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Biomedical subjects

O Köster

Publications and source records attributed to O Köster.

At least 19 recordsLinked to original sources
PubMed2002

[Lumbar intraspinal juxtafacet cysts: MR imaging and CT-arthrography].

PURPOSE: To present data on the MR imaging appearance of lumbar intraspinal juxtafacet cysts (JFC) and to assess the importance of additional CT arthrography. MATERIAL AND METHODS: Twenty-eight patients (16 women, 12 men) with a mean age of 64 years (range: 43 - 82), who underwent MR imaging because of radicular pain or spinal claudication, were found to have an intraspinal cyst associated with the facet joint. In 14 patients, additional CT-arthrography was performed to determine whether a communication exists between the cyst and the facet joint and to try to rupture the cyst. RESULTS: In T(2)-weighted images, juxtafacet cysts show a typical pattern consisting of a hyperintense center and hypointense rim. The center is likely to be inhomogeneous because of recurrent hemorrhage in the cyst. In T1-weighted images, the cysts are hypo/isointense. Irregular hyperintensity may indicate subacute hemorrhage, which may aggravate the clinical symptoms. MR allows superior visualization of the cyst in all anatomical planes. It also enables assessment of typical accompanying changes, such as degenerative spondylolisthesis and facet hypertrophy. All patients, who had CT-arthrography, were found to have a direct communication between joint space and cyst. Transarticular rupture of the cyst was possible in five patients. Two of these five patients had good to excellent improvement, and the remaining three patients underwent surgery. CONCLUSION: MR imaging is the method of choice for diagnosing lumbar intraspinal juxtafacet cysts. CT-arthrography of the facet joint is helpful in cases with difficult differential diagnosis, and in the preoperative planning. Furthermore, it assists in the primary interventional treatment.

Adult↗
PubMed2000

Macroangiopathy of the upper extremities in progressive systemic sclerosis.

BACKGROUND: Raynaud's phenomenon is a hallmark of progressive systemic sclerosis (SSc). While nailfold capillary changes are well known, morphological changes in larger arteries have less been focused on. OBJECTIVE AND METHODS: In the study presented we examined how often in digital subtraction angiography organic changes of the arteries of the fingers, hands and forearms were observed, whether they showed a typical picture like the changes in nailfold capillaries and whether they correlated with cutaneous sclerosis, Raynaud's phenomenon and serological findings. 29 patients were examined, 14 with acroscleroderma and 15 with proximal ascending sclerosis. RESULTS: In 27 of those 29 patients a stenosis of the arteries of the upper extremity was found. The frequency of arterial occlusions decreased from the fingers (26 patients) to the forearms (9 patients with occlusion of the ulnar artery, none with occlusion of the radial artery). The arteries of 47% of patients with proximal ascending sclerosis showed no reactivity towards the alpha-sympatholyticum tolazoline hydrochloride due to severe organic changes while in patients with acroscleroderma only 14% of patients did not respond to tolazoline hydrochloride. The severity of Raynaud's phenomenon did not correlate with the severity of the angiographic findings. In patients with stenoses refractory to tolazoline hydrochloride and in those with occlusions Scl-70 autoantibodies were more frequently positive than in other patients with SSc (44% compared to 23%). CONCLUSION: As in SSc the severity of the organic arterial changes is in close correlation with the extent of the cutaneous sclerosis and with the serological findings the arterial system should gain much more importance in the diagnosis and therapy of SSc.

Aged↗
PubMed1999

NH4+ utilization and regeneration rates in freshwater lakes determined by GC-MS of derivatised dihydroindophenol.

A new gas chromatographic-mass spectrometric method was established that is applicable for the determination of NH4+ utilization and regeneration rates in freshwater. Hollow-fibre modules were used to stop the biogenic nitrogen-fluxes by separating the particulate from the dissolved matter. Incubations were performed in Tedlar bags (polyvinylfluoride), which enabled repeated sample removals through Teflon tubes, making the calculation of nitrogen-fluxes in accordance to Blackburn and Caperon much more reliable. The Berthelot reaction was performed with ammonium and a fragment ion (base peak) of tris-(trifluoroacetyl) 4,4'-dihydroxydiphenylamine was used to determine the at% excess 15N by gas chromatography-mass spectrometry. Nitrogen-flux measurements were made in the epilimnion of the deep, stratified, mesotrophic Lake Zürich, in which the cyanobacterium Planktothrix rubescens was the dominating photoautotrophic micro-organism. The size fraction <20 microm that consisted of heterotrophic bacterioplankton and nanoflagellates, and photoautotrophic pico- and nanoplankton accounted only for a minor part of the ammonium utilization (<25%) and regeneration (< or =25%) rates, whereas the size fraction >20 microm which primarily consisted of Planktothrix rubescens was responsible for the major part. In the eutrophic Lake Au, which is connected to Lake Zürich through a canal, utilization and regeneration rates as high as 700 and 482 nM h(-1) were measured.

Animals↗
PubMed1999

Qualitative and quantitative analysis of voice onset by means of a multidimensional voice analysis system (MVAS) using high-speed imaging.

High-speed filming is one of the most informative methods for assessing voice physiology data. Tracing high-speed images of the glottis provides quantitative parameters such as the glottal area and the glottal width function. By way of example, a number of studies are discussed which extract quantitative data from high-speed images showing voice onsets. Furthermore, a new computer system (MVAS; multi-dimensional voice analysis system) is presented that synchronously displays a laryngoscopic high-speed film, the electroglottographical signal, and several acoustic analyses of the recorded voice sample. The automatic measurement of glottal width and glottal area from the laryngoscopic images is also provided. Looking at former studies and our analyses of voice onsets reveals a tremendous intersubject and even intrasubject variability (different prephonatory closure, different time span until full amplitude is reached, different open quotient).

Equipment Design↗
PubMed1999

Contrast-enhanced transcranial color-coded sonography in acute hemispheric brain infarction.

PURPOSE: The aim of the present study was to investigate the diagnostic potential of contrast-enhanced transcranial color-coded real-time sonography (CE-TCCS) in otherwise ultrasound-refractory acute stroke patients with an ischemia in the territory of the middle cerebral artery (MCA). Furthermore, correlations of CE-TCCS findings with clinical, angiographic, and CT results were investigated. METHODS: In 90 acute stroke patients with inadequate insonation conditions in unenhanced transcranial color-coded real-time sonography (TCCS) examinations, CE-TCCS, clinical, angiographic, and CT examinations were performed within 12 hours, 36 hours (CE-TCCS only), and 1 week after onset of clinical symptoms. A CT angiography (CTA) as reference method was available in 39 individuals. After application of a galactose-based echo-enhancing agent, the portion of conclusive ultrasound examinations of the MCA, as manifested by an MCA occlusion, decreased or increased flow velocity (FV), and symmetrical MCA FV, was evaluated. CE-TCCS findings on admission and during follow-up were correlated with infarction size as demonstrated on follow-up CT, and clinical findings were assessed by use of the European Stroke Scale. RESULTS: Adequate diagnosis was achieved in 74 of 90 patients (82%) by the use of echo contrast agents. MCA occlusion or reduction of MCA FV was found in 20 and 27 patients, respectively. MCA occlusion was confirmed by CTA in 17 cases. In one individual, false-positive diagnosis of MCA occlusion was made according to ultrasound criteria. In 5 patients with MCA occlusion, vessel recanalization was observed during follow-up; 15 of 27 patients with decreased flow velocities showed normalization after the third examination that was associated with a significantly better clinical outcome (P<0.0001). Furthermore, MCA occlusion or decreased FV in the first 12 hours were associated with significantly larger infarctions in the MCA territory compared with normal CE-TCCS findings (P<0.0001). CONCLUSIONS: CE-TCCS enables adequate diagnosis in approximately 80% of acute hemispheric stroke patients with insufficient unenhanced TCCS examinations. It is a reliable diagnostic tool regarding MCA mainstem and branch occlusions. Because this method conveys useful information concerning cerebral tissue and clinical prognosis, it may be useful to identify those patients who benefit most from local or intra-arterial thrombolytic therapy.

Acute Disease↗
PubMed1998

Diagnosis and monitoring of middle cerebral artery occlusion with contrast-enhanced transcranial color-coded real-time sonography in patients with inadequate acoustic bone windows.

Transcranial color-coded real-time sonography (TCCS) is an emerging diagnostic technique that allows noninvasive imaging of intracranial vessels within parenchymal structures. However, in some patients, transcranial ultrasound is particularly hindered by insufficient ultrasound penetration through the temporal bone. The present study evaluates whether or not application of an echo-contrast agent in ultrasound-refractory patients with middle cerebral artery (MCA) trunk occlusion enhances image acquisition enough to yield accurate diagnoses. Contrast-enhanced (CE) TCCS examinations, computed tomography scans and angiographic studies were performed in 20 patients with clinical symptoms suggestive of MCA occlusion within 12 h of the onset of symptoms. For comparison, 20 control persons without history or clinical signs for cerebrovascular diseases were examined using CE-TCCS. In none of the patients or control subjects did unenhanced TCCS investigations depict any color-coded vascular signal of an intracranial vessel. After application of 9 mL of 400 mg/mL galactose-based microbubbles, CE-TCCS was performed. In subjects with MCA occlusion, CE-TCCS examinations were repeated within 24 h, 48 h and 5 days after stroke. In stroke patients (n = 20), CE-TCCS showed an occluded MCA main stem in 11 patients, and this vessel was clearly demonstrable on the unaffected side. On the affected side, the posterior cerebral artery (PCA) and anterior cerebral artery (ACA) could be visualized in 8 of 11 subjects; in 3 patients, at least 1 of these vessels was detectable. Angiographic studies confirmed the diagnosis of MCA trunk occlusion in all 11 individuals. In follow-up investigations, 3 stroke patients had angiographic and CE-TCCS examinations consistent with vessel reperfusion. Nine stroke patients had a patent MCA shown in angiographic and CE-TCCS examinations. In the control group, the MCA trunk could be visualized in all subjects by CE-TCCS. CE-TCCS is a sensitive and specific ultrasound method for the diagnosis of MCA trunk occlusion that overcomes the anatomical hindrance of inadequate acoustic bone window. This technique may help to identify patients suitable for thrombolytic therapies and monitor their response.

Aged↗
PubMed1997

Early CCT signs of supratentorial brain infarction: clinico-radiological correlations.

Early signs of brain infarction can be detected by modern CCT technology even within the first 6 h after stroke. Little is known about the prognostic significance of early infarction signs in CCT. We prospectively evaluated clinical and CCT findings of 95 consecutive patients with an acute ischemia in the territory of the middle cerebral artery. All patients were admitted to our stroke unit within 6 h after stroke. In 55 patients CCT was performed within 3 h, and in 40 cases between 3 and 6 h. In all patients the clinical findings were assessed by the Scandinavian Stroke Scale (SSS). The disability due to stroke was evaluated after 4 weeks by use of the modified Rankin Scale. We could demonstrate the following early signs of cerebral infarction: focal hypodensity (23.2%), obscuration of basal ganglia (12.6%), focal brain swelling (22.1%), hyperdense middle cerebral artery sign (HMCA; 11.5%). In 3 patients early edema led to ventricular compression, in 1 patient to midline shift. The occurrence of early infarction signs did not depend on the etiology of ischemia but was significantly associated with a severe neurological deficit at admission and an unfavourable disability status 4 weeks after stroke. Focal brain swelling and HMCA were often followed by extensive infarction lesions on the follow-up CCT. In conclusion, early signs of hemispheric brain infarction visible on CCT scans performed within 6 h after stroke are correlated with severe stroke and an unfavourable functional outcome. However, a substantial part of our patients had a benign course of the disease in spite of early CCT pathology. Decisions on therapy in individual patients therefore should not depend on early CCT findings exclusively.

Acute Disease↗
PubMed1996

[Endoscopic imaging of vocal cord vibrations. Digital high speed recording with various systems].

Vocal fold vibration patterns during phonation are presented with different digital imaging systems. With newly developed technical equipment color images up to 1000 digital images/s were obtained without light intensifying enhancement techniques via rigid and flexible endoscopy. With this color high-speed system, morphologic structures, such as small blood vessels, were visualized in high-resolution quality as a result of additional color information. In another system, zooming of endoscopic pictures via pixel interpolation algorithms provided full-monitor presentation of vocal fold vibratory patterns. This system allows PC-based synchronization with microphone and electroglottographic signals in a frame-by-frame technique. Although only processing gray scale images, analyses of dynamic changes in modes of vibration were facilitated by the higher frame rate recording of up to 2000 frames/s and, in addition, they display corresponding analog signals. Both methods provide clinically important information. Furthermore, we demonstrated irregular vocal fold vibration patterns in a healthy adult volunteer. In this experiment, the irregular vibratory modes were induced by voluntarily applying asymmetric vocal fold tension. The asymmetric vocal fold vibration pattern resulted in (functionally induced) roughness of the voice as predicted by computer models of asymmetric vocal fold vibration. Digital high-speed cinematography proved to be a highly promising technique in the analysis of dysphonia and provided physiological examples that could be compared with models of coupled nonlinear oscillators.

Adult↗
PubMed1994

[The effect of a low-dose hydrochlorothiazide therapy on the bone mineral content of the axial and peripheral skeleton].

An increase in bone mineral content (BMC) as well as a decrease in the incidence of fracture of the proximal femur have been described in patients on thiazide diuretic treatment. A study was undertaken to assess, by means of dual X-ray absorptiometry, the effect of chronic low-dosage antihypertensive treatment with hydrochlorothiazide (HCT; < or = 25 mg daily) on lumbar vertebrae (representing the axial skeleton) and the nondominant radius (peripheral skeleton). Measurements were made on 27 women (mean age 63.8 +/- 8.2 years) and 23 men (65.9 +/- 9.5 years) and compared with a control group of 19 women (62 +/- 8.7 years) and 20 men (65.9 +/- 9.5 years) with minor surgical or dermatological lesions who had never taken HCT or other drugs with potential effects on mineral bone metabolism. In men who had been on HCT for more than 5 years, BMC of the lumbar vertebrae was higher by 10.3% and of the radius by 3.8% than among the controls (differences not significant). In women who had been on HCT for more than 5 years, the corresponding increases were 19.6% (P < 0.05) and 5.4% (not significant). Among those patients who had been on HCT for less than 5 years there were no significant differences compared with the control group. There were no significant differences between the groups relating as regards the proximal radius which, in contrast to the ultradistal radius, consists predominantly of cortical bone. -These data indicate that, while HCT has only a slight influence on BMC, it can be considered to have a desirable associated effect in the antihypertensive treatment of elderly patients.

Absorptiometry, Photon↗
PubMed1994

Interobserver variation in the detection of osteopenia by radiography and comparison with dual X-ray absorptiometry of the lumbar spine.

In 100 patients (20 male, 80 female) radiographs of the lumbar spine were obtained in both planes, anteroposterior and lateral. Nine readers independently and without specific criteria or training assessed the radiographs for presence of osteopenia in the form of a binary decision. A posteranterior dual x-ray absorptiometry (PA DXA) measurement of the lumbar spine was performed in all patients using the Hologic QDR 1000 bone densitometer. A bone mineral density (BMD) of 0.83 g/cm2 (T-score about 2 SD and 2.5 SD lower than BMD in normal young female and male subjects respectively) was used as a threshold for the diagnosis of osteopenia. Complete agreement amongst the 9 readers was achieved in 43 patients. In 26 more patients at least 8 readers agreed. kappa-coefficients for interobserver variation ranged from 0.458 to 0.691 for reader pairs. For agreement between the observer ratings and the DXA results, kappa-coefficients ranging between 0.347 and 0.555 were found. The vast majority of readers agreed in the diagnosis of osteopenia in cases where the BMD was less than 0.73 g/cm2. Where the BMD was between 0.73 and 1.03 g/cm2 a substantial disagreement was found between reader evaluation and DXA measurement, and also amongst the readers. We conclude from our results that osteopenia can reliably be detected from lumbar spine radiographs by all readers only after a substantial amount of BMD is lost. On the other hand, a diagnosis based solely on PA DXA measurement of the spine may also lack accuracy, due to a substantial influence of degenerative changes of the lumbar spine and aortic calcification.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1994

[High resolution computerized tomography of the temporal bone in mandibulofacial dysostosis].

High resolution CT (HR-CT) scanning of the temporal bone was performed in three patients with a fully expressed mandibulofacial dysostosis for preoperative assessment of temporal bone abnormalities. The external auditory canal was absent in five of six ears. Scans revealed a dysplastic middle ear cleft with dysplastic and partly dislocated ossicles. The ossicles were absent in two temporal bones. In no patient was the mastoid bone pneumatised. The inner ear was affected in only one patient in whom a shortening of the lateral semicircular canal could be found bilaterally. The role of HR-CT of the temporal bone as a preoperative diagnostic tool for the assessment of abnormalities of surgical import is discussed.

Adult↗
PubMed1993

[Ultrasound procedure in the diagnosis of osteoporosis].

Ultrasound transmission velocity and ultrasound attenuation of the appendicular skeleton are influenced by bone density and by bone structure and correlated to mechanical properties of bone. This article reviews basic principles of these techniques and their experimental and clinical applications. Results of the ultrasound techniques and their relation to established radiological measurements for the assessment of bone mineral density in vivo and in vitro are reported. Factors with an influence on both ultrasound transmission velocity and ultrasound attenuation are discussed. Ultrasonic measurements of the bone may offer a simple, non-invasive and radiation-free assessment of bone quality in osteoporosis and other metabolic diseases affecting the bone. However, further studies are required to confirm this.

Aged↗
PubMed1993

[Ultrasound velocity measurement in the diagnosis of postmenopausal osteoporosis].

We evaluated ultrasound transmission velocity as an indicator for osteoporosis at the os calcis of both feet and at the proximal phalanges of DII and DIII of both hands in 74 female subjects (22 premenopausal, 29 postmenopausal non-osteoporotic and 23 postmenopausal osteoporotic). In addition dual x-ray absorptiometry (DXA) of the lumbar spine was performed in 30 women and a combined cortical thickness index (CCT-index) of os metacarpale II was calculated from hand radiographs in 29 women. Ultrasound velocity at all sites slightly decreased in premenopausal women with age and declined significantly after menopause. At the hand postmenopausal osteoporotic women had significantly lower velocities than normal postmenopausal or premenopausal women while no difference could be seen at os calcis. An only poor or moderate correlation between ultrasound velocity at all sites and DXA of the lumbar spine and a good correlation between the CCT-index and velocity at the fingers indicate that ultrasound velocity is not only affected by bone density but even more by structural properties.

Absorptiometry, Photon↗
PubMed1992

[The radiation loading of the crystalline lens and thyroid during high-resolution computed tomography of the teeth].

The radiation dose to the ocular lens and thyroid gland during high resolution CT of the jaw was measured in a head phantom and in 9 patients. The dose for the lens and thyroid gland resulting from 10 cuts was 0.7 and 0.9 mGy, respectively. By shielding the thyroid gland against scatter a reduction of 20% is possible. Radiation exposure is considerably higher than during conventional dental x-ray examinations. Compared with CT examinations of the head and neck region, radiation exposure of both organs is about the same.

Humans↗
PubMed1992

[Ultrasonic velocity measurements at weight-bearing and non-weight-bearing sites of the peripheral skeleton. The effect of physical activity in soccer players].

Ultrasound transmission velocity at the appendicular skeleton is determined by elastic properties of the bone as mass density. We evaluated ultrasound transmission velocity at the os calcis of both feet and at the proximal phalanges of DII and DIII of both hands in 51 male subjects. 28 of them were professional soccer players of the 1st German division, 11 subjects performed non-professional exercise in various athletic organisations regularly and 12 did not exercise at all. A significant difference in the speed of sound could be seen at os calcis, where the soccer players had higher velocities than the other groups. The differences between the groups at the upper and lower extremities suggest that changes in ultrasound transmission velocity are not only affected by structural changes in the aging skeleton, as it might be suggested by age differences, but by exercise. Physical exercise can change the properties (structure and/or density) of weightbearing bone and this can be detected by measuring ultrasound velocity.

Adolescent↗
PubMed1992

The application of computerized tomography (CT) in cases of impacted maxillary canines.

A comparison is made between conventional X-rays and computerized tomography (CT) based on eight patients with thirteen impacted upper permanent canines. The use of CT yields information which is much more detailed than that observed on conventional X-rays, such as: pathological resorption on adjacent teeth caused by aberrant canines; the localization of the injury and the position of the canine in relation to one or both incisors. The amount of radiation per exposure is still rather high for the CT (Köster and Ewen, 1986). Further research is necessary in order to reduce this exposure and to determine the appropriate and most effective use of CT in the dental field.

Adolescent↗
PubMed1992

[Radiologic diagnosis of osteoporosis. Current methods and outlook].

Osteoporosis is defined as a decrease in bone mass and structural changes in bone leading to an increase in fractures. Early diagnosis as quantification of prophylaxis and treatment are of great interest. A number of non-invasive techniques are available for measuring bone mass at multiple sites of the skeleton. This article reviews basic methodology and developments in radiography as in x-ray or gamma photon absorptiometry, quantitative computed tomography, ultrasound velocity and attenuation and magnetic resonance imaging. Clinical applications of these methods are discussed. The still experimental use of ultrasound and MRI in assessment of bone-mineral content may also give information on bone quality.

Absorptiometry, Photon↗