Use of the Perturbing Sphere Method for the Estimation of Radiofrequency Coils' Efficiency in Magnetic Resonance Applications: Experience from an Electromagnetic Laboratory.

Radiofrequency (RF) transmitter and receiver coils are employed in in magnetic resonance (MR) applications to, respectively, excite the nuclei in the object to be imaged and to pick up the signals emitted by the nuclei with a high signal-to-noise ratio (SNR). The ability to obtain high-quality images and spectra in MR strongly depends on the RF coil's efficiency. Local coil efficiency can be estimated with magnetic field mapping methods evaluated at a fixed point in space.

MRI Application and Challenges of Hyperpolarized Carbon-13 Pyruvate in Translational and Clinical Cardiovascular Studies: A Literature Review.

Cardiovascular disease shows, or may even be caused by, changes in metabolism. Hyperpolarized magnetic resonance spectroscopy and imaging is a technique that could assess the role of different aspects of metabolism in heart disease, allowing real-time metabolic flux assessment in vivo. In this review, we introduce the main hyperpolarization techniques.

Hardware and Software Setup for Quantitative Na Magnetic Resonance Imaging at 3T: A Phantom Study.

Magnetic resonance (MR) with sodium (Na) is a noninvasive tool providing quantitative biochemical information regarding physiology, cellular metabolism, and viability, with the potential to extend MR beyond anatomical proton imaging. However, when using clinical scanners, the low detectable Na signal and the low Na gyromagnetic ratio require the design of dedicated radiofrequency (RF) coils tuned to the Na Larmor frequency and sequences, as well as the development of dedicated phantoms for testing the image quality, and an MR scanner with multinuclear spectroscopy (MNS) capabilities. In this work, we propose a hardware and software setup for evaluating the potential of Na magnetic resonance imaging (MRI) with a clinical scanner.

Dual-Channel Transverse Fields Radiofrequency Coils for 1.5 T Magnetic Resonance Imaging.

This theoretical study presents the design and analytical/numerical optimization of novel dual-channel transverse fields radiofrequency (RF) surface coils for 1.5 T Magnetic Resonance Imaging (MRI). The research explores a planar setup with two channels on a row with aligned spatial orientation of the RF coils, aiming to solve a common design drawback of single-channel transverse field RF coils: the reduced Field Of View (FOV) along the direction of the RF field.

Machine Learning for the Design and the Simulation of Radiofrequency Magnetic Resonance Coils: Literature Review, Challenges, and Perspectives.

Radiofrequency (RF) coils for magnetic resonance imaging (MRI) applications serve to generate RF fields to excite the nuclei in the sample (transmit coil) and to pick up the RF signals emitted by the nuclei (receive coil). For the purpose of optimizing the image quality, the performance of RF coils has to be maximized. In particular, the transmit coil has to provide a homogeneous RF magnetic field, while the receive coil has to provide the highest signal-to-noise ratio (SNR).

Magnetostatic Simulation and Design of Novel Radiofrequency Coils Based on Transverse Field Current Elements for Magnetic Resonance Applications.

Radiofrequency (RF) coils are key components in Magnetic Resonance (MR) systems and can be categorized into volume and surface coils according to their shapes. Volume RF coils can generate a uniform field in a large central sample's region, while surface RF coils, usually smaller than volume coils, typically have a higher Signal-to-Noise Ratio (SNR) in a reduced Region Of Interest (ROI) close to the coil plane but a relatively poorer field homogeneity. Circular and square loops are the simplest and most used design for developing axial field surface RF coils.

Conductor Losses in Radiofrequency Coils for Magnetic Resonance below 3T: Estimation Methods and Minimization Strategies.

The design of optimized radiofrequency (RF) coils is a fundamental task for maximizing the signal-to-noise ratio (SNR) in Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS) applications. An efficient coil should be designed by minimizing the coil noise with respect to the sample noise, since coil conductor resistance affects data quality by reducing the SNR, especially for coils tuned to a low frequency. Such conductor losses strongly depend on the frequency (due to the skin effect) and on the conductor cross-sectional shape (strip or wire).

Computer tomography and magnetic resonance for multimodal imaging of fossils and mummies.

The study of fossils and mummies has largely benefited from the use of modern noninvasive and nondestructive imaging technologies and represents a fast developing area. In this review, we describe the emerging role of imaging based on Magnetic Resonance (MR) and Computer Tomography (CT) employed for the study of ancient remains and mummies. For each methodology, the state of the art in paleoradiology applications is described, by emphasizing new technologies developed in the field of both CT, such as micro- and nano-CT, dual-energy and multi-energy CT, and MR, with the description of novel dedicated sequences, radiofrequency coils and gradients.

Shaping and Focusing Magnetic Field in the Human Body: State-of-the Art and Promising Technologies.

In recent years, the usage of radio frequency magnetic fields for biomedical applications has increased exponentially. Several diagnostic and therapeutic methodologies exploit this physical entity such as, for instance, magnetic resonance imaging, hyperthermia with magnetic nanoparticles and transcranial magnetic stimulation. Within this framework, the magnetic field focusing and shaping, at different depths inside the tissue, emerges as one of the most important challenges from a technological point of view, since it is highly desirable for improving the effectiveness of clinical methodologies.

Occupational exposure to electromagnetic fields in magnetic resonance environment: an update on regulation, exposure assessment techniques, health risk evaluation, and surveillance.

Magnetic resonance imaging (MRI) is one of the most-used diagnostic imaging methods worldwide. There are ∼50,000 MRI scanners worldwide each of which involves a minimum of five workers from different disciplines who spend their working days around MRI scanners. This review analyzes the state of the art of literature about the several aspects of the occupational exposure to electromagnetic fields (EMF) in MRI: regulations, literature studies on biological effects, and health surveillance are addressed here in detail, along with a summary of the main approaches for exposure assessment.

Design, simulation, and test of surface and volume radio frequency coils for C magnetic resonance imaging and spectroscopy.

Hyperpolarized C Magnetic Resonance (MR) is a promising technique for in vivo non-invasive assessment of metabolism in humans. Despite the considerable signal increase provided by hyperpolarization techniques, the low molar concentration of derivate C metabolites gives rise to technological limits in terms of data quality. The development of dedicated radio frequency coils, capable of providing a large field of view with high signal-to-noise ratio data, is thus a fundamental task.

Analysis, comparison and representation of occupational exposure to a static magnetic field in a 3-T MRI site.

The purpose of this study is to analyze exposure to the time-varying magnetic field caused by worker movements in a 3-T clinical magnetic resonance imaging (MRI) scanner. Measurements of the static magnetic field () in the proximity of the MRI scanner were performed to create a detailed map of the spatial gradient of , in order to indicate the areas at high risk of exposure. Moreover, a personal exposure recording system was used in order to analyze and compare exposure to the static magnetic field during different routine procedures in MRI.

Artifacts by Misalignment of Cardiac Magnetic Resonance Phased-array Coil Elements: From Simulation to In vivo Test.

Background: Cardiac magnetic resonance evaluations generally require a radiofrequency coil setup comprising a transmit whole-body coil and a receive coil. In particular, radiofrequency phased-array coils are employed to pick up the signals emitted by the nuclei with high signal-tonoise ratio and a large region of sensitivity.

Methods: Literature discussed different technical issues on how to minimize interactions between array elements and how to combine data from such elements to yield optimum Signal-to-Noise Ratio images.

The Procedure for Quantitative Characterization and Analysis of Magnetic Fields in Magnetic Resonance Sites for Protection of Workers: A Pilot Study.

Concerning the occupational exposure in magnetic resonance imaging (MRI) facilities, the worker behavior in the magnetic resonance (MR) room is of such particular importance that there is the need for a simple but reliable method to alert the worker of the highest magnetic field exposure. Here, we describe a quantitative analysis of occupational exposure in different MRI working environments: in particular, we present a field measurement method integrated with a software tool for an accurate mapping of the fringe field in the proximity of the magnetic resonance bore. Three illustrative assessment studies are finally presented, compared and discussed, considering an example of a realistic path followed by an MRI worker during the daily procedure.

TOWARDS A PERSONALISED AND INTERACTIVE ASSESSMENT OF OCCUPATIONAL EXPOSURE TO MAGNETIC FIELD DURING DAILY ROUTINE IN MAGNETIC RESONANCE.

Magnetic resonance imaging (MRI) is one of the most common sources of electromagnetic (EM) fields as a diagnostic technique widely used in medicine. MRI staff during the working day is constantly exposed to static and spatially heterogeneous magnetic field. Also, moving around the MRI room to perform their functions, workers are exposed to slowly time-varying magnetic fields that induce electrical currents and fields in the body.

Biomolecular imaging of C-butyrate with dissolution-DNP: Polarization enhancement and formulation for in vivo studies.

Magnetic Resonance Spectroscopy of hyperpolarized isotopically enriched molecules facilitates the non-invasive real-time investigation of in vivo tissue metabolism in the time-frame of a few minutes; this opens up a new avenue in the development of biomolecular probes. Dissolution Dynamic Nuclear Polarization is a hyperpolarization technique yielding a more than four orders of magnitude increase in the C polarization for in vivo Magnetic Resonance Spectroscopy studies. As reported in several studies, the dissolution Dynamic Nuclear Polarization polarization performance relies on the chemico-physical properties of the sample.

Radiofrequency magnetic resonance coils and communication antennas: Simulation and design strategies.

Coils simulation and design is a fundamental task to maximize Signal-to-Noise Ratio in Magnetic Resonance applications. In the meantime, in the last years the issue of accurate communication antennas analysis has grown. Coil design techniques take advantage of computer simulations in dependence on the magnetic field wavelength and coil sizes.

Radiofrequency Coils and Pulse Sequences for Cardiac Magnetic Resonance Applications: New Perspectives and Future Developments.

Cardiac magnetic resonance (CMR) is a relevant diagnostic tool for the evaluation of cardiac morphology, function, and mass. The assessment of myocardial tissue content through the measurement of longitudinal (T1) and transversal (T2) relaxation properties and the development of different technical advances are important clinical novelties of CMR. Recently, magnetic resonance spectroscopy has been explored for the assessment of the metabolic state of tissue for cardiac function evaluation by using nuclei other than protons, such as C and Na, expanding our knowledge of the kinetics of metabolic processes.

A radiofrequency system for in vivo hyperpolarized C MRS experiments in mice with a 3T MRI clinical scanner.

Hyperpolarized carbon-13 magnetic resonance spectroscopy (MRS) is a powerful tool to explore tissue metabolic state, by permitting the study of intermediary metabolism of biomolecules in vivo. However, a number of technological problems still limit this technology and need innovative solutions. In particular, the low molar concentration of derivate metabolites give rise to low signal-to-noise ratio (SNR), which makes the design and development of dedicated radiofrequency (RF) coils a fundamental task.

Magnetic resonance imaging for the study of mummies.

Nondestructive diagnostic imaging for mummies study has a long tradition and high-resolution images of the samples morphology have been extensively acquired by using computed tomography (CT). However, although in early reports no signal or image was obtained because of the low water content, mummy magnetic resonance imaging (MRI) was demonstrated able to generate images of such ancient specimens by using fast imaging techniques. Literature demonstrated the general feasibility of nonclinical MRI for visualizing historic human tissues, which is particularly interesting for archeology.

Magnetic resonance spectroscopy and imaging for the study of fossils.

Computed tomography (CT) has long been used for investigating palaeontological specimens, as it is a nondestructive technique which avoids the need to dissolve or ionize the fossil sample. However, magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) have recently gained ground as analytical tools for examination of palaeontological samples, by nondestructively providing information about the structure and composition of fossils. While MRI techniques are able to reveal the three-dimensional geometry of the trace fossil, MRS can provide information on the chemical composition of the samples.

Radiofrequency coils for magnetic resonance applications: theory, design, and evaluation.

Magnetic resonance imaging and magnetic resonance spectroscopy are noninvasive diagnostic techniques based on the phenomenon of nuclear magnetic resonance. Radiofrequency coils are key components in both the transmission and receiving phases of magnetic resonance systems. Transmitter coils have to produce a highly homogeneous alternating field in a wide field of view, whereas receiver coils have to maximize signal detection while minimizing noise.

Real-time cardiac metabolism assessed with hyperpolarized [1-(13) C]acetate in a large-animal model.

Dissolution-dynamic nuclear polarization (dissolution-DNP) for magnetic resonance (MR) spectroscopic imaging has recently emerged as a novel technique for noninvasive studies of the metabolic fate of biomolecules in vivo. Since acetate is the most abundant extra- and intracellular short-chain fatty acid, we focused on [1-(13) C]acetate as a promising candidate for a chemical probe to study the myocardial metabolism of a beating heart. The dissolution-DNP procedure of Na[1-(13) C]acetate for in vivo cardiac applications with a 3 T MR scanner was optimized in pigs during bolus injection of doses of up to 3 mmol.

Structured errors in reconstruction methods for Non-Cartesian MR data.

Background: Reconstruction methods for Non-Cartesian magnetic resonance imaging have often been analyzed using the root mean square error (RMSE). However, RMSE is not able to measure the level of structured error associated with the reconstruction process.

Methods: An index for geometric information loss was presented using the 2D autocorrelation function.