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Biomedical subjects

D Petersen

Publications and source records attributed to D Petersen.

At least 55 records · Page 3Linked to original sources
PubMed1996

3D MR angiography with ramp-shaped flip-angle distribution.

This study addressed the use of 3D MR angiography with flip angles (FAs) linearly varying across the excitation volume in order to diminish spin saturation. The shape of the ramp profile was varied to optimize the method for different regions and pathological alterations. Radio frequency pulses with ramp-shaped excitation profiles were generated using Fourier transformation and integrated into a flow-compensated 3D-FISP sequence. With the use of ramp-shaped excitation profiles good results were obtained for intracranial arteries as well as for neck arteries (i.e. carotid and vertebral arteries) which were demonstrated in 6 healthy volunteers and in 5 patients with various stenoses and anomalies of the carotid and vertebral arteries. With this technique it was possible to use increased thicknesses of the excitation volume (slab) up to 256 mm. Ramp-shaped excitation pulses with linearly increasing FAs in main flow direction can provide improved contrast of the vessel parts located distally to the entry side of the slab. Although this method has no advantage concerning complex flow or other dephasing effects; its particular effectiveness lies in the reduction of spin saturation.

Aged↗
PubMed1996

Diagnosis.

Explore the source record for details and available documents.

Adaptation, Psychological↗
PubMed1996

Interobserver agreement in assessing early CT signs of middle cerebral artery infarction.

PURPOSE: To assess the reliability of detecting signs of hemispheric infarction on CT scans obtained within 6 hours of the onset of symptoms. METHODS: A neuroradiologist selected 12 normal and 33 abnormal CT studies showing the hyperdense middle cerebral artery sign (HMCAS) (n = 10), brain swelling (n = 22), and parenchymal hypodensity (n = 33) from two series of 750 patients with recent onset of middle cerebral artery stroke. These selections served as the reference source for a nonblinded analysis of the initial and follow-up CT scans. Six neuroradiologists then reviewed the CT scans twice, first blinded then not blinded to clinical symptoms. They assessed the signs of infarction for each hemisphere separately and estimated the volume of abnormal parenchymal hypodensity in increments of 20% within the territory of the middle cerebral artery. RESULTS: Unblinding the reviewers did not change interobserver agreement significantly. The chance adjusted agreement was moderate to substantial: kappa = .62 (95% confidence interval [CI], .46 to .78) and kappa = .57 (95% CI, .33 to .81) for the HMCAS of the right and left hemisphere, respectively; kappa = .59 (95% CI, .47 to .71) and kappa = .56 (95% CI, .38 to .74) for focal brain swelling of the right and left hemisphere, respectively; and kappa = .58 (95% CI, .50 to .66) and kappa = .55 (95% CI, .32 to .67) for parenchymal hypodensity of the right and left hemisphere, respectively. Weighted kappa was .65 and .57 for the estimation of the hypodense tissue volume in the right and left hemisphere, respectively. Agreement with the reference source ranged from 73% to 93% for all variables and both hemispheres. CONCLUSION: Even with no clinical information, neuroradiologists can assess subtle CT signs of cerebral infarction within the first 6 hours of symptom onset with moderate to substantial interobserver agreement.

Brain Edema↗
PubMed1995

[Factitious disease caused by secret administration of the oral anticoagulant phenprocoumon: study of 16 personal cases].

BACKGROUND: It is frequently difficult to disclose covert ingestion of cumarins being the underlying cause of a bleeding disorder. PATIENTS AND METHODS: We report on 16 cases (15 patients) of phenprocoumon (Marcumar) abuse. All patients (9 females, 6 males) were admitted to the hospital because of bleeding and/or prolonged thromboplastin times. Analysis of phenprocoumon in the blood was performed by HPLC. RESULTS AND CONCLUSIONS: The clinical presentation of the bleeding was highly variable. Thromboplastin times ranged from < 5 to 58%. With the exception of two patients with hepatic dysfunctions factor V activity was normal. All but one patient denied the ingestion of Marcumar. One patient died from hemorrhage. Two types of patients emerge from our series: Type I is the young nurse (8 cases), type II the usually male patient formerly treated with phenprocoumon (5 cases). Type I patients had long medical histories and showed autoaggressive behavior including the artificial manipulation of disorders other than hemorrhage. Thromboplastin times however were within or close to the therapeutic range (10 to 25%). Type II patients did not simulate other diseases in addition to hemorrhage. Thromboplastin times were longer than in type I patients. In all instances discrimination between non suicidal and suicidal behaviour was difficult. Psychiatric consultance is indicated.

Administration, Oral↗
PubMed1995

Fixation instability and oculomotor abnormalities in Friedreich's ataxia.

Eye movements were studied in 13 patients with Friedreich's ataxia and correlated with MRI findings to investigate whether oculomotor abnormalities can be traced to cerebellar disturbances in this disease. One of the most prominent eye signs was fixation instability (square-wave jerks, SWJ.). Besides SWJ the patients showed various combinations of cerebellar, vestibular and brain-stem oculomotor signs. Our patients did not comprise a homogeneous group with regard to their oculomotor findings. There was no correlation between the severity of any of the so-called cerebellar oculomotor disturbances and the number of SWJ. We tried to correlate the extent of oculomotor disturbances with floccular atrophy and atrophy of the dorsal vermis on MRI in seven of the patients. None of the oculomotor features (including SWJ) correlated with flocculus or dorsal vermis size. Furthermore, floccular and vermal measurements on MRI were normal. Accordingly, we think it unlikely that the oculomotor disturbances, including SWJ, are attributable to cerebellar pathology per se.

Adult↗
PubMed1995

Tracking of cerebral vessels in MR angiography after highpass filtering.

Maximum intensity projection (MIP), the commonly used technique for calculating MR-angiograms from three-dimensional (3D) datasets, often fails to visualize small vessels due to superposition of background signal. An improved vascular depiction can be reached by application of a connectivity algorithm, but a very good delimitation of vessel signals from signals of stationary tissue is required for this technique. Results of intracranial vessel tracking could be improved by a 3D interpolation and a preceding highpass filtering of the 3D image dataset.

Cerebral Arteries↗
PubMed1995

Bilateral spastic cerebral palsy--MRI pathology and origin. Analysis from a representative series of 56 cases.

MRI of the brain was performed on 56 children with bilateral spastic cerebral palsy (CP) at a mean age of 10.7 years. Specific pathology was found in 91 per cent; periventricular leukomalacia was present in 42 per cent of term- and 87 per cent of preterm-born children. Parasagittal subcorticocortical injury, multicystic encephalomalacia and basal ganglia lesions were identified in 16 per cent, in all but one associated with severe peri-/neonatal events at term or near term. Maldevelopment comprised 9 per cent, all but one found in term-born children. MRI morphology correlated strikingly with outcome. Periventricular leukomalacia was associated with more severe disability in term- than preterm-born children.

Adolescent↗
PubMed1995

Scotoma perception in white-noise-field campimetry and postchiasmal visual pathway lesions.

The authors examined 59 patients (32 women and 27 men) suffering from homonymous hemianopia by white-noise-field campimetry (Tübingen Electronic Campimeter) and by conventional perimetry (Tübingen Automatic Perimeter or Tübingen Manual Perimeter) and by computerized tomography (CT) or magnetic resonance imaging (MR). In all, 56 patients showed neuroradiologically detectable cerebral lesions, which were superimposed in a reconstructed "reference brain". Of these 56 patients, 18 were not capable of perceiving any white-noise-field scotoma, although their conventional perimetric findings showed defects. Lesions of these patients were concentrated along the optic radiation and spared the primary visual cortex. The lesions of the remaining 38 patients with scotoma detectable in both methods were accumulated in area V1, the primary visual cortex. The lesions of 6 patients, who had had persistent scotoma perception for more than 2 years, were situated at the occipital pole. The lesions of 8 patients with vanishing scotoma were concentrated in more rostral areas.

Adolescent↗
PubMed1994

The effects of linearly increasing flip angles on 3D inflow MR angiography.

As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP sequence. The effects on the signal distribution in the resulting angiograms of the lower limbs revealed a considerable reduction of saturation losses in agreement with the calculations. Calculated optimal ramp slopes are provided for flow velocities ranging from 5 to 50 cm/s and excitation volumes ranging from 5 to 25 cm.

Algorithms↗
PubMed1994

The "dural tail" adjacent to meningiomas studied by dynamic contrast-enhanced MRI: a comparison with histopathology.

We examined 32 patients with intracranial tumors (17 meningiomas, 8 neuromas, 7 pituitary adenomas) by conventional and dynamic contrast-enhanced MRI. Our aim was to clarify whether the pathological dural contrast enhancement adjacent to meningiomas (the "dural tail") is specific to meningiomas and, more important, whether it represents neoplastic dural infiltration or hypervascularization as a tumor accompanying reaction. A "dural tail" was found in 9 of 17 meningiomas. None of the other extra-axial tumours (neuromas, pituitary adenomas) showed comparable dural enhancement. Dynamic examinations with an ultrafast single slice imaging technique (snapshot-FLASH) after a bolus injection of contrast medium showed a "dural tail" in seven out of these nine meningiomas, while in two cases the "dural tail" turned out to be a cortical vein with a characteristic dynamic contrast enhancement pattern. In the dynamic study all seven "dural tails" were found to have earlier, steeper contrast enhancement than the corresponding tumours. All the tumours and part of the adjacent dura mater in four of the seven meningiomas with dural enhancement were examined histopathologically. In none of these four cases was neoplastic tissue found more than 2 mm away from the main tumour. The results strongly support the suggestion that the "dural tail" adjacent to meningiomas represents a hypervascular, non-neoplastic dural reaction.

Adenoma↗
PubMed1994

Multiple system atrophy: natural history, MRI morphology, and dopamine receptor imaging with 123IBZM-SPECT.

Sixteen patients with a clinical diagnosis of probable multiple system atrophy (MSA) were examined clinically by MRI and by 123I-iodobenzamide single photon emission computed tomography (IBZM-SPECT). The clinical records of another 16 patients were also analysed retrospectively. On the basis of their clinical presentation, patients were subdivided into those with prominent parkinsonism (MSA-P, n = 11) and those with prominent cerebellar ataxia (MSA-C, n = 21). Autonomic symptoms were present in all patients and preceded the onset of motor symptoms in 63% of patients. Calculated median lifetime and the median time to become wheelchair bound after onset of disease were significantly shorter for MSA-P than for MSA-C (lifetime: 4.0 v 9.1 years; wheelchair: 3.1 vs 5.0 years) suggesting a better prognosis for cerebellar patients. A significant loss of striatal dopamine receptors (below 2 SD threshold) was detected by IBZM-SPECT in 63% of the patients (56% below 2.5 SD threshold). There was no difference between patients with MSA-C and those with MSA-P in the proportion with significant receptor loss and the extent of dopamine receptor loss. Planimetric MRI evaluation showed cerebellar and brainstem atrophy in both groups. Atrophy was more pronounced in patients with MSA-C than in those with MSA-P. Pontocerebellar hyperintensities and putaminal hypointensities on T2 weighted MRI were found in both groups. Pontocerebellar signal abnormalities were more pronounced in MSA-C than in MSA-P, whereas the rating scores for area but not for intensity of putaminal abnormalities were higher in MSA-P. MRI and IBZM-SPECT provide in vivo evidence for combined basal ganglia and pontocerebellar involvement in almost all patients in this series.

Adult↗
PubMed1993

Late-onset Friedreich's ataxia. Molecular genetics, clinical neurophysiology, and magnetic resonance imaging.

OBJECTIVE--To clarify the nosological classification of late-onset Friedreich's ataxia (LOFA), ie, patients who have later onset of Friedreich's ataxia (FRDA), often after 25 years of age. DESIGN--Comparison of clinical examination data, nerve conduction studies, electronystagmographic recording, and magnetic resonance imaging of a family with LOFA with a group of patients with FRDA. Genetic linkage analysis was performed in the family with LOFA. SETTING--Referral center. PATIENTS--Thirteen patients satisfied classic diagnostic criteria of FRDA, and three patients from one family satisfied all diagnostic criteria of FRDA but with disease onset after 25 years. RESULTS--Results of nerve conduction studies, electronystagmographic recording, and magnetic resonance imaging in patients with LOFA closely corresponded to observations made in patients with FRDA. In addition, genetic linkage analysis using markers tightly linked to the FRDA locus on chromosome 9 showed that all affected members of the LOFA family, but not their unaffected siblings, had inherited identical paternal and maternal genotypes. CONCLUSIONS--Data suggest that LOFA may also result from mutation within the FRDA locus.

Adolescent↗
PubMed1993

Cortical DC-potentials in identification of the language-dominant hemisphere: linguistical and clinical aspects.

In order to find a non-invasive method for determining the hemispheric dominance for language, we studied cortical activation patterns during language processing by means of electrophysiological techniques: DC-potentials were recorded from frontal, central, temporal and parietal electrode positions in 28 right-handed normal subjects and in 16 patients with a history of transient loss of speech and known hemispheric dominance. Subjects were asked to find as many synonyms as possible within 6 seconds to either a concrete or an abstract noun. This task caused a highly significant left-hemispheric lateralization over frontal and central, but not over temporal and parietal cortical areas. Search for synonyms to abstract nouns yielded frontal left-hemispheric dominance in 93% of all normal subjects, search for synonyms to concrete nouns in 85%. Inter-electrode correlation coefficients were higher during processing of abstract word categories than during processing of concrete categories. In all patients, frontal and central lateralization corresponded to their hemispheric dominance as determined from clinical data. Advantages as well as inconveniences of this technique are discussed and compared to other invasive and noninvasive tools of assessing speech lateralization.

Adolescent↗
PubMed1993

Cerebellar encephalitis in adults.

We examined 11 adult patients with cerebellar encephalitis (CE) during the acute phase of the disease and at least 12 months later. Five patients were aged between 23 and 31 years, 3 patients between 43 and 44 years and 3 patients between 60 and 64 years. Serological tests gave evidence of Epstein-Barr virus infection in 4 of the 5 young patients. Two patients had serological evidence of varicella-zoster virus reactivation, whereas the serological findings were negative in all other cases. All patients in the younger and middle age groups recovered within 3-30 weeks after onset of CE. If at all, they had only minor cerebellar deficits at the follow-up examination. Magnetic resonance imaging (MRI) examination performed at the follow-up examination was normal in all of them. In contrast, 2 of 3 patients older than 60 years had persistent cerebellar ataxia following CE. In these patients, MRI revealed infratentorial atrophy. Our data show that the clinical spectrum of CE in adults is wider than assumed so far. In addition to typical cases of CE in young male patients with good recovery, CE may also occur in older patients and give rise to persistent cerebellar ataxia.

Adult↗