Biomedical subjects

C Stippich

Publications and source records attributed to C Stippich.

14 recordsLinked to original sources

PubMed2003

Differentiation of multiple sclerosis plaques, subacute cerebral ischaemic infarcts, focal vasogenic oedema and lesions of subcortical arteriosclerotic encephalopathy using magnetisation transfer measurements.

Although multiple sclerosis (MS) plaques, subacute cerebral ischaemic infarcts, focal vasogenic brain oedema, and subcortical arteriosclerotic encephalopathy (SAE) often have typical radiological patterns, they are sometimes difficult to distinguish from each other. Our aim was to determine whether they can be differentiated by magnetisation transfer (MT) measurements. We measured MT ratios (MTR) in ten patients with plaques of MS, 11 with subacute ischaemic infarcts, 12 with focal vasogenic oedema, and ten with lesions of SAE and compared the mean MTRs statistically. The MTR of normal white matter was 47.3%; the lowest MTR was found in plaques of MS (mean 26.4%). With the exception of vasogenic oedema and subacute cerebral ischaemic infarcts the mean MTRs were significantly different between all groups. MT measurements can provide additional information for the differentiation of these conditions, but we could not distinguish vasogenic oedema from subacute cerebral ischaemic infarcts.

Adult↗

PubMed2003

[Topography of the inferior alveolar nerve in relation to cystic processes of the mandible in dental MRI].

PURPOSE: Cystic processes are changing the course of the inferior alveolar nerve in the mandible. This study evaluates the possibility of demonstrating the relationship between space-occupying processes and the course of the neurovascular bundle. MATERIALS AND METHODS: Thirteen patients with cystic processes in the mandible (9 keratocystic lesions, 1 eosinophilic granuloma, 1 plasmocytoma, 2 adamantinomas) were examined by MRI (1.5-T magnet, 8-cm surface coil, PD-gradient-echo-sequences in sagittal and coronal orientation, without enhancement) and the results retrospectively evaluated. RESULTS: The entire course of the nerve could be delineated in all patients. In six patients with minor cystic processes, the nerve was identified in both sagittal and coronal orientation. In seven patients with major cystic lesions, only parts of the nerve were detected in either image orientation, but the nerve could be visualized in its entire length by evaluating coronal and sagittal images side by side. CONCLUSION: It is possible to delineate the inferior alveolar nerve in its entirety along pathologic mandibular lesions. For large cystic lesions, this requires the evaluation of both coronal and sagittal sections of multidirectional MRI.

Adolescent↗

PubMed2003

[Comparison of the reliability of subjective evaluation and quantitative measurements of MR signal intensity in inflammations of the intratemporal facial nerve].

PURPOSE: To compare in a single-blind study the reliability of quantitative measurements and subjective evaluations of contrast enhancement of the facial nerve in patients with idiopathic facial paralysis. MATERIALS AND METHODS: Magnetic resonance images with a 0.7 mm slice thickness (surface coil) were obtained in patients with idiopathic facial paralysis before and after administration of Gd-DTPA, 0.1 mmol/kg. The five intratemporal segments of the facial nerve were quantitatively measured and subjectively assessed by five radiologists as to the degree of enhancement. The results were compared as to the reliability of both methods. RESULTS: Using the quantitative measuring method, 175 measurements were calculated from a total of 350 regions of interest. At all 35 measured sites, the five quantitative measurements produced identical results. In contrast, the subjective assessment of the five radiologists arrived at a majority consensus in only 16 sites. A complete agreement was not reached for any measured site. CONCLUSION: The measured quantitative increase in signal intensity after administration of contrast medium is more reliable than subjective assessment. The quantitative method enables reproducible signal intensity measurements even for different window settings and can be easily and swiftly performed at the workstation.

Bell Palsy↗

PubMed2002

[Functional magnetic resonance imaging: Physiological background, technical aspects and prerequisites for clinical use].

The advent of powerful gradient systems and ultrafast echo-planar imaging (EPI) offers the opportunity to use magnetic resonance imaging to measure and to localize brain function with high spatio-temporal resolution in clinically feasible scanning times. Functional magnetic resonance imaging (fMRI) opens up a new diagnostic field in radiology and neuroradiology with a change from pure morphological brain imaging to the measurement and visualization of brain function. Despite its successful application in neurosurgical, neurological, psychiatric, neuropediatric and pain patients fMRI has not yet reached the status of an established clinical diagnostic procedure. To this end special stimulation systems, standardized fMRI protocols and medically approved software, all dedicated to clinical application, are necessary. The training and teaching of doctors and radiographers will also be crucial for the progress of clinical fMRI. This paper gives an overview of the neurophysiological background, the technical requirements and the data processing strategies that are relevant for the clinical application of fMRI. Presurgical fMRI in patients with brain tumors is used as an example for the clinical relevance of the method.

Brain↗

PubMed2001

Interaction of tactile input in the human primary and secondary somatosensory cortex--a magnetoencephalographic study.

Interaction of simultaneous tactile input at two finger sites in primary (SI) and secondary somatosensory cortex (SII) was studied by whole-head magnetoencephalography. Short pressure pulses were delivered to fingers of the right and left hand at an interstimulus interval of 1.6 s. The first phalanx of the left digit 1 and four other sites were stimulated either separately or simultaneously. We compared four sites with increasing distance: the second phalanx of left digit 1, left digit 5, and digits 1 and 5 of the right hand. The temporal evolution of source activity in the contralateral SI and bilateral SII was calculated using spatiotemporal source analysis. Interaction was assessed by comparing the source activity during simultaneous stimulation with the sum of the source activities elicited by separate stimulation. Significant suppressive interaction was observed in contralateral SI only for stimuli at the same hand, decreasing with distance. In SII, all digits of the same and the opposite hand interacted significantly with left digit 1. When stimulating bilaterally, SII source waveforms closely resembled the time course of the response to separate stimulation of the opposite hand. Thus, in bilateral simultaneous stimulation, the contralateral input arriving first in SII appeared to inhibit the later ipsilateral input. Similarly, the separate response to input at two unilateral finger sites which arrived slightly earlier in SII dominated the simultaneous response. Our results confirm previous findings of considerable overlap in the cortical hand representation in SII and illustrate hemispheric specialization to contralateral input when simultaneous stimuli occur bilaterally.

Adult↗

PubMed2001

[Radiotherapy planning for paraspinal tumors with CT-myelography].

BACKGROUND AND AIM: Artifacts due to metal implants are an important problem in diagnostic radiology and radiotherapy planning in tumors such as chordoma of the spine. A strict differentiation between target and radiosensitive structures e.g. spinal cord is absolutely essential for high-dose radiotherapy. Up to now CT and MRI techniques have provided only limited image quality in such situations. We introduce an approach to facilitate segmentation by using the technique of CT-myelography for radiation treatment. PATIENT AND METHOD: A 48-year-old woman with multiple inoperable relapses of a chordoma in the lumbar spine and extensive metal instrumentation in this area was given to radiotherapy using IMRT-technique (intensity modulated). MRI- and CT-planning images did not allow differentiation between myelon, cauda equina, dural sac and tumor. In this situation we performed a CT-myelography with the patient in treatment position. RESULT: CT-myelographic images enabled precise differentiation between myelon, cauda equina and intraspinal tumor. A substantial improvement of the segmentation of the spinal cord was obtained. There was no compression of the dural sac along the spine. This information provided the basis for a precise radiotherapy planning in IMRT-technique. CONCLUSION: In situations where CT- and MRI-techniques are not able to generate precise images which allow differentiation between tumor, myelon and cauda equina because of metal artifacts, CT-myelography is a promising technique which may help the diagnostic radiologist and radiation oncologist in planning radiotherapy.

Humans↗

PubMed2001

[Similarity of the brains of twins].

PURPOSE: To test the assumption underlying every morphometric twin study that the brains of monozygotic twins are almost identical. METHODS: High resolution MRI of the neurocranium of 26 monozygotic twin pairs were acquired and the volumes of 36 cerebral structures were measured. The same twins served as control group after rear-ranging them into non-related pairs of same sex and matching them for age, body height and body weight. RESULTS: For most of the examined structures the correlations within the twins were significant (R = 0.97-0.59). Except for total forebrain volume the controls showed no significant similarity. CONCLUSIONS: For almost every measured cerebral structure the assumption, that significant similarities exist between healthy monozygotic twins is correct. Therefore discordant monozygotic twins represent an excellent sample when investigating cerebral correlates of neurologic and psychiatric disorders.

Adult↗

PubMed2000

Fast temporal interactions in human auditory cortex.

The temporal resolution of the human primary auditory cortex (AC) was studied using middle-latency evoked fields. Paired sounds with either the same or different spectral characteristics were presented with gaps between the sounds of 1, 4, 8 and 14 ms. Spatio-temporal modelling showed (1) that the response to the second sound was recognizable with gaps of 1 ms and rapidly increased in amplitude with increasing gap durations, (2) an enhanced N40m amplitude at gaps > 4 ms, (3) delayed N19m-P30m latencies when the stimuli were different. The median psychoacoustical thresholds were 1.6 ms for the same stimuli and 2.5 ms for different stimuli, confirming the electrophysiological evidence for rapid pattern-specific temporal processing in human primary auditory cortex.

Acoustic Stimulation↗

PubMed2000

Time course of focal slow wave activity in transient ischemic attacks and transient global amnesia as measured by magnetoencephalography.

In this longitudinal study multichannel MEG was used to localize and to quantify focal pathological spontaneous neuromagnetic activity in six patients with transient ischemic attacks (TIA) and two patients with transient global amnesia (TGA). Slow (2-6 Hz) and beta (14-30 Hz) activity were monitored up to 10 weeks. Results were compared with normative data, and changes over time were statistically analyzed. MEG detected pathological activity that persisted clinical symptoms. Focal slow activity originating from sensorimotor (TIA) and mesiotemporal (TGA) cortices exceeded normal values up to 14 times during the first hours after the attack and recovered to normal within 11 days. Focal beta activity was not useful to monitor the time course of TIA or TGA.

Aged↗

PubMed2000

Magnetic source imaging of tactile input shows task-independent attention effects in SII.

We investigated whether attention to different stimulus attributes (location, intensity) has different effects on the activity of the secondary (SII) somatosensory cortex. Tactile stimuli were applied to the left index finger and somatosensory evoked fields (SEFs) were recorded using a whole-head magnetoencephalography (MEG) system. Two oddball paradigms with stimuli varying in location or intensity were performed in an ignore and an attend condition. Brain sources were estimated by magnetic source imaging. No attention effect was observed for the primary SI area. However, attention enhanced SII activity bilaterally from 55 to 130 ms by 52% in the spatial and 64% in the intensity discrimination task. SII attentional enhancement was very similar in both paradigms and occurred both for deviants and standards.

Adult↗

PubMed2000

Robust localization of the contralateral precentral gyrus in hemiparetic patients using the unimpaired ipsilateral hand: a clinical functional magnetic resonance imaging protocol.

Tumor related contralateral motor deficits complicate preoperative functional magnetic resonance imaging (fMRI). In plegic patients the localization of the sensorimotor cortex is often impossible. In this context we developed a clinical fMRI protocol dedicated to patients with motor deficits using the unaffected ipsilateral hand. Based on the hypothesis that selfpaced finger movements recruit more and larger neuronal populations with rising task complexity, different motor tasks were tested regarding ipsilateral localization in ten right handed volunteers. Complex finger opposition localized the ipsilateral premotor cortex (Brodman area 6) robustly and was introduced to preoperative fMRI in hemiparetic patients as functional landmark to identify the precentral gyrus on the tumors side. Additional contralateral automated tactile stimulation localized the primary somatosensory cortex and completed the protocol.

Adult↗

PubMed1999

Somatotopic mapping of the human primary somatosensory cortex by fully automated tactile stimulation using functional magnetic resonance imaging.

The clinical application of functional magnetic resonance imaging (fMRI) requires time-saving protocols insensitive to artifacts that provide robust localization and important information on brain function. A fully automated, pneumatically driven tactile stimulation is presented, that reproducibly localizes postcentral lip, finger and toe representations in contralateral primary somatosensory cortex (SI) with mean correlation coefficients (cc) and relative BOLD signal changes (dS) of cc approximately 0.59, dS approximately 1.95% (fingers); cc approximately 0.52, dS approximately 1.35% (lips); cc approximately 0.47, dS approximately 1.42% (toes). Bilateral somatotopic mapping requires 21 min of scanning time and has become a clinical routine fMRI application in patients with perirolandic tumors. Normative data may also be useful in monitoring cerebral plasticity and reorganization, e.g. in sensorimotor recovery after cerebral ischemia or in understanding mechanisms of supraspinal pain processing.

Adult↗

PubMed1999

Focal slow and beta brain activity in patients with multiple sclerosis revealed by magnetoencephalography.

In multiple sclerosis (MS) inflammatory infiltrations cause white matter lesions. Magnetoencephalography (MEG) offers the opportunity to localize abnormal electric activity of neurons with a high spatio-temporal resolution. In this study, we investigated patients with MS in order to find if abnormal cortical activity is associated with (subcortical) MS lesions using simultaneous bilateral recording of biomagnetic activity. Eight patients suffering from definite laboratory-supported MS with mainly somatosensory deficits and multiple bihemispheric plaques revealed by MRI were included in the study. To obtain normative data, 8 healthy volunteers were investigated following the same measuring protocol. Spontaneous magnetic brain activity was recorded using a 2x37-channel biomagnetic system (BTI, USA). Offline analysis included digital filtering (to separately investigate slow and beta wave activity), a Principle Component Analysis and the Dipole Density Plot. Localization results were inserted into MR images using our contour fit procedure. The dipole distribution in the brain was quantified and compared between the groups by statistical analysis. In all MS patients, the maximum of focal abnormal activity was localized in cortical areas adjacent to the fiber lesions. In the healthy subjects, no focal abnormal brain activity could be found. However, the standardized maximum concentrations of dipoles were significantly higher in the MS patients than in the healthy control group both in the slow and in the beta wave analysis. These results let assume that subcortical lesions can occur together with abnormal cortical neuronal activity. The results are discussed in respect to their impact on the interpretation of the analysis of spontaneous magnetic brain activity.

Adolescent↗

PubMed1998

Motor, somatosensory and auditory cortex localization by fMRI and MEG.

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) were performed in six subjects during self-paced finger movement performance, tactile somatosensory stimulation and binaural auditory stimulation using identical stimulation paradigms. Both functional imaging modalities localized brain activity in adjacent areas of anatomically correct cortex. The mean distances measured between fMRI activity and the corresponding MEG dipoles were 10.1 mm (motor), 10.7 mm (somatosensory), 13.5 mm (auditory right hemisphere) and 14.3 mm (auditory left hemisphere). The distances found may reflect the correlation between electrophysiological and hemodynamic responses due to the different underlying substrates of neurophysiology measured by fMRI and MEG: BOLD contrast vs neuronal biomagnetic activity.

Adult↗