ISMRM 25th Annual Meeting & Exhibition • 22-27 April 2017 • Honolulu, HI, USA

Electronic Poster Session: Contrast Mechanisms
 3615 -3638 Arterial Spin Labeling: Methodology 3639 -3662 Electric Property Imaging & Clinical QSM 3663 -3686 QSM Technical Developments 3711 -3734 Relaxation: Methods & Others 3735 -3758 CEST/MT/NOE: Animal Models & Human Translation 3759 -3782 CEST: Acquisition, Quantification & Characterization 3783 -3806 Contrast Mechanisms: Miscellaneous

Arterial Spin Labeling: Methodology
Electronic Poster
Contrast Mechanisms

Monday, 24 April 2017
 Exhibition Hall 16:15 - 17:15

 Computer # 3619. 53 Bayesian model selection of Time Encoded Arterial Spin Labelling: effect of T1 and dispersion Marco Castellaro, Erica Silvestri, Ilaria Boscolo Galazzo, Matteo Tonietto, Alessandro Palombit, Francesca Pizzini, Stefania Montemezzi, Enrico Grisan, Matthias Van Osch, Alessandra Bertoldo Time-Encoded Arterial Spin Labelling (TE-ASL) has been proposed as a tool to efficiently sample the kinetics of the ASL signal. We propose a model comparison based on Bayesian Model Selection (BMS), to provide insights on which is the optimal model for the quantification of TE-ASL. Our results show how important it is to consider both T1 decay and dispersion in the quantification process. When mainly interested in GM, it is advisable to incorporate the dispersion of the bolus in the model with a Gamma kernel dispersion model and to use a single T1 value of 1.3s. 3630. 64 2D CAIPIRINHA improves accelerated 3D GRASE ASL Dimo Ivanov, Josef Pfeuffer, Anna Gardumi, Kâmil Uludag, Benedikt Poser Arterial spin labelling (ASL) is the primary non-invasive MRI approach to measure cerebral blood flow in healthy subjects and patients. Recently, a consensus paper has recommended segmented versions of 3D spin-echo readouts like GRASE, but these are susceptible to motion and have poor temporal resolution. To alleviate these drawbacks, we propose to accelerate the 3D GRASE readout and utilize 2D CAIPIRINHA for the reconstruction. We demonstrate that our approach is superior or at least equivalent to the 2D GRAPPA technique, depending on the acceleration factor used. The proposed approach will particularly benefit functional and clinical ASL applications. 3626. 60 A multi-compartment cerebral perfusion phantom to test territory selection using vessel encoded arterial spin labelling Michael Chappell, Bridget Fryer, Anton Firth, Robert Wight, Thomas Kirk, Thomas Okell Vessel encoded arterial spin labelling allows the visualisation of perfusion territories in the brain. However, the accuracy of perfusion measurements from VE-ASL and the associated analysis methods is difficult to establish without ground truth. Perfusion phantom devices have been prosed for conventional ASL, but don't currently attempt to model the full cerebral vasculature anatomy of the brain, limiting their value in evaluation of VE-ASL methods. Thus in this work we set out to create a multi-compartment, multi 'artery' perfusion phantom based on normal vascular anatomy. 3632. 66 Optimization of Flip Angle Design for Reduced T2 Blurring of 3D Arterial Spin Labeling Li Zhao, David Alsop Conventional 3D arterial spin labeling images suffer from pronounced T2 blurring. In this work, new variable flip angle schemes, which can provide a Hann or Fermi window response across the slice direction, or which can be easily corrected to the designed window response and provide optimal SNR, were evaluated. Volunteers’ results show reduced blurring, improved SNR and contrast with the proposed methods. 3618. 52 In-vivo evaluation of pCASL labeling scheme and position Marta Vidorreta, Li Zhao, Sheila Shankar, Daniel Wolf, David Alsop, John Detre Despite recent consensus in the ASL community on pseudo-continuous ASL as preferred labeling method, several challenges still exist towards optimizing pCASL labeling efficiency in-vivo, including its sensitivity to vessel tortuosity and off-resonance effects. In this work, we assess the impact of labeling plane location and labeling scheme on the ASL perfusion signal. 3631. 65 A Deconvolution Method for Improved CBF Quantification in 3D-GRASE ASL Kenneth Wengler, Xiang He Pseudo-continuous arterial spin labeling (pCASL) with segmented 3D-GRASE acquisition is widely accepted as the optimal ASL technique. However, the method suffers from blurring along the partition direction caused by point spread function (PSF) broadening. In this study, a PSF deconvolution method for pCASL images with 3D-GRASE acquisition is developed and evaluated in simulations and in-vivo experiments. The deconvolution method greatly reduces the effects of the PSF and recover the perfusion signal for segmentation factors of at least 2PAR x 2PE. The proposed deconvolution method improves the accuracy of cerebral blood flow quantification and facilitates the use of lower segmentation factors. 3623. 57 The influence of acquisition parameters on CBF and BOLD sensitivity in 3 and 7 Tesla ASL fMRI Anna Gardumi, Dimo Ivanov, Roy Haast, Josef Pfeuffer, Benedikt Poser, Kamil Uludag Arterial spin labeling (ASL) measures cerebral blood flow (CBF) non-invasively. Compared to the BOLD signal, CBF is quantitative and more directly linked to neural activation, albeit with lower SNR. Due to increased SNR and T1 relaxation time, ultra-high field MRI promises benefits for ASL. However, technical challenges remain to exploit its full potential. Here, we compared 3T and 7T ASL implementations and studied the influence of labeling schemes, resolution, parallel imaging, and field strength on the CBF and BOLD functional contrast. We found 3T pCASL being advantageous for low-resolution and 7T FAIR for high-resolution and acquisitions utilizing parallel imaging. 3617. 51 Improved spatial encoding for vessel-selective pCASL: improving efficiency, minimising mis-labeling, and shortening scan-time for artery specific MRA Yuriko Suzuki, Matthias van Osch, Thomas Okell Hadamard-encoded vessel-encoded pCASL is a vessel-selective ASL technique that enables SNR-efficient vascular territory mapping for perfusion MRI. For vessel-selective ASL-MRA, however, minimising the number of encodings is necessary to achieve clinically feasible scan times. The spatial modulation of inversion in ve-pCASL is gradual, which could potentially reduce SNR-efficiency and cause mislabeling of arteries when reducing the number of encodings. In this study, the modulation of ve-pCASL was optimized to achieve sharper inversion to avoid signal contamination of non-targeted arteries and achieve 4D-MRA with a minimal number of Hadamard-encodings. 3620. 54 Defining the optimal post-labeling delay for pCASL using patient specific estimates of blood velocity in the carotid artery Neville Gai, John Butman Pseudo-continuous arterial spin labeling (pCASL) with 3D non-segmented acquisition scheme allows assessment of full brain CBF with sufficiently high SNR and resolution in an efficient manner. Post-labeling delay is a critical parameter which needs to be determined preferably on a per subject basis since PLD can change based on the physiological condition of a subject. Multiple post-labeling delay (PLD) pCASL could address this issue. However, multiple PLD pCASL is not feasible for the 3D non-segmented acquisition scheme. In this work, we related the velocity in carotid artery (CA) measured using two schemes to PLD in ten volunteers. A relationship between the CA velocity and optimal PLD was derived which allows for optimal PLD to be determined on the fly for each subject. 3624. 58 Improved labeling efficiency in Super-Selective Pseudo-Continuous Arterial Spin Labeling Jonas Schollenberger, C. Alberto Figueroa, Luis Hernandez-Garcia We investigate how to improve the SNR of vessel-selective ASL images by off-resonance compensation and label rotation scheme optimization. 3625. 59 Automatic Planning for fast and robust Flow Territory Mapping Michael Helle, Kim van de Ven, Fabian Wenzel Super-Selective Pseudo-continuous Arterial Spin Labeling (pCASL) requires the labeling focus to be optimized to each artery of interest individually. This might be time-consuming especially for inexperienced users, and suboptimal results are possible as the labeling efficiency depends on the location of the labeling spot, as well as its angulation, which should be perpendicular to the artery. This study demonstrates an automatic planning approach for Super-Selective pCASL measurements in the major brain feeding vessels and subsequently compares the results to images acquired using a manual positioning of the labeling spot. 3628. 62 Robust 3D pCASL perfusion imaging using a Cartesian Acquisition with Spiral Reordering (CASPR) Joshua Greer, Xinzeng Wang, Marco Pinho, Ivan Pedrosa, Ananth Madhuranthakam Arterial spin labeling can non-invasively measure perfusion, but offers low SNR compared to contrast-enhanced perfusion techniques. A novel 3D TSE with a Cartesian Acquisition with SPiral Reordering (CASPR) was implemented and combined with pCASL in the brain and kidneys. This sampling technique samples the center of k-space early in each echo train, and was shown to provide significantly improved 3D perfusion images compared to 3D linear acquisitions, and more extensive coverage than 2D acquisitions in a similar scan time. 3629. 63 Single shot high resolution 3D arterial spin labeling using 2D CAIPI and ESPIRiT reconstruction Xingfeng Shao, Danny JJ Wang We present a single-shot 3D GRASE pCASL technique, which reduces the data loss due to motion, using 2D CAIPI sampling strategy, and reconstruct the under-sampled data using ESPIRiT. Proposed sequence employs 4-fold acceleration and achieves whole brain volume with isotropic 3×3×3 mm3 resolution. This technique was successfully applied for high resolution multi-delay ASL imaging, and CBF, ATT and T1 map could be simultaneously calculated in 4 min 14 sec. 3636. 70 Functional connectivity mapping using 3D GRASE arterial spin labeling MRI Kalen Petersen, Daniel Claassen, Manus Donahue The overall goal of this work is to optimize arterial spin labeling (ASL) MRI techniques to enable the use of baseline cerebral blood flow (CBF) fluctuations to identify major intrinsically-connected resting state networks (RSNs). We provide data in support of 3D GRASE pCASL being able to provide similar functional resting state networks as BOLD. Additionally, extremely low-frequency fluctuations, less than 0.01 Hz, were present in the CBF-weighted pCASL data, suggesting that application of pCASL may provide additional functional information relative to BOLD, which generally requires low-frequency filtering. 3637. 71 Assessment of Resting State Perfusion and Coherent Large-Scale Brain Networks in Healthy Aging Using Arterial Spin Labeling Perfusion MRI Alvaro Galiano, Reyes García de Eulate, Marta Vidorreta, Miriam Recio, María Fernández-Seara Cognitive decline is associated with aging even in the absence of disease. In this study ASL perfusion fMRI was used to investigate changes in perfusion and resting state networks connectivity due to aging, by comparing two groups of healthy subjects (young and elderly). Results showed perfusion deficits in the elderly group, in association areas, related with advanced cognitive abilities. Disruptions in varios core RSNs were also detected. Assessment of perfusion and resting functional connectivity jointly could be a good predictor of cognitive decline and a good biomarker for treatments aiming to extend cognitive abilities. 3635. 69 The effect of post-labeling delay on multiband pCASL based functional connectivity Alexander Cohen, Andrew Nencka, Yang Wang When too short a post-labeling delay (PLD) is used for ASL, intravascular artifacts can be present. This issue is amplified in multiband (MB) ASL where superior slices are acquired early in the acquisition. Here, MB pseudocontinuous ASL (pCASL) and a dual regression approach were used to analyze functional connectivity with PLD=1000ms and 1525ms. Increased whole-brain tSNR was observed for the PLD=1000ms data, but intravascular signal was present. Group connectivity was similar between PLDs, and no significant differences in mean or max z-score were seen between PLD. Thus, shorter PLDs may be appropriate for MB-ASL rsfMRI despite the presence of intravascular artifacts. 3621. 55 The reproducibility of absolute ASL-CBF: assessing the stability of absolute CBF, M0 and calibration images Mareike Buck, Matthias Günther, Federico von Samson-Himmelstjerna In this abstract the reproducibility of absolute CBF as well as the M0- and an optional calibration-image is assessed during individual scanning-sessions and also over the entire day. Comparably high reproducibility was found for all three types of images, which agrees with similar earlier findings. However, also the uncertainty of the corresponding fits was found to be high. 3634. 68 A Spatio-temporal Denoising Approach based on Total Variation Regularization for Arterial Spin Labeling Cagdas Ulas, Stephan Kaczmarz, Christine Preibisch, Jonathan Sperl, Marion Menzel, Axel Haase, Bjoern Menze We present a new spatio-temporal denoising method for arterial spin labelling MR image repetitions, and mainly aim to improve the quality of perfusion-weighted images and cerebral blood flow (CBF) maps obtained from a subset of all dynamics available. Our technique is based on a two-step 3D total variation regularization, which is applied to subsets of control/label pairs in the first step and to resulting perfusion-weighted (difference) images in the second step. We demonstrate that our method leads to improved quality of perfusion-weighted images and CBF maps compared to existing spatial filtering techniques in short computation time. 3633. 67 A denoising method for arterial spin labeling data based on total generalized variation (TGV) with a spatial varying regularization parameter Stefan Spann, Kamil Kazimierski-Hentschel, Christoph Aigner, Rudolf Stollberger Arterial spin labeling perfusion imaging permits a noninvasive approach to measure cerebral blood flow. The poor SNR of this technique makes denoising essential. ASL images are often corrupted with motion, physiological or scanning artifacts or acquired using parallel imaging leading to spatial dependent noise. To account for those artifacts and spatial varying noise we propose a denoising approach based on total generalized variation (TGV) using a spatial dependent regularization parameter. The performance of the proposed technique is evaluated on synthetic and in-vivo data and compared with the non-local means combined dual-tree complex wavelet transform (DT-CWT) denoising method. 3638. 72 Trait Specificity of Regional Cerebral Blood Flow between Different Resting-State Conditions Zhengjun Li, Marta Vidorreta, Daniel Wolf, John Detre We used latent state-trait theory to examine trait specificity of regional cerebral blood flow (CBF) acquired using arterial spin labeled (ASL) perfusion MRI in four different resting-state conditions (eyes-open, eyes-closed, fixation, and a low-level attention task (psychomotor vigilance task, PVT)). Most brain regions accepted the latent state-trait model. Fixation exhibited the lowest latent trait specificity, while PVT, eyes-open, and eyes-closed showed progressively higher trait specificity.  We confirmed that ASL CBF shows trait-like properties, which are optimally fit using eyes-open or eyes-closed conditions. 3627. 61 Evaluation of 3D GRASE and 2D MB-EPI for Multi-Delay PCASL Imaging Xiufeng Li, Xingfeng Shao, Dingxin Wang, Sudhir Ramanna, Steen Moeller, Kamil Ugurbil, Essa Yacoub, Danny Wang Recently 2D multi-band (MB) imaging has emerged as a promising alternative to 3D acquisitions for arterial spin labeling imaging. As part of the Human Connectome Project, we evaluated a segmented 3D GRASE and 2D MB-EPI for multi-delay PCASL imaging in terms of test-retest repeatability and CBF/ATT quantification. The results indicated that compared to 3D GRASE, 2D MB-EPI is less sensitive to subject motion, provided comparable but more reproducible ATT and CBF estimates, and suffered less from data loss. 2D MB-EPI appears promising for multi-delay PCASL imaging, especially with limited imaging time and where higher spatial resolution is of interest. 3615. 49 3D Whole-Brain Mapping of Cerebral Blood Flow using Velocity-Selective Pulse Trains: Evaluating Various Strategies for Background Suppression Qin Qin Velocity-selective arterial spin labeling (VSASL) has only been realized with 2D multi-slice acquisition. ASL with 3D readout is preferred for clinical applications and background suppression technique is essential for successful implementation of segmented 3D ASL. In this study, various strategies for background suppression are evaluated for 3D VSASL which are labeled with conventional T2prep VS pulse train, and new Fourier transform based velocity-selective saturation and inversion pulse trains, respectively. The optimal 3D whole-brain VSASL protocol is compared with PCASL for mapping cerebral blood flow on normal volunteers at 3T. 3622. 56 Improved Calculation of Arterial Blood Equilibrium Magnetization in Arterial Spin Labeling André Ahlgren, Ronnie Wirestam, Freddy Ståhlberg, Linda Knutsson, Esben Petersen The calibration factor (equilibrium magnetization of arterial blood) in arterial spin labeling is usually calculated by dividing a PD image with a constant brain-blood partition coefficient, $$\lambda$$$. A more accurate approach would be to divide a map corresponding to the PD of the perfused parenchymal tissue with a $$\lambda$$$ map (i.e, taking into account different values of $$\lambda$$$in different tissue types). In this work, we demonstrate how this can be achieved using partial volume (PV) estimates. In vivo results are demonstrated and compared with the conventional method. 3616. 50 Solving the dark-sides of multiband-ASL: A framework to correct for increased motion artefacts in MB-ASL due to sharp transitions in the level of background suppression Yuriko Suzuki, Thomas Okell, Wouter Teeuwisse, Sophie Schmid, Merlijn van der Plas, Michael Chappell, Matthias van Osch Recently, incorporation of multi-band (MB-) EPI into ASL has been reported, enabling increased spatial coverage without compromising SNR of distal slices due to longer post-labeling delay time. However, the combination of MB-EPI and ASL with the background suppression (BGS) could potentially induce problems when motion correction (MoCo) is required. In this study, we demonstrate that subtraction artefacts can be introduced when performing MoCo of MB-BGS-pCASL and that these artefacts can degrade image quality considerably. We propose a new framework that corrects for image degradation caused by MoCo of MB-BGS-pCASL data, thereby greatly improving robustness and thus usefulness of MB-BGS-pCASL. Electric Property Imaging & Clinical QSM Electronic Poster Contrast Mechanisms Monday, 24 April 2017  Exhibition Hall 16:15 - 17:15  Computer # 3639. 73 Investigating the relation between electrical conduction and tissue composition with proton and sodium MRI Stefano Mandija, Paul de Bruin, Andrew Webb, Peter Luijten, Cornelis van den Berg The focus of the presented work is to understand the relation between electrical conductivity and tissue composition in terms of 23Na concentration and water fraction. This would be relevant to evaluate the potential value of electrical conductivity imaging as a new endogenous biomarker and the validity of accessing conductivity from water content. For this purpose, MR-EPT and waterEPT conductivity reconstructions are performed and compared to network analyzer measurements. To evaluate whether conductivity is directly related to the total sodium concentration in free water, 23Na images are acquired at 7T and conductivity reconstruction are then performed using the Stogryn’s model. 3640. 74 CONtrast Conformed Electrical Properties Tomography (CONCEPT) based on Multi-channel Transmission Yicun Wang, Pierre-Francois Van de Moortele, Bin He Magnetic Resonance based Electrical Properties Tomography holds promise to provide valuable information on tissue functional changes, such as Tumorigenesis. We propose a novel technique based on multi-channel transmission to reconstruct quantitative electrical properties maps by exploiting the intermediate contrast information with jointly promoted sparsity. The resultant optimization problem was solved by Alternating Direction Method of Multipliers within seconds. Numerical simulations, phantom and human subject experiments were performed at 7T using a multi-channel transceiver coils array, demonstrating improved accuracy and visual outcome. CONCEPT does not rely on anatomical assumptions, and therefore represents a general approach suitable for broader applications. 3641. 75 Dictionary-based Electric Properties Tomography Ulrich Katscher, Max Herrmann, Christian Findeklee, Mariya Doneva, Thomas Amthor 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 applies db-EPT to numerical and experimental data comparing different types of dictionaries. 3642. 76 Spatial and Contrast Resolution of Phase Based MREPT Yusuf Ider, Gokhan Ariturk, Gulsah Yildiz Clarification of the contrast resolution (CR) and spatial resolution (SR) limits of phase based MREPT for conductivity imaging is essential for assessing its success success in clinical applications. Noise analysis of conventional phase based MREPT is performed to find the SNR needed for the MR sequence used for measuring B1-phase. It is found that with 1000-2000 SNR values about 0.01 S/m CR can be achieved. For SR evaluation, generalized phase based MREPT, which does not suffer from internal boundary artefacts, is considered. It is found by phantom experiments that 3.5mm spatial resolution is easily obtained with the state-of-art MR methods. 3643. 77 Adaptive Weighted Polynomial fitting in phase-based Electrical Property Tomography Jun-Hyeong Kim, Jaewook Shin, Ho-Joon Lee, Kang-Hyun Ryu, Donghyun Kim Weighted polynomial fitting method was proposed to resolve boundary artifact and noise amplification of Electrical Property Tomography. Weighted polynomial fitting method employs T1/T2 tissue contrast as prior information under assumption that pixels with similar magnitude intensity have similar conductivity. However, for non-simply connected structures make the fitting inaccurate. Therefore, in this study, we propose a modified weighted polynomial fitting technique including spatial constraint. 3662. 96 Changes in brain iron concentration after exposure to high altitude hypoxia by quantitative susceptibility mapping Lin Chen, Congbo Cai, Tianhe Yang, Jianzhong Lin, Shuhui Cai, Jiaxing Zhang, Zhong Chen Environmental factors may influence brain iron concentration. We investigated the changes of magnetic susceptibility and R2* values of cerebral regions especially in six deep gray matter nuclei of twenty-nine participants after high altitude exposure for four weeks. The results show that the susceptibility values of gray matter, especially in caudate nucleus, putamen, globus pallidus, substantia nigra, red nucleus, increased significantly. Traditional R2* maps verify the results of QSM evaluation except in red nucleus. Therefore, high altitude hypoxia can lead to significant increase of cerebral iron concentration. 3645. 79 In Vivo Mapping of Liver Tissue Damage using MR-based Conductivity Imaging Method Bup Kyung Choi, Nitish Katoch, Saurav Sajib, Jin Woong Kim, Hyung Joong Kim, Oh In Kwon, Eung Je Woo Liver tissues mainly consist of single cell, the variations of ion concentration and mobility inside the liver have similar pattern. This indicates that liver tissues can exhibit uniform distribution of electromagnetic tissue properties such as electrical conductivity. MREIT is typical method which can provide electrical conductivity information of suspicious tissue using a current-injection MRI method. Mapping of liver tissue damage using MREIT conductivity imaging may provide direct, immediate, and high sensitive information based on the changes of ion concentration and mobility at cellular levels. This study experimentally imaged in vivo liver tissue damage based on the changes of tissue conductivity. 3644. 78 Current Density Measurements in the Brain using Magnetic Resonance Electrical Impedance Tomography in Healthy Volunteers Aditya Kumar Kasinadhuni, Aprinda Indahlastari, Kevin Castellano, Christopher Saar, Casey Weigel, Bakir Mousa, Michael Schär, Munish Chauhan, Thomas Mareci, Rosalind Sadleir Characterizing current density distributions in the brain of healthy volunteers can provide important information to guide electrical stimulation therapies. Current-induced magnetic fields, produced as a result of electrical stimulation, can be mapped from phase changes in the MR imaging then current density can be computed using Maxwell’s equations. In this study, we present the first current density distribution induced magnetic field maps in healthy volunteers resulting from electrical stimulation using low frequency (10 Hz) transcranial alternating current simulation (tACS). 3646. 80 Data-Driven Background Phase Correction and Combination to Improve the Accuracy of MR-EPT with Multi-Channel Receivers Kathleen Ropella, Douglas Noll We propose a method for combining phase data from multiple receiver channels for phase-based conductivity mapping that does not require a reference scan or reference coil. The proposed method combines a background phase removal step, to reduce bias from individual coil phases, and local coil compression, which maximizes SNR in the combined phase data. 3647. 81 Volumetric Reconstruction of Tissue Electrical Properties from B1+ and MR Signals Using Global Maxwell Tomography: Theory and Simulation Results. Jose Serralles, Ioannis Georgakis, Athanasios Polimeridis, Luca Daniel, Jacob White, Daniel Sodickson, Riccardo Lattanzi Magnetic resonance-based inverse scattering has been proposed to extract tissue electrical properties (EP). We present an improved implementation of the Global Maxwell Tomography (GMT) EP mapping technique, with two new cost functions and an extension that uses piecewise linear basis functions to represent fields for higher accuracy. GMT does not make symmetry assumptions, is fully 3D, and is robust to noise. We validated the new GMT version with various numerical experiments, using a heterogeneous head model with realistic EP and a phantom with tissue-mimicking EP. We showed, for the first time, that artifact-free accurate reconstruction of EP is possible. 3648. 82 Longitudinal Atlas Construction for Normative Human Brain Development and Aging over the Lifespan using Quantitative Susceptibility Mapping (QSM) Yuyao Zhang, Hongjiang Wei, Naying He, Christian Langkammer , Stefan Ropele , Fuhua Yan, Chunlei Liu QSM is able to provide high contrast for iron-rich deep-brain nucleus. This is attributed to the sensitivity of magnetic susceptibility to the spatial variations of cellular components that exhibit different magnetic susceptibility properties, especially for brain iron and myelin. Although there have been atlases proposed for certain age groups, a longitudinal statistical atlas construction from general healthy population based on QSM is still lacking. We constructed longitudinal QSM atlases over the whole lifespan (from 1 to 83 years-old). One common QSM atlas is built for every 10-years interval to demonstrate the unique age-specific morphology and appearance of human brains. 3649. 83 Does Total Iron Content in Deep Brain Nuclei Really Increase in Healthy Aging? A Study Based on Quantitative Susceptibility Mapping. Yuyao Zhang, Hongjiang Wei, Naying He, Fuhua Yan, Chunlei Liu The crucial role of iron for normal neurological function in human brain has been well recognized. The iron concentration evolution trajectories in human brain deep nucleus have been shown monotonously increased with aging. However, previous studies concern only on iron concentration. At the same time, atrophy occurs in healthy ageing brains. These two competing effects raise an interesting possibility that the total iron content in deep brain nuclei may decrease. Surprisingly, the iron content, investigated by QSM, in globus pallidus, substantia nigra and red nuclei appear to decrease after the iron content reaching a peak. 3650. 84 Paramagnetic ions quantification using QSM and EPR in human brain - permission withheld Jeam Barbosa, Rafael Emidio, Ana Tereza Alho, Maria Otaduy, Edson Amaro, Fernando Barbosa Junior, Oswaldo Baffa Filho, Carlos Salmon QSM, R2* and R2 values for post-mortem intra and extra cranial human brain samples were statistically correlated with only total iron and Fe3+ present in ferritin. 3651. 85 Importance of reference in QSM and a new differential ROI reference method TaeHyun Hwang, JinGu Lee, JunYeol Choi, SangJoon Kim, GeonHo Jahng, Jongho Lee In this study, we developed a computer simulation to demonstrate the importance of reference in QSM. The results show that QSM values are substantially affected by spatial coverage for reconstruction. Only when the data are referenced using a neighboring region, the QSM results provide correct susceptibility values. Additionally, we suggest a new “differential ROI” reference method. This approach reports the susceptibility value as a difference between two (neighboring) ROIs. We demonstrate this new approach for a Parkinson’s disease patient study. 3652. 86 Quantitative susceptibility mapping with separate calculation in water and fat regions - permission withheld Ryota Sato, Toru Shirai, Yo Taniguchi, Takenori Murase, Atsushi Kuratani, Taisei Ueda, Takashi Tsuneki, Yoshitaka Bito, Hisaaki Ochi, Yoshihisa Soutome To reduce the calculation error and artifacts of susceptibility in the boundary region between water and fat, a new reconstruction method is presented and applied to a prostate QSM. In the proposed method, susceptibility maps of the water region and the fat region are calculated separately and differently and then combined. Numerical simulation and human prostate imaging using a 3T-MRI are performed to evaluate accuracy and artifacts of the proposed method. The results suggest that the proposed method reduces calculation error and the shading artifacts in the boundary region between water and fat near the prostate. 3653. 87 Localization of the implanted brachytherapy titanium seeds in presence of calcification on MR images using Quantitative Susceptibility Mapping (QSM) and 3D K-means clustering Reyhaneh Nosrati, Abraam Soliman, Alexey V. Dimov, Hirohito Kan, Gerard Morton, Ana Pejovic-Milic, William Song Post-implant dosimetry is an important quality assurance for prostate low-dose-rate (LDR) permanent seed brachytherapy. Despite the superior soft tissue contrast in MRI that is required for tumor delineation, there are some unresolved issues with seed depiction on MR images as they appear as signal void. In addition, calcified regions have similar characteristics on MR images making them indiscernible. This work investigates the feasibility of an MR-only workflow based on quantitative susceptibility mapping (QSM) and 3D k-means clustering for post-implant localization of the seeds. 3654. 88 Image Quality Improvement by Applying Retrospective Motion Correction on Quantitative Susceptibility Mapping and R2* Xiang Feng, Alexander Loktyushin, Andreas Deistung, Jürgen Reichenbach The aim of this study was to quantitatively assess the improvement of image quality on motion corrupted quantitative susceptibility mapping (QSM) and the effective transverse relaxation rate (R2*) maps, after applying retrospective motion correction. Image quality was assessed using the following metrics: SNR in different brain tissues, histogram analysis, and linear correlation between susceptibility and R2* values in subcortical structures. 3655. 89 In-vivo phase imaging of growing epiphyseal human cartilage at 7 T. Barbara Dymerska, Klaus Bohndorf, Paul Schennach, Alexander Rauscher, Siegfried Trattnig, Simon Robinson Growing epiphyseal cartilage of children contains vessels and more complex layer structure than adult hyaline cartilage. Phase imaging is sensitive to deoxyhemoglobin in venous blood and to orientation of magnetic tissues, but it is challenging since many established methods for combining and unwrapping data fail in the thin cartilage of the knee. In this study different phase reconstruction methods were tested at 7T and high resolution SWI was applied to visualize veins and collagen fiber architecture in healthy young subjects. 3656. 90 Comparison of quantitative susceptibility mapping methods for evaluating cerebral microbleeds at 3T and 7T Yicheng Chen, Clare Poynton, Suchandrima Banerjee, Janine Lupo There is a growing interest in using QSM to detect and quantitatively evaluate cerebral microbleeds (CMBs). We compared several algorithms proposed in recent years for QSM on patients with CMBs after radiation therapy at 3T and 7T by quantitatively analyzing the noise and contrast of the susceptibility maps. Although RESHARP+ iLSQR had the least noise among methods, CMB and vessel contrast were more affected by incomplete background field removal, especially at 7T. 3657. 91 Quantitative susceptibility mapping: phase images and microstructure Lukas Buschle, Christian Ziener, Michael Breckwoldt, Artur Hahn, Julia Bode, Björn Tews, Martin Bendszus, Heinz-Peter Schlemmer, Felix Kurz In this work, the effect of inhomogeneous microstructure on quantitative susceptibility mapping (QSM) is simulated for typical microstructural geometries. The results suggest that the susceptibility of blood-filled capillaries can not be measured using quantitative susceptibility mapping due to the symmetry of the local Larmor frequency around a capillary. However, numerical simulations show that the concentration of spherically-shaped magnetic particles (contrast agents) is determinable with QSM. These results are therefore essential for a detailed analysis of quantitative susceptibility images. 3658. 92 Variation of Regions of Interest (ROIs) using different tools for automatic ROI generation: The impact on reported magnetic susceptibility values in QSM Emma Dixon, David Thomas, Anna Barnes, Karin Shmueli Automatic Region of Interest (ROI) generation is useful for large clinical studies using Quantitative Susceptibility Mapping (QSM) as this allows mean susceptibility values for anatomical regions to be reported without manual intervention.Several methods to generate ROIs are compared in this work. We found that methods based on T1 contrast showed little variation whether a typical magnitude image from a susceptibility protocol or a structural MPRAGE image was used. An additional method based on a QSM atlas showed greater variability in ROIs. Mean susceptibility values for ROIs were shown to vary greatly depending on the method used to generate ROIs. 3659. 93 Positive visualization of MR compatible nitinol stent using a susceptibility-based imaging method Caiyun Shi, Xiaoyong Zhang, Shi Su, Hairong Zheng, Xin Liu, Guoxi Xie, Jim Ji Previous studies have demonstrated that a susceptibility-based positive contrast MR method exhibits excellent efficacy for visualizing MR compatible metal devices by taking advantage of their high magnetic susceptibility. However, the method was not evaluated in the visualization of stents. Therefore, the purpose of this study is to assess whether the susceptibility-based positive method can be used to visualize the nitinol stents, with the comparison of two typical MR positive contrast techniques, i.e., SUMO and GRASP. Experiment results showed that the susceptibility-based method provides much better visualization and localization of the stent than SUMO and GRASP. 3660. 94 Magnetic Properties of Skeletal Muscle at 7T Benjamin Tendler, Richard Bowtell The magnetic properties of skeletal muscle tissue were examined in a phantom consisting of a piece of muscle tissue embedded in agar. Frequency perturbation maps were generated from phase maps measured at 7T, with the phantom oriented at 29 angles to the external magnetic field. Using a novel minimisation technique, susceptibility and chemical exchange properties of the muscle tissue were obtained simultaneously. From this it was determined that skeletal muscle is significantly more diamagnetic than agar; there is a small anisotropic susceptibility component and a large, orientation independent positive offset within the tissue, hypothesised to be due to chemical exchange. 3661. 95 Correlations of SWI, QSM, and R2* map with neuromelanin and iron distributions from post-mortem human substantia nigra samples. Hansol Lee, Se Young Chun, Jae-Hyeok Lee, Sun-Yong Baek, HyungJoon Cho Spatial characterizations of neuromelanin and iron contents in human substantia nigra provide critical information in diagnosing and treating Parkinson's disease. In this work, MR investigations of susceptibility weighted imaging (SWI), R2* mapping, and quantitative susceptibility mapping (QSM) were performed with three post-mortem human substantia nigra samples at 7T and correlated with corresponding histological slides. Magnetization transfer (MT) based T1-weighted MRI technique was also conducted to validate its reputed neuromelanin sensitivity as well. QSM Technical Developments Electronic Poster Contrast Mechanisms Monday, 24 April 2017  Exhibition Hall 16:15 - 17:15  Computer # 3664. 98 QSM0 - QSM with automatic uniform CSF zero reference Zhe Liu, Yihao Yao, Yi Wang One challenge in Quantitative Susceptibility Mapping (QSM) identified in a recent QSM workshop is zero reference. Cerebrospinal fluid (CSF) with little cellular content has been a popular choice. However, current QSM often shows inhomogeneous CSF, which may be regarded as artifacts caused by surrounding anisotropic white matter fibers in the scalar dipole inversion. We propose a regularization of minimal CSF variation for projecting out CSF inhomogeneity artifacts. Our proposed new QSM incorporates automated segmentation and regularization specific to CSF and outputs susceptibility values with automatic and uniform CSF zero reference. Accordingly, we term this novel QSM method as QSM0 3665. 99 Susceptibility Mapping of the Dural Sinuses and Other Major Veins in the Brain Sagar Buch, Yongsheng Chen, E. Mark Haacke In QSM, every effort is made to reduce background field induced by the air-tissue interfaces. In this abstract, we propose a method to: correct the phase of boundary regions by using background field extrapolation methods such as Taylor expansion; preserve the internal phase for the superior sagittal sinus (SSS) and transverse sinuses using an arterial-venous (MRAV) image; and predict the phase outside the brain and SSS using forward modeling. Further, we combine these steps to obtain an estimate of the venous oxygen saturation levels inside dural sinuses. 3666. 100 Spatiotemporal dynamics of inter-subject magnetic susceptibility variations in the human brain Balint Sule, Robert Zivadinov, Jannis Hanspach, Michael Dwyer, Jesper Hagemeier, Nicola Bertolino, Dhaval Shah, Niels Bergsland, Ferdinand Schweser Magnetic susceptibility in the deep gray matter varies substantially between subjects of similar age or disease state. This work employs a blind source separation technique to 239 healthy controls to determine, without prior assumptions, the spatial patterns that drive inter-subject variation of magnetic susceptibility in the human brain. 3667. 101 Accelerated $$B_{0}$$$ Mapping Using "X" Sampling in $$k$$$-TE Space Xin Miao, Yi Guo, Krishna Nayak, John Wood High-resolution B0 mapping suffers from long scan time, and issues with phase-wraps. We present an acquisition and reconstruction technique that resolves both problems. We utilize “X” sampling in k-TE space, in which multiple phase-encoding lines are acquired exactly twice per TR. The echo spacing is shortest for central k-space and largest for outer k-space. A multi-scale reconstruction enables pixel-wise phase unwrapping. This technique may be particularly useful for quantitative susceptibility mapping (QSM), as it could a) shorten scan time while maintaining the sensitivity to high-order field variation and b) simplify phase-unwrapping, which are the key features of interest in QSM. 3668. 102 Tikhonov regularization aided quantitative susceptibility mapping of whole brain without background field removal Hongfu Sun, Yuhan Ma, M. Ethan MacDonald, G. Bruce Pike An advanced dipole field inversion method for whole brain quantitative susceptibility mapping (QSM) without a traditional background field removal step, is proposed. To aid this ill-posed inversion process and obtain successful QSM, a Tikhonov regularization of the local susceptibility distribution is included. It is shown that the proposed method (Tikhonov-QSM) can substantially suppress reconstruction artefacts. More importantly, Tikhonov-QSM does not require edge erosion like in other QSM methods involving background field removal steps, preserving the cerebral cortex of the final images. 3669. 103 A Fast Algorithm for Nonlinear QSM Reconstruction Carlos Milovic, Berkin Bilgic, Bo Zhao, Julio Acosta-Cabronero, Cristian Tejos This abstract presents a fast nonlinear solver for the QSM reconstruction using the total generalized variation regularization. The proposed method utilizes the alternating direction method of multipliers to obtain close-form solution to each sub-problem. To handle the non-linear data fidelity, a two-step algorithm is described, including a global optimum search and a local Newton-Raphson iteration. Compared to conventional linear solvers, nonlinear solutions reduce streaking artifacts and better handle noise in poor SNR regions. Reconstruction results are at least comparable to nonlinear MEDI in quality, but with an order of magnitude improvement in the computational efficiency. 3670. 104 Effect of Poisson kernel parameters on background field removal accuracy for QSM Debra Horng, Samir Sharma, Scott Reeder, Diego Hernando The Poisson Estimation for Ascertaining Local fields (PEAL) kernel is a recently-introduced method for background field removal in quantitative susceptibility mapping (QSM). The PEAL kernel is determined by two parameters: radius and spatial shift. The choice of these two parameters may have a substantial effect on the accuracy of background field removal. In this work, we assessed the effect of PEAL kernel size and shift on the accuracy of background field removal and susceptibility estimation. 3663. 97 Optimization of Preconditioned Total Field Inversion for Whole head QSM and Cardiac QSM Zhe Liu, Yan Wen, Pascal Spincemaille, Yi Wang Preconditioned Total Field Inversion (TFI) allows QSM for the entire head and chest. The preconditioner determines the TFI convergence. Can we choose a preconditioner that maximizes QSM quality within limited computational time? To answer this question, we conducted two numerical simulations specific to these applications to search for an optimal preconditioner. We found that preconditioner too small or too big for a targeted susceptibility distribution would have less computational acceleration and consequently greater errors for a given computational time. Our results here suggest that the optimal preconditioner should be identified to match the image content. 3671. 105 Discrete frequency shift signatures explain GRE-MRI signal compartments Shrinath Kadamangudi, Viktor Vegh, Surabhi Sood, David Reutens Ultra-high field GRE-MRI phase images present great promise for structural brain studies. Multi-echo GRE-MRI data has been shown to contain signal compartments, which may eventually be used to characterise brain microstructure. Existing studies considered three signal compartments, however it remains unclear how compartments co-localise throughout the brain. We compartmentalised the signal via frequency shift signatures in a mixture of grey-white matter brain regions and implemented quality of fit measures to select the most parsimonious model for each region. We utilised k-means cluster analyses to investigate signal compartment commonalities across different brain regions and found four dominant frequency shift signatures. 3672. 106 What causes streaking artifacts in QSM and how to efficiently suppress them? Liangdong Zhou, Jae Kyu Choi, Youngwook Kee, Yi Wang, Jin Keun Seo We provide a mathematical understanding for artifacts in QSM, particularly streaking artifacts. 1) The local field data can be decomposed into a dipole-compatible part and a dipole-incompatible part. 2) In spatially continuous space, the streaking-free susceptibility solution is obtained from the dipole-compatible field data only, and the dipole-incompatible data leads to artifacts defined by a wave propagator with z as time, specifically, streaking artifacts from granular noise and shadow artifacts from white matter noise error. Although it is not known how to filter out such dipole-incompatible data, its artifacts can be suppressed in regularization-based Bayesian methods such as MEDI, which can efficiently penalize streaking artifacts. k-space-truncation-based methods that generate additional dipole-incompatible data near the zero cone amplify streaking artifacts. 3673. 107 Imaging Cerebral Arteries and Veins using Susceptibility Weighted Imaging with Ferumoxytol Saifeng Liu, Jean-Christophe Brisset, Sagar Buch, Jing Jiang, E. Mark Haacke, Yulin Ge Susceptibility weighted imaging (SWI) has been widely used to image cerebral venous structures and in vivo iron content. However, it has not been used to image arteries, because of the lack of susceptibility contrast between arteries and the surrounding tissue. In this study, the susceptibility of the arterial blood was purposely modified to make it visible with SWI, by using the USPIO (ultra-small superparamagnetic iron oxide) agent Ferumoxytol. The purpose of this study is to determine the relationship between Ferumoxytol concentration and susceptibility using phantom and simulation studies, and compare these findings with those obtained from in vivo data. 3674. 108 Coherence Enhancement in QSM via Anisotropic Weighting in Morphology-Enabled Dipole Inversion Youngwook Kee, Pascal Spincemaille, Junghun Cho, Yi Wang The current regularization in morphology-enabled dipole inversion (MEDI) does not take into account orientation information in morphology between QSM and its corresponding magnitude image. In this abstract, we consider such orientation information to enhance structural coherence between the two images. In doing so, we achieve better image quality as well as higher RMSE (root mean square error) and HFEN (high frequency error norm) with respect to COSMOS and $$\chi_{33}$$$. 3675. 109 Improved Morphology Enabled Dipole Inversion for Quantitative Susceptibility Mapping by Using Prior Information Yihao Guo, Li Guo, Yingjie Mei, Jijing Guan, Yanqiu Feng Morphology enabled dipole inversion (MEDI) has been proposed to reconstruct QSM without obvious streaking artifacts at the smooth regions of susceptibility map. However, reconstruction errors or streaking artifacts near edges are not addressed by MEDI. In this work, we aim to improve MEDI by constraining the edges of susceptibility map with prior information. 3676. 110 Automatic venous vessel segmentation in high field, multi-echo SWI using Random Forests Albert Rechberger, Barbara Dymerska, Karin Poljanc, Georg Langs, Simon Robinson A method for automatic venous vessel segmentation is presented that uses a Random Forest classifier supplied with a number of appearance and shape features computed separately from magnitude images, phase images and QSMs of a multi-echo T2*-weighted GE scan. The importance of each feature, and thus each echo, is investigated.  The approach was tested on whole-brain 7T scans of four subjects, two of which were manually annotated, and was effective in segmenting both internal and surface veins. 3677. 111 Resolution and Coverage for Accurate Susceptibility Maps: Comparing Brain Images with Simulations Anita Karsa, Shonit Punwani, Karin Shmueli Magnetic Susceptibility Mapping is moving closer to clinical application. To reduce scan time, clinical images are often acquired with reduced resolution and coverage in the through-slice dimension. The effect of these factors has been studied using only balloon phantoms and downsampled brain images. Here, we used MR images acquired at low resolution or low coverage and compared these with images simulated in volunteers and a realistic numerical phantom. Simulated susceptibility maps were very similar to maps from acquired images. Our results show that low resolution and very low coverage both lead to loss of contrast and errors in susceptibility maps. 3678. 112 Phase processing for quantitative susceptibility mapping of regions with large susceptibility and lack of signal Véronique Fortier, Ives R. Levesque Phase unwrapping and background removal algorithms directly impact quantitative susceptibility maps. Phase processing techniques have been thoroughly studied for brain applications, but accuracy in the presence of large susceptibility and negligible signal, such as bone and air regions, is unknown. The performance of phase processing algorithms was evaluated quantitatively in simulations with a numerical head phantom and qualitatively in vivo in three head datasets. In these experiments, Laplacian-based unwrapping performed poorly. Accurate background removal remains an open question. Results suggest that Quality-Guided unwrapping should be preferred with background removal using Projection onto Dipole Fields. 3679. 113 Evaluation of air/bone segmentation using susceptibility-based imaging methods - permission withheld Emma Dixon, David Thomas, Anna Barnes, Karin Shmueli Due to the difference in magnetic susceptibility of air, teeth and bone, magnetic susceptibility mapping has the potential to enable segmentation of these regions despite the absence of direct MRI signal. Several methods have been described which attempt to calculate the magnetic susceptibility within air and bone. Two datasets are used to test the ability of these methods to distinguish between air and bone. The performance of all methods varied between datasets and depended strongly on the parameters selected. None of the methods performed consistently better across groups, but all showed potential to improve air/bone segmentation using susceptibility mapping. 3680. 114 A comprehensive assessment of methods for combining phase data from array radio-frequency coils at 7 T Simon Robinson, Korbinian Eckstein, José Marques, Berkin Bilgic, Siegfried Trattnig, Ferdinand Schweser Methods for combining phase data from array RF coils are quantitatively compared at 7 T. Of the reference-free approaches (which all leave arbitrary contributions to the total phase), the Virtual Reference Coil method yielded the best phase matching. The reference-free method COMPOSER removed non-B0-related phase but requires an artifact-free short echo-time reference measurement. Of the multi-echo methods, SVD, HIP and ASPIRE all had uniform phase matching. ASPIRE has higher CNR for a narrow range of echo times, but requires TE2=2 x TE1. The data and assessment scripts used in this study will be made publicly available. 3681. 115 Evaluation of Accuracy of MR phase and R2* for susceptibility quantification Yongquan Ye, Li Yang, Mengsu Zeng, Shengxiang Rao, Ying Ding, Jinguang Zong, Xixi Wen Computer simulation was performed to evaluate the relationship between a voxel's bulk susceptibility and its R2* or phase behavior. A virtual voxel with multi-dipole model was created, and the effects of dipole properties on the accuracy and consistency of R2* and phase on reflecting the voxel’s bulk susceptibility was investigated. Linearity is only observed at low bulk susceptibility regime, and phase is much more robust against various susceptibility dipole properties than R2*. 3682. 116 Texture analyses of quantitative susceptibility maps to differentiate patients with Parkinson’s disease from healthy controls Gaiying Li, Guoqiang Zhai, Xinxin Zhao, Hedi An, Tian Liu, Yi Wang, Dongya Huang, Jianqi Li QSM provides excellent contrast of iron-rich deep nuclei to quantify iron in the brains. Clinicians are interested in using QSM to diagnose patients with Parkinson’s disease (PD). Texture analyses of QSM images in substantia nigra (SN) was performed to differentiate PD from healthy controls (HC). Most of the texture parameters were significantly different between PD and HC. The second-order textures were more efficient in differentiating PD from HC than did the first-order ,which suggests that the second-order texture parameters are more suitable and sensitive for the diagnosis of PD. 3683. 117 Ultrashort Echo Time Quantitative Susceptibility Mapping (UTE-QSM): Limitations in Quantifying High Iron Concentration Xing Lu, Alexey Dimov, Qun He, Yajun Ma, Yi Wang, Eric Chang, Jiang Du Iron overload can affect not only the central nervous system, but the liver, pancreas, myocardium, endocrine glands, and musculoskeletal structures. A reliable quantitative method to detect and measure high concentration iron in vivo would be of great clinical utility. Ultrashort echo time (UTE) sequences have echo times (TE) 100-1000 times shorter than clinical sequences, and may detect signal from high iron concentration. In this study, we aimed to evaluate the capability of UTE-QSM sequence in quantifying high iron concentration with an Iron phantom study and the results show that UTE-QSM techniques can quantify high iron concentration up to 22 mM or higher. 3684. 118 Comparison of Quantitative Susceptibility Mapping algorithms based on numerical and in vivo 3T data Hanneke Geut, Louise van der Weerd, Itamar Ronen This study compares the currently publically available algorithms for quantitative susceptibility mapping, including different phase unwrapping, background field removal and dipole inversion methods. Numerical and human in vivo brain MRI data are used for a qualitative and quantitative assessment of the various methods. In 3T in vivo MRI data, phase unwrapping with combined spatial and temporal fitting and background field removal using V-SHARP results in the least artifacts. MEDI and iLSQR are currently the most accurate dipole inversion algorithms, with a significantly shorter processing time for the iLSQR method. 3685. 119 Biological underpinnings of different MR contrasts in the human midbrain using quantitative structural MR imaging at 9.4T: Validation with 14T ex-vivo measurements and PLI - video not available Joana Loureiro, Gisela Hagberg, Elisa Tuzzi, Rolf Pohmann, Zora Schickardt, Marc Himmelbach, Thomas Ethofer, Matthias Valverde, Wolgang Grodd, Klaus Scheffler In this study we use relaxometry and susceptibility mapping to obtain enhanced contrast in the midbrain, in particular in the superior colliculus (SC). High resolution GRE images were obtained in 11 subjects at 9.4T.  We calculated CNR values for each contrast for three midbrain regions (superior colliculus,red nucleus and aqueductal gray).  were  were obtained across 11 subjects in individual and MNI space. These measurement were validated with ex-vivo measurements in the 9.4T, 14.1T and PLI imaging. 3686. 120 Investigation of Brain Tissue Fixation on Iron Concentration, Magnetic Susceptibility and Effective Transverse Relaxation Rate Andreas Deistung, Verena Endmayr, Simon Hametner, Max Prihoda, Xiang Feng, Hans Lassmann, Jürgen Reichenbach, Simon Robinson, Evelin Haimburger, Christian Menard, Thomas Haider, Hannes Traxler, Siegfried Trattnig, Günther Grabner We investigated the effect of brain tissue fixation on iron concentration and on quantitative maps of the magnetic susceptibility and effective transverse relaxation rate (R2*). Both R2* and susceptibility distributions of unfixed and fixed tissue were found to be similar, indicating similar underlying proportions of iron across tissues. Quantitatively, however, severe decreases of iron concentration of 25% in putamen and about 15% in white matter were measured after tissue fixation. The iron concentration change due to tissue fixation was captured by R2* and susceptibility which needs to be considered when directly comparing experiments performed with unfixed and fixed brain tissue.

Relaxation: Methods & Others
Electronic Poster
Contrast Mechanisms

Monday, 24 April 2017
 Exhibition Hall 17:15 - 18:15

 Computer # 3722. 36 Model-Based Super-Resolution Reconstruction of T2 Maps Tom Hilbert, Jose Marques, Jean-Philippe Thiran, Reto Meuli, Gunnar Krueger, Tobias Kober We propose an algorithm that can reconstruct 0.9mm3 isotropic T2 maps based on multiple 2D multi-echo spin-echo acquisitions that were highly undersampled. The data is reconstructed by combining a classical super-resolution approach with an iterative model-based reconstruction. Thereby, the reconstruction problem is split into multiple sub-problems to improve the convergence of the algorithm. Resulting T2 values within structures of the midbrain and the hippocampus from four healthy volunteers showed good reproducibility. This kind of high-resolution relaxometry may enable additional insight in pathologies of small brain structures and increased sensitivity to disease-induced changes. 3734. 48 Kitchen Safe T1 and T2 Phantom Creation - video not available Kenneth Johnson, N Addy, Reeve Ingle, Michelle Nystrom, William Overall, Galen Reed, Juan Santos Typical magnetization prepared phantoms require paramagnetic salts such as copper, nickel and manganese chloride, which are toxic. Accordingly, governing bodies label these as hazardous materials requiring special storage, labeling and disposal. In search of a simpler and cheaper solution we have revisited this topic to make a kitchen-safe phantom recipe that is both cheap and easy to make. We used glycerine (a sweetener or for skin care) and Agar agar powder (a food additive for thickening or gel) to make phantoms with a physiological range of T1 and T2, and characterize these non-hazardous materials for 1.5 T MRI scanners. 3730. 44 Inversion-recovery Ultrashort Echo Time Imaging with Bi-component T2* Analysis of White Matter Signals in Native and Deuterated Ovine Brain Specimens Shu-Juan Fan, Yajun Ma, Eric Chang, Jiang Du Myelin protons have ultrashort-lived MR signals and are not accessible by clinical MRI. Such signals were probed herein using ultrashort echo time imaging (UTE) and inversion-recovery UTE (IR-UTE) with bi-component analysis in native and deuterated ovine brain specimens. UTE detected a fraction of ultrashort T2 components (STC) of < 4% in native specimens, and up to ~54% in deuterated specimens. Choice of inversion time in IR-UTE significantly affected such bi-component signal decay behavior in native samples in heavily deuterated samples. These results support the application of UTE and IR-UTE in quantitative myelin imaging. 3718. 32 Fast T1 mapping with temperature correction via DWI thermometry, and it application to vitreous oxygen measurement Shengwen Deng, Eric Muir, Wei Zhou, Timothy Duong T1 mapping is showing great potential for mapping oxygen in human organs such as eyes and lungs. And yet, accuracy of oxygen using fast T1 imaging methods is of great concern especially in tissue with radical temperature changes. In the current study we improve fast T1 mapping with temperature correction and explore its potential in mapping oxygen in eyes. With combination of inversion-recovery Look-Locker bSSFP and diffusion weighted thermometry, we calibrate the temperature dependence of ADC and T1, and use it to adjust the R1 for measuring partial pressure of oxygen(pO2). Fast T1 mapping could be a reliable way to pO2 that well agrees with invasive oxygen-sensitive optic fibers. 3721. 35 Quantitative 3D T1 mapping technique in rat brain using VFA-FLASH at 9.4T - permission withheld Hedok Lee, Simon Sanggaard, Kristian Mortensen, Palle Koch, Maiken Nedergaard, Helene Benveniste 3D whole brain T1 mapping technique at 9.4T is studied because of a lack of methodological consideration in spite of its utility in pre-clinical paramagnetic and manganese contrast enhanced imaging studies. We report a simple and accurate 3D T1 mapping technique using variable flip angles spoiled gradient echo sequence with B1+ correction. Accuracy of the technique was validated using phantoms and a population averaged 3D rat T1 map was constructed. 3725. 39 High-resolution 3D T2 mapping of the Brain Using T2-prepared Cartesian Spiral Phyllotaxis FLASH and Compressed Sensing Emilie Mussard, Tom Hilbert, Christoph Forman, Reto Meuli, Jean-Philippe Thiran, Tobias Kober Brain T2 relaxometry can provide sensitive biomarkers for pathological tissue alterations, especially inflammation. But their acquisition is often 2D-based and typically comes with long acquisition times. To improve through-slice resolution while keeping a clinically feasible scan time, we propose a centric T2-prepared variable-density Cartesian spiral phyllotaxis FLASH sequence combined with a compressed sensing reconstruction. Phantom experiments and a preliminary in-vivo scan show that T2 values can be reliably measured in 3D with high resolution. Parameter dependencies are evaluated and an initial protocol optimisation yields an acquisition time of 8.48min for a 1x1x1.2mm3 whole-brain acquisition. 3711. 25 Development of magnetic resonance fingerprinting (MRF) combined with FISP and multi-echo SPGR acquisition for proton density, T1, T2, T2* and field mapping. Dongyeob Han, Taehwa Hong, Dong-Hyun Kim  Magnetic resonance fingerprinting (MRF) is a novel technique which provides rapid proton density, T1 and T2 mapping. However, susceptibility related parameters such as T2* were not acquired simultaneously. In this study, FISP and multi-echo SPGR acquisition were combined within MRF scheme to allow proton density, T1, T2, T2* and field mapping. 3720. 34 Rapid high-resolution 3D T1 mapping using a highly accelerated radial inversion-recovery FLASH technique Zhitao Li, Ali Bilgin, Diego Martin, Maria Altbach A golden angle radial IR-FLASH technique and a principle component based iterative algorithm are developed for high-resolution T1 mapping using highly undersampled 3D radial data. The novel method yields T1 maps of a 3D volume with high spatial and temporal resolution and can cover 144 slices within 5 minutes. 3724. 38 Assessing the Accuracy of T2 and B1+ Maps Estimated from Multi-echo Spin Echo MRI Sequences Using Extended Phase Graph Signal Predictions Nuno Santos, Rui Teixeira, Joseph Hajnal, Rita Nunes Interpretation of T2-weighted images still remains highly reliant on subjective clinical evaluation. Quantitative mapping using the gold standard approach (single spin-echo), although appealing, remains unfeasible in clinical practice. Multi-SE sequences have emerged as viable solutions allowing much shorter scan times at the expense of signal contamination by indirect echoes.  A method based on the MR Fingerprinting concept has recently been proposed, estimating T2 and B1+ maps from pre-computed Echo Modulation Curves. This study evaluated the performance of this method performing Monte Carlo simulations followed by an in vivo acquisition. The method provided accurate T2 maps, despite highly biased B1+ estimates. 3719. 33 A rapid, whole-brain look-locker method for T1 mapping using inversion recovery EPIK N. Jon Shah, Seong Dae Yun Quantitative measurement of the T1 relaxation time is of great importance for the clinical diagnosis or optimisation of image contrast. Numerous Look-Locker method have been proposed for T1 mapping. One of them demonstrated by the community is TAPIR which has been shown to be fast and robust. However, TAPIR still demands substantial acquisition time for whole-brain coverage. This work aims to develop a fast Look-Locker method with whole-brain coverage on a basis of EPIK. It was shown that the proposed method acquired whole-brain T1 data (2.1 mm2resolution × 50 slices × 30 time-points) within 3.5 minutes. 3726. 40 Approaching the Limits of Imaging Brain Tissue with Ultra Short T2 Christoph Rettenmeier, V. Andrew Stenger A 3D radial UTE sequence optimized for the selective detection of fast relaxing tissue in the range of 500-60 μs using a composite hard pulse is presented. Its imaging properties on a T2-phantom are analyzed and used for the discussion of human brain images. 3713. 27 Whole Body Rapid T2 Quantification using Dual Echo Fast Spin Echo Kelly McPhee, Ashmita De, Alan Wilman We examine RF field variation on a modern 3T and illustrate T2 quantification using only PD and T2w fast spin echo images and a rapid flip angle map in the abdomen, spine, head, neck, and leg. Across the whole body at 3T or higher fields, RF field variation yields a wide variation in flip angles, requiring direct sequence modelling to achieve accurate T2. 3712. 26 Direct Relaxation Measurement from Clinical Sequences Kelly McPhee, Alan Wilman Through exact sequence response modeling using the Bloch equations, we propose direct extraction of quantitative T1 and T2 relaxation maps from standard clinical MRI sequences. This approach eliminates the need for excess specialized and complex sequences by measuring relaxation directly from clinical sequences.  We demonstrate this method to determine T2 and T1 using a standard brain protocol of fast spin echo images weighted by proton-density, T2 and FLAIR at 3 T. Our approach opens the door to wider use of quantitative MRI. 3731. 45 Novel nanogel-based MRI Contrast Agents Brendan Garrett, Simon Duckett, David Smith, Victor Chechik We present here the preparation and properties of new Gd3+-containing nanogel-based contrast agents. These gel nanoparticles are prepared by simple ionotropic gelation from sodium alginate and Gd3+.  The nanogels are 100-200 nm in diameter and have a high R1 relaxivity of ≈ 30 mM-1 s-1 at 1 T, however,  they have poor stability in high ionic strength media. Adding further covalent crosslinks with a suitable agent such as epichlorohydrin dramatically increased the relaxivity of the nanogels to ≈ 60 mM-1 s-1 at 1 T and provides a viable strategy to increases their stability against transmetallation. 3716. 30 Whole Body T1 Mapping of Small Animals using Prospective Gating and Variable Flip Angle Imaging Paul Kinchesh, Philip Allen, John Beech, Stuart Gilchrist, Ana Gomes, Veerle Kersemans, Robert Newman, Borivoj Vojnovic, Michael Brady, Ruth Muschel, Sean Smart Prospective gating and automatic reacquisition of data corrupted by respiration motion were implemented in variable flip angle (VFA) and actual flip angle imaging (AFI) scans to enable cardio-respiratory synchronised T1 mapping of the whole mouse. T1 calculation for each mouse took approximately 6 s using a robust and efficient nonlinear least squares process. 16 cardio-respiratory gated VFA scans and a respiration gated AFI scan were acquired in less than 14 minutes. T1 was calculated in the whole mouse with a voxel size of 0.075 mm3 and with a standard deviation less than 6.2% within ROIs from multiple organs. 3732. 46 Quantitative validation of Spin Echo and Magnetic Resonance Fingerprinting derived Proton Density using the qMRI Phantom Gregory Lemberskiy, Els Fieremans, Dmitry Novikov, Martijn Cloos Proton density (PD) measurements derived from single Spin Echo and PnP-MRF,  which is a fingerprinting protocol that enables simultaneous estimation of the excitation field (B1+), were validated using the ISMRM/NIST MRI system phantom that contains known D2O/H2O solutions at 14 different concentrations. We also expanded the PnP-MRF protocol by exploiting the symmetry between B1+ and the receive field, B1-, produced by a quadrature body coil at 3 Tesla in order to remove all B1 contribution from our PD. Ultimately, all methods showed remarkable correlation with the known water fraction from NIST samples (Pearson’s rho>0.99). 3723. 37 A time domain signal equation for multi-echo spin-echo sequences with arbitrary exciation and refocusing angle and phase Andreas Petrovic, Christoph Aigner, Rudolf Stollberger T2 quantification with multi-echo spin-echo sequences is often hampered by flip angle inhomogeneities and non-rectangular slice profiles. Here, we present a novel time domain signal equation for multi-echo spin-echo sequences with arbitrary excitation and refocusing flip angles and phases. To evaluate the equation simulations and phantom measurements were compared. Excellent agreement was found for the simulated and measured evolution of the transverse magnetization across the slice profile in a CP and a CPMG sequence. T2 mapping using the proposed signal equation and the incorporation of scanner specific RF pulse shapes will greatly improve T2 quantification accuracy. 3727. 41 Exploring the Utility of Temporal Phase Correction in Multi-Echo T2 Relaxation at 3T Emil Ljungberg, Alykhan Thobani, Thorarin Bjarnason, Piotr Kozlowski, Alexander Rauscher, Jing Zhang, Anthony Traboulsee, Cornelia Laule, Alex MacKay, Shannon Kolind T2 relaxation using combined gradient and spin echo (GRASE) is a fast and robust approach for myelin water imaging in vivo. For long echo trains, when the noise floor is reached, the magnitude signal will converge towards a non-zero mean due to the Rician noise characteristics of the magnitude data. This can give rise to artificial long-T2 components in analysis. In this study we employed temporal phase correction to multi-echo GRASE data and showed that for echo trains longer than 300ms, phase correction will effectively reduce artificial long-T2components, thus improving the ability to interpret the T2 distribution. 3728. 42 Correction of fixation effects in post-mortem T2 measurements using a kinetic tensor model Feng Qi, Samuel Hurley, Menuka Pallebage-Gamarallage, Olaf Ansorge, Martin Turner, Ricarda Menke, Sean Foxley, Karla Miller MRI of fixed post-mortem tissue can be used to relate MR signals to histopathology. However, MR relaxation parameters are altered by the process of fixation. We propose a “kinetic tensor” model that simulates the influx of fixative into the brain using diffusion tensor data, and demonstrate a correction by fitting a fixative concentration map to quantitative T2 measurements. Compared to correction methods based on distance-to-surface or isotropic diffusion, our approach captures an individual brain’s morphology and microstructure, both of which influence fixation. T2 maps corrected with the kinetic tensor model are more homogeneous than those with alternate corrections. 3733. 47 Toward 3D Printed, Anatomy-Mimicking, Quantitative MRI Phantoms Karthik Gopalan, Jonathan Tamir, Ana Arias, Michael Lustig We aim to design and build reproducible phantoms with anatomy-mimicking resolution and image contrast. We mix solutions of paramagnetic ions in agar gel to target specific relaxation parameters. Chambers for different tissue types are 3D printed and filled with the agar gels. Microfiber cloths are added to create additional high-resolution structure. We validate the ability to reproduce target relaxation values through spin-echo imaging and quantitative mapping, and present two 3D printed phantom designs. 3715. 29 Correction of off-resonance for T1 and T2 mapping using phase-cycled inversion-recovery balanced steady state free precession Eric Muir, Shengwen Deng Fast measurement of T1 and T2 can be made using inversion-recovery Look-Locker (LL) bSSFP methods. However, the LL-bSSFP signal is dependent on the off-resonance frequency which can affect calculated T1 and T2. In this study we develop and test methods to correct for effects of off-resonance on T1 and T2 calculation using multiple phase-cycled LL-bSSFP. The phase-cycled LL-bSSFP data could be combined with a maximum-T1* projection method to improve T1 and T2 accuracy in the case of off-resonance. 3717. 31 Motion Corrected T1 Mapping of the Pediatric Human Brain Steven Kecskemeti, Andrew Alexander A method to retrospectively correct both in- and through-plane motions that occur during the acquisition of inversion recovery images is developed and used for motion-corrected T1-mapping of the pediatric human brain.   Both intra- and inter-scan motions are corrected. 3729. 43 Ex vivo whole-blood $$T_2$$$versus $$HbO_2$$$ calibration for $$T_2$$\$-prepared balanced steady-state free precession (bSSFP) at 1.5T Ana Rodríguez-Soto, Michael Langham, Osheiza Abdulmalik, Felix Wehrli The transverse relaxation rate (1/T2) of blood water protons is governed by deoxyhemoglobin concentration, therefore providing a means to determine oxygen saturation (HbO2) in vivo. However, besides CPMG inter-pulse interval of the T2 preparation and field strength, whole-blood T2 depends on sequence-specific parameters. Balanced SSFP allows for rapid image acquisition and higher in-plane resolution and thus provides an ideal readout for T2-based oximetry. Here, we quantified T2 of human blood at 1.5T for the entire range of HbO2 saturation levels using T2-prepared bSSFP sequence. The data show the expected linearity of 1/T2 with (1-HbO2)2 with the y-intercept depending on hematocrit. 3714. 28 SNR Efficiency in Multi-Parameter Mapping (PD, T1 & T2*) at 3T: Comparison of MP2RAGE and VFA-FLASH Jean-David Jutras, Keith Wachowicz, Guillaume Gilbert, Nicola De Zanche Quantitative parametric mapping is becoming increasingly promising for improving the diagnostic quality and reproducibility of structural brain MR images. The variable flip angle technique with FLASH (VFA-FLASH) is a popular technique for mapping the proton-density, T1 and T2*. Recently, the MP2RAGE pulse sequence was developed to map T1 with robustness to RF inhomogeneity. If a multi-echo (bipolar) MP2RAGE is employed, proton-density and T2* can also be mapped simultaneously. In this study we compare the SNR efficiency and accuracy of VFA-FLASH and MP2RAGE for multi-parameter mapping at 3T. Both methods yield comparable T1-to-noise ratios, but VFA-FLASH is superior for PD and T2* mapping.

CEST/MT/NOE: Animal Models & Human Translation
Electronic Poster
Contrast Mechanisms

Monday, 24 April 2017
 Exhibition Hall 17:15 - 18:15

CEST: Acquisition, Quantification & Characterization
Electronic Poster
Contrast Mechanisms

Monday, 24 April 2017
 Exhibition Hall 17:15 - 18:15

Contrast Mechanisms: Miscellaneous
Electronic Poster
Contrast Mechanisms

Monday, 24 April 2017
 Exhibition Hall 17:15 - 18:15