Biomedical subjects

W J Huk

Publications and source records attributed to W J Huk.

At least 37 records · Page 2Linked to original sources

PubMed1997

Three-dimensional MR myelography of the lumbar spine: comparative case study to X-ray myelography.

Conventional myelography was compared with a new type of MR technique using a fat-suppressing 3D fast imaging with steady precession (FISP) sequence for diagnosis of the lumbar root compression syndrome. 80 patients with discogenic disease in the lumbar spine were examined with a 1.0-T whole-body MR system (Siemens Magnetom Impact, Erlangen, Germany). A strongly T2(*)-weighted 3D FISP sequence was applied in the sagittal orientation. To obtain fat suppression, a frequency-selective 1-3-3-1 prepulse was applied prior to the imaging sequence. The acquired 3D data set was evaluated using a maximum intensity projection (MIP) program. The measurement time was 7 min, 47 s. Magnetic resonance myelography has significant advantages over conventional myelography, particularly in cases of extreme spinal canal stenosis. Compared with the conventional method, this new MR technique shows comparable sensitivity in the visualization of the spinal nerve roots in the lumbar spine.

Case-Control Studies↗

PubMed1997

[Value of CT-angiography in the diagnosis of cerebral artery aneurysms].

PURPOSE: In a clinical study 35 patients with intracranial aneurysms were examined using CT-angiography, MR-angiography (MRA) and digital subtraction angiography (DSA). The aim of the study was to establish the ability of noninvasive techniques to detect intracranial aneurysms. MATERIAL AND METHODS: The CT examinations were performed using a spiral CT scanner and the MR investigations with a 1.5 T whole body MR-system. We used for MR-angiography Time of Flight (TOF) and Phase Contrast (PC) techniques. For postprocessing reconstructions modalities Maximum Intensity Projection (MIP), Surface and Volume Rendering Technique (VRT) techniques were used. The results were evaluated by the intraoperative findings. RESULTS: Aneurysms up to 5 mm could be detected best using CTA and DSA. Giant aneurysms could be evaluated best using CTA. Volume rendering technique was the most useful postprocessing procedure. MRA using Time of Flight was superior compared with MRA using PC technique. CONCLUSION: CTA is the best method to detect and to evaluate giant intracranial aneurysms. Nevertheless the reconstruction mode has a decisive influence on the results.

Adult↗

PubMed1997

MR cisternography: a new method for the diagnosis of CSF fistulae.

The aim of this study was to compare a new MRI method for detecting the existence of cerebrospinal fluid (CSF) fistulae, i. e. MR cisternography, with CT cisternography. In a prospective study, 30 patients with post-traumatic CSF fistulae were examined. The MR examinations were performed with a 1.0-T whole-body MR system, using two T2(*)-weighted sequences, a 3D PSIF (time-inversed fast imaging with steady-state precession, FISP) and a 3D constructive interference steady-state (CISS) sequence. The results of MRI and CT cisternography were compared with the surgical findings. The sensitivity in detecting CSF fistulae with MR cisternography (PSIF: 89.9 %; CISS: 93.6 %) was higher than with CT cisternography (72.3 %). The sensitivity of CT cisternography at detecting CSF fistulae in patients with a size of dural lesion less than 2 mm or in patients with multiple dural lesions is significantly lower compared with the MR method. Although the localization of CSF fistulae always proved possible with MR cisternography, this could only be accomplished wih CT in 70 % of cases. The MR cisternography technique is a new examination method with a higher sensitivity for the detection of CSF fistulae than CT cisternography. The CISS technique is superior compared with PSIF and should be used in patients with high-flow CSF fistulas.

Adolescent↗

PubMed1997

Neurophysiological findings in long-term survivors of acute lymphoblastic leukaemia in childhood treated with the BFM protocol 81 SR-A/B.

UNLABELLED: Monitoring of therapy-related late effects after acute lymphoblastic leukaemia (ALL) therapy in childhood has become an increasingly important field in posttherapeutic patient surveillance. The usefulness of neurophysiological investigations (e.g. EEG, evoked potentials (EP)) as part of these attempts is controversial. The present report focuses on this problem and the question whether and to what extent routinely performed EEG recordings and visual evoked potentials (VEP) were correlated with further measures of CNS integrity. EEGs and VEPs were recorded in 163 asymptomatic long-term survivors of ALL in childhood during a large retrospective multicentre study evaluating CNS late sequelae following antileukaemic therapy. Fifty-two ALL long-term survivors (4.5-10.6 years after end of therapy, median: 8.8 years), who had been treated according to BFM-81 SR-A (n = 30) or SR-B (n = 22) were selected for this analysis focusing on therapy-related CNS late effects. Therapy protocols differed with regard to the mode for CNS prophylaxis: SR-A, cranial irradiation with intrathecal methotrexate; SR-B, intrathecal and iv methotrexate. Neurophysiological findings were correlated with illness- and treatment-related parameters, as well as with data on the morphological, neurological and psychological status of the CNS. At the time of follow-up neurophysiological measures were abnormal in 28/52 cases (53.8%). Neither illness- nor therapy-specific differences in CNS prophylaxis showed any relationship to EEG/VEP outcome any relationship to EEG/VEP outcome in this reduced group of the whole study population. Children with EEG/VEP abnormalities showed a significantly higher incidence of structural CNS disturbances compared to those with inconspicuous neurophysiological recordings (60.9% vs 31.8%). However, in this special subject group there was no specific neurophysiological finding for a specific morphological substrate, neurological or psychological deficiency and vice versa. CONCLUSION: Routinely performed EEG/VEP investigations are not very helpful measures to predict the presence or degree of behavioural deficiencies, neurological disturbances, or morphological CNS abnormalities. Patients who received cranial irradiation or systemic methotrexate applications showed the same incidence of neurophysiological disturbances without evidence for specific neurotoxic correlates.

Adolescent↗

PubMed1997

[MR diagnosis of cerebrospinal fluid fistulas using a 3D-CISS sequence].

PURPOSE: We compared a new MR method for diagnosis of CSF fistulas with CT cisternography. MATERIAL AND METHODS: In a prospective case study we examined 35 patients with posttraumatic CSF fistulas and compared the results with the intraoperative findings. The MR investigation was performed using a 1.0T whole body MR-system. We used a strongly T2*-weighted 3D-CISS sequence. The examinations were performed in prone position, in patients with severe CSF rhinorrhoea additionally in supine position. RESULTS: The sensitivity and specificity of the MR method (88.9% and 95.1%) is higher compared with CT cisternography (77.8% and 87.8%). The reason for the lower sensitivity of CT compared with MRI are complex fracture systems, involving several paranasal cavities in patients with false positive results in CT cisternography. Reasons for the lower specificity of CT cisternography are false negative results in patients with small dural lesions below 2 mm2. CONCLUSION: Using a new method MRI can detect CSF-fistulas. The MR method is superior to CT cisternography, is noninvasive, the administration of contrast and agent is no longer necessary.

Adolescent↗

PubMed1996

Quantitative EEG in long-term survivors of acute lymphoblastic leukemia.

Conventional and quantitative aspects of electroencephalographic recordings obtained during a follow-up surveillance study in long-term survivors of acute lymphoblastic leukemia in childhood were investigated with respect to differences in central nervous system prophylaxis given during antileukemic therapy and compared with data derived from healthy controls. Central nervous system prophylaxis consisted either of cranial irradiation (18 Gray, group A, n = 8) or intermediate high-dose methotrexate (2000 mg/m2; group B, n = 5), each combined with intrathecal methotrexate. Conventional electroencephalographic analysis revealed comparable results in all three study groups. However, quantitative electroencephalography showed significantly increased absolute power scores for all frequency bands in both long-term survivor groups. Relative power estimates revealed a significant increase in delta/tau activities in both prophylaxis groups compared to healthy controls, which were countered by decreased percentage power scores in the alpha-range. Quantitative electroencephalographic comparisons between both central nervous system prophylaxis groups revealed only small differences in quantity, not quality, of the observed power disturbances with slightly higher deviations in irradiated long-term survivors than in nonirradiated ones. Topographical distributions of spectral band power were comparable between all three study groups without evidence for therapy-related topographical differences.

Adolescent↗

PubMed1996

[Dissection of the carotid artery and vertebral artery--diagnosis and therapy].

Carotid and vertebral artery dissections typically occur in young adults after major trauma, although they can arise spontaneously or after trivial injury. Many patients with carotid dissections have minor symptoms such as a subject bruit or Horner's syndrome. Cephalic pain is also frequent and often inaugural in carotid dissection. However, extracranial dissection is a well recognised cause of ischaemic stroke. The diagnosis of dissection was based on angiographic findings. Noninvasive imaging also allows prompt and reliable diagnosis. Our goal was to demonstrate the spectrum of neuroradiologic (CT, MR and angiographic) findings in craniocervical arterial dissection and compare the diagnostic utility of CT, MR, MR angiography. Clinical data imaging studies, and outcome were reviewed and compared with the results in four patients with carotid artery dissection.

Adolescent↗

PubMed1995

Ultra-rapid gradient echo imaging.

A novel ultra-rapid gradient echo (URGE) NMR imaging technique is introduced, which is capable of continuous high resolution 3D scanning while neither subject to fast gradient switching nor excessive RF power deposition. Sampling free induction decays instead of creating spin echoes enables maintaining a workable steady state magnetization. Due to segmented k-space acquisition, chemical shift, diffusion, and field inhomogeneity effects do not present major problems. We report on implementations acquiring from 32 x 64 x 64 partial-Fourier image sets in 0.72 s, allowing for single-shot magnetization-prepared 3D imaging, to 128 x 128 x 128 image sets in 13.3 s and 21.5 s on a standard MRI scanner.

Artifacts↗

PubMed1995

High-resolution magnetic resonance imaging of the endolymphatic duct and sac.

An anatomical study was carried out to determine the extent to which magnetic resonance imaging (MRI) could delineate inner ear structures. Anatomical preparations of human petrous temporal bone were examined and compared with the results of MRI in 20 healthy subjects to see whether the structures of the inner ear could be visualized. Imaging of the subjects was carried out in a 1.0-T MRI scanner (Siemens Magnetom Impact). Two strongly T2*-weighted sequences were used: a 3D-PSIF sequence and a 3D-CISS sequence. The 3D data sets were postprocessed using a Maximum Intensity Projection (MIP) program. Our investigations show that it is possible to obtain accurate visualization of structures with a diameter of under 1 mm. In all 20 subjects it was possible to identify both the endolymphatic duct and the endolymphatic sac.

Adult↗

PubMed1995

[Quality assurance in neuroradiology].

Due to growing economic pressure, quality management in medicine has to be performed under the aspect of rationing and rationalization simultaneously. High quality and cost effectiveness in medicine, however, can only be achieved by institutions with an adequate quality of structure, procedure and outcome. While the technical criteria of the quality of structure can easily be measured, the assessment of the quality of the performance and the outcome are much more difficult so establish. Therefore standards of quality for the various diagnostic and interventional subspecialties of Neuroradiology have to be designed. The same is true for the evaluation of the quality assurance. The quality of neuroradiology has reached a comparatively high level simply because of the specialization compared to general radiology. This advantage should be utilized more often when major diagnostic departments are to be installed, particularly under the aspect of cost effectiveness plus high quality medicine.

Cost-Benefit Analysis↗

PubMed1994

Raymond's syndrome following petrosal sinus sampling.

Inferior petrosal sinus sampling (IPSS) is used to evaluate the pituitary-dependency of Cushing's disease, and to predict the laterality of a microadenoma prior to transsphenoidal operation. A serious complication occurred in a 14-year-old boy: he suffered brain stem ischaemia with abducens nerve palsy and hemiparesis (Raymond's syndrome). The case prompted us to reconsider the indication for this investigation.

Abducens Nerve↗

PubMed1994

Magnetic source localization and morphological changes in temporal lobe epilepsy: comparison of MEG/EEG, ECoG and volumetric MRI in presurgical evaluation of operated patients.

Is MEG source analysis able to precisely locate the primary focal epileptic activity? 22 patients with pharmacoresistant temporal lobe epilepsy were recorded during presurgical evaluation simultaneously with multichannel MEG/EEG and invasive (subdural) electrodes to evaluate the increase of information gained by MEG concerning the localization of focal epileptic activity and lesions. With this systematic study it should become clearer how often MEG can establish a diagnostic bridge between function and morphology. In addition, MEG localization accuracy of focal epileptic activity was to be validated empirically by invasive EEG recordings and postsurgical outcome. Spikes in the MEG were used for magnetic source localization, and the result was combined with magnetic resonance imaging (MRI). All patients definitely suffered from temporal lobe epilepsy and revealed a structural abnormality in MRI. 17 patients with lesions in the temporal lobe were operated meanwhile and became markedly improved or seizure free. In 7 of 8 patients with a tumor and validated operation outcome, a very close correlation of the 3D-magnetic source localization and the border of the tumor in the brain was found (distance less than 10 mm). In 8 of 9 patients with a temporal/hippocampal atrophy and validated operation outcome, dipoles of epileptiform activity were located within the atrophic lobe.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗

PubMed1994

[3D-MR myelography in diagnosis of lumbar spinal nerve root compression syndromes. Comparative study with conventional myelography].

65 patients with nerve root compression syndrome were examined using a new type of MR-technique, which is comparable to the conventional X-ray myelography. The results of the prospective case study were compared with previous clinical experiences (1). For the examinations a 1.0T whole body MR-system (Siemens Magnetom Impact) was used. A strong T2*-weighted 3D-FISP sequence (TR = 73 ms, TE = 21 ms, alpha = 7 degrees) was applied in sagittal orientation using a circularly polarized oval spine coil. To obtain fat suppression a frequency selective 1-3-3-1 prepulse was applied prior to the imaging sequence. The acquired 3D-data set was evaluated using a Maximum Intensity Projection (MIP) program. Our results confirmed earlier experiences which showed that the diagnostic sensitivity of 3D-MR myelography (3D-MRM) is comparable to that of conventional X-ray myelography. In cases of severe spinal canal stenosis and spondylolisthesises, and in cases of postoperative scar tissue with nerve root compressions, the sensitivity of the 3D-MRM is higher as compared to that of conventional X-ray myelography.

Adult↗

PubMed1993

The role of transsphenoidal microsurgery in the management of sellar and parasellar meningioma.

We report on eight meningiomas that have been operated on via the transsphenoidal route since May 1988. Six patients harbored cavernous sinus meningiomas with intrasellar extension. The intrasellar tumor extension and the parasellar tumor portion medial to the carotid artery were removed. Decompression of the pituitary gland with normalization of prolactin levels was achieved in all patients. It is a well-tolerated approach to confirm the diagnosis and still allows the option of major transcranial surgery in the event of tumor progression. Additionally, we report complete tumor removal in two rare cases with intrasellar and suprasellar merely subdiaphragmatic meningiomas.

Adult↗

PubMed1993

Multichannel magneto-electroencephalography recordings of interictal and ictal activity.

A lobar or even a intralobar congruence was found when comparing the findings of magnetic source localization with presurgical evaluation (EEG, MRI and intraoperative ECoG) in temporal lobe epilepsy. The first dipolar activity that can be recognized during a spike-wave event (primary focal epileptic activity (PFA)) was localized in temporal neocortical or mesial regions. Further centres of epileptic activity could be localized by the method of spike averaging by correlation. This was interpreted as propagation of the electric activity. The comparison of interictal and ictal MEG localization results showed congruency in a patient with temporal lobe epilepsy. The combination of MEG and MRI helps to build a bridge between morphological and functional localization. MEG can serve as a pointer to discrete lesions in MRI.

Electroencephalography↗

PubMed1993

[Functional imaging of the brain. Magnetoencephalography (MEG)].

Magnetencephalography (MEG) is a new diagnostic tool for the exact localization of the biomagnetic sources of the electrical activity of the brain. The extremely weak magnetic fields are generated by the postsynaptic activity of the neurons, acting like current dipoles. They are measured with a SQUID (superconducting quantum interference device). Only the tangential components of the dipoles contribute to the measurable field outside the head. For MEG localization of sources, the brain is modelled as a sphere of homogeneous electrical conductivity, the center of which is fitted to MR images of the head. As a model of the current sources a one- or two-dipole model is used. For the analysis of more complex sources, however, a principle component analysis (PCA) should be performed before the dipole analysis, or the current-density distribution should be used. The effect of background activity can be eliminated by alpha wave filtering and the dipole-density plot (DDP), which also increases the signal/noise ratio. MEG seems to be useful in purely functional lesions of the brain. A final decision on the value of MEG for routine diagnosis is not yet possible, however.

Brain↗

PubMed1992

Magnetic resonance angiography of intracranial aneurysms: comparison with intra-arterial digital subtraction angiography.

Magnetic resonance angiography (MRA) with flow rephased gradient-echo sequences is a new non-invasive method for vascular imaging. We compared MRA and intra-arterial digital subtraction angiography in 18 patients with intracranial aneurysms to test whether MRA presently provides an alternative to cerebral angiography for the diagnosis of these anomalies. MRA showed 19 of the 22 aneurysms detected (86.4%). However, problems, especially with turbulent or slow flow, resulted in 6 studies (27.3%) with limited and 2 with questionable demonstration of an aneurysm, and 1 false negative study. At present, MRA is definitely inferior to angiography for the demonstration of intracranial aneurysms, due to its lower resolution and other limitations.

Adult↗

PubMed1991

Sodium-23 imaging of supratentorial lesions at 4.0 T.

In 27 patients with low and high grade gliomas (n = 17), meningiomas (n = 4), and other supratentorial tumors and lesions (n = 6), the results of sodium-23 MR imaging with high spatial resolution were compared to CT and proton MRI. The Na MR studies were performed with a 4.0-T whole-body MR system and an isotropic 3D-Flash sequence (TR 70 ms, TE 11 ms), which depicts the long T2 component of sodium. All patients tolerated the sodium study at 4.0 T well. The sodium images revealed almost all lesions, but the resolution was inferior to that of the reference methods. Two small meningiomas did not show up at all in the sodium study. Furthermore in one case small hemorrhages and calcifications within one of the tumors could not be found. Sodium imaging of the long T2 component did not provide any additional information regarding the histology, grading, size, and differentiation of the tumor from the surrounding edema which had not already been provided by CT or H MRI.

Adolescent↗