Matthew Kim¹, Denise Zhong¹, Moss Y Zhao², David Y.T Chen³, David D Shin⁴, Greg Zaharchuk², and Audrey P. Fan^1,5
1Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States, ²Department of Radiology, Stanford University, Stanford, CA, United States, ³Department of Medical Imaging, Taipei Medical University-Shuan-Ho Hospital, New Taipei City, Taiwan, ⁴General Electric Healthcare, San Ramon, CA, United States, ⁵Department of Neurology, University of California Davis, Davis, CA, United States

We quantified R2’ as a biomarker of brain oxygen extraction fraction (OEF) using a multi-parametric approach, based on multi-echo gradient echo (R2*) and fast spin echo scans (R2). Healthy volunteers received repeat scans after 1-2 weeks and the coefficient of variation of R2’ was low (4.4-8.3% in vascular territories), indicating good R2’ scan-rescan reproducibility. R2’ was also inversely correlated with PET scans of cerebral blood flow in healthy controls, as expected. In 14 Moyamoya patients, elevated R2’ (indicating abnormal, high OEF) was observed both in brain regions with and without artery stenosis, and provided complementary information to cerebral perfusion.

Hampus Olsson¹, Mads Andersen², Mustafa Kadhim¹, and Gunther Helms^1
1Department of Medical Radiation Physics, Clinical Sciences Lund, Lund University, Lund, Sweden, ²Philips Healthcare, Copenhagen, Denmark

MP2RAGE has become popular for T₁ mapping at 7T. Accuracy is yet improved by using a separately acquired flip angle map when creating the protocol-specific lookup table. Here, two additional volumes acquired at differing flip angles are added to an MP2RAGE sequence to obtain two separate states of driven equilibriums, effectively forming a dual flip angle protocol within the cycle. By estimating the accelerated effective relaxation, T₁^*, from the signals, both T₁ and B₁⁺ can be solved for analytically. Thus, a multi-volume MPRAGE sequence is turned into a dedicated high-resolution T₁ and flip angle-mapping protocol.

Rita Schmidt^1,2, Amir Seginer³, and Yael Kierson^1,2
1Neurobiology, Weizmann Institute of Science, Rehovot, Israel, ²The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel, ³Siemens Healthcare Ltd, Rosh Ha’ayin, Israel

There is a bulk of studies exploring spin-echo and multi-echo methods generating T₂ weighted imaging and T₂ mapping. However, the challenges at 7T MRI include high SAR, long scans and RF inhomogeneity. Steady-state GRE also provide T₂ maps based on the magnitude images. A recent study at 3T demonstrated phase-based 3D-GRE with specific RF phase increments producing T₂ maps.  We propose acquiring four scans from which we can estimate both the T₂ and the B₁ maps_.  We denote this method as Steady-state T₂ And Rf Estimation (STARE). STARE offers a new capability to acquire fast 3D dataset for T2 mapping.

Sen Ma¹, Nan Wang¹, Zhaoyang Fan¹, Yibin Xie¹, Debiao Li¹, and Anthony G. Christodoulou^1
1Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States

We introduce a motion-resolved solution to clinical brain MRI for quantitative multiparametric mapping using Multitasking. We demonstrate that the proposed approach is generalizable to translation, rotation, discrete motion, and periodic motion without explicit need for motion correction or compensation. Both simulation and in vivo results show that the proposed motion-resolved approach produces better image quality with sharp tissue structure and without ghosting/blurring artifacts, which outperforms no motion handling and simple motion removal. The motion-resolved approach yields substantially less RMSE in terms of quantitative mapping accuracy compared to no motion handling and simple motion removal.

Fuyixue Wang^1,2, Zijing Dong^1,3, Timothy G. Reese¹, Lawrence L. Wald^1,2, and Kawin Setsompop^4,5
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard-MIT Health Sciences and Technology, MIT, Cambridge, MA, United States, ³Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, ⁴Department of Radiology, Stanford University, Stanford, CA, United States, ⁵Department of Electrical Engineering, Stanford University, Stanford, CA, United States

3D-EPTI is a recent multi-parametric mapping technique capable of rapid T1,T2,and T2* quantification. In this work, we characterize the repeatability of two optimized 3D-EPTI whole-brain protocols at 1-mm and 0.7-mm isotropic resolutions (3- and 9-minutes), suitable for a range of clinical and neuroscientific applications. Scan-rescan across 5 subjects shows low intra- and inter-subject variabilities in the derived quantitative-metrics across 165 brain-regions using automatic FreeSurfer segmentation. High-repeatability of quantitative measures across cortical depths was demonstrated using the 0.7-mm protocol, indicating its potential for robust-and-repeatable cortical myeloarchitecture investigation. Lastly, synthetic 3D-EPTI images were demonstrated to be in high-agreement with clinical contrast-weighted images. 

Rong Guo^1,2, Yibo Zhao^1,2, Yudu Li^1,2, Yao Li³, and Zhi-Pei Liang^1,2
1Department of Electrical and Computer Engineering, 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, ³School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

Both quantitative MR parametric mapping and MRSI take long scan times. SPICE has recently demonstrated a unique capability for simultaneous metabolic imaging and water imaging. Taking advantage of the unsuppressed water signals acquired using SPICE, we extended the SPICE technique with a new feature for fast parametric mapping. With one-minute extra scan time, T₁ and T₂ maps at 1.0×1.0×2.0 mm³ resolution were successfully obtained. This new capability enables simultaneous high-resolution parametric mapping and metabolic imaging of the human brain in a total 8-minute scan.

Jana Hutter¹, Raphael Tomi-Tricot², Jan Sedlacik¹, Philippa Bridgen¹, Shaihan Malik¹, and Joseph V Hajnal^1
1Centre for Medical Engineering, King's College London, London, United Kingdom, ²MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom

A multi-parametric quantitative MRI sequence called ZEBRA, which varies diffusion weighting, inversion time (TI) and gradient echo time (TE) by shuffling flexibly diffusion preparation, slice acquisition order, slice spacing and diffusion properties and by adding multiple gradient echo read-outs sharing one diffusion preparation is explored on a 7T scanner in high resolution.

Laila khedher¹, Jean Marie Bonny², Ana Marques³, Marie Vidailhet⁴, Frédéric Torny⁵, Luc Defebvre⁶, Stéphane Thobois⁷, Elena Moro⁸, Philippe Remy⁹, Christian Geny¹⁰, Wassilios Meissner¹¹, Solène Frismand¹², Anne Doe de Maindreville¹³, Jean-Luc Houeto¹⁴, Olivier Rascol¹⁵, and Franck Durif^1,3
1University Clermont Auvergne, Clermont Ferrand, France, ²INRA, UR370 Qualité des Produits Animaux, Saint Genès Champanelle, France, ³CHU Clermont Ferrand, Clermont Ferrand, France, ⁴Fédération des maladies du système nerveux GH La Pitié Salpêtrière, Paris, France, ⁵CHU Dupuytren, Service de Neurologie, Limoges, France, ⁶Hopital Roger Salengro, Service de Neurologie et Pathologie du Mouvement, Lille, France, ⁷Hopital Pierre Wertheimer, Neurologie C, Lyon, France, ⁸CHU de Grenoble, Service de Neurologie, Grenoble, France, ⁹Hopital Henri Mondor, Service de Neurologie, Creteil, France, ¹⁰CHRU Montpellier, Service de Neurologie, Montpellier, France, ¹¹CHU Bordeaux, Service de Neurologie, Bordeaux, France, ¹²Hopital Central-CHU Nancy, Service de Neurologie, Nancy, France, ¹³Pole Neurologie-Gériatrie, Reims, France, ¹⁴CHU de Poitiers, Poitiers, France, ¹⁵Centre d’Investigation Clinique CIC 1436, CHU PURPAN-Place du Dr Baylac, Hopital Pierre Paul Riquet, Toulouse, France

Several postmortem studies have shown an accumulation of iron in the substantia nigra (SN) in Parkinson’s disease (PD). The iron concentration can be estimated by MRI via the MRI-R2* mapping. 1, 2 In order to assess the changes in R2* occurring in PD patients compared to healthy controls, a multicenter transversal prospective study was carried out in a large cohort of PD patients (n = 98) going from the early to the late stage of the disease and matched controls (n = 66).

Lingceng Ma^1,2, Qingjia Bao¹, Ricardo P. Martinho¹, Zhong Chen², and Lucio Frydman^1
1Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel, ²Department of Electronic Science, Xiamen University, Xiamen, China

Fast T₁ mapping methods based on subspace-constrained reconstructions of jointly sparsed-sample domains, are proposed and shown to efficiently deliver maps with either multiple T₁ contrasts or T₁ values with ≈ 50-100× accelerations. Both single-shot and multi-shot implementations were developed, incorporating random-sampling inversion recovery (IR) as well as variable-TR multi-shot gradient echo (GRE) and spatiotemporally encoded (SPEN) sequences. In vivo human brain scans confirmed the efficiency of this method. Preclinical scans on kidneys and on tumor-implanted animals subject to dynamic contrast-enhanced T₁ mapping, also demonstrate the proposed method's advantages for functional and pathological diagnoses.

Rosa Sanchez Panchuelo¹, Olivier Mougin¹, Robert Turner^1,2, and Susan Francis^1,3
1Sir Peter Mansfield Imaging Centre, UP, University of Nottingham, Nottingham, United Kingdom, ²Max Planck Institute for Human Cognitive and Brain Sciences, Leibzig, Germany, ³NIHR Nottingham Biomedical Research, University of Nottingham, Nottingham, United Kingdom

Multi-slice inversion–recovery EPI (MS-IR-EPI) combined with slice order shifting across multiple acquisitions can provide a fast method for high spatial resolution T₁ mapping. However, magnetization transfer (MT) effects of spectrally-selective fat-suppression pulses used in in-vivo imaging shorten measured T₁-values. Here we model the effect of fat-suppression pulses on measured T₁ and use this model to remove the MT contribution, improving the accuracy of T₁ quantification. MT-corrected high spatial resolution T₁ maps of the human brain generated with MS-IR-EPI at 7T are compared with those generated with the widely implemented MP2RAGE sequence and standard single slice IR-EPI.