Soudabeh Kargar¹, Daiki Tamada¹, Ruvini Navaratna¹, Jayse Merle Weaver¹, and Scott B Reeder^1
1Radiology, University of Wisconsin - Madison, Madison, WI, United States

Heavily T2-weighted imaging is used for a variety of fluid sensitive imaging such as MRCP. However, these fast spin-echo-based methods suffer from long acquisition duration. In this work we apply a novel strategy using RF phase modulated gradient echo (GRE) with small RF phase increments to encode T2 information into the phase of the signal. In this work, we optimize this strategy for long T2 species to achieve heavily T2-weighted imaging, including the introduction of a novel cross-product strategy to highlight signal in tissues with long T2 and suppress signal in tissues with shorter T2 values.

Dana C. Peters¹, Stefan Markovic², Qingjia Bao², Dina Preise², Keren Sasson², Lilach Agemy², Avigdor Scherz², and Lucio Frydman^2
1Radiology and Biomed Eng., Yale University, New Haven, CT, United States, ²Weizmann Institute of Science, Rehovot, Israel

Deuterium metabolic imaging (DMI) maps the individual in vivo fate of ²H-enriched metabolites. Upon injecting ²H6,6’-glucose, DMI images a ²H-water peak, and a small but diagnostic ²H3,3’-lactate signature, highlighting tumors and their aberrant metabolism.  DMI faces major sensitivity challenges, that can be alleviated by a multi-echo balanced SSFP approach. When suitably tuned, multi-echo bSSFP yields good spectral isolation of all metabolites, and thanks to the relatively large T₂/T₁ ratios of deuterated compounds, several-fold increases in SNR vs. chemical shift imaging are then obtained.   This is demonstrated in phantoms, and in in vivo mice studies of orthotopic pancreatic tumors. 

Yang Zhou¹, Peter van Zijl^2,3, Chongxue Bie^2,3,4, Jiadi Xu^2,3, Xin Liu¹, and Nirbhay N. Yadav^2,3
1Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Shenzhen, China, ²The Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ³F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ⁴Department of Information Science and Technology, Northwest University, Xian, China

Saturation transfer MRI has previously been applied to study transient molecular binding using the IMMOBILISE MRI approach, yet the multiple mechanisms of magnetization transfer during such binding are still under investigation. We studied electrostatic-interaction-mediated molecular binding of small substrates (choline and arginine) to ion-exchange column media. A theoretical model using relayed NOEs to exchangeable protons in the bound substrate is proposed to quantitatively describe the saturation transfer during such binding. 

Dahua Cui¹, Ailian Liu¹, Hongkai Wang², Mingrui Zhuang², and Qingwei Song^1
1The First Affiliated Hospital of Dalian Medical University, Dalian, China, ²Dalian University of Technology, Dalian, China

The aim of this study was to investigate the feasibility of intratumoral susceptibility signal intensities (ITSS) combined with R2* values obtained from T2 star-weighted angiography (ESWAN) in quantitatively and automatically evaluating histological grading of hepatocellular carcinoma (HCC). The results showed that the combination of quantitative ITSS and R2* was feasible to evaluate the histological grading of HCC performance (AUC = 0.856, P < 0.0001, sensitivity of 88.89%, specificity of 69.44%) automatically. 

Tianxiao Zhang¹, Rong Guo^2,3, Yudu Li^2,3, Yibo Zhao^2,3, Zhi-Pei Liang^2,3, and Yao Li^1
1School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ²Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Simultaneous MRSI and T₂* mapping has been demonstrated recently using SPICE. With a T₂ map, T₂' values could be calculated, which reflects tissue oxygenation. However, the accuracy of T₂* and T₂ measurements suffers from system imperfections. In this work, we improved T₂' mapping by overcoming signal dephasing in T₂* mapping and estimation bias in T₂ mapping. The signal dephasing in T₂* caused by B₀ inhomogeneity was corrected utilizing high-resolution field map and pre-learned subspaces, and the estimation bias in T₂ caused by B₁⁺ inhomogeneity was corrected with a dictionary-based estimation. The proposed method provided improved T₂' mapping in SPICE experiments.

Sophie Queler¹, Ek Tsoon Tan¹, Martin Prince², John Carrino¹, and Darryl Sneag^1
1Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States, ²Weill Cornell Medicine, New York, NY, United States

In this study, we investigated the use of ferumoxytol, an iron-oxide nanoparticle, for vascular signal suppression in 3 Tesla magnetic resonance neurography of the brachial plexus. A 3D, T2-weighted STIR sequence was prospectively acquired of 19 normal brachial plexi in 10 volunteers (1 unilateral; 9 bilateral) before and after ferumoxytol infusion. Independent assessment of anonymized exams by two radiologists demonstrated overall improved vascular suppression as well as improved visualization of the suprascapular nerve with increased diagnostic confidence. Improvements in nerve-, fat-, and blood-to-muscle contrast were supported by signal simulations.

Christof Boehm¹, Marianne Goeger-Neff², Hendrik T. Mulder³, Benjamin Zilles², Lars H. Lindner², Gerard C. van Rhoon³, Dimitrios C. Karampinos⁴, and Mingming Wu^1
1Technical University of Munich, Munich, Germany, ²Department of Medicine III, University Hospital, LMU Munich, Munich, Germany, ³Erasmus MC Cancer Institute, Rotterdam, Netherlands, ⁴Department of Diagnostic and Interventional Radiology, School of Medicine, Technical University of Munich, Munich, Germany

Motion-induced susceptibility changes induce field variations, leading to large errors during MR thermometry based on the linear proton resonance frequency shift. These artefacts aggravate temperature quantification in the face of both the long treatment duration and the mild temperature change during mild RF hyperthermia treatments. We show with the help of simulations, a phantom heating experiment, volunteer scans and mild hyperthermia treatment of a patient with cervical cancer and a sarcoma patient how to correct for this artefact source by methods known from quantitative susceptibility mapping. The recently introduced total field inversion shows advantages over the background field removal methods.

Zhehong Zhang¹, Fair Merlin², Fuyixue Wang^3,4, Zijing Dong^3,5, Wending Tang¹, Menghan Li¹, Danna Wei⁶, Kawin Setsompop^2,7, and Kui Ying^1
1Department of Engineering Physics, Tsinghua University, Beijing, China, ²Department of Radiology, School of Medicine, Stanford University, Stanford, CA, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ⁴Harvard-MIT Health Sciences and Technology, MIT, Cambridge, MA, United States, ⁵Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, ⁶Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, ⁷Department of Electrical Engineering, Stanford University, Stanford, CA, United States

Echo‐planar time‐resolved imaging (EPTI) is a multi-shot EPI technique capable of rapidly obtaining distortion‐free and blurring‐free time-resolved multi-contrast images across the EPI readout. PROPELLER is an extension to EPTI, which incorporates PROPRELLER-like acquisition, to enable shot-to-shot motion toleration. In this work, PEPTIDE was applied to the MR thermometry application, where an image reconstruction framework that leveraged sparsity across blades of PEPTIDE rawdata was proposed. The potential in using PEPTIDE to provide distortion- and blurring-free temperature mapping at high temporal resolution was then demonstrated via simulated human brain PEPTIDE data with various temperature profiles.

Kisoo Kim¹, Chris Diederich², and Eugene Ozhinsky^1
1Department of Radiology & Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA, United States

MR temperature monitoring during ultrasound thermal therapy of abdominal organs is challenging due to respiratory motion. It is especially important for hyperthermia therapy, which requires accurate temperature measurements to ensure therapeutic heating within a narrow temperature window (37-45 °C). In this study we developed a motion-robust, multi-slice, real-time MR thermometry sequence and reconstruction pipeline for the monitoring of temperature in hyperthermia or thermal ablation therapy in abdominal organs. This technique was implemented in RTHawk and evaluated in simulated acquisitions, phantom experiments with a custom-made motion phantom, and in-vivo healthy volunteer experiment without heating.

Alexey Samsonov^1
1University of Wisconsin-Madison, Madison, WI, United States

Macromolecular proton fraction (MPF) is an established myelin marker with confirmed clinical relevance, but with sensitivity to technological variations such as B1 field errors.  We propose a method to derive B1 map for MPF correction from MPF data itself. The method is based on standard two-pool MT formalism enhanced with improved relaxometry constraints.