Magnetic resonance current density imaging (MRCDI) and magnetic resonance electrical impedance tomography (MREIT) visualize an internal distribution of current density and/or conductivity by injecting current into an electrically conductive object such as the human body using an MRI scanner. MREIT measures the induced magnetic flux density which appears in the ...

INTRODUCTION: Susceptibility-weighted imaging (SWI) is a novel magnetic resonance (MR) technique that exploits the magnetic susceptibility differences of various tissues, such as blood, iron and calcification. This pictorial review covers many clinical conditions illustrating its usefulness. METHODS: SWI consists of using both magnitude and phase images from a high-resolution, three-dimensional ...

The BLADE and PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) techniques have been proposed to reduce the effect of head motion. Preliminary results have shown that BLADE also reduces pulsation artifacts from venous sinuses. The purpose of this study was to compare T1-weighted FLAIR acquired with BLADE (T1W-FLAIR ...

Magnetic resonance imaging (MRI) is capable of imaging infiltrative lung diseases as well as solid lung pathologies with high sensitivity. The broad use of lung MRI was limited by the long study time as well as its sensitivity to motion and susceptibility artifacts. These disadvantages were overcome by the utilisation ...

OBJECTIVE: Co-registration of EEG (electroencephalogram) and fMRI (functional magnetic resonance imaging) remains a challenge due to the large artifacts induced on the EEG by the MR (magnetic resonance) sequence magnetic fields. Thus, we present an algorithm, based on the average-subtraction method, which is able to correct EEG data for gradient ...

OBJECTIVES: The aim of this study was to test the hypothesis that dental materials vary significantly in MR-relevant material parameters-magnetic susceptibility and electrical conductivity, and that knowledge of these parameters may be used to estimate the quality of MR imaging in the presence of devices made of such materials. METHODS: ...

A proton magnetic resonance image of ice was observed with the stray-field (STRAFI) technique. A preliminary study of proton relaxation times was performed in water and ice, at different temperatures. For example, a value of 3.5 micros for the spin-spin relaxation time, T(2), was found in ice at 258 K. ...

INTRODUCTION: Single-shot (SS) turbo spin-echo (TSE) diffusion-weighted (DW) magnetic resonance imaging (MRI) is a non echo-planar imaging (EPI) technique recently reported for the evaluation of middle ear cholesteatoma. We prospectively evaluated a SS TSE DW sequence in detecting congenital or acquired middle ear cholesteatoma and evaluated the size of middle ...

Postoperative patients may develop complications requiring imaging. Although any imaging technique can be used to investigate these patients, the presence of metal hardware in the region of interest may distort the image and interfere with diagnosis. It is important to understand why this distortion occurs and how to compensate for ...

Magnetic resonance (MR) imaging at 3.0 T offers an improved signal-to-noise ratio compared with that at 1.5 T. However, the physics of high field strength also brings disadvantages, such as increases in the specific absorption rate, in magnetic field inhomogeneity effects, and in susceptibility artifacts. The use of 3.0-T MR ...

RATIONALE AND OBJECTIVES: To determine the sensitivity of susceptibility-weighted imaging (SWI) for depicting hemorrhagic hypointense foci of the brain in comparison with gradient-recalled echo (GRE)- and GRE-type single-shot echo-planar imaging (GREI, GRE-EPI), and to assess the basic characteristics of the susceptibility effect by using a phantom. MATERIALS AND METHODS: We ...

Four-dimensional CT images are generally sorted through a post-acquisition procedure correlating images with a time-synchronized external respiration signal. The patient's ability to maintain reproducible respiration is the limiting factor during 4D CT, where artifacts occur in approximately 85% of scans with current technology. To reduce these artifacts and their subsequent ...

The purpose of this article is to present a educational overview of practical tips to deal with metal artefacts in clinical musculoskeletal MRI. A brief theoretical explanation to understand the cause of metal artefacts is provided followed by a discussion on parameters to reduce these metal artefacts. Effects of adjustable ...

Intrauterine devices (IUDs) have been viewed as an effective form of contraception. However, the mechanism by which IUDs disturb fertility remains controversial. This study aimed to evaluate the effects of IUDs on uterine contractility using cine MR. Eleven healthy female volunteers of reproductive age bearing IUDs and 12 women not ...

OBJECTIVE: Molecular targeted MR imaging of human clots material in a model of pulmonary embolism using a fibrin-specific magnetic resonance imaging contrast agent (EP-2104R, EPIX Pharmaceuticals, Cambridge, MA). MATERIAL AND METHODS: Fresh ex vivo engineered thrombi (human blood) and human clots removed from patients were delivered in 11 swine. Molecular ...

This paper aims to demonstrate the capabilities of a speed optimized T(2) weighted single-shot turbo spin echo sequence, using parallel imaging, variable flip angle refocusing and half-Fourier acquisition (FAS-TSE), in comparison with a standard TSE (sTSE) sequence in patients with suspected multiple sclerosis (MS). 33 patients presenting with a clinically ...

A magnetic resonance imaging (MRI) pulse programmer has been developed using a single-chip microcontroller (ADmicroC7026). The microcontroller includes all the components required for the MRI pulse programmer: a 32-bit RISC CPU core, 62 kbytes of flash memory, 8 kbytes of SRAM, two 32-bit timers, four 12-bit DA converters, and 40 ...

PURPOSE: To retrospectively evaluate cisterna chyli (CC) enhancement on magnetic resonance (MR) images obtained after intravenous administration of a gadolinium-based contrast agent. MATERIALS AND METHODS: This retrospective HIPAA-compliant study of 1.5-T MR imaging findings was institutional review board approved; informed patient consent was waived. All MR examinations involved the acquisition ...

PURPOSE: To design and construct an anthropomorphic head phantom using materials of appropriate magnetic susceptibility and air spaces of realistic dimensions, with the aim of reproducing the susceptibility artifacts found in the human brain. MATERIALS AND METHODS: The phantom is based on a plastic skull filled with MnCl2-doped water. Materials ...

The purpose of this work was to present and evaluate a new method for directly designing T2-selective preparation pulses. Using a modified Shinnar-Le-Roux (SLR) transform, the design of T2-selective pulses becomes equivalent to designing a pair of polynomials one of which represents the longitudinal magnetization and the other the transverse ...

OBJECTIVE: To obtain dynamic images of articulators using a magnetic resonance imaging (MRI) movie and to clarify the relationships among the articulators. MATERIALS AND METHODS: The subjects consisted of 10 volunteers. Custom-made circuitry was connected to an MRI apparatus to enable an external trigger pulse to control the timing of ...

Echo-planar imaging (EPI) is the standard technique for dynamic susceptibility-contrast (DSC) perfusion MRI. However, EPI suffers from well-known geometric distortions, which can be reduced by increasing the k-space phase velocity. Moreover, the long echo times (TEs) used in DSC lead to signal saturation of the arterial input signal, and hence ...

The ability to detect brain anatomy and pathophysiology with MRI is limited by the contrast-to-noise ratio (CNR), which depends on the contrast mechanism used and the spatial resolution. In this work, we show that in MRI of the human brain, large improvements in contrast to noise in high-resolution images are ...

As the amygdala is involved in various aspects of emotional processing, its characterization using neuroimaging modalities, such as functional magnetic resonance imaging (fMRI), is of great interest. However, in fMRI, the amygdala region suffers from susceptibility artifacts that are composed of signal dropouts and image distortions. Various technically demanding approaches ...

OBJECTIVES: To determine quantitative and qualitative image quality in patients undergoing magnetic resonance (MR) cholangiography at 3.0 Tesla (T) compared with 1.5 T. MATERIALS AND METHODS: Fifty patients (30 women; mean age, 51 years) underwent MR cholangiography at 1.5 T; another 50 patients (25 women; mean age 51 years) were ...

PURPOSE: To characterize misregistration artifact in arterial input function (AIF) pixels in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a two-dimensional non-echo-planar imaging (EPI)-based gradient-recalled echo (GRE) sequence. MATERIALS AND METHODS: Dynamic gadopentetate-enhanced MRI was acquired in the rat using a semikeyhole acquisition scheme. The AIF was obtained from abdominal ...

Recently, balanced steady-state free precession (SSFP) magnetic resonance imaging at small flip angles (i.e. FLAPS imaging) has been shown to preferentially enhance the visibility of spins residing near susceptibility-shifted media by exploiting the unique spectral response of SSFP signals. Nevertheless, the use of FLAPS imaging to visualize passive, susceptibility-shifted devices ...

Whole body magnetic resonance imaging (whole body MR imaging) could potentially provide accurate cancer staging as a single imaging modality. This study was done to develop a whole body MR imaging protocol for a 1.5T MR instrument using four normal Beagle dogs (Phase 1) and then to assess the protocol's ...

PURPOSE: To develop a gradient insensitive, generic technique for recording of non-MR signals by use of surplus scanner bandwidth. MATERIALS AND METHODS: Relatively simple battery driven hardware is used to transform one or more signals into radio waves detectable by the MR scanner. Similar to the "magstripe" technique used for ...

At magnetic resonance (MR) imaging and multidetector computed tomography (CT), artifacts arising from metallic orthopedic hardware are an obstacle to obtaining optimal images. Although various techniques for reducing such artifacts have been developed and corroborated by previous researchers, a new era of more powerful MR imaging and multidetector CT modalities ...

This paper describes a variant of time-of-flight magnetic resonance (MR) imaging that provides a method of measuring the inherent mixing in a fluidized bed without the introduction of tracer particles. The modifications to conventional time-of-flight imaging enable the measurement of the axial mixing of a precisely controlled initial particle distribution, ...

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has become a widely used application in spite of EEG perturbations due to electromagnetic interference in the MR environment. The most prominent and disturbing artifacts in the EEG are caused by the alternating magnetic fields (gradients) of the MR scanner. Different ...

Magnetic field gradients play a fundamental role in MR imaging and localized spectroscopy. The MRI experiment, in particular fast MRI, relies on precise gradient switching, which has become more demanding with the constantly growing number of fast imaging techniques. Here we present a simple MR method to measure the behavior ...

OBJECTIVES: To investigate interobserver variability in the delineation of head-and-neck (H&N) anatomic structures on CT images, including the effects of image artifacts and observer experience. METHODS: Nine observers (7 radiation oncologists, 1 surgeon, and 1 physician assistant) with varying levels of H&N delineation experience independently contoured H&N gross tumor volumes ...

PURPOSE: To evaluate the effect of incidental magnetization transfer (iMT) in multislice brain imaging at 3.0T. MATERIALS AND METHODS: The contribution of iMT to multislice brain MRI was evaluated at 3.0T. In 10 normal subjects we obtained multislice fast spin-echo (FSE) MR images using a 16-echo pulse train without an ...

Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium and CoCrMo-alloys or carbon fiber reinforced polymers (CFRP). Implant-related susceptibility artifacts can decrease the quality of magnetic resonance imaging (MRI) scans. This cadaveric study aimed to demonstrate the extent that implant-related MRI artifacting affects the postfusion ...

In this retrospective review, we demonstrate the utility of using a commercially available gated navigator sequence (prospective acquisition correction technique [PACE]) to reduce rhythmic breathing motion on brain MR images. For purposes of this report, we studied 2 sedated patients who had marked head rocking, one due to deep breathing ...

Accurate and efficient filtering techniques are required to suppress large nuisance components present in short-echo time magnetic resonance (MR) spectra. This paper discusses two powerful filtering techniques used in long-echo time MR spectral quantitation, the maximum-phase FIR filter (MP-FIR) and the Hankel-Lanczos Singular Value Decomposition with Partial ReOrthogonalization (HLSVD-PRO), and ...

BACKGROUND: Evaluation of the severity and the follow-up of aortic insufficiency (AI) are important tasks in paediatric cardiology. Assessment is based on clinical and echocardiographic (ECHO) findings such as the configuration of the valve and the regurgitation fraction (RF). OBJECTIVE: The goal of this study was to evaluate MRI compared ...

Diagnostic imaging of systemic disorders, such as peripheral vascular diseases, requires a field-of-view (FOV) larger than the local FOV available on clinical MR scanners. The continuously moving table (CMT) method acquires large FOV images in a single acquisition. Balanced steady-state free precession (bSSFP) is an attractive candidate for the CMT ...

OBJECTIVE: To evaluate motion artifacts and patient acceptability of MR imaging of claustrophobic patients in an open 1.0T scanner. SUBJECTS AND METHODS: Thirty six claustrophobic patients were enrolled prospectively, 34 of which had previous MR examinations in closed bore magnets. Anxiety and pain during MR examination in an open 1.0T ...

Magnetic resonance images are prone to artifacts caused by metallic objects. Apart from being a source of image degradation, such artifacts can also provide information about the magnetic properties of the foreign object. In this work, we aim to explore the potential of magnetic resonance imaging to detect and characterize ...

A complex sum method of quantifying the magnetic susceptibility of a long, narrow cylinder embedded in a uniform medium has been developed. The radius of the cylinder can be as small as one pixel. The susceptibility inside the object is extracted from the magnetic resonance complex images, using two concentric ...

OBJECT: The recently developed vascular space occupancy (VASO) fMRI technique is gaining popularity as it facilitates the measurement of cerebral blood volume (CBV) changes concomitant with brain activation, without the use of contrast agents. Thus far, VASO fMRI has only been used in conjunction with a GE-EPI (gradient-echo echo planar ...

OBJECTIVE: The non-pregnant uterus shows wave-like activity (uterine peristalsis). This pilot study was intended to determine: (1) whether uterine peristalsis during the menstrual cycle is detectable by cine magnetic resonance imaging (MRI); (2) the effects of leiomyoma on uterine peristalsis. STUDY DESIGN: Mid-sagittal MRI was performed sequentially with T2-weighted single-shot ...

In MRI of human brain, the respiratory cycle can induce B0-field fluctuations through motion of the chest and fluctuations in local oxygen concentration. The associated NMR frequency changes can affect the MRI data in various ways and lead to temporal signal fluctuations, and image artifacts such as ghosting and blurring. ...

Physiologic motions can appear during a Computed Tomography (CT) exam. Even if some motions can be prevented, others are unavoidable. To tempt to correct the resulting artifacts, it is necessary to understand their apparition and their influence on the image quality. By using an anthropomorphic phantom and a dynamic platform, ...

Whole-brain images were acquired with a 2X acceleration factor by using Simultaneous Multi-slice Acquisition (SMA). Utilizing a Sinc pulse modulated by cosine/sine functions combined with an extra gradient along the slice-selection direction during acquisition, we are able to take multiple magnetic resonance images of different slice simultaneously. 2-slice and 4-slice ...

PURPOSE: To compare the value of different MRI sequences of the lung for the detection of pulmonary metastases. MATERIALS AND METHODS: A total of 28 patients with 225 pulmonary metastases confirmed at multidetector-row computed tomography (MDCT) underwent MRI of the lung, including breathhold T2-weighted single-shot turbo spin-echo (half-Fourier single-shot turbo ...

We have developed a compact magnetic resonance (MR) imaging scanner with permanent magnet, gradient coil set, and radiofrequency (RF) coils optimized for whole-hand examination for the diagnosis of rheumatoid arthritis (RA). The system weighs about 600 kg, and installation space is 2 m(2), excluding the shield room. Hand examinations of ...