Dehydration assessment via a portable, single sided magnetic resonance sensor

Bashyam, Ashvin; Frangieh, Chris J.; Li, Matthew; Cima, Michael J.

doi:10.1002/mrm.28004

Cited by 16 publications

(11 citation statements)

References 77 publications

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“…There are two broad classes of optimization target fields: one which consists of a linear static magnetic field gradient perpendicular to the surface of the magnet [ 28 , 32 , 33 , 35 , 41 , 45 , 49 ] or a localized ‘sweet spot’ consisting of a ROI in which the magnetic field is relatively homogeneous in all three dimensions [ 29 , 30 , 34 , 42 , 43 , 48 , 50 ]. In the next section we will use the EA model we developed to find an optimized magnet design solution by varying the relative positions of the individual permanent cubic magnets.…”

Section: Magnet Array Designmentioning

confidence: 99%

Deep neural-network based optimization for the design of a multi-element surface magnet for MRI applications

2022

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We present a combination of a CNN-based encoder with an analytical forward map for solving inverse problems. We call it an encoder-analytic (EA) hybrid model. It does not require a dedicated training dataset and can train itself from the connected forward map in a direct learning fashion. A separate regularization term is not required either, since the forward map also acts as a regularizer. As it is not a generalization model it does not suffer from overfitting. We further show that the model can be customized to either finding a specific target solution or one that follows a given heuristic. As an example, we apply this approach to the design of a multi-element surface magnet for low-field magnetic resonance imaging (MRI). We further show that the EA model can outperform the benchmark genetic algorithm model currently used for magnet design in MRI, obtaining almost 10 times better results.

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Section: Magnet Array Designmentioning

confidence: 99%

Deep neural-network based optimization for the design of a multi-element surface magnet for MRI applications

2022

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“…The barrel magnet design uses the combination of two magnets to create a "sweet spot" of field strength and homogeneity at distances on the order of 30 mm from the surface of the magnet [115]. Halbach arrays have been used both to provide the typical bilateral B 0 in portable form factors (i.e., the "NMR-Cuff") [116] and have recently been employed in unilateral designs [117,118] .…”

Section: How Far Is Everywhere? Examples From Low-field Nmrmentioning

confidence: 99%

EPR Everywhere

Biller

McPeak

2021

Appl Magn Reson

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This review is inspired by the contributions from the University of Denver group to low-field EPR, in honor of Professor Gareth Eaton's 80th birthday. The goal is to capture the spirit of innovation behind the body of work, especially as it pertains to development of new EPR techniques. The spirit of the DU EPR laboratory is one that never sought to limit what an EPR experiment could be, or how it could be applied. The most well-known example of this is the development and recent commercialization of rapid-scan EPR. Both of the Eatons have made it a point to remain knowledgeable on the newest developments in electronics and instrument design. To that end, our review touches on the use of miniaturized electronics and applications of single-board spectrometers based on software-defined radio (SDR) implementations and single-chip voltage-controlled oscillator (VCO) arrays. We also highlight several non-traditional approaches to the EPR experiment such as an EPR spectrometer with a "wand" form factor for analysis of the OxyChip, the EPR-MOUSE which enables non-destructive in situ analysis of many non-conforming samples, and interferometric EPR and frequency swept EPR as alternatives to classical high Q resonant structures.

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“…Magnetic resonance systems that operate at lower fields than conventional scanners have been developed to achieve this goal [3,4]. MRI contrast mechanisms have also been applied in portable low field MR relaxometry devices, which may unlock new uses of magnetic resonance for point of care diagnosis and monitoring [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Oxygen saturation-dependent effects on blood transverse relaxation at low fields

Thomas

Galvosas

Tzeng

et al. 2022

Magn Reson Mater Phy

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Objective Blood oxygenation can be measured using magnetic resonance using the paramagnetic effect of deoxy-haemoglobin, which decreases the $$\textit{T}_{2}$$ T 2 relaxation time of blood. This $$\textit{T}_{2}$$ T 2 contrast has been well characterised at the $$\textit{B}_{{0}}$$ B 0 fields used in MRI (1.5 T and above). However, few studies have characterised this effect at lower magnetic fields. Here, the feasibility of blood oximetry at low field based on $$\textit{T}_{2}$$ T 2 changes that are within a physiological relevant range is explored. This study could be used for specifying requirements for construction of a monitoring device based on low field permanent magnet systems. Methods A continuous flow circuit was used to control parameters such as oxygen saturation and temperature in a sample of blood. It flowed through a variable field magnet, where CPMG experiments were performed to measure its $$\textit{T}_{2}$$ T 2 . In addition, the oxygen saturation was monitored by an optical sensor for comparison with the $$\textit{T}_{2}$$ T 2 changes. Results These results show that at low $$\textit{B}_{{0}}$$ B 0 fields, the change in blood $$\textit{T}_{2}$$ T 2 due to oxygenation is small, but still detectable. The data measured at low fields are also in agreement with theoretical models for the oxy-deoxy $$\textit{T}_{2}$$ T 2 effect. Conclusion $$\textit{T}_{2}$$ T 2 changes in blood due to oxygenation were observed at fields as low as 0.1 T. These results suggest that low field NMR relaxometry devices around 0.3 T could be designed to detect changes in blood oxygenation.

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Dehydration assessment via a portable, single sided magnetic resonance sensor

Cited by 16 publications

References 77 publications

Deep neural-network based optimization for the design of a multi-element surface magnet for MRI applications

Deep neural-network based optimization for the design of a multi-element surface magnet for MRI applications

EPR Everywhere

Oxygen saturation-dependent effects on blood transverse relaxation at low fields

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