Philipp Amrein, Fleming Bruckmaier, Feng Jia, Dominik B Bucher, Maxim Zaitsev, Sebastian Littin
INTRODUCTION: Diffusion weighting in optically detected magnetic resonance experiments involving diamond nitrogen-vacancy (NV) centers can provide valuable microstructural information. Bi-planar gradient coils employed for diffusion weighting afford excellent spatial access, essential for integrating the NV-NMR components. Nevertheless, owing to the polar tilt of roughly [Formula: see text] of the diamond NV center, the primary magnetic field direction must be taken into account accordingly...
August 14, 2023: Magma
Bu S Park, Joshua W Guag, Hongbae Jeong, Sunder S Rajan, Brent McCright
OBJECTIVE: To enhance RF safety when implantable medical devices are located within the body coil but outside the imaging region by using a secondary resonator (SR) to reduce electric fields, the corresponding specific absorption rate (SAR), and temperature change during MRI. MATERIALS AND METHODS: This study was conducted using numerical simulations with an American Society for Testing and Materials (ASTM) phantom and adult human models of Ella and Duke from Virtual Family Models, along with corresponding experimental results of temperature change obtained using the ASTM phantom...
August 11, 2023: Magma
Fatemeh Arzanforoosh, Avery J L Berman, Marion Smits, Esther A H Warnert
OBJECTIVE: Monitoring brain oxygenation is critical in brain tumors, as low oxygenation influences tumor growth, pathological angiogenesis, and treatment resistance. This study examined the ability of the streamlined quantitative (sq)BOLD MRI technique to detect oxygenation changes in healthy individuals, as well as its potential application in a clinical setting. METHODS: We used the asymmetric spin echo (ASE) technique with FLAIR preparation, along with model-based Bayesian inference to quantify the reversible transverse relaxation rate (R2 ' ) and oxygen extraction fraction (OEF) across the brain at baseline and during visual stimulation in eight healthy participants at 3T; and two patients with glioma at rest only...
August 9, 2023: Magma
Dyah Ekashanti Octorina Dewi, Mohammed R S Sunoqrot, Gabriel Addio Nketiah, Elise Sandsmark, Guro F Giskeødegård, Sverre Langørgen, Helena Bertilsson, Mattijs Elschot, Tone Frost Bathen
PURPOSE: To evaluate the reproducibility of radiomics features derived via different pre-processing settings from paired T2-weighted imaging (T2WI) prostate lesions acquired within a short interval, to select the setting that yields the highest number of reproducible features, and to evaluate the impact of disease characteristics (i.e., clinical variables) on features reproducibility. MATERIALS AND METHODS: A dataset of 50 patients imaged using T2WI at 2 consecutive examinations was used...
August 9, 2023: Magma
Najat Salameh, David J Lurie, Özlem Ipek, Clarissa Zimmerman Cooley, Adrienne E Campbell-Washburn
No abstract text is available yet for this article.
July 24, 2023: Magma
Mathias Schillmaier, Athanasia Kaika, Geoffrey J Topping, Rickmer Braren, Franz Schilling
OBJECTIVES: Development of a protocol for validation and quality assurance of filter-exchange imaging (FEXI) pulse sequences with well-defined and reproducible phantoms. MATERIALS AND METHODS: A FEXI pulse sequence was implemented on a 7 T preclinical MRI scanner. Six experiments in three different test categories were established for sequence validation, demonstration of the reproducibility of phantoms and the measurement of induced changes in the apparent exchange rate (AXR)...
July 12, 2023: Magma
Rita Castro, Sean Gullette, Courtney Whalen, Floyd J Mattie, Ximing Ge, A Catharine Ross, Thomas Neuberger
OBJECTIVES: Pre-clinical models of human atherosclerosis are extensively used; however, traditional histological methods do not allow for a holistic view of vascular lesions. We describe an ex-vivo, high-resolution MRI method that allows the 3 dimensional imaging of the vessel for aortic plaque visualization and quantification. MATERIALS AND METHODS: Aortas from apolipoprotein-E-deficient (apoE-/- ) mice fed an atherogenic diet (group 1) or a control diet (group 2) were subjected to 14 T MR imaging using a 3D gradient echo sequence...
July 8, 2023: Magma
Jonathan Arvidsson, Stefanie Eriksson, Edvin Johansson, Kerstin Lagerstrand
OBJECTIVE: Dynamic BOLD MRI with cuff compression, inducing ischemia and post-occlusive hyperemia in skeletal muscle, has been pointed out as a potential diagnostic tool to assess peripheral limb perfusion. The objective was to explore the robustness of this technique and its sensitivity to the occlusion duration. MATERIALS AND METHODS: BOLD images were acquired at 3 T in 14 healthy volunteers. [Formula: see text]-imaging with 5- and 1.5-min occlusions were acquired and several semi-quantitative BOLD parameters were derived from ROI-based [Formula: see text]-time curves...
June 17, 2023: Magma
Rajiv Ramasawmy, John P Mugler, Ahsan Javed, Zhixing Wang, Daniel A Herzka, Craig H Meyer, Adrienne E Campbell-Washburn
OBJECTIVE: Diagnostic-quality neuroimaging methods are vital for widespread clinical adoption of low field MRI. Spiral imaging is an efficient acquisition method that can mitigate the reduced signal-to-noise ratio at lower field strengths. As concomitant field artifacts are worse at lower field, we propose a generalizable quadratic gradient-field nulling as an echo-to-echo compensation and apply it to spiral TSE at 0.55 T. MATERIALS AND METHODS: A spiral in-out TSE acquisition was developed with a compensation for concomitant field variation between spiral interleaves, by adding bipolar gradients around each readout to minimize phase differences at each refocusing pulse...
June 12, 2023: Magma
Aurélien Maillot, Soumaya Sridi, Xavier Pineau, Amandine André-Billeau, Stéphanie Hosteins, Jean-David Maes, Géraldine Montier, Marta Nuñez-Garcia, Bruno Quesson, Maxime Sermesant, Hubert Cochet, Matthias Stuber, Aurélien Bustin
OBJECTIVE: To simplify black-blood late gadolinium enhancement (BL-LGE) cardiac imaging in clinical practice using an image-based algorithm for automated inversion time (TI) selection. MATERIALS AND METHODS: The algorithm selects from BL-LGE TI scout images, the TI corresponding to the image with the highest number of sub-threshold pixels within a region of interest (ROI) encompassing the blood-pool and myocardium. The threshold value corresponds to the most recurrent pixel intensity of all scout images within the ROI...
June 9, 2023: Magma
Juergen Hennig
The paper describes the evolution of low-field MRI from the very early pioneering days in the late 70 s until today. It is not meant to give a comprehensive historical account of the development of MRI, but rather to highlight the different research environments then and now. In the early 90 s, when low-field systems below 1.5 T essentially vanished, there were just no reasonable means available to make up for the factor of roughly three in signal-to-noise-ratio (SNR) between 0.5 and 1.5 T...
June 8, 2023: Magma
Michele N Martin, Kalina V Jordanova, Anthony B Kos, Stephen E Russek, Kathryn E Keenan, Karl F Stupic
OBJECTIVE: Temperature controlled T1 and T2 relaxation times are measured on NiCl2 and MnCl2 solutions from the ISMRM/NIST system phantom at low magnetic field strengths of 6.5 mT, 64 mT and 550 mT. MATERIALS AND METHODS: The T1 and T2 were measured of five samples with increasing concentrations of NiCl2 and five samples with increasing concentrations of MnCl2 . All samples were scanned at 6.5 mT, 64 mT and 550 mT, at sample temperatures ranging from 10 °C to 37 °C...
May 20, 2023: Magma
Bart de Vos, Rob F Remis, Andrew G Webb
OBJECTIVE: Low-cost low-field point-of-care MRI systems are used in many different applications. System design has correspondingly different requirements in terms of imaging field-of-view, spatial resolution and magnetic field strength. In this work an iterative framework has been created to design a cylindrical Halbach-based magnet along with integrated gradient and RF coils that most efficiently fulfil a set of user-specified imaging requirements. METHODS: For efficient integration, target field methods are used for each of the main hardware components...
May 20, 2023: Magma
Kalina V Jordanova, Michele N Martin, Stephen E Ogier, Megan E Poorman, Kathryn E Keenan
OBJECTIVE: To measure healthy brain [Formula: see text] and [Formula: see text] relaxation times at 0.064 T. MATERIALS AND METHODS: [Formula: see text] and [Formula: see text] relaxation times were measured in vivo for 10 healthy volunteers using a 0.064 T magnetic resonance imaging (MRI) system and for 10 test samples on both the MRI and a separate 0.064 T nuclear magnetic resonance (NMR) system. In vivo [Formula: see text] and [Formula: see text] values are reported for white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) for automatic segmentation regions and manual regions of interest (ROIs)...
May 20, 2023: Magma
Andrew Webb, Thomas O'Reilly
OBJECTIVE: To review the major hardware components of low-field point-of-care MRI systems which affect the overall sensitivity. METHODS: Designs for the following components are reviewed and analyzed: magnet, RF coils, transmit/receive switches, preamplifiers, data acquisition system, and methods for grounding and mitigating electromagnetic interference. RESULTS: High homogeneity magnets can be produced in a variety of different designs including C- and H-shaped as well as Halbach arrays...
May 18, 2023: Magma
Thomas O'Reilly, Peter Börnert, Hongyan Liu, Andrew Webb, Kirsten Koolstra
OBJECTIVE: To implement magnetic resonance fingerprinting (MRF) on a permanent magnet 50 mT low-field system deployable as a future point-of-care (POC) unit and explore the quality of the parameter maps. MATERIALS AND METHODS: 3D MRF was implemented on a custom-built Halbach array using a slab-selective spoiled steady-state free precession sequence with 3D Cartesian readout. Undersampled scans were acquired with different MRF flip angle patterns and reconstructed using matrix completion and matched to the simulated dictionary, taking excitation profile and coil ringing into account...
May 18, 2023: Magma
Sara Moscatelli, Peter Gatehouse, Sylvia Krupickova, Raad Mohiaddin, Inga Voges, Daniel Giese, Sonia Nielles-Vallespin, Dudley J Pennell
OBJECTIVES: Two-dimensional (2D) through-plane phase-contrast (PC) cine flow imaging assesses shunts and valve regurgitations in paediatric CMR and is considered the reference standard for Clinical quantification of blood Flow (COF). However, longer breath-holds (BH) can reduce compliance with possibly large respiratory manoeuvres altering flow. We hypothesize that reduced BH time by application of CS (Short BH quantification of Flow) (SBOF) retains accuracy while enabling faster, potentially more reliable flows...
May 18, 2023: Magma
Ali Caglar Özen, Maximilian Frederik Russe, Thomas Lottner, Simon Reiss, Sebastian Littin, Maxim Zaitsev, Michael Bock
OBJECTIVE: Low-field MRI systems are expected to cause less RF heating in conventional interventional devices due to lower Larmor frequency. We systematically evaluate RF-induced heating of commonly used intravascular devices at the Larmor frequency of a 0.55 T system (23.66 MHz) with a focus on the effect of patient size, target organ, and device position on maximum temperature rise. MATERIALS AND METHODS: To assess RF-induced heating, high-resolution measurements of the electric field, temperature, and transfer function were combined...
May 17, 2023: Magma
Rita Schmidt, Elena Kleban, Saskia Bollmann, Christopher J Wiggins, Thoralf Niendorf
No abstract text is available yet for this article.
May 16, 2023: Magma
Daniel Michael Krainak, Rongping Zeng, Ningzhi Li, Terry O'Riska Woods, Jana Gut Delfino
Although there has been a resurgence of interest in low field magnetic resonance imaging (MRI) systems in recent years, low field MRI is not a new concept. FDA has a long history of evaluating the safety and effectiveness of MRI systems encompassing a wide range of field strengths. Many systems seeking marketing authorization today include new technological features (such as artificial intelligence), but this does not fundamentally change the regulatory paradigm for MR systems. In this review, we discuss some of the US regulatory considerations for low field magnetic resonance imaging (MRI) systems, including applicability of existing laws and regulations and how the U...
May 16, 2023: Magma
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