Jesse I. Hamilton¹, Anagha Deshmane¹, Stephanie Hougen², Mark Griswold^1,3, and Nicole Seiberlich^1,3
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Physics, Case Western Reserve University, Cleveland, OH, United States, ³Radiology, Case Western Reserve University, Cleveland, OH, United States

A new technique termed MRF-X is introduced that models two-compartment chemical exchange to generate a dictionary for subvoxel mapping of T1, T2, volume fraction, and exchange rate. Simulations indicate that the MRF-X model can map subvoxel parameters in cases where standard mapping sequences would map a single effective T1 or T2 value. MRF-X has the potential to directly measure properties of tissue microstructure.

Martijn A Cloos^1,2, Tiejun Zhao^2,3, Florian Knoll^1,2, Leeor Alon^1,2, Riccardo Lattanzi^1,2, and Daniel K Sodickson^1,2
1Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ²Center for Advanced Imaging Innovation and Research (CAI2R), New York University School of Medicine, New York, NY, United States, ³Siemens Medical Solutions USA Inc., Malvern, PA, United States

Magnetic Resonance Fingerprinting enables rapid multi-parametric mapping. By interweaving multiple transmit-channels into the fingerprinting sequence an elegant parallel transmission framework can be constructed. Forgoing uniform excitations, this generalized MR fingerprinting framework circumvents a pitched battle against the electro-dynamic interactions that cause B1 artifacts in the traditional MR paradigm while maintaining a tractable “plug & play” like workflow. In this work we introduce the concept of “fingerprint compression”, which enables even greater acceleration factors while simultaneously speeding up the reconstruction process. This is of particular importance when using multiple transmit channels.

Dan Ma¹ and Mark Griswold^2
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Radiology, Case Western Reserve University, OH, United States

The MRF-Music sequence is a special form of the MRF method that allows one to generate quantitative MR images with a pleasant sounding acquisition. This study introduces a fast converting method that generates the encoding gradients directly from the music for a 2D MRF-Music sequence in less than 1/5000th of the previous calculation time. The resulting gradients generate similar sound effects to the original music and still maintain high efficiency of quantifying T1, T2 and M0 maps simultaneously.

Dongyeob Han¹, Min-Oh Kim¹, Dosik Hwang¹, and Dong-Hyun Kim^1
1Yonsei University, Seoul, Korea

In body imaging such as knee or liver, fat signal needs to be quantified for applications such as bone marrow diseases or hepatic steatosis. Herein, a fast dual TR bSSFP acquisition method for simultaneous w/f decomposition with T1, T2 quantification is proposed.

Cheng-Chieh Cheng¹, Chang-Sheng Mei², Pelin Aksit Ciris^3,4, Robert V. Mulkern^4,5, Mukund Balasubramanian^4,5, Hsiao-Wen Chung¹, Tzu-Cheng Chao⁶, Lawrence P. Panych^3,4, and Bruno Madore^3,4
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, ²Department of Physics, Soochow University, Taipei, Taiwan, ³Department of Radiology, Brigham and Women's Hospital, Boston, MA, United States, ⁴Harvard Medical School, Boston, MA, United States,⁵Department of Radiology, Boston Children's Hospital, Boston, MA, United States, ⁶Department of Computer Science and Information Engineering, National Cheng-Kung University, Tainan, Taiwan

Both T2 mapping and field mapping can provide rich clinically-relevant information. During thermal therapies for example, field maps provide temperature information through the proton resonance frequency effect while T2 can reveal tissue damage and edema. In brain imaging, field maps reveal iron deposits and bleeding through susceptibility effects while T2 enables tumor detection and segmentation. Typically, pulse sequences based on spin echoes are needed for T2 mapping while gradient echoes are needed for field mapping, making it difficult to simultaneously acquire both types of information. A dual-pathway multi-echo pulse sequence is employed here to generate both T2 and field maps from the same acquired data.

Giang Chau Ngo^1,2 and Bradley P. Sutton^1,2
1Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States

T2* maps are used in many applications from functional brain imaging to targeted contrast agents. However, in-plane magnetic field inhomogeneity leads to a non-exponential decay of the T2* signal. This work proposes a method to estimate T2* by taking into account intra-voxel magnetic gradients. A k-space estimation approach is developed, combined with a single shot multi-echo spiral out trajectory.

Abraam S Soliman^1,2, Lanette J Friesen-Waldner³, Kevin J Sinclair³, Timothy R.H Regnault^4,5, and Charles A McKenzie^1,3
1Biomedical Engineering, University of Western Ontario, London, Ontario, Canada, ²Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada, ³Medical Biophysics, University of Western Ontario, London, Ontario, Canada, ⁴Obstetrics and Gynaecology, University of Western Ontario, London, Ontario, Canada, ⁵Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada

High resolution water and fat imaging is recommended in animal research to depict detailed tissue structures. Current multi-gradient-echo unipolar sequences employ flyback readout gradients, which prolongs the acquisition time. In this work, a recently proposed bipolar acquisition is utilized to achieve double the spatial resolution of the conventional unipolar sequence during the same acquisition time, allowing clear identification of adipose tissue structures without further increase in scan time.

Vanessa Stahl¹, Florian Maier¹, Ralf O. Floca², Moritz C. Berger¹, Mauricio Berriel Diaz³, Martin T. Freitag², Marc-André Weber⁴, Antonia Dimitrakopoulou-Strauss⁵, and Armin M. Nagel^1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, ²Department of Radiology, German Cancer Research Center, Heidelberg, Germany, ³Molecular Metabolic Control, German Cancer Research Center, Heidelberg, Germany, ⁴Diagnostic and Interventional Radiology, University Hospital of Heidelberg, Heidelberg, Germany, ⁵Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center, Heidelberg, Germany

Brown adipose tissue (BAT) is subject of ongoing research because of its ability to dissipate energy through non-shivering thermogenesis giving therapeutic potential for the treatment of obesity and metabolic diseases in humans. The purpose of this work was to evaluate in vivo the acute activation of BAT by induced cooling of the skin using Dixon water-fat-separated MRI. The fat fraction (FF) of BAT was determined over time in five volunteers in a temperature-controlled measurement including 90 minutes of cooling time. Focusing on the two interscapular BAT depots, a mean FF decrease of (-4.0 ± 1.7) % / h was detected and therefore FF changes over time in BAT during cooling could be observed.

Diego Hernando¹, Utaroh Motosugi^1,2, and Scott B. Reeder^1,3
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, ²Radiology, University of Yamanashi, Yamanashi, Japan, ³Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Chemical Shift Encoded (CSE) techniques for fat quantification enable rapid and accurate quantification of proton-density fat-fraction (PDFF), a fundamental biomarker of triglyceride concentration in tissue. However, these techniques suffer from relatively low SNR due to the rapid acquisition with parallel imaging acceleration and the use of very low flip angles. In order to improve the SNR, acquisitions with short echo times (eg: initial TE<1ms) and moderate spatial resolution may be performed. In this work, we show that these acquisitions present elevated signal at short TE, leading to positive bias (1.6%-1.9%) in liver PDFF relative to standard CSE or single-voxel spectroscopy.

Dimitrios C Karampinos¹, Stefan Ruschke¹, Michael Dieckmeyer¹, Holger Eggers², Hendrik Kooijman³, Ernst J Rummeny¹, Jan S Bauer⁴, and Thomas Baum^1
1Diagnostic and Interventional Radiology, Technische Universität München, Munich, Germany, ²Philips Research Laboratory, Hamburg, Germany, ³Philips Healthcare, Hamburg, Germany, ⁴Neuroradiology, Technische Universität München, Munich, Germany

Spine fat fraction mapping is emerging with growing applications in osteoporosis and radiation therapy. Vertebral bone marrow is characterized by short T2* relaxation times. Therefore, vertebral bone marrow fat quantification using chemical shift encoding-based water-fat imaging needs to correct for T2* decay effects. The present study compares different approaches for T2* correction in water-fat imaging of vertebral bone marrow using single-voxel MRS as a reference standard. The advantage of a method correcting for a common T2′ and using a priori known T2 relaxation times for water and fat components is evaluated on the data from 26 young healthy volunteers.