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Florian Kroh^1,2, Philip S. Boyd¹, Nikolaus von Knebel Doeberitz³, Heinz-Peter Schlemmer^3,4, Mark E. Ladd^1,2,4, Peter Bachert^1,2, Daniel Paech^3,5, and Andreas Korzowski^1
1Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, ³Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ⁴Faculty of Medicine, University of Heidelberg, Heidelberg, Germany, ⁵Division of Neuroradiology, University Hospital Bonn, Bonn, Germany

Keywords: CEST & MT, Brain

In this study, the APT-weighted (APTw_asym) and relaxation-compensated CEST-MRI contrasts of 9 postoperative glioma patients, were analyzed for potential regional differences in gray and white matter. The purpose of this analysis was to identify the influence of the location within the brain on CEST contrasts of tumorous and healthy control tissue, respectively. For relaxation-compensated CEST (MTR_Rex), (i) differences between gray and white matter and also (ii) regional differences with a decreased contrast inside the frontal lobe were found. On the contrary, the APTw_asym was found to be independent of (i) location and (ii) comparable for gray and white matter.

Hahnsung Kim^1,2, Suhyung Park^3,4, Ranliang Hu², Kimberly B Hoang⁵, and Phillip Zhe Sun^1,2
1Emory National Primate Research Center, Emory University, Atlanta, GA, United States, ²Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States, ³3Department of Computer Engineering, Chonnam National University, Gwangju, Korea, Republic of, ⁴Department of ICT Convergence System Engineering, Chonnam National University, Gwangju, Korea, Republic of, ⁵Department of Neurosurgery, Emory University School of Medicine, Atlanta, GA, United States

Keywords: CEST & MT, CEST & MT

We proposed a new 3D EPI CEST imaging integrated with unevenly segmented RF irradiation configuration to reduce T_1w relaxation-induced signal modulation, thereby allowing for a reliable CEST effect over the whole volume. In addition, a temporal random walk with variable density (VD) CAIPI undersampling is incorporated into segmented 3D EPI for optimized random encoding in CEST imaging. The proposed pulse sequence and reconstruction framework were validated on the phantom and tumor patient.  

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Jianhua Mo¹, Xiang Xu^2,3, Andong Ma¹, Mingjun Lu¹, Xianlong Wang¹, Qihong Rui¹, Jianbin Zhu¹, Haitao Wen¹, Genyun Lin¹, Chen Zhao⁴, Linda Knutsson^3,5,6, Peter van Zijl^3,6, and Zhibo Wen^1
1Department of Radiology, Zhujiang Hospital, Southern Medical University, Guangzhou,Guangdong, China, ²BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ³Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁴Philips Healthcare, Guangzhou, China, ⁵Department of Medical Radiation Physics, Lund University, Lund, Sweden, ⁶F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

Keywords: CEST & MT, Contrast Agent, glucose

In this study, we explored the feasibility of dynamic glucose enhanced (DGE) MRI technology in the clinical application of gliomas. 20 glioma patients underwent pre-operative DGE-MRIs before clinical intervention. We observed a significant increase in DGE area under the uptake curve (AUC) signal in tumors compared to the white matter.       In some cases, we found enhancement in DGE MRI in histopathological confirmed tumor region that was not enhanced by Gd T1w MRI. These findings provide a new perspective for the further exploration and analysis of the D-glucose delivery, uptake and metabolism in brain tumors.

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Yohann Mathieu-Daudé¹, Jérémy Pépin¹, Jean-Baptiste Pérot¹, Cécile Maguin¹, and Julien Flament^1
1Université Paris-Saclay, CEA, CNRS, MIRCen, Laboratoire des Maladies Neurodégénératives, Fontenay-aux-Roses, France

Keywords: CEST & MT, CEST & MT, gluCEST and glucoCEST

Huntington’s disease (HD) is an inherited neurodegenerative disease characterized by motor, cognitive and psychiatric symptoms. As glutamate has been shown to be a potential biomarker of neurodegenerative diseases, we used Chemical Exchange Saturation Transfer imaging of glutamate (gluCEST) to map cerebral glutamate distribution in a rat model of HD. Modification of glutamate levels observed at 12 months were preceded by decrease of lactate concentration and reduced glycolytic metabolism measured glucoCEST at 4 months, suggesting early remodeling of energy metabolism during asymptomatic stage.

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Chongxue Bie^1,2,3, Peter C. M. van Zijl^1,2, Deng Mao^1,4, and Nirbhay N. Yadav^1,2
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, BALTIMORE, MD, United States, ²The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, BALTIMORE, MD, United States, ³Department of Information Science and Technology, Northwest University, Xi’an, China, ⁴Philips Healthcare, Baltimore, MD, United States

Keywords: CEST & MT, CEST & MT

Acquisition of high-resolution Z-spectra requires excessive scan times. Ultrafast Z-spectroscopy (UFZ) can obtain whole Z-spectra within one acquisition by encoding the Z-spectral dimension spatially via a gradient applied concurrently with the saturation RF pulse, significantly reducing the scanning time. Still, UFZ has had limited success in vivo due to tissue heterogeneity. Here, we developed a TS-UFZ imaging approach where both saturation gradient and its readout were applied in the slice direction, where there is minimal heterogeneity. Results show that TS-UFZ allows high spectral- and spatial-resolution imaging of CEST signals in phantoms and human brain at 3T.

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Lucia Nichelli^1,2, Christos Papageorgakis³, Mehdi Bensemain⁴, Julian Jacob^2,5, Charles Valery⁶, Patrick Liebig⁷, Moritz Zaiss⁸, Stéphane Lehéricy^1,2, and Stefano Casagranda^3
1Department of Neurosurgery, Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Pitié-Salpêtrière-Charles-Foix, Paris, France, ²Sorbonne University, ICM, Paris, France, ³Department of R&D Advanced Applications, Olea Medical, La Ciotat, France, ⁴Department of Radiology, Nancy Regional University Hospital Centre, Nancy, France, ⁵Department of Radiation-Oncology, Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Pitié- Salpêtrière-Charles-Foix, Paris, France, ⁶Department of Neurosurgery, Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Pitié- Salpêtrière-Charles-Foix, Paris, France, ⁷Siemens Healthcare GmbH, Erlangen, Germany, ⁸Department of Neuroradiology, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany

Keywords: CEST & MT, Tumor, APTw Imaging, Perfusion, Metastases, Radionecrosis, Tumor Progression

The distinction between radionecrosis and tumor recurrence is a common diagnostic dilemma, as current advanced multiparametric MRI protocols lack on accuracy. Fluid-Suppressed Amide Proton Transfer weighted (APTw) imaging has strong potentials in brain tumor post-therapeutic assessment. In this study we compare at 3T the diagnostic accuracy of Fluid Suppressed APTw with the most used advanced technique, i.e. the Leakage-Corrected relative Cerebral Blood Volume imaging obtained by DSC perfusion in 22 pre-irradiated metastases. Results show that Fluid-Suppressed APTw metrics can clearly make a distinction between these two pathologies, in contrast to Leakage-Corrected rCBV contrast.

Hye-Young Heo¹, Munendra Singh¹, Shanshan Jiang¹, and Jinyuan Zhou^1
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States

Keywords: CEST & MT, CEST & MT

Increased cytosolic mobile protein content in gliomas causes amide proton transfer (APT) hyperintensity. However, most current APT imaging protocols acquire APT-weighted images that reflect multiple contributions, including residual direct water saturation (or relaxation), semisolid macromolecular magnetization transfer contrast (MTC) asymmetry, and nuclear Overhauser enhancement (NOE) effects, thus limiting the assessment of clean APT. Herein, we separated water, MTC, and APT signal components from RF saturated signals using an MR fingerprinting sequence and evaluated the contributions to the saturation signal at 3.5 ppm in the Z-spectrum of brain tumors.

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Patrick Schuenke¹, Felix Frederik Zimmermann¹, Kerstin Kaspar¹, Moritz Zaiss², and Christoph Kolbitsch^1
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, ²Institute for Neuroradiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany

Keywords: CEST & MT, Data Processing

CEST MRI provides a contrast sensitive to exchange processes between solute and water protons that was proven to add value in clinical MRI. However, the contrast is susceptible to B₀- and B₁ field inhomogeneities as well as the T₁ relaxation time. Here we present an analytical solution for a modified WASABI method that enables the quantitative mapping of all three parameters simultaneously from a single CEST-like MRI scan. We show that the generated parameter maps and reference maps match well and demonstrate their applicability for the B₀, B₁ and T₁ correction of CEST MRI data.

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Patrick Schuenke¹, Kai Herz^2,3, Zhongliang Zu⁴, Nirbhay Yadav^5,6, Qing Zeng^5,6, Markus Huemer⁷, Rudolf Stollberger⁷, Jiadi Xu^5,6, Kexin Wang^5,8, Feriel Romdhane⁹, Dario Livio Longo⁹, Or Perlman¹⁰, Peter C.M. van Zijl^5,8, and Moritz Zaiss^11
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, ²Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ³Department of Biomedical Magnetic Resonance, University of Tuebingen, Tuebingen, Germany, ⁴Department of Radiology, Vanderbilt University Medical Center, Nashville, TN, United States, ⁵FM Kirby Research Center, Kennedy Krieger Institute, Baltimore, MD, United States, ⁶Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁷Institut of Bioimaging, Graz University of Technology, Graz, Austria, ⁸Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ⁹Institute of Biostructures and Bioimaging (IBB), National Research Council of Italy (CNR), Torino, Italy, ¹⁰Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States, ¹¹Institute for Neuroradiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany

Keywords: CEST & MT, Simulations, validation, comparison

Quantitative CEST approaches can provide access to the exchange rate and solute concentration of exchange processes of interest. However, differences in the implementation of underlying Bloch-McConnell simulations will lead to differences in the determined quantitative parameters. Thus, we initiated a platform to compare and validate the CEST simulations from various CEST research groups. In this first comparison of continuous-wave saturation schemes, up to 5 different results for 8 compared simulations were observed. The project is still open for participation and we invite everbody to join the comparison and our planned discussions to finally realize a consensus on CEST simulations.
 

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Zhechuan Dai¹, Xingwang Yong¹, Jing Zhang², Xiaoxia Wang², Qing Li³, Yi Sun³, Ying Cao⁴, Jiuquan Zhang², and Yi Zhang^1
1Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China, ²Department of Radiology, Chongqing University Cancer Hospital, Chongqing, China, ³MR Collaborations, Siemens Healthineers Ltd., Shanghai, China, ⁴School of Medicine, Chongqing University, Chongqing, China

Keywords: CEST & MT, CEST & MT

Chemical exchange saturation transfer (CEST) imaging provides important molecular information that can reflect changes in various pathologies. However, applying CEST to lipid-rich organs, such as the breast, is technically challenging, where the lipid artifacts can grossly affect the CEST signal. In this study, we propose a novel differential analysis method with fitted magnetization transfer and lipid contributions (DIGITAL) to remove the lipid artifacts without changing the acquisition sequence. The DIGITAL method was validated on breast cancer patients, and yielded fewer lipid artifacts and better image smoothness than previous analysis-based methods.

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Keywords: CEST & MT, CEST & MT, Amide, reproducibility, brain tumor

The goal of this study was to investigate whether APT-weighted CEST imaging can provide reproducible measurements across scan sessions and scanners. Reproducibility of APT-weighted imaging in healthy brain tissue and tumors was evaluated for three CEST metrics: Lorentzian Difference (LD), magnetization transfer ratio asymmetry (MTR_asym), and relaxation-compensated inverse magnetization transfer ratio (MTR_REX).

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Jingyi Yu¹, Jian Wu¹, Xinli Lan¹, Yonggui Yang², Zhigang Wu³, Congbo Cai¹, and Shuhui Cai^1
1Department of Electronic Science, Xiamen University, Xiamen, China, ²Department of Radiology, The Second Affiliated Hospital of Xiamen Medical College, Xiamen, China, ³MSC Clinical & Technical Solutions, Philips Healthcare, Shenzhen, China

Keywords: CEST & MT, Machine Learning/Artificial Intelligence

Chemical exchange saturation transfer (CEST) quantification is mostly based on pixel-wise fitting of Z-spectra, which is time-consuming and noise-sensitive. Herein, we propose an approach to quantify CEST based on U-Net. The proposed method can simultaneously quantify the concentration and the exchange rate of nuclear Overhauser enhancement (NOE), together with the B₀ map. The results of a simulation sample and a rat C6 glioma model suggest that the quantification of NOE effect with U-Net is accurate, precise and fast.

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Clemens Stilianu¹, Markus Huemer¹, Christina Graf¹, Clemens Diwoky², Armin Rund³, Moritz Zaiss^4,5, and Rudolf Stollberger^1
1Institute of Biomedical Imaging, Graz University of Technology, Graz, Austria, ²Institute of Molecular Biosciences, University of Graz, Graz, Austria, ³Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria, ⁴Department High-field Magnetic Resonance, Max Planck Institute Tübingen, Tübingen, Germany, ⁵Institute of Neuroradiology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany

Keywords: CEST & MT, CEST & MT, Spin lock, CESL

The exchange weighting and robustness to B₀-inhomogeneities are essential properties for accurate CEST-MRI saturation measurements. Therefore, we investigated these properties for a new numerical optimized saturation pulse train and for state-of-the-art saturation pulse strategies in simulation and phantom measurements. We have found that the optimized pulse train generates superior CEST contrast and has very high stability against B₀-inhomogenities while maintaining the natural shape at the water peak which improves CEST-spectrum fitting and B₀-correction.

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Huan Minh Luu¹ and Sung-Hong Park^1
1Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea, Republic of

Keywords: CEST & MT, Quantitative Imaging

Most quantitative magnetization transfer imaging (qMT) protocols require additional T1 mapping scan. A recent on-resonance multiple phase-cycle bSSFP method was proposed for qMT that obviates the necessity for T1 mapping, but the fitting results were suboptimal. In this study, we proposed a physics-informed artificial neural network (ANN) to improve the fitting of this method. By using the MR signal model to generate the training data and regularize the network, no in-vivo data acquisition was necessary. Experiments on digital phantom and in-vivo data demonstrated improvement over previous method and better resilience against measurement noise.

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David Leitão¹, Daniel West¹, Raphael Tomi-Tricot^2,3, Jo Hajnal^1,3, Tobias C Wood⁴, and Shaihan Malik^1,3
1Biomedical Engineering & Imaging Sciences, King's College London, London, United Kingdom, ²MR Research Collaborations, Siemens Healthcare, Frimley, United Kingdom, ³Centre for the Developing Brain, King's College London, London, United Kingdom, ⁴Department of Neuroimaging, King's College London, London, United Kingdom

Keywords: Magnetization transfer, Magnetization transfer, Low-Field MRI

We used multiband pulses to obtain Magnetization Transfer (MT) weighted images at 0.55T in a time-efficient manner. White Matter (WM)/Grey Matter (GM) contrast is compared across several flip-angles for both GRE and bSSFP sequences. GRE showed larger MTR WM/GM difference but after accounting for signal-to-noise ratio bSSFP had 50% better contrast-to-noise ratio.