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Chuanjiang Cui¹, Kyu-Jin Jung¹, Jun-Hyeong Kim¹, and Dong-Hyun Kim^1
1Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of

Keywords: Electromagnetic Tissue Properties, Electromagnetic Tissue Properties

Phase-based EPT algorithm is extremely sensitive to noise. Although various denoising algorithms have been introduced to suppress noise amplification, residual artifact cause instability conductivity error or broadening boundary artifact. In this work, we propose a novel generative network trained with Stein’s unbiased risk estimator under the purely unsupervised learning framework, which improve the performance of phase-based conductivity reconstruction algorithms. In addition, the proposed method does not need any dataset for training neural network and not require any prior information for designing explicit regularization.

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Safa Özdemir^1,2, Efe Ilicak^1,2, Lothar R. Schad^1,2, and Frank G. Zöllner^1,2
1Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany, ²Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany

Keywords: Electromagnetic Tissue Properties, Electromagnetic Tissue Properties

Magnetic Resonance Electrical Properties Tomography (MREPT) is used for obtaining conductivity by utilizing B₁ phase images. In order to obtain B₁ phase, different pulse sequences can be used. Among these, spiral trajectory based imaging has various advantages including high SNR efficiency and acquisition speed and was demonstrated in MREPT previously. In this work, to further improve spiral trajectory based imaging in MREPT, we investigate variable density sampling patterns. In vivo brain results indicate that conductivity images are quite robust with the choice of undersampling pattern and whole brain coverage can be completed under a minute with multiple averages.

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Jose E. C. Serralles¹, Ilias I. Giannakopoulos², Georgy D. Guryev¹, Luca Daniel¹, and Riccardo Lattanzi^2
1Research Laboratory of Electronics (RLE), Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ²The Bernard and Irene Schwartz Center for Biomedical Imaging (CBI), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States

Keywords: Electromagnetic Tissue Properties, Electromagnetic Tissue Properties

We propose a novel approach to electrical property (EP) estimation that also estimates the incident fields generated by a coil, by solving a basis pursuit problem. We also propose a novel Global Maxwell Tomography (GMT) formulation that uses the MR signal instead of $$$B_1^+$$$. We tested our approach experimentally by reconstructing the average EP of a homogeneous cylinder. We obtained < 5% estimation error using only $$$B_1^+$$$ data obtained from MR Fingerprinting. We then estimated the receive sensitivity maps $$$B_1^-$$$ by using the new signal-based GMT.

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Stefano Mandija^1,2, Sarah Jacobs³, Jordi Kleinloog^1,2, Hongyan Liu^1,2, Oscar van der Heide^1,2, Anja van der Kolk^1,4, Alessandro Sbrizzi^1,2, and Cornelis van den Berg^1,2
1Department of Radiotherapy, UMC Utrecht, Utrecht, Netherlands, ²Computational Imaging Group for MR Therapy and Diagnostics, UMC Utrecht, Utrecht, Netherlands, ³Department of Radiology, UMC Utrecht, Utrecht, Netherlands, ⁴Department of Medical Imaging, Radboud UMC, Nijmegen, Netherlands

Keywords: Electromagnetic Tissue Properties, Electromagnetic Tissue Properties, Conductivity

In this work, we first extend the validation of the water-content based Electrical Properties Tomography (wEPT) model from brain white matter to gray matter conductivity reconstructions in healthy volunteers. Secondly, we show that wEPT reconstructions calibrated on 10 healthy volunteers from an MR-STAT clinical trial dataset show a conductivity increase in pathological regions for 6 primary brain tumor and 9 multiple sclerosis (MS) patients from the same study. For diffuse glioma, a positive correlation between grade and conductivity is observed. For MS white matter lesions a clear conductivity increase is observed compared to healthy white matter.

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Bup Kyung Choi¹, Nitish Katoch¹, Ji Ae Park², Tae Hoon Kim³, Young Hoe Hur⁴, Jin Woong Kim⁵, and Hyung Joong Kim^1
1Department of Biomedical Engineering, Kyung Hee University, Seoul, Korea, Republic of, ²Division of Applied RI, Korea Institute of Radiological and Medical Science, Seoul, Korea, Republic of, ³Medical Convergence Research Center, Wonkwang University Hospital, Iksan, Korea, Republic of, ⁴Department of Hepato-Biliary-Pancreas Surgery, Chonnam National University Medical School, Gwangju, Korea, Republic of, ⁵Department of Radiology, Chosun University Hospital and Chosun University College of Medicine, Gwangju, Korea, Republic of

Keywords: Electromagnetic Tissue Properties, Electromagnetic Tissue Properties, Electrical Conductivity, Low-frequency conductivity, High-field MRI, Tissue properties, Cell density imaging

Conductivity measured at low-frequency can provide information on extracellular space (ECS), which will be useful in clinical applications such as tumor imaging and bioelectromagnetic modeling. Recently proposed conductivity tensor imaging (CTI) technique provides the anisotropic low-frequency conductivity distribution extracted from high-frequency conductivity measurement from the B1 map of MRI. The extracellular conductivity measured using CTI from three phantoms was compared with an impedance analyzer. The accuracy of the CTI technique was estimated to be high enough for most clinical applications.

Junting Guo¹, Lu Zhang¹, Shuo Li¹, Ding Li¹, Zhichang Fan¹, Meining Chen², Guoqiang Yang³, Yan Li³, Le Wang³, Bin Wang³, and Xiaochun Wang^3
1College of Medical Imaging, Shanxi Medical University, Taiyuan, China, ²MR Scientific Marketing, Siemens Healthcare, Shanghai, China, ³Department of Radiology, The First Hospital of Shanxi Medical University, Taiyuan, China

Keywords: Multi-Contrast, Cancer

Tumor grading is the most important single prognostic factor for bladder urothelial carcinoma. In this study, we compared 5 diffusion models for assessing low- and high-grade in bladder urothelial carcinoma, including continuous-time random-walk (CTRW), incoherent motion within the voxel (IVIM), stretched exponential model (SEM), diffusion kurtosis imaging (DKI) and fractional-order calculus (FROC). The study found that CTRW_D, DKI_Dapp, DKI_Kapp, FROC_D, IVIM_D and SEM_DDC were significantly different between low- and high-grade bladder urothelial carcinoma and could distinguish one from the other.

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Sam Keaveney^1,2, Alina Dragan¹, Julie Hughes¹, Mihaela Rata^1,2, Thomas Benkert³, Christina Messiou^1,2, Dow-Mu Koh^1,2, and Jessica M Winfield^1,2
1MRI Unit, Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, ²Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, United Kingdom, ³MR Application Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany

Keywords: Diffusion/other diffusion imaging techniques, Whole Body, Simultaneous Multi-Slice

Simultaneous multi-slice (SMS) has the potential to accelerate whole-body diffusion-weighted imaging (WB-DWI). This work presents quantitative and qualitative assessment of SMS image quality in phantoms and healthy volunteers, as a strategy to determine the optimal parameters for the clinical application of a research application SMS sequence.

An SMS factor of 2 and a moderately reduced TR did not introduce significant bias to ADC measurements. The reduction in SNR for these acquisitions was statistically, but not clinically, significant. These parameters offer time savings of up to 24% with respect to non-SMS settings and should be investigated further in a patient population.

 

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Alba Herrero Gómez¹, Marc Azagra¹, and Irene Marco Rius^1
1Institute for Bioengineering of Catalonia, Barcelona, Spain

Keywords: Molecular Imaging, New Devices

Due to its non-invasive nature, NMR has become a pillar as a diagnostic technique, as well as a support for biochemical assays and disease tracking both in vivo and in-vitro. However, due to its magnetic susceptibility, some of the materials used for tissue engineering and 3D cell modeling are incompatible with the technique, interfering with data acquisition and reducing its applications in-vitro. We developed a cryogel that could help bridge this gap between NMR and tissue engineering.

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Samuel St-Jean¹ and Markus Nilsson^1
1Clinical Sciences Lund, Lund University, Lund, Sweden

Keywords: Diffusion/other diffusion imaging techniques, Data Analysis, diffusion modeling

This work explores how to obtain parameter maps from a diffusion MRI model under 30 seconds and how to leverage multiple plausible solutions into a consensus solution using a framework similar to MR fingerprinting. The method is tested with a two compartments model and a mean kurtosis model and compared with a standard optimisation solver. Visual improvements are shown on parameter maps, showing less implausible values than the standard method, but without the use of constraints or assumptions. Access to a distribution of plausible values allows to compute most likely value from this distribution in the case of parameter degeneracies.

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Marten Veldmann¹, Luke J. Edwards², Kerrin J. Pine², Philipp Ehses¹, Nikolaus Weiskopf^2,3, and Tony Stöcker^1,4
1MR Physics, Deutsches Zentrum für Neurodegenerative Erkrankungen e.V., Bonn, Germany, ²Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ³Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany, ⁴Department of Physics & Astronomy, University of Bonn, Bonn, Germany

Keywords: Diffusion/other diffusion imaging techniques, Diffusion/other diffusion imaging techniques

We compared spiral and EPI diffusion imaging at ultra-high b-values for axon radius estimation in the white matter. For data acquisition, a custom multiband spiral sequence was combined with trajectory monitoring and higher order image reconstruction. The lower echo time of the spiral sequence led to increased relative SNR compared to EPI and improved estimation of axon radii. The resulting axon radius maps from spiral scans were more homogeneous especially in low-SNR regions. We also found, that denoising performed on complex data instead of magnitude data significantly improved axon radius estimation.

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Wei-Yue Xu¹, Qiong Li¹, Ya-Jun Hou¹, Yi-Cheng Hsu², Thomas Benkert³, Yu-Dong Zhang¹, and Xi-Sheng Liu^1
1Department of Radiology, the First Affiliated Hospital with Nanjing Medical University, Nanjing, China, ²MR Collaboration, Siemens Healthineers Ltd, Shanghai, China, ³MR Application Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany

Keywords: Diffusion/other diffusion imaging techniques, Diffusion/other diffusion imaging techniques, ZOOMit diffusion-weighted imaging

Magnetic resonance imaging has been demonstrated to be a useful tool in the preoperative diagnosis of gastric cancer. With improved imaging quality and flexible imaging orientation, ZOOMit diffusion-weighted imaging (DWI) is attracting attention in gastric tumor imaging. The stomach is a hollow organ with variable morphology. Thus, multi-orientation ZOOMit DWI imaging provides a complete view of the lesion compared with axial DWI, thus leading to more accurate preoperative staging in treatment strategy determination.

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Joseph Weygand¹, Tess Armstrong², J.M. Bryant¹, Jacqueline Andreozzi¹, Ibrahim M. Oraiqat¹, Casey L. Liveringhouse¹, Kujtim Latifi¹, Kosj Yamoah¹, James R. Costello³, Eduardo G. Moros¹, Issam M. El Naqa⁴, Arash O. Naghavi¹, Stephen A. Rosenberg¹, and Gage Redler^1
1Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, United States, ²Department of Product Development, ViewRay, Oakwood Village, OH, United States, ³Department of Radiology, Moffitt Cancer Center, Tampa, FL, United States, ⁴Department of Machine Learning, Moffitt Cancer Center, Tampa, FL, United States

Keywords: Diffusion/other diffusion imaging techniques, Radiotherapy

Diffusion weighted imaging (DWI) allows for the evaluation of tumor cellularity. Its application on a 0.35 T MRI-guided linear accelerator (MRL) would facilitate integration of this information into radiotherapy planning and potentially allow for online biologically-guided plan adaption. This study demonstrates the capability of a DWI protocol both in phantom and in vivo. In particular, it is demonstrated that quantitively accurate, repeatable, and geometrically precise ADC maps can be produced in phantom on the 0.35 T MRL. Additionally, this technique was applied in vivo on one sarcoma patient receiving same-day diagnostic diffusion scans before, during, and after radiotherapy.

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Olaf Dietrich¹, Mengfei Cai², Anil Tuladhar², Mina Jacob², Gerald Drenthen³, Jacobus Jansen^3,4, José Marques², Jens Ricke¹, Frank-Erik de Leeuw², Marco Duering⁵, and Walter Backes^3
1Department of Radiology, LMU University of Munich, Munich, Germany, ²Department of Neurology, Donders Center for Medical Neurosciences, Radboud University Medical Center, Nijmegen, Netherlands, ³Schools for Mental Health and Neuroscience (MHeNs) and Cardiovascular Diseases (CARIM), Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, Netherlands, ⁴Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, ⁵Medical Image Analysis Center (MIAC AG) and qbig, Department of Biomedical Engineering, University of Basel, Basel, Switzerland

Keywords: Diffusion/other diffusion imaging techniques, Diffusion Tensor Imaging, Intravoxel incoherent motion MRI; Model selection; Brain; Cerebral small vessel disease

The acquisition of IVIM and DTI data of the brain can be integrated into a single measurement, which offers the possibility to determine orientation-dependent (tensorial) perfusion parameters in addition to established IVIM and DTI parameters. The purpose of this study was to evaluate the feasibility of such an integrated IVIM-DTI protocol with a clinically feasible scan time below 6 minutes and to establish the maximum number of DTI and IVIM tensor parameters that can reliably be determined with this approach by comparing 17 different IVIM-diffusion models with 4 to 19 model parameters.

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Imogen Thrussell^1,2, Jessica Winfield^1,2, Sadiq Usman², Jennifer Newman², Georgina Hopkinson², Shane Zaidi^1,2, Aisha Miah^1,2, Christina Messiou^1,2, and Matthew Blackledge^1,2
1The Institute of Cancer Research, London, United Kingdom, ²The Royal Marsden NHS Foundation Trust, London, United Kingdom

Keywords: Diffusion/other diffusion imaging techniques, Diffusion Tensor Imaging, Cancer, Fractional Anisotropy, DWI, ADC

In previous studies average values of Apparent Diffusion Coefficient (ADC) have been shown to change significantly after radiotherapy in Soft-Tissue Sarcomas (STS). In this study we evaluate the Fractional Anisotropy (FA) of STS before and after treatment and demonstrate that (i) tumours can exhibit significant diffusion anisotropy, and (ii) changes in FA are inversely correlated with ADC change. Diffusion-Tensor Imaging (DTI) may therefore provide important microstructural information when interpreting change in STS after radiotherapy, and that diffusion anisotropy should be accounted for when optimising diffusion-weighted imaging (DWI) protocols for STS.

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Martin M. Pike¹, Xin Li¹, Eric Baetscher¹, Thomas M. Barbara¹, Manoj K. Sammi¹, Alexander A. Stevens¹, and Charles S. Springer^1
1Advanced Imaging Research Center, Oregon Health & Science University, Portland, OR, United States

Keywords: Molecular Imaging, Metabolism, Activity

Metabolic Activity Diffusion Imaging [MADI] maps on-going sodium pump metabolic flux.  Here, we investigate the question as to whether MADI can detect temporal changes of this activity in sequential acquisitions from the healthy human brain. 

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Louise Rosenqvist¹, Mikael Montelius¹, Maria Ljungberg^1,2, and Oscar Jalnefjord^1,2
1Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden, ²Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden

Keywords: Diffusion/other diffusion imaging techniques, Perfusion, IVIM

Using IVIM imaging for completely non-invasive perfusion MRI is gaining popularity. IVIM perfusion assessment depends not only on capillary network characteristics, but also on diffusion encoding-time. In this study, a flow-compensated pulse sequence with variable encoding-time was implemented and validated through phantom measurements, and subsequently used to study the encoding-time dependence of IVIM perfusion fraction in human brain tissue. Initial findings indicate a decrease in perfusion fraction as encoding-time increases.