Biomedical subjects

J Finsterbusch

Publications and source records attributed to J Finsterbusch.

11 recordsLinked to original sources

PubMed2003

Diffusion tensor imaging for long-term follow-up of corticospinal tract degeneration in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a predominantly clinical and electromyographic diagnosis. Conventional MRI reveals atrophy of the motor system, particularly the pyramidal tract, in the advanced stages but does not provide a sensitive measure of disease progression. Three patients with different principal symptoms of ALS, i.e., with predominant involvement of the upper (UMN) or lower (UMN) motor neurons, or bulbar disease, respectively, underwent serial clinical examination including lung function tests, conventional MRI, and diffusion tensor imaging (DTI). MRI demonstrated changes in of the pyramidal tract without measurable variation on follow-up. The patient with UMN involvement showed remarkable progressive loss of diffusion anisotropy in the pyramidal tract. DTI might be useful, together with clinical follow-up, as an objective morphological marker in therapeutic trials.

Amyotrophic Lateral Sclerosis↗

PubMed2003

Megalencephalic leukoencephalopathy with subcortical cysts in an adult: quantitative proton MR spectroscopy and diffusion tensor MRI.

A 37-year-old macrocephalic woman was investigated for increasing gait disturbance due to longstanding spasticity and ataxia. MRI showed widespread bilateral increase in signal from cerebral white matter on T2-weighted images. Numerous subcortical cysts were visible in anterior-temporal and parietal regions. These clinical and neuroradiological features are those of megalencephalic leukoencephalopathy with subcortical cysts (MLC), a recently delineated white-matter disease with onset in childhood. Quantitative localised proton MR spectroscopy of white matter revealed marked reduction of N-acetylaspartate, creatine, and choline with normal values for myo-inositol, consistent with axonal loss and astrocytic proliferation. Diffusion tensor imaging showed an increased apparent diffusion coefficient and reduced anisotropy in affected white matter pointing to reduced cell density with an increased extracellular space. These findings are in line with histological changes alterations known to occur in MLC.

Adult↗

PubMed2002

Distortion-free diffusion tensor imaging of cranial nerves and of inferior temporal and orbitofrontal white matter.

The main impact of functional neuroimaging has been its ability to locate neuronal activity either directly (EEG, MEG) or through the hemodynamic response caused by neuronal activity (PET, fMRI). In the past decade functional neuroimaging has been extended to investigate how brain regions interact, using the concepts of functional and effective connectivity. These concepts are further strengthened by estimates of anatomical connectivity of the same subject. A tool to determine anatomical connectivity in vivo may be provided by diffusion tensor imaging (DTI) methods. These can be used to determine the orientation of fiber bundles in white matter on the basis of the diffusion characteristics of water. Commonly, DTI data are acquired using echo planar imaging which suffers from susceptibility artifacts in orbitofrontal and inferior temporal cortex. Here we demonstrate the use of an alternative pulse sequence, diffusion-weighted single-shot STEAM, for assessing fiber orientation in orbitofrontal cortex and the cranial nerves. The scope of DTI needs to be extended to these structures to investigate psychiatric disorders in which orbitofrontal pathology or temporo-frontal disconnection have been postulated.

Adult↗

PubMed2002

[PACS: from project to reality. Report of experiences on full digitalisation of the radiology department of a major hospital].

OBJECTIVE: To assess the time needed and the resulting effects of a complete digitalisation of a radiological department of a major hospital (856 beds, 28,000 in-patients, 35,000 out-patients/year) a pilot study was performed. This had to be done without interrupting routine services. RESULTS: After intensive preparations were performed and the hospital-network was completed, within a two year period all radiological functions (mammography excluded), reporting stations and archives were changed to a complete digital workflow. All modalities (provided by 3 different companies) are now connected by DICOM-work lists. The picture-files (4 GB/day) are automatically routed to the work-stations (n = 10), where the reporting and file shows are performed, to the digital archive and to the peripheral viewing-stations (n = 44). The distribution of the digital pictures takes place all over the hospital including the ORs and special units. We accomplished, to connect electronically the report and the image data. The clinical file shows are also performed completely digitally. The access to the data of the deep archive is possible by the dept. of radiology without any manual interaction. The film consumption was reduced to an amount of less than 10%, as compared to the prior PACS situation. Since PACS has been introduced the radiological productivity increased by more than 15% and throughput-time was clearly reduced. CONCLUSIONS: The complete digitalisation increases productivity and attractiveness of a hospital-radiology and helps to shorten diagnostic and therapeutic decision-making. The transfer from a conventional to a digital workflow is possible without interrupting the clinical services. Extensive preparations and ongoing assistance of such projects though are clearly needed.

Computer Systems↗

PubMed2000

Diffusion tensor mapping of the human brain using single-shot line scan imaging.

A recently developed single-shot line scan imaging technique for diffusion measurements (Finsterbusch and Frahm, Magn Reson Med 1999;42:772-778) was extended to full diffusion tensor mapping of the human brain. Because the sequence acquires stimulated echoes from individual columns of magnetization ("lines"), the approach is affected neither by spatial aliasing when studying inner volumes nor by resonance offset effects or T2* dephasing as in diffusion-weighted echoplanar imaging. Experiments on healthy subjects were performed at 2.0 T using 31 single-shot images (5b values, 6 orientations, 520 msec each) at 1.5 x 1.5 mm2resolution (interpolated) and 6.0 mm section thickness. Apart from calculated images with isotropic diffusion weighting, the results include maps of the six independent diffusion tensor components, the apparent diffusion coefficient, the relative anisotropy, and the main diffusion direction. The achievable signal-to-noise ratio and resolution allow the identification of differently oriented nerve fibers in the brain stem. J. Magn. Reson. Imaging 2000;12:388-394.

Anisotropy↗

PubMed2000

Rapid isotropic diffusion mapping without susceptibility artifacts: whole brain studies using diffusion-weighted single-shot STEAM MR imaging.

A subsecond magnetic resonance imaging (MRI) technique for isotropic diffusion mapping is described which, in contrast to echo-planar imaging (EPI), is insensitive to resonance offsets, i.e., tissue susceptibility differences, magnetic field inhomogeneities, and chemical shifts. It combines a diffusion-weighted (DW) spin-echo preparation period and a high-speed stimulated echo acquisition mode (STEAM) MRI sequence and yields single-shot images within measuring times of 559 msec (80 echoes). Here, diffusion encoding involved one scan without DW, three DW scans with b = 490 sec mm(-2), and three DW scans with b = 1000 sec mm(-2) (orthogonal gradient orientations). An automated on-line evaluation resulted in isotropic DW images as well as ADC maps (trace of the diffusion tensor). Experiments at 2.0 T covered the brain of healthy subjects in 20 contiguous sections of 6 mm thickness and 2.0 x 2.0 mm(2) in-plane resolution within a total measuring time of 78 sec. High-resolution studies at 1.0 x 1.0 mm(2) (interpolated from 2.0 x 1.0 mm(2) acquisitions) were obtained within 5 min 13 sec using four averages. In comparison with EPI, DW single-shot STEAM MRI exhibits only about half the SNR, but completely avoids regional signal losses, high intensity artifacts, and geometric distortions.

Adult↗

PubMed2000

Reducing inhomogeneity artifacts in functional MRI of human brain activation-thin sections vs gradient compensation.

We evaluated two methods for correcting inhomogeneity-induced signal losses in magnetic resonance gradient-echo imaging that either use gradient compensation or simply acquire thin sections. The strategies were tested in the human brain in terms of achievable quality of T2*-weighted images at the level of the hippocampus and of functional activation maps of the visual cortex. Experiments were performed at 2.0 T and based on single-shot echo-planar imaging at 2. 0 x 2.0 mm(2) resolution, 4 mm section thickness, and 2.0 s temporal resolution. Gradient compensation involved a sequential 16-step variation of the refocusing lobe of the slice-selection gradient (TR/TE = 125/53 ms, flip angle 15 degrees ), whereas thin sections divided the 4-mm target plane into either four 1-mm or eight 0.5-mm interleaved multislice acquisitions (TR/TE = 2000/54 ms, flip angle 70 degrees ). Both approaches were capable of alleviating the inhomogeneity problem for structures in the base of the brain. When compared to standard 4-mm EPI, functional mapping in the visual cortex was partially compromised because of a lower signal-to-noise ratio of inhomogeneity-corrected images by either method. Relative to each other, consistently better results were obtained with the use of contiguous thin sections, in particular for a thickness of 1 mm. Multislice acquisitions of thin sections require minimal technical adjustments.

Adult↗

PubMed2000

Gradient-echo line scan imaging using 2D-selective RF excitation.

A gradient-echo line scan imaging technique was developed which employs two-dimensional spatially selective radiofrequency (2DRF) pulses for consecutively exciting individual columns of transverse magnetization, i.e., image lines. Although a variety of trajectories are possible for 2DRF excitation, the current implementation involved a blipped-planar trajectory in conjunction with additional saturation RF pulses to suppress side excitations above and below the desired image section, i.e., along the blip direction of the 2DRF pulse. Human brain imaging at 2.0 T (Siemens Vision, Erlangen, Germany) resulted in measuring times of 5.2 s for a 5-mm section at 1.0 x 1.0 mm in-plane resolution. Functional neuroimaging of the motor cortex at 1.2 s temporal resolution and 0.78 x 1.56 mm in-plane resolution exploited the capability of imaging inner volumes (here a 25-mm strip) without signal aliasing.

Algorithms↗

PubMed1999

Diffusion-weighted single-shot line scan imaging of the human brain.

Single-shot line scan imaging (LSI) was adapted to diffusion-weighted (DW) MRI by replacing the initial 90 degrees radiofrequency pulse of the underlying high-speed stimulated echo sequence by a DW spin-echo preparation period. Implementation on a 2. 0 T whole-body MRI system yielded DW images of the human brain with b factors of 750 s mm(-2) and total imaging times of about 500 ms either for a single slice at 1.5 x 3.0 x 6 mm(3) resolution or simultaneously for up to seven slices at 3.75 x 3.75 x 8 mm(3) resolution. Isotropic DW images and maps of the trace of the diffusion tensor were calculated from four scans with different combinations of three orthogonal diffusion gradients. DW LSI combines high speed with robustness against image artifacts caused by motion (no phase ghosting) and tissue susceptibility differences (no signal losses, no geometric distortions). Because the latter is an important advantage over echo-planar imaging, DW LSI may find useful applications despite a limited signal-to-noise ratio. Magn Reson Med 42:772-778, 1999.

Brain↗

PubMed1999

Single-shot line scan imaging using stimulated echoes.

A new high-speed MRI method is described for single-shot line scan imaging (LSI) based on stimulated echoes (STE). To allow for multislice imaging, the technique comprises a series of slice-selective preparation pulses (each corresponding to the first RF pulse of a STE sequence), a slab-selective refocusing pulse (second RF pulse), and multiple line-selective read pulses (third RF pulses). An alternative version employs packages of two slice-selective pulses followed by multiple line-selective read pulses. Experimental applications deal with human brain imaging on a clinical MRI system at 2.0 T. The technique offers user-selectable trade-offs between volume coverage (1-15 sections) and in-plane spatial resolution (1-5 mm linear pixel dimension) within total acquisition times of less than 500 ms. Although LSI yields a lower signal-to-noise ratio than Fourier imaging, single-shot LSI with STEs is free from resonance offset effects (e.g., magnetic field inhomogeneities and susceptibility differences) that are typical for echo-planar imaging. Moreover, the technique exhibits considerable robustness against motion and provides access to arbitrary fields-of-view, i.e., localized imaging of inner volumes without aliasing artifacts due to phase wrapping.

Adult↗

PubMed1997

Comparative EPR and redox studies of three prokaryotic enzymes of the xanthine oxidase family: quinoline 2-oxidoreductase, quinaldine 4-oxidase, and isoquinoline 1-oxidoreductase.

For three prokaryotic enzymes of the xanthine oxidase family, namely quinoline 2-oxidoreductase, quinaldine 4-oxidase, and isoquinoline 1-oxidoreductase, the electron transfer centers were investigated by electron paramagnetic resonance. The enzymes are containing a molybdenum-molybdopterin cytosine dinucleotide cofactor, two distinct [2Fe-2S] clusters and, apart from isoquinoline 1-oxidoreductase, a flavin adenine dinucleotide. The latter cofactor yields two different organic radical signals in quinoline 2-oxidoreductase and quinaldine 4-oxidase, typical for the neutral and anionic form, respectively. A "rapid" Mo(V) species is present in all enzymes with small differences in magnetic parameters. From spectra simulation of 95Mo-substituted quinoline 2-oxidoreductase, a deviation of 25 degrees between the maximal g and 95Mo-hyperfine tensor component was derived. The very rapid Mo(V) species was detected in small amounts upon reduction with substrates in quinoline 2-oxidoreductase and quinaldine 4-oxidase, but showed a different kinetic behavior with considerable EPR intensities in isoquinoline 1-oxidoreductase. The FeSI and FeSII centers produced different signals in all three enzymes and, in case of isoquinoline 1-oxidoreductase, revealed a dipolar interaction, from which a maximum distance of 15 A between FeSI and FeSII was estimated. The midpoint potentials of the FeS centers were surprisingly different and determined for FeSI/FeSII with -155/-195 mV in quinoline 2-oxidoreductase, -250/-70 mV in quinaldine 4-oxidase, and +65/+10 mV in isoquinoline 1-oxidoreductase. The slopes of the fitting curves for the Nernst equation are indicative for nonideal behavior. Only in quinoline 2-oxidoreductase, an averaged midpoint potential of the molybdenum redox pairs of about -390 mV could be determined. Both of the other enzymes did not produce Mo(V) signals in redox titration experiments, probably because of direct reduction of Mo(VI) to Mo(IV) in the presence of dithionite.

Electron Spin Resonance Spectroscopy↗