Yashwant Kurmi, Malvika Viswanathan, Zhongliang Zu
PURPOSE: To develop a SNR enhancement method for CEST imaging using a denoising convolutional autoencoder (DCAE) and compare its performance with state-of-the-art denoising methods. METHOD: The DCAE-CEST model encompasses an encoder and a decoder network. The encoder learns features from the input CEST Z-spectrum via a series of one-dimensional convolutions, nonlinearity applications, and pooling. Subsequently, the decoder reconstructs an output denoised Z-spectrum using a series of up-sampling and convolution layers...
July 19, 2024: Magnetic Resonance in Medicine
Shihan Qiu, Lixia Wang, Pascal Sati, Anthony G Christodoulou, Yibin Xie, Debiao Li
PURPOSE: To develop a self-supervised learning method to retrospectively estimate T1 and T2 values from clinical weighted MRI. METHODS: A self-supervised learning approach was constructed to estimate T1 , T2 , and proton density maps from conventional T1 - and T2 -weighted images. MR physics models were employed to regenerate the weighted images from the network outputs, and the network was optimized based on loss calculated between the synthesized and input weighted images, alongside additional constraints based on prior information...
July 16, 2024: Magnetic Resonance in Medicine
Divya S Bolar, Ryan A Barnes, Conan Chen, Fei Han, Josef Pfeuffer, Thomas T Liu, Eric C Wong
PURPOSE: To mitigate the B0 /B1 + sensitivity of velocity-selective inversion (VSI) pulse trains for velocity-selective arterial spin labeling (VSASL) by implementing adiabatic refocusing. This approach aims to achieve artifact-free VSI-based perfusion imaging through single-pair label-control subtractions, reducing the need for the currently required four-pair dynamic phase-cycling (DPC) technique when using a velocity-insensitive control. METHODS: We introduce a Fourier-transform VSI (FT-VSI) train that incorporates sinc-modulated hard excitation pulses with MLEV-8-modulated adiabatic hyperbolic secant refocusing pairs...
July 16, 2024: Magnetic Resonance in Medicine
Nienke P M Wassenaar, Oliver J Gurney-Champion, Anne-Sophie van Schelt, Tom Bruijnen, Hanneke W M van Laarhoven, Jaap Stoker, Aart J Nederveen, Jurgen H Runge, Eric M Schrauben
PURPOSE: For reliable DCE MRI parameter estimation, k-space undersampling is essential to meet resolution, coverage, and signal-to-noise requirements. Pseudo-spiral (PS) sampling achieves this by sampling k-space on a Cartesian grid following a spiral trajectory. The goal was to optimize PS k-space sampling patterns for abdomin al DCE MRI. METHODS: The optimal PS k-space sampling pattern was determined using an anthropomorphic digital phantom. Contrast agent inflow was simulated in the liver, spleen, pancreas, and pancreatic ductal adenocarcinoma (PDAC)...
July 14, 2024: Magnetic Resonance in Medicine
Nicolas Boulant, Samantha Ma, Erica Walker, Alexander Beckett, An T Vu, Shajan Gunamony, David A Feinberg
PURPOSE: Driven by the Lorentz force, acoustic noise may arguably be the next physiological challenge associated with ultra-high field MRI scanners and powerful gradient coils. This work consisted of isolating and mitigating the main sound pathway in the NexGen 7 T scanner equipped with the investigational Impulse head gradient coil. METHODS: Sound pressure level (SPL) measurements were performed with and without the RF coil to assess its acoustic impact...
July 14, 2024: Magnetic Resonance in Medicine
Ariel J Hannum, Tyler E Cork, Kawin Setsompop, Daniel B Ennis
PURPOSE: Diffusion encoding gradient waveforms can impart intra-voxel and inter-voxel dephasing owing to bulk motion, limiting achievable signal-to-noise and complicating multishot acquisitions. In this study, we characterize improvements in phase consistency via gradient moment nulling of diffusion encoding waveforms. METHODS: Healthy volunteers received neuro ( <mml:math xmlns:mml=""> <mml:semantics><mml:mrow><mml:mi>N</mml:mi> <mml:mo>=</mml:mo> <mml:mn>10</mml:mn></mml:mrow> <mml:annotation>$$ N=10 $$</mml:annotation></mml:semantics> </mml:math> ) and cardiac ( <mml:math xmlns:mml="https://www...
July 12, 2024: Magnetic Resonance in Medicine
Bilal Tasdelen, Nam G Lee, Sophia X Cui, Krishna S Nayak
PURPOSE: Breath-held fat-suppressed volumetric T1-weighted MRI is an important and widely-used technique for evaluating the abdomen. Both fat-saturation and Dixon-based fat-suppression methods are used at conventional field strengths; however, both have challenges at lower field strengths (<1.5T) due to insufficient fat suppression and/or inadequate resolution. Specifically, at lower field strengths, fat saturation often fails due to the short T1 of lipid; and Cartesian Dixon imaging provides poor spatial resolution due to the need for a long ∆TE, due to the smaller ∆f between water and lipid...
July 12, 2024: Magnetic Resonance in Medicine
Alexander R Toews, Philip K Lee, Krishna S Nayak, Brian A Hargreaves
PURPOSE: Comprehensive assessment of image quality requires accounting for spatial variations in (i) intensity artifact, (ii) geometric distortion, (iii) signal-to-noise ratio (SNR), and (iv) spatial resolution, among other factors. This work presents an ensemble of methods to meet this need, from phantom design to image analysis, and applies it to the scenario of imaging near metal. METHODS: A modular phantom design employing a gyroid lattice is developed to enable the co-registered volumetric quantitation of image quality near a metallic hip implant...
July 12, 2024: Magnetic Resonance in Medicine
Dunja Simicic, Helge J Zöllner, Christopher W Davies-Jenkins, Kathleen E Hupfeld, Richard A E Edden, Georg Oeltzschner
PURPOSE: Retrospective frequency-and-phase correction (FPC) methods attempt to remove frequency-and-phase variations between transients to improve the quality of the averaged MR spectrum. However, traditional FPC methods like spectral registration struggle at low SNR. Here, we propose a method that directly integrates FPC into a 2D linear-combination model (2D-LCM) of individual transients ("model-based FPC"). We investigated how model-based FPC performs compared to the traditional approach, i...
July 10, 2024: Magnetic Resonance in Medicine
Horace Z Zhang, Nahla M H Elsaid, Heng Sun, Hemant D Tagare, Gigi Galiana
PURPOSE: To standardize T <mml:math xmlns:mml=""> <mml:semantics> <mml:mrow><mml:msub><mml:mo> </mml:mo> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:msub> </mml:mrow> <mml:annotation>$$ {}_2 $$</mml:annotation></mml:semantics> </mml:math> -weighted images from clinical Turbo Spin Echo (TSE) scans by generating corresponding T <mml:math xmlns:mml="https://www...
July 10, 2024: Magnetic Resonance in Medicine
Rüdiger Stirnberg, Andreas Deistung, Jürgen R Reichenbach, Monique M B Breteler, Tony Stöcker
PURPOSE: To explore the high signal-to-noise ratio (SNR) efficiency of interleaved multishot 3D-EPI with standard image reconstruction for fast and robust high-resolution whole-brain quantitative susceptibility (QSM) and <mml:math xmlns:mml=""> <mml:semantics> <mml:mrow> <mml:msubsup><mml:mrow><mml:mi>R</mml:mi></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> <mml:mrow><mml:mo>∗</mml:mo></mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation>$$ {R}_2^{\ast } $$</mml:annotation></mml:semantics> </mml:math> mapping at 7 and 3T...
July 10, 2024: Magnetic Resonance in Medicine
Difei Wang, Rüdiger Stirnberg, Tony Stöcker
PURPOSE: The transverse relaxation time T <mml:math xmlns:mml=""> <mml:semantics> <mml:mrow> <mml:msub><mml:mrow><mml:mo> </mml:mo></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:msub> </mml:mrow> <mml:annotation>$$ {}_2 $$</mml:annotation></mml:semantics> </mml:math> holds significant relevance in clinical applications and research studies...
July 10, 2024: Magnetic Resonance in Medicine
Constantin von Deuster, Daniel Nanz
PURPOSE: Fluid-sensitive turbo spin echo (TSE) MRI with short-TI inversion-recovery preparation for fat suppression (STIR) plays a critical role in the diagnostics of the musculoskeletal system (e.g., close to metal implants). Potential advantages of 3D acquisitions, however, are difficult to exploit due to long acquisition times. Shortening the TR incurs a signal loss, and a driven-equilibrium (DE) extension reduces fluid signal even further. METHODS: The phase of the flip-back pulse was changed by 180° relative to the conventional implementation (i...
July 10, 2024: Magnetic Resonance in Medicine
Matthijs H S de Buck, Aaron T Hess, Peter Jezzard
PURPOSE: T2-weighted DANTE-SPACE (Delay Alternating with Nutation for Tailored Excitation - Sampling Perfection with Application optimized Contrasts using different flip angle Evolution) sequences facilitate non-invasive intracranial vessel wall imaging at 7T through simultaneous suppression of blood and CSF. However, the achieved vessel wall delineation depends closely on the selected sequence parameters, and little information is available about the performance of the sequence using more widely available 3T MRI...
July 6, 2024: Magnetic Resonance in Medicine
Zekang Ding, Huajun She, Qun Chen, Yiping P Du
PURPOSE: To reduce the ringing artifacts of the motion-resolved images in free-breathing dynamic pulmonary MRI. METHODS: A golden-step based interleaving (GSI) technique was proposed to reduce ringing artifacts induced by diaphragm drifting. The pulmonary MRI data were acquired using a superior-inferior navigated 3D radial UTE sequence in an interleaved manner during free breathing. Successive interleaves were acquired in an incoherent fashion along the polar direction...
July 5, 2024: Magnetic Resonance in Medicine
Jordina Aviles Verdera, Raphael Tomi-Tricot, Lisa Story, Mary A Rutherford, Sebastien Ourselin, Joseph V Hajnal, Shaihan J Malik, Jana Hutter
PURPOSE: T1 mapping and T1-weighted contrasts have a complimentary but currently under utilized role in fetal MRI. Emerging clinical low field scanners are ideally suited for fetal T1 mapping. The advantages are lower T1 values which results in higher efficiency and reduced field inhomogeneities resulting in a decreased requirement for specialist tools. In addition the increased bore size associated with low field scanners provides improved patient comfort and accessibility. This study aims to demonstrate the feasibility of fetal brain T1 mapping at 0...
July 5, 2024: Magnetic Resonance in Medicine
Michael C Steckner, David Grainger, Geoff Charles-Edwards
The "5 gauss line" is a phrase that is likely to be familiar to everyone working with MRI, but what is its significance, how was it defined, and what changes are currently in progress? This review explores the history of 5 gauss (0.5 mT) as a threshold for protecting against inadvertently putting cardiac pacemakers, implantable cardioverter defibrillators, and other active implantable medical devices into a "magnet mode." Additionally, it describes the background to the recent change of this threshold to 9 gauss (0...
July 5, 2024: Magnetic Resonance in Medicine
S Pala, A Paajanen, A Ristaniemi, E Nippolainen, I O Afara, O Nykänen, M J Nissi
PURPOSE: To assess the potential for accelerating continuous-wave (CW) T1ρ dispersion measurement with compressed sensing approach via studying the effect that the data reduction has on the ability to detect differences between intact and degenerated articular cartilage with different spin-lock amplitudes and to assess quantitative bias due to acceleration. METHODS: Osteochondral plugs (n = 27, 4 mm diameter) from femur (n = 14) and tibia (n = 13) regions from human cadaver knee joints were obtained from commercial biobank (Science Care, USA) under Ethical permission 134/2015...
July 2, 2024: Magnetic Resonance in Medicine
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July 1, 2024: Magnetic Resonance in Medicine
Friederike Hesse, Jacob Low, Jianbo Cao, Flaviu Bulat, Felix Kreis, Alan J Wright, Kevin M Brindle
PURPOSE: Serine is a major source of one-carbon units needed for the synthesis of nucleotides and the production of intramitochondrial nicotinamide adenine dinucleotide phosphate (NADPH), and it plays an important role in cancer cell proliferation. The aim of this study was to develop a deuterium (2 H) MRS imaging method for imaging tumor serine metabolism. METHODS: Sequential (2 H) spectra and spectroscopic images were used to monitor the metabolism of [2,3,3-2 H3 ]serine in patient-derived glioblastoma cells in vitro and in tumors obtained by their orthotopic implantation in mouse brain...
June 30, 2024: Magnetic Resonance in Medicine
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