Macroscopic magnetic field inhomogeneities might lead to image distortions, while microscopic field inhomogeneities, due to susceptibility changes in tissues, cause spin dephasing and decreasing T(2)() relaxation time. The latter effects are especially observed in the trabecular bone and in regions adjacent to air-containing cavities when gradient-echo sequences are applied. In ...

The tiny difference between hard pi pulses and their delta-function approximation can be exploited to control coherence. Variants on the magic echo that work despite a large spread in resonance offsets are demonstrated using the zeroth- and first-order average Hamiltonian terms, for 13C NMR in 60C. The 29Si NMR linewidth ...

A double inversion-recovery (DIR) sequence with an echo-planar imaging (EPI) readout can be used to image selectively the grey matter of the brain, and this has previously been applied to improve the sensitivity of the statistical analysis of functional magnetic resonance imaging (fMRI) data. If a procedure were to be ...

PURPOSE: Online MR-thermometry during hyperthermia can improve treatment control. It needs excellent image quality during hyperthermia treatment to get information from subtracted images. MATERIALS AND METHODS: For hybrid hyperthermia two high-frequency devices were used in combination working with different frequencies. The imaging was performed on a 1.5 T MR tomograph ...

PURPOSE: To develop computer-assisted image processing to identify the central sulcus from the MRI data sets in patients with brain tumors. MATERIALS AND METHODS: All MR images were acquired with a 3.0 Tesla scanner by three-dimensional (3D) spoiled gradient recalled acquisition using the steady state (SPGR) gradient-echo sequence and short ...

The purpose of this study was to prospectively compare the performance of magnetic resonance (MR) elastography using echo-planar and spin-echo imaging for staging of hepatic fibrosis. Twenty-four patients who had liver biopsy for suspicion of chronic liver disease had MR elastography performed with both spin-echo and echo-planar sequences. At histology, ...

In magnetic resonance electrical impedance tomography (MREIT), currents are injected into an object, the resulting magnetic flux density is measured using MRI, and the conductivity distribution reconstructed using these MRI data. The relatively long acquisition times of conventional MREIT methods limit the signal averaging rate and are susceptible to motion ...

Microfluidics has advanced to become a complete lab-on-a-chip platform with applications across many disciplines of scientific research. While optical techniques are primarily used as modes of detection, magnetic resonance (MR) is emerging as a potentially powerful and complementary tool because of its non-invasive operation and analytical fidelity. Two prevailing limitations ...

OBJECT: Neuroradiology has become indispensable in detecting the pathophysiology in syringomyelia. Constructive interference in steady-state (CISS) magnetic resonance (MR) imaging can provide superior contrast at the sub-arachnoid tissue borders. As this region is critical in preoperative evaluation, the authors hypothesized that CISS imaging would provide superior assessment of syrinx pathology ...

OBJECTIVE: The Fourier transform, a fundamental mathematic tool widely used in signal analysis, is ubiquitous in radiology and integral to modern MR image formation. Understanding MRI techniques requires a basic understanding of what the Fourier transform accomplishes. MR image encoding, filling of k-space, and a wide spectrum of artifacts are ...

With the development of dedicated receiver coils and increased gradient performance, 3.0-T magnetic resonance (MR) systems are gaining wider acceptance in clinical practice. The expected twofold increase in signal-to-noise ratio (SNR) compared with that of 1.5-T MR systems may help improve spatial resolution or increase temporal resolution when used with ...

PURPOSE: Motion artifact is problematic in the diagnosis of Creutzfeldt-Jakob disease (CJD) because of dementia. The purpose was to compare the occurrence of this artifact between a diffusion-weighted (DW) magnetic resonance (MR) imaging sequence and conventional sequences. MATERIALS AND METHODS: Ten MR examinations comprising T2-weighted, T1-weighted, DW, and fluid-attenuated inversion ...

Rapid MR imaging using the stimulated echo acquisition mode (STEAM) technique yields single-shot images without any sensitivity to resonance offset effects. However, the absence of susceptibility-induced signal voids or geometric distortions is at the expense of a somewhat lower signal-to-noise ratio than EPI. As a consequence, the achievable spatial resolution ...

We investigated magnetization transfer (MT) effects on the steady-state MR signal for a sample subjected to a series of identical on-resonance RF pulses, such as would be experienced while imaging a single slice using a spoiled gradient echo sequence. The MT coupling terms for a two-pool system were added to ...

The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a longitudinal multisite observational study of healthy elders, mild cognitive impairment (MCI), and Alzheimer's disease. Magnetic resonance imaging (MRI), (18F)-fluorodeoxyglucose positron emission tomography (FDG PET), urine serum, and cerebrospinal fluid (CSF) biomarkers, as well as clinical/psychometric assessments are acquired at multiple time points. ...

The routine use of arterial spin-labeling (ASL) in a clinical population has led to the depiction of diverse brain pathologic features. Unique challenges in the acquisition, postprocessing, and analysis of cerebral blood flow (CBF) maps are encountered in such a population, and high-quality ASL CBF maps can be generated consistently ...

In the mid 1990s, the fast spin-echo (FSE) and turbo spin-echo (TSE) T2-weighted (T2-W) sequences became available and are now widely accepted alternatives to conventional spin-echo sequences since they result in reduced acquisition times while maintaining tissue contrast. Since that time, there has been continued development of new sequences to ...

The purpose of this study was to produce an magnetic resonsnce (MR) image atlas of clinically relevant brain anatomy and to relate this neuroanatomy to clinical signs. The brain of a large mixed breed dog was imaged in transverse, sagittal, and dorsal planes using a 1.5 T MR unit and ...

A 3D inner-volume fast spin echo (3D IV-FSE) sequence was developed for ECG-gated, black-blood, T1- and T2-weighted vessel wall imaging of peripheral vein bypass grafts (PVBG). The sequence utilizes nonselective refocusing excitations to minimize echo spacings and a highly selective IV excitation scheme to minimize the need for oversampling of ...

OBJECTIVE: Ventricular shunting is a common neurosurgical procedure. Metal-containing shunt components can cause artifacts on magnetic resonance imaging (MRI), obscuring visualization of the surrounding tissue. We present the case of a radiation-induced meningioma growing around a ventricular catheter that was not noted at an early stage as a result of ...

The goal of this study was to evaluate the MR compatibility of the Neurelec Digisonic SP cochlear implant by performing in vitro and in vivo tests. All tests were performed on 1.5 T machine. Torque and force were measured to observe a potential displacement of the internal receiver. Demagnetisation of ...

Quantification of fat has been investigated using images acquired from multiple gradient echoes. The evolution of the signal with echo time and flip angle was measured in phantoms of known fat and water composition and in 21 research subjects with fatty liver. Data were compared to different models of the ...

Few institutions use MRI perfusion without contrast injection called arterial spins labeling (ASL) routinely in clinical setting. After general considerations concerning the different ASL techniques and quantitative issues, we will detail a pulsed sequence that can be used on a clinical 1.5-T MR unit. We will discuss and illustrate the ...

Single-shot echo-planar imaging (EPI) is an important method for MRI of the brain. A method has been developed to double the resolution of EPI in the phase-encode direction, without requiring increases in the maximum gradient amplitude or slew rate. The new approach is based on an EPI implementation of the ...

This HIPAA-compliant study had institutional review board approval, with waiver of informed consent. The purpose was to test the hypothesis that, compared with a standard magnetic resonance (MR) cholangiography sequence, MR cholangiography with a sampling perfection with application optimized contrasts using different flip angle evolutions (SPACE) sequence reduces ghosting artifacts ...

This work assesses the temporal resolution of dual-source computed tomography (CT) in a visually intuitive manner. Exploiting the principles of ring artifact creation, a phantom containing a highly attenuating delta function signal (a wire) was rotated at the same speed as the gantry, creating a partial ring artifact where the ...

OBJECTIVE: The purpose of our study was to characterize the imaging features of an MDCT artifact caused by gas bubble motion. MATERIALS AND METHODS: For the period 2002-2006, the CT images of 10 patients that revealed a curvilinear artifact thought to be due to a gas bubble moving during CT ...

PURPOSE: To develop a method that automatically corrects ghosting artifacts due to echo-misalignment in interleaved gradient-echo echo-planar imaging (EPI) in arbitrary oblique or double-oblique scan planes. MATERIALS AND METHODS: An automatic ghosting correction technique was developed based on an alternating EPI acquisition and the phased-array ghost elimination (PAGE) reconstruction method. ...

In humans that have undergone cervical diskectomy, magnetic susceptibility artifacts are often found on postoperative magnetic resonance (MR) images of the affected region. In some patients, these artifacts complicate image interpretation, while in others the artifacts lead to a false diagnosis of spinal cord compression. We describe two dogs and ...

Recent technical advances have enabled the visualization of neuromelanin in the substantia nigra pars compacta (SNc) and locus ceruleus (LC) by 3-tesla (T) magnetic resonance imaging in vivo. In the present study, we successfully detected neuromelanin in the SNc and LC of 6 healthy volunteers at 1.5T using a 3D ...

The chemical shift displacement error (CSDE) is an often-underestimated problem in slice selection for localized proton spectroscopy at higher fields. With the proposed semi-localized by adiabatic selective refocusing (LASER) pulse sequence, this problem is dealt with by using RF pulses with bandwidths in the order of 5 kHz. A combination ...

PURPOSE: We assessed the frequency of common bile duct (CBD) motion artifacts caused by inferior vena cava (IVC) pulsation on magnetic resonance cholangiopancreatography (MRCP). METHODS: We retrospectively evaluated CBD motion artifacts in 4 MRCP sequences from each of 115 consecutive patients. RESULTS: We observed 37 (32.2%) ghost artifacts at the ...

Magnetic steering of an untethered ferromagnetic device in a living body has many advantages in the clinical fields. In this paper, the positioning and tracking methods of a ferromagnetic sphere have been compared with magnetic resonance phantom images obtained with three different imaging sequences, spin echo, gradient echo, and selected ...

OBJECTIVE: To examine some typical histological findings in Crohn's disease using high-frequency ultrasound and to define the echo properties of these findings. MATERIAL AND METHODS: Bowel resection specimens from 14 patients operated on for Crohn's disease were examined with a 10 MHz linear array ultrasound transducer in a saline reservoir. ...

PURPOSE: To prospectively compare single-shot spin-echo echo-planar imaging (SSSE-EPI) using b = 0, 10, 150, and 400 seconds/mm(2) with standard MRI techniques after intravenous super paramagnetic iron oxide (SPIO) in the detection and characterization of focal liver lesions with focus on small (<10 mm) focal liver lesions. MATERIALS AND METHODS: ...

PURPOSE: To determine the benefits of variable-rate selective-excitation (VERSE) radio frequency (RF) pulses for increased slice coverage in breathhold (BH) fat-suppressed T2-weighted fast spin-echo (FS-T2W-FSE) liver imaging at 3.0T. MATERIALS AND METHODS: A total of 12 healthy volunteers were imaged on 3.0T, using FS-T2W-FSE. Slice coverage and specific absorption rate ...

We evaluated the newly developed whole-brain, isotropic, 3-dimensional turbo spin-echo imaging with variable flip angle echo train (SPACE) for contrast-enhanced T(1)-weighted imaging in detecting brain metastases at 3 tesla (T). Twenty-two patients with suspected brain metastases underwent postcontrast study with SPACE, magnetization-prepared rapid gradient-echo (MP-RAGE), and 2-dimensional T(1)-weighted spin echo ...

Existing functional brain MR imaging methods detect neuronal activity only indirectly via a surrogate signal such as deoxyhemoglobin concentration in the vascular bed of cerebral parenchyma. It has been recently proposed that neuronal currents may be measurable directly using MRI (ncMRI). However, limited success has been reported in neuronal current ...

BACKGROUND AND PURPOSE: The bilateral foramina of Monro occlusion is an extremely rare event in adults. To date, only six cases of adult hydrocephalus due to idiopatic obstruction of the bilateral foramina of Monro (including our patient) have been reported. METHODS: The authors describe the case of a 41-year-old man ...

Magnetic resonance imaging (MRI) at a field-strength of 3 T has become more and more frequently used in recent years. In an increasing number of radiological sites, 3-T MRI now starts to play the same role for clinical imaging that was occupied by 1.5-T systems in the past. Because of ...

Strain and motion measurements in balanced steady-state free precession (bSSFP) imaging require high magnetic field homogeneity. This requirement is due to the nonlinear signal response to spin phase variations in bSSFP. Here, a technique that utilizes background gradients for preparing strong in-plane spin phase variations is proposed. As a result, ...

This work introduces an MR-compatible active breathing control device (MR-ABC) that can be applied to lung imaging. An MR-ABC consists of a pneumotachograph for respiratory monitoring and an airway-sealing unit. Using an MR-ABC, the subjects were forced to suspend breathing for short time intervals, which were used in turn for ...

PURPOSE: To develop a rapid stimulated echo acquisition mode (STEAM) MRI technique for "black-blood" imaging of the human heart that overcomes the single-slice limitation and partially compromised blood suppression associated with double inversion-recovery techniques. MATERIALS AND METHODS: Black-blood multislice images of the heart along anatomic orientations and triggered to end ...

State-of-the-art magnetic resonance imaging (MRI) protocol for the evaluation of rectal cancer suggests only T2-weighted fast spin-echo sequences. We present a case of rectal cancer with a simultaneous presacral myelolipoma that could have been misdiagnosed on MRI as a metastasis if a T1-weighted sequence had not also been used in ...

This study was designed to assess whether breath-hold cardiac multiecho imaging at 3.0 T is achievable without significant image artefacts and if fat/water phase interference modulates the exponential T2* signal decay. Twelve healthy volunteers (mean age 39) were imaged on a Philips Intera 3.0 T MRI scanner. Multiecho imaging was ...

PURPOSE: Measurement protocols which have been optimized for MRI at field strengths of 1.5 T or 3 T cannot be directly transferred to 7 T. Specific absorption rate limitations, different tissue relaxation times, as well as new image artifacts require adjustments of the sequence parameters. The goal of our study ...

OBJECTIVE: The objective of our study was to evaluate intraoperative low-field MRI for the frequency and duration of imaging sessions needed during surgery, the direct additional procedure time attributable to imaging, and the proportion of cases in which information provided by intraoperative MRI led to a change in the procedure ...

BACKGROUND AND PURPOSE: The evidence for traumatic brain injury in amateur boxers is controversial. Hypothetically, sudden acceleration of the head due to the impact of the blow during the boxing fight might result in diffuse axonal injury or contusion. We wanted to determine whether cerebral microhemorrhages occur more often in ...

Cortical bone in the mature skeleton has a short T(2)* and produces no detectable signal with conventional MR sequences. A two-dimensional ultrashort echo time (UTE) sequence employing half radio frequency (RF) pulse excitations and radial ramp sampling reduces the effective TE to 8 micros and is capable of detecting signals ...

Multi spin-echo sequences such as single-shot RARE are very sensitive to the initial phase of the transverse magnetization, and they can preserve only the transverse magnetization component which is aligned with the axis of the refocusing pulse rotation. Therefore, two separate single-shot RARE experiments with phases of refocusing pulses 90 ...