Restoring three-dimensional magnetic resonance angiography images with mean curvature motion.

OBJECTIVE: The management of neurovascular disease requires precise information on the cerebral vascular anatomy. Digital subtraction angiography (DSA) is the gold standard against which other imaging modalities have to be measured. To improve the quality of three-dimensional (3D) magnetic resonance angiography (MRA) images, we present a novel concept in 3D image analysis. METHODS: Five patients, harboring cerebral aneurysm, underwent DSA, computed tomography angiography (CTA) and MRA. MRA data were processed using a novel anisotropic curvature motion model. Three-dimensional reconstructions of CTA and MRA datasets were used for comparison. RESULTS: The 3D-reconstructed images accurately displayed all aneurysms. The anatomy of the anterior part of the circle of Willis was visualized reliably. The smoothened vessel surfaces enhanced the readability of the images. Regarding visual representation of the posterior part of the circle of Willis, the post-processed MRA showed the arterial segments less accurate than the standard modalities. CONCLUSIONS: This new approach is a promising tool for planning of neurovascular interventions and preoperative evaluation.

[Analysis of MR image quality of echo planar diffusion-weighted imaging: investigations at 1.5 Tesla with higher gradient field strength]. / Analyse der Bildqualität einer diffusionsgewichteten (EPI DWI) Sequenz: Untersuchungen an einem 1,5 T MRT mit höherer Gradientenfeldstärke.

PURPOSE: Single-shot echo planar Diffusion-weighted-Imaging (EPI DWI) requires extended gradient facilities with strong, fast switching gradients. Up to now the image quality of EPI DWI is enormously influenced by some kinds of artifacts. Therefore we evaluated the image quality of EPI DWI in demonstrating anatomical structures using a 1.5 T MR scanner with a higher gradient field strength of 40 mt/m, a risetime of 200 micros and a slewrate of 200T/m/s. MATERIALS AND METHODS: Using an evaluation scale with four categories two independent readers evaluated 12 different infra- and supratentorial anatomic regions of the brain on 50 DWI images and compared them with the corresponding T2 turbospin echo image. RESULTS: No region was judged to be undistinguishable. On axial DWI images the assessment of the brain stem was poor. In the level of the putamen and thalamus the image quality of DWI was judged to be from adequate to excellent. The central sulcus and the boundary of the white and grey matter was assessed to be adequately visible. The interobserver variability showed a good agreement between the two readers. CONCLUSION: The image quality of EPI DWI improves from a higher gradient field strength. The shortening rise time of 200 micros and the slewrate of 200 T/m/s will lead to a faster gradient switching. Single shot EPI DWI is less influenced by image artefacts and the presentation of different anatomical structures profits when a MR scanner with higher gradient field strength is used.

Magnetic resonance imaging, computed tomography, and conventional X-ray in 3 cases of symmelia.

BACKGROUND: Symmelia is a rare birth defect, often combined with severe malformations of the urogenital system and the lower gastrointestinal tract. Additionally, a deformed pelvis and various degrees of separation of the lower limbs are present. CASES: We report the examination findings of 3 autopsy specimens of symmelia using magnetic resonance imaging (MRI) and computed tomography (CT) with 3-dimensional (3D) reconstructions, and conventional X-ray. CONCLUSIONS: MRI and CT with the addition of 3D visualization can be used additionally with autopsy and conventional X-ray images in the investigation of such complex anatomical abnormalities.

ADC mapping of normal human brain.

BACKGROUND: The quantification of diffusion conditions in normal human brain has been gaining more and more attention since diffusion weighted imaging (DWI) was proved to be an important tool in the evaluation of cerebral pathologies, especially regarding the diagnosis of hyperacute stroke. The purpose of this study was to investigate the apparent diffusion coefficient (ADC) and anisotropy index (AI) in normal human brain to evaluate physiological ADC values for an ADC mapping of different brain regions. MATERIAL/METHODS: 22 regions of interest (ROIs) in the ADC maps of 53 volunteers showing no cerebral pathologies were measured in the gray and white matter of the frontal, parietal and occipital lobes, the corpus callosum, and the lateral ventricles. RESULTS: Apparent diffusion is quite inhomogeneous for different brain regions. In both subcortical white matter (ADC: 525 x 10(-8) mm2/s, AI: 0.05) and in gray matter (ADC: 1486 x 10(-8) mm2/s, AI: 0.05) diffusion was isotropic, while in periventricular white matter (ADC: 408 x 10(-8) mm2/s, AI: 0.34) and the corpus callosum (ADC: 799 x 10(-8) mm2/s, AI: 0.77) anisotropic. CONCLUSIONS: With the exception of children and young adults, ADC seems to be intra- and interindividually constant, with no sex or age dependency for the patient sample we investigated (mean age: 62+/-9.4 years). Hence the measurement of ADC may provide an index of lesion severity.