Nuclear Magnetic Resonance Imaging System Research Articles

Effect of long-term infiltration on porosity-permeability evolution in carbonate rocks: An online NMR coupling penetration test

Investigating the porosity–permeability evolution in carbonate rocks during long-term infiltration is a challenging hydrodynamic problem in rock engineering (hydroelectric engineering, CO2 geological storage, and oil/gas development). In general, we consider the evolution of porosity and permeability to be positively correlated. However, the complex pore structures in carbonate rocks include multiscale pore-fracture structures, such as intergranular pores, dissolution pores, and even fractures. Although the permeability levels of carbonate rocks are similar, the evolution of the pore structure is highly variable. Here, we use the “rock seepage coupled nuclear magnetic resonance (NMR) online analysis and imaging system” platform to conduct a long-term penetration test in carbonate rocks under the coupling of stress and reactive fluid. The variation in the multiscale pore volume was quantitatively characterized by the inversion of the T2 spectrum. Subsequently, in combination with permeability measurement, the permeability-porosity evolution during long-term infiltration can be roughly divided into three stages. The experimental results show that the evolution of permeability exhibits noticeable stress sensitivity at the initial stage of the test (0–156 h). Since the compression of the pore volume is the dominant mechanism, the permeability decreases with porosity at this stage. A negative correlation between the evolution of porosity and permeability was observed during the subsequent stage of the test (156–400 h). This phenomenon may be attributed to mineral dissolution at this stage, causing the cementation to be exfoliated from the pore surface and to re-precipitate at the pore throat, locally blocking the seepage channels. As the test continued (400–720 h), mineral dissolution transitioned from micropores to mesopores and macropores, with a synergistic increase in porosity and permeability. These results revealed the competing mechanism of stress compression and mineral dissolution during long-term infiltration, providing an accurate prediction of the seepage properties in carbonate rocks.

Sub-Nyquist Sampling of Multiple Exponentially Damped Sinusoids With Feedback Structure

Multiple exponentially damped sinusoids (MEDS) signals have been widely applied to the fields of speech analysis and nuclear magnetic resonance imaging systems. Although sub-Nyquist sampling schemes were proposed in previous works, either the image frequency aliasing was not resolved, or the parameters measuring process required a large number of samples. In this paper, a feedback based sub-Nyquist sampling and parameters measurement scheme for MEDS signals is proposed to address these problems. Since sub-Nyquist sampling would lead to frequencies ambiguity, an additional sampling is designed to determine the true frequencies. Moreover, image frequency aliasing would occur when the difference between two true frequencies is an integer multiple the sampling rate. To prevent image frequency aliasing, a feedback sampling strategy and a dealiasing algorithm are proposed. The proposed scheme enables sub-Nyquist sampling and parameters measurement of MEDS signals with K frequency components, by using only 4K samples. We also propose a hardware prototype to implement the proposed system. Simulation and hardware experiment results have shown that the frequency estimation accuracy of the proposed method has been improved on average by about 11.65 dB than previous works under noise environment, and the statistical variance experiments have shown that it has better stability.

Spatiotemporal imaging of redox status using in vivo dynamic nuclear polarization magnetic resonance imaging system for early monitoring of response to radiation treatment of tumor

In general, the effectiveness of radiation treatment is evaluated through the observation of morphological changes with computed tomography (CT) or magnetic resonance imaging (MRI) images after treatment. However, the evaluation of the treatment effects can be very time consuming, and thus can delay the verification of patient cases where treatment has not been fully effective. It is known that the treatment efficacy depends on redox modulation in tumor tissues, which is an indirect effect of oxidizing redox molecules such as hydroxyl radicals and of reactive oxygen species generated by radiation treatment. In vivo dynamic nuclear polarization-MRI (DNP-MRI) using carbamoyl-PROXYL (CmP) as a redox sensitive DNP probe enables the accurate monitoring of the anatomical distribution of free radicals based on interactions of electrons and nuclear spin, known as Overhauser effect. However, spatiotemporal response of the redox status in tumor tissues post-irradiation remains unknown. In this study, we demonstrate the usefulness of spatiotemporal redox status as an early imaging biomarker of tumor response after irradiation using in vivo DNP-MRI. Our results highlight that in vivo DNP-MRI/CmP allowed us to visualize the tumor redox status responses significantly faster and earlier compared to the verification of morphological changes observed with 1.5 T MRI and cancer metabolism (Warburg effect) obtained by hyperpolarized 13C pyruvate MRS. Our findings suggest that the early assessment of redox status alterations with in vivo DNP-MRI/CmP probe may provide very efficient information regarding the effectiveness of the subsequent radiation treatment.

1.5 T Nuclear Magnetic Resonance Imaging System Failure Treatment and Rectification Summary

Quench of magnetic resonance imaging system refers to the process that the superconducting condition inside the magnet is destroyed due to some reason. The large current stored in the coil is quickly converted into heat at the place where the resistance is formed, and a large amount of liquid helium in the magnet is evaporated. If it happens, it will cause huge loss to the user. We introduce the real cases of 1.5 T magnetic resonance imaging system's quench fault, maintenance treatment and management improvement, which can be used for reference by various medical institutions, so as to better strengthen the operation and maintenance management of magnetic resonance imaging system, so as to avoid the occurrence of out of tolerance fault, and do a good job in the guarantee work after the out of tolerance fault.

Parameters Measurement of Multiple Exponentially Damped Sinusoids With Sub-Nyquist Sampling

Measurement of parameters of multiple exponentially damped sinusoids (MEDS) signals is significant for nuclear magnetic resonance imaging and speech analysis systems. Traditional technologies require a large number of samples and heavy processing burden to estimate the parameters. In this brief, we propose a sub-Nyquist sampling and parameters estimation scheme for MEDS signals to address this problem. The proposed system consists of two parallel sampling channels, where the sampling clock of one channel is staggered with the other. The first sampling channel is used to estimate complex amplitudes, while the other is used to solve frequency ambiguity problem and determine the damping factors and pole frequencies. The proposed scheme enables parameters measurement of K components MEDS signals from as few as 3K samples, and it is also applicable to the scenario with unknown K. We also propose a hardware prototype to implement the proposed system. Simulation and experimental results demonstrate the effectiveness and noise robustness of the proposed scheme.

Analysis of hydration process of smelter slag plugging fluid activated with alkalis

The improper treatment of smelter slag is a prominent issue regarding environmental protection. To resolve this issue, we explored the possible application of a slag plugging fluid in the field of oil and gas field development. Specifically, the thermal effect during the hydration process, the microstructure, the water function mechanism, and the mechanical characteristics of a hardened body of the slag plugging fluid were investigated using a combination of characterization equipment including a hydration heat calorimeter, nuclear magnetic resonance (NMR) spectrometer, scanning electron microscope, NMR crosslink density meter, and medium-sized NMR analysis and imaging system. The results of this study show that the degree of polymerization of Si increases during the hydration process, accompanied by the generation of a large amount of 6-coordinated Al. At the same time, the spacing between particles is reduced by the physical and chemical reactions in the hydration product formed through the hydration reaction of the slag. This behavior causes the slurry to cement and harden. During the hardening process of the slurry, the water binding force, the water form, and the pore structure are all affected and changed by the components in the slurry. These combined effects further cause the T2 spectrum curve of water to change during the hydration process. Finally, a hardened slurry can form a slug that effectively seals the leaking channel. The theoretical results obtained from this study can help guide the recycling utilization of slag in the area of oil and gas field development. Such a direction will provide an effective means of resolving the slag treatment issue.

Serelaxin (recombinant human relaxin-2) treatment affects the endogenous synthesis of long chain poly-unsaturated fatty acids and induces substantial alterations of lipidome and metabolome profiles in rat cardiac tissue

Background and Purpose: Recombinant human relaxin-2, serelaxin, is being proved as a novel drug with therapeutic efficacy in some cardiovascular diseases, especially heart failure, a disease whose physiopathology and course are firmly correlated with important alterations in cardiac metabolism. The aim of our present work was to investigate changes in the cardiac metabolome following relaxin-2 treatment.Experimental Approach: Sprague-Dawley rats were treated with human recombinant relaxin-2 using osmotic minipumps at a dose of 0.4 mg/kg/day for 2 weeks. Body composition was measured with a nuclear magnetic resonance imaging system seven days after surgery and on the final day of the experiment. The last two days of treatment, respiratory quotient, locomotor activity and energy expenditure were measured with a calorimetric system. The plasma levels of relaxin-2, total cholesterol, high- and low- density lipoproteins (HDL, LDL), triglycerides and the hepatic enzymes glutamic-pyruvic transaminase (GTP) and gamma-glutamyltransferase (GGT) levels were analyzed. The metabolic profiling of both atria from relaxin-2-treated and control rats was carried out using two separate ultra-high performance liquid chromatography (UHPLC)-Time of Flight-MS based platforms analyzing methanol and chloroform/methanol extracts combined with a UHPLC-single quadrupole-MS based platform used to analyze aminoacids and with a methanol/water extract platform that covered polar metabolites. Identified ion features in the methanol extract platform included fatty acids, acyl carnitines, bile acids, monoacylglycerophospholipids, monoetherglycerophospholipids, free sphingoid bases, and oxidized fatty acids. The chloroform / methanol extract platform provided coverage over glycerolipids, cholesterol esters, sphingolipids, diacylglycerophospholipids, and acyl-ether-glycerophospholipids. Gene expression levels of the adipokines adiponectin, leptin and nesfatin-1 in visceral adipose tissue and cardiac gene expression levels of key enzymes of desaturation and elongation of n-6 and n-3 PUFAs were assessed by Real Time-PCR.Key Results: Twenty-eight metabolites out of three hundred sixty-two were significantly altered by human relaxin-2. These included fifteen glycerophospholipids: three phosphatidylethanolamines (PE) and twelve phosphatidylcholines (PC); eight sphingolipids: three ceramides (Cer) and five sphingomyelins (SM); and also five aminoacids and one carboxylic acid. Interestingly, the majority of changes correspond to lipid classes, twelve of them polyunsaturated diacylglycerophosphatidylcholines with long acyl chains, containing mainly docosahexaenoic acid (22:6) and arachidonic acid (20:4). Atrial levels of Elovl5 (Elongation of very long chain fatty acids protein 5), Fads1 (Δ5-fatty acid desaturase) and Fads2 (Δ6-fatty acid desaturase), key enzymes of elongation and desaturation of n-6 and n-3 PUFAs like arachidonic acid and DHA, respectively, were significantly increased by relaxin-2 treatment. Atrial tissues from rats treated with relaxin-2 showed a significant increase in the mRNA levels of Srebf1, a transcription factor that activates the gene expression of Elovl5, Fads1 and Fads2.The treatment with relaxin-2 significantly decreased the visceral fat mRNA expression levels of adiponectin, leptin and nesfatin-1, adipokines known to exert an important influence on the regulation of cardiovascular function.Conclusion and Implications: Serelaxin (human recombinant relaxin-2) treatment induces significant changes in cardiac major components of the membrane lipid bilayer such as glycerophospholipids and sphingolipids, known to have structural roles but also very relevant regulatory effects in cardiac function. Serelaxin induced also modifications in several aminoacids of high influence in cardiac energy metabolism regulation. Our results highlight the need to further understand the role of relaxin-2 in the regulation of cardiac energy metabolism, in the context of the therapeutic strategies for the treatment of cardiometabolic pathologies as heart failure.

A simple protection evaluation method for no-insulation REBCO pancake coils during local normal-state transition

No-insulation (NI) and metal-insulation (MI) winding techniques are promising for enhancing the thermal stability of REBCO pancake coils, toward the practical use of nuclear magnetic resonance and magnetic resonance imaging systems. The NI and MI REBCO pancake coils showed high thermal stability in many over-current tests. However, a disadvantage is a charging delay due to low turn-to-turn contact resistance. Therefore, many researchers have tried to increase turn-to-turn contact resistance to overcome the charging delay problem. Meanwhile, a partial element equivalent circuit (PEEC) model can accurately simulate the over-current and charging/discharging tests of NI REBCO pancake coils in detail. Using the PEEC model coupling with thermal finite element analysis (FEA), the thermal stability was evaluated during a local normal-state transition. From the simulation results, it was found that a best range of turn-to-turn contact resistance existed to keep a high thermal stability during a local normal-state transition. However, the PEEC and thermal FEA method requires a substantial amount of time with complicated simulation approach. In this paper, we propose a simple mathematical formulation to obtain an appropriate range of turn-to-turn contact resistance during a local normal-state transition, supposing a worst cooling condition. The simple computation is easy to use and timesaving to roughly estimate the operation reliability of NI REBCO pancake coils.

Variable Temperature Nuclear Magnetic Resonance and Magnetic Resonance Imaging System as a Novel Technique for In Situ Monitoring of Food Phase Transition

A nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system with a 45 mm variable temperature (VT) sample probe (VT-NMR-MRI) was developed as an innovative technique for in situ monitoring of food phase transition. The system was designed to allow for dual deployment in either a freezing (-37 °C) or high temperature (150 °C) environment. The major breakthrough of the developed VT-NMR-MRI system is that it is able to measure the water states simultaneously in situ during food processing. The performance of the VT-NMR-MRI system was evaluated by measuring the phase transition for salmon flesh and hen egg samples. The NMR relaxometry results demonstrated that the freezing point of salmon flesh was -8.08 °C, and the salmon flesh denaturation temperature was 42.16 °C. The protein denaturation of egg was 70.61 °C, and the protein denaturation occurred at 24.12 min. Meanwhile, the use of MRI in phase transition of food was also investigated to gain internal structural information. All these results showed that the VT-NMR-MRI system provided an effective means for in situ monitoring of phase transition in food processing.

Damage Characteristics of Sandstone Subjected to Coupled Effect of Freezing‐Thawing Cycles and Acid Environment

In order to figure out the damage characteristics and mechanisms of sandstone under coupled effect of acid erosion and recurrent freezing‐thawing cycles, sulfuric acid is chosen as acid solution, and sandstone, representative stone in Sichuan province, is chosen as a sample to conduct the freezing‐thawing cycling test. In the meantime, chemical component of the solution is also tested and recorded in the progress of freezing‐thawing cycling. Then, the nuclear magnetic resonance (NMR) test and magnetic resonance images (MRI) test on samples are conducted with the help of the AniMR‐150 NMR imaging system. After a series of tests, the sample’s appearance, dry mass, porosity, T2 spectrum, solution’s pH, solution’s metallic ion concentration, and magnetic resonance images are obtained and analyzed. The results show that dry mass loss and porosity grow with F‐T cycles increase and pH value decrease. Montmorillonite, illite, and clay in sandstone react with sulfuric acid solution; as a consequence, K+, Mg2+, Fe3+, and Al3+ separate out, and the solution’s pH and concentration of K+, Mg2+, Fe3+, and Al3+ increase with F‐T cycles. Acid erosion and F‐T cycling lead to the generation of new micropores and expansion of micropores at the beginning; when the acid solution is exhausted, new micropores generate under the effect of freezing‐thawing cycling, and micropores in samples keep developing and expanding with the increase of freezing‐thawing cycles. Coupled effect of acid corrosion and recurrent freezing‐thawing cycling causes much more serious deterioration to sandstone samples than acid corrosion.

Active shimming method for a 21.3 MHz small-animal MRI magnet

In a 21.3 MHz animal nuclear magnetic resonance (NMR) analyzer and imaging system, high uniformity of the static field B0 is a crucial prerequisite for obtaining high-quality images and detecting weak signals with short relaxation time. Using only passive shimming and gradient shimming, it is impossible to achieve perfect B0 uniformity. This paper presents an approach involving high-order active shimming for an NMR analyzer and an imaging magnet. The diameter spherical volume (DSV) of the magnet is only 60 mm. The spherical harmonic function is introduced to analyze the magnetic field and provide a foundation for active shimming. Eleven pairs of bi-planar active shim coils (X, Y, Z, XZ, YZ, Z2, X2 + Y2, X2 − Y2, Z3, Z4, Z5) were designed using the target field-and stream-function methods, and coils were manufactured with printed circuit board technology in this research. The magnetic field created by these electrified shim coils compensates effectively and accurately for the static magnetic field B0. The full width at half maximum of the resonance spectrum was used to measure the shimming effect. The results of practical shimming experiments in a 21.3 MHz animal NMR analyzer and imaging device showed that this new approach helps to reduce inhomogeneity from 24 ppm (24 × 10−6) to 0.39 ppm (0.39 × 10−6) over a 60 mm DSV, which meets the requirements of imaging and analytical practice.

Hyperpolarized 13C Metabolic Magnetic Resonance Spectroscopy and Imaging.

In the past decades, new methods for tumor staging, restaging, treatment response monitoring, and recurrence detection of a variety of cancers have emerged in conjunction with the state-of-the-art positron emission tomography with 18F-fluorodeoxyglucose ([18F]-FDG PET). 13C magnetic resonance spectroscopic imaging (13CMRSI) is a minimally invasive imaging method that enables the monitoring of metabolism in vivo and in real time. As with any other method based on 13C nuclear magnetic resonance (NMR), it faces the challenge of low thermal polarization and a subsequent low signal-to-noise ratio due to the relatively low gyromagnetic ratio of 13C and its low natural abundance in biological samples. By overcoming these limitations, dynamic nuclear polarization (DNP) with subsequent sample dissolution has recently enabled commonly used NMR and magnetic resonance imaging (MRI) systems to measure, study, and image key metabolic pathways in various biological systems. A particularly interesting and promising molecule used in 13CMRSI is [1-13C]pyruvate, which, in the last ten years, has been widely used for in vitro, preclinical, and, more recently, clinical studies to investigate the cellular energy metabolism in cancer and other diseases. In this article, we outline the technique of dissolution DNP using a 3.35 T preclinical DNP hyperpolarizer and demonstrate its usage in in vitro studies. A similar protocol for hyperpolarization may be applied for the most part in in vivo studies as well. To do so, we used lactate dehydrogenase (LDH) and catalyzed the metabolic reaction of [1-13C]pyruvate to [1-13C]lactate in a prostate carcinoma cell line, PC3, in vitro using 13CMRSI.

Microtesla NMR and High Resolution MR Imaging Using High-$T_{\rm c}$ SQUIDs

In this work, we set up a low-cost high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> SQUID-based low-field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system without μ-metal. In order to reduce the surrounding noise, we built the shielded box and shielded cylinder made out of aluminum. For NMR and MRI measurements, we apply the gradient compensation field to cancel the field inhomogeneity in our lab to obtain a narrow linewidth NMR spectrum of 0.8 Hz from a 10-ml water specimen. In the absence of chemical shifts, the J-couplings of trimethyl phosphate and trifluoroethanol are demonstrated in trials of the proposed scheme. Furthermore, the 2-D images of water specimen and mini tomato with high-image resolution of better than 2 mm are obtained by using our low-field MRI system. Our high- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> SQUID-based low-field MRI system promises a low-cost and high imaging quality in microtesla magnetic fields.

Feasibility study of contaminant detection for food with ULF-NMR/MRI system using HTS-SQUID

We have developed an ultra-low frequency (ULF) nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system utilizing an HTS-SQUID for an application of contaminant detection in food and drink. In the system, a permanent magnet of 1.1T was used to pre-polarize protons in a water sample. We measured NMR signals from water samples with or without various contaminants, such as stainless steel (SUS304), aluminum, and glass balls using the system. In the case that the contaminant was the SUS304 ball, the NMR signal intensity was reduced compared to that from the sample without the contaminant due to the remnant field of the contaminant. One-dimensional (1D) MRIs of the samples were also acquired to detect non-magnetic contaminants. In the 1D MRIs, changes of the MRI spectra were detected, corresponding to positions of the contaminants. These results show that the feasibility of the system to detect various contaminants in foods.

Patterning of Spiral Structure on Optical Fiber by Focused-Ion-Beam Etching

We produce patterns on minute and curved surfaces of optical fibers, and develop a processing technology for fabricating sensors, antennas, electrical circuits, and other devices on such patterned surfaces by metallization. A three-dimensional processing technology can be used to fabricate a spiral coil on the surface of cylindrical quartz materials, and then the microcoils can also be applied to capillaries of micro-fluid devices, as well as to receiver coils connected to a catheter and an endoscope of nuclear magnetic resonance imaging (MRI) systems used in imaging blood vessels. To create a spiral line pattern with a small linewidth on a full-circumference surface of an optical fiber, focused-ion-beam (FIB) etching was employed. Here, a simple rotation stage comprising a dc motor and an LR3 battery was built. However, during the development of a prototype rotation stage before finalizing a large-scale remodelling of our FIB etching system, a technical problem was encountered where a spiral line could not be processed without running into breaks and notches in the features. It turned out that the problem was caused by axis blur resulting from an eccentric spinning (or wobbling) of the axis of the fiber caused by its unrestrained free end. The problem was solved by installing a rotation guide and an axis suppression device onto the rotation stage. Using this improved rotation stage. we succeeded in the seamless patterning of 1-µm-wide features on the full-circumference surface of a 250-µm-diameter quartz optical fiber (QOF) by FIB etching.

A transportable magnetic resonance imaging system for in situ measurements of living trees: The Tree Hugger

This paper presents the design of the ‘Tree Hugger’, an open access, transportable, 1.1MHz 1H nuclear magnetic resonance imaging system for the in situ analysis of living trees in the forest. A unique construction employing NdFeB blocks embedded in a reinforced carbon fibre frame is used to achieve access up to 210mm and to allow the magnet to be transported. The magnet weighs 55kg. The feasibility of imaging living trees in situ using the ‘Tree Hugger’ is demonstrated. Correlations are drawn between NMR/MRI measurements and other indicators such as relative humidity, soil moisture and net solar radiation.

Development of Ultra Low Field Nuclear Magnetic Resonance Imaging System Using HTS rf SQUID

We constructed and studied an ultra low-field nuclear magnetic resonance imaging system using a HTS rf SQUID and room-temperature coils. We recorded the free induction decay signals of 1H by employing a measuring field, Bm, of 44.8 μT and a polarizing field, Bp, of 36.8 mT; in the presence of ∂BZ/∂z and ∂BZ/∂y gradients of the order of 0.8 μT/m, we were able to obtain a quasi two-dimensional 4-pixels image of a simple water phantom.

Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design

Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum in a cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable ldquosensitive volumes.rdquo

Development of Birdcage Resonators for the 3 Tesla NMR Imaging System

An optimized birdcage resonator configuration with a low-pass filter was designed and built to facilitate the acquisition of high-resolution three-dimensional images of small animals on the 3 T nuclear magnetic resonance imaging system. The birdcage resonator had a 12-element structure in order to ensure B 1 homogeneity over the image volume and for obtaining the maximum filling factor. The quality of the manufactured birdcage resonators was evaluated on the basis of the return loss following the matching and tuning process. The experimental magnetic resonance images of the phantoms were obtained by the various manufactured birdcage resonators to compare the signal-to-noise ratio (SNR) in accordance with the size of the objects. The ratio of the size of an object to the size of the coil was identified by the parameters that were estimated from the images of a phantom. This study demonstrated that the SNR could be different depending on the size of the object even if birdcage resonators have the same cylindrical forms.

ODIN—Object-oriented Development Interface for NMR

A cross-platform development environment for nuclear magnetic resonance (NMR) experiments is presented. It allows rapid prototyping of new pulse sequences and provides a common programming interface for different system types. With this object-oriented interface implemented in C++, the programmer is capable of writing applications to control an experiment that can be executed on different measurement devices, even from different manufacturers, without the need to modify the source code. Due to the clear design of the software, new pulse sequences can be created, tested, and executed within a short time. To post-process the acquired data, an interface to well-known numerical libraries is part of the framework. This allows a transparent integration of the data processing instructions into the measurement module. The software focuses mainly on NMR imaging, but can also be used with limitations for spectroscopic experiments. To demonstrate the capabilities of the framework, results of the same experiment, carried out on two NMR imaging systems from different manufacturers are shown and compared with the results of a simulation.