[en] Based on extensions and improvements in tissue differentiation and reductions in the time of measurement, at universities and in industry a number of different sequences have been developed, with widely different acronyms. Here, the author attempts to systematically describe the technical basis, following explanation of the sequences, and classify the many acronyms into groups of sequences with similar properties. Using examples from clinical practice, the potential advantages of different sequence groups for medical diagnosis are demonstrated. (orig.)

[en] Improvement in MR imaging signal-to-noise ratio (S/N) with the use of reduced read-out gradients is well known, as is the use of increased read-out gradients to diminish chemical shift effects. However, the optimization of read-out gradient strengths for specific clinical applications is not well documented. The authors compared image quality (in terms of S/N, tissue contrast and boundary definition) in 20 patients with brain lesions and 20 patients with head and neck lesions. All patients were scanned on a 1-T system using gradient strengths of 11.56 mT/cm and 0.78 mT/cm. The authors found improved S/N and increased contrast in the low bandwidth images of the CNS. Chemical shift effects were negligible in these images but were increased and significantly degraded in the head and neck examination. Therefore, the authors recommend a choice of two bandwidths for ''neuroradiologic'' examinations: low for CNS studies and high for head and neck studies

[en] A velocity spectrum may allow the flow within small vessels to be characterized even when the vessels are only a few pixels in cross-sectional area. An anisotropic three-dimensional Fourier-transformed MR imaging sequence with a bipolar velocity-encoding gradient in the third dimension produced velocity spectra of a phantom containing a jet and a stenosis. The low spatial resolution spectra downstream of the jet and at the inlet, neck, and outlet of the stenosis exhibited differences from normal laminar flow, the differences were consistent with the expected distribution of velocities

[en] The 'sequence tree' sketched in Figure 1 serves as an overview of the sequences discussed in this article. The classical division into Spin Echo and Gradient Echo sequences is made depending on whether the image is T₂-weighted or T₂*-weighted. The Spin Echo family includes the conventional Spin Echo (SE) sequence and the Inversion Recovery sequences (IR, IRM and STIR), as well as newer variants such as TSE, TIRM and HASTE. The Gradient Echo family can be divided into the FLASH group (SSI: Steady State Incoherent technique) and the FISP group of sequences (SSC: Steady State Coherent technique). Acronyms located near the 'branch' are either very similar to the type discussed or even identical. A combination of pure Gradient Echo sequences with spin echoes and other echo paths is found with the PSIF, CISS, DESS and true FISP sequences. (orig.)

[en] The wide range of different sequences available, with their widely different acronyms, are summarized and their clinical potential discussed. Part 1 of this report, about the Spin Echo family, appeared in the previous volume, 1/96. Part 2 deals with Gradient Echo sequences, with the exception of Echo Planar imaging, which together with hybrid techniques, i.e. mixed Gradient Echo - Spin Echo sequences, will be subject of Part 3. (orig.)

[en] A 90⁰-r-90⁰ -image pulse sequence spatially maps magnetic field distortions arising from susceptibility differences. Three phantoms having three concentric cylinders of fluid were imaged. The outer and inner cylinders of each contain a 5-mM NiCl/sub 2/ solution. The middle cylinders contain either NiCl/sub 2/, sunflower oil, or 9-mMDyCl/sub 3/. Sunflower oil exhibits only a chemical shift, while dysprosium has both chemical shift and a significant susceptibility difference compared with nickel-doped water. Images of the NiCl/sub 2/ and sunflower oil phantoms are similar, while those of dysprosium show marked field distortions. Varying tau to phase-encode the resonant frequency allows quantitative measurement of field distortion

[en] The aim of this study was to assess the detectability of the trigeminal nerve and its branches using T1 weighted (w.) 3-D magnetization prepared rapid gradient echo (MP-RAGE), T2* w. 3D CISS and T2 w. 2-D turbo spin echo MR sequences. Thirty healthy volunteers were examined for this purpose using a 1.5 Tesla MR unit. The detectability of the trigeminal nerve and Gasser's Ganglion, i.e. structures that are surrounded by liquor was best using 3-D CISS. In the case of the ophthalmic, maxillary and mandibular nerves, the T1 w. 3-D MPRAGE was significantly better than T2* w. CISS and T2 w. 2-D turbo spin echo. The latter yielded the poorest results. We conclude that both high resolution T2* w. and T1 w. 3-D sequences are necessary in order to detect the liquor-surrounded trigeminal nerve and its soft tissue-surrounded branches. We would therefore recommend the inclusion of constructive interference in steady state (CISS) and MP-RAGE in a MR imaging protocol of the trigeminal nerve and its branches

[en] At the 'Joint Test Rig (PNS 4215) for Testing and Calibrating of Two-phase Mass Flow Measurement Techniques' roughly 250 tests were performed within the range of p = 5 - 100 bar with α = 0 - 1 und m = 0 - 4 kg/s. Velocities of 0,1 - 50 m/s for both phases and slip ratios of 1,0 - 7,0 were measured. A typical result has been represented as an example in the two diagrams. Until completion and installation in the test rig of the γ-absorption density measuring system the two-phase mass flow was calculated from the steam and water velocities measured by the radiotracer method as well as from the pressure, temperature, and superficial velocities. The values so determined showed good agreement with the balance mass flows evaluated by the IRB Institute. It was demonstrated in these two-phase velocity measurements that the gaseous and liquid tracers mix well with the related steam and liquid phase, respectively, and stay in this phase as a gas and liquid, respectively. Moreover, further knowledge was derived about the length of starting and measuring sections. Good results have been likewise obtained with the multiple beam γ-absorption density measuring system, which started operation in the fourth quarter of the year, so that it is possible now to determine the mass flow directly from the velocities of the two phase and from the density of the two-phase mixture. (orig.)

[en] At the Karlsruhe polarized neutron facility POLKA precise neutron-deuteron scattering experiments were carried out in the energy range from 18 to 50 MeV. Angular distributions of the n→-d analyzing power A/sub y/ were determined in ten energy bins for both the elastic scattering and the n→-d breakup to the FSI region. The data have been corrected for multiple scattering and finite geometry effects and are presented together with Faddeev calculations using various NN potentials. These calculations seem to be unable to reproduce the backward angle shape of recent dσ/dΩ data. The authors have, therefore, measured the differential cross section of the elastic and scattering in the angular range 130⁰-170⁰ (C.M.). The data were normalized to a measurement of the np cross section utilizing the same techniques of charged particle detection

No abstract available