Magnetic properties characterized by susceptibility and chemical shift linearly modify the local magnetic field experienced spins. A piece-wise constant solution using resonance imaging is found to challenging inversion problem from properties. The shifts were estimated MR phase images. magnitude images segmented into many regions of uniform Standard linear regression calculated each region allowed accurate quantification. technique was experimentally validated on a variety samples including...

Boys with X-linked hypohidrotic ectodermal dysplasia and their families were studied. Many suffered severe illness in early childhood nearly 30% died; many had feeding problems, fever, atopic disease, recurrent respiratory infections. Some infants failed to thrive. We found no consistent common endocrine or immunological abnormality, although, most abnormal immunoglobulin production. This may be related the mucosa of gastrointestinal tracts which exacerbates chronic obstructive airways...

In this work, a generic recipe for an inexpensive and nontoxic phantom was developed within range of biologically relevant dielectric properties from 150 MHz to 4.5 GHz.

To determine the feasibility of using finite element analysis applied to 3-T magnetic resonance (MR) images proximal femur microarchitecture for detection lower bone strength in subjects with fragility fractures compared control without fractures.This prospective study was institutional review board approved and HIPAA compliant. Written informed consent obtained. Postmenopausal women (n = 22) were matched age body mass index. All underwent standard dual-energy x-ray absorptiometry. Images...

In high field MRI, the spatial distribution of radiofrequency magnetic ( B1) is usually affected by presence sample. For hardware design and to aid interpretation experimental results, it important both anticipate accurately simulate behavior these fields. Fields generated a surface coil were simulated using dyadic Green's functions, or experimentally measured over range frequencies inside an object whose electrical properties varied illustrate variety transmit [Formula: see text] receive...

In vivo sodium magnetic resonance imaging (MRI) measures tissue content in living human brain but current methods do not allow noninvasive quantitative assessment of intracellular concentration (ISC) – the most useful marker viability. this study, we report first measurement ISC and volume fraction (ISVF) healthy brain, made possible by measuring (TSC) molar (ISMF) at ultra‐high field MRI. The method uses single–quantum (SQ) triple–quantum filtered (TQF) 7 Tesla to separate intra‐...

Purpose Previous work with body‐size objects suggested that loops are optimal MR detectors at low fields, whereas electric dipoles required to maximize signal‐to‐noise ratio (SNR) ultrahigh fields ( ≥ 7 T). Here we investigated how many and/or needed approach the ultimate intrinsic SNR (UISNR) various field strengths. Methods We calculated UISNR inside dielectric cylinders mimicking different anatomical regions. assessed performance of arrays respect UISNR. validated our results by comparing...

Purpose To explore the use of polyvinylpyrrolidone (PVP) for simulated materials with tissue‐equivalent dielectric properties. Methods PVP and salt were used to control, respectively, relative permittivity electrical conductivity in a collection 63 samples range solute concentrations. Their properties measured commercial probe fitted 3D polynomial order establish an empirical recipe. The material's thermal MR spectra measured. Results recipe (available at...

For pharmacokinetic modeling of tissue physiology, there is great interest in measuring the arterial input function (AIF) from dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) using paramagnetic contrast agents. Due to relaxation effects, measured signal a nonlinear injected agent concentration and depends on sequence parameters, system calibration, time-of-flight making it difficult accurately measure AIF during first pass. Paramagnetic agents also affect susceptibility...

Abstract The markedly increased degrees of freedom introduced by parallel radiofrequency transmission presents both opportunities and challenges for specific absorption rate (SAR) management. On one hand they enable E‐field tailoring SAR reduction while facilitating excitation profile control. other increase the complexity behavior risk inadvertently exacerbating improper design or playout pulses. substantial subject‐dependency in high field magnetic resonance can be a compounding factor....

Abstract The critical design aim for a sodium/proton coil is to maximize sodium sensitivity and transmit field homogeneity while simultaneously providing adequate proton homogeneity. While most dual‐frequency coils use lossy high‐impedance trap circuits or PIN diodes allow dual‐resonance, we explored nested‐coil knee imaging at 7 T. A stand‐alone eight‐channel receive array was implemented without standard dual‐resonance circuitry provide improved signal‐to‐noise ratio. detunable birdcage...

Purpose To demonstrate the feasibility of performing bone microarchitecture, high-resolution cartilage, and clinical imaging hip at 7T. Materials Methods This study had Institutional Review Board approval. Using an 8-channel coil constructed in-house, we imaged hips 15 subjects on a 7T magnetic resonance (MRI) scanner. We applied: 1) T1-weighted 3D fast low angle shot (3D FLASH) sequence (0.23 × 0.23 1–1.5 mm3) for microarchitecture imaging; 2) FLASH (water excitation) volumetric...

Purpose To demonstrate that strategic use of materials with high electric permittivity along integrated head‐sized coil arrays can improve SNR in the entire brain. Methods Numerical simulations were used to design a high‐permittivity material (HPM) helmet for enhancing throughout brain receive 8 and 28 channels. Then, two 30‐channel head coils identical geometry constructed: one fitted prototype helmet‐shaped ceramic HPM helmet, second low‐permittivity shell, each 8‐mm thick. An...

Purpose High‐resolution imaging of deeper anatomy such as the hip is challenging due to low signal‐to‐noise ratio (SNR), necessitating long scan times. Multi‐element coils can increase SNR and reduce time through parallel (PI). We assessed feasibility using a 26‐element receive coil setup perform 3 Tesla (T) MRI proximal femur microarchitecture without with PI. Materials Methods This study had institutional review board approval. scanned 13 subjects on 3T scanner 26 receive‐elements...

Purpose We describe a 2 × 6 channel sodium/proton array for knee MRI at 3T. Multielement coil arrays are desirable because of well‐known signal‐to‐noise ratio advantages over volume and single‐element coils. However, low tissue–coil coupling that is characteristic coils operating frequency can make the potential gains from phased difficult to realize. Methods The issue in developed six‐channel sodium receive was addressed by implementing 1) mechanically flexible former minimize...

Purpose Introduce a novel coil design using an electrically long transversely oriented slot in conductive sheet. Theory and Methods Theoretical considerations, numerical simulations, experimental measurements are presented for transverse antennas as compared with electric dipole antennas. Results Simulations show improved central average transmit receive efficiency, well larger coverage the plane, single to element. Experiments on body phantom confirm simulation results antenna relative...

ABSTRACT Electromagnetic field simulations are increasingly used to assure RF safety of patients during MRI exams. In practice, however, tissue property distribution the patient being imaged is not known, but may be represented with a pre‐existing model. Repeatedly, agreement in transmit magnetic ( ) distributions between two geometries has been suggest heating distributions. Here we examine relative effects anatomical differences on distribution, specific absorption rate (SAR), and...

Purpose . To revisit the “loopole,” an unusual coil topology whose unbalanced current distribution captures both loop and electric dipole properties, which can be advantageous in ultra-high-field MRI. Methods Loopole coils were built by deliberately breaking capacitor symmetry of traditional coils. The corresponding distribution, transmit efficiency, signal-to-noise ratio (SNR) evaluated simulation experiments comparison to those loops dipoles at 7 T (297 MHz). Results loopole exhibited a...

Flexible radiofrequency coils for magnetic resonance imaging (MRI) have garnered attention in research and industrial communities because they provide improved accessibility performance can accommodate a range of anatomic postures. Most recent flexible coil developments involve customized conductors or substrate materials and/or target applications at 3 T above. In contrast, we set out to design based on an off-the-shelf conductor that is suitable operation 0.55 (23.55 MHz). Signal-to-noise...

The capture of highly accurate data describing the complex surfaces human body may prove extremely useful in many medical situations. provide a method measuring and recording changes to surface patient's soft tissue. be applied computer-controlled manufacturing techniques, such as rapid prototyping (RP). This enables physical replicas patient topography produced. Such models used an aid design manufacture prostheses. paper describes investigation aimed at identifying problems that...

Abstract Radiofrequency shimming with multiple channel excitation has been proposed to increase the transverse magnetic field uniformity and reduce specific absorption rate at high strengths (≥7 T) where high‐frequency effects can make traditional single volume coils unsuitable for transmission. In case of deep anatomic regions power‐demanding pulse sequences, optimization transmit efficiency may be a more critical requirement than homogeneity per se. This work introduces novel method...

The purpose of this work was to develop a novel method disentangle the intra- and extracellular components total sodium concentration (TSC) in breast cancer from combination proton ([Formula: see text]H) text]) magnetic resonance imaging (MRI) measurements. To do so, TSC is expressed as function intracellular text]), volume fraction (ECV) water (WF) based on three-compartment model tissue. measured [Formula: text] MRI, ECV calculated baseline post-contrast text]H maps, while WF with chemical...

The pathological cascade of tissue damage in mild traumatic brain injury is set forth by a perturbation ionic homeostasis. However, whether this class can be detected vivo and serve as surrogate marker clinical outcome unknown. We employ sodium MRI to test the hypotheses that regional global total concentrations: (i) are higher patients than controls (ii) correlate with presentation neuropsychological function. Given novelty imaging injury, effect sizes from (i), correlation types strength...