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NMR in Biomedicine

Colleen Bailey, Roger M Bourne, Bernard Siow, Edward W Johnston, Mrishta Brizmohun Appayya, Hayley Pye, Susan Heavey, Thomy Mertzanidou, Hayley Whitaker, Alex Freeman, Dominic Patel, Greg L Shaw, Ashwin Sridhar, David J Hawkes, Shonit Punwani, Daniel C Alexander, Eleftheria Panagiotaki
The VERDICT framework for modelling diffusion MRI data aims to relate parameters from a biophysical model to histological features used for tumour grading in prostate cancer. Validation of the VERDICT model is necessary for clinical use. This study compared VERDICT parameters obtained ex vivo with histology in five specimens from radical prostatectomy. A patient-specific 3D-printed mould was used to investigate the effects of fixation on VERDICT parameters and to aid registration to histology. A rich diffusion data set was acquired in each ex vivo prostate before and after fixation...
February 19, 2019: NMR in Biomedicine
Tania S Vergara Gomez, Marc Dubois, Stanislav Glybovski, Benoit Larrat, Julien de Rosny, Carsten Rockstuhl, Monique Bernard, Redha Abdeddaim, Stefan Enoch, Frank Kober
Earlier work on RF metasurfaces for preclinical MRI has targeted applications such as whole-body imaging and dual-frequency coils. In these studies, a nonresonant loop was used to induce currents into a metasurface that was operated as a passive inductively powered resonator. However, as we show in this study, the strategy of using a resonant metasurface reduces the impact of the loop on the global performance of the assembled coil. To mitigate this deficiency, we developed a new approach that relies on the combination of a commercial surface coil and a coupled-wire structure operated away from its resonance...
February 17, 2019: NMR in Biomedicine
Hyungseok Jang, Michael Carl, Yajun Ma, Saeed Jerban, Tan Guo, Wei Zhao, Eric Y Chang, Jiang Du
PURPOSE: In ultrashort echo time (UTE) imaging, fat suppression can improve short T2 * contrast but can also reduce short T2 * signals. The conventional two-point Dixon (2p-Dixon) method does not perform well due to short T2 * decay. In this study, we propose a new method to suppress fat for high contrast UTE imaging of short T2 tissues, utilizing a single-point Dixon (1p-Dixon) method. METHODS: The proposed method utilizes dual-echo UTE imaging, where UTE is followed by the second TE, chosen flexibly...
February 15, 2019: NMR in Biomedicine
Thomas Puiseux, Anou Sewonu, Olivier Meyrignac, Hervé Rousseau, Franck Nicoud, Simon Mendez, Ramiro Moreno
Several well-resolved 4D Flow MRI acquisitions of an idealized rigid flow phantom featuring an aneurysm, a curved channel as well as a bifurcation were performed under pulsatile regime. The resulting hemodynamics were processed to remove MRI artifacts. Subsequently, they were compared with CFD predictions computed on the same flow domain, using an in-house high-order low dissipative flow solver. Results show that reaching a good agreement is not straightforward but requires proper treatments of both techniques...
February 12, 2019: NMR in Biomedicine
Sanaz Mohajeri, Tedros Bezabeh, Omkar B Ijare, Scott B King, Michael Albert Thomas, Gerald Minuk, Jeremy Lipschitz, Iain Kirkpatrick, Allan B Micflikier, Randy Summers, Ian C P Smith
Primary sclerosing cholangitis (PSC) has been considered to be either an "autoimmune disease" or a "bile acid-induced injury." In vitro MRS studies on PSC patients have limitations due to the contamination of bile with contrast agent (commonly administered during endoscopic retrograde cholangiopancreatography) and/or the use of patient cohorts with other diseases as controls. The objective of this study was to quantify biliary metabolites using in vivo 1 H MRS and gain insight into the pathogenesis of PSC...
February 8, 2019: NMR in Biomedicine
Samantha J Holdsworth, Rafael O'Halloran, Kawin Setsompop
Diffusion-weighted imaging, a contrast unique to MRI, is used for assessment of tissue microstructure in vivo. However, this exquisite sensitivity to finer scales far above imaging resolution comes at the cost of vulnerability to errors caused by sources of motion other than diffusion motion. Addressing the issue of motion has traditionally limited diffusion-weighted imaging to a few acquisition techniques and, as a consequence, to poorer spatial resolution than other MRI applications. Advances in MRI imaging methodology have allowed diffusion-weighted MRI to push to ever higher spatial resolution...
February 7, 2019: NMR in Biomedicine
Daniel Topgaard
Conventional diffusion MRI yields voxel-averaged parameters that suffer from ambiguities for heterogeneous anisotropic materials such as brain tissue. Using principles from solid-state NMR spectroscopy, we have previously introduced the shape of the diffusion encoding tensor as a separate acquisition dimension that disentangles isotropic and anisotropic contributions to the observed diffusivities, thereby allowing for unconstrained data inversion into diffusion tensor distributions with "size," "shape," and orientation dimensions...
February 7, 2019: NMR in Biomedicine
Ahmad Raza Khan, Brian Hansen, Jibrin Danladi, Andrey Chuhutin, Ove Wiborg, Jens R Nyengaard, Sune Nørhøj Jespersen
No abstract text is available yet for this article.
February 1, 2019: NMR in Biomedicine
Christian Guenthner, Sweta Sethi, Marian Troelstra, Ayse Sila Dokumaci, Ralph Sinkus, Sebastian Kozerke
In order to acquire consistent k-space data in MR elastography, a fixed temporal relationship between the MRI sequence and the underlying period of the wave needs to be ensured. To this end, conventional GRE-MRE enforces synchronization through repeated triggering of the transducer and forcing the sequence repetition time to be equal to an integer multiple of the wave period. For wave frequencies below 100 Hz, however, this leads to prolonged acquisition times, as the repetition time scales inversely with frequency...
January 29, 2019: NMR in Biomedicine
John Griffiths
No abstract text is available yet for this article.
January 29, 2019: NMR in Biomedicine
Sarah Atwi, Han Shao, David E Crane, Leodante da Costa, Richard I Aviv, David J Mikulis, Sandra E Black, Bradley J MacIntosh
Cerebrovascular reactivity (CVR) is a dynamic measure of the cerebral blood vessel response to vasoactive stimulus. Conventional CVR measures amplitude changes in the blood-oxygenation-level-dependent (BOLD) signal per unit change in end-tidal CO2 (PET CO2 ), effectively discarding potential timing information. This study proposes a deconvolution procedure to characterize CVR responses based on a vascular transfer function (VTF) that separates amplitude and timing CVR effects. We implemented the CVR-VTF to primarily evaluate normal-appearing white matter (WM) responses in those with a range of small vessel disease...
March 2019: NMR in Biomedicine
Marie-France Penet, Tariq Shah, Flonne Wildes, Balaji Krishnamachary, Santosh K Bharti, Jesus Pacheco-Torres, Dmitri Artemov, Zaver M Bhujwalla
Because of the spatial and temporal heterogeneities of cancers, technologies to investigate cancer cells and the consequences of their interactions with abnormal physiological environments, such as hypoxia and acidic extracellular pH, with stromal cells, and with the extracellular matrix, under controlled conditions, are valuable to gain insights into the functioning of cancers. These insights can lead to an understanding of why cancers invade and metastasize, and identify effective treatment strategies. Here we have provided an overview of the applications of MRI/MRS/MRSI to investigate intact perfused cancer cells, their metabolism and invasion, and their interactions with stromal cells and the extracellular matrix...
January 28, 2019: NMR in Biomedicine
Mikael Montelius, Oscar Jalnefjord, Johan Spetz, Ola Nilsson, Eva Forssell-Aronsson, Maria Ljungberg
Early non-invasive tumour therapy response assessment requires methods sensitive to biological and physiological tumour characteristics. The aim of this study was to find and evaluate magnetic resonance imaging (MRI) derived tumour tissue parameters that correlate with histological parameters and that reflect effects of radionuclide therapy. Mice bearing a subcutaneous human small-intestine neuroendocrine tumour were i.v. injected with 177 Lu-octreotate. MRI was performed (7 T Bruker Biospec) on different post-therapy intervals (1 and 13 days) using T2-weighted imaging, mapping of T2* and T1 relaxation time constants, as well as diffusion and dynamic contrast enhancement (DCE-MRI) techniques...
January 28, 2019: NMR in Biomedicine
Hsin-Yu Chen, Jeremy W Gordon, Robert A Bok, Peng Cao, Cornelius von Morze, Mark van Criekinge, Eugene Milshteyn, Lucas Carvajal, Ralph E Hurd, John Kurhanewicz, Daniel B Vigneron, Peder E Z Larson
Hyperpolarized 13 C MRI takes advantage of the unprecedented 50 000-fold signal-to-noise ratio enhancement to interrogate cancer metabolism in patients and animals. It can measure the pyruvate-to-lactate conversion rate, kPL , a metabolic biomarker of cancer aggressiveness and progression. Therefore, it is crucial to evaluate kPL reliably. In this study, three sequence components and parameters that modulate kPL estimation were identified and investigated in model simulations and through in vivo animal studies using several specifically designed pulse sequences...
January 21, 2019: NMR in Biomedicine
Elvisha Dhamala, Ines Abdelkefi, Mavesa Nguyen, T Jay Hennessy, Hélène Nadeau, Jamie Near
PURPOSE: In vivo magnetic resonance spectroscopy (MRS) is the only technique capable of non-invasively assessing metabolite concentrations in the brain. The lack of alternative methods makes validation of MRS measures challenging. The aim of this study is to assess the validity of MRS measures of human brain metabolite concentrations by comparing multiple MRS measures acquired using different MRS acquisition sequences. METHODS: Single-voxel SPECIAL and MEGA-PRESS MR spectra were acquired from both the dorsolateral prefrontal cortex and primary motor cortices in 15 healthy subjects...
January 21, 2019: NMR in Biomedicine
Roman Wesolowski, Nicholas P Blockley, Ian D Driver, Susan T Francis, Penny A Gowland
A better understanding of the coupling between changes in cerebral blood flow (CBF) and cerebral blood volume (CBV) is vital for furthering our understanding of the BOLD response. The aim of this study was to measure CBF-CBV coupling in different vascular compartments during neural activation. Three haemodynamic parameters were measured during a visual stimulus. Look-Locker flow-sensitive alternating inversion recovery was used to measure changes in CBF and arterial CBV (CBVa ) using sequence parameters optimized for each contrast...
January 18, 2019: NMR in Biomedicine
Alexandra Tobisch, Thomas Schultz, Rüdiger Stirnberg, Gabriel Varela-Mattatall, Hans Knutsson, Pablo Irarrázaval, Tony Stöcker
Time constraints placed on magnetic resonance imaging often restrict the application of advanced diffusion MRI (dMRI) protocols in clinical practice and in high throughput research studies. Therefore, acquisition strategies for accelerated dMRI have been investigated to allow for the collection of versatile and high quality imaging data, even if stringent scan time limits are imposed. Diffusion spectrum imaging (DSI), an advanced acquisition strategy that allows for a high resolution of intra-voxel microstructure, can be sufficiently accelerated by means of compressed sensing (CS) theory...
January 14, 2019: NMR in Biomedicine
Rohini Vidya Shankar, John C Chang, Houchun H Hu, Vikram D Kodibagkar
Magnetic resonance spectroscopic imaging (MRSI) is an important technique for assessing the spatial variation of metabolites in vivo. The long scan times in MRSI limit clinical applicability due to patient discomfort, increased costs, motion artifacts, and limited protocol flexibility. Faster acquisition strategies can address these limitations and could potentially facilitate increased adoption of MRSI into routine clinical protocols with minimal addition to the current anatomical and functional acquisition protocols in terms of imaging time...
January 14, 2019: NMR in Biomedicine
Margarida Julià-Sapé, Ana Paula Candiota, Carles Arús
The contribution of MRS(I) to the in vivo evaluation of cancer-metabolism-derived metrics, mostly since 2016, is reviewed here. Increased carbon consumption by tumour cells, which are highly glycolytic, is now being sampled by 13 C magnetic resonance spectroscopic imaging (MRSI) following the injection of hyperpolarized [1-13 C] pyruvate (Pyr). Hot-spots of, mostly, increased lactate dehydrogenase activity or flow between Pyr and lactate (Lac) have been seen with cancer progression in prostate (preclinical and in humans), brain and pancreas (both preclinical) tumours...
January 11, 2019: NMR in Biomedicine
Sarah S Dinges, Lindsey A Vandergrift, Shulin Wu, Yannick Berker, Piet Habbel, Matthias Taupitz, Chin-Lee Wu, Leo L Cheng
In this article, we review the state of the field of high resolution magic angle spinning MRS (HRMAS MRS)-based cancer metabolomics since its beginning in 2004; discuss the concept of cancer metabolomic fields, where metabolomic profiles measured from histologically benign tissues reflect patient cancer status; and report our HRMAS MRS metabolomic results, which characterize metabolomic fields in prostatectomy-removed cancerous prostates. Three-dimensional mapping of cancer lesions throughout each prostate enabled multiple benign tissue samples per organ to be classified based on distance from and extent of the closest cancer lesion as well as the Gleason score (GS) of the entire prostate...
January 4, 2019: NMR in Biomedicine
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