Where contrast agent concentration really matters - a comparison of CT and MRI.

Objectives: First pass contrast-enhanced magnetic resonance imaging (MRI) and computed tomography (CT) are influenced by parameters that characterize the injected bolus. The aim of this study was to assess the role of contrast agent concentration and the differences between MRI and CT.

Material And Methods: We systematically evaluated the published literature to define the differences between MRI and CT with regards to the influence of contrast agent concentration and flow rate on signal enhancement and image quality.

Adjustable cerebrospinal fluid shunt valves in 3.0-Tesla MRI: a phantom study using explanted devices.

Purpose: Considering the rapidly increasing number of clinical high-field MR imagers and the lack of data regarding interference with magnetically adjustable cerebrospinal fluid (CSF) shunt valves, valve safety was assessed with regard to magnetic field interactions: imaging artifacts, heating, magnetic forces, and functional changes in a phantom study at 3.0 Tesla using explanted devices as a realistic model for in vivo conditions.

Materials And Methods: Sixteen explanted Codman-Medos and Sophy-SU8 shunt valves, all in perfect working order, were selected and exposed to a 3.

Oxygen therapy reduces secondary hemorrhage after thrombolysis in thromboembolic cerebral ischemia.

Hyperbaric oxygen (HBO) and normobaric hyperoxia (NBO) protect the brain parenchyma and the cerebral microcirculation against ischemia. We studied their effect on secondary hemorrhage after thrombolysis in two thromboembolic middle cerebral artery occlusion (MCAO) (tMCAO) models. Beginning 60 minutes after tMCAO with either thrombin-induced thromboemboli (TT) or calcium-induced thromboemboli (CT), spontaneously hypertensive rats (n=96) breathed either air, 100% O(2) (NBO), or 100% O(2) at 3 bar (HBO) for 1 hour.

Reduced anisotropy in the middle cerebellar peduncle in Chiari-II malformation.

Besides supratentorial abnormalities, spina bifida menigomyelocele (SBM) is typically associated with Chiari-II malformation comprising a small cerebellum, which herniates downward due to a shallow posterior fossa. We used diffusion tensor imaging to probe additional microstructural alterations of the major cerebellar white matter tracts, the cerebellar peduncles. A region-of-interest approach was employed in six SBM patients and six matched controls to compare the fractional anisotropy (FA) within the superior, middle, and inferior cerebellar peduncle (SCP, MCP, and ICP, respectively).

Kinetics of hematoma expansion in murine warfarin-associated intracerebral hemorrhage.

Background And Purpose: The burden of intracerebral hemorrhage associated with oral anticoagulants (OAC-ICH) is growing. However, little is known about the pathophysiology of W-ICH. Herein, we refine a mouse model of OAC-ICH using repetitive T2* MRI to describe kinetics of hematoma enlargement, and establish a benchside point of care INR assay (PoC) for assessment of anticoagulation.

[Magnetic resonance imaging of stents: quantitative in vitro examination at 3 Tesla].

Purpose: The aim of this study was to qualitatively and quantitatively study MR artifacts of various stents on the basis of in vitro experiments. We were particularly interested whether sequence type and orientation of the stent with respect to the static magnetic field influences the artifact.

Material And Methods: We examined 18 stents of different material (nitinol, stainless steel, cobalt alloy), different design of the stent meshes (AccuLink, OmniLink, DynaLink, Xact, Protoge, Wallstent Monorail), different diameter (5-10mm) and different length (18-58 mm) with a turbo spin echo (TSE), a 2D-fast low angle shot (FLASH) and a 3D-FLASH sequence.

In vitro comparison of different carotid artery stents: a pixel-by-pixel analysis using CT angiography and contrast-enhanced MR angiography at 1.5 and 3 T.

Introduction: CT angiography (CTA) and MR angiography (MRA) are increasingly used methods for evaluation of stented vessel segments. The purpose of this study was to compare CTA, contrast-enhanced MRA (CEMRA) at 1.5 T, and CEMRA at 3 T for the visualization of carotid artery stents and to define the best noninvasive imaging technique for each stent.

Carotid artery stents: in vitro comparison of different stent designs and sizes using CT angiography and contrast-enhanced MR angiography at 1.5T and 3T.

Background And Purpose: CT angiography (CTA) and MR angiography (MRA) are increasingly used methods for evaluation of stented vessel segments. Our aim was to compare CTA, contrast-enhanced MRA (CE-MRA) at 1.5T, and CE-MRA at 3T for the visualization of carotid artery stents and to define the best noninvasive imaging technique as an alternative to conventional angiography for each stent.

How does the injection protocol influence the attenuation-time curve in CT perfusion measurements: comparison of measured and simulated data.

In this study the authors compared a computer simulation that models bolus dispersion during the first pass to patient PCT data acquired with three different types of injection protocols. PCT was performed in 27 patients with one of the three injection protocols: (1) Monophasic bolus injection with saline flush, (2) monophasic bolus injection without saline flush, and (3) biphasic bolus injection with saline flush. They performed computer simulation to model bolus dispersion in the three injection protocols.

A single systemic transient hypotension induces long-term changes in rats' MRI parameters and behavior: relation to aging.

Objectives And Aim: The aim of this work was to examine whether a single 20-minute systemic hypotension induces short- and long-term changes in 12- and 18-month-old rat brain.

Methods: Age-related changes were determined after hemorrhagic hypotension over a 6-month period of investigation using holeboard testing, diffusion-weighted (DW) magnetic resonance imaging (MRI) and T2 and T2* relaxometry.

Results: The results showed a short-term but significant reduction in the apparent diffusion coefficient (ADC) after hypotension, which was accompanied by an increase in T2 relaxation time and deterioration in rat locomotor activity and memory capacities.

Prospective combined brain and spinal cord MRI in clinically isolated syndromes and possible early multiple sclerosis: impact on dissemination in space and time.

Background: The diagnosis of multiple sclerosis (MS) is based on dissemination in space (DIS) and time (DIT). The aim of the study was to assess the impact of spinal cord (SC) imaging on the evidence of DIS and DIT.

Methods: Thirty-five treatment-naive patients with a first clinical symptom suggestive of MS were examined in a 2-year prospective longitudinal follow-up assessment.

Fiber tracking of human brain using fourth-order tensor and high angular resolution diffusion imaging.

The accuracy of fiber tracking on the basis of diffusion tensor magnetic resonance imaging (DTI) is affected by many parameters. To increase accuracy of the tracking algorithm, we introduce DTI with a fourth-order tensor. Tensor elements comprise information obtained by high angular resolution diffusion imaging (HARDI).

DTI of commissural fibers in patients with Chiari II-malformation.

Chiari II-malformation is a complex congenital deformity of the brain which is frequently associated with hydrocephalus. Abnormalities of the corpus callosum are known to occur in the majority of patients. The objective of the present study was to study the microstructure of the corpus callosum (CC) and the anterior commissure (AC) to differentiate between different mechanisms of damage to these structures.

3T high-spatial-resolution contrast-enhanced MR angiography of the intracranial venous system with parallel imaging.

The diagnostic image quality of contrast-enhanced (CE) 3D MR venography (MRV) was prospectively compared with that of 2D time-of-flight (TOF) MRV and contrast-enhanced 3D magnetization-prepared rapid acquisition of gradient echo (MPRAGE) sequences for the visualization of the intracranial venous system at 3T in 22 patients. CE MRV provides high-quality images and was shown to be superior to TOF MRV and MPRAGE sequences in visualizing the normal intracranial venous system.

Hypothermia reduces cytotoxic edema and metabolic alterations during the acute phase of massive SAH: a diffusion-weighted imaging and spectroscopy study in rats.

Acute changes in cerebral perfusion and metabolism after subarachnoid hemorrhage (SAH) have been shown to contribute significantly to acute brain injury. The purpose of this study was to examine the effects of moderate hypothermia on the acute changes after massive experimental SAH as evaluated by diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS). SAH in rats was induced by injection of 0.

[Impact of technical and morphological factors on the precision of software-based MR tumor volumetry: a phantom study].

Purpose: To investigate the impact of technical and morphological parameters on the precision of software-based MR tumor volumetry (SBV) in an in-vitro experimental setting.

Materials And Methods: Tumor models were formed from a silicone compound in three different sizes with a max. diameter < 2 cm (small), 2 - 4 cm (middle), and > 4 cm (large).

Minocycline and hypothermia for reperfusion injury after focal cerebral ischemia in the rat: effects on BBB breakdown and MMP expression in the acute and subacute phase.

Reperfusion injury is a complication of recanalization therapies after focal cerebral ischemia. The disruption of the blood-brain barrier (BBB) caused by up-regulated metalloproteinases (MMPs) can lead to edema and hemorrhage. Middle cerebral artery occlusion (MCAO=90 min) and reperfusion (R=24 h vs.

Quantitative diffusion tensor imaging in herpes simplex virus encephalitis.

Diffusion-weighted imaging (DWI) has been employed in many brain pathologies, but with few studies only and heterogeneous results in herpes simplex virus encephalitis (HSVE). Diffusion tensor imaging (DTI) in comparison to DWI yields additional directional diffusion data, adding information and enabling a more differentiated description of brain pathologies. The authors addressed the question whether tissue changes as identified on T2-weighted magnetic resonance imaging (MRI) could be further characterized by DTI, in particular whether different forms of edema may occur in HSVE.

Diffusion tensor imaging screening of radiation-induced changes in the white matter after prophylactic cranial irradiation of patients with small cell lung cancer: first results of a prospective study.

Background And Purpose: Diffusion tensor imaging (DTI) will show abnormal fractional anisotropy (FA) in the normal-appearing brain after prophylactic cranial irradiation (PCI). These abnormalities will be more accentuated in patients with underlying vascular risk factors.

Materials And Methods: A prospective study by use of DTI and conventional T2-weighted MR images was performed with a 1.

Prevalence of cerebral microhemorrhages in amateur boxers as detected by 3T MR imaging.

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 amateur boxers than in nonboxers.

Delayed hyperbaric oxygenation is more effective than early prolonged normobaric hyperoxia in experimental focal cerebral ischemia.

Hyperbaric (HBO) and normobaric (NBO) oxygen therapy have been shown to be neuroprotective in focal cerebral ischemia. In previous comparative studies, NBO appeared to be less effective than HBO. However, the experimental protocols did not account for important advantages of NBO in the clinical setting such as earlier initiation and prolonged administration.

Functional magnetic resonance imaging for cranial neuronavigation: methods for automated and standardized data processing and management. A technical note.

Preoperative fMRI is one of the best established clinical fMRI applications. Due to the difficulties in recording and coregistration of functional image data, we present methods to standardize and automate these procedures. We used a self-made interactive software package (AFI - Automated Functional Imaging) to automate the time consuming and complex analysis of fMRI data.

Measuring anisotropic brain diffusion in three and six directions: influence of the off-diagonal tensor elements.

Diffusion tensor imaging (DTI) has been proposed for examination of cerebral white matter. However, this measurement needs sophisticated postprocessing and is susceptible to eddy current artefacts. The aim of this study was to examine whether diffusion measured in three anatomically well defined directions provides full and reliable information on diffusion anisotropy.

Polyamine-substituted gadolinium chelates: a new class of intracellular contrast agents for magnetic resonance imaging of tumors.

A new class of intracellular contrast agents (CA) for magnetic resonance imaging has been developed, based on Gd(DTPA) with two positively charged amide-linked substituents. Uptake of Gd(DTPA) into cultured tumor cell lines (B16 mouse melanoma, MH3924A Morris hepatoma) was below the detection limit while CA with the melanin-binding pharmacophore 2-(diethylamino)ethylamine reached intracellular concentrations of ca. 0.

Diphenyleneiodonium and dimethylsulfoxide for treatment of reperfusion injury in cerebral ischemia of the rat.

Diphenyleneiodonium (DPI) is an inhibitor of the free radical producing NAD(P)H-oxidase. We tested whether DPI shows neuroprotective properties after focal cerebral ischemia and we used dimethylsulfoxide (DMSO), a nonspecific free radical scavenger, as a solvent. In male Wistar rats middle cerebral artery occlusion (1.