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

 1877 -1898 Arterial Spin Labeling Applications 1899 -1923 DSC & DCE 1924 -1943 Relaxation: Mechanisms & Applications 1944 -1968 Electric Property Imaging & Susceptibility Imaging 1969 -1989 All Things CEST/MT

Arterial Spin Labeling Applications
Contrast Mechanisms

Tuesday, 25 April 2017
 Exhibition Hall 16:15 - 18:15

DSC & DCE
Contrast Mechanisms

Tuesday, 25 April 2017
 Exhibition Hall 16:15 - 18:15

 1900 Improving Simultaneous T1 and T2* Measurements for Dynamic Susceptibility Contrast MRI using a 3D Distributed Spirals Sequence Laura Bell, Dallas Turley, Natenael Semmineh, James Pipe, C. Quarles Multi-echo (ME) DSC-MRI enables the simultaneous assessment of contrast-agent induced T1 and T2* changes, but its sensitivity to and the quantification of these T1 changes could be confounded by long TR and TE. Using simulations, we demonstrate that conventional 2D ME scans underestimate contrast agent concentration and DCE-MRI kinetic parameters. To solve this problem, we propose a 3D ME spiral acquisition that enables lower TRs and minimal TEs for improved T1 quantification and a range of echo times to main T2* sensitivity. 1901 Joint DCE- and DSC-MRI processing using the Gradient correction model Ondrej Macícek, Radovan Jirík, Zenon Starcuk jr. The contribution presents a method for simultaneous processing of the DCE- and DSC-MRI perfusion data acquired using a multi-echo sequence. It is an extension of the sequential application of the so-called gradient correction model. In the sequential approach, relaxivity parameters are estimated from the DSC signal based on perfusion parameters calculated from the DCE signal. Here the perfusion and relaxivity parameters are estimated using an iterative alternating optimization strategy. The impact on accuracy and precision is tested on synthetic data. The results show that the suggested approach can yield a remarkable improvement, especially for noisy data. 1902 Correction of R2* Effects in Arterial Input Function of Fast Dynamic Contrast-Enhanced MRI for Accurate Cerebral Blood Flow Measurement Benoit Bourassa-Moreau, Réjean Lebel, Guillaume Gilbert, Martin Lepage Signal loss resulting from $$R_2^*$$$effects is usually neglected in fast dynamic contrast-enhanced perfusion imaging. A new flow-compensated 3D RF-spoiled dual gradient echo sequence was designed to quantify the $$R_2^*$$$ variation during a bolus injection of contrast agent and its effect on cerebral blood flow measurement. Moderate $$R_2^*$$effects are found to be amplified by the non-linear relationship between signal ratio and concentration. This is shown to lead to substantial changes in peak arterial input function and measured cerebral blood flow. 1903 Improved Arterial Input Function Measurements Using Phase-versus-Time and Modified Look-Locker Inversion Recovery: Phantom Validation Study Nicholas Majtenyi, Gregory Cron, Hanif Gabrani-Juma, Andreas Greiser, Robert deKemp, Ran Klein, Thanh Nguyen, Ian Cameron Dynamic contrast-enhanced (DCE)-MRI is used to quantify organ perfusion abnormalities in many diseases, but is prone to errors. This study investigated the accuracy of a new method for measuring the arterial input function (AIF) in a flowing-water phantom using phase-versus-time measurements with pre- and post-DCE Modified Look-Locker Inversion Recovery (MOLLI) T1 measurements (Phase+MOLLI). The Phase+MOLLI technique provides an important improvement over previous methods since it avoids signal saturation and gives correct [Gd] values for the washout of the AIF. The Phase+MOLLI method was validated to be accurate, reproducible, and flow-insensitive so that it may be used for clinical DCE-MRI. 1899 Optimization of Echo Times for CBV Measurements in the Arterial Input Function, Brain, and High-Grade Tumor Tissue using Error Analysis for DSC-MRI Laura Bell, Mark Does, Ashley Stokes, Leslie Baxter, Kathleen Schmainda, C. Quarles This abstract demonstrates that the optimal TE for a single-echo DSC-MRI acquisition is 30-35 ms (without a preload) and 23-30 ms (with a standard full-dose preload) for a high-grade glioma population. Optimal TEs were calculated using error analysis on T2* values quantified during the first-pass of contrast agent using dual-echo DSC, and were shown to be the weighted-average of these values. Furthermore, we demonstrate that the optimal TE depends on tissue type (tumor/healthy tissue/AIF) and preload. 1905 Impact of Reference Time Curve Determination on the Correction of Contrast Agent Extravasation in Dynamic Susceptibility Contrast MRI Mu-Lan Jen, Ping Hou, Jason Johnson, Donald Schomer, Ho-Ling Liu This study investigated the influence of reference time curve determination on DSC leakage correction. Our findings suggested that the reference time curve obtained with inclusion of leaky tissue could lead a significantly different in K2, which supported that the probable error in lesion blood volume quantification with inaccurate automated segmentation process. 1904 Dynamic Susceptibility Contrast MRI at 7T: Tail Scaling Analysis and Inferences About Field Strength Dependence Linda Knutsson, Xiang Xu, Freddy Ståhlberg, Peter Barker, Pia Sundgren, Peter van Zijl, Ronnie Wirestam In this study, a dynamic susceptibility contrast MRI (DSC-MRI) protocol for cerebral perfusion imaging at 7T was designed. With reduced contrast agent dose, the obtained perfusion maps showed the same visual appearance as seen at lower field strengths. In addition, a correction method was applied to obtain quantitative estimates of CBF and CBV in order to assess whether previous predictions of a field-strength dependence of the in vivo transverse relaxivity, leading to overestimated perfusion estimates, were supported. We concluded that assumptions of a field-strength dependence were plausible, based on observations of further elevated CBF and CBV estimates at 7T. 1906 Robust reference-region DCE-MRI analysis with a vascular component and two-fit analysis Zaki Ahmed, Ives Levesque The Extended Reference Region Model (ERRM) can quantify tumour perfusion without needing an arterial input function and includes a vascular term to account for the plasma volume. The addition of the vascular term also leads to larger variability in the estimated parameters. This study notes that one of the ERRM fitting parameters should be the same for all voxels. A two-fit approach is proposed that takes advantage of this constraint to reduce the number of fitting parameters from four to three. Evaluation in simulation and in-vivo found that the proposed two-fit approach resulted in a substantial decrease in variability for KTrans and kep estimates. 1908 Feasibility and value of View-shared Compressed Sensing combined fast DCE-MRI in quantitative evaluation of unilateral renal embolism in rabbits Hanjing Kong, Bin Chen, Hao Li, Bihui Zhang, Haochen Wang, Xiaodong Zhang, Min Yang, Jue Zhang, Xiaoying Wang, Jing Fang Dynamic-contrast enhanced MR imaging is widely employed as a clinical tool in kidney imaging and renal function measurements. Some novel works have been made in improve temporal resolution. In this work, we adopt a 3D Cartesian MRI with compresses sensing and variable view sharing sequence to explore its evaluation in renal embolism assessment. GFR was calculated and renal embolism was confirmed by histological results. Fast DCE-MRI is a promising method for renal embolism diagnose. 1910 Influence of parameter initial values on DCE parameter estimates in pharmacokinetic modeling: a simulation study Charlotte Debus, Ralf Floca, Amir Abdollahi, Michael Ingrisch In pharmacokinetic analysis of DCE-MRI data, the choice of initial parameter values for fitting has been reported to have a significant impact on the outcome of the optimization and hence, on parameter estimates. In this study, we investigated the influence of initial values by fitting simulated concentration time curves with varying combinations of initial parameters, using the two compartment exchange model. The resulting parameter estimates were visualized and compared to the true values, used for simulation, by means of relative errors. Results showed that the choice of initial values has little influence on the precision of the pharmacokinetic analysis. 1911 Nested tracer-kinetic model-based DCE-MRI reconstruction from under-sampled data Sajan Goud Lingala, Yi Guo, Naren Nallapareddy, Yannick Bliesener, R Marc Lebel, Krishna Nayak We propose a novel nested tracer-kinetic (TK) model based constrained reconstruction method for DCE-MRI reconstruction from under-sampled data. This approach models the concentration time profiles as a sparse linear combination of temporal bases constructed from TK models of varying complexity. Subspaces from the models of plasma volume, Patlak, and the extended-Tofts are constructed. A spatial mask determining the TK model complexity at every pixel location is derived. Reconstruction involves iteration between data consistency and pixel wise projection of the concentration profiles on one of the three subspaces. We demonstrate its utility in retrospective under-sampled reconstruction of brain tumor DCE-MRI datasets. 1909 Comparison of (k,t) sampling schemes for DCE MRI pharmacokinetic parameter estimation Yannick Bliesener, Sajan Lingala, Justin Haldar, Krishna Nayak We demonstrate an approach to evaluate and compare (k,t) sampling patterns for DCE-MRI. We compute Cramér-Rao lower bounds on the variance of pharmacokinetic (PK) parameter estimates, using pathologically- and anatomically-realistic digital reference objects. The framework allows for the optimization of sampling patterns independent of any specific estimator. We apply this framework to a 2D reference object for four sampling patterns: keyhole, TRICKS, lattice, and golden angle sampling. It is shown that TRICKS, lattice, and golden angle sampling enable low variance estimation for low undersampling factors. Out of these, lattice sampling keeps variances lowest with increasing undersampling factors. 1912 Measurement of Murine Single-Kidney Glomerular Filtration Rate using Dynamic Contrast Enhanced MRI Kai Jiang, Hui Tang, Prassana Mishra, Slobodan Macura, Lilach Lerman A method for noninvasive assessment of mouse glomerular filtration rate (GFR) using dynamic contrast enhanced MRI (DCE-MRI) was developed and validated. The kinetics of gadolinium in the abdominal aorta and two kidneys were measured using a snapshot fast low angle shot based T1 mapping method with a temporal resolution of 1 s. A modified bi-compartmental model was used for quantification of GFR by a least-squares fitting. As a reference standard, GFR was also measured using FITC-inulin clearance. Single-kidney GFR measured from both methods showed a good agreement, suggesting the proposed DCE-MRI method provides an accurate measurement of murine single-kidney GFR. 1913 Patlak analysis of dynamic gadoxetic acid-enhanced MR imaging is an effective and simpler alternative to compartmental pharmacokinetic modelling for assessing liver function Matthew Orton, Mihaela Rata, Dow-Mu Koh, Maria Bali, Robert Grimm, David Collins, James d'Arcy, Martin Leach Liver perfusion and function can be assessed using gadoxetic acid combined with DCE-MRI imaging and pharmacokinetic (PK) modelling. Whilst compartmental PK models give a good account of the contrast changes over the first five minutes of enhancement, the Patlak graphical approach is a simpler alternative that is more easily implemented. Patlak evaluation requires the specification of a delay time after which the initial transients in the uptake curves have decayed, so the purpose of this abstract is to present a preliminary evaluation of the sensitivity of liver uptake rate estimates to the Patlak delay time. 1907 Quantitative DCE-MRI Analysis using a Reference Tissue and AIF Tail Zaki Ahmed, Ives Levesque The reference region model can quantify tumour perfusion without needing an arterial input function (AIF) and provides relative estimates, i.e. KTrans/KTrans,RR and ve/ve,RR which are usually converted to absolute KTrans and ve by using literature-based values for KTrans,RR and ve,RR. However, this approach fails to account for inter-patient variability. This study proposes a method that uses the Reference Region and AIF Tail (RRIFT) to estimate patient-specific KTrans,RR and ve,RR. The AIF tail is the post-peak part of the AIF and is easier to measure than the complete AIF. Evaluation in simulation and in-vivo showed that RRIFT provides comparable results to Tofts model, and even outperforms the Tofts model at slower temporal resolutions. 1915 Absolute Quantification of Brain Perfusion using Golden Angle Compressed Sensing DCE-MRI Radovan Jirík, Marie Danková, Pavel Rajmic, Lucie Krátká, Lenka Dvoráková, Eva Dražanová, Zenon Starcuk, jr. A DCE-MRI method for absolute quantification of cerebral blood flow (CBF) and volume (CBV) and vessel permeability surface area product is presented. It is based on L+S compressed sensing, the two-compartment exchange model (2CXM) and blind deconvolution estimation of the arterial input function. The method is evaluated on data from a healthy rat. 1916 Parameters From Dynamic Contrast-Enhanced Magnetic Resonance Imaging Are Biomarkers Predicting Response after Radiation to Brain Metastases Zhuo Shi, Lizhi Xie, Peng Wang, Xinming Zhao, Han Ouyang Dynamic contrast-enhanced (DCE) MRI provides additional information regarding blood-brain barrier integrity, and Ktrans is directly proportional to the level of permeability of the blood-brain barrier. In our study, we found demonstrates that SRS of cerebral metastasis is associated with a reduction of Ktrans values in the early post-treatment period. DCE-MRI derived parameters of Ktrans may be a promising imaging biomarker of tumor aggressiveness. 1917 Quantification of tracer kinetic and hemodynamic parameters of human breast tumor and fibro-glandular tissue using DCE-MRI data Snekha Sehrawat, Pradeep Kumar Gupta , Meenakshi Singhal, Rakesh Kumar Gupta, Anup Singh Objective of current study was to develop a framework for computing tracer kinetic parameters using GTKM model and hemodynamic parameters using first pass analysis of human breast tissue for characterizing of breast lesion; and also differentiation of the histological grade II and III of breast cancer. A significant difference between benign, malignant and fibroglandular tissues; and also between grade II and III of breast cancer were observed. 1918 The Vanishing Shutter-Speed Limit Ruiliang Bai, Charles Springer, Jr., Peter Basser Dynamic-contrast-enhanced MRI (DCE-MRI) has been widely used to characterize microvasculature permeability. Recently, it was shown to reveal metabolic activity using the shutter-speed pharmacokinetic paradigm (SSP), in which steady-state intra/extracellular water exchange kinetics was incorporated into DCE-MRI data analysis. Interesting insights into DCE-MRI signals come from modeling the extravascular tissue MR signal. The questions addressed here are, “When can extravascular 1H2O longitudinal magnetization recovery from inversion/saturation still be described by a single-exponential process, and when can the intra/extracellular water exchange kinetics be accurately determined?” 1919 Whole Brain Dynamic Contrast-Enhanced MRI Study of Blood-Brain Barrier Disruption in Systemic Lupus Erythematosus Patients: Implications on the Choice of Tracer Kinetic Model Dennis Cheong, Mary Stephenson, Sen Hee Tay Current evidence suggests that blood-brain barrier (BBB) integrity is one of the potential biomarkers to diagnose neuropsychiatric systemic lupus erythematosus patients. We use DCE MRI and performed tracer kinetic analysis using both a distributed parameter (DP) model and the modified Tofts (MT) model. More Leaky BBB in SLE patients with anti-NR2 in their sera than the controls was detected by the permeability related parameters from both models. However, Ktrans of MT model, which is commonly used in DCE MRI of cancer studies, might be less reliable than DP model permeability parameters in this study. 1920 Feasibility and Value of Quantitative Dynamic Contrast Enhancement MR imaging in the Evaluation of Lymphoma and Inflammatory Pseudotumor in the Orbit Liyuan Song, Lizhi Xie, Junfang Xian This work assessed the feasibility of quantitative parameters derived from dynamic contrast enhanced MR imaging (DCE-MRI) and evaluated the value of quantitative dynamic contrast enhanced MR imaging in the differential diagnosis between lymphoma and inflammatory pseudotumor in the orbit.From the results we can see that it is feasible that quantitative parameters of DCE-MRI can be applied in the differential diagnosis between lymphoma and inflammatory pseudotumor in the orbit. Thus, it can probably be used as imaging biomarkers to predict prognosis and aggressiveness of orbital lymphoma. 1921 Assessment of hydrodynamics and T2 alterations in spontaneously hypertensive rat under short-term hyperhydration Kun-I Chao, Cheng-He Li, Sheng-Min Huang, Pei-Lun Yu, Kung-Chu Ho, Shang-Yueh Tsai, Ping-Huei Tsai, Fu-Nien Wang With a fluid infusion of 2% of body weight in the D2O perfusion imaging experiment, the tissues are expected in a hyperhydration state. In this study, we conduct both D2O and H2O infusion experiments on spontaneously hypertension rat (SHR). Fast and slow flow of brain were analyzed by a two-compartmental parallel model. Pre- and post-infusion T2 maps were acquired. The slow flow matched the T2 prolonged regions, which could be due to the CSF production and flow. 1914 Vastly accelerated linear least squares fitting with numerical optimization for dual delay compensated quantitative liver perfusion mapping Ramin Jafari, Yi Wang, Martin Prince, Pascal Spincemaille Accurate liver perfusion quantification requires correction for dual arterial and portal venous input delays, but such dual delay correction in current nonlinear perfusion methods is computationally too expensive to apply in perfusion mapping. We realize that the kinetic equation is a linear differential equation that would allow fast linear processing. Accordingly, we propose to use linear least squares (LLS) fitting to this kinetic equation with fast conjugate gradient search for processing dynamic contrast enhanced MRI data. Our proposed LLS vastly (~300 times) accelerate computation in perfusion quantification, enabling for the first time accurate liver perfusion mapping with dual delay corrections. 1922 Feasibility study of a Dialyzer as a multi-compartment Perfusion Phantom for microvascular tracer kinetic Modelling Tanja Gaa, Lothar Schad, Frank Zöllner Dynamic contrast enhanced MRI combined with tracer kinetic modelling allows for the determination of quantitative perfusion parameters. To achieve standardized examinations and data analysis, phantoms are employed to investigate the reproducibility of perfusion parameters by imitating tissue on capillary level. In this study we used a dialysis filter with a semipermeable membrane of the fibers which enables the simulation of two compartment kinetics and can thus serve as imitation of capillaries and interstitium which might be closer to the anatomical conditions. 1923 Feasibility of using Active Contrast Encoding (ACE)-MRI for Assessment of Tumor Treatment Response Jin Zhang, Willis Chen, Kerryanne Winters, Sungheon Kim Active Contrast Encoding MRI (ACE-MRI) is a recently proposed method to conduct DCE-MRI experiment without the need to perform separate T1 and B1 measurement. The purpose of this study is to further investigate the feasibility of using the ACE-MRI method for evaluation of tumor treatment response in a mouse model of breast cancer. The results of the ACE-MRI method were compared with conventional DCE-MRI data analysis with separately measured T1 maps. Our preliminary results demonstrate that the ACE-MRI method can be used to evaluate tumor treatment response reliably. Relaxation: Mechanisms & Applications Traditional Poster Contrast Mechanisms Tuesday, 25 April 2017  Exhibition Hall 16:15 - 18:15  1937 Quantitative relaxation time mapping of axillary lymph nodes and recommended parameters for 3T lymphatic node substructure imaging Rachelle Crescenzi, Paula Donahue, Vaughn Braxton, Allison Scott, Manus Donahue A lack of MRI methods exist that are designed with sensitivity to the lymphatics, even though components of the lymphatic system have been discovered in every major organ system of the body and likely play an understudied role in disease. In this work we performed quantitative relaxation time mapping in axillary lymph node substructures, the cortex and hilum, for the first time at 3 Tesla and used these values to optimize structural imaging parameters for the lymphatics. Knowledge of fundamental MR parameters in the lymphatics is the first step to developing novel imaging sequences that exploit lymphatic tissue in vivo. 1926 MR Contrast Effects of Intrinsically Gd-chelated Melanin Nanoparticles at 1.5 and 11.7 Tesla Soojeong Cho, Weiguo Li, Andrew Larson, Dong-Hyun Kim The development of polymeric contrast agents exhibiting a high MR relaxivity has been achieved using bio-inspired metal chelating melanin nanoparticle (Mel NP) synthesized with dopamine or L-3,4-dihydroxyphenylalanine (L-DOPA). In here, we described our simple one-pot synthesis to prepare new Gd chelated Mel NP and their specific features of efficient MR T1 imaging along with their high intrinsic Gd chelation efficiency. 1933 Development and Systematic Analysis of 2D and 3D GRE Myelin Water Imaging Hyeonggeol Shin, Se-Hong Oh, Jongho Lee In this study, we developed high quality GRE-MWI methods for 2D and 3D acquisitions and performed systematic analysis on TR and flip angle. The myelin water images showed that image quality was higher in 2D than in 3D. Over a range of TR (56 ms to 1630 ms), the myelin water fraction was uniform when Ernst angles (assume T1 of 800 ms) were used. The fractions were overestimated when larger flip angles were used. 1924 Accurate Tissue Oxygen Level-dependent MRI with true T1-weighted signal SoHyun Han, HyungJoon Cho, Seong-Gi Kim Tissue oxygen level dependent (TOLD) MRI utilizes that T1 is directly related with tissue pO2. TOLD MRI is acquired by gradient echo based with a minimized TE. However, T2* contribution may not fully be suppressed. Here, we investigated the modulations of longitudinal and transverse relaxation times with oxygen challenge (OC) and compared TOLD signals from FLASH, UTE, and TSE at 7 T and 15.2 T. At both magnetic fields, T2 did not change with tissue pO2 while T1 did. Spin echo and UTE appear to reflect true pO2 levels due to invariability in T2 during OC and minimized T2* with ultrashort TE, respectively. 1927 Effect of vendor specific formalin composition and concentration on post-mortem MRI of human brain tissue Christoph Birkl, Martin Soellradl, Anna Toeglhofer, Johannes Haybaeck, Lukas Pirpamer, Franz Fazekas, Stefan Ropele, Christian Langkammer Formalin fixation is common procedure to prevent tissue autolysis by crosslinking proteins. Not unexpectedly this affects the relaxation properties of the tissue. In addition, quantitative relaxation time constants of formalin fixed brain tissue show a broad variation across different studies. To investigate the contribution of the formulation of formalin to this variability we investigated MR relaxation times of pure formalin solutions from different vendors and the effect of formalin concentration on MR relaxation times of fixed brain tissue. Our results showed a strong variation of relaxation times depending on the concentration used and more importantly on the vendor specific composition of the formalin solutions. 1940 Determination of Oxygenation Extraction Fraction for People with Sickle Cell Anemia using Calibration Model Specific to SCA Blood Wenbo Li, Xiang Xu, Peiying Liu, John Strouse, Hanzhang Lu, Peter van Zijl, Qin Qin For the blood T2-based MRI oximetry methods, the calibration model to convert blood T2 to blood oxygenation (Y) is critical to calculate the brain oxygen extraction fraction (OEF). Here, we established a calibration model specific to people with sickle cell anemia (SCA) using in vitro blood T2 measurements on SCA blood samples under various conditions. The results show that the use of calibration models based on normal blood underestimate Y, and thus overestimate OEF, for individuals with SCA. Using a fast T2 protocol to measure oxygenation in the internal jugular vein (IJV), the whole-brain OEF values of individuals with SCA were determined and compared with healthy volunteers. 1928 Relaxation time shortening by oxygen molecules: Strong enhancement in a viscous solution with cellular viscosity Masayuki Taguchi, Toru Yamamoto Since oxygen molecules are paramagnetic, they shorten the relaxation time as well as gadolinium contrast medium. The effect of relaxation time shortening by the paramagnetic substance is enhanced with an increase in viscosity of the solution as in the cell. We investigated the longitudinal and transverse relaxivities of oxygen in viscous solution with cellular viscosity and clarified that the relaxation time shortening by oxygen molecules strongly increases with an increase in viscosity. This effect of oxygen in the cell may be visible by using pulse sequences that enhance the signal from the cellular proton. 1929 Characterization of the Four Pool Model in formalin-fixed sheep's brain using NMR spectroscopy Alan Manning, Alex MacKay, Carl Michal Despite its importance, T1 relaxation in brain and spinal cord is not well understood. The Four Pool Model gives a fundamental framework for its understanding in white and grey matter tissue. In this work, we characterize the Four Pool Model for the first time in formalin-fixed sheep's brain using NMR spectroscopy. We find this is a suitable system, and our results are consistent with previous studies: T1 is multi-exponential and the values measured result from a convolution of pure relaxation and exchange processes. 1930 Transverse relaxation of cerebrospinal fluid depends on glucose concentration Alexia Daoust, Steven Dodd, Govind Nair, Nadia Bouraoud, Stephen Jacobson, Stuart Walbridge, Daniel Reich, Alan Koretsky Brain relaxometric properties are widely used by the NMR community. While brain tissue relaxivities are well established, much less work has been done on CSF relaxivities. To clarify this point, we characterized the CSF relaxometric properties at various field strengths in vivo and in vitro. Our results suggest that low field is more optimal to quantify CSF T2 due to smaller residual gradients. There is a significant difference between in vitro CSF T2 vs saline T2 that is mostly explained by the glucose relaxivity. This finding was confirmed in vivo, opening the possibility of studying glucose regulation of CSF at the resolution of MRI. 1931 Origin of Dipolar Effects - Achilles Tendon at 3T and 11.7T. Nikolaus Szeverenyi, Jiang Du, Graeme Bydder We examined the MR image appearance of human Achilles tendon as a function of orientation to the B0 field at 3 T and 11.7 T. Images were registered and displayed a remarkable similarity in the fine discernable structural features at both field strengths. Residual dipolar effects are responsible for the contrast on these images, rather than frequency changes that scale with magnetic field. 1935 Spatial distribution of myelin concentration in healthy volunteers measured in GRE myelin water imaging, ViSTa myelin water imaging, quantitative MT and DTI Dongmyung Shin, Sehong Oh, Jongho Lee This study investigated the spatial distribution of several myelin imaging methods. Myelin water fraction in GRE-MWI, apparent MWF in ViSTa-MWI, fractional pool size (F) in qMT, MT saturation, MT ratio, and FA in DTI were compared for their spatial distribution in white matter. Strong correlations were measured particularly between GRE-MWI and ViSTa-MWI and also among MT contrasts. FA showed least correlations with the other parameters. 1932 Effect of T1 on Multi-echo Gradient Echo based Myelin Water Fraction Hongpyo Lee, Yoonho Nam, Dong-Hyun Kim, Hongpyo Lee Myelin Water Fraction uses the property that myelin water has shorter T2* relaxation time compared to axonal/extra-cellular water. Previous studies found that not only the T2/T2* relaxation time but also the T1 relaxation time is difference between these compartments. The T1 relaxation time of myelin water is known to be affected by the cross-relaxation therefore the term “apparent T1” is considered more accurate. In this study, we analyze the effect of this ‘apparent’ T1 in mGRE based MWF. Our results show that the MWF estimation is dependent on the differential T1 of different compartments. T1 effect on the MWF can makes overestimation error. Using the low flip angle could reduce the this error, but it gives rise to insufficient SNR on MWF. Also, increasing TR could be another choice for reducing estimated error, but it leads to inefficient scan time. Thus, GRE-MWF is needed to compensated T1 effect for accurate quantification. 1939 Hemodynamic response to respiratory challenge evaluated by dynamic R2’ imaging: application for acute renal ischemia caused by microsphere-induced renal artery embolism Chengyan Wang, Bihui Zhang, Haochen Wang, Hanjing Kong, Fei Gao, Li Jiang, He Wang, Xiaodong Zhang, Min Yang, Jue Zhang, Xiaoying Wang, Jing Fang The clinical use of iodinated or gadolinium contrast agents for renal hemodynamic imaging is limited in the presence of renal dysfunction due to its increased risks of exacerbating renal damage. Therefore, we performed a modified HRI technique with a specific-designed magnetic-susceptible sequence that could separate R2’ from the BOLD signals in a unilateral microemboli-induced AKI model. The results show that R2’ in normal or less affected regions reduced after carbogen challenge, while the R2’ in the most affected lesions increased significantly. The dR2’ map could indicate the most affected areas accurately confirmed with the final anatomic T2w image. 1938 Relaxation Times and Magnetic Susceptibility of Human Umbilical Cord Blood at 3 Tesla Sharon Portnoy, Natasha Milligan, Mike Seed, John Sled, Christopher Macgowan With an increasing proportion of fetal cardiovascular MRI scans being performed at 3 Tesla, there is growing need for an accurate calibration, which characterizes relationships between MRI properties (T1, T2, susceptibility) and blood properties (oxygen-saturation, sO2 and hematocrit, Hct) at 3T. Accordingly, relaxometry measurements were performed at 3T on cord blood specimens (N=89) with a broad range of hematocrits (0.09 Electric Property Imaging & Susceptibility Imaging Traditional Poster Contrast Mechanisms Tuesday, 25 April 2017  Exhibition Hall 1944-1968 16:15 - 18:15  1944 On the feasibility of synthetic sodium MRI based on tissue conductivity Nazim Lechea, Yu Peng Liao, N. Jon Shah The recently proposed magnetic resonance electrical property tomography opens new opportunities for sodium ion characterisation. In this study, a model was built by measuring electrical conductivity and sodium MRI in different saline solutions. We exploit this interdependence with additional temperature correction to build a synthetic sodium brain map based on in vivo electrical conductivity. The results were compared to sodium MRI measurements. A statistically significant Pearson correlation (p<0.001; r=0.43) was observed between the two modalities while Bland-Altman analysis revealed discrepancies between them with a mean difference ~4mMol/L in whole brain. The proposed approach facilitates tissue sodium extraction. 1945 Advanced 3D simultaneous conductivity and susceptibility imaging with mitigation of nonlinear phase evolution effect. Kang-Hyun Ryu, Jaewook Shin, Hongpyo Lee, Dong-Hyun Kim Simultaneous Quantitative conductivity and susceptibility mapping (QCSM) can acquire both 3D conductivity and 3D susceptibility map with a single scan 3D multi-echo GRE sequence. However, error occurs due to nonlinear phase evolution in some regions producing false values especially for conductivity. In this study, we analyzed this effect and propose a way to mitigate this effect. 1946 Evaluation of dual-echo EPI for in-vivo current mapping in individual subjects during transcranial Direct Current Stimulation Mayank Jog, Lirong Yan, Kay Jann, Lucas Parra, Marom Bikson, Danny Wang Transcranial Direct Current Stimulation (tDCS) is a neuromodulation technique that uses milliampere currents to modulate cortical excitability. Although tDCS has been shown to treat clinical symptoms and improve cognition, the distribution of tDCS currents in the brain remains unknown. Here we show a MRI technique that measures a component of the magnetic field induced by tDCS currents in-vivo. Experimental data acquired using this technique is compared to model-based simulations. Our results demonstrate that mapping the tDCS current-induced magnetic fields in individual subjects is feasible; opening an avenue to map electric currents directly and track target engagement in individual subjects. 1947 A stabilized convection-reaction magnetic resonance electrical property tomography (crMREPT) using viscosity-type regularization Changyou Li, Wenwei Yu, Shao Ying Huang Convection-reaction MREPT (crMREPT) method is a more general approach to reconstruct an electrical property map based on B1-maps from a magnetic resonance imaging (MRI) scanner compared to other existing methods in the literature, such as electrical property tomography (EPT) and local Maxwell tomography (LMT). However, crMREPT shows global spurious oscillations in the reconstructed maps and persistent artifacts in the region when $$\small\triangledown|B_1|$$  is small. We propose a solution to effectively mitigate the artifacts by applying a viscosity-type regularization. This abstract shows that the proposed method significantly increases the accuracy of the reconstructed electrical property maps and reduces the sensitivity to noise comparing to crMREPT. 1948 Three-Dimensional Model-Based Conductivity Mapping with Regularization and a Non-Negativity Constraint Kathleen Ropella, Douglas Noll We present a three-dimensional model-based approach to calculating conductivity using MRI. Our proposed method is formulated as an inverse problem based on the phase-based conductivity equation. The algorithm includes an edge-preserving regularization term and we explore the utility of non-negativity constraints. Structural information is also used to inform regions over which to regularize. We present results for simulation, phantom, and human brain data. 1949 Use of Padding to Eliminate Low Convective Field Artifact in Conductivity Maps Obtained by cr-MREPT Gulsah Yildiz, Gokhan Ariturk, Yusuf Ider Convection-reaction equation based Magnetic Resonance Electrical Properties Tomography (cr-MREPT) has been developed by Hafalir et.al; however Low Convective Field causes artifacts. This study investigates how padding can be used in practice to eliminate the LCF artifact in conductivity reconstructions. Simulation and experimental results are given to demonstrate that conductivity images are improved by padding. 1950 In Vivo Current Density Distribution of Brain during Electrical Stimulation Nitish Katoch, Bup Kyung Choi, Saurav Sajib, Jin Woong Kim, Hyung Joong Kim, Oh In Kwon, Eung Je Woo In deep brain stimulation, in vivo mapping of brain response is indispensable to secure its clinical applications. Estimation of current density distribution by stimulating currents can provide alternative way for understanding the therapeutic effects in electrical stimulation. MREIT method enables high-resolved mapping of electromagnetic tissue properties such as current density and conductivity of living tissues. In this study, we experimentally imaged current density distribution of in vivo canine brains by applying MREIT to electrical stimulation. The resulting current pathway and volume activation may provide useful information for adjusting the surgical planning and proving the therapeutic effects of DBS. 1951 Conductivity Measurements at 21.1 T using MR Electrical Property Tomography Ghoncheh Amouzandeh, Jens Rosenberg, Samuel Grant This study explores the opportunity of using ultra-high field (21.1 T) for producing electrical conductivity maps. Phantoms with known NaCl concentrations were used to compare conductivity maps generated by phase-based MREPT with actual values measured at 900 MHz with a dielectric probe. Phase-based MREPT also was evaluated for in vivo ischemic brain using an MCAO rat model. Increased conductivity values were noted in the stroked region of the rat brain. 1952 Current density imaging using novel carbon electrodes proposed for Deep Brain Stimulation (DBS) Munish Chauhan, Neeta Ashok Kumar, Fanrui Fu, Rosalind Sadleir Deep Brain Stimulation (DBS) is popular in the treatment of movement disorders. Conventional metal DBS electrodes present MR safety and susceptibility problems. We implemented novel carbon fiber electrodes that produced low susceptibility artifacts for imaging DBS current densities at 7 T. We used Magnetic Resonance Electrical Impedance Tomography (MREIT) to measure the z-component of the magnetic flux density (Bz) resulting from DBS-like pulses and reconstructed projected current density maps (JP) in two objects (agarose-gelatin phantom and ex-vivo piglet brain). We did not observe susceptibility artifact, and reconstructed projected current density maps agreed with simulation in the electrode neighborhood. 1953 Quantitative Susceptibility Mapping of Paramagnetic and Diamagnetic Substances at 3T-MR, 1.5T-MR and CT. Yasutaka Fushimi, Kyoko Takakura, Tomohisa Okada, Takuya Hinoda, Aki Kido, Kaori Togashi We compared QSM value of paramagnetic and diamagnetic substances at 3T-MR, 1.5T-MR, and CT in this study. Phantoms with different concentration gadoterate meglumine (Gd) and calciumcarbonate (CaCO3) were created. QSM at 3T and 1.5T and CT imaging were performed for these phantoms. QSM of Gd phantom showed positive susceptibility and QSM of CaCO3 showed negative susceptibility. QSM demonstrated consistent results in paramagnetic and diamagnetic substances at 3T and 1.5T. QSM and CT values were correlated well. 1954 Susceptibility Mapping Reveals Inter-Hemispheric Differences in Venous Density in Patients with Brain Arteriovenous Malformations Emma Biondetti, Alvaro Rojas Villabona, Anita Karsa, Rolf Jäger, David Thomas, Karin Shmueli Brain arteriovenous malformations (AVMs) are vascular abnormalities characterised by arteriovenous shunting with the lack of a capillary bed. Recent studies have shown that it is possible to create diagrams of the cerebral vein network (venograms) from images of magnetic susceptibility ($$\chi$$$). Here, we used $$\chi$$$-based venograms to calculate the hemispheric percentage of venous voxels (venous density) in each hemisphere in AVM patients and healthy subjects. We found larger venous densities in the AVM-containing hemispheres than in the contralateral hemispheres, and more variable venous density in AVM patients than in healthy subjects. 1955 Evaluating The Accuracy of Susceptibility Maps Calculated from Single-Echo versus Multi-Echo Gradient-Echo Acquisitions Emma Biondetti, Anita Karsa, David Thomas, Karin Shmueli For Susceptibility Mapping (SM), Laplacian-based methods (LBMs) can be used on single- or multi-echo gradient echo phase data. Previous studies have shown the advantage of using multi-echo versus single-echo data for noise reduction in susceptibility-weighted images and simulated data. Here, using simulated and acquired images, we compared the performance of two SM pipelines that used multi- or single-echo phase data and LBMs. We showed that the pipeline that fits the multi-echo data over time first and then applies LBMs gives more accurate local fields and $$\chi$$$maps than the pipelines that apply LBMs to single-echo phase data. 1956 A Robust 3D Phase Unwrapping Method with Application to Quantitative Susceptibility Mapping Junying Cheng, Biaoshui Liu, Yingjie Mei, Yihao Guo, Maodong Chen, Xiaoyun Liu, Wufan Chen, Yanqiu Feng In susceptibility-weighted imaging and quantitative susceptibility mapping, phase unwrapping methods are generally needed to restore the underlying true phase from the principal period (-π, π]. However, current phase unwrapping algorithms are challenged by noise, rapid phase changes and open-end cutlines. In this paper, a 2D phase unwrapping method based on pixel clustering and local surface fitting (CLOSE) was extended to 3D. The simulation and in vivo data is used to test the performance of the proposed method, with a comparison to a region growing method and PRELUDE, which are widely used for human brain phase-related imaging. The proposed method is demonstrated that can accurately unwrap 3D phase data even in the presence of severe noise, rapid phase changes, and open-end cutlines, and will benefit phase-related 3D MRI applications. 1957 Iterative Background Phase Correction: Recovering Data for QSM Johannes Lindemeyer, N. Shah We present a technique to improve the preparation process of phase data for QSM. In order to compensate for data loss caused by strong local phase gradients near the surface of the brain support, harmonic and dipole-based fitting are used to determine the responsible background fields within an extended brain mask. In an iterative approach, phase data are corrected regarding such contributions prior to further QSM processing steps. This allows for the acquisition of more reliable field maps and larger evaluation masks, which finally leads to more robust susceptibility maps. 1958 Incorporating macroscale susceptibility in QSM reconstruction with 3D spiral acquisition. Giang-Chau Ngo, Berkin Bilgic, Borjan Gagoski, Bradley Sutton Macroscale magnetic susceptibility creates large variations in the phase images preventing the direct analysis of local tissue-dependent phase in quantitative susceptibility mapping. Unwrapping and background field removal are important steps for calculating tissue phases and susceptibility maps. In this work, a 3D spiral acquisition is combined with an image reconstruction pipeline modelling the macroscale magnetic susceptibility to provide more accurate tissue phases and susceptibility maps, by reducing image distortions and facilitating unwrapping and background phase removal. 1959 Effects of Spatial Resolution on Quantitative Susceptibility Mapping Timothy Colgan, Samir Sharma, Diego Hernando, Scott Reeder The purpose of this study was to investigate the effects of spatial resolution on the performance of quantitative susceptibility mapping (QSM). The combination of magnitude contrast in spoiled gradient echo images and the voxel sensitivity function can create significant errors in the estimated B0 field map. This work evaluated the use of proton density weighted imaging and joint R2* and field map estimation to reduce the impact of imaging resolution on QSM. Our results indicate that reducing magnitude contrast in the complex-valued echo images will reduce errors in the field map estimates and, thus, the susceptibility estimates in QSM. 1960 Evaluation of Quantitative Susceptibility Mapping for the visualization of the Globus Pallidus Internus and Subthalamic Nucleus at 3T and 7T Fei Cong, Zhangyan Yang, Xiaohong Zhou, Bo Wang, Yan Zhuo, Lirong Yan The globus pallidus internus (GPi) and subthalamic nucleus (STN) (Figure 1) were the commonly used nuclei in deep brain stimulation (DBS) for the treatment of the Parkinson disease. In this study, we evaluated the QSM, T2* weighted and SWI methods for the visualization the GPi and STN on both 3T and 7T scanners. Our results showed the QSM at 7T displayed an excellent delineation of the GPi and STN, compared with T2* and SWI images. 1961 Primal-Dual Implementation for Quantitative Susceptibility Mapping (QSM) Youngwook Kee, Kofi Deh, Alexey Dimov, Pascal Spincemaille, Yi Wang We investigate the computational aspects of the prior term in the field-to-susceptibility inversion problem for QSM. Providing a spatially continuous formulation of the problem, we analyze 1) its Euler-Lagrange equation that appears degeneracy and 2) the Gauss-Newton conjugate gradient (GNCG) algorithm that employs numerical conditioning. We propose a primal-dual (PD) formulation that avoids such degeneracy and use the Chambolle-Pock algorithm to solve this alternative formulation; thus numerical conditioning is not required. The two methods were tested and validated on numerical/gadolinium phantoms and ex-vivo/in-vivo MRI data. The PD formulation with the Chambolle-Pock algorithm was faster and more accurate than GNCG. 1962 The challenge of phase offset correction for quantitative susceptibility mapping at ultra-high field Steffen Bollmann, Simon Robinson, Kieran O'Brien, Viktor Vegh , Andrew Janke, Lars Marstaller, David Reutens, Markus Barth One challenge in quantitative susceptibility mapping (QSM) at ultra-high field (> 3 T) is the combination of phase data from phased array receive coils. We assessed the performance of COMPOSER (COMbining Phase data using a Short Echo-time Reference scan) with separate reference scans and with an intrinsic reference scan, as well as a reference-free single-channel method. Our results show that reference scans can bias QSM results at ultra-high field. We conclude that ultra-short echo-time reference scans reduce quantitation bias and remove the transmit field phase when using COMPOSER to combine phase data at ultra-high field. 1963 Accuracy of magnetic resonance based susceptibility measurements Hannah Erdevig, Stephen Russek, Slavka Carnicka, Karl Stupic, Kathryn Keenan We examined the accuracy of MR-based susceptibility quantification relative to conventional measurements in preparation of making a standard susceptibility phantom. SQUID magnetometry of tissue mimics provides absolute accuracy of approximately 100 ppb while MR-based techniques give relative accuracy of 10 ppb. 1964 Quantification of Dendronized Superparamagnetic Iron Oxide Nanoparticles in Rat Liver Using Quantitative Susceptibility Mapping Jeam Barbosa, Imen Miladi, Patrick Poulet, Kofi Deh, Yi Wang, Carlos Salmon Quantitative Susceptibility Mapping was environment independent to quantify iron of SPIONs compared with R2*. 1965 Assessment of melanin content and its influence on susceptibility contrast in melanoma metastases Sina Straub, Frederik Laun, Martin Freitag, Christian Kölsche, Heinz-Peter Schlemmer, Mark Ladd, Till Schneider Melanoma metastases can be classified as melanotic or amelanotic based on their T1-weighted magnetic resonance signal. However, the underlying contrast mechanisms have remained unclear and have been attributed to melanin and/or blood products. In this study, non-hemorrhagic cerebral melanoma metastases were investigated using quantitative susceptibility mapping. Susceptibility values for metastases with no, small or high melanin content were very similar (-0.023±0.046 ppm / -0.006±0.02 ppm / -0.018±0.017 ppm). Non-hemorrhagic melanoma metastases show weakly diamagnetic susceptibility values and melanin is not a source of strong susceptibility. 1966 A Simple Phase Imaging REconstruction method (ASPIRE) Korbinian Eckstein, Siegfried Trattnig, Simon Robinson Combining phase data from multi-channel coils at high field is challenging. Many approaches involve optimization or iterative steps which require offline reconstruction. We present a simple method that avoids the need for unwrapping or other fragile or time consuming steps by using echo times that satisfy $$T_{E,2}=2\,\cdot\,T_{E,1}$$$. ASPIRE is compared with the Roemer method, MCPC-3D-I and the Hermitian inner product. ASPIRE achieves similar phase matching quality to Roemer but has the advantage that the combined phase values correspond to the B0 field. It is less computationally demanding than MCPC-3D-I and has higher CNR than the Hermitian inner product. 1967 Enhancing Quantitative Susceptibility Mapping by Using Gradient L2 Regularization with Morphological Priors Yihao Guo, Li Guo, Yingjie Mei, Yanqiu Feng TKD, LSQR and CSC methods have been proposed to reconstruct QSM from field map. However, these three methods result in inconsistent in the magic angle and can be further improved. This work introduces efficient gradient L2 regularization with morphological information from magnitude images for enhancing the QSM reconstructed by TKD, LSQR and CSC methods. 1968 Functional and structural ex vivo “MRI staining” using manganese-enhanced MRI (MEMRI), Gd-DTPA and Mn-Gd mixture Chika Sato, Kazuhiko Sawada, David Wright, Tatsuya Higashi, Ichio Aoki To reveal brain 3D microstructures noninvasively and microscopically using MRI, we developed “ex vivo MEMRI” and Mn-Gd double-contrast methods, and then compared them with conventional ex vivo Gd-DTPA-doped contrast. Because MEMRI sample loses contrast after perfusion fixation, we examined the stability of Mn2+ accumulation in ex vivo tissue samples. In addition, we tried to improve the contrast of MEMRI in combination with Gd-DTPA. The Mn-Gd double-contrast showed novel contrast and improved visibility. The functional “MRI staining” methods we developed in this study will be useful for visualizing whole brain 3D microstructures with a higher throughput compared to histological staining.

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