Global white matter analysis of diffusion tensor images is predictive of injury severity in traumatic brain injury.

Conventional clinical neuroimaging is insensitive to axonal injury in traumatic brain injury (TBI). Immunocytochemical staining reveals changes to axonal morphology within hours, suggesting potential for diffusion-weighted magnetic resonance (MR) in early diagnosis and management of TBI. Diffusion tensor imaging (DTI) characterizes the three-dimensional (3D) distribution of water diffusion, which is highly anisotropic in white matter fibers owing to axonal length.

In vivo measurement of tissue damage, oxygen saturation changes and blood flow changes after experimental traumatic brain injury in rats using susceptibility weighted imaging.

Traumatic brain injury (TBI) is a prevalent disease, and many TBI patients experience disturbed cerebral blood flow (CBF) after injury. Moreover, TBI is difficult to quantify with conventional imaging modalities. In this paper, we utilized susceptibility weighted imaging (SWI) as a means to monitor functional blood oxygenation changes and to quantify CBF changes in animals after trauma.

Simultaneous detection of resolved glutamate, glutamine, and gamma-aminobutyric acid at 4 T.

A new approach is introduced to simultaneously detect resolved glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA) using a standard STEAM localization pulse sequence with the optimized sequence timing parameters. This approach exploits the dependence of the STEAM spectra of the strongly coupled spin systems of Glu, Gln, and GABA on the echo time TE and the mixing time TM at 4 T to find an optimized sequence parameter set, i.e.

Susceptibility-weighted imaging to visualize blood products and improve tumor contrast in the study of brain masses.

Purpose: To evaluate the diagnostic value of susceptibility-weighted imaging (SWI) for studying brain masses.

Materials And Methods: SWI is a high-resolution, three-dimensional, fully velocity-compensated gradient-echo sequence that uses both magnitude and phase data. Custom postprocessing is applied to enhance the contrast in the magnitude images between tissues with different susceptibilities.

The role of voxel aspect ratio in determining apparent vascular phase behavior in susceptibility weighted imaging.

Susceptibility weighted imaging (SWI) uses apparent phase contrast to enhance the contrast-to-noise ratio (CNR) in the magnitude image. In theory, the apparent phase will depend on the aspect ratio when both venous blood and parenchyma occupy the same voxel. To demonstrate the maximal expected effect of the external field from a vein, we model the vein as an infinitely long cylinder perpendicular to the main magnetic field.

Clinical applications of neuroimaging with susceptibility-weighted imaging.

Susceptibility-weighted imaging (SWI) consists of using both magnitude and phase images from a high-resolution, three-dimensional, fully velocity compensated gradient-echo sequence. Postprocessing is applied to the magnitude image by means of a phase mask to increase the conspicuity of the veins and other sources of susceptibility effects. This article gives a background of the SWI technique and describes its role in clinical neuroimaging.

Nonnvasive assessment of vascular architecture and function during modulated blood oxygenation using susceptibility weighted magnetic resonance imaging.

Susceptibility weighted imaging (SWI) is a BOLD-sensitive method for visualizing anatomical features such as small cerebral veins in high detail. The purpose of this study was to evaluate high-resolution SWI in combination with a modulation of blood oxygenation by breathing of air, carbogen, and oxygen and to directly visualize the effects of changing blood oxygenation on the magnetic field inside and around venous blood vessels. Signal changes associated with the response to carbogen and oxygen breathing were evaluated in different anatomic regions in healthy volunteers and in two patients with brain tumors.

Orientational dependence of trimethyl ammonium signal in human muscles by (1)H magnetic resonance spectroscopic imaging.

(1)H magnetic resonance spectroscopic imaging (MRSI) was used to investigate the effect of orientation on spectral characteristics of trimethyl ammonium (TMA) in human muscle at rest. Four different muscles in the healthy calf were studied: soleus, gastrocnemius, tibial posterior and anterior. The data demonstrate that muscle orientation can profoundly change apparent spectral characteristics of proton metabolites.

Imaging iron stores in the brain using magnetic resonance imaging.

For the last century, there has been great physiological interest in brain iron and its role in brain function and disease. It is well known that iron accumulates in the brain for people with Huntington's disease, Parkinson's disease, Alzheimer's disease, multiple sclerosis, chronic hemorrhage, cerebral infarction, anemia, thalassemia, hemochromatosis, Hallervorden-Spatz, Down syndrome, AIDS and in the eye for people with macular degeneration. Measuring the amount of nonheme iron in the body may well lead to not only a better understanding of the disease progression but an ability to predict outcome.

Susceptibility weighted imaging (SWI).

Susceptibility differences between tissues can be utilized as a new type of contrast in MRI that is different from spin density, T1-, or T2-weighted imaging. Signals from substances with different magnetic susceptibilities compared to their neighboring tissue will become out of phase with these tissues at sufficiently long echo times (TEs). Thus, phase imaging offers a means of enhancing contrast in MRI.

Reliability in detection of hemorrhage in acute stroke by a new three-dimensional gradient recalled echo susceptibility-weighted imaging technique compared to computed tomography: a retrospective study.

Purpose: To compare the sensitivity of magnetic resonance (MR) susceptibility-weighted imaging (SWI) with conventional MR sequences and computed tomography (CT) in the detection of hemorrhage in an acute infarct.

Materials And Methods: A series of 84 patients suspected of having acute strokes had both CT and MR imaging (MRI) scans with diffusion-weighted imaging (DWI) and SWI. The SWI sequence is a new high-resolution three-dimensional (3D) imaging technique that amplifies phase to enhance the magnitude contrast.

Coronary artery imaging using three-dimensional breath-hold steady-state free precession with two-dimensional iterative partial fourier reconstruction.

Purpose: To assess the feasibility of using a two-dimensional partial Fourier (PF) reconstruction scheme to reduce the acquisition time of magnetic resonance imaging (MRI) of coronary arteries.

Materials And Methods: Symmetric k-space data sets of coronary arteries were collected in seven volunteers using a three-dimensional breath-hold steady-state free precession (SSFP) sequence. Partial, asymmetric k-space data sets were generated by removing 25% of the data in the readout direction and 25% of the data in the phase encoding direction.

Hemorrhagic shearing lesions in children and adolescents with posttraumatic diffuse axonal injury: improved detection and initial results.

Purpose: To compare the effectiveness of a high-spatial-resolution susceptibility-weighted (SW) magnetic resonance (MR) imaging technique with that of a conventional gradient-recalled-echo (GRE) MR imaging technique for detection of hemorrhage in children and adolescents with diffuse axonal injury (DAI).

Materials And Methods: Seven young patients with a mean Glasgow Coma Scale score of 7 +/- 4 (SD) at admission were imaged a mean of 5 days +/- 3 after injury. High-spatial-resolution three-dimensional GRE imaging performed with postprocessing by using a normalized phase mask was compared with conventional GRE MR imaging.

Quantification of errors in volume measurements of the caudate nucleus using magnetic resonance imaging.

Purpose: To quantify the various sources of error in measuring the volume of the caudate nucleus and to understand these errors would lead to the standardization of the MRI protocol and would make the utility of data from around the world more viable in a global database.

Materials And Methods: We collected data at four different sites all using a Siemens 1.5T Vision MR Scanner.

Evaluation of polymer gels and MRI as a 3-D dosimeter for intensity-modulated radiation therapy.

BANG gel (MGS Research, Inc., Guilford, CT) has been evaluated for measuring intensity-modulated radiation therapy (IMRT) dose distributions. Treatment plans with target doses of 1500 cGy were generated by the Peacock IMRT system (NOMOS Corp.