Andreas Georg Berg^1,2, Stefan Hengsbach³, and Klaus Bade^3
1Center for Medical Physics and Biomedical Engineering High field MR-Center, Medical University of Vienna, Vienna, Austria, ²High-Field MR-Center (MRCE), Medical Universits of Vienna, Vienna, Austria, ³Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Leopoldshafen-Eggenstein, Germany

Quality-control for systematic improvements in 3D-isotropic spatial resolution of the MR-imaging system up to the microscopic range becomes increasingly relevant not only for preclinical imaging but also for High-Field-MR human scanners. The design of a prototype phantom, comprising a set of 3D-cubes and an exemplary MR-microscopic evaluation is presented. The extraordinary challenges on accurate bar-width-to-cavity ratios for the cube range from periodicity a=128µm down to a=4µm are dealt with using 2-photon-lithography as manufacturing technology. The spatial resolution for 3D isotropic imaging can be checked qualitatively and quantitatively by interpolation of the Modulation-Transfer-Function demonstrated on a 3D-GRE sequence as an example.

Wolfgang Kilian¹, Rüdiger Brühl¹, Yasser Abdulhadi¹, and Bernd Ittermann^1
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany

Stable and well characterized anthropomorphic MR-phantoms for quantitative MRI of T1 and T2 measurements are still lacking. We investigate the potential application of additive manufacturing of silicone to produce multi-compartment MR-phantoms with well characterized relaxation properties. Various two-component silicone types with different mixture ratios were investigated. Additionally, the influence of admixing colors to modulate relaxation times was studied. First bi-phasic test samples were designed, produced by different commercial 3D printing sources, and characterized.

Adriano Troia¹, Umberto Zanovello¹, Luca Zilberti¹, Matteo Cencini², Michela Tosetti^2,3, David Kilian⁴, Martina Capozza⁵, Wolfgang Kilian⁶, and Tuğba Dışpınar Gezer^7
1INRIM, Turin, Italy, ²IRCCS Stella Maris, Pisa, Italy, ³IMAGO7 Foundation, Pisa, Italy, ⁴Centre for Translational Bone, Joint and Soft Tissue Research, Faculty of Medicine and University Hospital TUD, Dresden, Germany, ⁵Department of Molecular Biotechnology and Health Sciences UNITO, Turin, Italy, ⁶Physikalisch-Technische Bundesanstalt, Braunschweig, Germany, ⁷National Metrology Institute, TUBITAK, Istanbul, Turkey

Anthropomorphic phantoms for MRI imaging are rapidly evolving also thanks to the increase of 3D printing technologies. Their realization may represent an important support for the implementation of advanced quantitative imaging technique such as Magnetic Resonance Fingerprinting (MRF)or Electrical Properties Tomography (EPT). Even if formulations of gel based tissue-mimicking materials have been widely explored, generally they lacked in achieving the simultaneous tuning of electrical and relaxation properties of the mimicked tissues. In this study, customized moulds of white and grey matter are combined to realize brain-like gel phantoms in which relaxation times, conductivity and permittivity have been measured.

Christoph Leuze¹, Supriya Sathyanarayana¹, Bruce L Daniel¹, and Jennifer A McNab^1
1Radiology, Stanford University, Stanford, CA, United States

We present a method for alignment of augmented reality display of brain MRI with the patient’s real-world head with potential applications to an AR-neuronavigation system that relies on a see-through display.

Philip Meng-en Lee¹, Hsin-Yu Chen¹, Jeremy W Gordon¹, Zihan Zhu¹, Peder EZ Larson¹, Nicholas Dwork¹, Mark Van Criekinge¹, Lucas Carvajal¹, Michael A Ohliger¹, Zhen J Wang¹, Duan Xu¹, John Kurhanewicz¹, Robert A Bok¹, Rahul Aggarwal², Pamela N Munster², and Daniel B Vigneron^1
1Department of Radiology & Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Department of Medicine, University of California, San Francisco, San Francisco, CA, United States

The inhomogeneous B₁ excitation profile of ¹³C surface transmit/receive coils provides high SNR near the surface, but results in a spatially-varying B₁+. For accurately quantifying the pyruvate to lactate conversion rate (k_PL), the flip angle needs to be corrected based on the B₁ excitation profile. Simultaneously, random noise in hyperpolarized spectral data obscures peaks of downstream metabolites. In this work, we developed and tested a specialized computational pipeline incorporating denoising and a B₁ excitation field correction method that improved quantitative kinetic rate analyses of hyperpolarized ¹³C MRSI scans of liver tumor patients acquired with a T/R ¹³C surface coil.

Alexey Dimov¹, Kelly Gillen¹, and Yi Wang^1
1Radiology, Weill Cornell Medicine, New York, NY, United States

A magnetic susceptibility phantom with a large range of negative to positive susceptibility values relative to water is demonstrated for validating quantitative susceptibility mapping (QSM) and related quantitative MRI techniques. The phantom consists of vials with various concentrations of paramagnetic Gadolinium contrast agent (Gd) and diamagnetic calcium chloride (CaCl2) solutions. Compared to previously reported phantoms, this phantom is easy to construct and highly stable and has minimal effects of unwanted air bubbles.

Leo Konst Marecki¹, Eric Konst Marecki¹, and Xiaoliang Zhang^1
1Biomedical Engineering, SUNY University at Buffalo, Buffalo, NY, United States

Most utilized phantoms for determining the SAR compose of a uniform material to determine the properties of each coil and the exposure time to remain below the FDA guidelines and ensure patient safety.  Accurate modeling of the tissue permittivity, conductivity, and geometry will provide more accurate methods to measure the SAR of each organ for a variety of RF coil systems.  Our results showed that utilizing 3D printed Nylon containers and Polyvinylpyrrolidone (PVP), NaCl, and water solutions can be used to model the geometry and tissue characteristics of the human knee.

Tito Körner¹, Stefan Wampl¹, Marcos Wolf¹, Martin Meyerspeer¹, Maxim Zaitsev^1,2, Wolfgang Birkfellner¹, and Albrecht Schmid^1
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany

Development of motion compensation strategies is challenging, especially when involving volunteer measurements due to high demands to subject compliance and low reproducability. In this work a human shaped torso phantom, capeable of simulating respiratory motion of a left ventricle phantom including blood flow simulation is presented. A tracking algorithm is applied in postprocessing to acquired images containing simulated respiratory motion. Comparison to motion tracking data from an external sensor show good agreement proving the setup to be an environment with high reproducability and hence ideal for the purpose to develop and evaluate motion compensation strategies. 

Rita Schmidt^1,2, Ghil Jona³, and Edna Furman-Haran^2,3
1Neurobiology, Weizmann Institute of Science, Rehovot, Israel, ²The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel, ³Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel

Moving to ultra-high fields (≥7T), the inhomogeneity of both RF and static magnetic fields increases, which motivates to design a realistic head-shaped phantom. In this study, a 3D-printed head-shaped phantom with brain mimicking metabolites and lipid layer examined for 7T MRI and MRSI. The phantom was designed to resemble the brain with respect to B₀ and B₁ distributions, metabolites and lipid layer. We examined it for ¹H MRS and MRSI, especially in the lipid layer vicinity. We also demonstrated in EPI that the Fat Suppression pulse flip angle can be optimized to minimize the lipid artifact and reduce the SAR. 

Victor Fritz¹, Petros Martirosian¹, Jürgen Machann^1,2, Rolf Daniels³, and Fritz Schick^1
1Section on Experimental Radiology, University of Tübingen, Tübingen, Germany, ²Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich at the University of Tübingen, Tübingen, Germany, ³Institute of Pharmaceutical Technology, University of Tübingen, Tübingen, Germany

The aim of this work was to develop stable and homogeneous oil-in-water emulsions for tissue simulation in MRI. For this purpose, three different emulsifiers (polysorbate 60, sodium dodecyl sulfate (SDS), and soy lecithin) were examined for their stabilizing ability. In addition, their potential impact on the MR-measurements was investigated.                       Sufficient stability can be achieved using both emulsifier, polysorbate and lecithin. Emulsions stabilized by SDS showed a visually lower stability. Due to its sufficient stabilizing ability, promising relaxometric properties (r_1,lecithin=0,11wt%^-1s^-1, r_2,lecithin =0,62wt%^-1s^-1), and no additional spectral resonances, lecithin is suggested as the preferred emulsifier for use in MRI. 

Elif Aygun^1,2, Ahmet Rahmetullah Cagil^1,2, and Emine Ulku Saritas^1,2,3
1Department of Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey, ²National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey, ³Neuroscience Graduate Program, Bilkent University, Ankara, Turkey

Phantoms doped with paramagnetic materials are commonly used for quality assessment of MRI protocols and image reconstruction techniques. These phantoms are typically prepared using cylindrical containers and mimic the T₁ /T₂ characteristics of human tissue. In this work, we propose a 1:1 scale human head and neck agar-agar phantom prepared using a 3D human model. The phantom mimics human tissue characteristics while incorporating the skull and cervical vertebrae. The MRI images show that the phantom closely matches human anatomy, and the susceptibility artifacts in EPI images successfully mimic those seen during in vivo imaging of the brain and spine.

Stephen E Russek¹, Kathryn E Keenan¹, Karl F Stupic¹, Teryn S Wilkes², Ramesh Karki³, and Todor Karaulanov^4
1NIST, Boulder, CO, United States, ²Intermountain Neuroimaging Consortium, University of Colorado, Boulder, CO, United States, ³University of Colorado Anschutz, Radiological Sciences, Aurora, CO, United States, ⁴CaliberMRI, Inc., Boulder, CO, United States

Using the MRI system phantom we demonstrate the utility of the embedded MR-readable thermometer to measure and correct for temperature variations, demonstrate the use of the fiducial array to characterize scanner geometric distortions and the efficacy of software distortion corrections, and finally look at the effect of the electromagnetic properties of the phantom fill on quantitative measurements.

Endre Grøvik^1,2, Elisabeth Lysvik¹, Robin Bugge¹, Kyrre Emblem¹, Trine Hjørnevik¹, Svein-Are Vatnehol¹, and Tryggve Storås^1
1Oslo University Hospital, Oslo, Norway, ²University of South-Eastern Norway, Drammen, Norway

The proposed glymphatic system is hypothesized to be a waste-clearance system of the cerebrospinal fluid (CSF) through the perivascular and interstitial spaces of the brain. The details of this system, and its contribution to the delivery of nutrients and eliminating waste products, are yet to be established. Here we present a tailored MRI phantom to simulate the fluid dynamics of the CSF in the perivascular space. This glymphatic ultra-slow flow phantom facilitates testing of MRI flow measurements in a controlled environment, enabling optimization of MRI scan parameters to allow accurate measurements of glymphatic flow in the human brain.

Emilie Poirion¹, Corentine Marie², Marine Boudot de La Motte³, Chloé Dupont⁴, Jean-Claude Sadik¹, and Julien Savatovsky^1
1Hospital Foundation A. de Rothschild, Imaging department, Paris, France, PARIS, France, ²Sorbonne University, Paris Brain Institute, Paris, France, Paris, France, ³Hospital Foundation Rothschild,Neurology department, Paris, France, Paris, France, ⁴Hospital Foundation A. de Rothschild, Pharmaceutical department, Paris, France, PARIS, France

Gadolinium-enhanced imaging provides valuable information in clinical practice for the diagnosis of several diseases. Conventional sequences fail to detect low concentrations of gadolinium, such as those encountered in abnormal meninges. We designed a phantom containing 16 diluted gadobutrol tubes to compare and optimize sequences, based on normalized signal and contrast-to-noise ratio, for each gadolinium concentration. We performed a preliminary study comparing T1, FLAIR and FLAIR with optimized parameters on this phantom. The optimized FLAIR sequence shows an efficient detection of low concentrations, with a higher CNR than other sequences. Preliminary in-vivo experiment shows promising results for leptomeningeal abnomalities detection.

Koji Sakai¹, Yasuhiko Tachibana², Toshiaki Nakagawa³, Hiroyasu Ikeno³, Takayuki Obata², and Kei Yamada^1
1Kyoto Prefectural University of Medicine, Kyoto, Japan, ²National Institute of Radiological Sciences, Chiba, Japan, ³Kyoto Prefectural University of Medicine Hospital, Kyoto, Japan

We compared DTI measures among three different anisotropic diffusion phantoms: a commercially available astriction cotton; a glass capillary plate; a hand-bundled polyethylene fibers. The purpose of this study was to examine whether the cotton is useful as an anisotropic diffusion phantom. Differences in ADC and FA were evaluated by comparing coefficients of variation (CVs). No significant difference was seen for the largest eigen value: 2.06 - 2.14 x 10^-3 mm²/sec. Clear differences in FA were seen among the three DTI phantoms (p = 0.0079). CVs from five acquisitions for ADC and FA from every phantoms were all less than 2%.

Egor Kretov¹, Zhao Kaixuan ^1,2, Charles Grassin³, and Thoralf Niendorf^1
1Max Delbrück Center for Molecular Medicine, Berlin, Germany, ²School of Biomedical Engineering, Southern Medical University, Guangzhou, China, ³Independent Researcher, Paris, France

This work presents a cost-effective near-field RF mapping approach for accurate tracking of a field probe. The method is based on the OpenCV library. It serves as a practical tool for the rapid assessment and characterization of MR coils and arrays. The only equipment required for the setup is a field probe, a regular webcam, and a paper QR code label, which renders this technique highly accessible and easy-to-use.

Fadi Ayad¹ and Amir Shmuel^2
1Biomedical Engineering, McGill University, Montreal, QC, Canada, ²McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, QC, Canada

Head and body movements introduce artifacts in structural, diffusion, and functional MRI. With the advent of imaging at ultra-high field, head and body movements limit our capacity to obtain high-resolution, high-quality data. We have developed a small wearable device for acquiring data on head and body movements and transmitting it wirelessly to a computer for real-time analysis while a subject is trained in a mock MRI scanner. This device works in parallel to an in-bore camera used for movement detection, to support subject screening and training to remain still in preparation for MRI.

Apoorva Agarwal¹, Megha Goel¹, and Jignesh Dholakia^1
1GE Healthcare, Bengaluru, India

This study presents a new Deep-Learning (DL) based strategy for background computation in MR images. 3-plane Localizer scans have been used for background-subtraction in all subsequent scans of same MR Examination. This is accomplished by obtaining foreground-background masks for Localizer images using U-Net model and applying Image Resampling techniques on the obtained mask to compute background for subsequent scans. Comparison with existing algorithms demonstrates that proposed method prevails in accuracy, effectiveness and provides improved visual contrast. It can also be used universally across anatomies and MR pulse-sequences as opposed to other methods requiring anatomy/sequence-specific tuning and adaptive parameter adjustments.

Tomohiro Noda¹, Keitaro Sofue², Ryuji Shimada¹, Yuichiro Somiya¹, Shintaro Horii¹, Yoshiko Ueno², Naoki Yoshida¹, Yu Ueda³, Akiko Kusaka¹, and Takamichi Murakami^2
1Center of Radiology and Radiation Oncology, Kobe University Hospital, Kobe, Japan, ²Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Japan, ³Philips Japan MR Clinical Science, Tokyo, Japan

In free-breathing radial k-space sampling with KWIC reconstruction, soft gating method can be adopted to reduce motion artifacts. We investigated optimal soft gating parameters for free-breathing hepatobiliary phase MRI. A programmable respiratory motion phantom with varying motion distance of 10, 20, 30 mm was imaged using six values of soft gating factor (SGF). Image contrast and sharpness were analyzed by calculating contrast ratio (CR) and full width at half maximum (FWHM). The CR and FWHM were not inferior compared with the reference standard images in any of the motion distances when the SGF was set at more than 1.4.

Davide Cicolari¹, Domenico Lizio², Patrizia Pedrotti³, Monica Teresa Moioli², Alessandro Lascialfari¹, Manuel Mariani¹, and Alberto Torresin^2,4
1Department of Physics, University of Pavia, Pavia, Italy, ²Department of Medical Physics, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy, ³Department of Cardiology, ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy, ⁴Department of Physics, University of Milan, Milan, Italy

A method for the MRI relaxation time measurement validation and harmonization is proposed: it relies on a phantom composed of vials filled with different concentrations of MnCl₂ aqueous solutions, whose relaxation times are characterized as a function of both concentration and temperature, employing NMR techniques. The accuracy and the precision of fast mapping sequences developed for cardiac applications are better quantified through, respectively, the phantom characterization and the SD maps analysis. Scan-dependent recalibrations of the relaxation time maps can be performed relying on the ground-truth NMR values of the phantom, aiming to clinical intra- and inter-center harmonization.