Fatemeh Adelnia^1,2, Zhongliang Zu^1,2, Feng Wang^1,2, Saikat Sengupta^1,2, Kevin D Harkins^1,2, and John C Gore^1,2,3
1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ³Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

R_1ρ dispersion over a range of weak locking fields has the potential to reveal information on microvascular geometry and density based on diffusion effects. Using an efficient protocol for data acquisition and theoretical fits to a simple model we present estimates of novel parameters derived from R_1ρ dispersion measurements that are in the range expected for microvasculature structure. Our in vivo results support the application of R_1ρ dispersion at low locking fields in human studies. However, further validation such as ex vivo studies need to be performed.

Véronique Fortier^1,2 and Ives R. Levesque^2,3
1Medical Imaging, McGill University Health Center, Montreal, QC, Canada, ²Medical Physics Unit, McGill University, Montreal, QC, Canada, ³Research Institute of McGill University Health Center, Montreal, QC, Canada

The impact of the fat fraction in fat-water mixtures on the fat and water T₁s is an open question, with variable observations reported in phantoms, in vivo in bone marrow, and in liver. This work investigated variations of fat and water T₁ as a function of fat content in phantoms in the presence of a water relaxation enhancing agent (MnCl₂). Fat fraction and MnCl₂ impacted both the water and fat T₁s, in different ways. Our observations may shed light on variable trends of fat and water T₁ as a function of fat content reported in the literature.

Muhamed Barakovic^1,2,3,4, Marco Pizzolato^4,5, Cristina Granziera^1,2, Jean-Philippe Thiran^4,6,7, Derek K. Jones^3,8, and Erick Jorge Canales-Rodríguez^4
1Translational Imaging in Neurology (ThINk) Basel, Department of Biomedical Engineering, University Hospital Basel and University of Basel, Basel, Switzerland, ²MS Center and Research Center for Clinical Neuroimmunology and Neuroscience Basel, University Hospital Basel and University of Basel, Basel, Switzerland, ³Cardiff University Brain Research Imaging Centre, Cardiff University, Cardiff, Wales, United Kingdom, ⁴Signal Processing Laboratory 5 (LTS5), École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁵Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kgs. Lyngby, Denmark, ⁶Radiology Department, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland, ⁷Centre d’Imagerie Biomédicale (CIBM), EPFL, Lausanne, Switzerland, ⁸Mary MacKillop Institute for Health Research, Faculty of Health Sciences, Australian Catholic University, Melbourne, Australia

The main limitation of current axon diameter mapping techniques is that the diffusion MRI (dMRI) signals from axons smaller than 2.0 μm are practically undistinguished from each other, even for the most advanced human scanners. Consequently, there is a resolution limit for the in vivo estimation of axon diameters from dMRI data. Therefore, it would be desirable to find another source of MRI contrast sensitive to the axonal calibre. This proof-of-concept study used a surface-based relaxation model to investigate whether the intra-axonal T₂ estimated in a human brain is related to the inner axon radius measured from histological data.

Junghun Cho¹, Jinwei Zhang², Pascal Spincemaille¹, Hang Zhang², Thanh D. Nguyen¹, Ajay Gupta¹, and Yi Wang^1,2
1Radiology, Weill Cornell Medicine, New York, NY, United States, ²Biomedical Engineering, Cornell University, Ithaca, NY, United States

Quantitative mapping of oxygen extraction fraction (OEF) is critical to evaluate brain tissue viability and function in neurologic disorders. An integrated model of QSM and qBOLD (QSM+qBOLD or QQ) has been developed to map OEF from a routine gradient echo MRI without the need for vascular challenges, and QQ inversion can be obtained using deep learning. This study proposes a multi-echo complex QQ (mcQQ) that improves fidelity to data noise characteristics using complex domain. The proposed mcQQ provided more accurate OEF in simulation and an improved sensitivity to OEF abnormalities in ischemic stroke patients, compared to the current QQ method.

Rolf F Schulte¹, Carolin M Pirkl¹, Pablo Garcia-Polo², Matteo Cencini^3,4, Michela Tosetti^3,4, Luis Marti-Bonmati⁵, and Marion I Menzel^1,6
1GE Healthcare, Munich, Germany, ²GE Healthcare, Madrid, Spain, ³IRCCS Stella Maris, Pisa, Italy, ⁴IMAGO7 Foundation, Pisa, Italy, ⁵Hospital Universitario y Politécnico La Fe, Valencia, Spain, ⁶Technische Hochschule Ingolstadt, Ingolstadt, Germany

Quantitative MRI offers diagnostic insights into tissue and enables characterisation of diseases, while reducing variability between operators, sites and vendors. A stack-of-stars sequence using Quantitative Transient State Imaging (QTI) was optimised and implemented to map T1, T2 and Proton Density in human prostates. Resulting in vivo multi-parametric maps were of high quality, while validation in the NIST phantom show good agreement with T1 and T2 reference values.

Simona Baroni¹, Valeria Bitonto¹, Maria Rosaria Ruggiero¹, Alessandra Pittaro², isabella Castellano², Riccardo Bussone³, Lionel M. Broche⁴, David J. Lurie⁴, Silvio Aime^1,5, and Simonetta Geninatti Crich^1
1Department of Molecular Biotechnology and Health Sciences - Molecular Imaging Center, University of Turin, Torino, Italy, ²Department of Medical Sciences, University of Turin, Torino, Italy, ³Breast Unit, Ospedale Cottolengo, Torino, Italy, ⁴University of Aberdeen, Aberdeen, United Kingdom, ⁵IRCCS SDN, Napoli, Italy

A new methodology, based on low field NMR relaxometry, has been employed to characterize breast tumour tissue and to tackle the important clinical need for the assessment of tumour margins during breast-conserving surgery. The method relies on the acquisition of proton longitudinal relaxation rate at low magnetic field strengths which are affected by the changes in the composition of the mammary gland tissue occurring during the development of neoplasia. A sensitivity, specificity, and accuracy of 92%, 85%, and 89%, respectively, were achieved. The information obtained has the potential to support the surgeon in real-time margin assessment.

Jonathan K. Stelter^1,2, Christof Boehm¹, Stefan Ruschke¹, Kilian Weiss³, Maximilian N. Diefenbach¹, Mingming Wu¹, Tabea Borde¹, Marcus R. Makowski¹, Eva M. Fallenberg¹, and Dimitrios C. Karampinos^1
1Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany, ²Department of Physics, Technical University of Munich, Garching, Germany, ³Philips Healthcare, Hamburg, Germany

A water- and fat-suppressed sequence is typically used to verify the integrity of silicone breast implants. The feasibility of using chemical shift encoding-based MRI for in vivo water–fat–silicone separation was recently shown. In this work, a hierarchical multi-resolution graph-cut framework is developed and proposed for water–fat–silicone separation in breast MRI. Robustness and competitive processing times are achieved by performing graph-cuts using varying spatial resolution. Results show successful water–fat–silicone separation for 4 echoes (the minimum of required echoes) without water–fat–silicone swaps and an improved silicone contrast compared to the conventional sequence.