Rajiv S Deshpande^1,2, Michael C Langham², and Felix W Wehrli^2
1Dept. of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States, ²Dept. of Radiology, University of Pennsylvania, Philadelphia, PA, United States

A T₂-based oximetry pulse sequence has been developed by interleaving a phase-contrast module preceding a background-suppressed T₂-prepared echoplanar imaging readout. The method enables rapid simultaneous measurement of blood flow velocity and T₂ of blood water protons from a single anatomic location in 18 seconds scan time. The pulse sequence improves on T₂-based oximetry methods, including T₂-relaxation-under-spin-tagging (TRUST), by incorporating background-suppression to eliminate the need for “control” and “label” images. The pulse sequence also interleaves phase-contrast MRI so that a separate measurement of blood flow velocity is not required to quantify whole-organ metabolic rate of oxygen.

Tomoki Amemiya¹, Suguru Yokosawa¹, Yo Taniguchi¹, Ryota Sato¹, Hisaaki Ochi¹, and Toru Shirai^1
1Healthcare Business Unit, Hitachi, Ltd., Tokyo, Japan

We proposed a method to acquire venous and arterial image in addition to maps of multiple MR parameters (T1, T2*, proton density, and susceptibility) at the same time. The method applies venous extraction to susceptibility map obtained in previously developed multiple parameter mapping method using RF-spoiled gradient echo. The venous image of the proposed method were similar to those of conventional method. The result suggests that the proposed method enables simultaneous acquisition of arterial and venous images with quantitative MR parameter maps, and it may contribute to more efficient MR examination.

Ronald J Beyers¹, Adil Bashir¹, and Thomas S Denney^1
1MRI Research Center, Auburn University, Auburn University, AL, United States

CMR T2-mapping is needed to assess myocardial edema after such events as acute myocardial infarction, myocarditis and tako-tsubo cardiomyopathy.  Many T2mapping sequences have been developed, but most suffer from design shortcuts that degrade their accuracy, consistency and prognostic value. T2maps from four-point T2 curve-fits at end-systole (ES) would have maximum wall thickness and fewest artifacts for better prognostic value.  We present a new sequence that produces accurate four-point T2maps at ES within a 24-second breathhold at 3T.  This sequence was tested on phantoms and healthy human volunteers to present superior results.

Paul Han¹, Thibault Marin¹, Vanessa Landes², Yanis Djebra^1,3, Georges El Fakhri¹, and Chao Ma^1
1Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States, ²GE Healthcare, Boston, MA, United States, ³LTCI, Télécom Paris, Institut Polytechnique de Paris, Paris, France

Spoiled gradient echo (GRE) is an attractive alternative to balanced steady-state free precession (bSSFP) for ECG-gated recovery (IR)-based volumetric myocardial T₁ mapping at 3T. However, the robustness of T₁ estimation from spoiled GRE-based ECG-gated IR acquisitions has not been thoroughly investigated under different schemes and in the presence of B₁ inhomogeneity. This work investigated effects of B₁ inhomogeneity in the context of T₁ estimation, considering B₁ inhomogeneity in the model for T₁ estimation, and characterized effects of flip angle and heart rate to optimize a spoiled GRE-based ECG-gated IR acquisition scheme for 3D cardiac T₁ mapping.

Laura Saunders¹, Paul J. C. Hughes¹, James Eaden¹, Andy J Swift¹, Stephen Bianchi², and Jim M Wild^1
1Infection Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom, ²Sheffield Teaching Hospitals NHS, Sheffield, United Kingdom

Lung T₁ is sensitive to lung pathology, tissue and perfusion, and can be used to the calculation of quantitative DCE perfusion metrics. However, no comparisons have been made of common MRI T₁ mapping sequences in the human lung. The aim of this work was to compare Look-Locker and variable flip angle T₁ mapping sequences in phantoms and in vivo, in the lung, liver and blood. T₁ measured in the phantom, blood and liver was significantly lower when measured using a Look-Locker acquisition than VFA, whereas lung T₁ was significantly higher when measured using Look-Locker acquisition than when measured using VFA.

Weibo Gao¹, Quanxin Yang¹, Xin Chen¹, and Xiaocheng Wei^2
1Radiology, Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi, China, ²MR Research, GE Healthcare, Beijing, China

In this study, we aim to investigate whether different parameters of synthetic MRI can be used for the prediction of prognostic factors and molecular subtypes of breast cancer. It was concluded that SD of PD-Pre, SD of PD-Gd, T2-Pre, T2-Gd, T1-Pre and PD-Pre can be used as quantitative imaging biomarkers for the different receptor status of breast cancer. Among them, SD of PD-Pre, SD of PD-Gd, T2-Pre and T2-Gd were significantly different molecular subtypes, which worth further study. 

Weibo Gao¹, Xin Chen¹, Quanxin Yang¹, and Xiaocheng Wei^2
1Radiology, Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi, China, ²MR Research, GE Healthcare, Beijing, China

In this study, we aim to investigate the performance of quantitative measurements from synthetic MRI and DWI as well as their combinations in differentiating malignant from benign breast lesions and to compare with BI-RADS. Quantitative T2, PD and ADC values were significant lower in malignant than that of benign breast lesions. Quantitative multi-parameters of T2+PD+ADC had the best performance compared to all the other quantitative plans and BI-RADS. The approach, without contrast agents that combined synthetic MRI and DWI outperformed BI-RADS and may serve as an alternative and effective strategy for the improvement of breast lesion differentiation.

Julie Camille DiCarlo^1,2, Anum S Kazerouni³, and Thomas E Yankeelov^1,2,4,5,6
1Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX, United States, ²Livestrong Cancer Institutes, The University of Texas at Austin, Austin, TX, United States, ³Department of Radiology, University of Washington, Seattle, WA, United States, ⁴Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States, ⁵Department of Diagnostic Medicine, The University of Texas at Austin, Austin, TX, United States, ⁶Department of Oncology, The University of Texas at Austin, Austin, TX, United States

Pharmacokinetic modeling of DCE-MRI is based on fitting perfusion parameters to contrast agent concentration or relaxivity curves computed using the nonlinear spoiled gradient-echo (SPGR) signal equation, T₁ mapping values, and the linear relationship between T₁ and contrast agent relaxivity. The nonlinear term of the SPGR equation has implications for how image noise scales in the concentration.  By simulating image noise at different levels for ideal curves of different parameter values, we show why it’s advantageous to fit signal intensity curves rather than relaxivity curves.

John Charles Waterton^1,2
1Centre for Imaging Sciences, University of Manchester, MANCHESTER, United Kingdom, ²Bioxydyn Ltd, MANCHESTER, United Kingdom

Liver R₁ was surveyed in vivo in 3464 subjects at 16 field strengths from 106 publications.  R₁ was plotted against B₀ and fitted both to a biophysical model, and to a log-log heuristic. An investigator who wishes to compare their own findings with prior literature, and who finds their average liver R₁ to be within 9% of our fit, with between-subject CoV <8%, can conclude that their study is consistent with the majority of the literature.  

Sirisha Tadimalla^1,2, Daniel J Wilson³, Margaret A Saysell⁴, Martin John Graves⁵, Iosif A Mendichovszky^6,7, Geoffrey JM Parker⁸, and Steven Sourbron^2,9
1Institute of Medical Physics, The University of Sydney, Sydney, Australia, ²Department of Biomedical Imaging Sciences, The University of Leeds, Leeds, United Kingdom, ³Department of Medical Physics and Engineering, Leeds Teaching Hospital NHS Trust, Leeds, United Kingdom, ⁴Cardiac MRI, Leeds Teaching Hospitals NHS Trust, Leeds, United Kingdom, ⁵MR Physics and Radiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom, ⁶Department of Radiology, University of Cambridge, Cambridge, United Kingdom, ⁷Department of Nuclear Medicine, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom, ⁸Bioxydyn, Manchester, United Kingdom, ⁹Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom

A multi-centre, multi-vendor study in 8 travelling healthy volunteers was conducted for technical validation of variable flip angle (VFA) T₁ mapping in the liver across 6 scanners (3 vendors and 2 field strengths). The 95% CI was 28±8% for the bias in VFA liver T₁, 10±3% for the intra-scanner repeatability CV and 28±6% for the inter-scanner reproducibility CV. These values are comparable to B₁⁺ corrected VFA T₁ in prostate, brain, and breast. Any proposed refinement of the VFA method in the liver should demonstrate a significant improvement on those benchmarks before it can be recommended as a future standard.

Qiang Wei¹, Nan Wang¹, Ailian Liu¹, Qingwei Song¹, Renwang Pu¹, Lihua Chen¹, Jiazheng Wang², and Liangjie Lin^2
1The First Affiliated Hospital of Dalian Medical University, Dalian, China, ²Philips Healthcare, Dalian, China

Ultrashort echo time (UTE) imaging is a valuable technique for imaging short T2 and T2* samples. While the mDIXON-quant sequence enables reliable separation of water and fat signals, and measurement of fat fraction. With introduction of multiple echo acquisition, both the UTE and mDIXON-quant sequence can be used for measurement of the quantitative R2* values. This study investigated the correlation between R2* values measured by UTE and mDIXON-quant sequences. Results show that a moderate correlation between R2 values by the two methods, and R2* values measured by UTE were slightly higher than those by mDIXON-quant.

Arthur Peter Wunderlich^1,2, Eva Leithner¹, Richard Fiedler³, Meinrad Beer¹, Stefan Andreas Schmidt¹, and Mika Lindén^3
1Dept. of Diagnostic Radiology, Ulm University, Medical Center, Ulm, Germany, ²Section for Experimental Radiology, Ulm University, Medical Center, Ulm, Germany, ³Institute for Inorganic Chemistry II, Ulm University, Ulm, Germany

Liver R₂* determined with a breath hold GRE sequence is commonly used to address liver iron content in vivo. However, iron occurs in the body bound to various chemical substances. To study influence of chemical composition on R₂* on a clinical MRI scanner, we scanned mixtures of two iron compounds, polymer coated nanoparticles on the one hand and diluted Fe³⁺ ions on the other, at different concentrations of both compounds. We found that the relaxivity of one compound depended on the concentration of the other, suggesting that the interactions between compounds are more complex than previously assumed.

Shawyon Chase Rohani^1,2, Cara Morin¹, Xiaodong Zhong³, Stephan Kannengiesser⁴, Joseph Holtrop¹, Ayaz Khan¹, Ralf Loeffler^1,5, Claudia Hillenbrand^1,5, Jane Hankins⁶, and Aaryani Tipirneni Sajja^1,2
1Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, United States, ²Department of Biomedical Engineering, The University of Memphis, Memphis, TN, United States, ³Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States, ⁴MR Application Development, Siemens Healthcare, Erlangen, Germany, ⁵University of New South Wales, Sydney, Australia, ⁶Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN, United States

Radial acquisitions are less motion sensitive and a viable alternative in patients unable to breath-hold. This study investigates a free-breathing 3D Radial Dixon technique to assess HIC by validating with 3D Cartesian Dixon and biopsy-calibrated 2D GRE method. All three acquisitions showed excellent correlation with each other. The free-breathing 3D Radial Dixon produced sharper images whereas the 2D GRE and 3D VIBE Cartesian-based techniques exhibited motion artifacts and a slight underestimation in R₂^* values compared to 3D Radial VIBE likely due to motion artifacts.

YANLI JIANG¹, Pin Yang¹, FengXian Fan¹, Wanjun Hu¹, Jing Zhang¹, and Shaoyu Wang^2
1Department of Magnetic Resonance, LanZhou University Second Hospital, LanZhou, China, ²MR Scientific Marketing, Siemens Healthineers, Shanghai, China

The aim of this study was using B1 corrected native T1 value to assess their diagnostic accuracy for staging of liver fibrosis. We found that native T1 values increased with the  level of liver fibrosis, and a positive correlation was found between liver FibroScan results and the native T1 values. In conclusion, the B1 corrected native T1 values might be useful for staging of liver fibrosis.

Gabriela Belsley¹, Damian J. Tyler¹, Matthew D. Robson^1,2, and Elizabeth M. Tunnicliffe^1
1Oxford Centre for Clinical Magnetic Resonance Research, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom, ²Perspectum, Oxford, United Kingdom

Correcting B1+ inhomogeneities is imperative in T1 mapping using a VFA 3D SPGR sequence. We compared B1+ mapping using a preconditioning RF (preRF) pulse and TurboFLASH readout against B1+ mapping using a 2D double angle method (DAM) with EPI readout. The preRF method had a residual B1+-related variation in the T1 maps of 143ms, 95% CI [135, 150] and 170ms, 95% CI [158, 181] for 2 healthy volunteers while the DAM reduced these, with B1+-related variations of -27ms, 95% CI [-33, -20] and -8ms, 95% CI [-18, 2].

Hao Peng^1,2, Liwen Wan¹, Qian Wan¹, Jianxun Lv¹, Chuanli Cheng¹, Yi Wang³, Wenzhong Liu², Xin Liu¹, Hairong Zheng¹, and Chao Zou^1
1Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology,Chinese Academy of Sciences, Shenzhen, China, ²Key Laboratory of Imaging Processing and Intelligence Control, School of Artificial Intelligence and Automation, Huazhong University of Science & Technology, Wuhan, China, ³Department of Radiology, Peking University Peoples Hospital, Beijing, China

Fat-water ambiguity is an intrinsic problem from chemical shift encoded imaging model. When this problem is not well solved throughout the whole image, fat-water swaps appear and result in inaccurate fat quantification. The success of solving the ambiguity relies on pre-assumptions, e.g. the magnetic field continuity or the prior knowledge of the adipose/aqueous tissue distribution etc. In our work, we proposed to incorporate the T1 difference of fat and water to help solve the ambiguity problem. Proposed method can obtain PDFF and accurate T1 mapping simultaneously with B1+ correction. The sequence could cover the whole liver within a single breath-hold. 

Qianfeng Wang¹, Hong Xiao², He Wang^1,3, and Fuhua Yan^2
1Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China, ²Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ³Human Phenome Institute, Fudan University, Shanghai, China, Shanghai, China

In this study, R1ρ images of 24 rat liver samples were acquired with 2D UTE-R1ρ pulse sequences. The results showed that mean R1ρ values displayed dispersion, with decrease in R1ρ at higher FSLs. Spearman’s correlation analysis (two-tailed) indicated that the R1ρ values were significantly associated with liver iron concentration at all 6 spin-lock frequencies (all r > 0.8 and all P < 0.001).

Qianfeng Wang¹, Hong Xiao², Xuchen Yu¹, He Wang^1,3, and Fuhua Yan^2
1Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China, ²Department of Radiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ³Human Phenome Institute, Fudan University, Shanghai, China, Shanghai, China

In this study, T1ρ images of 24 rat liver samples were acquired with two types of pulse sequences: RARE and UTE. The mean T1ρ value of the rat liver with RARE was significantly higher compared to UTE (p<0.001). This study shows that the quantitative UTE-R1ρ has a better correlation with LIC than RARE-R1ρ.

Mahesh Bharath Keerthivasan^1,2, Jean-Philippe Galons², Diego Martin³, Ali Bilgin^2,3,4, and Maria Altbach^2
1Siemens Medical Solutions USA Inc, New York, NY, United States, ²Medical Imaging, University of Arizona, Tucson, AZ, United States, ³Biomedical Engineering, University of Arizona, Tucson, AZ, United States, ⁴Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States

Turbo spin-echo based T2 quantification of neoplasms is affected by partial volume effects resulting in underestimation of T2 values leading to lesion misclassification. Bi-exponential models proposed for two-component T2 estimation do not account for flip angle variations across the excited slice due to RF imperfections. This work presents a two-component model for accurate T2 estimation in the presence of partial volume which considers the slice profile of the excitation and refocusing pulses. The proposed model has <4% relative error in slices affected by partial volume and allows good separation between benign and malignant lesions in the abdomen.    

Nathan Tibbitts Roberts^1,2, Ruvini Navaratna^1,3, Diego Hernando^1,3, and Scott B Reeder^1,3,4,5,6
1Radiology, University of Wisconsin - Madison, Madison, WI, United States, ²Electrical and Computer Engineering, University of Wisconsin - Madison, Madison, WI, United States, ³Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, ⁴Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States, ⁵Medicine, University of Wisconsin - Madison, Madison, WI, United States, ⁶Emergency Medicine, University of Wisconsin - Madison, Madison, WI, United States

Chemical shift-encoded (CSE) MRI allows for measurement of important tissue parameters with established and emerging quantitative MRI applications, including proton density fat fraction (PDFF) and R2*. Respiratory and bulk patient movement can affect the accuracy and precision of CSE-MRI measurements, which makes rapid and motion robust imaging of high clinical value. This work demonstrates the combination of simultaneous multislice (SMS) imaging to accelerate 2D motion robust CSE-MRI acquisitions. Results with computer simulations and in vivo experiments confirm the feasibility of combining these two techniques to achieve rapid, whole-liver, motion robust quantitative tissue characterization.