A truncated twisted solenoid RF phase gradient transmit coil for TRASE MRI.

Transmit array spatial encoding (TRASE) is an MR imaging technique that achieves k-space encoding through the use of phase gradients in the RF transmit field. Without requiring B gradient fields, TRASE MRI can be performed using significantly cheaper bi-planar permanent magnets or Halbach arrays. For TRASE encoding with these magnets, the twisted solenoid has been demonstrated as the most efficient RF transmit coil; however, this specific geometry results in a long coil with a relatively short imaging volume.

The effects of coupled B fields in B encoded TRASE MRI - A simulation study.

Transmit Array Spatial Encoding (TRASE) is a novel MRI technique that encodes spatial information by introducing phase gradients in the transmit RF (B) magnetic field. Since TRASE relies on the use of multiple RF fields (B fields with different phase gradients) for k-space traversal, a TRASE pulse sequence requires RF pulses that are produced by switching between the transmit coils (B fields). However, interactions among the transmit RF coils can cause un-driven coils to produce unwanted B fields that impair the spatial encoding.

A geometrically decoupled, twisted solenoid single-axis gradient coil set for TRASE.

Purpose: TRASE uses phase gradients in the RF transmit field to encode MRI data. A highly efficient twisted solenoid coil was proposed recently for TRASE imaging for transverse geometries. This novel coil can be rotated to generate a phase gradient in any transverse direction, therefore, combining two such coils would double k-space coverage for single-axis encoding, resulting in higher spatial resolution.

TRASE 1D sequence performance in imperfect B fields.

Transmit Array Spatial Encoding (TRASE) is an MRI technique that uses radio-frequency (RF) magnetic field (B) phase gradients for spatial encoding. A TRASE pulse sequence consists of a long echo train in which each echo samples a different k-space point. Due to the need for accurate refocusing, TRASE imaging performance depends on |B| homogeneity.

A high duty-cycle, multi-channel, power amplifier for high-resolution radiofrequency encoded magnetic resonance imaging.

Objective: A radiofrequency (RF) power amplifier is an essential component of any magnetic resonance imaging (MRI) system. Unfortunately, no commercial amplifier exists to fulfill the needs of the transmit array spatial encoding (TRASE) MRI technique, requiring high duty cycle, high RF output power and independently controlled multi-channel capability. Thus, an RF amplifier for TRASE MRI is needed.

Design, Development, and Content Creation for an Open Education Physics Website for MRT Education.

Background: As health care technologies continue to advance rapidly, resulting in improved standards of practice, it is essential for health care professionals to continually expand on their current skills and knowledge. We describe here an initiative to use open education resources to provide ongoing education in radiation medical sciences and imaging.

Aims: The aim of this study to design an interactive, engaging, multilevel radiation medical physics resource, which is fully open to the public, and functional on all types of computing devices.

The twisted solenoid RF phase gradient transmit coil for TRASE imaging.

TRASE is an MRI k-space encoding method that uses radio-frequency (RF or B) transmit phase gradient fields to achieve millimeter-level spatial resolution. Image quality is critically dependent upon the efficient generation of B fields with uniform magnitude and strong phase gradients. We present the design of a new family of phase gradient transmit coil based upon a solenoid twisted about a transverse axis.

Least squares reconstruction of non-linear RF phase encoded MR data.

Purpose: The numerical feasibility of reconstructing MRI signals generated by RF coils that produce B1 fields with a non-linearly varying spatial phase is explored.

Theory: A global linear spatial phase variation of B1 is difficult to produce from current confined to RF coils. Here we use regularized least squares inversion, in place of the usual Fourier transform, to reconstruct signals generated in B1 fields with non-linear phase variation.

High-resolution MRI encoding using radiofrequency phase gradients.

Although MRI offers highly diagnostic medical imagery, patient access to this modality worldwide is very limited when compared with X-ray or ultrasound. One reason for this is the expense and complexity of the equipment used to generate the switched magnetic fields necessary for MRI encoding. These field gradients are also responsible for intense acoustic noise and have the potential to induce nerve stimulation.

B1 transmit phase gradient coil for single-axis TRASE RF encoding.

Purpose: TRASE (Transmit Array Spatial Encoding) MRI uses RF transmit phase gradients instead of B0 field gradients for k-space traversal and high-resolution MR image formation. Transmit coil performance is a key determinant of TRASE image quality. The purpose of this work is to design an optimized RF transmit phase gradient array for spatial encoding in a transverse direction (x- or y- axis) for a 0.

In vivo open-bore MRI reveals region- and sub-arc-specific lengthening of the unloaded human posterior cruciate ligament.

Open-bore MRI scanners allow joint soft tissue to be imaged over a large, uninterrupted range of flexion. Using an open-bore scanner, 3D para-sagittal images of the posterior cruciate ligament (PCL) were collected from seven healthy subjects in unloaded, recumbent knee extension and flexion. PCL length was measured from one 2D MRI slice partition per flexion angle, per subject.

MRI using radiofrequency magnetic field phase gradients.

Conventionally, MR images are formed by applying gradients to the main static magnetic field (B0). However, the B0 gradient equipment is expensive, power-hungry, complex, and noisy and can induce eddy currents in nearby conducting structures, including the patient. Here, we describe a new silent, B0 gradient-free MRI principle, Transmit Array Spatial Encoding (TRASE), based on phase gradients of the radio-frequency (RF) field.

The integration of real and virtual magnetic resonance imaging experiments in a single instrument.

We present the design of an integrated system for performing both real and virtual (simulated) magnetic resonance imaging (MRI) experiments. We emphasize the approaches used to maximize the level of integration and also the benefits that tight real-virtual integration brings for a scientific instrument. The system has been implemented for both low field (0.

Early detection and quantification of murine melanoma bone metastases with magnetic resonance imaging.

Objective: Bone metastases occur in approximately 80% of patients with advanced cancer and cause significant morbidity. There are currently no established means by which to identify the early growth of micro-metastatic cells or their effects on bone at a time when curative therapy might be initiated. We postulated that high-resolution magnetic resonance imaging (MRI) could detect and quantify the growth and destructive effects of bone micrometastases.

Magnetic resonance imaging of trabecular and cortical bone in mice: comparison of high resolution in vivo and ex vivo MR images with corresponding histology.

Measurements of bone morphometry and remodeling have been shown to reflect bone strength and can be used to diagnose degenerative bone disease. In this study, in vivo and ex vivo magnetic resonance imaging (MRI) techniques to assess trabecular and cortical bone properties have been compared to each other and to histology as a novel means for the quantification of bone. Femurs of C57Bl/6 mice were examined both in vivo and ex vivo on an 11.

In vivo morphological characterisation of skin by MRI micro-imaging methods.

Background/purpose: Quantitative assessments in skin layers using images obtained with standard magnetic resonance imaging (MRI) sequences are limited, since the stratum corneum and dermis, the layers of most clinical interest, have low signal due to their short spin-spin relaxation, T2.

Methods: In the present work, different methods of MRI contrast, such as magnetisation transfer contrast (MTC), T1-weighting (where T1 is spin-lattice relaxation time), T2*-weighting (where T2* is the combination of T2 and magnetic field in-homogeneity effect) and chemical shift, were used. These techniques were combined with high-resolution MRI.

High-resolution imaging at 3T and 7T with multiring local volume coils.

Magnetic resonance (MR) microimaging of the human is becoming increasingly common for studies of tissue microstructure and microfunction. In this study, we consider the constraints that such experiments place on the design of radio-frequency (rf) coils, and describe the advantages of multiring coils, which offer a locally uniform B(1) field. We show that these coils are particularly suitable for high-field imaging of a restricted region of larger experimental animals or humans, offering the same simplicity and efficient use of rf power as a simple surface coil but without requiring sequence modifications such as adiabatic pulses.

In vivo quantitative analysis of the effect of hydration (immersion and Vaseline treatment) in skin layers using high-resolution MRI and magnetisation transfer contrast.

Background/aims: Many claims are made as to the efficacy of topical preparations in moisturising the skin, yet most of these claims cannot be substantiated by scientific study for the skin layers beneath the stratum corneum, and yield no information on the remainder of the epidermis and dermis. This argues for an in vivo quantitative method for measuring the effect of water loading extended to various layers of the skin.

Methods: Detailed high-resolution in vivo MRI studies of hydration and dehydration of finger pad skin layers were conducted on one normal subject using two moisturisation methods (topical white soft paraffin (Vaseline) and water immersion).

An NMR technique for measurement of magnetic field gradient waveforms.

Almost all NMR imaging and localized spectroscopic methods fundamentally rely on the use of magnetic field gradients. It follows that precise information on gradient waveform shape and rise-times is often most useful in experimental MRI. We present a very simple and robust method for measuring the time evolution of a magnetic field gradient.

Normal murine bone morphometry: a comparison of magnetic resonance microscopy with micro X-ray and histology.

Objective: The authors have devised a means to assess subtle changes in the structure of bone using magnetic resonance (MR) microscopy. MR microscopy was compared with micro X-ray and histology to analyze the structure of normal bone.

Design: Femurs of C57Bl/6 mice were examined ex vivo using differently orientated slices and pulse sequences on both a 9.