Olivier M. Girard^1,2, Lucas Soustelle^1,2, Thomas Troalen³, Andreea Hertanu^1,2, Arash Forodighasemabadi^1,2,4,5, Maxime Guye^1,2, Jean-Philippe Ranjeva^1,2, Gopal Varma⁶, David C. Alsop⁶, and Guillaume Duhamel^1,2
1Aix Marseille Univ, CNRS, CRMBM, Marseille, France, ²APHM, Hôpital Universitaire Timone, CEMEREM, Marseille, France, ³Siemens Healthcare SAS, Saint-Denis, France, ⁴Aix-Marseille Univ, Université Gustave Eiffel, LBA, Marseille, France, ⁵iLab-Spine International Associated Laboratory, Marseille - Montreal, France, ⁶Division of MR Research, Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

Inhomogeneous Magnetization Transfer (ihMT) MRI has raised interest for myelin imaging. Applications at ultra-high field are appealing for SNR considerations but are challenged by the reduction of available RF power due to regulatory SAR constraints and the need to account for inhomogeneities of the RF excitation field (B₁⁺). In the current study we present experimental data acquired at 3T which validate two B₁⁺-bias removal strategies. Then we further evaluate them at 7T and show preliminary results towards a robust ihMT protocol free from B₁⁺ bias.

Pietro Bontempi^1,2, Ilana R. Leppert³, Simona Schiavi^1,4, Jennifer S. W. Campbell³, Mark Nelson^3,5, Bruce G. Pike⁶, Christine L. Tardif^3,5,7, and Alessandro Daducci^1
1Department of Computer Science, University of Verona, Verona, Italy, ²Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy, ³McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, QC, Canada, ⁴Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, Genova, Italy, ⁵Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada, ⁶Hotchkiss Brain Institute and Departments of Radiology and Clinical Neuroscience, University of Calgary, Calgary, AB, Canada, ⁷Department of Biomedical Engineering, McGill University, Montreal, QC, Canada

Magnetization Transfer (MT) imaging is a MR technique that sensitizes image contrast to protons bound to macromolecules such as protein and lipids. Using an innovative sequence that combines MT and diffusion- imaging, and Convex Optimization Modeling for Microstructure Informed Tractography (COMMIT), a method that allows estimation of bundle tissue properties, we investigate bundle specific MT ratio (MTR) values.

Hyla Allouche-Arnon¹, Olga Khersonsky², Nishanth Deva Tirukoti¹, Liat Avram³, Talia Harris³, Nirbhay N. Yadav^4,5, Sarel J. Fleishman², and Amnon Bar-Shir^1
1Department of Molecular Chemistry and Materials Science, Weizmann institute of science, Rehovot, Israel, ²Department of Biomolecular Sciences, Weizmann institute of science, Rehovot, Israel, ³Department of Chemical Research Support, Weizmann institute of science, Rehovot, Israel, ⁴Russell H. Morgan Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁵F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

Genetically engineered multicolor fluorescent proteins have changed biomedical research by enabling multiplexed mapping of transgenes expression. However, although MRI reporter genes have been developed, the ability to monitor multiple reporters that are expressed simultaneously and present them in a multicolor fashion is still needed. Here, we present an MRI-based system, comprising computationally designed reporters (enzymes) combined with MRI-detectable synthetic probes (substrates) for non-invasive color-encoded MRI mapping of transgene expression. Systemically administered reporter probes exclusively accumulate in cells expressing the designed reporter genes allowing their spatial display as pseudo-colored CEST MRI maps as demonstrated in both tumor model and viral-delivery system.

Yohann Mathieu-Daudé¹, Mélissa Vincent¹, Julien Valette¹, and Julien Flament^1
1Université Paris-Saclay, Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Molecular Imaging Research Center (MIRCen), Laboratoire des Maladies Neurodégénératives, Fontenay-aux-Roses, France

Compartmental origin of glucoCEST signal is still an ongoing debate. To address this crucial question, we propose in this study to use diffusion-weighted CEST-MRS in order to disentangle extracellular/extravascular and intracellular contributions to the glucoCEST signal. D-glucose and 2-deoxy-D-glucose were injected intravenously and kinetics of glucoCEST signal were measured over time. The comparison of kinetics acquired with and without diffusion grandients showed that 2-deoxy-D-glucose glucoCEST signal was dominated by intracellular contribution, contrarily of D-glucose. This study could constitute a major step toward glucoCEST quantification and could be beneficial for several applications, especially to study energy metabolism defects in neurodegenerative disorders.

Zheng Han^1,2, Safiya Aafreen³, Yang Zhou^1,2,4, Chongxue Bie^1,2, Jiadi Xu^1,2, Lei Zheng⁵, Peter C.M. van Zijl^1,2, and Guanshu Liu^1,2
1Radiology, Johns Hopkins University, Baltimore, MD, United States, ²F.M Kirby Research Center, Kennedy Krieger Institute, Baltimore, MD, United States, ³Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States, ⁴Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ⁵Oncology, Johns Hopkins University, Baltimore, MD, United States

Here we report a novel approach to detect non-labeled cationic compounds, named modulated saturation transfer (MOST)-MRI, based on their effect of modulating the exchange rate of surrounding exchangeable protons. MOST-MRI was able to detect polyethylenimine (PEI600, M.W. = 600 Da), at a high sensitivity (μM or μg/mL range) through its quenching effects on surrounding fast-exchanging protons. In animals, MOST-MRI detected the tumor uptake of PEI600 that was injected intratumorally at a low dose (50 μg/kg b.w.), indicating the potential of MOST-MRI for label-free imaging guidance that is needed for the development and clinical translation of cationic gene delivery systems.

DiaoHan Xiong¹, Rui Wang¹, Tao Wen¹, TieJun Gan¹, PengFei Wang¹, XinYing Ren¹, YuJing Li¹, Jing Zhang¹, and Kai Ai^2
1Lanzhou University Second Hospital, Lanzhou, China, ²Philips Healthcare, Xi'an, China

To assess the diagnostic performance of Amide Proton Transfer (APT) and Arterial Spin Labeling (ASL) for distinguishing different sub-classifications of gliomas in comparison with Diffusion Weighted Imaging (DWI). Forty patients underwent sequences including T1W enhancement, DWI, APT and 3D-pCASL. ADC_mean, ADC_mean-to-ADC_NAWM ratio, APT_mean, APT_mean-to-APT_NAWM ratio, regional cerebral blood flow (rCBF) and rCBF_mean-to-rCBF_NAWM ratio are calculated. The results showed that diagnostic accuracy of APT_mean was superior in distinguishing sub-classifications of gliomas than other parameters. We concluded that APT can be used in predicting sub-classification of gliomas based on WHO CNS5, providing more valuable supplementary information for early treatment guidance and surgery.