Marta Brigid Maggioni¹, Martin Krämer^1,2, and Jürgen R. Reichenbach^1,2,3,4,5
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University, Jena, Germany, ²Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University, Jena, Germany, ³Michael Stifel Center for Data-driven and Simulation Science Jena, Friedrich Schiller University, Jena, Germany, ⁴Abbe School of Photonics, Friedrich Schiller University, Jena, Germany, ⁵Center of Medical Optics and Photonics, Friedrich Schiller University, Jena, Germany

B₁ mapping is a considerable challenge for T₁ quantification, and it is especially difficult for short T₂^* species because only ultrashort echo-time (UTE) imaging sequences are able to retrieve signal in such tissues. Recently a method called Actual Flip Angle Imaging (AFI) has shown promising results because of its potential to be combined with UTE acquisition. However the AFI method is characterized by long acquisition times. In this work we propose to use undersampling to reduce the acquisition times of  AFI-based B₁ mapping.

Refaat E Gabr¹, Lingzhi Hu², Xingxian Shou², Yongquan Ye², Weiguo Zhang², and Ponnada A Narayana^1
1Diagnostic and Interventional Imaging, University of Texas Health Science Center at Houston, Houston, TX, United States, ²UIH America Inc., Houston, TX, United States

We developed a multi-flip multi-spoiling phase angle method for quantitative assessment of tissue parameters. Application in phantom studies and in vivo knee imaging shows promising performance for high resolution parameter mapping in clinically feasible scan time.

Stefan Sommer^1,2, Tom Hilbert^3,4,5, Constantin von Deuster^1,2, Natalie Hinterholzer², Markus Klarhöfer¹, and Daniel Nanz^2,6
1Siemens Healthcare, Zurich, Switzerland, ²Swiss Center for Musculoskeletal Imaging (SCMI), Balgrist Campus, Zurich, Switzerland, ³Advanced Clinical Imaging Technology (ACIT), Siemens Healthcare, Lausanne, Switzerland, ⁴Department of Radiology, Lausanne University Hospital (CHUV), Lausanne, Switzerland, ⁵LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁶University of Zurich, Zurich, Switzerland

Clinical application of UTE (ultrashort echo time) sequences in musculoskeletal studies remains limited, despite their potential to unveil quantitative short-T₂* information of e.g. tendons or ligaments. The major shortcoming of quantitative mapping is the considerably longer scan time compared to conventional, anatomical imaging sequences. We investigated the feasibility and use of an isotropic 3D radial compressed sensing UTE (CUTE) prototype sequence for quantitative mapping of short-T₂* components in the knee. Similar image quality and T₂* values were obtained for non-accelerated and accelerated acquisitions. Thus, CUTE sequences show great promise for fast and clinically feasible UTE T₂* mapping.

Céline Smekens¹, Quinten Beirinckx², Floris Vanhevel³, Pieter Van Dyck³, Arjan den Dekker², Jan Sijbers², Thomas Janssens¹, and Ben Jeurissen^2
1Siemens Healthcare NV/SA, Beersel, Belgium, ²imec-Vision Lab, Department of Physics, University of Antwerp, Wilrijk, Belgium, ³Department of Radiology, Antwerp University Hospital and University of Antwerp, Edegem, Belgium

T2* mapping using ultrashort echo time (UTE) MRI allows for quantitative evaluation of collagen-rich knee structures with short mean transverse relaxation times. However, acquisitions with low through-plane resolution are commonly used to obtain T2* maps within reasonable scan times, affecting the accuracy of the estimations because of partial volume effects. In this work, model-based super-resolution reconstructions based on UTE Spiral VIBE MRI were performed to obtain high-resolution T2* maps of knee structures within a reasonable scan time. The obtained T2* maps are comparable to maps generated with direct 3D UTE Spiral VIBE acquisitions while requiring approximately 25% less scan time.

Ruaridh M Gollifer^1,2, Tim JP Bray^1,3, Margaret Hall-Craggs^1,3, and Alan Bainbridge^2
1Centre for Medical Imaging (CMI), University College London, London, United Kingdom, ²Department of Medical Physics and Bioengineering, University College London Hospital, London, United Kingdom, ³Department of Imaging, University College London Hospital, London, United Kingdom

Short tau inversion recovery (STIR) imaging is the mainstay of clinical imaging in inflammatory musculoskeletal (MSK) diseases, and generates hyperintense signal in areas of inflammation in bone marrow (bone marrow oedema). However, the assessment of STIR images of bone marrow is based on qualitative judgement of signal intensity and can be confounded by variations in fat content resulting from the healing response in bone to inflammation. We aimed to develop a method which would (1) separate fat and water and (2) provide a water-specific T₂ measurement, enabling separation and individual quantification of oedema and fat in the bone marrow. 

Marcelo Victor Wust Zibetti¹, Azadeh Sharafi¹, Mahesh Bharath Keerthivasan², and Ravinder Regatte^1
1Radiology, NYU Langone Health, New York, NY, United States, ²Siemens Healthineers, New York, NY, United States

We modified the Cartesian 3D-fast spoiled gradient-echo sequence with T1rho magnetization preparation for prospective acceleration of knee-joint mapping using optimized sampling patterns (SPs) and compressed sensing (CS) reconstructions. In this sequence, after each T1rho preparation module, several k-space lines are captured, partially filling the 3D k-space. However, the ordering of the k-space filling is very important to maintain consistent T1rho contrast and to obtain stable quantitative mapping. This is even more challenging when arbitrary SPs are used for accelerated MRI. We investigate different k-space ordering schemes considering optimized SPs and Poisson disk SPs in prospective 3D-T1rho acquisition with CS reconstructions.

Hongyu Li¹, Mingrui Yang², Jeehun Kim², Chaoyi Zhang¹, Ruiying Liu¹, Peizhou Huang³, Sunil Kumar Gaire¹, Dong Liang⁴, Xiaoliang Zhang³, Xiaojuan Li², and Leslie Ying^1,3
1Electrical Engineering, University at Buffalo, State University of New York, Buffalo, NY, United States, ²Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, Cleveland, OH, United States, ³Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY, United States, ⁴Paul C. Lauterbur Research Center for Biomedical Imaging, Medical AI research center, SIAT, CAS, Shenzhen, China

This abstract presents a combined deep learning framework SuperMAP to generate MR parameter maps from very few subsampled echo images. The method combines deep residual convolutional neural networks (DRCNN) and fully connected networks (FC) to exploit the nonlinear relationship between and within the combined subsampled T1rho/T2 weighted images and the combined T1rho/T2 maps. Experimental results show that the proposed combined network is superior to single CNN network and can generate accurate T1rho and T2 maps simultaneously from only three subsampled echoes within one scan with results comparable to reference from fully sampled 8-echo images each for two separate scans.

Jeehun Kim^1,2, Qi Peng³, Can Wu^4,5, and Xiaojuan Li^1,6
1Department of Biomedical Engineering, Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, Cleveland, OH, United States, ²Case Western Reserve University, Cleveland, OH, United States, ³Department of Radiology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, United States, ⁴Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ⁵Philips Healthcare, Andover, MA, United States, ⁶Department of Diagnostic Radiology, Cleveland Clinic, Cleveland, OH, United States

Quantitative T_1ρ mapping is a promising biomarker for detecting tissue compositional changes at early stages of diseases. For reliable and reproducible measurements, T_1ρ preparation pulses should be robust to B₀ and B₁ inhomogeneity. In this work, six different preparation schemes were evaluated in terms of their responses to B₀ and B₁ inhomogeneities on agarose phantoms and volunteers using both 3T and 7T MRI systems.

Qi Peng¹, Can Wu^2,3, Jee Hun Kim^4,5, and Xiaojuan Li^4,5,6
1Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, United States, ²Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ³Philips Healthcare, Andover, MA, United States, ⁴Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, Cleveland, OH, United States, ⁵Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, United States, ⁶Department of Diagnostic Radiology, Cleveland Clinic, Cleveland, OH, United States

Magnetization-prepared gradient echo (MP-GRE) sequences have been commonly used for quantitative MRI in the literature to improve imaging speed. Paired acquisitions with RF phase-cycling could eliminate image blurring due to longitudinal relaxation and loss of MP contrast along the GRE readouts, with doubled scan time. This study introduces a novel unpaired phase cycling strategy to eliminate the time penalty with reduced sensitivity to B₀ field inhomogeneities for high resolution quantitative mapping in MP-GRE sequences. The feasibility and efficacy of this strategy were demonstrated in both phantom and human studies.

Qianfeng Wang¹, He Wang^1,2, Danyang Feng¹, Fei Dai¹, Yuwen Zhang¹, and Baofeng Yang^1
1Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China, ²Human Phenome Institute, Fudan University, Shanghai, China, Shanghai, China

In this study, we demonstrate that T1ρ-MRF can be achieved by varying flip angle, repetition time, echo time, as well as spin lock time—in a pseudorandom manner at 11.7T MR system.

Marco Fiorito¹, Maksym Yushchenko¹, Davide Cicolari², Mathieu Sarracanie¹, and Najat Salameh^1
1Center for Adapatable MRI Technology (AMT center), Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland, ²Department of Physics, University of Pavia, Pavia, Italy

$$$T_1$$$ mapping in MRI can be employed in a variety of techniques for diagnosis and treatment follow-up, but generally suffers from long acquisition times. Little effort has been put in low magnetic field regimes, where sensitivity is further impeded. Nevertheless, low field provides higher $$$T_1$$$ dispersion and favours adaptable scanner designs, suitable for dedicated applications such as MRI of body extremities. Here, we assess our newly developed interleaved, Look-Locker based $$$T_1$$$ mapping sequence in calibrated samples, and we present a first in vivo $$$T_1$$$ map of a volunteer’s hand at 0.1 T.

Nathan Tibbitts Roberts^1,2, Diego Hernando^1,3, Daiki Tamada¹, and Scott B Reeder^1,3,4,5,6
1Radiology, University of Wisconsin - Madison, Madison, WI, United States, ²Electrical and Computer Engineering, University of Wisconsin - Madison, Madison, WI, United States, ³Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, ⁴Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States, ⁵Medicine, University of Wisconsin - Madison, Madison, WI, United States, ⁶Emergency Medicine, University of Wisconsin - Madison, Madison, WI, United States

Tissue fat and spatially varying B1 inhomogeneities are known confounders of quantitative T1_W(ater) mapping methods that use variable flip angle techniques. T1_W measurements can be corrected for B1 heterogeneity, but this typically requires an additional B1 calibration acquisition both extending patient acquisition time and introducing image registration considerations. In this work we propose simultaneous estimation of B1, T1_W, proton density fat-fraction and R2* using a three-pass approach using dual orthogonal RF pulses and multiple flip angles. The feasibility and noise performance of this proposed acquisition and fitting strategy are evaluated using Cramer-Rao Lower Bound analysis, simulations, and phantom experiments.

Justin Yu¹, Anshuman Panda¹, and Alvin Silva^1
1Department of Radiology, Mayo Clinic Arizona, Phoenix, AZ, United States

Quantitative MRI can precisely measure biomarkers for disease, such as liver hemochromatosis. R2* correlates with liver iron concentration (LIC), but data is scarce for 3T R2* mapping. The out-of-the box vendor provided sequences for quantitative R2* measurements do not precisely measure large R2* values in a standardized phantom. The discrepancy is greater at higher R2* values. This can lead to underestimates in LIC quantification for patients with severe hemochromatosis. R2* mapping from different MRI vendors may yield different results, and patient specific QA may be necessary for clinical utilization for quantitative R2* mapping.

Francisco Javier Fritz¹, Mohammad Ashtarayeh¹, Joao Periquito², Andreas Pohlmann², Markus Morawski³, Carsten Jaeger⁴, Thoralf Niendorf², Kerrin J. Pine⁴, Evgeniya Kirilina^4,5, Nikolaus Weiskopf^4,6, and Siawoosh Mohammadi^1
1Institut für Systemische Neurowissenschaften, Universitätklinikum Hamburg-Eppendorf, Hamburg, Germany, ²Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ³Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany, ⁴Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁵Center for Cognitive Neuroscience Berlin, Free University Berlin, Berlin, Germany, ⁶5Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany

We studied the impact of fibre dispersion and myelin on the angle-dependent gradient-recalled echo signal decay in simulation and experimental data from post-mortem tissue. We compared the classical log-mono-exponential and quadratic time-dependent signal model (M2) derived from Wharton and Bowtell’s forward-model with and without myelin-water contribution. We found that R₂*-angular dependency was modulated by fibre dispersion and the R₂*-angular dependency is removed using M2. We also observed that the higher-order parameter estimated from experimental data at small angles and dispersion was only reflected in simulations when accounting for myelin-water contributions, indicating that this pool needs to be added into M2.

Giorgia Milotta¹, Nadège Corbin^1,2, Antoine Lutti³, Siawoosh Mohammadi^4,5, and Martina Callaghan^1
1Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom, ²Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536, CNRS/University Bordeaux, Bordeaux, France, ³Laboratory for Research in Neuroimaging, Department for Clinical Neuroscience, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland, ⁴Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, ⁵Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Quantitative relaxometry in the brain is appealing because of its microstructural sensitivity. Estimating bulk parameters assumes a single relaxation time per voxel, which is only valid when the residency time is short with respect to T₁. In reality, the relative contribution of sub-compartments will depend on flip angle and echo time. Here, we simulate a two-compartment model (myelin and intra-extracellular water) and estimate T₁ with FA-specific signals derived via three estimation schemes. We quantify the impact of myelin water fraction, residency time and transmit field inhomogeneity on these estimates and find good correspondence with in vivo T₁ estimates at 7T. 

Fabrizio Fasano^1,2, John Evans³, Chloe Benson⁴, Yifei Wang⁴, Derek K Jones^3,5, Alison Paul⁴, and Robert Turner^6,7
1Siemens Healthcare Ltd, Camberly, United Kingdom, ²Siemens Healthcare GmbH, Erlangen, Germany, ³Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff, United Kingdom, ⁴School of Chemistry, Cardiff University, Cardiff, United Kingdom, ⁵Mary McKillop Institute for Health Research, Faculty of Health Sciences, Australian Catholic University, Melbourne, Australia, ⁶Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁷Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom

Myeloarchitecture has a critical role in the specialisation of brain microcircuitry. It shapes network functions from small to large scale, and ultimately behaviour. We tested, on homemade Agar gel phantoms, the multi-shot inversion recovery slice shuffled EPI IR-MS-EPI approach recently proposed by Sanchez and co-workers  (Proc. Intl. Soc. Mag. Reson. Med. 2018, 60). Our measurement results and the simulated performances of MS-IR-EPI showed a good reproducibility of the T1 maps and a preserved quality of its point spread function, when acquiring at higher-than 500μm in-plane resolution, making it suitable for assessing grey matter myelination process. 

Kaia Ingerdatter Sørland¹, Pål Erik Goa^2,3, Kirsten Margrete Selnæs^1,3, Elise Sandsmark³, Cristopher George Trimble¹, Mohammed R. S. Sunoqrot¹, Mattijs Elschot^1,3, and Tone F. Bathen^1,3
1Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway, ²Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway, ³Department of Radiology and Nuclear Medicine, St. Olavs University Hospital, Trondheim, Norway

Quantitative analysis of T2-weighted (T2W) MR images is hindered by the lack of signal intensity standardization. The tissue T2 values are independent of variations in scanner parameters, but T2 mapping is normally not part of the clinical pathway. Autoref is an automated dual-reference tissue normalization of T2W images developed in our group, aiming to reproduce the prostate T2 values. In this study we measured the prostate T2 value in seven healthy volunteers, and compared them with pseudo-T2 values from Autoref normalized T2W. The Autoref was proven to reproduce prostate T2 values as well as contrast within the prostate zones. 

Yitong Li¹, Xiaoqing Liang¹, Bowen Hou¹, Yan Xiong¹, Weiyin Vivian Liu², and Xiaoming Li^1
1Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, ²MR Research, GE Healthcare, Beijing, China

Multiple relaxation quantitative maps can be obtained from a single scan with synthetic MRI. Previous researches have investigated this technique in lumbar spine applications, but coil selection, which may introduce bias into the quantitative data, has not been taken into account. In this study, we compared the measured quantitative parameters (T1, T2, and PD) using three coils separately and evaluated data reliability and repeatability. Coil selection contributes to differences in measurements of lumbar spine synthetic MRI, which should be concerned in future studies.

Ping Wang¹, Jay D Turner¹, Juan Uribe¹, and John C Gore^2
1Barrow Neurological Institute, Phoenix, AZ, United States, ²Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

This study aims to develop a T_1ρ dispersion protocol method for human lumbar spine imaging, with a specific goal to detect proteoglycan loss in the intervertebral disc (IVD), which is an initial step in degenerative disc disease (DDD). T_1ρ dispersion parametric images are able to distinguish the nucleus pulposus from annulus fibrosus based on differences in  exchangeable protons, as predicted theoretically. This work is relevant for clinical applications for DDDas it provides novel, quantitative, and clinically translatable in vivo imaging biomarkers capable of detecting proteoglycan changes.

Xiaoqing Liang¹, Weiyin Vivian Liu², Jingyi Wang¹, and Xiaoming Li^1
1Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, ²MR Research,GE Healthcare, Beijing, China

The distinction between the nucleus pulposus (NP) and the peripheral annulus fibrosus (AF) of intervertebral disc is an important diagnostic indicators of intervertebral disc degeneration (IVDD) on MRI. So far, there have not been many studies or mature approaches to quantify the distinction between the NP and AF. This study aimed to discover histogram distribution of the T2 relaxation time of the AF and NP using Gaussian fitting. Our results showed that Gaussian-fitted histogram analysis of T2 relaxation time could achieve quantitative distinction between the NP and AF, and computed Gaussian-fitted histogram parameters had good performance on diagnosing IVDD.