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Ralf Lützkendorf, Robin M Heidemann, Thorsten Feiweier, Michael Luchtmann, Sebastian Baecke, Jörn Kaufmann, Jörg Stadler, Eike Budinger, Johannes Bernarding
OBJECTIVES: We assessed the use of high-resolution ultra-high-field diffusion magnetic resonance imaging (dMRI) to determine neuronal fiber orientation density functions (fODFs) throughout the human brain, including gray matter (GM), white matter (WM), and small intertwined structures in the cerebellopontine region. MATERIALS AND METHODS: We acquired 7-T whole-brain dMRI data of 23 volunteers with 1.4-mm isotropic resolution; fODFs were estimated using constrained spherical deconvolution...
September 17, 2018: Magma
Céline Marie Desmet, Ly Binh An Tran, Pierre Danhier, Bernard Gallez
OBJECTIVES: Electron paramagnetic resonance (EPR) oximetry using particulate materials allows repeatable measurements of oxygen in tissues. However, the materials identified so far are not medical devices, thus precluding their immediate use in clinical studies. The aim of this study was to assess the magnetic properties of Carbo-Rep® , a charcoal suspension used as a liquid marker for preoperative tumor localization. MATERIALS AND METHODS: Calibration curves (EPR linewidth as a function of pO2 ) were built using 9-GHz EPR spectrometry...
September 12, 2018: Magma
Giovanna Nordio, Aurélien Bustin, Markus Henningsson, Imran Rashid, Amedeo Chiribiri, Tevfik Ismail, Freddy Odille, Claudia Prieto, René Michael Botnar
PURPOSE: To improve the precision of a free-breathing 3D saturation-recovery-based myocardial T1 mapping sequence using a post-processing 3D denoising technique. METHODS: A T1 phantom and 15 healthy subjects were scanned on a 1.5 T MRI scanner using 3D saturation-recovery single-shot acquisition (SASHA) for myocardial T1 mapping. A 3D denoising technique was applied to the native T1-weighted images before pixel-wise T1 fitting. The denoising technique imposes edge-preserving regularity and exploits the co-occurrence of 3D spatial gradients in the native T1-weighted images by incorporating a multi-contrast Beltrami regularization...
September 6, 2018: Magma
Andreas Reichert, Michael Bock, Simon Reiss, Christiaan G Overduin, Jurgen J Fütterer, Axel Joachim Krafft
OBJECTIVE: To accelerate a passive tracking sequence based on phase-only cross correlation (POCC) using simultaneous slice excitation. METHODS: For magnetic resonance (MR)-guided biopsy procedures, passive markers have been proposed that can be automatically localized online using a POCC-based tracking sequence. To accelerate the sequence, a phase-offset multiplanar (POMP) excitation technique was implemented to acquire tracking images. In a phantom experiment, the POMP-POCC sequence was tested and compared with the sequential non-accelerated version in terms of duration and accuracy...
September 6, 2018: Magma
Da Xie, Lauren E Ohman, Emily L Que
OBJECTIVES: Our aim was to demonstrate the potential of exploiting simultaneous changes in coordination geometry and spin state in fluorinated Ni(II) complexes as an avenue for 19 F magnetic-resonance (MR)-based pH sensing. MATERIALS AND METHODS: Crystal structures were studied using an Agilent Technologies SuperNova Dual Source diffractometer. Solution magnetic moment was determined using Evan's method. MR images were collected on a 7.0-T MR scanner equipped with a quadrature 19 F volume coil...
September 3, 2018: Magma
Raluca G Chelu, Michael Horowitz, Dominica Sucha, Isabella Kardys, Delphine Ingremeau, Shreyas Vasanawala, Koen Nieman, Jean-Francois Paul, Albert Hsiao
PURPOSE: With the hypothesis that 4D flow can be used in evaluation of cardiac shunts, we seek to evaluate the multilevel and interreader reproducibility of measurements of the blood flow, shunt fraction and shunt volume in patients with atrial septum defect (ASD) in practice at multiple clinical sites. MATERIALS AND METHODS: Four-dimensional flow MRI examinations were performed at four institutions across Europe and the US. Twenty-nine patients (mean age, 43 years; 11 male) were included in the study...
August 31, 2018: Magma
Conor J MacDonald, Stephen Gandy, Eilidh C M Avison, Shona Matthew, Rose Ross, John G Houston
OBJECTIVE: To compare non-contrast enhanced MRI with ultrasound (US) for measurement of arm blood vessel geometries and flow velocities in volunteers and patients with end-stage renal disease. MATERIALS AND METHODS: Subjects were scanned using US (reference standard), and MRI 2D time-of-flight (ToF), 2D phase contrast (PC), and 3D multi-echo data image combination (MEDIC). Patients were also scanned after arteriovenous fistula (AVF) surgery. RESULTS: For mean vessel diameters (radial and brachial arteries; cephalic vein) MEDIC measurements were similar to US (p > 0...
August 21, 2018: Magma
Juha I Peltonen, Teemu Mäkelä, Eero Salli
OBJECTIVE: Quality assurance (QA) of magnetic resonance imaging (MRI) often relies on imaging phantoms with suitable structures and uniform regions. However, the connection between phantom measurements and actual clinical image quality is ambiguous. Thus, it is desirable to measure objective image quality directly from clinical images. MATERIALS AND METHODS: In this work, four measurements suitable for clinical image QA were presented: image resolution, contrast-to-noise ratio, quality index and bias index...
August 17, 2018: Magma
Oscar Jalnefjord, Mats Andersson, Mikael Montelius, Göran Starck, Anna-Karin Elf, Viktor Johanson, Johanna Svensson, Maria Ljungberg
OBJECTIVE: Intravoxel incoherent motion (IVIM) shows great potential in many applications, e.g., tumor tissue characterization. To reduce image-quality demands, various IVIM analysis approaches restricted to the diffusion coefficient (D) and the perfusion fraction (f) are increasingly being employed. In this work, the impact of estimation approach for D and f is studied. MATERIALS AND METHODS: Four approaches for estimating D and f were studied: segmented IVIM fitting, least-squares fitting of a simplified IVIM model (sIVIM), and Bayesian fitting of the sIVIM model using marginal posterior modes or posterior means...
August 16, 2018: Magma
Ina Vernikouskaya, Alexander Pochert, Mika Lindén, Volker Rasche
OBJECTIVES: A common limitation of all 1 H contrast agents is that they only allow indirect visualization through modification of the intrinsic properties of the tissue, making quantification of this effect challenging. 19 F compounds, on the contrary, are measured directly, without any background signal. There is a linear relationship between the amount of 19 F spins and the intensity of the signal. However, non-uniformity of the radiofrequency field may lead to errors in the quantified 19 F signal and should be carefully addressed for any quantitative imaging...
August 10, 2018: Magma
Maria Filomena Santarelli, Antonella Meloni, Daniele De Marchi, Laura Pistoia, Antonella Quarta, Anna Spasiano, Luigi Landini, Alessia Pepe, Vincenzo Positano
OBJECTIVES: To propose a method for estimating pancreatic relaxation rate, R2*, from conventional multi-echo MRI, based on the nonlinear fitting of the acquired magnitude signal decay to MR signal models that take into account both the signal oscillations induced by fat and the different R2* values of pancreatic parenchyma and fat. MATERIALS AND METHODS: Single-peak fat (SPF) and multi-peak fat (MPF) models were introduced. Single-R2* and dual-R2* assumptions were considered as well...
July 24, 2018: Magma
Ziwu Zhou, Fei Han, Takegawa Yoshida, Kim-Lien Nguyen, John Paul Finn, Peng Hu
OBJECTIVE: Our aim was to develop and evaluate a motion-weighted reconstruction technique for improved cardiac function assessment in 4D magnetic resonance imaging (MRI). MATERIALS AND METHODS: A flat-topped, two-sided Gaussian kernel was used to weigh k-space data in each target cardiac phase and adjacent two temporal phases during the proposed phase-by-phase reconstruction algorithm. The proposed method (Strategy 3) was used to reconstruct 18 cardiac phases based on data acquired using a previously proposed technique [4D multiphase steady-state imaging with contrast enhancement (MUSIC) technique and its self-gated extension using rotating Cartesian k-space (ROCK-MUSIC) from 12 pediatric patients...
July 24, 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...
October 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...
October 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...
October 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)...
October 2018: Magma
Johnes Obungoloch, Joshua R Harper, Steven Consevage, Igor M Savukov, Thomas Neuberger, Srinivas Tadigadapa, Steven J Schiff
OBJECTIVES: The need for affordable and appropriate medical technologies for developing countries continues to rise as challenges such as inadequate energy supply, limited technical expertise, and poor infrastructure persist. Low-field magnetic resonance imaging (LF MRI) is a technology that can be tailored to meet specific imaging needs within such countries. Its low power requirements and the possibility of operating in minimally shielded or unshielded environments make it especially attractive...
October 2018: Magma
Manoj Shrestha, Pavel Hok, Ulrike Nöth, Bianca Lienerth, Ralf Deichmann
OBJECTIVE: The purpose of this work was to optimize the acquisition of diffusion-weighted (DW) single-refocused spin-echo (srSE) data without intrinsic eddy-current compensation (ECC) for an improved performance of ECC postprocessing. The rationale is that srSE sequences without ECC may yield shorter echo times (TE) and thus higher signal-to-noise ratios (SNR) than srSE or twice-refocused spin-echo (trSE) schemes with intrinsic ECC. MATERIALS AND METHODS: The proposed method employs dummy scans with DW gradients to drive eddy currents into a steady state before data acquisition...
October 2018: Magma
Thérèse Barbier, Sarra Aissani, Nicolas Weber, Cédric Pasquier, Jacques Felblinger
PURPOSE: To evaluate the function of an active implantable medical device (AIMD) during magnetic resonance imaging (MRI) scans. The induced voltages caused by the switching of magnetic field gradients and rectified radio frequency (RF) pulse were measured, along with the AIMD stimulations. MATERIALS AND METHODS: An MRI-compatible voltage probe with a bandwidth of 0-40 kHz was designed. Measurements were carried out both on the bench with an overvoltage protection circuit commonly used for AIMD and with a pacemaker during MRI scans on a 1...
October 2018: Magma
Nobuyuki Kosaka, Yasuhiro Fujiwara, Tetsuji Kurokawa, Tsuyoshi Matsuda, Masayuki Kanamoto, Naoyuki Takei, Kenji Takata, Jin Takahashi, Yoshio Yoshida, Hirohiko Kimura
OBJECTIVES: We evaluated the vascularity of retained products of conception (RPOC) using arterial spin-labeling magnetic resonance imaging (ASL-MRI) to clarify the clinical feasibility of this approach. MATERIALS AND METHODS: A pulsed-continuous ASL sequence with echo-planar imaging (EPI) acquisitions was used. Ten consecutive patients with RPOC were enrolled. All ASL images were evaluated visually and semiquantitatively and compared with the findings of Doppler ultrasound (US) and dynamic contrast-enhanced MRI (DCE-MRI)...
August 2018: Magma
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