Joint Annual Meeting ISMRM-ESMRMB • 16-21 June 2018 • Paris, France

Electronic Poster Session
Contrast Mechanisms
Wednesday, 20 June 2018
Electronic Poster

Quantitative Susceptibility Mapping
Electronic Poster
Contrast Mechanisms

Wednesday, 20 June 2018
 Exhibition Hall 16:15 - 17:15

Physiological Techniques
Electronic Poster
Contrast Mechanisms

Wednesday, 20 June 2018
 Exhibition Hall 16:15 - 17:15

Electrical Property Imaging
Electronic Poster
Contrast Mechanisms

Wednesday, 20 June 2018
 Exhibition Hall 17:15 - 18:15

 Computer # 5081. 1 Electro-Magnetic Property Mapping Using Kalman Filtering with a Single Acquistion at 3.0 T and 7.0 T MRI Han-Jae Chung, Jong-Min Kim, You-Jin Jeong, Jeong-Hee Kim, Chulhyun Lee, Chang-Hyun Oh The phase-based Electro-Magnetic (EM) MR property imaging such as Quantitative Susceptibility Mapping (QSM) and MR Electric Properties Tomography (MREPT) shows great potential clinically. The main post-processing steps in QSM and MREPT are high-pass filtering and Laplacian of MR images. They, however, cause severe artifacts and noise during conventional calculations. In this work, we propose a novel reconstruction method of EM property MRI using Kalman filter algorithm and show the utility of the proposed method by comparing the imaging results. 5082. 2 Development of Carbon Electrodes for Current Density Mapping during DBS Neeta Ashok Kumar, Munish Chauhan, Rosalind Sadleir We used MR phase mapping techniques in a preclinical DBS model to image current distributions nearby deep brain stimulation electrodes. To avoid safety issues and artifacts associated with imaging typical platinum-iridium (Pt-Ir) DBS leads, we developed custom carbon electrodes. We compared carbon electrode performance to size-matched Pt-Ir and clinical DBS electrodes at 7 T, using uniform phantoms and fixed brain tissue. Artifacts surrounding carbon electrodes were smaller than for Pt-Ir electrodes. Current density distributions derived from phase images were similar for both electrode types in uniform phantoms and fixed tissue. 5083. 3 In vivo Current Density and Conductivity Tensor Imaging of Human Brain During TACS using DT-MREIT Munish Chauhan, Aprinda Indahlastari, Aditya Kasinadhuni, Christopher Saar, Bakir Mousa, Kevin Castellano, Thomas Mareci, Rosalind Sadleir Knowledge of the electrical properties of brain tissue is key to developing better understanding of whole brain function. In this study, we present the first in vivo images of anisotropic conductivity distribution in the human head, measured at a frequency of ~10 Hz. We used MREIT techniques to encode phase changes caused by transcranial AC current flow (TACS) within the head via two independent electrode pairs. These results were then combined with DTI data to reconstruct full anisotropic conductivity distributions in 5 mm-thick slices of the brains of two participants. Conductivity values recovered in the study were broadly consistent with literature values. 5084. 4 Sequences for transceive phase mapping: a comparison study and application to conductivity imaging Soraya Gavazzi, Stefano Mandija, Cornelis van den Berg, Yulia Shcherbakova, Mick Bennis, Jan Lagendijk, Lukas Stalpers, Hans Crezee, Astrid van Lier Electrical properties imaging relies on accurate transceive phase determination. We explored the use of PLANET, an ellipse fitting approach on phase-cycled bSSFP data, for transceive phase mapping for the first time. We compared its accuracy, precision and time-efficiency with conventional SE and bSSFP techniques. Additionally, we reconstructed conductivity maps based on these techniques. We found that bSSFP and PLANET were as accurate as SE, but more precise. Also, bSSFP was the most time-efficient. Nevertheless, banding artefacts corrupting bSSFP transceive phase were, instead, intrinsically removed by PLANET.  PLANET had clinically acceptable scan-time and was generally more suitable for conductivity mapping. 5085. 5 Noninvasive Assessment of Electrical Conductivity Characteristics of Normal and Diseased Liver Using Electric Properties Tomography Khin Tha, Ulrich Katscher, Kinya Ishizaka, Kohsuke Kudo, Hiroki Shirato The feasibility of Electric Properties Tomography (EPT) in distinguishing between the normal and diseased liver tissues was evaluated. A 2D steady state free precession sequence was used to acquire the RF transceive phase needed for a simplified version of EPT; and a total of 10 dynamic sagittal scans of the liver were obtained under single breath-hold, in 10 healthy volunteers and 11 patients with hepatic lesions. Despite the need of technical improvements, noninvasive electrical conductivity assessment of the  liver by EPT was possible.  Its potential utility in identifying hepatocellular carcinomas with intratumoral necrosis and/ or high vascularity was also shown. 5086. 6 Diffusion Tensor Magnetic Resonance Electrical Impedance Tomography versus Magnetic Resonance Conductivity Tensor Imaging Mehdi Sadighi, Figen S. Oktem, B. Murat Eyuboglu In this study, recently proposed diffusion tensor magnetic resonance electrical impedance tomography (DT-MREIT) is compared with magnetic resonance conductivity tensor imaging (MRCTI) using simulated measurements generated by means of a finite element model. Both methods are used to reconstruct conductivity tensor images of an anisotropic conductivity distribution. In DT-MREIT, extra cellular conductivity and diffusivity ratio (ECDR) is recovered from its transverse gradient. In MRCTI, the conductivity tensor is reconstructed from two current profiles by using anisotropic Bz sensitivity (ABzS) method with a stronger regularization. Reconstructed conductivity images suggest that MRCTI provides better accuracy than DT-MREIT, at lower SNR levels. 5087. 7 Transceive Phase Corrected Contrast Source Inversion-Electrical Properties Tomography Peter Stijnman, Stefano Mandija, Patrick Fuchs, Rob Remis, Cornelis van den Berg Contrast Source Inversion Electrical Properties Tomography (CSI-EPT) is an integral-based method that aims to reconstruct tissue electrical properties through an iterative minimization procedure. This method requires complex $$B_1^+$$$data as input. In practice, however, the transmit phase cannot be measured in MRI-experiments. Only the transceive phase can be calculated from MR-measurements. In this work, the CSI-EPT reconstruction algorithm is reformulated to take the transceive phase into account. This transceive phase correction opens the possibility to exploit higher sensitivity of EPT at higher field strengths with regular quadrature setups. Additionally, for the first time CSI-EPT reconstructions from MR-measurements are shown. 5088. 8 Evaluating Validity of MREPT Assumptions for 21.1 T Ghoncheh Amouzandeh, Jens Rosenberg, Frederic Mentink-Vigier, Nastaren Abad, Samuel Grant This study examines conductivity mapping using MR Electrical Properties Tomography (MREPT) at ultra-high field (21.1 T). The accuracy of reconstructing conductivity using the complex B1+ field (Full-form) versus only the B1+ phase (Phase-based) is evaluated. Phantoms containing different NaCl concentrations were tested to compare these reconstructions with actual conductivities measured by dielectric probe at 900 MHz. Also, these methods were evaluated for experiments acquired with volume and surface coil configurations operated in either linear or quadrature transceiver. Conductivity maps of Full-form versus Phase-based MREPT from in vivo MCAO rats were acquired, with both providing similar variations across the ischemic brain. 5089. 9 bSSFP Phase Correction and its use in MREPT Safa Ozdemir, Yusuf Ider Balanced steady state free precision (bSSFP) has various advantages, namely high speed, high SNR, motion insensitivity and eddy current compensation. However, due to the B0 inhomogeneity, the so called "banding artifact" occurs at certain frequency regions. In this paper, phase correction method for the bSSFP sequence is proposed utilizing B0 and T2 maps. As an application, acquired B0 insensitive phase maps are used to obtain artifact-free conductivity maps. 5090. 10 Implementation of Conductivity Tensor Imaging (CTI) using MRI Nitish Katoch, Bup Kyung Choi, Saurav Sajib, Hyung Joong Kim, Oh In Kwon, Eung Je Woo Electrical conductivity is a passive material property primarily determined by concentrations of charge carriers and their mobility. The macroscopic conductivity of biological tissue at low frequency may exhibit anisotropy related with its structural directionality. When expressed as a tensor and properly quantified, the conductivity tensor can provide diagnostic information of numerous diseases. Imaging of conductivity distributions inside the human body requires probing it by externally injecting conduction currents or inducing eddy currents. Here we propose a novel method to reconstruct conductivity tensor images using an MRI scanner without any current injection. 5091. 11 A Fast and Dedicated First-Order Differencing EPT Reconstruction Method Patrick Fuchs, Stefano Mandija, Peter Stijnman, Wyger Brink, Cornelis van den Berg, Rob Remis A new method for reconstructing electrical properties from $$B_1^+$$$ data based on Maxwell's equations in an E polarized field (found in the midplane of a birdcage coil) is presented. This first-order EPT (foEPT) method uses first order spatial derivatives as opposed to the second order Helmholtz based MR-EPT methods and is thus less susceptible to noise. Furthermore, the method does not rely on any homogeneity assumptions. The method is validated using an in-vivo phantom measurement and compared to an MR-EPT reconstruction. FoEPT conductivity reconstructions show less noise-amplification and less boundary artefacts compared to Helmholtz-based MR-EPT reconstructions. 5092. 12 An Explicit Method for MR-Based Electrical Properties Reconstruction Free from Their Boundary Values Motofumi Fushimi, Takaaki Nara This paper presents a new explicit reconstruction method for Magnetic Resonance Electrical Properties Tomography (MREPT) in a circular region of interest (ROI) that does not require EP values on the boundary of the ROI. Starting from the complex form of Maxwell's equations, we solved the D-bar equation of the electric field with the Neumann boundary condition. The proposed method reconstructs EPs successfully without giving any knowledge of EP values on the boundary of the ROI. To extend the method to, for example, a rectangular ROI, is our future work. 5093. 13 LCF Artifact Elimination in cr-MREPT using Phased-Array Receive Coil Gulsah Yildiz, Yusuf Ider Convection-reaction equation based MREPT (cr-MREPT)1 conductivity images suffer from LCF artifact at low convective field (LCF) regions. Padding2 method has been proposed to overcome this issue but it requires additional acquisition, prolonging the total time. In this paper, we propose using data from different channels of phased-array receive coil to eliminate LCF artifact without requiring extra acquisitions. 5094. 14 Automated Seed Selection for Gradient-based Electrical Properties Tomography and Its in vivo Validation in the Brain Yicun Wang, Pierre-Francois Van de Moortele, Bin He Electrical Properties Tomography (EPT) retrieves tissue electrical conductivity and permittivity at Larmor frequency which potentially provides diagnostic information and facilitates subject-specific local SAR estimation. Gradient-based EPT (gEPT) significantly alleviates boundary artifact encountered by conventional EPT methods, yet its implementation requires subjective assignment of integration seed points. In this study, we developed an automated seed selection strategy based on locally calculated conductivity values, and evaluated the effect of seed number for human brain imaging. This new strategy was validated in eight healthy subjects to produce robust and accurate results, paving the path for an unbiased and fully-automated process for EP quantification. 5095. 15 Global Maxwell Tomography with Match Regularization for accurate electrical properties extraction from noisy B1+ measurements Jose Serralles, Athanasios Polimeridis, Luca Daniel, Daniel Sodickson, Riccardo Lattanzi We introduce a new regularization approach, “Match Regularization”, and show that in tandem with Global Maxwell Tomography (GMT) it enables accurate, artifact-free volumetric estimation of electrical properties from noisy B1+ measurements. We demonstrated the new method for two numerical phantoms with completely different electrical properties distributions, using clinically feasible SNR levels. Estimated electrical properties were accurate throughout the volume for both phantoms. Our results suggest that GMT with match regularization is robust to noise and can be employed to map electrical properties in phantoms and in vivo experiments. 5096. 16 In-vivo validation of water content Electrical Properties Tomography reconstructions in white matter using independent MR-EPT measurements Stefano Mandija, Petar Petrov, Jord Vink, Sebastian Neggers, Peter Luijten, Cornelis van den Berg MR-Electrical Properties Tomography (MR-EPT) can provide accurate mean conductivity values in large homogeneous tissues such as the white matter, provided sufficient erosion to avoid boundary regions. Water-content-EPT (wEPT) has been recently proposed to reconstruct EPs on a voxel-to-voxel basis. However, wEPT uses an empirical model calibrated with literature EPs values, assumed correct, obtained from ex-vivo probe measurements. In this work, the validity of the model employed in wEPT is verified for white matter conductivity reconstructions by using in the wEPT model calibration the mean white matter conductivity value obtained from in-vivo MR-EPT reconstructions as an independent modality. 5097. 17 Error Analysis of Helmholtz-based MR-Electrical Properties Tomography Stefano Mandija, Alessandro Sbrizzi, Ulrich Katscher, Peter Luijten, Cornelis van den Berg The numerical error arising from the computation of spatial derivatives using finite difference kernels is investigated for Helmholtz-based MR-Electrical-Properties-Tomography conductivity reconstructions. We show that this numerical error is one major cause of limited accuracy in Helmholtz-based MR-EPT reconstructions, even if mitigation strategies such as Gibbs ringing correction and Gaussian apodization in k-space are adopted. Ultimately, large derivative kernels lead to more noise-robust conductivity reconstructions, at the cost of more spatially-extended boundary errors. If boundaries are not explicitly taken into account during reconstructions, the accuracy of MR-EPT is severely hampered, particularly for spatially convoluted tissues such as the human brain. 5098. 18 Spatial resolution of Full cr-MREPT: 2D and 3D evaluation Yusuf Ider, Celik Boga, Gulsah Yildiz Determining the spatial resolution (SR) of Magnetic Resonance Electrical Property Tomography (MREPT) is important for assessing its utility in clinical applications. This study aims at finding the SR of Full cr-MREPT which yields images without internal boundary artifact.  It is shown by simulations and experimental results that SR in general is determined by the resolution of the MR data. With noise-free simulation data SR is 2-2.5 pixels. With noisy and real data it may go up to 4-4.5 pixels due to Low Pass filtering and regularization. SR appears to be equal in all three directions. 5099. 19 A Dictionary-Based Method for Conductivity Tensor Mapping Kathleen Ropella-Panagis, Scott Peltier, Douglas Noll Measuring conductivity tensors provides an additional layer of information as to how tissues in the body conduct electric current. Tissues with anisotropic conductivity values may include white matter tracts and muscle. Measurement of the tensor requires the object to rotate with respect to the main magnetic field of the MRI scanner, but the degree of rotation is severely limited in human subjects. We propose a dictionary-based approach that provides an estimate of the tensor given small rotation angles of the object. 5100. 20 In Vitro Imaging of Therapeutic Effect of Curcumin on Liver Cirrhosis using MR-based Electrical Conductivity Imaging Method Bup Kyung Choi, Nitish Katoch, In Ok Ko, Ji Ae Park, Jin Woong Kim, Hyung Joong Kim, Oh In Kwon, Eung Je Woo Curcumin has been used for the treatment of inflammatory diseases in oriental medicine, and its anti-inflammatory effect was recently reported. In this feasibility study, hepato-protective effect of curcumin was imaged in rat liver cirrhosis model, which was induced with dimethylnitrosamine (DMN). Magnetic resonance (MR)-based electrical conductivity imaging method was applied to evaluate tissue condition associated with protective effect. From electrical conductivity images, damaged liver tissues by DMN showed decreased conductivity than normal liver tissues. In contrast, cirrhotic tissues with curcumin treatment showed increased conductivity which was similar to normal tissue. 5101. 21 Contrast source inversion global Maxwell tomography: a technique for electric properties MR imaging without phase information. Alessandro Arduino, Oriano Bottauscio, Luca Zilberti The possibility to perform MR imaging of the electric properties relying only on the measurable magnitude of transmit sensitivity, without any hypothesis on its phase, is an extremely interesting task pursued by the scientific community in the last years. Here, the adoption of the contrast source inversion technique in the context of the global Maxwell tomography is proposed. The lack of phase information affect the numerical minimisation procedure by introducing local minima in the cost functional. The convergence of the method is restored by the adoption of multi-channel transmit coils, which can increase the data by measuring multiple transmit sensitivities. 5102. 22 Dictionary-based Electric Properties Tomography for brain conductivity imaging Ulrich Katscher, Max Herrmann, Thomas Amthor, Christian Findeklee, Mariya Doneva Electric Properties Tomography (EPT) derives tissue conductivity and permittivity according to the Helmholtz equation via the second derivative of the measured complex B1 map, or by iteratively solving the corresponding forward problem. This abstract presents a different type of EPT reconstruction: the measured B1 map is compared locally with entries of a dictionary, which are small B1 maps of a priori known electric properties. This "dictionary-based EPT" (db-EPT) could be able to solve the transceive phase problem as well as the boundary problem of EPT. This study demonstrates the feasibility of db-EPT by measuring brain conductivity of healthy volunteers. 5103. 23 Evaluation of the Noise Behavior of Gradient-based vs. Helmholz-based Reconstruction of Electrical Properties Tomography in Simulation Yihe Hua, Ileana Hancu, Seung-Kyun Lee, Teck Beng Desmond Yeo, Jiaen Liu Electrical properties tomography (EPT) is a promising technique that has the potential to generate high resolution images of tissue electrical properties in vivo. One limitation of EPT is its high sensitivity to noise in the measured data. In this study, a comparison was performed between the so-called gradient-based EPT (gEPT) algorithm and the Helmholtz-based EPT method in a simulation. The result suggests significantly improved performance using gEPT and provides useful insight into the noise behavior of various EPT algorithms for optimization of the algorithm design. 5104. 24 Mapping the Brain’s water content and low-frequency electrical properties through T1-weighted MRI imaging Cornelia Wenger, Catherine Tempel-Brami, Hadas Hershkovich, Moshe Giladi, Zeev Bomzon This study investigates the possibility to extend the water-content based electrical properties tomography (wEPT) technique to lower frequencies. The wEPT approach assumes that electrical properties (EP) of brain tissues can be estimated from water-content (WC) which is derived from two T1-weighted MRIs. Adapted wEPT model parameters were evaluated from ex-vivo measurements of calf brain tissue samples. We performed wEPT estimations in an in-vivo rat brain tumor model, followed by ex-vivo measurements of brain extracted samples. Results predict good correlation between WC ex-vivo measurements and in-vivo wEPT estimations. Yet, mapping EPs with wEPT at lower frequencies needs further investigation.
Advancements in CEST Methodology & Applications
Electronic Poster
Contrast Mechanisms

Wednesday, 20 June 2018
 Exhibition Hall 17:15 - 18:15

 Computer # 5105. 25 Spin-lock Imaging of 3-o-Methyl-D Glucose (3oMG) in Brain Tumors Zhongliang Zu, Xiaoyu Jiang, Junzhong Xu, John Gore We evaluated the ability of spin-lock imaging to detect the uptake of 3-o-methyl-D-glucose (3oMG) in normal brain and brain tumors in animals. We used $$\triangle R_{1\rho}^{diff}$$$to isolate the contribution from only the injected agent. We found that $$\triangle R_{1\rho}^{diff}$$$ in tumors increased rapidly after injection, whereas intact brain showed a gradual increase up to 1h. $$\triangle R_{1\rho}^{diff}$$was significantly different between tumors and contralateral normal tissues 5106. 26 Chemical Exchange Rotation Transfer imaging of Phosphocreatine in Muscle Zhongliang Zu, Eugene Lin, Elizabeth Louie, Xiaoyu Jiang, Christopher Lankford, Bruce Damon, Mark Does, John Gore, Daniel Gochberg CEST imaging of Creatine has been reported, whereas selective mapping of PCr in vivo has not been implemented. We found that CEST imaging of Creatine may be influenced by other molecules in muscle, but CERT imaging of PCr is more specific and thus should be a better indicator of changes of flux through the CK reaction. 5107. 27 Chemical Exchange Saturation Transfer imaging of prostate cancer at 3T: Repeatability, and initial results of an acquisition and multi-pool analysis protocol Vincent Evans, Francisco Torrealdea, Marilena Rega, Mina Kim, Mrishta Brizmohun Appayya, Arash Latifoltojar, Shonit Punwani, Xavier Golay, David Atkinson An optimised acquisition and post-processing protocol for multi-pool Lorentzian analysis of CEST data in the prostate at 3T is described. The repeatability of the technique is evaluated in five healthy volunteers and the contrast observed between healthy tissue, TZ tumour and PZ tumour in two prostate cancer patients is evaluated. 5108. 28 Toward CEST MRI of renal masses: protocol optimization and first preliminary data Shu Zhang, Bian Li, Joshua Greer, Ananth Madhuranthakam, Jochen Keupp, Ivan Dimitrov, Robert Lenkinski, Ivan Pedrosa, Elena Vinogradov Chemical Exchange Saturation Transfer (CEST) MRI is emerging as a tool for the studies of human malignancy. However, the translation of CEST into a successful tool for renal cancer characterization has been slow and hampered by technical difficulties associated with body imaging, such as motion, contaminating lipid signals and increased B­0 ingomogeneity. Here we optimize CEST protocol for characterization of renal masses and demonstrate CEST measurements are feasible in kidneys using combination of motion synchronization, post-processing registration and lipid artifact removal. In addition, first Renal Cell Carcinoma patient CEST-mDixon data is shown and imaging results are correlated with the pathology. 5109. 29 APT-CEST post Gadolinium. Should it be avoided? Comparison of pre- & post-Gadolinium CEST on glioma at 3T. Francisco Torrealdea, Joe Hearle, Vincent Evans, Moritz Zaiss, Ana Carvalho, Anath Shankar, Harpreet Hyare, David Atkinson, Xavier Golay, Anna Barnes, Marilena Rega This study compares APT-CEST between pre- and post-gadolinium in patients with gliomas at 3T, and evaluates the feasibility of performing CEST after administration of T1 contrast. The results of the study demonstrate that Gd administration does not significantly affect the quality of the APT-CEST image, encouraging the acquisition of CEST data, even after the administration of T1 contrast agents. 5110. 30 Phase-locked CEST – Introducing dynamic B0-correction to gagCEST Johannes Windschuh, Moritz Zaiss, Jae-Seung Lee, Alexej Jerschow, Ravinder Regatte Even a small frequency drift of less than 1Hz/min of the MRI scanner can have a strong impact on gagCEST measurements. We propose a dynamic B0-correction that tracks the frequency shift using the phase images provided by the GRE readout. We show that this correction eliminates the influence of the frequency drift on gagCEST without the need of additional measurement time allowing higher accuracy, reproducibility, and comparability of gagCEST studies. 5111. 31 Accelerating CEST with Patch-based Global Orthogonal Dictionary Learning Huajun She, Xinzeng Wang, Shu Zhang, Ece Ercan, Jochen Keupp, Anath Madhuranthakam, Ivan Dimitrov, Robert Lenkinski, Elena Vinogradov This work investigates accelerating CEST imaging using patch-based global spatial-temporal dictionary learning (G-KSVD). We extend the dictionary learning for CEST acceleration. CEST data has high spatial-temporal correlation, so we can utilize the global Z-Spectrum information as well as the spatial information to form the global spatial-temporal dictionary. The dictionary is learned iteratively from overlapping patches of the dynamic image sequence along both the spatial and temporal directions. The proposed method performs better than the BCS and k-t FOCUSS methods for both phantom and in vivo brain data at high reduction factor of R=8. 5112. 32 Accelerated CEST Imaging with Parallel Deep Convolutional Neural Networks Huajun She, Shu Zhang, Xinzeng Wang, Ece Ercan, Jochen Keupp, Anath Madhuranthakam, Ivan Dimitrov, Robert Lenkinski, Elena Vinogradov CEST is a new contrast mechanism in MRI. However, a successful application of CEST is hampered by its slow acquisition. This work investigates accelerating CEST imaging using parallel convolutional neural networks (PCNN). We extend the Cascade-CNN into a multi-channel model and train the network establish a mapping from the multi-coil input to multi-coil output. This work is the first try to apply deep learning and convolutional neural networks technique in accelerating CEST imaging. The in vivo brain results show that the proposed method demonstrates a high quality reconstruction of the MTRasym maps with different saturation pulses at R=4. 5113. 33 Accelerating 3D CEST Imaging with Low Rank Sparse Reconstruction Huajun She, Ece Ercan, Shu Zhang, Xinzeng Wang, Jochen Keupp, Anath Madhuranthakam, Ivan Dimitrov, Robert Lenkinski, Elena Vinogradov Chemical exchange saturation transfer (CEST) is a new contrast mechanism in MRI. However, a successful application of CEST is hampered by its slow acquisition especially in the 3D applications. Compressed sensing (CS) is powerful for reconstruction of highly undersampled data. This work implements the 3D pulsed steady-state CEST acquisition sequence and extended the low rank plus sparse (L+S) method to a 3D version. The phantom and in vivo human brain results demonstrate our design has the potential to accelerate the 3D CEST imaging about 4 times. 5114. 34 Quantitative Magnetization Transfer Imaging in Murine Kidneys with Renal Artery Stenosis Kai Jiang, Lilach Lerman Quantitative magnetization transfer (qMT) imaging was used to measure bound water fraction in mouse kidneys with renal artery stenosis (RAS). MT-weighted images at variable offset frequencies and amplitudes, as well as B0, B1, and T1 maps of control and RAS kidneys, were acquired. A two-pool qMT model was used to estimate the bound water fraction as well as other relaxation and exchange parameters. An increased bound water fraction was found in the cortex, outer medulla, and inner medulla of the RAS kidneys. In conclusion, qMT imaging offers potential new biomarkers for assessment of RAS kidneys. 5115. 35 Assessing changes in kidney pH in acute kidney injury model using acidoCEST MRI Atul Minhas, Jack Sharkey, Edward Randtke, Patricia Murray, Bettina Wilm, Mark Pagel, Harish Poptani Kidneys are responsible for regulation of pH homeostasis, and cytotoxicity caused by cancer therapeutics can significantly alter renal function and homeostasis. Chemical exchange saturation transfer (acidoCEST) MRI has been proposed to measure tissue pH in-vivo using exogenous contrast agents. In this study, we used the acidoCEST technique to measure changes in kidney pH after acute kidney injury (AKI) in rodents. Typically, CT contrast agents such as Iopamidol (300 mg iodine/mL) are used as CEST contrast agent in acidoCEST MRI. However, the accuracy of acidoCEST using CT contrast agents relies on the delivery of the contrast agent to the target organ. To address this issue, we performed acidoCEST and FAIR-EPI based perfusion imaging to assess pH and blood flow changes in a mouse model of AKI. Results show that perfusion of kidneys affect pH measurements. 5116. 36 Detection of the accumulation of mannitol in rat brains using CEST MRI Jing Liu, Chengyan Chu, Lin Chen, Jia Zhang, Rohit Srivatava, Piotr Walczak, Jiadi Xu, Peter van Zijl, Miroslaw Janowski, Guanshu Liu Mannitol is a clinically widely-used osmotic agent. Accumulation of mannitol in the interstitium of the brain, however, can cause severe adverse effects. Here we used CEST MRI to detect mannitol directly through its inherently carried exchangeable hydroxyl protons. After comprehensively characterizing the CEST properties of mannitol in vitro, we demonstrated that the intra-arterial infusion of mannitol at an excess dose led to a significantly elevated CEST signal at 0.9 ppm, indicating that CEST MRI has great clinical potential to be used as a monitoring tool for mannitol treatment. 5117. 37 Nuclear Overhauser enhancement effect of low $$B_{1}$$ power CEST RF in human brain at 3.0 T Yuki Kanazawa, Masafumi Harada, Mitsuharu Miyoshi, Ikuho Kosaka, Kotaro Baba, Hiroaki Hayashi, Yuki Matsumoto The purpose of this study is to clarify the relationship between APT and NOE effects derived from CPE fitting of the human brain on a 3 T MR scanner. CEST imaging with different B1 values of the brain was performed in healthy subjects. The mean NOE values of white matter at 0.5 µT were higher than all regions (P < 0.05). CPE-spectrum shows greater sensitivity for both APT and NOE peaks than conventional Z-spectrum and MTRasym. It is found that NOE imaging on a 3.0 T scanner is sensitive on low-B1 power regardless of the CEST fitting process. 5118. 38 GluCEST MRI: Reproducibility, background contribution and source of glutamate changes in the MPTP mouse model of Parkinson’s disease Puneet Bagga, Stephen Pickup, Dan Martinez, Rachelle Crescenzi, Ari Borthakur, Gaurav Verma, Joel Greenberg, John Detre, Hari Hariharan, Ravinder Reddy Glutamate Chemical Exchange Saturation Transfer (GluCEST) MRI provides indirect detection of glutamate in vivo by measuring the exchange of glutamate amine protons with bulk water. The GluCEST contrast is potentially contaminated by a contribution of other metabolites exhibiting proton chemical exchange. We evaluated the reproducibility and background contamination to the GluCEST and source of the GluCEST changes in MPTP mouse model. Approximately 28% of GluCEST contrast appears to be derived from sources other than glutamate that are also not detectable by MRS. Glial proliferation caused by neuroinflammation was found to be the cause of elevated glutamate in mice exposed to MPTP. 5119. 39 Toward Safer Monitoring of Glucose Transport in a Rat Brain Tumor Necrosis using 3-O-Methyl-Glucose Chemical Exchange-sensitive Spin-Lock Magnetic Resonance Imaging Julius Chung, Moon-Sun Jang, Geun Ho Im, Wonmin Choi, Tao Jin, Seong-Gi Kim, Jung Hee Lee Glucose exchange-sensitive spin lock imaging has been shown to have promise in monitoring glucose uptake with reasonable sensitivity.  There are design choices that can be made in such an experiment such as whether to use an analog for better sensitivity and how to establish an efficient spin-lock.  We examine metabolic uptake of a rat brain tumor with necrosis using 3-O-methyl-glucose, a safer glucose analog than 2DG, and examine differences between using an adiabatic pulse and a paired self-compensated pulse with lower peak power.  Both pulses demonstrated delayed uptake in the infarcted tumor region although with higher sensitivity using adiabatic pulses. 5120. 40 Magnetization Transfer in Lipids - Role of Exchangeable Groups and Water BindingVideo Permission Withheld Weiqi Yang, Jae-Seung Lee, Johannes Windschuh, Maureen Leninger, Nate Traaseth, Alexej Jerschow We study the magnetization exchange mechanism in lipid systems, with relevance to imaging myelin via MT contrast. Studies of samples with different lipid compositions reveal exchange time scales, and the role of structural features in the contrast mechanism. Insights from molecular dynamics provide estimates of the contribution of the dipolar pool equilibration to the MT amplitude. The effect of lipid head groups, and the contribution of cholesterol and proteins are examined. It is hoped that these findings will help explaining the origin of White Matter MT contrast and will allow better myelin quantification by tailored saturation sequences. 5121. 41 In vivo Kinetic CEST MRI of sodium salicylate(NaSA): Comparison of MTRasym and Subtraction of saturation-weighted images Yanrong Chen, Chengwang Jin, Yan Luo, Chongxue Bie, Yingcheng Zhao, Xiaowei He, Xiaolei Song Salicylate analogues feature chemical shift far from water (Δω = 8-10 ppm), however, there are almost no available reports on their in vivo detection of salicylate upon intravenous administration. We aim to optimize the in vivo detection of NaSA, by comparing compared MTRasym and a Dynamic Salicylate Enhancement (DSE). For the mice brain with LPS-induced inflammation, there are ~4% DSE signal which displays a clear kinetic trend. While MTRasm values are very small, oscillating between -2% to 0% due to the unsymetric MTC. In conclusion, our DSE method is able to track the dynamic signal changes following the infusion of NaSA. 5122. 42 Assessment of a clinically feasible Bayesian fitting algorithm using a simplified description of Chemical Exchange Saturation Transfer (CEST) Imaging Aaron Kujawa, Mina Kim, Eleni Demetriou, Annasofia Anemone, Dario Longo, Moritz Zaiss, Xavier Golay A Bayesian fitting algorithm was combined with analytical approximations of the Bloch-McConnell (BM) equations with the aim to considerably reduce processing time. The accuracy of the algorithm was assessed with simulated data and data from phantom experiments and compared to fit results obtained with the numerical solution of the BM equations. Continuous-wave and pulsed saturation was considered. The results showed agreement between estimates and ground truth as well as between the approximate analytical and numerical model implementations of the Bayesian algorithm. A considerable reduction of processing time was achieved. 5123. 43 Including water nutation in an analytic solution for pulsed CEST Christopher Lankford, Zhongliang Zu, Elizabeth Louie, Mark Does, Daniel Gochberg Pulsed chemical exchange saturation transfer (CEST) MRI lacks an analytical solution, impeding data analysis and optimization efforts. A recently proposed solution has mitigated this problem, but it ignores water pool nutation and is thus inaccurate near the water resonance frequency. This work proposes a solution that accounts for water nutation assuming a known flip angle function which can be numerically estimated with no a priori knowledge about tissue parameters. The nutation-corrected solution closely matches numerical Bloch-McConnell simulation, even near the water resonance frequency. 5124. 44 Chemical exchange saturation transfer magnetic resonance imaging of functionalized poly(N, N’-methylene bisacrylamide 4-aminobutanol) gel Weiqiang Dou, Jos M.J. Paulusse, Heinz Peter Janke, Xiaolei Song, Jiadi Xu, J.W.M Bulte, Arend Heerschap Poly (amido amine)s like poly(N, N’-methylene bisacrylamide 4-aminobutanol) (MBA-ABOL) are compounds with promising biomedical applications, which, however, require that they can be visualized without contrast application. In this study we investigated if they can be imaged in a “label free fashion” by CEST MRI making use of their exchangeable amide and hydroxyl protons. We systematically determined optimal conditions for CEST in MBA-ABOL in solution and then demonstrated that the material can be imaged both in vitro and ex vivo, implanted in a rat leg, with a strong CEST effect from the amide protons and substantial effect from the hydroxyl protons. 5125. 45 Clinically Feasible Model-based Analysis of Amide Proton Transfer MRI in Acute Ischaemic Stroke Paula Croal, Yunus Msayib, Kevin Ray, James Larkin, Brad Sutherland, George Harston, Alistair Buchan, Peter Jezzard, James Kennedy, Nicola Sibson, Michael Chappell Model-based analysis of CEST MRI is a robust quantitative method, however, the lengthy acquisition and processing times make it less clinically feasible. It has recently been proposed that partial acquisition of Z-spectra provides a faster approach, but at the cost of increased variability and large alterations in baseline Amide Proton Transfer (APT) effect. Here we present a refined approach, accounting for magnetisation transfer effects, which reduces acquisition and processing times and also decreases variability in the data. We demonstrate its ability to detect pathological reductions in the APT effect in both preclinical and clinical cohorts of acute ischaemic stroke respectively. 5126. 46 Improved quantification of amide proton transfer effect with direct water saturation- and magnetization transfer-correction in a glioma rat model at 3 Tesla Yin Wu, Yinsheng Chen, Yiying Zhao, Shasha Yang, Jing Zhao, Zhongping Chen, Phillip Sun Quantification of in vivo APT effect with routine asymmetry analysis is problematic due to concomitant contributions. Herein, a steady-state CEST signal solution was utilized to estimate direct water saturation (DWS) to improve Z-spectral quantification in a pulsed-RF CEST imaging. Specifically, APT effect was measured from the DWS and magnetization transfer (MT)-corrected CEST signals in glioma rat brains post-chemoradiotherapy at 3 Tesla. The proposed method revealed significant APT signal difference among regions of control (3.13±0.38%), necrosis (3.95±0.31%) and tumor (4.56±0.34%), consistent with histological observations and superior than routine asymmetry analysis. 5127. 47 In-vivo Z-spectra acquisition with decreased direct saturation using adiabatic spin-lock pulses at 9.4T Kai Herz, Chirayu Gandhi, Klaus Scheffler, Moritz Zaiss Off-resonant spin-lock imaging enables a lot of possibilities for T1ρ and chemical exchange (CE) sensitive applications. For this purpose, a matching amplitude of the tipping and the locking pulse is required, which can be difficult due to the high power requirements of adiabatic pulses. In this work, we present a newly shaped adiabatic half-passage pulse, usable at low power to match the amplitude of the pulses. Off- and on-resonant saturated images acquired at 9.4T are shown. The new pulse shape is able to generate robust images with comparatively low power at ultra-high-field strengths. 5128. 48 Optimization of overlap-resolved CEST for specific mapping of Glutamate and GABA Frederico Severo, Noam Shemesh Glutamate-CEST (GluCEST) has been recently emerging as a powerful new technique for mapping Glutamate in the brain. A recent development termed overlap-resolved CEST (orCEST) has demonstrated that other metabolites may contaminate GluCEST contrast, and proposed how to resolve the wanted signals; here we optimize orCEST contrast to reflect Glutamate and GABA with very high sensitivity and good specificity. orCEST experiments are optimized on metabolite phantoms, and then are applied in-vivo in the rat. The results are promising for neurotransmitter mapping in-vivo.
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