion degree is needed to determine the extension factor of the z-phase encoding. In this work, a method to scout the through-plane distortion by applying the readout gradient in slice direction is presented, which can be fully integrated into SEMAC and SEMAC-MAVRIC hybrid sequence.

Chiel Johan den Harder¹, Ulrike A Blume¹, and Clemens Bos^2
1MR CTO, Philips Healthcare, Best, Netherlands, ²MR Clinical Science, Philips Healthcare, Best, Netherlands

Slice-Encoding for Metal Artifact Correction (SEMAC) has been proposed for reducing image distortions near metal implants. In SEMAC, the number of through-plane phase encoding steps determines the frequency range for which slice distortions are corrected. Signals with frequencies outside this range will alias in through-plane direction. Here, SEMAC and Off-Resonance Suppression (ORS) are combined to limit signal selection to a confined frequency range and thus prevent back-folding. Phantom and in-vivo experiments show that ORS allows substantial reduction of phase encoding steps to obtain SEMAC images without back-folding. The resulting imaging time reduction supports the clinical utility of SEMAC.

Guobin Li¹, Mathias Nittka², Dominik Paul², and Lars Lauer^2
1Siemens Mindit Magnetic Resonance Ltd., Shenzhen, Guang Dong, China, People's Republic of, ²Siemens Healthcare Sector, Erlangen

SEMAC and MAVRIC are two recently developed techniques to significantly reduce the geometric distortion caused by metallic implants in MR examinations. However, both two methods are suffering from long scan time due to their intrinsic feature of 3D acquisition. In this abstract, the limitations of these two methods in terms of sampling efficiency are analyzed and an improved implementation MSVAT-SPACE is presented to show the higher imaging speed

Kevin M Koch¹, and Kevin F King^1
1Global Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States

3D Multi-Spectral Imaging (3D-MSI) can significantly reduce susceptibility artifacts near metal implants. In order to reduce these artifacts, 3D-MSI acquires a large amount of spectral and spatially encoded data. With such requirements, it is challenging to acquire high-resolution 3D-MSI images in a clinical environment. Here, we explore the combined effects of data-driven parallel imaging and compressed sensing in improving the resolution capabilities of 3D-MSI near a total knee replacement at 1.5T.

Kevin M Koch¹, Matthew A Koff², and Hollis G Potter^2
1Global Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States, ²Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States

3D-Multi-Spectral Imaging techniques (MAVRIC, SEMAC, and combinations thereof) can substantially reduce image artifacts in the presence of implanted metal. Residual susceptibility artifacts in 3D-MSI techniques are commonly manifested as localized “pileup” artifacts - where many spins are frequency encoded to the same spatial position. Here, we show that spectral information inherent to 3D-MSI acquisitions can be used to construct field maps with sufficient accuracy to combat these residual artifacts through estimation of local gradients and Jacobian intensity correction of shifted pixels. The proposed methods are demonstrated on clinical images at 1.5T of total knee and shoulder replacements composed of cobalt-chromium alloys.

Wenmiao Lu¹, Jun Deng¹, Yi Lu², Garry Gold³, and Brian Hargreaves^3
1Nanyang Tech. University, Singapore, SG, Singapore, ²University of Illinois, Urbana Champaign, United States, ³Stanford University, United States

Slice Encoding for Metal Artifact Correction (SEMAC) fully corrects metal-induced artifacts in MR images, which nevertheless suffers from two main problems, namely long scan times and low signal-to-noise ratio. This work presents a new POCS-based reconstruction procedure for SEMAC, which fully exploit the correlation and sparsity in SEMAC-encoded slices. The new reconstruction procedure not only greatly reduces scan times incurred to fully correct metal-induced artifacts but also leads to the improved SNR of SEMAC corrected result.

Uchechukwuka Diana Monu¹, Pauline W Worters², Kyunghyun Sung², Kevin M Koch³, Garry E Gold², and Brian A Hargreaves^2
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Department of Radiology, Stanford University, Stanford, CA, United States, ³Applied Science Lab, GE Healthcare, Waukesha, WI, United States

In MRI, the measurement of RF excitation fields is challenging. Furthermore, B0 inhomogeneities make B1 mapping near metallic implants especially difficult. Currently available B1 mapping methods that are based on gradient echo and spin echo techniques have not been successfully used around metallic implants. This is mostly due to signal loss from increased susceptibility and imaging artifacts near metal. In this work, B1 maps of phantoms were obtained using the standard gradient echo double angle method (DAM) and using the SEMAC DAM on a 1.5T whole-body MR scanner. A good comparison of these maps and matlab simulations carried out to model the error values of the SEMAC DAM, allowed for the SEMAC DAM to be subsequently applied to a metallic implant phantom at both 1.5T and 3T. The flip angle maps obtained show that the proposed technique is a valid approach for tackling the issue of B1 mapping near metallic implants.

Catherine Lee Hayter¹, Matthew F Koff¹, Kevin F Koch², Parina Shah¹, Edwin P Su³, and Hollis G Potter^1,4
1Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States, ²Applied Science Laboratory, General Electric Healthcare, Waukesha, Wisconsin, United States, ³Center for Hip Pain and Preservation, Hospital for Special Surgery, New York, NY, United States, ⁴Weill Cornell Medical College of Cornell University, New York, NY, United States

Metal-on-metal hip resurfacing is associated with specific complications, including metal hypersensitivity which may manifest as synovitis, bursitis or osteolysis. The purpose of this prospective, observational study was to review patterns of osteolysis and synovitis in symptomatic and asymptomatic individuals following resurfacing. Synovitis was detected in a similar proportion of symptomatic and asymptomatic patients. Osteolysis was only detected in symptomatic individuals. The similarities of the synovitis measurements combined with the lack of correlation with blood chromium and weak correlation with blood cobalt ion levels indicate that additional factors must be considered when determining the long term prognosis of hip resurfacing implants.

Maartje E Vossen¹, Wouter M Teeuwisse¹, Monique Reijnierse¹, Desiree M van der Heijde², Nadine B Smith¹, and Andrew G Webb^1
1Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Rheumatology, Leiden University Medical Center

High spatial resolution images of the SI joints have been acquired at 7 Tesla in both volunteers and patients sufferenting from sacroilitis. Very small cortical erosions can be visualized with an in-plane resolution of 0.5 x .5 mm. Water/fat imaging using a three-point Dixon method was shown to differentiate between fatty infiltration and edema in a second patient.

Michael Bock¹, Florian Meise¹, Titus Lanz², Reiner Umathum¹, Lydia Schuster³, Lars Gerigk³, Armin M Nagel¹, Ann-Kathrin Homagk¹, and Wolfhard Semmler^1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²RAPID Biomedical GmbH, Rimpar, Germany, ³Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

MR imaging of the knee has been demonstrated at 7 Tesla, but the full potential of the high field strength has so far not been exploited due to the lack of multi-channel receive coils. In this work we present preliminary data acquired with a 15 channel extremty coil which demonstrates that MR imaging of the knee region is feasible with parallel imaging at 7 Tesla in clinically acceptable imaging times.

Vladimir Juras^1,2, Goetz Welsch¹, Ladislav Valkovic², Pavol Szomolanyi^1,2, Iris-Melanie Nöbauer-Huhmann¹, Ivan Frollo², and Siegfried Trattnig^1
1Department of Radiology, Medical University of Vienna, Vienna, Austria, Austria, ²Department of Imaging Methods, Institute of Measurement Science, Bratislava, Slovakia

The aim of this study was to investigate the performance of the clinical MR sequences in in-vivo ankle imaging at ultrahigh-field (7 Tesla) MR. As a key parameter SNR and CNR of different structures were used with 3 sequences (3D-GRE, 2D-SE, 2D-TSE). Significantly better performance of clinical MR sequences in ankle joint imaging at 7T in comparison to 3T was observed. The substantial benefit from ultrahigh-field could be demonstrated.

Goetz Hannes Welsch^1,2, Vladimir Juras¹, Pavol Szomolanyi¹, Tallal Charles Mamisch³, Peter Baer⁴, Claudia Kronnerwetter¹, Friedrich Frank Hennig², Hiroyuki Fujita⁵, and Siegfried Trattnig^1
1Medical University of Vienna, Vienna, Vienna, Austria, ²Department of Trauma Surgery, University of Erlangen-Nuremberg, Erlangen, Bavaria, Germany, ³University of Berne, ⁴Siemens Healthcare, ⁵Quality Electrodynamics

Aim of this study was to compare the quantitative and qualitative performance of a routine 8-channel knee coil at 3T and a new 28-channel knee coil at 7T. Compared to an optimized 3T protocol, at 7T, i)the resolution was increased whereas keeping the same examination time and ii)the examination time was reduced whereas keeping the spatial resolution the same. CNR as well as the subjective quality revealed better results for both 7T measurements compared to the 3T measurements, documenting the possible superiority of 7T MRI in the knee joint compared to 3T in the presence of a dedicated multi-channel coil.

Gregory Chang¹, Ligong Wang¹, Guoyuan Liang², Graham C Wiggins¹, Punam K Saha², and Ravinder R Regatte^1
1NYU Langone Medical Center, New York, NY, United States, ²University of Iowa, Iowa City, Iowa, United States

High resolution 7 Tesla MRI can detect subregional variations in trabecular bone micro-architecture of the wrist in healthy subjects. These differences may explain differences in individuals' bone quality and fracture risk.

Gregory Chang¹, Ding Xia¹, Graham C Wiggins¹, Guillaume Madelin¹, Christian Glaser¹, Matthew Finnerty², Hiroyuki Fujita², and Ravinder R Regatte^1
1NYU Langone Medical Center, New York, NY, United States, ²Quality Electrodynamics, Mayfield Village, Ohio, United States

This in vivo study on 10 healthy subjects compares the performance of a 28 channel phased array coil and a circularly polarized coil for morphologic magnetic resonance imaging and T2 mapping of knee cartilage at 7 Tesla. Signal-to-noise ratio and contrast-to-noise ratio are higher with the 28 channel coil, favoring its use for future studies of osteoarthritis or other knee pathology.

Martijn Froeling^1,2, Johannes M Hoogduin^3,4, Dennis W.J. Klomp³, Klaas Nicolay¹, Gustav J Strijkers¹, and Aart J Nederveen^2
1Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, ²Department of Radiology, Academic Medical Center, Amsterdam, Netherlands, ³Imaging Division, University Medical Center Utrecht, Utrecht, Netherlands, ⁴Brain Division, University Medical Center Utrecht, Utrecht, Netherlands

Data acquisition at high field increases the signal allowing for higher spatial resolution. In this study demonstrate the feasibility of DTI of skeletal muscle at 7T maximizing the spatial resolution.

Stefan Zbyn^1,2, David Stelzeneder¹, Goetz Hannes Welsch^1,3, Lukas L. Negrin⁴, Vladimir Juras^1,5, Pavol Szomolanyi^1,5, Ronald Dorotka², and Siegfried Trattnig^1
1Department of Radiology, Medical University Vienna, Vienna, Austria, ²Department of Orthopaedic Surgery, Medical University Vienna, Vienna, Austria, ³Department of Trauma Surgery, University Hospital of Erlangen, Erlangen, Germany, ⁴Department of Trauma Surgery, Medical University Vienna, Vienna, Austria, ⁵Department of Imaging Methods, Institute of Measurement Science - SAS, Bratislava, Slovakia

The aim was to apply gradient-echo sequence optimized for sodium imaging at 7T for the evaluation of repaired tissue glycosaminoglycan (GAG) content in the patients after bone marrow stimulation (BMS) and matrix-associated autologous chondrocyte transplantation (MACT) treatment of articular cartilage. Significantly lower GAG content was found in the repaired tissue in comparison to the native cartilage in both treatment groups and significantly lower GAG content was observed in BMS repair tissue in comparison to MACT repair tissue. Our results suggest that the MACT treatment provides higher GAG content and therefore higher quality repair tissue in comparison to the BMS techniques.

Jimin Ren¹, Ivan Dimitrov^1,2, Changho Choi¹, A Dean Sherry^1,3, and Craig R Malloy^1,4
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, ²Philips Medical Systems, Cleveland, Ohio,³Department of Chemistry, University of Texas at Dallas, Richardson, Texas, United States, ⁴VA North Texas Health Care System, Dallas, Texas, United States

Lactate plays a crucial role in energy homeostasis in body. Elevated lactate can be an important marker of mitochondria disease, poor prognosis in acutely ill patients, or nutritional deficiency of thiamine. Lactate measurement by proton MRS is usually done by detecting the methyl resonance. In muscle, overlapping signals from lipids poses challenge to the effectiveness of this approach. Here we demonstrate that STEAM-based sequence with long echo time at 7T allows detection of lactate methine signal in exercised muscle in vivo. It is found that lactate decays very fast (half time 1.4 min) following 10 minutes of hand open-close exercise.

Jimin Ren¹, Ivan Dimitrov^1,2, Craig R Malloy^1,3, and A Dean Sherry^1,4
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, ²Philips Medical System, Cleveland, Ohio, United States, ³VA North Texas Health Care System, Dallas, Texas, United States, ⁴Department of Texas at Dallas, University of Texas at Dallas, Richardson, Texas, United States

Proton MRS offers many advantages for detection of a number of muscle metabolites. However, quantitative and reliable measurement of muscle metabolites can be quite challenging due to multiple factors intrinsic to MRS and skeletal muscle itself. We present here an optimized 1H MRS acquisition protocol, termed “muscle module”, for acquisition of high-quality spectra for easy data analysis. This muscle module is based on a STEAM sequence, with data acquisition at two different echo-times, TE 140 and 280 ms, without applying water-suppression pulses. Its advantage in spectral resolution enhancement and quantitative analysis is demonstrated in a large population (n = 80).

Katja Heinicke^1,2, Jackson Green^1,2, Ivan Dimitrov^3,4, Sergey Cheshkov³, Jimin Ren³, Craig R. Malloy³, and Ronald G. Haller^1,2
1Neuromuscular Center, Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, United States, ²Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX, United States, ³Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, ⁴Philips Medical Systems, Cleveland, OH, United States

31P-MRS provides insight into muscle energy metabolism, and 1H-MRS offers direct measurement of intramyocellular lipid concentration and the concentration of acetylcarnitine which is important for characterizing mitochondrial function and integrity. The objective of this pilot study was to evaluate the feasibility of interleaved 1H and 31P-MRS measurements in human skeletal muscle during exercise in a 7 Tesla whole body magnet. This study demonstrates that, it is possible to obtain consecutive high resolution 1H-MRS and 31P-MRS spectra in response to exercise. The rate of recovery of high energy phosphates in skeletal muscle post exercise is much faster than recovery of acetylcarnitine.

Wolfgang Bogner¹, Marek Chmelik¹, Siegfried Trattnig¹, and Stephan Gruber^1
1Department of Radiology, Medical University of Vienna, Vienna, Austria

For phosphorus magnetic resonance spectroscopy (31P-MRS) the SNR of surface coil localized fully relaxed 31P spectra was reported to be almost doubled between 3T vs 7T in the human calf muscle. These studies did not consider differences in the sensitive volume of coils. Localized 31P-MRS allows unbiased comparison of spectral quality between different field strength. We found that the reported SNR gain for surface coil localized 31P-MRS was significantly underestimated. In our study localized 31P-MRS showed an ~3.2 times higher SNR at 7T than at 3T with identical measurement parameters, while surface coil localized 31P-MRS showed only an increase by a factor of ~2.

Hermien E. Kan¹, Sebastian Aussenhofer¹, Andrew Webb¹, Aranee Techawiboonwong², and Itamar Ronen^1
1Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands, ²Department of Electrical Engineering, Mahidol University, Nakornpathom, Thailand

Assessment of diffusive properties of phosphorous metabolites using diffusion tensor spectroscopy (DTS) has so far been limited to animal studies. ³¹P DTS of the phosphocreatine signal could provide a useful method to probe intracellular space in humans, as it is not present in the same compartment as the adipose tissue that influences DTI measurements of skeletal muscle. In this study, we show, for the first time in humans, that it is feasible to obtain ADC and FA values of different skeletal muscles in the human calf using 2D ³¹P DT CSI and a newly developed coil design for 7T.

Keerthi Shet¹, Hikari Yoshihara², Joe Schooler², John Kurhanewicz², Michael Ries², and Xiaojuan Li^2
1Radiology, University of California, San Francisco, San Francisco, CA, United States, ²University of California, San Francisco

HRMAS NMR spectroscopy was used to quantify T1-rho and T2 relaxation times and examine the T1-rho dispersion characteristics of human OA cartilage specimens. T2 of water in cartilage showed a bi-exponential decay, with the shorter component significantly higher in OA cartilage. A mono-exponential decay was a better fit to T1-rho of control cartilage as against a bi-exponential decay for OA-cartilage. The longer T1-rho component of OA cartilage was found to be significantly higher than the T1-rho of healthy cartilage which can be attributed to proteoglycan degeneration in OA cartilage.

Jose G Raya¹, Gerd Melkus², Silvia Adam-Neumair³, Kevin Dunham⁴, Olaf Dietrich³, Maximilian F Reiser³, Reinhard Putz³, Peter M Jakob⁵, and Christian Glaser^4
1Radiology, New York University Langone Medical Center, New York, NY, United States, ²University of California, San Francisco, ³University of Munich, ⁴New York University Langone Medical Center, ⁵University of Wuerzburg

The aim of this work was to characterize the functionality of human healthy and OA articular cartilage using a multiparametric approach (T2, T1, ADC, FA and water volume fraction). Samples of healthy (n=10) and OA (n=3) patellar cartilage were MRI examined at 17.6T (resolution=50×100μm2) native, under loading (strain=26%) and 4h after relaxation (n=5 healthy, n=1 OA). Differences in MRI parameters between the native and loading examinations were larger in absolute value and extension in OA than in the healthy samples. After 4h relaxation, healthy samples returned to their native values, whereas the OA sample demonstrated signs of the indentation.

Julien GONDIN¹, Christophe VILMEN¹, Patrick J. COZZONE¹, Guillaume DUHAMEL¹, and David BENDAHAN^1
1Centre de Résonance Magnétique Biologique et Médicale (CRMBM) - UMR CNRS 6612, Faculté de Médecine - Université de la Méditerranée, Marseille, France

We have constructed a strictly non-invasive experimental setup adapted to an ultra-high field MR system and report in the present work the results of MRI investigation and force production measurements in exercising hindlimb mouse muscles at ultra-high field. This newly strictly non-invasive device allowed highly reproducible measurements of both force production and muscle activation (T2 changes) in exercising hindlimb mouse muscles within an ultra-high field magnet. Our setup appears as a suitable tool for future ultra-high field functional MR investigations of exercising hindlimb mouse muscles.

Jiang Du¹, Won Bae¹, Hermida Juan², Eric Diaz¹, Christine Chung¹, Darryl DLima², and Graeme Bydder^1
1Radiology, University of California, San Diego, San Diego, California, United States, ²Scripps Reseach Institution

Bone water occurs at various locations and in different states. It is associated with the mineral phase, bound to the organic matrix, and a significant fraction occurs in more or less free form in the microscopic pores of the Haversian and the lacuna-canalicular systems. A measure of free water concentration can potentially provide a surrogate measure of bone porosity, while a measure of bound water reflects collagen content. Here we propose to use bi-component analysis of UTE images to quantify T2* and fractions of the free and bound water components in cortical bone.

Olivier M Girard¹, Jiang Du¹, Robert F Mattrey¹, and Graeme M Bydder^1
1Department of Radiology, University of California, San Diego, CA, United States

Dynamic Contrast Enhanced MRI has been applied for micro-vascular characterization of various tissues such as brain lesions and tumors. So far its application to bone perfusion characterization has been limited to bone marrow studies due to the lack of detectable signal from cortical bone, which has extremely short T2 and therefore cannot be detected by conventional gradient echo sequences. Ultrashort echo time (UTE) sequences offer an opportunity to measure signal from cortical bone. In this preliminary study we report on the kinetic analysis of dynamic UTE imaging data of cortical bone acquired on healthy volunteers using a clinical 3T MR scanner.

Richard J Hodgson¹, Nikesh Menon², Andrew J Grainger², Philip O'Connor², Dennis McGonagle³, Philip 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

There is increasing interest in quantifying tendon disease in spondyloarthritis. Ultrashort echo time and gradient echo images were acquired from the Achilles tendon of 24 patients and 14 healthy volunteers. Signal intensities at different echo times before and after intravenous gadolinium were normalized to the signal intensity on unenhanced UTE images. Ratios were significantly greater in patients with spondyloarthritis compared to controls. This was most marked on the ratio of the image acquired at TE=2ms to the UTE image. These measurements are straightforward, reproducible and fast and may be useful as potential quantitative biomarkers of tendon disease in spondyloarthritis.

Vladimir Juras^1,2, Stefan Zbyn¹, Vladimir Jellus³, Pavol Szomolanyi^1,2, Ivan Frollo², and Siegfried Trattnig^1
1Department of Radiology, Medical University of Vienna, Vienna, Austria, Austria, ²Department of Imaging Methods, Institute of Measurement Science, Bratislava, Slovakia, ³Siemens AG, Erlangen, Germany

Proton NMR relaxation properties (T₂*) in human Achilles tendon were assessed in vivo at 3T and 7T field strength. 3D-UTE sequence (capable of minimum TE=0.07ms) was used with the set of 8 different TE {min 0.07 ms, max 4.00 ms}. T₂* were found to be statistically significantly different between two field strengths in the most of the selected anatomical regions. Bulk T₂* was 0.98+/-0.08ms (3T) and 0.41+/-0.10 (7T). T₂ may prospectively serve as a marker for diagnosis of early tendon diseases.