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Jan Petr, Henri J M M Mutsaerts, Enrico De Vita, Rebecca M E Steketee, Marion Smits, Aart J Nederveen, Frank Hofheinz, Jörg van den Hoff, Iris Asllani
OBJECTIVE: Partial volume (PV) correction is an important step in arterial spin labeling (ASL) MRI that is used to separate perfusion from structural effects when computing the mean gray matter (GM) perfusion. There are three main methods for performing this correction: (1) GM-threshold, which includes only voxels with GM volume above a preset threshold; (2) GM-weighted, which uses voxel-wise GM contribution combined with thresholding; and (3) PVC, which applies a spatial linear regression algorithm to estimate the flow contribution of each tissue at a given voxel...
June 18, 2018: Magma
Bu S Park, Ge Ma, William T Koch, Sunder S Rajan, Manuel Mastromanolis, Johnny Lam, Kyung Sung, Brent McCright
OBJECTIVE: Improve 19 F magnetic resonance imaging uniformity of perfluorocarbon (PFC)-labeled cells by using a secondary inductive resonator tuned to 287 MHz to enhance the induced radio frequency (RF) magnetic field (B1 ) at 7.05 T. MATERIALS AND METHODS: Following Faraday's induction law, the sign of induced B1 made by the secondary resonator can be changed depending on the tuning of the resonator. A secondary resonator located on the opposite side of the phantom of the 19 F surface coil can be shown to enhance or subtract the induced B1 field, depending upon its tuning...
June 15, 2018: Magma
Yuhong Peng, Chao Zou, Yangzi Qiao, Changjun Tie, Qian Wan, Rui Jiang, Chuanli Cheng, Dong Liang, Hairong Zheng, Faqi Li, Xin Liu
PURPOSE: Real-time monitoring is important for the safety and effectiveness of high-intensity focused ultrasound (HIFU) therapy. Magnetic resonance imaging is the preferred imaging modality for HIFU monitoring, with its unique capability of temperature imaging. For real-time temperature imaging, higher temporal resolution and larger spatial coverage are needed. In this study, a sequence based on the echo-shifted RF-spoiled gradient echo (GRE) with simultaneous multi-slice (SMS) imaging was designed for fast temperature imaging...
June 14, 2018: Magma
Sheryl L Herrera, Morgan E Mercredi, Richard Buist, Melanie Martin
OBJECT: Most early methods to infer axon diameter distributions using magnetic resonance imaging (MRI) used single diffusion encoding sequences such as pulsed gradient spin echo (SE) and are thus sensitive to axons of diameters > 5 μm. We previously simulated oscillating gradient (OG) SE sequences for diffusion spectroscopy to study smaller axons including the majority constituting cortical connections. That study suggested the model of constant extra-axonal diffusion breaks down at OG accessible frequencies...
June 4, 2018: Magma
Peter E Yoo, Jon O Cleary, Scott C Kolbe, Roger J Ordidge, Terence J O'Brien, Nicholas L Opie, Sam E John, Thomas J Oxley, Bradford A Moffat
OBJECTIVE: Ultra-high-field functional MRI (UHF-fMRI) allows for higher spatiotemporal resolution imaging. However, higher-resolution imaging entails coverage limitations. Processing partial-coverage images using standard pipelines leads to sub-optimal results. We aimed to develop a simple, semi-automated pipeline for processing partial-coverage UHF-fMRI data using widely used image processing algorithms. MATERIALS AND METHODS: We developed automated pipelines for optimized skull stripping and co-registration of partial-coverage UHF functional images, using built-in functions of the Centre for Functional Magnetic Resonance Imaging of the Brain's (FMRIB's) Software library (FSL) and advanced normalization tools...
May 29, 2018: Magma
Roel L F van der Palen, Arno A W Roest, Pieter J van den Boogaard, Albert de Roos, Nico A Blom, Jos J M Westenberg
OBJECTIVE: The aim was to investigate scan-rescan reproducibility and observer variability of segmental aortic 3D systolic wall shear stress (WSS) by phase-specific segmentation with 4D flow MRI in healthy volunteers. MATERIALS AND METHODS: Ten healthy volunteers (age 26.5 ± 2.6 years) underwent aortic 4D flow MRI twice. Maximum 3D systolic WSS (WSSmax) and mean 3D systolic WSS (WSSmean) for five thoracic aortic segments over five systolic cardiac phases by phase-specific segmentations were calculated...
May 26, 2018: Magma
E E Sigmund, S H Baete, K Patel, D Wang, D Stoffel, R Otazo, P Parasoglou, J Bencardino
OBJECTIVES: We describe measurement of skeletal muscle kinetics with multiple echo diffusion tensor imaging (MEDITI). This approach allows characterization of the microstructural dynamics in healthy and pathologic muscle. MATERIALS AND METHODS: In a Siemens 3-T Skyra scanner, MEDITI was used to collect dynamic DTI with a combination of rapid diffusion encoding, radial imaging, and compressed sensing reconstruction in a multi-compartment agarose gel rotation phantom and within in vivo calf muscle...
May 14, 2018: Magma
Anja Müller-Lutz, Alexandra Ljimani, Julia Stabinska, Moritz Zaiss, Johannes Boos, Hans-Jörg Wittsack, Christoph Schleich
PURPOSE: The study compares glycosaminoglycan chemical exchange saturation transfer (gagCEST) imaging of intervertebral discs corrected for solely B0 inhomogeneities or both B0 and B1 inhomogeneities. METHODS: Lumbar intervertebral discs of 20 volunteers were examined with T2 -weighted and gagCEST imaging. Field inhomogeneity correction was performed with B0 correction only and with correction of both B0 and B1 . GagCEST effects measured by the asymmetric magnetization transfer ratio (MTRasym ) and signal-to-noise ratio (SNR) were compared between both methods...
May 14, 2018: Magma
Kannika Khantasup, Pairash Saiviroonporn, Suwatchai Jarussophon, Warangkana Chantima, Tararaj Dharakul
OBJECTIVES: The development of targeted contrast agents for magnetic resonance imaging (MRI) facilitates enhanced cancer imaging and more accurate diagnosis. In the present study, a novel contrast agent was developed by conjugating anti-EpCAM humanized scFv with gadolinium chelate to achieve target specificity. MATERIALS AND METHODS: The material design strategy involved site-specific conjugation of the chelating agent to scFv. The scFv monomer was linked to maleimide-DTPA via unpaired cysteine at the scFv C-terminus, followed by chelation with gadolinium (Gd)...
May 8, 2018: Magma
Felix Lugauer, Jens Wetzl, Christoph Forman, Manuel Schneider, Berthold Kiefer, Joachim Hornegger, Dominik Nickel, Andreas Maier
OBJECTIVE: Our aim was to develop and validate a 3D Cartesian Look-Locker [Formula: see text] mapping technique that achieves high accuracy and whole-liver coverage within a single breath-hold. MATERIALS AND METHODS: The proposed method combines sparse Cartesian sampling based on a spatiotemporally incoherent Poisson pattern and k-space segmentation, dedicated for high-temporal-resolution imaging. This combination allows capturing tissue with short relaxation times with volumetric coverage...
June 2018: Magma
Gwenaël Pagé, Jérémie Bettoni, Anne-Virginie Salsac, Olivier Balédent
OBJECTIVE: The objective of the study was to determine how to optimize 2D and 4D phase-contrast magnetic resonance imaging (PC-MRI) acquisitions to acquire flow velocities in millimetric vessels. In particular, we search for the best compromise between acquisition time and accuracy and assess the influence of the principal component analysis (PCA). MATERIALS AND METHODS: 2D and 4D PC-MRI measurements are conducted within two in vitro vessel phantoms: a Y-bifurcation phantom, the branches of which range from 2 to 5 mm in diameter, and a physiological subject-specific phantom of the carotid bifurcation...
June 2018: Magma
Rita G Nunes, Joseph V Hajnal
OBJECTIVE: Point spread function (PSF) mapping enables estimating the displacement fields required for distortion correction of echo planar images. Recently, a highly accelerated approach was introduced for estimating displacements from the phase slope of under-sampled PSF mapping data. Sampling schemes with varying spacing were proposed requiring stepwise phase unwrapping. To avoid unwrapping errors, an alternative approach applying the concept of finite rate of innovation to PSF mapping (FRIP) is introduced, using a pattern search strategy to locate the PSF peak, and the two methods are compared...
June 2018: Magma
Xin Zhang, Xiangyang Zhu, Christopher Martyn Ferguson, Kai Jiang, Tyson Burningham, Amir Lerman, Lilach Orly Lerman
OBJECTIVE: Low-energy shockwave (SW) therapy attenuates damage in the stenotic kidney (STK) caused by atherosclerotic renal artery stenosis (ARAS). We hypothesized that magnetic resonance elastography (MRE) would detect attenuation of fibrosis following SW in unilateral ARAS kidneys. MATERIALS AND METHODS: Domestic pigs were randomized to control, unilateral ARAS, and ARAS treated with 6 sessions of SW over 3 consecutive weeks (n = 7 each) starting after 3 weeks of ARAS or sham...
June 2018: Magma
Elias Kellner, Irina Mader, Marco Reisert, Horst Urbach, Valerij Gennadevic Kiselev
OBJECT: We aimed to modify our previously published method for arterial input function measurements for evaluation of cerebral perfusion (dynamic susceptibility contrast MRI) such that it can be applied in humans in a clinical setting. MATERIALS AND METHODS: Similarly to our previous work, a conventional measurement sequence for dynamic susceptibility contrast MRI is extended with an additional measurement slice at the neck. Measurement parameters at this slice were optimized for the blood signal (short echo time, background suppression, magnitude and phase images)...
June 2018: Magma
Chengcheng Zhu, Bing Tian, Luguang Chen, Laura Eisenmenger, Esther Raithel, Christoph Forman, Sinyeob Ahn, Gerhard Laub, Qi Liu, Jianping Lu, Jing Liu, Christopher Hess, David Saloner
OBJECTIVE: Develop and optimize an accelerated, high-resolution (0.5 mm isotropic) 3D black blood MRI technique to reduce scan time for whole-brain intracranial vessel wall imaging. MATERIALS AND METHODS: A 3D accelerated T1 -weighted fast-spin-echo prototype sequence using compressed sensing (CS-SPACE) was developed at 3T. Both the acquisition [echo train length (ETL), under-sampling factor] and reconstruction parameters (regularization parameter, number of iterations) were first optimized in 5 healthy volunteers...
June 2018: Magma
Oliver Gloger, Robin Bülow, Klaus Tönnies, Henry Völzke
OBJECTIVES: We aimed to develop the first fully automated 3D gallbladder segmentation approach to perform volumetric analysis in volume data of magnetic resonance (MR) cholangiopancreatography (MRCP) sequences. Volumetric gallbladder analysis is performed for non-contrast-enhanced and secretin-enhanced MRCP sequences. MATERIALS AND METHODS: Native and secretin-enhanced MRCP volume data were produced with a 1.5-T MR system. Images of coronal maximum intensity projections (MIP) are used to automatically compute 2D characteristic shape features of the gallbladder in the MIP images...
June 2018: Magma
Peter T While, Jose R Teruel, Igor Vidić, Tone F Bathen, Pål Erik Goa
OBJECTIVE: To explore the relationship between relative enhanced diffusivity (RED) and intravoxel incoherent motion (IVIM), as well as the impact of noise and the choice of intermediate diffusion weighting (b value) on the RED parameter. MATERIALS AND METHODS: A mathematical derivation was performed to cast RED in terms of the IVIM parameters. Noise analysis and b value optimization was conducted by using Monte Carlo calculations to generate diffusion-weighted imaging data appropriate to breast and liver tissue at three different signal-to-noise ratios...
June 2018: Magma
Manushka V Vaidya, Cem M Deniz, Christopher M Collins, Daniel K Sodickson, Riccardo Lattanzi
OBJECTIVE: To use high-permittivity materials (HPM) positioned near radiofrequency (RF) surface coils to manipulate transmit/receive field patterns. MATERIALS AND METHODS: A large HPM pad was placed below the RF coil to extend the field of view (FOV). The resulting signal-to-noise ratio (SNR) was compared with that of other coil configurations covering the same FOV in simulations and experiments at 7 T. Transmit/receive efficiency was evaluated when HPM discs with or without a partial shield were positioned at a distance from the coil...
June 2018: Magma
Jolanda M Spijkerman, Esben T Petersen, Jeroen Hendrikse, Peter Luijten, Jaco J M Zwanenburg
OBJECT: Cerebrospinal fluid (CSF) T 2 mapping can potentially be used to investigate CSF composition. A previously proposed CSF T 2 -mapping method reported a T 2 difference between peripheral and ventricular CSF, and suggested that this reflected different CSF compositions. We studied the performance of this method at 7 T and evaluated the influence of partial volume and B 1 and B 0 inhomogeneity. MATERIALS AND METHODS: T 2 -preparation-based CSF T 2 -mapping was performed in seven healthy volunteers at 7 and 3 T, and was compared with a single echo spin-echo sequence with various echo times...
June 2018: Magma
Florian Siedek, Thorsten Persigehl, Roman-Ulrich Mueller, Volker Burst, Thomas Benzing, David Maintz, Stefan Haneder
OBJECTIVE: Acute kidney injury (AKI) is an important risk factor for a number of adverse outcomes including end-stage renal disease and cardiovascular morbidity and mortality. Whilst many clinical situations that can induce AKI are known-e.g. drug toxicity, contrast agent exposure or ischemia during surgery-targeted preventive or therapeutic measures are still lacking. As to renoprotective strategies, remote ischemic preconditioning (RIPC) is one of the most promising novel approaches and has been examined by a number of clinical trials...
June 2018: Magma
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