Muhammad Sulaiman Sarwar^1,2, Antoine Vallatos^1,3, Cher Hon Lau⁴, Adam Waldman^1,3, Simone Dimartino², and Michael J Thrippleton^1,3
1Centre for Clinical Brain Sciences, The University of Edinburgh, Edinburgh, United Kingdom, ²Institute for Bioengineering, The University of Edinburgh, Edinburgh, United Kingdom, ³Edinburgh Imaging, The University of Edinburgh, Edinburgh, United Kingdom, ⁴Institute for Materials and Processes, The University of Edinburgh, Edinburgh, United Kingdom

Difficulties in engineering accurate biomimetic phantoms make it challenging to validate MRI models. This is particularly true for quantitative vascular permeability measurements using dynamic contrast-enhanced (DCE-) MRI, where no robust controllable phantoms are available for validating novel techniques and harmonising multicentre results. We developed 3D-printed biomimetic vascular permeability phantoms with controllable properties and assessed their ability to interrogate common DCE model quantification approaches. Parameters such as blood flow, vascular permeability, plasma volume and extravascular volume were reproduced by adapted 3D-printed material and flow circuit properties. The resulting phantoms were shown to reproduce realistic DCE-MRI signals observed clinically.

Fenglei Zhou^1,2, Fei Gao³, Longji Xu³, Jing Yang³, Fuxin Ren³, Weibo Chen⁴, and Geoff JM Parker^1,5
1Centre for Medical Image Computing, University College London, London, United Kingdom, ²School of Pharmacy, University College London, London, United Kingdom, ³Department of Radiology,Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China, ⁴Philips Heathcare, Shanghai, China, ⁵Bioxydyn Limited, Manchester, United Kingdom

Brain diffusion tensor imaging (DTI) measurements are sensitive to pathological changes, but in order for them to be of greatest use it is vital to understand intra-scanner and inter-scanner variations in DTI metrics. Here we demonstrate a physical phantom with variable pore sizes and fibre orientation that can be used to assess the repeatability and reproducibility of DTI measurements across scanners and protocols and present its application in assessing 9 separate scanner/protocol combinations.

Velencia Witherspoon¹, Michal Komlosh^1,2,3, Dan Benjamini^1,2,3, Peter Basser^1,3, and Nick Lavrik^4
1Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States, ²Center for Neuroscience and Regenerative Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States, ³The Henry M. Jackson Foundation for the Advancement of Military Medicine (HJF), Bethesda, MD, United States, ⁴The Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL), Oakridge, TN, United States

Microscopically anisotropic but globally isotropic DTI MRI phantom was designed and fabricated using a 2 Photon Nanoscribe 3D Printer. The capillary array blocks were measured aligned and randomly oriented to determine the ability of ddPFG and DTI to characterize local anisotropy in a globally isotropic system. These experiments combined computational methods can provide MRI phantoms that can be employed to validate novel or proposed microstructure imaging experiments.

Weronika Mazur^1,2, Anna Stefańska-Bernatowicz², Ewa Stodolak-Zych³, and Artur Tadeusz Krzyżak^2
1Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Kraków, Poland, ²Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Kraków, Poland, ³Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Kraków, Poland

Anisotropic hydrogels has been attracting attention for biomedical purposes. These highly-hydrated materials have potential for tissue-mimicking and then, may serve for advanced medical imaging studies. In the work, we present two types of anisotropic hydrogels  made from sodium alginate (NA) and polyvinyl alcohol (PVA) in the form of fiber bundle- a single component for larger phantom. We investigated their potential for diffusion-weighted imaging. NA-based phantoms are characterized by highly uniform diffusivity distribution, even higher then water. Single component turned out to be insufficient for the accurate quantification of the microstructure. PVA-based phantom exhibited desirable diffusion properties for tissue-mimicking.

Victor Fritz¹, Petros Martirosian¹, Jürgen Machann^1,2, and Fritz Schick^1,2
1Department of Diagnostic and Interventional Radiology, University of Tuebingen, Germany., Section on Experimental Radiology, Tuebingen, Germany, ²Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich at the University of Tuebingen, Tuebingen, Germany

The aim of this work was to systematically investigate whether lecithin is suitable for the construction of a diffusion phantom that covers and simulates ADC-values occurring in human tissue. For this, aqueous solutions of different lecithin concentrations (0%-10%) were prepared and measured by DWI. The presented results showed that lecithin is a suitable agent for simulating a wide variety of ADC-values. Even low concentrations showed a strong decrease in the ADC-value of water. However, with increasing concentration, lecithin also showed a strong influence on T2, so that ADC and T2 cannot be set independently from one another in lecithin-based phantoms.

Alexis Brullé¹, Anas Bachiri¹, Christophe Destrieux², Gilles Wiber³, Thierry Delzescaux ⁴, Ivy Uszynski¹, and Cyril Poupon^1
1BAOBAB/NeuroSpin, Université Paris-Saclay, CNRS, CEA, Gif-sur-Yvette, France, ²iBrain U1253, Université de Tours, CHU Bretonneau, INSERM, Tours, France, ³DSSI, DIF, DAM, CEA, Bruyères-le-Châtel, France, ⁴LMN, MIRCen, Université Paris-Saclay, CNRS, CEA, Fontenay-aux-Roses, France

In this work, we demonstrate that the MEDUSA simulator can be used to create huge collections of brain white matter tissue microstructure samples in the frame of large-scale HPC simulation campaigns and how these Big Data could serve the design of novel computational models able to decode white matter microstructure.

James Rice^1,2, Ruiqi Geng^2,3, Diego Hernando^2,3,4,5, and Alejandro Roldan-Alzate^1,2
1Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, United States, ²Radiology, University of Wisconsin-Madison, Madison, WI, United States, ³Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ⁴Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, United States, ⁵Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States

A major limitation of standard diffusion-weighted imaging (DWI) in the various organs, including the liver, is the presence of artifacts, bias, and poor reproducibility resulting from physiologic cardiovascular-induced motion. Recent efforts to develop motion-robust DWI sequences show promise, but there is an important unmet need for highly controlled validation in motion phantoms. This study presents the fabrication of an anthropomorphic liver flow phantom that can produce compressive motion in the liver to generate and control artifact seen in DW images. This phantom may enable improved validation of motion-robust DWI and other motion-robust applications.

Teemu Tuomainen¹, Antti Paajanen¹, and Mikko J. Nissi^1,2
1Department of Applied Physics, University of Eastern Finland, Kuopio, Finland, ²Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland

Increasing availability and affordability of 3-D printers utilizing fused deposition modeling (FDM) have enabled their widespread use especially in pre-clinical MRI, allowing in-house design and manufacturing of elaborate coil housings, animal holders, sample holders, etc. Here, we investigated ten common and broadly available FDM polymers for their MRI-visibility at 9.4T. We utilized ultra-short echo time imaging sequences, specifically, single-point-imaging (SPI) and multi-band SWIFT to measure the relaxation properties of the different polymers. The findings support the selection of appropriate printing materials when either visibility or invisibility for ultra-short echo time imaging is required.

Alex Barrett¹ and Marc Rea^1
1Medical Physics, Clatterbridge Cancer Centre NHS Foundation Trust, Liverpool, United Kingdom

Distortion in MRI can have a significant impact on diagnosis and radiotherapy treatment planning. We have 3D printed a large, low cost phantom that we used along with a CT ground truth to measure 6 MR scanners geometric accuracy. We found significantly more distortion for the 3T and mobile scanners tested which we conclude means they would require a more careful evaluation of distortion if they are to be used for radiotherapy applications and that care should be taken for all scanners where specialist radiotherapy applications such as stereotactic radiosurgery are used.

Laura Biagi^1,2, Paolo Cecchi², and Michela Tosetti^1,2
1Laboratory of Medical Physics and Magnetic Resonance, IRCCS Stella Maris, Pisa, Italy, ²Imago7 Research Foundation, Pisa, Italy

The European Standard IEC 62464-1:2018 [1] describes the methodologies to carry out acceptance and constancy tests of an MR scanner. Its come into effect extends its applicability in the range of ultra-high field (UHF) tomographers. Here, we present a protocol, with an effective time of acquisition of about 11 hours, developed for the testing of a 7T MR system, in order to address all the requirements of the standard for the evaluation of essential image quality parameters. The protocol provided for the test of two different coil configurations, using proper phantoms.

Shanshan Shan^1,2, Paul Liu^1,2, David Waddington^1,2, Bin Dong², Mingyan Li³, Fangfang Tang³, Gary Liney², Feng Liu³, Paul Keall^1,2, and Brendan Whelan^1
1ACRF Image X Institute, University of Sydney, Sydney, Australia, ²Ingham Institute For Applied Medical Research, Sydney, Australia, ³School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Australia

MRI-Linac systems require high fidelity geometric information to localize and track tumors during radiotherapy treatments. B0 field inhomogeneity causes image distortions and can provide inaccurate tumor anatomy. Here, we develop a high-order spherical harmonic method to correct for B0 inhomogeneity induced geometric distortions. Experimental data acquired from a 1T open bore MRI-Linac was used to validate the proposed method.

Juliane Peter^1,2, Sebastian Gantz^1,2, Leonhard Karsch^1,2, Jörg Pawelke^1,2, and Aswin Hoffmann^1,2,3
1OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, ²Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany, ³Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany

MRI-based proton beam visualisation in water has proven feasible in exploratory irradiation experiments performed on a first research prototype in-beam MRI system. Beam-induced convection was hypothesised to be implicated into MR signal loss observed within the beam volume. In this study, this hypothesis was tested in liquid water-filled phantoms by suppression of convection-induced motion using mechanical barriers and temperature control of water expansivity. In absence of convection-induced motion, no beam-induced signal changes occurred, supporting the hypothesis that convection triggers local MR signal loss during proton beam irradiation. The elucidation of the exact mechanism of convection-induced signal loss requires further investigation.