Sensors

Editorial

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4 pages, 628 KiB

Open AccessEditorial

Magnetic Resonance Sensors

by Robert H. Morris and Michael I. Newton

Sensors 2014, 14(11), 21722-21725; https://doi.org/10.3390/s141121722 - 17 Nov 2014

Cited by 1 | Viewed by 6086

Abstract

Magnetic Resonance finds countless applications, from spectroscopy to imaging, routinely in almost all research and medical institutions across the globe. It is also becoming more frequently used for specific applications in which the whole instrument and system is designed for a dedicated application. [...] Read more.

Magnetic Resonance finds countless applications, from spectroscopy to imaging, routinely in almost all research and medical institutions across the globe. It is also becoming more frequently used for specific applications in which the whole instrument and system is designed for a dedicated application. With beginnings in borehole logging for the petro-chemical industry Magnetic Resonance sensors have been applied to fields as varied as online process monitoring for food manufacture and medical point of care diagnostics. This great diversity is seeing exciting developments in magnetic resonance sensing technology published in application specific journals where they are often not seen by the wider sensor community. It is clear that there is enormous interest in magnetic resonance sensors which represents a significant growth area. The aim of this special edition of Sensors was to address the wide distribution of relevant articles by providing a forum to disseminate cutting edge research in this field in a single open source publication.[...] Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

Research

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19 pages, 888 KiB

Open AccessArticle

Simultaneous Magnetic Resonance Imaging and Consolidation Measurement of Articular Cartilage

by Robert Mark Wellard, Jean-Philippe Ravasio, Samuel Guesne, Christopher Bell, Adekunle Oloyede, Greg Tevelen, James M. Pope and Konstantin I. Momot

Sensors 2014, 14(5), 7940-7958; https://doi.org/10.3390/s140507940 - 5 May 2014

Cited by 19 | Viewed by 8263

Abstract

Magnetic resonance imaging (MRI) offers the opportunity to study biological tissues and processes in a non-disruptive manner. The technique shows promise for the study of the load-bearing performance (consolidation) of articular cartilage and changes in articular cartilage accompanying osteoarthritis. Consolidation of articular cartilage [...] Read more.

Magnetic resonance imaging (MRI) offers the opportunity to study biological tissues and processes in a non-disruptive manner. The technique shows promise for the study of the load-bearing performance (consolidation) of articular cartilage and changes in articular cartilage accompanying osteoarthritis. Consolidation of articular cartilage involves the recording of two transient characteristics: the change over time of strain and the hydrostatic excess pore pressure (HEPP). MRI study of cartilage consolidation under mechanical load is limited by difficulties in measuring the HEPP in the presence of the strong magnetic fields associated with the MRI technique. Here we describe the use of MRI to image and characterize bovine articular cartilage deforming under load in an MRI compatible consolidometer while monitoring pressure with a Fabry-Perot interferometer-based fiber-optic pressure transducer. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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9 pages, 537 KiB

Open AccessArticle

Degradation of Phosphate Ester Hydraulic Fluid in Power Station Turbines Investigated by a Three-Magnet Unilateral Magnet Array

by Pan Guo, Wei He and Juan C. García-Naranjo

Sensors 2014, 14(4), 6797-6805; https://doi.org/10.3390/s140406797 - 14 Apr 2014

Cited by 7 | Viewed by 7235

Abstract

A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the ¹H-NMR transverse and [...] Read more.

A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the ¹H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T_2eff and longitudinal relaxation time T₁ were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T_2eff,long and T_1,long. This indicates that the T_2eff,long and T_1,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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10 pages, 331 KiB

Open AccessArticle

Towards Using NMR to Screen for Spoiled Tomatoes Stored in 1,000 L, Aseptically Sealed, Metal-Lined Totes

by Michael D. Pinter, Tod Harter, Michael J. McCarthy and Matthew P. Augustine

Sensors 2014, 14(3), 4167-4176; https://doi.org/10.3390/s140304167 - 3 Mar 2014

Cited by 23 | Viewed by 6569

Abstract

Nuclear magnetic resonance (NMR) spectroscopy is used to track factory relevant tomato paste spoilage. It was found that spoilage in tomato paste test samples leads to longer spin lattice relaxation times T₁ using a conventional low magnetic field NMR system. The increase [...] Read more.

Nuclear magnetic resonance (NMR) spectroscopy is used to track factory relevant tomato paste spoilage. It was found that spoilage in tomato paste test samples leads to longer spin lattice relaxation times T₁ using a conventional low magnetic field NMR system. The increase in T₁ value for contaminated samples over a five day room temperature exposure period prompted the work to be extended to the study of industry standard, 1,000 L, non-ferrous, metal-lined totes. NMR signals and T₁ values were recovered from a large format container with a single-sided NMR sensor. The results of this work suggest that a handheld NMR device can be used to study tomato paste spoilage in factory process environments. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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17 pages, 2322 KiB

Open AccessArticle

Optimal Configuration for Relaxation Times Estimation in Complex Spin Echo Imaging

by Fabio Baselice, Giampaolo Ferraioli, Alessandro Grassia and Vito Pascazio

Sensors 2014, 14(2), 2182-2198; https://doi.org/10.3390/s140202182 - 28 Jan 2014

Cited by 23 | Viewed by 6919

Abstract

Many pathologies can be identified by evaluating differences raised in the physical parameters of involved tissues. In a Magnetic Resonance Imaging (MRI) framework, spin-lattice T₁ and spin-spin T₂ relaxation time parameters play a major role in such an identification. In this [...] Read more.

Many pathologies can be identified by evaluating differences raised in the physical parameters of involved tissues. In a Magnetic Resonance Imaging (MRI) framework, spin-lattice T₁ and spin-spin T₂ relaxation time parameters play a major role in such an identification. In this manuscript, a theoretical study related to the evaluation of the achievable performances in the estimation of relaxation times in MRI is proposed. After a discussion about the considered acquisition model, an analysis on the ideal imaging acquisition parameters in the case of spin echo sequences, i.e., echo and repetition times, is conducted. In particular, the aim of the manuscript consists in providing an empirical rule for optimal imaging parameter identification with respect to the tissues under investigation. Theoretical results are validated on different datasets in order to show the effectiveness of the presented study and of the proposed methodology. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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8 pages, 290 KiB

Open AccessCommunication

Detection of Virgin Olive Oil Adulteration Using Low Field Unilateral NMR

by Zheng Xu, Robert H. Morris, Martin Bencsik and Michael I. Newton

Sensors 2014, 14(2), 2028-2035; https://doi.org/10.3390/s140202028 - 24 Jan 2014

Cited by 64 | Viewed by 10494

Abstract

The detection of adulteration in edible oils is a concern in the food industry, especially for the higher priced virgin olive oils. This article presents a low field unilateral nuclear magnetic resonance (NMR) method for the detection of the adulteration of virgin olive [...] Read more.

The detection of adulteration in edible oils is a concern in the food industry, especially for the higher priced virgin olive oils. This article presents a low field unilateral nuclear magnetic resonance (NMR) method for the detection of the adulteration of virgin olive oil that can be performed through sealed bottles providing a non-destructive screening technique. Adulterations of an extra virgin olive oil with different percentages of sunflower oil and red palm oil were measured with a commercial unilateral instrument, the profile NMR-Mouse. The NMR signal was processed using a 2-dimensional Inverse Laplace transformation to analyze the transverse relaxation and self-diffusion behaviors of different oils. The obtained results demonstrated the feasibility of detecting adulterations of olive oil with percentages of at least 10% of sunflower and red palm oils. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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22 pages, 805 KiB

Open AccessArticle

Calibrationless Parallel Magnetic Resonance Imaging: A Joint Sparsity Model

by Angshul Majumdar, Kunal Narayan Chaudhury and Rabab Ward

Sensors 2013, 13(12), 16714-16735; https://doi.org/10.3390/s131216714 - 5 Dec 2013

Cited by 11 | Viewed by 6562

Abstract

State-of-the-art parallel MRI techniques either explicitly or implicitly require certain parameters to be estimated, e.g., the sensitivity map for SENSE, SMASH and interpolation weights for GRAPPA, SPIRiT. Thus all these techniques are sensitive to the calibration (parameter estimation) stage. In this work, we [...] Read more.

State-of-the-art parallel MRI techniques either explicitly or implicitly require certain parameters to be estimated, e.g., the sensitivity map for SENSE, SMASH and interpolation weights for GRAPPA, SPIRiT. Thus all these techniques are sensitive to the calibration (parameter estimation) stage. In this work, we have proposed a parallel MRI technique that does not require any calibration but yields reconstruction results that are at par with (or even better than) state-of-the-art methods in parallel MRI. Our proposed method required solving non-convex analysis and synthesis prior joint-sparsity problems. This work also derives the algorithms for solving them. Experimental validation was carried out on two datasets—eight channel brain and eight channel Shepp-Logan phantom. Two sampling methods were used—Variable Density Random sampling and non-Cartesian Radial sampling. For the brain data, acceleration factor of 4 was used and for the other an acceleration factor of 6 was used. The reconstruction results were quantitatively evaluated based on the Normalised Mean Squared Error between the reconstructed image and the originals. The qualitative evaluation was based on the actual reconstructed images. We compared our work with four state-of-the-art parallel imaging techniques; two calibrated methods—CS SENSE and l1SPIRiT and two calibration free techniques—Distributed CS and SAKE. Our method yields better reconstruction results than all of them. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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18 pages, 314 KiB

Open AccessArticle

Software Defined Radio (SDR) and Direct Digital Synthesizer (DDS) for NMR/MRI Instruments at Low-Field

by Aktham Asfour, Kosai Raoof and Jean-Paul Yonnet

Sensors 2013, 13(12), 16245-16262; https://doi.org/10.3390/s131216245 - 27 Nov 2013

Cited by 16 | Viewed by 12508

Abstract

A proof-of-concept of the use of a fully digital radiofrequency (RF) electronics for the design of dedicated Nuclear Magnetic Resonance (NMR) systems at low-field (0.1 T) is presented. This digital electronics is based on the use of three key elements: a Direct Digital [...] Read more.

A proof-of-concept of the use of a fully digital radiofrequency (RF) electronics for the design of dedicated Nuclear Magnetic Resonance (NMR) systems at low-field (0.1 T) is presented. This digital electronics is based on the use of three key elements: a Direct Digital Synthesizer (DDS) for pulse generation, a Software Defined Radio (SDR) for a digital receiving of NMR signals and a Digital Signal Processor (DSP) for system control and for the generation of the gradient signals (pulse programmer). The SDR includes a direct analog-to-digital conversion and a Digital Down Conversion (digital quadrature demodulation, decimation filtering, processing gain…). The various aspects of the concept and of the realization are addressed with some details. These include both hardware design and software considerations. One of the underlying ideas is to enable such NMR systems to “enjoy” from existing advanced technology that have been realized in other research areas, especially in telecommunication domain. Another goal is to make these systems easy to build and replicate so as to help research groups in realizing dedicated NMR desktops for a large palette of new applications. We also would like to give readers an idea of the current trends in this field. The performances of the developed electronics are discussed throughout the paper. First FID (Free Induction Decay) signals are also presented. Some development perspectives of our work in the area of low-field NMR/MRI will be finally addressed. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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15 pages, 1842 KiB

Open AccessArticle

Embedded NMR Sensor to Monitor Compressive Strength Development and Pore Size Distribution in Hydrating Concrete

by Floriberto Díaz-Díaz, Prisciliano F. De J. Cano-Barrita, Bruce J. Balcom, Sergio E. Solís-Nájera and Alfredo O. Rodríguez

Sensors 2013, 13(12), 15985-15999; https://doi.org/10.3390/s131215985 - 25 Nov 2013

Cited by 25 | Viewed by 8814

Abstract

In cement-based materials porosity plays an important role in determining their mechanical and transport properties. This paper describes an improved low–cost embeddable miniature NMR sensor capable of non-destructively measuring evaporable water loss and porosity refinement in low and high water-to-cement ratio cement-based materials. [...] Read more.

In cement-based materials porosity plays an important role in determining their mechanical and transport properties. This paper describes an improved low–cost embeddable miniature NMR sensor capable of non-destructively measuring evaporable water loss and porosity refinement in low and high water-to-cement ratio cement-based materials. The sensor consists of two NdFeB magnets having their North and South poles facing each other, separated by 7 mm to allow space for a Faraday cage containing a Teflon tube and an ellipsoidal RF coil. To account for magnetic field changes due to temperature variations, and/or the presence of steel rebars, or frequency variation due to sample impedance, an external tuning circuit was employed. The sensor performance was evaluated by analyzing the transverse magnetization decay obtained with a CPMG measurement from different materials, such as a polymer phantom, fresh white and grey cement pastes with different w/c ratios and concrete with low (0.30) and high (0.6) w/c ratios. The results indicated that the sensor is capable of detecting changes in water content in fresh cement pastes and porosity refinement caused by cement hydration in hardened materials, even if they are prepared with a low w/c ratio (w/c = 0.30). The short lifetime component of the transverse relaxation rate is directly proportional to the compressive strength of concrete determined by destructive testing. The r² (0.97) from the linear relationship observed is similar to that obtained using T₂ data from a commercial Oxford Instruments 12.9 MHz spectrometer. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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12 pages, 509 KiB

Open AccessArticle

Sensing Lanthanide Metal Content in Biological Tissues with Magnetic Resonance Spectroscopy

by Dina V. Hingorani, Sandra I. Gonzalez, Jessica F. Li and Mark D. Pagel

Sensors 2013, 13(10), 13732-13743; https://doi.org/10.3390/s131013732 - 11 Oct 2013

Cited by 3 | Viewed by 6333

Abstract

The development and validation of MRI contrast agents consisting of a lanthanide chelate often requires a determination of the concentration of the agent in ex vivo tissue. We have developed a protocol that uses 70% nitric acid to completely digest tissue samples that [...] Read more.

The development and validation of MRI contrast agents consisting of a lanthanide chelate often requires a determination of the concentration of the agent in ex vivo tissue. We have developed a protocol that uses 70% nitric acid to completely digest tissue samples that contain Gd(III), Dy(III), Tm(III), Eu(III), or Yb(III) ions, or the MRI contrast agent gadodiamide. NMR spectroscopy of coaxial tubes containing a digested sample and a separate control solution of nitric acid was used to rapidly and easily measure the bulk magnetic susceptibility (BMS) shift caused by each lanthanide ion and gadodiamide. Each BMS shift was shown to be linearly correlated with the concentration of each lanthanide ion and gadodiamide in the 70% nitric acid solution and in digested rat kidney and liver tissues. These concentration measurements had outstanding precision, and also had good accuracy for concentrations ³10 mM for Tm(III) Eu(III), and Yb(III), and ³3 mM for Gd(III), gadodiamide, and Dy(III). Improved sample handling methods are needed to improve measurement accuracy for samples with lower concentrations. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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9 pages, 412 KiB

Open AccessArticle

Fetal Electrocardiogram (fECG) Gated MRI

by Martyn N.J. Paley, Janet E. Morris, Debbie Jarvis and Paul D. Griffiths

Sensors 2013, 13(9), 11271-11279; https://doi.org/10.3390/s130911271 - 23 Aug 2013

Cited by 10 | Viewed by 10353

Abstract

We have developed a Magnetic Resonance Imaging (MRI)-compatible system to enable gating of a scanner to the heartbeat of a foetus for cardiac, umbilical cord flow and other possible imaging applications. We performed radiofrequency safety testing prior to a fetal electrocardiogram (fECG) gated [...] Read more.

We have developed a Magnetic Resonance Imaging (MRI)-compatible system to enable gating of a scanner to the heartbeat of a foetus for cardiac, umbilical cord flow and other possible imaging applications. We performed radiofrequency safety testing prior to a fetal electrocardiogram (fECG) gated imaging study in pregnant volunteers (n = 3). A compact monitoring device with advanced software capable of reliably detecting both the maternal electrocardiogram (mECG) and fECG simultaneously was modified by the manufacturer (Monica Healthcare, Nottingham, UK) to provide an external TTL trigger signal from the detected fECG which could be used to trigger a standard 1.5 T MR (GE Healthcare, Milwaukee, WI, USA) gating system with suitable attenuation. The MR scanner was tested by triggering rapidly during image acquisition at a typical fetal heart rate (123 beats per minute) using a simulated fECG waveform fed into the gating system. Gated MR images were also acquired from volunteers who were attending for a repeat fetal Central Nervous System (CNS) examination using an additional rapid cardiac imaging sequence triggered from the measured fECG. No adverse safety effects were encountered. This is the first time fECG gating has been used with MRI and opens up a range of new possibilities to study a developing foetus. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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Review

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22 pages, 3202 KiB

Open AccessReview

Hyperpolarized NMR Probes for Biological Assays

by Sebastian Meier, Pernille R. Jensen, Magnus Karlsson and Mathilde H. Lerche

Sensors 2014, 14(1), 1576-1597; https://doi.org/10.3390/s140101576 - 16 Jan 2014

Cited by 49 | Viewed by 10918

Abstract

During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized) molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and [...] Read more.

During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized) molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and detected with high sensitivity and contrast against background signals using high resolution NMR spectroscopy. A variety of natural, derivatized and designed hyperpolarized probes has emerged for diverse biological studies including assays of intracellular reaction progression, pathway kinetics, probe uptake and export, pH, redox state, reactive oxygen species, ion concentrations, drug efficacy or oncogenic signaling. These probes are readily used directly under natural conditions in biofluids and are often directly developed and optimized for cellular assays, thus leaving little doubt about their specificity and utility under biologically relevant conditions. Hyperpolarized molecular probes for biological NMR spectroscopy enable the unbiased detection of complex processes by virtue of the high spectral resolution, structural specificity and quantifiability of NMR signals. Here, we provide a survey of strategies used for the selection, design and use of hyperpolarized NMR probes in biological assays, and describe current limitations and developments. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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16 pages, 414 KiB

Open AccessReview

Optical Fiber-Based MR-Compatible Sensors for Medical Applications: An Overview

by Fabrizio Taffoni, Domenico Formica, Paola Saccomandi, Giovanni Di Pino and Emiliano Schena

Sensors 2013, 13(10), 14105-14120; https://doi.org/10.3390/s131014105 - 18 Oct 2013

Cited by 193 | Viewed by 15449

Abstract

During last decades, Magnetic Resonance (MR)—compatible sensors based on different techniques have been developed due to growing demand for application in medicine. There are several technological solutions to design MR-compatible sensors, among them, the one based on optical fibers presents several attractive features. [...] Read more.

During last decades, Magnetic Resonance (MR)—compatible sensors based on different techniques have been developed due to growing demand for application in medicine. There are several technological solutions to design MR-compatible sensors, among them, the one based on optical fibers presents several attractive features. The high elasticity and small size allow designing miniaturized fiber optic sensors (FOS) with metrological characteristics (e.g., accuracy, sensitivity, zero drift, and frequency response) adequate for most common medical applications; the immunity from electromagnetic interference and the absence of electrical connection to the patient make FOS suitable to be used in high electromagnetic field and intrinsically safer than conventional technologies. These two features further heightened the potential role of FOS in medicine making them especially attractive for application in MRI. This paper provides an overview of MR-compatible FOS, focusing on the sensors employed for measuring physical parameters in medicine (i.e., temperature, force, torque, strain, and position). The working principles of the most promising FOS are reviewed in terms of their relevant advantages and disadvantages, together with their applications in medicine. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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23 pages, 1424 KiB

Open AccessReview

Magnetic Resonance Imaging of Ischemia Viability Thresholds and the Neurovascular Unit

by Philip A. Barber

Sensors 2013, 13(6), 6981-7003; https://doi.org/10.3390/s130606981 - 27 May 2013

Cited by 23 | Viewed by 9199

Abstract

Neuroimaging has improved our understanding of the evolution of stroke at discreet time points helping to identify irreversibly damaged and potentially reversible ischemic brain. Neuroimaging has also contributed considerably to the basic premise of acute stroke therapy which is to salvage some portion [...] Read more.

Neuroimaging has improved our understanding of the evolution of stroke at discreet time points helping to identify irreversibly damaged and potentially reversible ischemic brain. Neuroimaging has also contributed considerably to the basic premise of acute stroke therapy which is to salvage some portion of the ischemic region from evolving into infarction, and by doing so, maintaining brain function and improving outcome. The term neurovascular unit (NVU) broadens the concept of the ischemic penumbra by linking the microcirculation with neuronal-glial interactions during ischemia reperfusion. Strategies that attempt to preserve the individual components (endothelium, glia and neurons) of the NVU are unlikely to be helpful if blood flow is not fully restored to the microcirculation. Magnetic resonance imaging (MRI) is the foremost imaging technology able to bridge both basic science and the clinic via non-invasive real time high-resolution anatomical delineation of disease manifestations at the molecular and ionic level. Current MRI based technologies have focused on the mismatch between perfusion-weighted imaging (PWI) and diffusion weighted imaging (DWI) signals to estimate the tissue that could be saved if reperfusion was achieved. Future directions of MRI may focus on the discordance of recanalization and reperfusion, providing complimentary pathophysiological information to current compartmental paradigms of infarct core (DWI) and penumbra (PWI) with imaging information related to cerebral blood flow, BBB permeability, inflammation, and oedema formation in the early acute phase. In this review we outline advances in our understanding of stroke pathophysiology with imaging, transcending animal stroke models to human stroke, and describing the potential translation of MRI to image important interactions relevant to acute stroke at the interface of the neurovascular unit. Full article

(This article belongs to the Special Issue Magnetic Resonance Sensors)

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