Adam V. Dvorak^1,2, Dushyant Kumar³, Guillaume Gilbert⁴, Cornelia Laule^1,2,5,6, G.R. Wayne Moore^2,6, Alex L. MacKay^1,5,7, and Shannon H. Kolind^1,2,5,8
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, ²International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada, ³Radiology, University of Pennsylvania, Philadelphia, PA, United States, ⁴MR Clinical Science, Philips Canada, Mississauga, ON, Canada, ⁵Radiology, University of British Columbia, Vancouver, BC, Canada, ⁶Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada, ⁷UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada, ⁸Medicine (Neurology), University of British Columbia, Vancouver, BC, Canada

We introduce the CALIPR framework, applied here to multi-component T₂ relaxation myelin water imaging (MWI) to achieve a simultaneous increase in data quality and decrease in acquisition time. CALIPR showed robust results for data acquired with aggressive under sampling acceleration, strong agreement with a newly developed “gold-standard” reference MWI acquisition, excellent scan-rescan repeatability, and the ability to acquire whole-brain MWI in under 5 minutes.

While this work demonstrates dramatic improvements the CALIPR framework brings to MWI, its utility can be extended to a wide range of both quantitative and qualitative MRI applications across different scanner vendors and field strengths.

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

T1 mapping of species with very fast T2/T2* relaxation is impossible with conventional methods measuring echoes refocused by gradients or radiofrequency pulses. We therefore present a new approach to estimate T1 relaxation times of short-T2 tissue such as bone, tendon, or ligament by sampling transversal magnetization at different inversion times with a short-T2 sensitive ultra-short-TE readout. The presented T1 mapping method is efficient and B1-insensitive. By acquiring multiple echoes, it is possible to obtain T1 relaxation times at short and long echo-time and therefore assess the influence of short-T2 components.

Sharada Balaji¹, Irene M. Vavasour^2,3, Adam Dvorak¹, Poljanka Johnson⁴, Alex MacKay^1,2, and Shannon H. Kolind^1,2,3,4
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, ²Radiology, University of British Columbia, Vancouver, BC, Canada, ³International Collaboration on Repair Discoveries, Vancouver, BC, Canada, ⁴Medicine, University of British Columbia, Vancouver, BC, Canada

Myelin water fraction (MWF) quantifies myelin content in the central nervous system. MWF analysis typically assumes there is no water exchange between different water pools in tissue during the measurement. Here we investigate the effect of incorporating a two-pool model of exchange in a study of MWF in multiple sclerosis (MS) spinal cord and compare with results from the original algorithm. Including exchange resulted in higher MWF values and myelin water residence times that were correlated with MWF, but maintained the expected relationship in MWF between MS subtypes and controls.

Marc-Antoine Fortin^1,2, Véronique Fortier^1,3, Jorge Campos Pazmino¹, Andre van der Kouwe⁴, and Ives Roger Levesque^1,5
1Medical Physics Unit, McGill University, Montreal, QC, Canada, ²Physics, NTNU, Trondheim, Norway, ³Medical Imaging, McGill University Health Centre, Montreal, QC, Canada, ⁴Athinoula A. Martinos Center for Biomedical Imaging, Havard Medical School, Boston, MA, United States, ⁵Research Institute of the McGill University Health Centre, Montreal, QC, Canada

To design a novel fat-water separated T₁ mapping technique from a multi echo (ME) version of the Magnetization Prepared Two Rapid Acquisition of Gradient Echoes (MP2RAGE) sequence by adapting the MP2RAGE sequence to shorter T₁ values resembling values observed for fat (between 200 and 800 ms) and introducing a 3-point Dixon fat-water separation step in the analysis.

Yongquan Ye¹, Xiaodi Liu², Ying Wu², Zhongqi Zhang¹, and Jian Xu^1
1UIH America, Inc., Houston, TX, United States, ²United Imaging Healthcare, Shanghai, China

In this work, we evaluated the performance of a recently proposed high resolution multi-parametric method, i.e. MULTIPLEX, on a state-of-the-art 5T whole body scanner. Comparing to the 3T counterpart, MULTIPLEX on 5T generally offers improved SNR, image quality and imaging efficiency, while maintaining satisfactory performance on B₁/T₁ mapping.

Zhi-Yuan Chen¹, Yu-Pin Liu¹, and Yunzhu Wu^2
1Department of Radiology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, China, ²MR Scientific Marketing, SIEMENS Healthineers, Shanghai, China

Noninvasive identification of significant liver fibrosis in chronic hepatitis B patients is of great value because it can be an important indication for anti-viral therapy according to EASL guideline. This abstract was to evaluate the diagnostic capability of variable flip angle native T1 mapping combined with liver stiffness measurement (LT1 model) in identifying significant liver fibrosis in chronic hepatitis B patients. The LT1 score had good sensitivity and specificity for identifying significant liver fibrosis in chronic hepatitis B patients, and could provide a reliable basis for clinical diagnosis and treatment.

Petros Martirosian¹, Cecilia Zhang², Martin Schwartz^1,3, Thomas Benkert⁴, and Fritz Schick^1
1Section on Experimental Radiology, University Hospital of Tübingen, Tübingen, Germany, ²Department of Diagnostic and Interventional Radiology, University Hospital of Tübingen, Tübingen, Germany, ³Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Germany, ⁴MR Application Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany

Magnetization prepared 3D spiral UTE sequences were developed for T1, T2, T1rho and MTR measurements of fibrous structures. The robustness of the parameter mapping for tendons, ligaments, menisci, cartilage and muscle of the human knee joint was evaluated in a test-retest repeatabilty study. Multiparametric UTE imaging was successfully performed for both test and retest examination. The results of the study demonstrate good repeatability of the applied multiparametric protocol. Parameter maps such as T2 and T1rho show less robustness than T1 and MTR measurements. Especially with small structures as tendons and ligaments, there is the least agreement between scan and rescan.

Nicholas Bryden¹, Christian T McHugh¹, Michele Kelley¹, and Rosa T Branca^1
1University of North Carolina Chapel Hill, Chapel Hill, NC, United States

We provide superparamagnetic iron oxide longitudinal relaxivity measurements at both high (11.7 T) and low (0.6 – 2.1 mT) magnetic field strengths, for both ¹H and hyperpolarized ¹²⁹Xe nuclei. These measurements show significant increase in relaxivity at low field for both nuclei. We also provide some preliminary in vivo results for hyperpolarized ¹²⁹Xe that suggest a depolarization mechanism similar to that of SPIONs from the hemoglobin found in whole blood.

Bruno Madore¹, Michael Jerosch-Herold¹, Jr-Yuan George Chiou¹, Cheng-Chieh Cheng², Srinivasan Mukundan¹, Jeffrey Guenette¹, and Georgeta Mihai^1
1Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, ²Computer Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan

Although many methods already exist to map T₁, T₂ and M₀, these often involve special sequences not readily available on clinical scanners and/or may require long scan times. In contrast, the proposed method can run on most scanners, it offers flexible tradeoffs between scan time and image quality, and it generates spatially-aligned parameter maps. Validation was performed in gel phantoms with varying concentrations of contrast agents, and in vivo examples are presented from three neuroradiology patients. Compared to other quantitative mapping methods, the present method is meant to stand out in terms of its practicality and availability.

Hannah E. Alderson^1,2 and Mark D. Does^1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Nashville, TN, United States

This study investigated the orientation dependence of myelin water fraction (MWF) as evaluated with a 3D multiple-spin echo sequence (MSE). MSE and diffusion tensor scans were acquired at 7-T from two excised rat brains at three different orientations with respect to the main magnetic field. Region of interest analysis of the corpus callosum and the internal capsule revealed that there is no clear orientation dependency for MWF in these white matter tracts. This result is also evidenced by the minimal orientational modulation of the T₂ spectra for both ROIs across both brains. 

Malte Brammerloh^1,2, Evgeniya Kirilina^1,3, Renat Sibgatulin⁴, Karl-Heinz Herrmann⁴, Tilo Reinert^1,5, Carsten Jäger^1,6, Primož Pelicon⁷, Kerrin J. Pine¹, Primož Vavpetič⁷, Andreas Deistung⁸, Markus Morawski⁶, Jürgen R. Reichenbach⁴, and Nikolaus Weiskopf^1,5
1Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ²Leipzig University, Leipzig, Germany, ³Center for Cognitive Neuroscience Berlin, Freie Universität Berlin, Berlin, Germany, ⁴Medical Physics Group, Institute of Diagnostic and Interventional Radiology, University Hospital Jena, Jena, Germany, ⁵Felix Bloch Institute for Solid State Physics, Leipzig University, Leipzig, Germany, ⁶Paul Flechsig Institute of Brain Research, Leipzig University, Leipzig, Germany, ⁷Department for Low and Medium Energy Physics, Jožef Stefan Institute, Ljubljana, Slovenia, ⁸6University Clinic and Outpatient Clinic for Radiology, University Hospital Halle (Saale), Halle (Saale), Germany

MRI holds high promise to diagnose Parkinson’s disease (PD) at clinical field strength B0. However, it remains unclear which B0 optimizes T2* contrast in substantia nigra, which provides high diagnostic accuracy. We used quantitative MRI at B0=1.5T-9.4T, MR microscopy, and histochemistry to characterize the field dependence of the major contributors to R2* (1/T2*): dopaminergic neurons, ferritin, and myelin. R2* maps were similar at B0=3T-9.4T, and all contributions scaled approximately linearly with B0. Hence, the contrast mechanisms are similar across currently available MRI field strengths in vivo, which informs the design of novel PD biomarkers.

Jonathan Doucette^1,2, Manuel Bauer^1,3, Lara Bartels^1,2, Alexander Jaffray^1,2, and Alexander Rauscher^1,2,4,5
1UBC MRI Research Centre, Vancouver, BC, Canada, ²Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada, ³Institute for Physical Chemistry, Albert-Ludwigs-University, Freiburg, Germany, ⁴Radiology, University of British Columbia, Vancouver, BC, Canada, ⁵Pediatrics, University of British Columbia, Vancouver, BC, Canada

The MRI signal in white matter tissue is composed of constituent signals from two different water pools: intra/extracellular water and myelin water. When using a multi spin-echo acquisition, the relaxation rate measured in each pool has been shown to depend on the orientation of the containing white matter fibre with respect to the main magnetic field. Here, we show an additional influence of the acquisition echo spacing on the apparent intra/extracellular rate relaxation rate, and using numerical simulation, we provide evidence that decoherence mediated by diffusion through local field inhomogeneities created by blood vessels cannot explain the observed orientation dependence.

Mohsine Mekhfi ¹, Aimé Labbé ¹, Dimitri Kereselidze¹, Erwan Selingue ², Lionel Broche³, Anne-Laure Rollet ⁴, and Marie Poirier-quinot^1
1Université Paris Saclay, CEA, CNRS, Inserm, Laboratoire d’Imagerie biomédicale multimodale Paris Saclay (BioMaps), Orsay, France, ²Université Paris-Saclay, CEA, CNRS, Baobab, NeuroSpin, Gif-sur-Yvette, France, ³Aberdeen Biomedical Imaging Centre, University of Aberdeen, Foresterhill, AB25 2ZD, Aberdeen, UK, Aberdeen, Scotland, ⁴Laboratoire PHysico-chimie des Electrolytes et Nanosystèmes InterfaciauX, PHENIX, Sorbonne Université, CNRS, Paris, France

Measuring whole blood relaxation time is as a reliable diagnosis tool. Usually, one compartmental model is used to fit data, which seems a very simplistic approach considering the complexity of blood. The aim of this work is to test the validity of this assumption by studying the relaxation rate of whole blood, plasma and red blood cells (rbc) of rats at different temperatures. The whole blood is well described by a two-compartment approach, one corresponding to plasma and another for red blood cells. Once frozen, there is only one relaxation rate population, which is considered to be the rbc population.